Crosslink density and fracture toughness of epoxy resins

Levita, G.; Petris, S. De; Marchetti, A.; Lazzeri, Andrea

doi:10.1007/bf01130180

Cited by 235 publications

(205 citation statements)

References 14 publications

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“…This type of morphology was previously observed by us in materials obtained with 1-methylimidazole, which cured very fast as is also the case here [30]. The T g measured for this thermoset does not indicate plasticization, related to ductility, that dictate its toughness characteristics [31]. However, the rougher surface appearance observed in the fractographs containing HBP-OH blends, suggests that the impact specimens experienced more plastic deformation during fracture in comparison with the unmodified epoxy network.…”

Section: Mechanical and Morphological Characterizationsupporting

confidence: 49%

Influence of end groups in hyperbranched polyesters used as modifiers in the characteristics of epoxy thermosets cured by adipic dihydrazide

Tomuta¹,

Ramis²,

Flor³

et al. 2013

Express Polym. Lett.

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Abstract. Mixtures of diglycidylether of bisphenol A (DGEBA) resin and different ratios of aliphatic-aromatic hyperbranched polyester (HBP) were cured by a latent curing agent, adipic dihydrazide (AH). The HBPs prepared have hydroxyl groups or 10-undecenoyl or allyl groups as chain ends. The curing mixtures were investigated by differential scanning calorimetry (DSC) to study the curing process and to evaluate the kinetic parameters of the different formulations. These studies suggest that HBPs decrease the curing rate of epoxy/AH in the case of vinyl terminated HPB, whereas OH terminated HBP accelerates the first stages and delays the lasts. The thermosets obtained showed an improvement in microhardness and impact strength without any reduction of the T g and thermal parameters. Microparticle phase separation was observed with the undecenoyl HBP derivatives or when a 10% of allyl HBP derivative was in the formulation.

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Section: Mechanical and Morphological Characterizationsupporting

confidence: 49%

Influence of end groups in hyperbranched polyesters used as modifiers in the characteristics of epoxy thermosets cured by adipic dihydrazide

Tomuta¹,

Ramis²,

Flor³

et al. 2013

Express Polym. Lett.

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“…Varying the molecular weight between cross-links has been linked to toughening in both mode I fracture and impact resistance. [28][29][30][31] However, the use of high-molecular-weight epoxy resins with low epoxide functionality presents challenges in processing as increasing the molecular weight before curing results in solid epoxy resins that requires high processing temperatures or the use of organic solvents. Additionally, increasing the molecular weight between cross-links can dramatically reduce the glass transition temperatures of the resulting thermosets, limiting their use in high-performance applications.…”

Section: Introductionmentioning

confidence: 99%

Bio-based epoxy resin toughening with cashew nut shell liquid-derived resin

Maiorana

Ren

et al. 2015

Green Materials

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IntroductionEpoxy resins are building blocks used to form a versatile class of thermoset polymers. They can be cured under a wide range of conditions and exist as solids or liquids at room temperature. Liquid epoxy resins are ideal for manufacturing large one-piece structural composites such as wind turbine blades and car frames.1 Higherviscosity liquid epoxy resins also find uses as structural adhesives for wind turbine blades, car frames and electronics. Aside from composites, liquid and solid epoxy resins also find a wide variety of uses as protective coatings due to their anticorrosive nature and good adhesion to metal substrates.2 Epoxy resins can be designed such that after curing they result in thermosets with high modulus and glass transition temperatures. However, these thermosets may possess low impact resistance and brittle fracture. Bisphenol A (BPA) and, subsequently, the diglycidyl ether of bisphenol A (DGEBA), is currently used for the preparation of a versatile family of high-performance cured epoxy resins.

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“…Different factors may influence the curing process, such as the temperature profile, time, epoxy/hardener ratio, and additives. [6,7] DSC is a technique commonly used to characterize the cure kinetics based on heat evolution and activation energies. Conversion studies resulting from isothermal and dynamic DSC experiments can quantitatively define the formation of the epoxy network.…”

Section: Communicationmentioning

confidence: 99%

Epoxy/Silica Nanocomposites: Nanoparticle‐Induced Cure Kinetics and Microstructure

Rosso

2007

Macromol. Rapid Commun.

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This study reveals the influence of silica nanoparticles on the cure reactions of a diglycidyl ether of bisphenol A epoxy resin. As soon as the silica nanoparticles are added to the neat resin (1, 3, and 5 vol.‐%), the total degree of conversion increases with an increasing amount of nanoparticles, and the cure reaction shows a more complex autocatalytic behaviour, which can not be described by a traditional kinetic model. Results from subsequent thermo‐mechanical analyses confirm an alteration in the microstructure attributable only to the presence of the nanoparticles in the curing stage. An amino‐rich interphase around the reactive treated particles is formed, which shifts the resin/hardener ratio, and benefits the homopolymerization of the epoxy and leads to a more highly crosslinked epoxy network. At the same time, the nanophase consists of a core‐shell structure with the rigid particle inside and a rubber‐like shell because of the excess hardener in this region.TEM image of two neighboring silica nanoparticles in the epoxy matrix showing a 2–3 nm altered interphase region.magnified imageTEM image of two neighboring silica nanoparticles in the epoxy matrix showing a 2–3 nm altered interphase region.

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Crosslink density and fracture toughness of epoxy resins

Cited by 235 publications

References 14 publications

Influence of end groups in hyperbranched polyesters used as modifiers in the characteristics of epoxy thermosets cured by adipic dihydrazide

Influence of end groups in hyperbranched polyesters used as modifiers in the characteristics of epoxy thermosets cured by adipic dihydrazide

Bio-based epoxy resin toughening with cashew nut shell liquid-derived resin

Epoxy/Silica Nanocomposites: Nanoparticle‐Induced Cure Kinetics and Microstructure

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