一种含树枝单元的高流动性尼龙6的原位聚合及性能测试

将低代数的树枝状大分子聚酰胺胺(polyamidomine,即PAMAM)分别与对苯二甲酸配制成母盐溶液,再以母盐溶液,己内酰胺,封端剂一起投入高压釜进行原位聚合,通过调节PAMAM在己内酰胺中的比例及改变不同的PAMAM代数得到新型高流动性尼龙6.FTIR显示,与线性尼龙相比较,高流动性尼龙6的γ(N—H)和2δ(N—H)两处对应峰都发生了明显的蓝移.对于树枝单元含量较低(0.3 wt%~0.5 wt%)的新型尼龙6,拉伸性能没有下降,缺口冲击强度增加,而熔体流动却显著得到改善.DSC显示,新型尼龙6的结晶曲线的结晶峰温度有不同程度的降低,晶体生长速率明显减慢.

in situ Polymerization and Characterization of High Fluidity Nylon 6 Contain ing Low Content of PAMAM Units

A new strategy was developed for preparation of high fluidfy nylon 6 on a large scale.Generation 1,2,3(G1,G2,G3) polyamidoamine(PAMAM) dendrimers reacted with p-phthalic acid by equimolar terminal groups in water solutions,respectively,and mother salt solutions were then prepared.The high fluidity nylon 6 was prepared with suitable quantity of mother salt solution,end capping agent(acetic acid) and ε-caprolactam by in situ polymerization.By changing the quantity of mother salt solution or the generation of PAMAM dendrimers,different samples of high fluidity nylon 6 were obtained.Blue shifts were found for the peaks of NH(γN—H and 2δN—H) of the high fluidity nylon 6 compared with pure nylon 6 in the IR spectra.Compared with pure nylon 6,the samples of high fluidity nylon 6 with low content of PAMAM units(0.3 wt%～0.5 wt%) had greater MFI,the value of MFI was improved about 70%～90%.It was also found that there was a drastic increment in MFI when the content of PAMAM units in PA6 matrix increased from 0.5 wt% to 1.2 wt%,while the molecular weight of the high fluidity nylon 6 did not decrease.For the high fluidity nylon 6 with low content of PAMAM units(0.3 wt%～0.5 wt%),the tensile strength did not decrease while the elongation at break decreased(ca.20%～35%),and the izod impact strength of different kinds of high fluidity nylon 6 increased.DSC thermograms of non-isothermal crystallization exhibited that the peak temperature of high fluidity nylon 6 was lower than that of pure nylon 6,and the peak of crystallization curve broadened comparing with the pure nylon 6 at the same crystallization condition,which broadened more with increasing the generation or the content of PAMAM units.Broader peak means the crystallization rate was decreased and the fluidity was improved,which benefits molding of small parts with thin walls or precision parts.