Effect of the molecular weights of raw epoxy resins on the physical properties of cured epoxy resins.

Ogata, Masatsugu; Kinjo, Noriyuki; Eguchi, S.; Kawata, Tatuo; Urano, Takasi

doi:10.1295/koron.47.639

Cited by 8 publications

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“…Many studies have been made on the relation between cross-linking density and physical properties for epoxy resins cured with various amine or acid anhydride hardeners, and it has been reported that similar relationships were observed for these epoxy resins.6-8J3- 27 We concluded in a previous paper [17][18][19][20] that the cross-linking density is the most dominant factor that determines the various physical properties of cured neat epoxy resins. The results show that there are relationships, given in Table V, between cross-linking density and physical properties of the cured resin; i.e., when the cross-linking density increases, the glass transition temperature also increases while the thermal expansion coefficient (TEC) in the rubbery region and elasticity in the glassy region decrease.…”

Section: As Shown Inmentioning

confidence: 85%

Effects of curing accelerators on physical properties of epoxy molding compound (EMC)

Ogata

Kinjo

Eguchi

et al. 1992

J of Applied Polymer Sci

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SYNOPSISThe effects of various curing accelerators on the physical properties of epoxy molding compounds (EMCs) were investigated. Such properties as elasticities in rubbery and glassy regions, glass transition temperature, thermal expansion coefficient, and water absorption at 60°C of neat epoxy resins using various curing accelerators were found to be directly reflected in the properties of the EMCs that were prepared by using each resin system. However, volume resistivity and saturated water absorption at 120°C were not reflected. This was attributed to differences in the catalytic reactivity of accelerators causing different melt viscosity for the EMC, which resulted in different densities (packing degrees) and affected physical properties of molded EMC. On the other hand, it was found that the density of molded EMC was also affected by the molding conditions. To improve the physical properties of the molded EMC, in addition to proper selection of accelerators, it was very important to set the melt viscosity of the EMC as high as possible within the moldable range and to select suitable molding conditions.

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Section: As Shown Inmentioning

confidence: 85%

Effects of curing accelerators on physical properties of epoxy molding compound (EMC)

Ogata

Kinjo

Eguchi

et al. 1992

J of Applied Polymer Sci

Self Cite

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“…[5][6][7] Free volume measurement vs chemical conversion shows that the maximum in the isothermal density or modulus occurs approximately in the same location as the minimum found in the free volume. 8 The maximum found in density and modulus has a significant implication on all other physical properties, such as water absorption, 5 diffusion coefficient, 9 gas permeability, 9 thermal expansion coefficient, 10 and the physical aging rate. 11 Of most importance is that the same phenomenon has been observed in other systems, such as polycynurates 12,13 and phenolic resins.…”

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confidence: 99%

Effects of Gelation in the Glassy State

Wang

Foltz

2001

Macromolecules

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Effects of crosslinking on physical properties of phenol–formaldehyde novolac cured epoxy resins

Ogata

Kinjo

Kawata

1993

J of Applied Polymer Sci

129

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SYNOPSISTo clarify the relationship between crosslinking density and physical properties of phenolformaldehyde novolac cured epoxy resin and factors governing their physical properties, we studied various properties of cured resins having different crosslinking densities. The resins were prepared with various curing accelerators and raw epoxy resins having different molecular weights. We found that as the crosslinking density of a cured resin increases, glass transition temperature ( Tg) rises and the relaxation time becomes longer. Furthermore, in the rubbery region, the coefficient of linear thermal expansion drops and the elastic modulus become larger, while, in the glassy region, the coefficient of linear thermal expansion, specific volume, water absorption, diffusion coefficient, and permeability all increase but the elastic modulus becomes smaller. The WLF analysis on the relaxation behaviors of typical cured resin showed that cured resin with a higher crosslinking density decreases in the fractional free volume. This behavior is completely opposite from the relationship predicted from the temperature dependency of specific volume. While the coefficient of thermal expansion of free volume decreases as the crosslinking density increases for the cured resin, it coincides well with the tendency predicted from the difference in coefficient of cubic thermal expansion in the rubbery and glassy regions of each cured resin. That the free volume obtained from WLF analysis shows a relationship opposite to the predicted free volume as based on the temperature dependency of specific volume is explained as follows: Namely, the free volume obtained from the WLF analysis is a hole free volume V , which contributes to fluidity and v h decreases with the crosslinking density. On the other hand, the free volume predicted from the specific volume is a sum of the interstitial free volume Vi and v h . V, increases with the crosslinking density and this Vi increase exceeds the decrease of v h . Therefore, the free volume predicted from the specific volume increases with the crosslinking density. Consequently, the influence of free volume on the relationship between the crosslinking density and physical properties of cured resin can be interpreted as follows. As the crosslinking density increases on cured resins, Tg rises, the relaxation time is lengthened, and the coefficient of linear thermal expansion becomes smaller in the rubbery region because, as the crosslinking density increases, v h decreases. Since crosslinking density increases on cured resins, the coefficient of linear thermal expansion, water absorption, diffusion coefficient, and permeability become larger, and the elastic modulus becomes smaller in the glassy region because, as the crosslinking density increases, Vi increases and, accordingly, molecular chain packing becomes looser; i.e., the specific volume increases. 0 1993 John Wiley & Sons, Inc.

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Effect of the molecular weights of raw epoxy resins on the physical properties of cured epoxy resins.

Cited by 8 publications

References 0 publications

Effects of curing accelerators on physical properties of epoxy molding compound (EMC)

Effects of curing accelerators on physical properties of epoxy molding compound (EMC)

Effects of Gelation in the Glassy State

Effects of crosslinking on physical properties of phenol–formaldehyde novolac cured epoxy resins

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