This article reviews the progress in the development of wood biomass origin epoxy resin system from 1960s to recent years in Japan. The methods of using wood biomass for epoxy resin systems are classified into the following three categories; one is the method of preparing lignin‐epoxy resins after applying treatments on the industrial lignin, which has been disposed in large volume, another is that of using wood as the raw material of epoxy resin system after applying treatments directly on wood, and the other is that of composing epoxy resin and/or curing agent from woody raw materials (except the industrial lignin), which are isolated and refined from wood before the treatments. Although several promising technologies have been developed and tried to be industrialized in Japan, the full‐fledged development of wood biomass‐based epoxy resin has just started when viewed as a whole. These developments will be further accelerated toward the construction of the environment harmony type and the resources circulation type societies. As the result of continuous developmental efforts, it is expected that we can look at the scene where epoxy resins are sustainably supplied in various forms even after the depletion of oil resources. POLYM. ENG. SCI.,, 2012. © 2012 Society of Plastics Engineers

SYNOPSISDielectric properties above the glass transition have been investigated for a series of bisphenol-A type epoxide prepolymers (388 5 M, I 2640). Dielectric measurements were performed over a frequency range of 50 Hz-1 MHz using a vertical parallel plate cell which was constructed in the laboratory. The dielectric a-relaxation for each prepolymer fits the empirical model of the Havriliak-Negami equation. The temperature dependence of the dielectric relaxation time 7 is described by the Williams-Landel-Ferry ( WLF ) equation as well as that of the direct current conductivity cr, which can be measured using the same cell. The relationship between 7 and cr, cr -7 m = const, is derived from experimental results.The exponent m , which depends on the molecular weight of the prepolymer, is considered to correspond to the ratio of the segmental mobility to ionic mobility. The dielectric loss 6'' can be used as an indicator of the direct current conduction in the temperatures where the ionic component in 6'' becomes much larger than the dipole one.

ABSTRACT:The free volume of a bisphenol-A-type epoxide oligomer (DGEBA) was studied using Williams-Landel-Ferry parameters and thermal expansion coefficients above and below the glass transition temperature (T g ). The values of the free-volume fraction at the T g are around 0.02 for the DGEBA oligomers having weight-average molecular weights (M w 's) from 1396 to 2640. The dipole mobility, which was obtained from the analysis of the temperature dependence of the dielectric relaxation time, was compared with the segment mobility in terms of the critical volume for the transport of each moving unit. The critical volume for the segment transport increases with increase of the M w of the oligomer. The critical volume for the dipole movement, on the other hand, is not different between the oligomers studied (1396 Յ M w Յ 2640), which leads to that the dipole mobility in the epoxide oligomer is smaller than is the segment mobility. The low mobility of the dipole is considered to result from the molecular interaction restricting the dipole movement, especially in a smaller M w oligomer.

SYNOPSISMelt viscosity has been investigated for a series of bisphenol-A type epoxide oligomers with different weight-average mol w t s (A&,), ranging from 388 to 2640. The temperature dependence of the melt viscosity is described by the Williams-Landel-Ferry ( WLF ) equation. The melt viscosity q is correlated with both the direct current (dc) conductivity u and the dielectric relaxation time 7. The two relationships between these three properties, o.q* = const (0.63 5 K 5 1.12) and q /~~ = const (0.73 d C 5 1.06), are experimentally derived. Both exponents, K and C, depend on the M u of the oligomer. The lower &fw oligomer has the larger value of K . The K value is close to unity for the low Mw oligomer, which agrees with Walden's rule, u -77 = const, applicable to most low mol wt liquids. The C value is near unity for the epoxide oligomer with higher Mu than 2000, which means that the melt viscosity is proportional to the dielectric relaxation time. The low oligomer (au < 2000), on the other hand, has a smaller value of C below unity. The result indicates that the melt viscosity is not proportional to the dielectric relaxation time for the low Mw epoxide oligomer, whose dielectric a-relaxation is not governed by the Debye equation.

SYNOPSISThe isothermal curing behavior of an epoxy resin system has been monitored by a dielectric measurement whose sensor consisted of a vertical parallel-plate cell based on a threeterminal method. The materials used in the isothermal cure were the diglycidyl ether of bisphenol-A (DGEBA), which was purified from Epon 825 by recrystallization, and 4,4'-diamino diphenyl methane (DDM). A dielectric relaxation was observed during each isothermal cure at temperatures of 70,80,90, and 100°C, which were below the glass transition temperature ( T,) of the reactive DGEBA-DDM system at the gel point. The relaxation is considered to be caused by the transformation from a liquid state to an ungelled glassy state as a result of an increase in molecular weight because gelation followed by a rubbery state did not exist in the temperature range studied. The dielectric relaxation for the DGEBA-DDM system fits the empirical model of the Havriliak-Negami equation. The Tg of the DGEBA-DDM system, which was estimated from the dielectric relaxation time, agreed with the one experimentally determined by differential scanning calorimetry (DSC) .