No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Properties of solvent based polyurethane adhesives containing fumed silicas
Abstract
Five hydrophilic and two hydrophobic fumed silicas of different surface area and particle size were added to solvent based polyurethane adhesives. Silica addition produced a noticeable increase in the adhesive viscosity, imparted negative thixotropy, increased the storage modulus (G') and improved the green adhesion of chlorinated rubber/PU adhesive/chlorinated rubber joints. Those modifications were more pronounced in the adhesives which contain hydrophilic silicas.
... Currently, polyurethane composites have been widely promoted and utilized, and high-performance composite polymer materials have demonstrated excellent thermal stability, electrical conductivity, and high strength. In terms of the above properties, polymer composites present great development potential in many aspects [1][2][3][4][5]. e domestic and overseas research mainly focus on adding carbon fiber into composite materials [6][7][8][9][10][11][12]. ...
Polymer grouting is carried out between the steel panel and surrounding soil in underground engineering, and the polymer material consists of isocyanates and polyols. The isocyanate/polyol composite slurry expands rapidly due to chemical reaction and solidifies immediately. Then, a dense impermeable polymer layer is formed after rapid expansion of isocyanate and polyol, which is widely used for ground reinforcement and foundation remediation. Thus, a steel panel-polymer composite structure is developed. Mechanical properties of the steel panel-polymer structure are studied. The results show that the steel panel-polymer structure exhibited excellent mechanical properties. The steel panel and polymer layer should be designed above 3 mm and 10 mm in thickness, respectively. The steel panel showed superior mechanical properties to those of polymer layers. Considering good rigidity of the steel panel and good flexibility of the polymer layer, the steel panel and polymer layer presented perfect interfacial contact. It is concluded that the mechanical properties of the whole structure were increasingly enhanced with the increase of the steel panel thickness and the structural flexibility increased with the thickness of the polymer layer. Besides, the combination of the steel panel and polymer layer could also improve the mechanical properties of this coupling structure. This study provided an initial attempt for investigating the feasibility of applying polyurethane foam to steel panels in underground engineering. The stress analysis along the grouting direction inside the prefabricated wall was conducted. It may lay the foundation for further application of polymer grouting in underground engineering.
... Solvent based adhesives use volatile organic compounds as solvents, such as benzene and toluene. These solvents will directly volatilize to pollute the environment and harm the health of human body [15][16][17][18][19] . For the environmental protection our soil consolidation agent should not pollute the soil and groundwater and neither impair normal growth of the seedlings. ...
Transplanting trees with rhizospheric soil is an important way to facilitate tree survival in the process of landscaping and reforestation. Traditional way to prevent looseness of rhizospheric soil is forming soil balls around the roots with bags, boxes or rope wrapping, which is cumbersome, laborious and easy to break. This study is aimed to develop a new type of degradable environment-friendly polymer as soil consolidation agent to facilitate tree transplanting. In this paper, the KGM/CA/PVA ternary blending soil consolidation agent was prepared by using Konjac glucomannan (KGM), chitosan (CA) and polyvinyl alcohol (PVA) as raw materials. Through the verification and evaluation, the clay and sandy soil can be consolidated and formed into soil balls by the ternary blend adhesive, which was convenient for transportation. The preliminary application of the ternary blend adhesive in the transplanting process of sierra salvia, Japanese Spindle ( Euonymus japonicus ) and Juniperus sabina ‘Tamaricifolia’ confirmed that the application of soil consolidation agent can effectively solve the problem that the root ball of seedling is easily broken in the process of transplant. And the application of soil consolidation agent has no adverse effect on the growth of transplanted seedlings. The research and development of ternary blending soil consolidation agent and its preliminary application in seedling transplanting will provide a new solution to solve the problem of soil ball breakage in the process of seedling transplanting. This is an important stage in the development of new seedling transplanting technology. Therefore, the research and development of soil consolidation agent is of great significance.
... SiO 2 , TiO 2 , ZnO and Al 2 O 3 into waterborne polyurethanes is one of several methods widely used to improve their thermal stability, mechanical and physical properties. Fumed silicas are often used with polyurethane adhesives to improve their physico-mechanical properties [2]. Silica nanoparticles offer potential for waterborne polyurethane reinforcement, because silanol groups on the surface of nanosilica might interact with the hard and/or soft segments of polyurethane thus supporting dispersion of the nanosilica in the polyurethane backbone [3]. ...
Castor oil polyols (COLs) have been synthesized from glycolyzed oligoester polyol in order to produce waterborne polyurethane (WPU)/silica hybrid dispersions. Soft drinks poly(ethylene terephthalate) (PET) bottles were depolymerized by glycolysis with different molar ratio of poly(ethylene glycol) ( PEG 400), in the presence of zinc acetate as catalyst. The obtained glycolyzed products were reacted with castor oil (CO) to attain castor oil polyols by the process of transesterification. Five castor oil polyols were used with hydroxyl values of 255, 275, 326, 366 and 426 mg KOH g−1. Several castor oil-based, polyurethane/silica hybrid dispersions having soft segment content of 39.6% to 28.2% and two concentrations of SiO2 nanoparticles (0.5 and 1.0) have been prepared.
Reiner [1] defines rheology as a science that treats body deformation and flow. Founders of modern rheology consider deformation of mainly solid bodies, regarding them as homogeneous continuous media. The present study focuses on the rheological behaviour of filled polymers, where the filler affects not only material exploitation characteristics, but essentially determines its fabrication into a final product. A combination of the characteristics of the dispersed medium with those of the filler-formed structure is the basis of the rheology of filled polymers. Those systems may display different properties, depending on medium viscosity and strength of the structure skeleton of the filler. Modern rheology is dominated by two main problems; Malkin [2] defines them as follows:
The first goal of rheology is to search for stress-deformation relationships for various technological and engineering materials in order to solve macroscopic problems related to continuum mechanics of these materials;
The second problem consists in the establishment of relations between rheological properties of a material and its molecular composition. This goal is specific for microrheology, a trend founded by Reiner.
This chapter constitutes one of the very few reviews in the existing literature on shoe bonding, and it gives an updated overview of the upper to sole bonding by means of adhesives. The surface preparation of rubber soles and both the formulations of polyurethane and polychloroprene adhesives are described in more detail. The preparation of adhesive joints and adhesion tests are also revised. Finally, the most recent development and technology in shoe bonding is described.
Different mixtures of thermoplastic polyurethane (PU) with different amounts of nanometric carbon black (CB) were prepared by mechanical stirring in organic solvent, and their thermal, rheological, viscoelastic and mechanical properties were investigated. The rheology of the PU-CB mixtures in methyl ethyl ketone was optimized, allowing good dispersion of the CB in the polyurethane matrix once the solvent was removed; an increase in the number and size of carbon black aggregates in the polyurethane matrix was obtained by increasing the carbon black loading. Addition of carbon black improved the rheological and viscoelastic properties of the polyurethane, and the larger was the carbon black content, the higher was the storage modulus and the lower was the tanδ value. Moreover, the addition of higher amounts of CB changed the viscoelastic behaviour of the polyurethane, which became mainly elastic over all temperature range. On the other hand, the addition of CB loadings up to 12 wt% increased the thermal stability of the polyurethanes and increased the elongation-at-break without noticeable reduction in the tensile strength.
Three elastomeric polyurethanes were obtained by reacting MDI (diphenylmethane-4,4′-diisocyanate) with ϵ-caprolactone macroglycols of different molecular weight (1000–3000 daltons); the chain extender used was 1,4-butane diol. The increase in the molecular weight of the macroglycol modified the degree of phase separation and the interactions between the hard and soft domains in the polyurethane structure. The properties of elastomeric polyurethanes were studied by using Gas Permeation Chromatography, FTIR spectroscopy, DSC, DMTA, rheology (stress-controlled rheometer), contact angle measurements, and T-peel strength tests. The use of low molecular weight macroglycol produced polyurethane with small crystallinity, relatively higher Tg and reduced softening enthalpy. Therefore a poor degree of phase separation was produced and reduced mechanical and viscoelastic properties were obtained. On the other hand, a high molecular weight macroglycol improved the degree of phase separation producing better mechanical, viscoelastic and thermal properties in the polyurethanes. Furthermore, the increase in molecular weight of macroglycol increased the adhesion of PVC/polyurethane adhesive joints and further changed the locus of failure.
Fumed silicas of different specific surface area (90-380 m/g) were added to a thermoplastic polyurethane (PU) solution. After solvent removal, solid fumed silica-PU composites were obtained. The viscoelastic properties of PU were improved by adding fumed silica and only a solid-like behavior in PU-fumed silica composites was obtained. The increase in the specific surface area of the fumed silica up to 200 m / g increased the moduli of the composites. Fumed silica-PU interactions were responsible for the improved rheological properties of the composites. The activation energies for viscous flow of the composites were 14-16 kcal/mol and increased as the specific surface area of fumed silica increased. The glass transition temperature (obtained from DMTA and DSC experiments) and the crystallization rate of fumed silica-PU composites decreased compared with PU and also decreased with increasing surface area of the fumed silica. The contact angle values were similar in all the composites and the strength of PVC/fumed silica-PU composite joints was not affected by the specific surface area of the fumed silica.
Natural ultramicronized calcium carbonate and mixtures of fumed silica + natural ultramicronized calcium carbonate are proposed as a filler for solvent-based polyurethane (PU) adhesives. The PU adhesive containing only calcium carbonate showed similar thermal, mechanical, surface, and adhesion properties to those of the PU adhesive without a filler. The addition of 90 wt% fumed silica + 10 wt% calcium carbonate mixture to the PU adhesive produced a performance similar to or improved over that of the PU adhesive containing only fumed silica. The increase in the amount of natural calcium carbonate with respect to fumed silica in the filler mixture had a detrimental effect on the rheological and mechanical properties of the PU adhesives, although the surface and final adhesion properties were not noticeably modified. The immediate adhesion (45 min after joint formation) was noticeably increased in the joints produced with the PU adhesives containing fillers, mainly in those with a higher fumed silica content; a cohesive failure in the adhesive was produced in those joints and the mechanical and rheological properties of the PU adhesives determined the immediate adhesion. The failure in the joints peeled 72 h after joint formation was adhesional and the adhesion properties were mainly determined by the surface properties of the PU adhesives. All the adhesive joints showed a similar final adhesion because they have similar surface properties.
Fumed silica is a well-known mineral filler of epoxy and polyurethane adhesives. Although effective, the small particle size and the relative high cost of fumed silicas suggest the need for an alternative filler. In this study, the usefulness of adding a natural hydrated magnesium silicate (sepiolite) as a new filler in solvent-based polyurethane (PU) adhesive formulations has been demonstrated. The rheological and adhesion performance of the sepiolite-filled PU adhesive was compared with that in PU adhesives containing fumed silicas. The addition of a filler to PU adhesives provided an increase in viscosity, imparted thixotropy and pseudoplasticity to the adhesive solution, produced an increase in storage and loss moduli, and improved the rheology of the PU. The mechanical properties of adhesive films were increased by adding filler, mainly with fumed silica. On the other hand, the immediate T-peel strength of roughened or (roughened + chlorinated) styrene-butadiene rubber/PU adhesive joints was greatly improved in filled PU adhesives. The effects produced by adding sepiolite or fumed silica to the adhesives were very similar, although in general more noticeable in fumed silica filled PU due to the formation of hydrogen bonds between the filler and the solvent and/or the polyurethane (in sepiolite-filled adhesives, van der Waals forces seemed to be responsible for the interactions between the filler and the solvent and/or polyurethane).
Two hydrophilic and two hydrophobic fumed silicas of different characteristics were added to solvent-based polyurethane adhesives (PU). IR spectroscopy, contact angle measurements and rheology (viscosity measurements, determination of viscoelastic properties) were used to monitor the variation of properties of PU adhesives produced by addition of silica. Immediate (green) adhesion was determined by T-peel testing of halogenated synthetic rubber/PU adhesive/halogenated synthetic rubber joints. Silica addition produced a noticeable increase in the PU adhesive viscosity which can be related to the variation of viscoelastic properties. Viscosity of PU adhesives containing hydrophilic silica slightly increased with time after preparation; the increase was less significant in PU adhesives with hydrophilic silica. In the rheological studies, silica imparted shear thinning and negative thixotropy to PU adhesives due to a better dispersion of the silica in the polyurethane during shearing. The addition of silica produces an increase in the storage modulus (G') of PU adhesives, the values obtained being independent of the hydrophilic or hydrophobic nature of the fumed silica. The increase of G' and the changes in tan δ of PU adhesives containing silica corresponded to an improvement in the green adhesion properties of chlorinated rubber/PU adhesive/chlorinated rubber joints. In general, in disagreement with previous results, the presence of silica did affect the properties of solvent-based PU adhesives, but these properties were not dependent on the type of silica (hydrophobic or hydrophilic) used in this study.
The influence of the addition of silica (Aerosil-200) (5-25 wt%) to polyurethane adhesives on their adhesion properties with non-chlorinated and surface-chlorinated rubbers has been studied. The chlorinating agent was Trichloroisocyanuric acid (TIC) in 2-butanone solution at a concentration of between 1 and 9 wt%. In general, silica produced an increase in the adhesive viscosity and an improvement of green (immediate) peel strength (especially with chlorinated rubber). The best results were obtained for a silica content of 10-20 wt%. However, the addition of silica did not improve the peel strength after a thermal ageing process. Polyurethane adhesives containing silica undergo an improvement in their resistance to degradation by chlorine on the rubber surface. On the other hand, the chlorination of silica produces the rupture of Si-O bonds and the formation of Si-H and Si-Cl groups. Furthermore, the stirring speed (directly related to the dispersion) of silica into the adhesive is an important parameter which affects the viscosity and peel strength. A stirring speed of 1000 rpm gives the best silica dispersion.
A method for measuring the surface energy of solids and for resolving the surface energy into contributions from dispersion and dipole-hydrogen bonding forces has been developed. It is based on the measurement of contact angles with water and methylene iodide. Good agreement has been obtained with the more laborious γc method. Evidence for a finite value of liquid-solid interfacial tension at zero contact angle is presented. The method is especially applicable to the surface characterization of polymers.
DEGUSSA. Technical Bulletin Pigments no. 23
- M. Ettlinger
- H. Ferch
- J. Mathias
DEGUSSA. Technical Bulletin Pigments no. 11
- R. Bode
- H. Ferch
- H. Fratzscher