电子束辐射固化环氧树脂的动态力学分析——树脂化学结构、分子量及其分布的影响

应用不同化学结构、分子量及其分布的环氧树脂进行了电子束辐射固化实验 ,对固化物进行了动态力学分析 ,研究了不同样品凝胶含量、内耗tanδ及动态模量的变化规律 .分析结果表明环氧树脂辐射反应活性与其化学结构有很大关系 ,酚醛型环氧树脂的辐射反应活性高 ,固化后高温模量及玻璃化温度较高 ,而脂环族环氧树脂反应活性小 .在低辐射剂量下 ,环氧树脂的固化度随分子量增大略有下降 ,但固化物的玻璃化温度随分子量增加而升高 .增大辐射剂量 ,树脂固化度的提高受分子量大小的影响很小 ,分子量较大样品的网络均匀程度有所提高 ,在较高反应程度下 ,玻璃化温度主要受固化度影响 .树脂固化程度也是决定其模量高低的主要因素 ,而在固化程度相近的情况下 ,分子量的影响作用很大 .在同样辐射剂量下 ,分子量分布宽的树脂固化反应程度高 ,但交联网络均匀性低 .

DYNAMIC MECHANICAL ANALYSIS ON ELECTRON BEAM CURING OF EPOXY RESINS--INFLUENCE OF THE CHEMICAL STRUCTURE,MOLECULAR WEIGHT AND DISTRIBUTION OF EPOXY RESINS

Electron beam (EB) curing of polymer matrix composites offers many particular advantages compared to conventional thermal curing. There has been a considerable development about the EB curing advanced composites for the use of aerospace and other industries in recent years. Most variety of epoxy resin has been confirmed to possess radiation reactivity and have already become chief resin matrix used in EB curable composites. The dynamic mechanical analyses on EB cured epoxy resin were made in the paper. Epoxy resins with varied chemical structure, molecular weight and distribution index were used in the EB radiation experiment. The variation regularities of gel fraction, damping factor and dynamic modulus for different samples were studied. The experimental results indicate that the radiation reactivity of epoxy resins is directly associated with their chemical structures. Phenolic aldehyde epoxy resin exhibits high radiation reactivity, glass transition temperature and high temperature modulus after curing. But the radiation reactivity of alicyclic epoxy resin is low. The curing level of epoxy resin descends slightly with increasing molecular weight under low radiation dosage, but the glass transition temperature is enhanced. The molecular weight has a little influence on the enhanced extent of curing level with increasing radiation dosage and the degree of homogeneity in cross linked structure is improved for samples with high molecular weight. The glass transition temperature is under the influence of curing density at high reaction level. Similarly, the curing density is key factor to determine modulus of cured samples, but the molecular weight plays chief role in the samples with similar curing density. The reaction extent in sample with high polydispersity is higher under same radiation dosage, but the degree of homogeneity in cross linked structure is lower than that of low polydispersity sample.