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Screening Experiments for Butyl Acrylate/Vinyl Acetate Pressure-Sensitive Adhesives
Abstract
Emulsion-based pressure-sensitive adhesives (PSAs) are gaining in importance due to their improved performance as well as the lower environmental impact of the emulsion polymerization process. In this study, the influence of eight emulsion polymerization variables on the final PSA properties of butyl acrylate/vinyl acetate (BA/VAc) emulsion-based PSAs was investigated (i.e., BA/VAc ratio, acrylic acid content, type and concentration of stabilizer, concentration of initiator, concentration of CTA, temperature, solids content). Final performance properties such as peel strength, shear strength, and tack were investigated on two different substrates: stainless steel and high-density polyethylene. A wide range of properties was generated ranging from very good to poor PSA performance. The screening design fulfilled its purpose in that it was used to generate a wide range of final properties. The results obtained here will be used in the decision-making process for further experimentation. However, for several reasons, the development of empirical models to relate the process conditions to the final product properties was not possible. In all three adhesive tests, the performance of the investigated adhesives was superior on the stainless steel substrate compared to high-density polyethylene. Most of the adhesives showed relatively high loop tack coupled with either adhesive or cohesive failure on both substrates. In most cases, peel strength was higher on stainless steel. A broad range of shear strength responses was observed: extremely high, on the order of several weeks, to zero shear strength. The chain transfer agent, which regulated the gel content of the emulsion latexes and the molecular weight of the soluble polymer fraction as well as the monomer feed composition, was suspected to be among the most influential factors affecting the final PSA performance. In addition, it was possible to obtain balanced final properties using either sodium dodecyl sulfate or poly(vinyl alcohol) as surfactant but at different concentrations.
... To introduce crosslinking structures to the emulsion is well studied in pressure sensitive adhesives (PSAs) and coatings. [9][10][11][12][13][14][15][16][17][18][19] Recently, Mishra et al. synthesized LAs using glycidyl methacrylate (GMA), methyl methacrylate (MMA), and butyl acrylate (BA) as comonomers. 20 They reported that the polymer chains had epoxy groups and the adhesive properties could be improved by crosslinking reaction of functional groups after laminating. ...
... Generally, the coagulation is affected by surfactant content, solid content, AA content, polymerization temperature, stirring speed, initiator content, and polymerization technique. 16 Therefore, the factors were optimized through a series of experiments to obtain very little coagulation (about 0.12 wt %) and stable latices for the following investigations. The recipes in this study were completed successfully with monomer conversions exceeding 99 wt %. ...
... It has been known that the molecular weight and gel content are the significant factors affecting the performance of PSAs, wherein increasing molecular weight and gel content will increase the bonding strength of adhesives but decrease tack. 16 These principles are applicable for LAs. ...
The concept of using particle structure design to prepare emulsion laminating adhesives (LAs) for improving both the peel strength and heat resistance properties has been investigated. The homogeneous particle latices based on vinyl acetate/acrylate copolymer (samples 1–3) were synthesized by seeded semicontinuous emulsion polymerization with different chain transfer agent (CTA) contents but with no functional monomers, while the core-shell structure crosslinkable latices (samples 4 and 5) were prepared through multistage polymerization technique. The emulsion particle structure was investigated by TEM and particle size analyzer. The results indicate that the average emulsion particle diameter is about 130 nm and the particles grow without secondary nucleation. Samples 1 and 2 prepared with 0.7 and 0.5 phm (per hundred gram monomer) CTA respectively, show high peel strength but poor heat resistance property. On the contrary, the sample 3 prepared with 0.1-phm CTA exhibits low peel strength but relatively good heat resistance. However, sample 4, which was synthesized with 0.5-phm CTA and 0.4-phm acetoacetoxy ethyl methacrylate (AAEM) in core but 0.5-phm CTA and 0.6-phm AAEM in shell stages, shows high peel strength (1032.9 g/in.) and good heat resistance property (524.9 g/in.). In addition, sample 5 also demonstrates high peel strength (987.2 g/in.) and good heat resistance property (643.5 g/in.) when it was synthesized using 0.1-phm CTA but no AAEM in core, 0.36-phm CTA and 0.75-phm AAEM in shell stages. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
... The in situ incorporation of up to 1 phm CNC (phm: parts per hundred parts monomer by mass) in emulsion polymerization of poly(n-butyl acrylate-methyl methacrylate) (BA/MMA) resulted in significant and simultaneous improvement of all three PSA characteristics (Dastjerdi et al. 2018). This groundbreaking finding solves a long-time conundrum in PSA property modification, which originates from a polymer's viscoelastic behaviour, and the fact that microstructural modification usually only improves one aspect of such behaviour at a time (Jovanović and Dubé 2005;González et al. 2006;Ren and Dubé 2017). In situ addition of CNCs elevated the hydrophilicity of the PSAs and therefore, their work of adhesion, which resulted in better tack and to some degree peel strength. ...
... The selection of our monomer system was based on a rule of thumb for PSA formulations which implies copolymerization of ''soft'', ''hard'', and ''polar'' monomers. BA, VAc, and AA were selected, respectively, and their levels were adjusted according to a previous study (Jovanović and Dubé 2005). We replaced MMA with VAc as the ''hard'' monomer, because of the higher hydrophilicity of VAc, which improves the polymer-CNC compatibility, and therefore, can assist in achieving a good dispersion of the CNCs in the final PSA films (Dastjerdi et al. 2018;Ouzas et al. 2018a). ...
Cellulose nanocrystals (CNCs) are naturally-sourced nanoparticles that can be used to modify polymers and provide exceptional mechanical properties to nanocomposite materials. In this study, CNCs were incorporated into water-based pressure sensitive adhesives (PSAs) via in situ semi-batch emulsion polymerization to improve PSA properties. A sequential design approach was used to improve CNC/poly(n-butyl acrylate/vinyl acetate) nanocomposite PSAs. In the first part of the design, the effects of acrylic acid (AA) and anionic surfactant sodium dodecyl sulfate (SDS) were examined in the presence of 0.5 wt% CNCs (based on polymer mass). While the SDS was crucial to maintaining latex stability, its excessive addition led to a decrease in PSA performance, namely tack and peel strength. The AA comonomer was pivotal in improving the shear strength of the PSAs, especially in the presence of CNCs. In all cases, the addition of CNCs led to improved PSA shear strength. In the second part of the design, the addition of 1-dodecanethiol (NDM) as a chain transfer agent (CTA) with CNC levels up to 1 wt% led to an improvement in tack and peel strength but at the cost of diminishing the shear strength. Generally, the addition of CNCs improved PSA performance. Thus, to maximize the impact of CNCs on PSA properties, a careful balance of SDS (for latex stability), AA (to improve shear strength) and NDM (to improve tack and peel strength) are needed.
Graphic abstract
... The latter one have much higher shear strength, together with higher peel and tack properties, for the aforementioned applications considering the continuous network morphology made by physical entanglements of acrylic chains in the solvent-borne adhesives when the solvent has evaporated [32]. In comparison, the microgels in the latex particles retain their discrete morphology in the adhesive film [33]. This morphology decreases the shear strength of the latex based PSAs because of the poor interconnections between the microgels and the linear polymers in the structure of the film [34,35]. ...
... UV grades are solvent free and are processed as hot melts. The adhesive film is cross-linked with UV radiation after the acrylic film has been coated with the UV-acrylic hot melt for self-adhesive material production [28,33]. ...
Self-adhesive materials are called, in the adhesive industry, pressure-sensitive adhesives (PSAs). PSAs are designed in the shapes of latex, solvent borne resin, rubber solution, or hot melt and are being used for foils and films, tapes, labels, and notepads which can make permanent, removable, or semi-removable adhesive joints for applications of general purpose product assembly by simple contact under light pressure. This special class of adhesives does not undergo any physical transformation or chemical reaction during the bonding process. The end-use properties of PSAs result from the nonlinear viscoelastic behavior of the adhesive material, and the elastomeric polymer basis of PSAs imparts them such a viscoelastic behavior caused by a carefully chosen polymer architecture and monomer composition with the proper addition of small molecules called tackifying resins. They are safe to use and easy to handle and thus are increasingly replacing more conventional types of adhesives. In this chapter, we review adhesion mechanism of PSAs, types of PSAs, adhesion properties and tests, mechanical behavior of joints, and especially different aspects of PSA applications.
... Commercially, EPSA are prepared with soft monomers such as BA and 2-EHA as the main monomers because of their low plateau modulus and good weather ability [5][6][7]. The performance of EPSA is judged mainly on three major properties: peel, shear strength, and tack of the final product [8]. ...
... Regardless of the polymerization procedure used, the PSAs showed an increase in shear holding power as the gel content increased. In another study, a range of BA=VAc polymers were synthesized by Jovanovic and Dube in order to screen the system for application as a PSA [8]. The influence of eight polymerization variables (i.e., BA=VAc ratio, weight fraction of AA, type and weight fraction of stabilizer, weight fraction of initiator and CTA, polymerization temperature, and solids content) on final product properties of BA=VAc emulsion-based polymers was investigated. ...
In order to obtain a suitable formulation of designing direct synthesis of acrylic latexes to be used as emulsion pressure sensitive adhesives (EPSA), having high shear resistance together with high peel strength and tack, free radical emulsion polymerization of hard monomers, such as styrene (St), vinyl acetate monomer (VAM), methyl methacrylate (MMA) and butyl methacrylate (BMA), and soft monomers, butyl acrylate (BA) and 2-ethylhexyl acrylate (2-EHA) along with multifunctional monomers, namely acrylic acid (AA), were carried out. The effect of the type of hard and soft acrylic monomers, the type and level of emulsifiers, and the initiator concentration on the emulsion polymer stability and final properties of the EPSA were investigated. The results obtained showed an optimized composition. This composition led to a significant increase in shear strength and peel strength to 909 kPa and 0.45 N/mm, respectively, while the synthesized PSA was still too tacky, 5.5 cm, according to adhesion performance testing. For making this successful balance of the conflicting adhesion properties of PSA, a series of anionic and nonionic emulsifiers were investigated. It was interestingly found out that the hybrid emulsifiers (anionic coupling with nonionic) with the optimized compositions could enhance the stability of the emulsion system and improve the properties of PSA compared with the mono-emulsifier. We also tried to adjust the initiator concentration with the level of the optimized hybrid emulsifier, polyoxyethylene alkyl phenyl ether (K30), dioctyl sulfosuccinate (DOSS), and sodium vinyl sulfonate (SVS) with the ratio 2:1:1, resulting in a highly preferred proportion of the 0.5 part of the initiator versus 1.25 parts of the hybrid emulsifier in terms of the total weight of the monomers.
... The effect of surface roughness was discussed in several earlier studies [6][7][8] and in our previous work [9] we have presented a detailed investigation of the effect of surface roughness of a steel substrate on the adhesion of uncrosslinked acrylate copolymers and have shown that surface roughness strongly influences the work of adhesion as well as size and number of the cavities, however the cavity growth rate is found to be insensitive to surface roughness, but strongly controlled by viscoelastic properties of PSA. Some earlier studies [3,[10][11][12] and several recent studies [13][14][15][16][17] are related to the investigation of the effect of surface energy of the substrate (i.e. probe in the tack experiment) on the adhesion of PSAs. ...
... Good wetting of the adherent by the adhesive is also very important for high tack, which is fulfilled if the adherent has a higher surface tension than the adhesive [3]. In the recent studies [13][14][15][16][17], the influence of the composition of PSAs on their adhesive performance on the lowenergy surfaces has been studied and synthesis of PSAs with good adhesion on low-energy surfaces has been attempted. ...
a b s t r a c t The adhesion behavior of statistical, uncrosslinked butyl acrylate-methyl acrylate copolymer on different surfaces (stainless steel, polyethylene, glass and Si-wafer) has been investigated using a combination of probe tack test and simultaneous video-optical imaging. Tack and stress peak values increase and the final number of cavities as well as cavity growth rate decreases with increasing surface energy of the substrate due to better wetting. The influence of the incorporation of an additional comonomer, namely, hydroxyethyl acrylate, methyl methacrylate and acrylic acid, on the adhesion of statistical, uncrosslinked butyl acrylate-methyl acrylate copolymer has been studied. Steel probes with different average surface roughness (R a ¼ 2.9 and 291.7 nm) have been used for tack tests. The increasing polarity of the incorporated comonomer has no measurable effect on the surface tension but leads to an increase of shear modulus and consequently, to an increase in the stress peak, deformation at break, tack values, as well as the total number of cavities. The latter is a consequence of worse wetting. Cavity growth rate on the smooth surface is insensitive to copolymer composition, on the rough surface, the increase in the modulus associated with the additional monomers, leads to a decrease in the cavity growth rate. This indicates different cavity growth mechanisms: predominately lateral growth on the smooth surface and omnidirectional growth on the rough surface. The adhesion performance of uncrosslinked and crosslinked butyl acrylate-methyl acrylate copolymers is compared. The latter exhibit adhesive, and the former cohesive failure. The total number of cavities and cavity growth rate is found to be controlled by viscoelastic properties of PSA independent of the debonding mechanism and the latter decreases significantly with increasing shear modulus.
... The results showed that polymer emulsion products performed quite well compared to others. According to the literature, emulsion-based pressure-sensitive adhesives (PSAs) polymers are gaining popularity due improved performance and lower environmental impact (Czech 2003;Jovanovi c and Dub e 2005). Meng, Liang, and Liu (2017) described a successful chemical sand-fixing material made from a cationic poly(vinyl acetate acrylate-2-hydroxyethyl acrylate tri-methyl ammonium chloride) (P(Vac-BA-HEA-DMC)) copolymer emulsion. ...
Dust palliatives are commonly used when airborne dust is problematic. Dry soils are treated with a mixture of polymers, such as butyl acrylate vinyl acetate (BA–VA), emulsified in water. Eventual spread through surface runoff or leaching may transport palliative away from the application area. This paper reports a novel method developed for the determination of BA–VA using gel permeation chromatography (GPC) and nuclear magnetic resonance spectroscopy (¹H NMR) to provide qualitative and quantitative measurements allowing further investigation of polymer-based soil palliatives. The results showed that the average specific refractive index increments (dn/dc) for BA–VA copolymer in two dust palliatives were 0.055 and 0.038 mL/g. The masses of extracted BA–VA were 1400 and 2900 mg from these products. The corresponding limits of quantification (LOQ) for the extracted BA–VA polymer using a refractive index (RI) detector were 11.63 and 17.04 µg, respectively.
... The effect of the copolymer ratio (DMA:LMA) on T g was investigated. This physicochemical property is one significant factor affecting the adhesive properties [43]. Figure S18 illustrates the thermograms of PSA-1000, PSA-2000, PSA-3000, PSA-4000, and PSA-5000. ...
Renewable polymers possess the potential to replace monomers from petrochemical sources. The design and development of polymeric materials from sustainable materials are a technological challenge. The main objectives of this study were to study the microstructure of copolymers based on itaconic acid (IA), di-n-butyl itaconate (DBI), and lauryl methacrylate (LMA); and to explore and to evaluate these copolymers as pressure-sensitive adhesives (PSA). The copolymer synthesis was carried out through batch emulsion radical polymerization, an environmentally friendly process. IA was used in a small fixed amount as a functional comonomer, and LMA was selected due to low glass transition temperature (Tg). The structure of synthesized copolymers was studied by FTIR, 1H-NMR, Soxhlet extraction, and molecular weight analyses by GPC. Furthermore, the viscoelastic and thermal properties of copolymer films were characterized by DMA, DSC, and TGA. The single Tg displayed by the poly(DBI-LMA-IA) terpolymers indicates that statistical random composition copolymers were obtained. Moreover, FTIR and NMR spectra confirm the chemical structure and composition. It was found that a cross-linked microstructure and higher molecular weight are observed with an increase of LMA in the feed led. The Tg and modulus (G′) of the copolymers film can be tuned with the ratio of DBI:LMA providing a platform for a wide range of applications as a biobased alternative to produce waterborne PSA.
... Acrylate copolymers with good physical and chemical properties are widely used for adhesives [12,13], coatings [14], oil-resistant rubber [15], and optical devices [16,17]. In addition, they can be easily prepared by free radical polymerization under mild conditions. ...
Combining the advantages of solvent-based and water-based anticorrosive coatings, a waterborne composite dispersion of hydroxy acrylic resin (HAR) and modified graphene oxide (MGO) was prepared for application as an anticorrosive coating. MGO was obtained using 3-aminopropyltriethoxysilane as the coupling agent to introduce NH2 groups onto the graphene surface. HAR with COOH, OH and epoxy groups was prepared at a high solid content of up to 80% through solution copolymerization using methacrylic acid, hydroxyethyl methacrylate, methyl methacrylate, n-butyl acrylate and styrene as monomers, tert-butyl peroxybenzoate as the initiator, and propanediol butyl ether and dimethylbenzene as solvents. The covalent bonds between NH2 and epoxy groups would be formed after blending MGO dispersion and the neutralized HAR to improve its compatibility. The effect of dosage of MGO on the viscosity of water-dispersion of HAR (WHAR), and the hardness, adhesion, contact angle of film formed by WHAR, and the anticorrosive performance of the composite coatings were investigated in detail. Results showed that the more MGO added, the higher viscosity of WHAR-MGO. A small amount of MGO formed a barrier layer after being evenly distributed in the coatings, but excessive MGO agglomerated, thereby reducing the compatibility. Composite coatings with 0.25% MGO had the best corrosion performance in 3.0 wt% NaCl aqueous solution, and the |Z|0.01Hz was 10–20 times higher than other coatings with or without MGO, and the Icorr was 10 times lower than coating without MGO. This work provides a good way to balance the environmental issue of organic solvent emission and corrosive properties of water-borne polyacrylate coatings.
... The adhesive T g influences the final adhesive properties and the stiffness of the chains will affect wetting of the adhesive on the surface of the desired substrate (Jovanovic and Dube, 2005). The hydrocarbon side chain of Physaria oil can increase free volume by creating more unoccupied space between polymer chains yielding a reduction in the measured T g (Sun, 2005). ...
Polyurethanes (PU) are an important class of materials used in various applications across industries. With increased global interest in sustainable and environmentally benign packaging, there is high demand to replace traditional petroleum-based materials with renewable, bio-derived sources. This research developed PU adhesives for multilayer flexible food packaging using Physaria fendleri oil (formerly Lesquerella fendleri) and Ricinus communis (Castor oil), each possessing naturally occurring hydroxyl functional groups. Physaria oil has, on average, hydroxyl functionality on two of the three fatty acids compared to all three for Castor oil; therefore systematically varying the concentration of each oil and maintaining a constant crosslink density for each adhesive facilitates an understanding of the effect of Physaria oil's unreacted hydrocarbon sidechain on physical properties in biobased adhesives. The results of this study determined that the peel resistance of polyethylene and polyethylene terephthalate substrates adhered with adhesives containing varying amounts of Physaria and castor oils possessed average peel strengths of 6–8 N relatively independent of composition. Furthermore, the glass transition temperatures were measured to be within the range of −25 to −44 °C with higher concentrations of the hydrocarbon sidechain resulting in lower Tgs. These physical properties indicate their use in multilayer food packaging adhesive applications where isocyanate PU adhesives are still commonplace. Understanding the PU adhesive network structure-property relationships will help develop the next generation of bio-derived PU adhesives with additional sources of renewable feedstocks for food packaging applications.
... The cohesive and adhesive properties of the copolymers are balanced by selection of the molar mass, polarity and low glass transition temperatures (normally between −25 to −70°C) [3]. Other monomers such as methyl or ethyl methacrylate [4] or vinyl acetate [5,6] may also be incorporated in the copolymer structure. The higher polarity of the incorporated comonomer has no measurable effect on the surface tension but leads to an increase of shear modulus and consequently, to an increase in the stress peak, deformation at break, tack values, as well as the total number of cavities. ...
The creation of micrometer adhesive pads by dewetting and subsequent crosslinking of a benzophenone-acrylate copolymer onto a substrate that is lithographically patterned with a benzophenone-fluoropolymer, has been investigated in relation to the adhesive performance of either continuous or patterned adhesive interlayers. First, the intrinsic adhesive properties of a n-butyl acrylate methacryloyl-4-oxy-benzophenone copolymer were investigated as a function of composition (4, 10, 20 mol-% benzophenone), concentration (1–5 mg/ml) and photochemical cross-linking conditions (1–120 min). Under optimized conditions, the benzophenone-acrylate provides a good balance of adhesive strength and ductility at low concentrations of photo-reactive groups and performs better than reference adhesives. The latter can be understood by the formation of a dense polymer network with different degree of crosslinking resulting in high stiffness. Second, the benzophenone-acrylate was successfully confined into adhesive pads through spontaneous flow and pinning of the contact line of the liquid adhesive at the hydrophobic/hydrophilic interface of chemically patterned substrates, followed by dimensional stabilization of the droplet shape through partial crosslinking. The adhesive strength of interfaces with discrete adhesive pads (diameter 2000 to 500 μm) is significantly higher than continuous adhesive interlayers and is confirmed by cohesive failure of the adhesive.
... This may have occurred because the polymer chain of latex GNR-80:20 did not sufficiently wet the substrate. The wetting ability of the polymer chain in this latex may have decreased due to short branching (Jovanovic and Dube, 2005). In addition, the number of graft copolymers presented in the latex may not be high enough. ...
In order to study the potential of increasing the weather stability of natural rubber latex for use as a water-based contact adhesive, the natural rubber latex was modified by graft copolymerization with n-butyl acrylate (BA) and methyl methacrylate (MMA). The grafting reaction was carried out using emulsion polymerization at 60° ° ° ° °C. Potassium persulfate was used to initiate polymerization. Four different weight percentage ratios of BA to MMA used in this work were 95:5, 90:10, 85:15 and 80:20. Percentage conversion of the monomer of all latexes prepared was ≥ ≥ ≥ ≥ ≥ 79.5%. The grafting efficiency of graft-modified natural rubber with a different monomer ratio tends to decrease with an increase of MMA. 1 H-nuclear magnetic resonance spectroscopy ( 1 H-NMR) confirmed that the latexes which were prepared contained graft copolymer. The adhesive performance was characterized by 90° ° ° ° ° peel strength tests. Only graft-modified natural rubber latex with the monomer ratio of 80:20 possessed an adhesion property enough to conduct peel testing. The peel strength value of graft-modified natural rubber was lower than that of natural rubber latex. However, graft-modified natural rubber latex tends to have a higher weather stability than natural rubber latex.
... Peel strength, tack and shear resistance are strongly dependent on the emulsion particle size distribution, polymer molecular weight distribution, polymer gel fraction, and copolymer composition. The glass transition temperature affects the adhesion properties by determining the softness of the PSA, which is needed for an appropriate flow of the adhesive during the film formation process [45]. In the PSA industry, T g is normally tailored via the copolymerization process via the selection of different monomers [24,46]. ...
... En el campo de los recubrimientos, la tecnología de los polímeros afronta ambiciosos retos para lograr productos con bajos niveles en emisión de compuestos orgánicos volátiles (VOCs), alta durabilidad a la intemperie, rápido curado, buena adhesión a diferentes sustratos y baja sensibilidad a la humedad [1][2][3][4] . Cada vez son más los procesos que se están encaminando a la producción de polímeros en emulsión, en los cuales se busca obtener una dispersión de los monómeros en un liquido inmiscible con ellos, que generalmente es agua. ...
Results on the emulsion polymerization of a styrenated acrylic resin using polymerizable surfactants are presented. These surfactants exhibit low foaming, high film strength upon contact with water and good stability in the polymerization. A comparison was made with results for conventional non-polymerizable alkyl aryl polyglycol ether sulphate, sodium salt and nonylphenolethoxylate surfactants. The effect of these polymerizable surfactants on the particle size distribution of the resin was evaluated; in addition to determining the final properties of the resin such as solids content, free monomer content, viscosity and pH. It is feasible to totally replace non-polymerizable surfactants by the polymerizable surfactants evaluated without affecting significantly the properties of the resin, while partial substitution of the non-polymerizable surfactants induces, in some cases, the formation of particles with larger sizes than those in the standard resin.
... A model for the adhesion between the PSA and each substrate may be modeled based on a systematic investigation of the influence of the SFE on the tack performance. Several recent studies of the adhesion of PSAs to different substrates [13][14][15] have been reported. In the majority of cases, only two types of substrate were studied: stainless steel and polyolefins (PE, PP). ...
This article describes a comparative study of the tack properties of a model acrylic pressure-sensitive adhesive (PSA) crosslinked using aluminum acetylacetonate on several substrates, including stainless steel, glass, polyethylene, polypropylene, polytetrafluoroethylene, polycarbonate, and poly(methyl methacrylate). The tack measurements were conducted using a technique commonly used to measure the tack of an adhesive tape in the PSA industries. The surface free energy (SFE) values of the materials were evaluated using the Owens–Wendt and van Oss–Chaudhury–Good methods. The experiments showed a clear relationship between the SFE of the substrate and the tack of the model acrylic PSA. In general, larger differences between the SFE values of the substrate and adhesive (ΔSFE) were correlated with greater tack values. The tack of the model acrylic PSA was found to be optimal over the ΔSFE range of 7.0–13.1 mJ/m2. The trend in the tack as a function of the SFE difference was attributed to the quantity of energy dissipated at the jointed points during the separation stage in the loop tack test.
... Based on results of our previous studies of microsphere adhesives, a strong correlation exists between the adhesive properties and amount of gel phase [1][2][3]. According to the published studies, other researchers found that the amount of gel content (beside the molecular weight and molecular structure) was among the most influential factors affecting the final PSA performance [18][19][20]. ...
In the following study, a synthesis and characterization of UV crosslinkable acrylic pressure sensitive adhesives are presented. Different amounts of unsaturated photoinitiator 4-acryloyloxy benzophenone (4-ABF) were added in t-butyl acrylate/2-ethylhexyl acrylate monomer mixture and then polymerized using a suspension polymerization technique. The adhesive suspension was coated on a pilot coating machine, dried by application of IR and subsequently crosslinked under UV light. The copolymerized 4-ABF photoinitiator will produce reactive radicals upon absorption of UV light, which are capable of initiating a rapid chain reaction with neighboring C–H positions of polymer side chains, what leads to formation of crosslinked polymer structures. UV crosslinking process was monitored by ATR-FTIR spectroscopic technique. Adhesion properties of the synthesized materials were determined using standard measurements of tack, peel and shear strength. Results have shown that all adhesive properties are strongly influenced by the degree of crosslinking of the microspheres, which increased with higher amounts of added 4-ABF photoinitiator. All the three measured adhesive properties showed a substantial decrease even at small amounts of added 4-ABF. The decrease in adhesion may be correlated with higher crosslinking density, what also resulted in higher gel phase amounts. Determination of glass transition temperature showed minor difference between adhesive coatings.
... Acrylic-based latexes are widely employed in formulations that can be used in adhesives [1], waterborne coatings [2], drug-releasing devices [3], and immobilization of enzymes [4] and microorganisms [5], i.e. in virtually any important area of scientific/economic activity. ...
Latexes based on acrylic acid, acrylamide, ethyl methacrylate, and ethyl acrylate were synthesized via emulsion polymerization with different monomer compositions. The resultant latices were thickened with different molar ratios of NaOH to acrylic acid and were analyzed in terms of acid-basis titrimetry, turbidimetry, rheology, and tensiometry. Titrimetry, turbidimetry and rheometry were used to analyze factors such as carboxyl group availability and particle solubilization, tensiometry monitoring the influence of carboxyl neutralization on polymer-surfactant interactions. For the acrylic acid content used in this work (20 wt%), the results indicated that as carboxyl groups distribution became more homogeneous, the process of latex thickening became more effective.
A series of fluorinated polyacrylate emulsion pressure-sensitive adhesives (PSA) with various lengths fluorinated side chains were synthesized by using n-butyl acrylate (nBA), acrylic acid (AA), 2-hydroxyethyl acrylate (HEA) together with three kinds of fluorine monomers trifluoroethyl methacrylate (TFEMA), hexafluorobutyl methacrylate (HFBMA) and dodecafluoroheptyl methacrylate (DFHMA). The influences of fluorocarbon chains’ length on the particle size of the latex, as well as on thermostability (DSC, TG) and surface properties (XPS, CA, AFM) of the PSA films were investigated. The results showed that Tg and thermal stability of the PSA were both increased with the introduction of F-monomers with various lengths of fluorinated side chains, and the shorter the side chain, the more the Tg and thermal stability increased. The XPS results indicated that the surface atom percentage of F element of film increased with the escalation of the length of fluorocarbon lateral chain, which results in the water contact angle and surface roughness increment of the PSA films. Finally, effects of fluorocarbon chains’ length on the adhesive properties (i.e. loop tack, peel strength and shear strength) of the fluorinated latex PSA were also evaluated.
Polymer nanocomposites revolutionized research in the composites area by achieving the nanoscale dispersion of the inorganic filler (clay platelets) in the polymer matrices after suitable surface modifications of the filler phase. A large number of polymer matrices were tried and nanocomposites with varying degrees of successes were achieved with these polymer systems. The majority of the synthesis are carried out by melt blending which frequently result in the full exfoliation of the filler. However, advanced techniques provide a number of advantages as compared to the melt blending and lead to more uniform composites with enhanced properties. There are a number of recent advances in these methods such as the use of reactive surfactants, modified initiators, advanced clay surface modifications, use of a variety of fillers, inverse polymerization, and miniemulsion polymerization methods which have further led the generation of advanced exfoliated nanocomposites. Until now, most of the published research has been scattered throughout the literature. This book provides a single comprehensive source of information about one of the most important facets of polymer nanocomposites technology: synthesis in emulsion and suspension. These polymerization methods lead to the generation of the well delaminated polymer nanocomposites with a wide range of polymer matrices. This book serves as both a professional reference for experienced researchers and a valuable text for newcomers to the field. It makes the reader aware of the potential commercial use of these recent developments.
Historically, analytical test methods on pressure sensitive adhesives (PSAs) have shown modest correlation to applications test results. Since applications tests such as peel strength and shear strength involve large deformations of the adhesive, large amplitude oscillatory shear (LAOS) experiments may correlate more strongly to the applications test results than typical linear viscoelastic measurements. Here we report some of the earliest LAOS measurements on commercial PSA films and compare them to the measured peel strength and shear strength. The parameters, G’M, Q, and e3/e1, showed a strong correlation to the peel and shear results while the parameters, S, T, and v3/v1, demonstrated weaker dependencies. While detailed molecular level interpretation of the LAOS results is not possible, these results indicate LAOS testing may provide a better indication of applications performance in a more efficient way than existing applications test protocols.
This present work focuses on the synthesis of styrene / n-acylglycerol (n-ACG) (a macromonomer formed by glycerol esterification with acrylic acid catalyzed by methane sulfonic acid) copolymers through suspension polymerization process. The final properties of poly(styrene-co-n-acylglycerol) was strongly dependent on the n-ACG fraction into the polymer chains. The effect of n-ACG on the copolymer properties was evaluated and a huge reduction in both the thermal stability and the Tg values (from 93 °C for polystyrene homopolymer to −22 °C for styrene / n-ACG copolymers synthesized with 20 wt% of n-ACG) was observed when the n-ACG fraction was increased. The variations in the thermal properties were accompanied by drastic morphological changes of the materials, depending essentially on the n-ACG composition as for instance: i) porous spherical particles with polyHIPE-like structures (copolymers containing from 5 to 15 wt% of n-ACG), which indicates that these porous microparticles may be used as support/carries in heterogeneous catalysis, ion exchange resins, and controlled drug delivery, among others; ii) adhesive films containing n-ACG fractions higher than 15 wt%, conferring "tack" features similar to the one observed in for pressure-sensitive adhesives (PSA) evaluated by using a rolling ball test. Mechanical tests also showed that the polymer adhesives have an enormous potential to be used as PSA materials in the adhesive industry.
Fluorinated acrylate emulsion pressure sensitive adhesives (PSA) based on butyl acrylate (BA), fluorine monomer dodecafluoroheptyl methacrylate (DFMA), acrylic acid (AA) and 2-hydroxyethyl acrylate (HEA) were synthesized via a monomer-starved seeded semi-continuous emulsion polymerization process. The influences of DFMA on the resultant latex and PSA properties were comprehensively investigated. FTIR analysis indicated that DFMA could be successfully introduced into the latex PSA copolymer through emulsion polymerization. DSC and TG analyses showed that Tg and thermal stability of the PSA were both improved as DFMA content increased. XPS analysis indicated that fluoroalkyl groups had a tendency to enrich on the surface of the film, and the more DFMA added the more F content on the film surface. Moreover, the surface roughness and contact angle of the acrylate latex PSA film were both increased with the introduction of DFMA. Dynamic mechanical analysis (DMA) and adhesive property tests showed that the storage modulus (Gʹ) and shear holding power were improved with DFMA content while at the sacrifice of loop tack. Finally, 180° peel strength of fluorinated acrylate latex PSAs on different substrates (PP, SS) as a function of DFMA content was evaluated.
Acrylic latex laminating adhesives (ALLAs) were successfully prepared via a monomer-starved seeded semi-continuous emulsion polymerization with butyl acrylate (BA), methyl methacrylate (MMA), styrene (St), acrylamide (Am), and methacrylate glycidyl ether (GMA) as monomers. Impacts of GMA on the final latex, the dried latex films and the adhesive properties of ALLAs were investigated, respectively. The results indicated that the increase of GMA contents in the pre-emulsion feed has no apparent effect on the final latex average particle size and size distribution, while the gel contents, glass transition temperature (Tg) and water contact angle of the ALLAs gradually increased, and the molecular weight (Mn, Mw) obviously increased. Additionally, as the amount of GMA increased from 0 to 10 wt%, the maximum peel strength of the composite films reached 3.72 N/15mm with 5 wt% GMA contents. When heated to 65 °C, the peel strength of the composite films with 5 wt% of GMA can still maintain an acceptable peel strength (2.51 N/15mm) for application, showing excellent adhesive performance and heat resistance properties.
Waterborne pressure sensitive adhesives with biobased contents up to 72% and adhesive performance comparable to pure oil-based formulations have been developed. For that, partially biobased commercial 2-octyl acrylate and isobornyl methacrylate monomers (derived from castor oil and pine resin, respectively) are copolymerized by emulsion polymerization, an environmentally friendly procedure which allows fine-tuning the microstructure of the copolymer at high solids content as well as notably reducing the VOCs in the final product. Formulations with well balance adhesiveness and cohesiveness are achieved, and the reasons are thoroughly discussed. Furthermore, the moderate reduction of the bio-content by the substitution of part of 2-octyl acrylate by the oil-based 2-ethylhexyl acrylate provides trade off waterborne formulations with very promising adhesive properties.
Fluorinated acrylic pressure sensitive adhesive (PSA) latexes based on butyl acrylate (BA), acrylic acid (AA), 2-hydroxyethyl acrylate (HEA) and 2,2,2-trifluoroethyl methacrylate (TFMA) were synthesized via a monomer-starved seeded semi-continuous emulsion polymerization process using a reactive emulsifier. Effects of TFMA on the resultant PSA properties were comprehensively investigated. IR analysis indicated that TFMA can be introduced into the latex particles successfully through emulsion polymerization. Gel content and sol molecular weight of the PSA were not significantly affected by the addition of TFMA. It was also found that Tg and thermal stability of the PSA were both improved remarkably as TFMA content increased. Water resistance of the PSA was enhanced, while surface energy of the PSA was decreased with TFMA concentration increased, which were confirmed by XPS analysis. Moreover, the storage modulus (Gʹ) and loss modulus (Gʺ) of the PSA increased with TFMA content. Peel strength of the PSA on PP surface was not affected by the presence of TFMA, while peel strength of the PSA on SS and PC surfaces were first decreased and then increased with the TFMA content. Besides, the influences of reactive surfactant SR-10 and conventional surfactant CO-436 on the acrylic latex PSA were also compared.
A series of hyperbranched polymers (HBPs) were synthesized and measured by FT-IR and 1H-NMR. Two types of HBPs with-COOH and-COOH/-OH as end-groups were used to modify the performance of BA/VAc/AA emulsion-based pressure-sensitive adhesives (PSAs). The influences of the HBPs on the properties of PSAs were discussed. It is found that both the stability and the adhesive properties of PSAs are improved by HBPs. Further more, 0.5% HBP as the modifier with-COOH as end groups increase shear strength and peel strength to the maximum, which are two conflicting properties of emulsion-based PSAs.
We report novel insights into the adhesive performance of bio-based pressure sensitive adhesives (PSAs). Three different homopolymers based on renewable fatty acid methyl esters were characterized in terms of their mechanical and adhesive properties. The polymers display the typical dependence of adhesive properties on molecular weight and degree of crosslinking, as quantified by shear modulus, tack and peel measurements. The absolute values of characteristic adhesion parameters are in the range of commercially available petrochemical PSAs. Curing of applied PSA films at elevated temperature results in a pronounced maximum in tack and peel strength at a critical curing time, which corresponds to a change from cohesive to adhesive failure. Thus, demand-oriented tailoring of adhesive properties can be achieved via an appropriate choice of curing time. Moreover, these bio-based adhesives offer improved adhesion on hydrophobic substrates and high water-resistance without any whitening, thus rendering them an attractive alternative to conventional petroleum-based products. These peculiar features are attributed to the high hydrophobicity of the used monomers.
Reversible addition-fragmentation chain transfer (RAFT) polymerization has been applied in the synthesis of controlled molecular weights and dispersity of poly (2-ethylhexyl acrylate) (PEHA) by the miniemulsion technique. The RAFT agent (2-cyanoethyl morpholine-4-carbodithioate) was synthesized and used for 2-ethylhexyl acrylate (2-EHA) polymerization at molecular weights of 2 × 105, 7 × 10, 14 × 105, and 20 × 105 Da and polymerization reaction kinetics were studied. The RAFT agent was characterized by Fourier transform infrared (FTIR) spectroscopy, 1H-nuclear magnetic resonance (1H-NMR) spectroscopy, and mass spectroscopy. The synthesized emulsions were characterized by gel permeation chromatography, particle-size analysis, x-ray diffraction (XRD) analysis, and rheological characterization. The PEHAs were used as adhesives for coated and uncoated laminates with low and high surface energies and materials, and their properties such as tack, lap shear strength, peel strength, and shear holding strength were assessed.
The cross-linkable laminating adhesives (LAs) based on core-shell vinyl acetate/acrylate latexes were synthesized through multistage emulsion polymerization. The effects of core copolymer Tg, core/shell weight ratio, cross-linking structure and molecular structure on the peel strength of LAs were studied. It was found that peel strength increases with the decrease of core/shell weight ratio and core copolymer Tg. And cross-linking structure could improve adhesion properties of LAs evidently. Moreover, the molecular structure of core-shell latexes has a significant influence on adhesion properties of LAs. The peel strength of sample 14-H could reach 3.4 N/15 mm even under 60°C by particle structure design.
The polyacrylate emulsions tackified by polymerized rosin were prepared via seeded semicontinous emulsion polymerization. The effects of polymerized rosin on the monomer conversion, particle size, polymer microstructure (gel fraction, cross-linking density and sol molecular weight) and adhesive properties were studied. The instantaneous conversion, gel fraction, cross-linking density and sol molecular weight decreased significantly due to the chain transfer and inhibition of the abietic acid. Also, the related mechanism was discussed. Dynamic light scattering was used to monitor the particle size of tackified emulsion. The relationship between the main adhesive properties of tackified latex films and polymer microstrcuture was studied.
Pressure sensitive adhesives (PSAs) were produced using latexes synthesized via a starved seeded semi-batch emulsion polymerization process with butyl acrylate (BA), methyl methacrylate (MMA) and sometimes additional monomers, 2-hydroxy ethyl methacrylate (HEMA) and/or acrylic acid (AA). For the BA/MMA comonomer latexes, the amount of cross-linker (allyl methacrylate), monomer emulsion and initiator solution feeding times, and the BA/MMA weight ratio were manipulated to vary the polymer properties. The performance of PSA films cast from these latexes was evaluated by tack, peel strength and shear strength. The effect of polymer properties on PSA performance was related to the viscoelastic properties of the PSAs. For BA/MMA latexes, it was not possible to greatly improve the peel strength even at great sacrifice of shear strength for PSAs with gel contents of ∼60 wt% or higher. This was because the ratio of the loss modulus at debonding frequency to the storage modulus at bonding frequency did not vary significantly for the conditions studied. The addition of HEMA provided a significant influence on latex polymer properties as well as PSA performance for both high (>60 wt%) and low (∼20 wt%) gel contents. For some cases, tack, peel strength and shear strength were simultaneously and greatly improved by the addition of HEMA. Adding both AA and HEMA while decreasing the amount of emulsifier, also resulted in a PSA with much better performance (i.e., higher tack, peel strength and shear strength) than a BA/MMA PSA with similar gel content (∼60 wt%).
Pressure-Sensitive Adhesives (PSAs) are used for many applications (e.g. tapes and labels), and the market is still growing as new applications are regularly discovered. Emulsion polymerization is widely used to produce water-based PSAs. In this work, the influence of morphology, diameter and acrylic acid concentration in the particles on adhesion properties (peel, tack and shear) was studied. To do so, two series of homogeneous and core-shell latex particles of poly(butyl acrylate-2-ethyl-hexyl acrylate) with different concentrations of acrylic acid (0, 1, 3 and 5 wt%) and three different average diameters, were synthesized by means of emulsion polymerization techniques. The materials were characterized by dynamic light scattering, zeta potential and transmission electronic microscopy. The contents of acrylic acid in the polymer and dispersed medium were determined and the higher quantity of it was found within the particles. The best equilibrium between adhesion properties was found in the core-shell particles with 3 wt% of AA.
The influence of the amounts of acrylic acid, chain transfer agent and anionic stabilizer on polymer microstructural properties and final adhesive performance of BA/VAc emulsion-based PSAs on stainless-steel and high-density polyethylene substrates was investigated using a Box-Behnken experimental design for 15 runs. The resulting data were empirically modelled. For each final adhesive property (i.e., loop tack, shear and peel strength), different models were found to fit the data. Similar models for loop tack and peel strength were found to be adequate for different PSA thicknesses on the same substrate. AA and SDS had significant effects on loop tack as did the AA-SDS and CTA-SDS two-factor interactions. Quadratic peel strength models were found to adequately describe the data for SS substrate cases with a noticeable absence of any interaction parameters. The shear strength models were similar regardless of the substrate or thickness of the adhesive (e.g. in all models, AA and CTA, as well as their second-order interactions, were the significant factors).
In this work, the effect of polymer molecular weight and crosslinking reactions on the end-use properties of the microsphere water-based acrylic pressure-sensitive adhesives (PSA) is presented. Polymer molecular weight and polymer microstructure were regulated using different chain transfer agent (CTA) concentrations and by addition of a diacrylic monomer (MM). The adhesion properties of the synthesized PSAs were characterized via measurements of tack, peel adhesion and shear strength. The results of experiments have shown that the kinetics of suspension polymerization is relatively independent on the amount of CTA and MM. The amount of gel phase in the adhesive was reduced with increasing amount of CTA agent, and gel phase amount may be considered as a function of polymer molecular weight. With a combination of CTA and MM was possible to regulate the amount of formed gel phase in the adhesive, as well sol phase molecular weight. All of the measured adhesion properties strongly depend on molecular weight of the synthesized polymer and on the amount of gel phase. For adhesives synthesized solely with addition of CTA, tack decreased with lower polymer molecular weight and consecutively also with lower amount of gel phase. The same trend was also observed for peel strength measurements, whereas a cohesive failure was observed for adhesives with low amount of gel phase. A maximum value for tack and shear strength was observed at 80 wt% of gel phase. In case of syntheses with a combination of CTA and MM (amount of gel phase in range from 70 to 80 wt%), tack values were distributed in quite narrow range. On the other hand, peel strength values decreased in comparison with adhesives synthesized only with CTA, regardless to the equal amount of gel phase. Poor shear strength was observed for all adhesives synthesized by combination of CTA and MM.
In this paper, the batch suspension copolymerization process for production of microsphere acrylic pressure-sensitive adhesives (PSA) is presented. The effects of different process and chemical parameters on adhesion properties are discussed. The reaction was monitored in-line by using attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy. Properties of the adhesive suspension (particle size), adhesive (gel phase, molecular weight, glass transition temperature (Tg)) and adhesion properties (tack, peel strength and shear) were determined. The results have shown that reaction kinetics strongly depends on polymerization temperature and initiator concentration. On the other hand, adhesion properties depend mainly on the Tg of the polymer and on the amount of insoluble gel fraction in the adhesive.
Statistical copolymer films that consist of two types of monomers, a sticky and a glassy monomer, are investigated. These model systems of pressure-sensitive adhesive films are probed with X-ray reflectivity and mechanical tack measurements. For the first time, composition profiles along the surface normal in the near-surface region are monitored. The influence of the type of monomers being copolymerized, the monomer ratio, and the sample age on the near-surface composition as well as the resulting adhesive performance of the films are analyzed. The copolymers contain ethylhexyl acrylate as the majority component and styrene, maleic acid anhydride, or methylmethacrylate as a minority component. Regardless of the composition, we find a surface enrichment of one component in all samples. In the case of freshly prepared samples, this enrichment is driven by solubility due to the preparation based on solution casting. The minimization of the surface free energy results in an internal reorganization and the component of the statistical copolymer with the lower surface tension enriches at the free surface. The mechanical behavior is not dominated by the surface but by the surface-near part of the composition profile.
The effects of plasticizer inclusion (10%, w/w) on roughness, mechanical and adhesive properties of novel skin-bioadhesive patches produced from polyvinyl alcohol and polyvinyl pyrrolidone were studied. Dry, non-adhesive patches became adhesive upon wetting. Roughness profiles of the patches and a skin model were studied, by measuring average values of Ra (recognized as average roughness in practice) and Rz (average of the vertical distances from the highest peak to the lowest valley within five equal sampling lengths). These values ranged from 2.4 to 3.8microm and from 10.9 to 12.5microm, respectively. Plasticizers had no significant effect on them. The average Ra obtained for the skin model was six- to eightfold higher than that obtained for the patches. Plasticizer inclusion caused a reduction in patch tensile strength and an increase in its strain at failure-the lower the plasticizer's molecular weight, the greater its effect. Plasticizer inclusion also caused a significant reduction in peeling force: 1.5+/-0.11 and 2.8+/-0.13g force/cm for patches with and without glycerol, respectively. Patch adhesion to the skin also depended on the time elapsed between application and removal. In summary, plasticizer inclusion widened the range of mechanical and adhesive properties of the patches.
The batch emulsion copolymerization of styrene with n-butyl acrylate in the presence of acrylic and methacrylic acids was investigated. Values of reaction rate and conversion observed at different pH values were examined. The effect of pH on the glass transition temperature of the polymers was also investigated and the results compared with model predictions. Its effect on the distribution of the carboxyl groups at different positions within the emulsion system (surface and core of particles, and in the aqueous phase) was also analyzed. Three methods were used to measure the number of carboxyl groups: conductimetry, organic phase potentiometry, and titration with a solution of sodium hydroxide in methanol. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65: 2343–2355, 1997
Pressure-sensitive products (PSPs) are multilayer constructions based on solid-state materials and coated components (see Applications of Pressure-Sensitive Products, Chapter 1). Th erefore, the production of the PSPs includes the manufacture and assembly of the individual components. Th e manufacture of the components includes the manufacture of both the solid-state carrier materials (face stock and release liner) and the coating components (adhesive, abhesive, primer, etc.) (see also Chapter 8). Generally, the buildup of the PSP from its components is carried out by coating and laminating and leads to a web-like product that must be confectioned. Table 10.1 presents the manufacturing technology of main PSPs and demonstrates that the manufacture of PSPs by coating of a solid-state carrier with a liquid pressure-sensitive adhesive (PSA) is the main procedure to produce various PSPs.
Relationships between the peel strength and the composition of an adhesive, vinyl acetate-butyl acrylate copolymer, and its peel rate were studied. It was shown that, as the content of butyl acrylate units in the copolymer increases and the peel rate grows, variations in the peel strength can be described by curves with a maximum and are accompanied by a transition from the cohesive to adhesive character of failure. It was demonstrated that the strength of the tested adhesive joints is characterized by an ultimate failure stress and the peel strength is dependent on the work of deformation of the adhesive layer. A simple procedure for determining the contribution from the work of deformation to the peel strength was suggested.
Direct 13C n.m.r. evidence for chain transfer to polymer in emulsion polymerization of n-butyl acrylate is reported. This reveals that the reaction proceeds by abstraction of tertiary C-H bonds in n-butyl acrylate repeat units and, under the usual condition of high instantaneous conversion, leads to polymers with high extents of branching (10-20 branches per 1000 backbone carbon atoms). Changes in molar mass distribution during emulsion polymerization correlate with observations on the extent of chain transfer to polymer.
For studying k variables in N runs, all 2 designs of maximum resolution are not equally good. In this paper the concept of aberration is proposed as a way of selecting the best designs from those with maximum resolution. Algorithms are presented for constructing these minimum aberration designs.
Analysis using molecular mechanics has been performed on the six-bond aliphatic link segment formed when diglycidyl ether of bisphenol-A (DGEBA) is cured with aromatic amines. It is found to have restricted conformational freedom owing to coulombic repulsion between oxygen and nitrogen atoms. Hence the segment can be approximated by a virtual bond about 9.5 Å long. The study of the local network structure is therefore simplified.
The batch emulsion copolymerization of styrene with n-butyl acrylate in the presence of acrylic and methacrylic acids was investigated. Values of reaction rate and conversion observed at different pH values were examined. The effect of pH on the glass transition temperature of the polymers was also investigated and the results compared with model predictions. Its effect on the distribution of the carboxyl groups at different positions within the emulsion system (surface and core of particles, and in the aqueous phase) was also analyzed. Three methods were used to measure the number of carboxyl groups: conductimetry, organic phase potentiometry, and titration with a solution of sodium hydroxide in methanol.
Pressure sensitive adhesives (PSAs) adhere instantaneously to a variety of surfaces upon application of slight pressure and can be obtained using different technologies. Increasing environmental concerns and regulations are the major driving forces for the development of emulsion‐based PSAs. Given the number of factors affecting the emulsion polymerization process and versatility of emulsion‐based polymers, there is a need to identify and model those factors that significantly influence particular PSA applications. In this review, factors such as emulsion polymerization components, latex rheology, and film formation are examined in light of their relevance to adhesion. In addition, the body of knowledge related to measurement methods, design factors, and modeling of each of the three major PSA performance characteristics (i.e., tack, peel strength, and shear strength) is reviewed with a particular emphasis on emulsion‐based PSAs.
The effects of the initial monomer concentration, [M]o, and percent conversion on the extent of chain transfer to polymer in free-radical solution polymerization of n-butyl acrylate has been studied. The polymerizations were carried out in cyclohexane at 70 °C using 0.1% (w/w) 2,2‘-azobis(2-cyanopropane) as initiator and the mole percent branched repeat units (mole percent branches) in the poly(n-butyl acrylate) was determined from unique resonances of branch-point carbons in the 13C NMR spectra. At [M]o > 10% (w/w) the mole percent branches is independent of [M]o and increases from 0.8 to 2.2% as conversion increases from 35 to 95%. However, for more dilute solutions, with [M]o ≤ 10% (w/w), the mole percent branches increases as [M]o decreases and is higher than at equivalent conversions for the more concentrated solution polymerizations; e.g., at 25% conversion the mole percent branches increases from 2.7% for [M]o = 10% (w/w) to 5.9% for [M]o = 3% (w/w). These observations are explained in terms of the ratio of the concentrations of polymer repeat units and monomer in the vicinity of the propagating chain end. In more concentrated solutions, intermolecular chain transfer to polymer dominates because, at all except the lowest percent conversions, the overall polymer repeat unit concentration is sufficient for overlap of individual polymer coils. However, in the dilute solutions the overall polymer repeat unit concentration is too low for overlap of individual polymer coils and intramolecular chain transfer to polymer dominates. Under these conditions, the local polymer repeat unit concentration within the isolated propagating chains is defined by the chain statistics and so is approximately constant, whereas the monomer is distributed uniformly throughout the solution. Thus, for dilute solutions, as [M]o decreases, the probability of chain transfer to polymer (and hence the mole percent branches) increases.
Two series of emulsion polymers with n-butyl (meth)acrylate and the bifunctional monomer methallyl methacrylate were prepared, covering the whole range from un-cross-linked to highly cross-linked particles. Dynamic mechanical measurements showed that films from slightly or moderately cross-linked particles behave like homogeneous networks in the linear viscoelastic range. Measurements of the fracture energy per unit volume, W(B), of poly(butyl methacrylate) films gave insight into the development of mechanical strength by interdiffusion across particle boundaries. When annealed above T(g), un-cross-linked films show a transition from brittle to tough fracture at short annealing times, followed by a further gradual increase of W(B) linear with the square root of the annealing time. On the basis of these measurements and small-angle neutron scattering experiments on the same samples,7 a three-stage process is proposed for the development of film strength. Films from particles so highly cross-linked that the mean molecular mass between cross-links becomes smaller than the entanglement length M(e) remain brittle upon annealing. Interdiffusion and the formation of interparticular entanglements are impossible in these latex films.
A method to determine the minimum time monomer addition policy for composition control in unseeded emulsion polymerization systems based on calorimetric measurements was developed. The iterative approach requires a series of semicontinuous emulsion copolymerizations to be carried out under semistarved conditions. Only the values of the reactivity ratios and the heat of homopolymerization of each monomer involved are required to apply the approach. The method, which was checked in the vinyl acetate-butyl acrylate emulsion copolymerization, converged in four steps even when technical grade monomers were used.
Model acrylic pressure-sensitive adhesives (PSAs) based on poly(2-ethyl-hexyl acrylate-stat-acrylic acid) and poly(n-butyl acrylate-stat-acrylic acid) at 97.5/2.5 wt % were synthesized using semicontinuous emulsion and solution polymerizations. Microgels formed in the lattices retained their discrete network morphology in the film. In contrast, acrylic solution was essentially gel free and crosslinking in the film was provided by the reaction of acrylic acid and post added Al Acetyl Acetonate after solvent evaporation, which led to continuous network morphology. The difference in film network morphology caused significantly lower shear holding power for the film from emulsion PSA compared with that of solvent-borne film. Unlike shear holding power, loop tack and peel of acrylic PSAs were mainly controlled by the same sol/gel molecular parameters, regardless of emulsion or solution PSAs. The important molecular parameters are sol-to-gel ratio, entanglement molecular weight, weight average molecular weight, and to a lesser extent, glass transition temperature. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 2230–2244, 2001
Emulsion polymerizations of vinyl acetate (VAc) with polyvinyl alcohol (PVA) as emulsifier were carried out by both batch and semicontinuous processes. The extent of grafting of vinyl acetate onto the PVA chains was investigated by a new method for separating the various polymer fractions in high solids content latexes. The quantification was carried out by a three-step separation and selective solubilization of the PVAc latexes. After the separation, the water-soluble PVA and the solvent-soluble PVAc components were characterized by gel permeation chromatography and 13C–NMR, from which the accuracy of this method was verified. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1739–1747, 2001
Introduction Pressure-sensitive Adhesives Self-adhesive Labels Self-adhesive Tapes Test Methods Laminating Adhesives Flexible Packaging Glossy Film Lamination Furniture and Automotive Construction Adhesives Floor-covering Adhesives Sub-floor and Wall Mastics Sealants Ceramic Tile Adhesives Polymer-modified Mortars Waterproofing Membranes Elastomeric Roof Coatings Self-adhesive Labels Self-adhesive Tapes Test Methods Flexible Packaging Glossy Film Lamination Furniture and Automotive Floor-covering Adhesives Sub-floor and Wall Mastics Sealants Ceramic Tile Adhesives Polymer-modified Mortars Waterproofing Membranes Elastomeric Roof Coatings
A study of butyl acrylate (BA) and vinyl acetate (VAc) solution homopolymerization and copolymerization in toluene was carried out. The conversion and copolymer composition were monitored using traditional techniques (gravimetry and 1H-NMR spectroscopy) and attenuated total reflectance-Fourier transform IR (ATR-FTIR) spectroscopy with a diamond-composite probe and light conduit technology. The peak height of the characteristic absorbances of the monomer(s) during the course of the reaction was used to calculate the conversion and copolymer composition for the ATR-FTIR monitoring. The data obtained using a ReactIR™ 1000 reaction analysis system in the off-line mode showed very good agreement with data obtained using traditional techniques. The solvent effects on BA and VAc solution homopolymerizations and copolymerizations in toluene were also investigated. Improvement to model predictions was obtained by allowing the lumped constant (kp/k) to vary with the solvent concentration. Experimental data and model predictions of the number- and weight-average molecular weights for the investigated systems are also presented. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2958–2977, 2001
Applications in the Adhesives and Construction Industries. In Polymer Dispersions and Their In-dustrial Applications
- D Urban
- L Egan
Urban, D.; Egan, L. Applications in the Adhesives and Construction Industries. In Polymer Dispersions and Their In-dustrial Applications; Urban, D., Tackamura, K., Eds.; Wiley-VCH: Weinheim, 2002; pp 191-253.
Analysis of Factors Important in Emulsion Acrylic Pressure Sensitive Adhesives Design
- R M Kell
- L G Boss
- D E Nordhaus
Kell, R. M.; Boss, L. G.; Nordhaus, D. E. Analysis of Factors Important in Emulsion Acrylic Pressure Sensitive Adhesives Design. TAPPI Proceedings. TAPPI Polymers, Laminations and Coatings Conference: Boston, September, 1984; p 469.
Off-Line Monitoring of Butyl Acrylate and Vinyl Acetate Homo-and Copolymerization in Toluene Copolymer Composition Control in Unseeded Emulsion Polymerization Using Calorimetric Data International Standard for Shear Adhesion of Pressure Sensitive Tape
- R Jovanovic
- M A Dubé
- L M Gugliotta
- J R Leiza
- M Arotcarena
- P D Armitage
- J M Asua
- G E P Box
- W G Hunter
- Hunter
Jovanovic, R.; Dubé, M. A. Off-Line Monitoring of Butyl Acrylate and Vinyl Acetate Homo-and Copolymerization in Toluene. J. Appl. Polym. Sci. 2001, 82, 2958. (10) Gugliotta, L. M.; Leiza, J. R.; Arotcarena, M.; Armitage, P. D.; Asua, J. M. Copolymer Composition Control in Unseeded Emulsion Polymerization Using Calorimetric Data. Ind. Eng. Chem. Res. 1995, 34, 3899. (11) International Standard for Shear Adhesion of Pressure Sensitive Tape. In Test Methods for Pressure Sensitive Adhesive Tapes, 13th ed.; Pressure Sensitive Tape Council: Northbrook, 2000. (12) Box, G. E. P.; Hunter, W. G.; Hunter, J. S. Statistics for Experimenters; John Wiley & Sons: New York, 1978. (13) Montgomery, D. C. Designs of Experiments, 5th ed.; John Wiley & Sons: New York, 2000.
Formulation Components. In Emulsion Polymerization and Emulsion Polymers
- A Klein
- E S Daniels
Klein, A.; Daniels, E. S. Formulation Components. In Emulsion Polymerization and Emulsion Polymers; Lovell, P. A., El-Aasser, M. S., Eds.; John Wiley and Sons: Chichester, 1997; pp 207-239.
Characterization of Grafting in the Emulsion Polymerization of Vinyl Acetate Using Poly(vinyl alcohol) as Stabilizer Received for review February 14
- A Klein
Klein, A.; El-Aasser, M. S. Characterization of Grafting in the Emulsion Polymerization of Vinyl Acetate Using Poly(vinyl alcohol) as Stabilizer. J. Appl. Polym. Sci. 2001, 82, 1739. Received for review February 14, 2005 Revised manuscript received June 10, 2005 Accepted June 10, 2005 IE0501778 Ind. Eng. Chem. Res., Vol. 44, No. 17, 2005 6675
- Urban D.