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Mechanical properties of epoxy thermosets depending on the ep/CA ratio.

Mechanical properties of epoxy thermosets depending on the ep/CA ratio.

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Article
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Epoxy resin plays a key role in composite matrices and DGEBA is the major precursor used. With the aim of favouring the use of bio resources, epoxy resins can be prepared from lignin. In particular, diglycidyl ether of isoeugenol derivatives are good candidates for the replacement of DGEBA. This article presents an effective and eco-friendly way to...

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Context 1
... if the epoxide function/CA ratio deviates from the ideal number of reactants, it would decrease the crosslinking density and thus degrades mechanical and thermal properties. Calculated crosslinking density values from DMA data are detailed in Table 3. These values are in accordance with the augmentation of the glass transition temperature and with the decrease of the thermosets swelling ability. ...
Context 2
... can notice the decrease of the loss modulus with the increase of the ep/CA ratio (Table 3). This effect is due to the increasing crosslink density, involving a loss of ability to absorb shock. ...

Citations

... The resulting temperature dependences of storage E and loss E" moduli and mechanical loss tangent tan δ are presented in Figure 4. A peak observed on tan δ curve (Figure 4b) determines the α-transition of the cured epoxy network [26]. It indicates that the glass transition temperatures of the nanocomposite and the neat matrix without nanoparticles (samples N2-5 and V2, Table 1) are equal to 150 and 152 • C, respectively. ...
Article
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Epoxy/silica thermosets with tunable matrix (vitrimers) were prepared by thermal curing of diglycidyl ether of bisphenol A (DGEBA) in the presence of a hardener—4-methylhexahydrophthalic anhydride (MHHPA), a transesterification catalyst—zinc acetylacetonate (ZAA), and 10–15 nm spherical silica nanoparticles. The properties of the resulting material were studied by tensile testing, thermomechanical and dynamic mechanical analysis. It is shown that at room temperature the introduction of 5–10 wt% of silica nanoparticles in the vitrimer matrix strengthens the material leading to the increase of the elastic modulus by 44% and the tensile stress by 25%. Simultaneously, nanoparticles enhance the dimensional stability of the material since they reduce the coefficient of thermal expansion. At the same time, the transesterification catalyst provides the thermoset with the welding ability at heating, when the chain exchange reactions are accelerated. For the first time, it was shown that the silica nanoparticles strengthen welding joints in vitrimers, which is extremely important, since it allows to repeatedly use products made of thermosets and heal defects in them. Such materials hold great promise for use in durable protective coatings, adhesives, sealants and many other applications.
... To enhance attractiveness of diepoxidized isoeugenol as precursor of biosourced epoxy resin the same authors proposed recently [38] an improvement of this previous bio-based epoxy resin in order to make its scale-up possible. Extensive characterization allowed the authors to identify all side-products formed during the first step of the reaction (Scheme 11). ...
... Scheme 11. Formation of monoepoxidized isoeugenol and coproducts during the reaction of glycidylation of isoeugenol [38]. ...
Article
The synthesis of polymers from renewable resources is largely investigated in a context of sustainable development. Polyepoxide networks, widely used in many applications, constitute a major class of thermosetting polymers synthesized from bisphenol A (BPA), a substance identified as chemical estrogen. Moreover, epichlorohydrin used to graft a glycidyl ether group onto BPA to yield diglycidyl ether of BPA (DGEBA) is very toxic. This review proposes to demonstrate that eugenol represents an asset in the development of sustainable epoxy thermosets, by giving a general approach of the researches on the use of eugenol and its isomers for the synthesis of epoxidized precursors. The syntheses of precursors with hetero atoms (nitrogen, phosphorus or silicon) used in specific applications in electrochemistry or as flame-retardants is compared to DGEBA materials.
... Bioplastics are considered a promising solution to concerns related to microplastics because they are environmentally friendly [24][25][26][27]. In this study, polymers containing bio-resources such as isoeugenol were prepared as a way to address pollution problems [28]. ...
Article
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We synthesized a series of renewable and plant-based isoeugenol-substituted polystyrenes (PIEU#, # = 100, 80, 60, 40, and 20, where # is the molar percent content of isoeugenol moiety), using polymer modification reactions to study their liquid crystal (LC) alignment behavior. In general, the LC cells fabricated using polymer film with a higher molar content of isoeugenol side groups showed vertical LC alignment behavior. This alignment behavior was well related to the surface energy value of the polymer layer. For example, vertical alignments were observed when the polar surface energy value of the polymer was smaller than approximately 3.59 mJ/m2, generated by the nonpolar isoeugenol moiety with long and bulky carbon groups. Good alignment stability at 100 °C and under ultraviolet (UV) irradiation of 15 J/cm2 was observed for the LC cells fabricated using PIEU100 as a LC alignment layer. Therefore, renewable isoeugenol-based materials can be used to produce an eco-friendly vertical LC alignment system.
... Tan δ (where δ is the phase lag between stress and strain) is calculated from tan δ = E"/E , where E" is the loss modulus and E is the storage modulus. The crosslinking density, ρ, was calculated using the rubber elasticity theory according to Equation (2) [80,81]: ...
Article
Full-text available
Thermally activated shape memory polymers (SMPs) can memorize a temporary shape at low temperature and return to their permanent shape at higher temperature. These materials can be used for light and compact space deployment mechanisms. The control of transition temperature and thermomechanical properties of epoxy-based SMPs can be done using functionalized polyhedral oligomeric silsesquioxane (POSS) additives, which are also known to improve the durability to atomic oxygen in the space environment. In this study, the influence of varying amounts of two types of POSS added to epoxy-based SMPs on the shape memory effect (SME) were studied. The first type contained amine groups, whereas the second type contained epoxide groups. The curing conditions were defined using differential scanning calorimetry and glass transition temperature (Tg) measurements. Thermomechanical and SME properties were characterized using dynamic mechanical analysis. It was found that SMPs containing amine-based POSS show higher Tg, better shape fixity and faster recovery speed, while SMPs containing epoxide-based POSS have higher crosslinking density and show superior thermomechanical properties above Tg. This work demonstrates how the Tg and SME of SMPs can be controlled by the type and amount of POSS in an epoxy-based SMP nanocomposite for future space applications.
... 18 Because BPA is a known endocrine disruptor, 19 there is also environmental and health reasons to seek safer, more sustainable biobased alternatives. 12,20,21 Due to its widespread use, complete replacement of BPA in the immediate future is an unlikely scenario. Partial replacement of BPA with functionally equivalent alternatives is a more feasible nearer term strategy that could help the polymer industry transition to biobased substitutes. ...
Article
Biobased epoxy thermoset polymers were prepared from lignin hydrogenolysis oils produced from native hardwood lignin. Native lignin in Eucalyptus nitens and Eucalyptus saligna wood was reacted in situ under Pd-catalyzed mild hydrogenolysis conditions to give depolymerized lignin oils in yields up to 98 wt %. Reacting these lignin oils with epichlorohydrin produced biobased epoxy resins. Blending these resins with nonrenewable bisphenol A diglycidyl ether (BADGE) in different proportions, and curing with diethylenetriamine, produced a series of epoxy thermoset polymers with varying biobased content. Up to 67% of the BADGE could be replaced with hardwood lignin-derived epoxy resins while achieving superior or equivalent mechanical properties to the BADGE control polymer. Comparing the performance of lignin-based epoxy polymers from eucalyptus and pine wood provided insights into the advantages and disadvantages of using hardwood versus softwood native lignins in the quest for high performance biobased thermoset polymers.
... How to improve the processability of the system, reduce the melting temperature and viscosity of the system, improve the thermal stability and durability, and Scheme 56. Molecular structures of epoxy monomers, prepolymers, curing agents and flame retardants derived from eugenol (56-1 [233], 56-2 [234], 56-3 [235], 56-4 and 56-5 [236], 56-6 [237], 56-7 [238], 56-8 [239], and 56-9 [240]), vanillin (56-10 [242], 56-11 [243], and 56-12 [244]), phloroglucinol (56-13 [247]), resveratrol (56-14 [250]), magnolol (56-15 [254]), protocatechualdehyde (56-16 [255]), genistein [256], daidzein (56-18 [257]), and salicylaldehyde (56-19 [258]). enhance the toughness requires in-depth research. ...
... But the advances are rapid. Serval interesting research appears in recent months, in particular, the epoxy thermosets and applied materials based on (iso)eugenol [233][234][235][236][237][238][239][240][241], vanillin [242][243][244][245][246], phloroglucinol [247][248][249], resveratrol [250][251][252], cardanol [253], magnolol [254], and more [255][256][257][258][259][260][261][262][263][264][265][266]. These studies are compatible with the general framework described in this review. ...
Article
Recent years have witnessed significant progress in bio-based epoxy thermosets. A variety of epoxy thermosets have been synthesized from various bioresources. In particular, epoxy thermosets derived from bio-based monomeric phenols, either naturally occurring or biotransformed, such as cardanol, eugenol, vanillin, tannin acid, gallic acid, and so forth. This review summarizes research and highlights the molecular transformations and ultimate properties of the resultant epoxy thermosets and materials. The relevant epoxy monomers, prepolymers, curing agents, additives, thermosets, functional materials and biocomposites are discussed based on their molecular structures and properties of crosslinked networks. Finally, the challenges and opportunities in developing sustainable epoxy thermosets and materials from bio-based monomeric phenols are presented.
Article
New developments in thermosets based on bioproducts are gaining significance due to the importance of replacing thermosets and their monomers, traditionally obtained from petrochemical processes, with biobased thermosets prepared from biomass. In the context of new BPA/DGEBA replacements with both enhanced performance and reduced toxicity and the development of innovative biobased thermosetting resins, the conversion of plant biomass, especially natural phenols, into useful polymeric materials is believed to have considerable environmental and economic value. Eugenols are receiving encouraging interest, not only due to their sourcing but also due to their structure and chemical properties, which could enhance the physical characteristics of thermosetting materials, and which could reduce their toxic effects on the environment and human health. The present review mainly focuses on the utilization of eugenol for the synthesis of biobased epoxy and its thermosetting resins, describing synthetic details of new designs for eugenol‐based monomer and/or additive component preparation that are conducive to the formation of eugenol‐containing polymeric materials. Synthetic methods for eugenol‐based monomers are classified according to the principles of green chemistry and are divided into three large groups: single reactions, consecutive reactions, and multicomponent reactions. Outstanding physical characteristics of the formulated eugenol‐based thermosetting epoxy materials are also described. Synthetic details of new designs for eugenol‐based monomer and/or additive component preparation conducive to the formation of eugenol‐containing polymeric materials are explained. Outstanding physical characteristics of the formulated eugenol‐based thermosetting epoxy materials are also described.
Article
A renewable eugenol-based biphenyl bifunctional epoxy monomer (DEUEP) is synthesized via a facile method. Eugenol is coupled into 5,5'-dieugenol and then glycidized to yield DEUEP with a potentially 100% biobased content in high purity (96%). DEUEP displays a lower viscosity (9.2 vs. 20.6 Pa·s at 25 ℃) and flow activation energy (60.4 ± 0.4 vs. 81.1 ± 0.4 kJ/mol) than a commodity bisphenol A-based epoxy prepolymer (E54) does. With a 3,3′-diaminodiphenylsulfone (33DDS) hardener, DEUEP/33DDS is found to express the reactivity identical to E54/33DDS with a similar activation energy (~62 kJ/mol). The cured DEUEP/33DDS thermoset is systematically examined and compared with E54/33DDS in terms of dynamic mechanical properties, thermal stability, flammability, flexural, impact and shear properties, fracture behaviors, water resistance, and wettability. DEUEP/33DDS has a lower flammability as indicated by the increased limited oxygen index (26.4% vs. 22.1%), the decreased heat release rate (HRR), total heat release (THR) and heat capacity (HR) by 46%, 33% and 46%, respectively. DEUEP/33DDS has Tg of 120.9 ℃, storage modulus of 2.57 GPa (25℃), a higher char yield of 32.2% (750 ℃ in N2), and a higher water-contact angle of 110.6o.
Article
There is a growing demand to develop epoxy resins (EP) with smoke suppression as well as satisfactory flame retardancy. Herein, bio‐based cobalt alginate is successfully fabricated and incorporated into EP to prepare EP/Cobalt Alginate composites with better fire safety performance. The addition of cobalt alginate reduces the thermal‐decomposition rate, temperature at maximum weight‐loss rate of EP, whereas obviously improves the thermal stabilities at a higher temperature range. Furthermore, the addition of cobalt alginate substantially reduces the fire hazard of EP, resulting in 56.2% reduction in peak heat release rate, as well as 17.8% and 56.3% reduction in total smoke production and peak smoke production rate, respectively, compared with EP matrix. Moreover, the presence of cobalt alginate increases smoke‐suppressant properties, according to the smoke density test. Additionally, the incorporation of cobalt alginate has no obviously destructive effect on the mechanical properties of EP, while EP/Cobalt Alginate‐3 exhibits a 27.0% improvement in impact strength. In prospective, this study may provide a significant method for producing eco‐friendly flame retardant EP. Bio‐based cobalt alginate is introduced into epoxy resins (EP) matrix to acquire flame retardant EP. The addition of cobalt alginate substantially reduces peak heat release rate, total smoke production, and peak smoke production rate with 56.2%, 17.8%, and 56.3% reduction, respectively. Moreover, the presence of cobalt alginate increases the smoke‐suppressant properties.
Chapter
The importance of bio-based polymers and their derived materials lies in the fact of the great variety of renewable feedstock and the environmentally friendly perspectives of materials. Recent statistics have demonstrated that the efforts to develop bio-based materials (biopolymers) either directly or by producing bio-based monomers promote the future of green products. Current achievements in polymer chemistry and the involvement of biotechnology have impressively accelerated the progress of multifunctional bio-based polymers. This chapter discusses the up-to-date literature review of the most frequently used categories of bio-based sources, their derived monomers, and polymers. The different systems of polymers derived from biomass, their properties, and applications are also part of the chapter. The significance of the discussion is concluded in the last section.