MDI与HDI封端共聚甲醛研究

Study on Co-POM Terminated with MDI and HDI

采用反应性熔融挤出法对共聚甲醛进行封端处理,研究两种不同异氰酸酯4,4'-二苯基甲烷二异氰酸酯(MDI)与六亚甲基二异氰酸酯(HDI)与共聚甲醛反应性挤出后的稳定化效果。通过测定熔体质量流动速率(MFR)、红外分析、热重分析(TGA)和黄色指数,评价共聚甲醛封端效果。结果表明,两种异氰酸酯均能对共聚甲醛进行封端,提高其热稳定性,MDI较HDI对共聚甲醛热稳定性的提高稍显著一些。随着异氰酸酯添加量增加,采用MDI反应性挤出样的MFR剧烈下降,而采用HDI反应性挤出样则下降一些后便保持平稳。MDI与共聚甲醛反应性挤出样较HDI与共聚甲醛反应性挤出样老化过程中颜色变黄更明显。

The polyoxymethylene copolymer was terminated during melting extrusion with isocyanates.The stability of reaction products with two different isocyanates-4,4＇-diphenylmethane diisocyanate and hexamethylene diisocyanate was investigated.The effects of eliminating the terminal hydroxyl were evaluated by melt flow rate （MFR）,Fourier transform infrared spectroscopy （FTIR）,thermal gravimetric analysis （TGA） and yellow index （YI）.The results showed that the two isocyanates both can make the unstable terminals end-capped and improve the thermal stability of Co-POM.The MDI＇s effect on improving the thermal stability was slightly better than HDI＇s.The MFR values of reaction product with the MDI decreased fiercely while the reaction product with the HDI dropped some and then remained stable.Moreover,it was found that during aging,the yellowing degree of reaction products with the MDI were evidently higher than that with HDI.