Crosslinked epoxies: Network structure characterization and physical–mechanical properties

Vakil, U. M.; Martin, G. C.

doi:10.1002/app.1992.070461204

Cited by 52 publications

(40 citation statements)

References 19 publications

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“…At small strain level below 10%, as shown in Figure 7a, the stress-strain behaviour of particles appears independent on the crosslinking density, indicating that the reduced E-modulus at small strains are similar for different crosslinked particles. The macroscopic elastic deformation is mainly determined by the elastic properties of the polymer chain [30]; accordingly the effect of different crosslinking density is suppressed. However, as the strain increases over the level of 10%, the effect of crosslinking becomes pronounced.…”

Section: Deformation Process and Fracturementioning

confidence: 99%

Crosslinking effect on the deformation and fracture of monodisperse polystyrene-co-divinylbenzene particles

He¹,

Zhang²,

Kristiansen³

et al. 2013

Express Polym. Lett.

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Abstract. This study focuses on the effect of crosslinking density on the mechanical response of polystyrene-co-divinylbenzene (PS-DVB) particles under compression by means of nanoindentation-based flat punch method combined with SEM observation of particle morphologies. The monodisperse PS-DVB particles with about 5 !m in diameter are produced by the Ugelstad activated swelling method and the crosslinking density defined as the weight percentage of activated crosslinker DVB during the preparation process varies from 2.0 to 55.3%. Results show that the particle stress-strain behaviour is independent of the crosslinking density if the strain is less than 10%. With increasing strain level over 10%, a higher crosslinking leads to a stiffer behaviour of the particles. While slightly crosslinked (2.0 and 5.0 wt%) particles undergo plastic deformation with crazing and residual strain, highly crosslinked (21.3, 32.0 and 55.3 wt%) counterparts experience perfectly viscoelastic deformation. The crosslinking density significantly influences the fracture property as well as the failure morphology. Slightly crosslinked particles become permanently deformed after compression, while highly crosslinked ones are entirely fragmented once a critical strain is reached.

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Section: Deformation Process and Fracturementioning

confidence: 99%

Crosslinking effect on the deformation and fracture of monodisperse polystyrene-co-divinylbenzene particles

He¹,

Zhang²,

Kristiansen³

et al. 2013

Express Polym. Lett.

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“…The correlation between T g and M c can be described in the form of Nielsen's empirical equation [18]: (3) where: T g0 is the glass transition temperature of the uncrosslinked polymer, ξ is a parameter proportional to the molecular weight of the unreacted resin and to the ratio of incremental free volume contributions for the resin and the curing agent [28]. The slope of T g vs. 1/M c curve represents ζ.…”

Section: Correlation Between T G and M Cmentioning

confidence: 99%

“…Nevertheless, determining the role that a network architecture plays on the thermal and mechanical behaviour of thermoset systems, especially epoxy ones, is complicated by the wide variety of crosslinking agents and epoxy resins available. For that reason in the majority of such studies on epoxy systems, the molecular weight between crosslinks (M c ) is the only network variable controlled [3,16,24,28]. This parameter is related to the crosslink density and can be varied by changing the stoichiometric ratio and the degree of cure [21,24] since while curing the chemical reaction between resin and the curing agent develops three dimensional crosslinked polymeric chains.…”

Section: Introductionmentioning

confidence: 99%

Effect of Molecular Weight on the Yield Behaviour of Epy Epoxy Compound

Urbaniak¹

2016

Adv. Sci. Technol. Res. J.

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A series of epoxy networks with molecular weight between crosslinks (M c ) ranging from 117 to 508 g/mol were investigated by employing as DSC and DMA methods and compression testing over a broad range of test temperatures (from 20 to 120°C) and strain rates (from 0.0208 to 20.8 min -1 ). Mechanical characteristics vs. testing temperature and strain rate developed in relation to working conditions of EPY compound applied for machine foundation chocks as well as effect of crosslinking on glass transition temperature (T g ) presented in this paper let to find out the effect of molecular architecture composed chiefly by M c on the thermal and mechanical properties that govern yield behaviour of the material. The investigations carried out in a.m. ranges of testing temperatures and strain rates showed that whichever change of M c is related to the change in crosslink density causing relative shift in the T g of the compound. However, a sensitivity of the polymer material on changes in strain rate falls down with growth of testing temperature. Obtained results prove that yielding in EPY compound can be examined in categories of the Eyring's plastic flow model in which yielding is described.

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“…Desta maneira é possível o entendimento da relação estrutura-propriedades destes materiais. Numerosos trabalhos têm sido publicados nas últimas décadas em relação a este tópico, especialmente para o caso de redes diepóxi-diaminas [1][2][3][4][5][6][7][8] .A importância do estudo de juntas adesivas, assim como a tecnologia da estrutura das uniões tem sido incrementado, devido a numerosas vantagens do emprego das juntas adesivas em relação à utilização de outros métodos para a união de materiais [9][10] . Para obter estruturas resistentes usando juntas adesivas, é importante o estudo do efeito da natureza do adesivo e do substrato, características tais como a rugosidade do substrato e a geometria das uniões [11] .…”

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Influência da estrutura química do co-monômero nas propriedades termomecânicas e durabilidade de uniões adesivas submetidas à ação da água

2011

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Resumo: A caracterização termomecânica, assim como a durabilidade de juntas adesivas usando diferentes polímeros epoxídicos no estado vítreo foram analisadas. Os polímeros foram baseados no prepolímero do éter diglicidílico do bisfenol A (DGEBA) curado com diferentes aminas alifáticas. Análises termomecânicas no modo de torção foram realizadas para monitorar o fator de perda (tan δ), o módulo de armazenamento (G'), e o módulo de perda (G") em função da temperatura. Os ensaios de adesão foram realizados em uniões de simples sobreposição usando substrato de aço quando submetidas à ação da água a temperatura ambiente, e a 80 °C, com o objetivo de avaliar a durabilidade das juntas adesivas a diferentes temperaturas. As análises termomecânicas evidenciaram diferenças significativas nos valores de tan δ, G' e G" em função da temperatura para as redes estudadas. As melhores propriedades adesivas são obtidas para uniões polímero-substrato que usam polímeros que apresentem estrutura de rede mais flexível. A durabilidade das juntas adesivas quando submetidas à ação da água causa menor prejuízo à formulação com piperidina. Este comportamento foi associado à baixa tendência de absorver água deste polímero, devido à homopolimerização dos grupos epóxi, que originam uma estrutura de rede com baixa concentração de grupos hidroxila. Palavras-chave: Polímeros epoxídicos, uniões adesivas, caracterização termomecânica, durabilidade. Influence of Chemical Structure of Co-monomer on Thermomechanical and Durability of Adhesive Joints to the Action of the WaterAbstract: The thermomechanical properties, as well as the durability of adhesive joints using different epoxy polymer in the vitreous state was analyzed. The epoxy polymers based on diglycidyl ether of bisphenol A (DGEBA) cured with various aliphatic amines. Rheological tests were used to determine damping (tan δ = G"/G'). The adhesion tests were carried out in steel joints using single lap shear when submit to the action of the water, at ambient temperature and at 80 °C, with the objective of evaluating the durability of the adhesive joints at different temperature. The best adhesive properties were obtained when exists high flexibility of chain between crosslink. The durability of the adhesive joints, when submitted to the action of the water cause smaller damage in the resistance adhesive to the polymer with piperidine. This behavior was associated to the low tendency of absorbing water of this polymer, due to the homopolimerization of the epoxy groups, what origin a network with low concentration of hydroxyl groups. Keywords: Epoxy polymer, adhesive joint, thermomechanical characterizations, durability. IntroduçãoOs polímeros epoxídicos constituem uma das mais importantes classes de polímeros termorrígidos utilizados em adesivos, matrizes para compósitos reforçados, recobrimentos e encapsulados. Para obter alto desempenho usando estes materiais é necessário tanto do ponto de vista do controle do processo de sínteses quanto do processamento, especialmente quando se deseja obte...

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Crosslinked epoxies: Network structure characterization and physical–mechanical properties

Cited by 52 publications

References 19 publications

Crosslinking effect on the deformation and fracture of monodisperse polystyrene-co-divinylbenzene particles

Crosslinking effect on the deformation and fracture of monodisperse polystyrene-co-divinylbenzene particles

Effect of Molecular Weight on the Yield Behaviour of Epy Epoxy Compound

Influência da estrutura química do co-monômero nas propriedades termomecânicas e durabilidade de uniões adesivas submetidas à ação da água

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