三聚氰胺甲醛树脂纤维素共混模塑料的热稳定性

The Thermal Behavior of Melamine-Formaldehyde Resin Cellulose Molding Materials

按n（F）/n（M）（甲醛与三聚氰胺物质的量比）=2.0~4.0合成系列三聚氰胺甲醛树脂,制备了纤维素共混模塑料。通过热重（TG）、动态热机械分析（DMA）、弯曲和冲击试验研究了模塑料从室温到600℃的性能变化,通过分析其热行为,确认了模塑料中的主要化学结构。当n（F）/n（M）=3.0~3.5时,树脂交联结构完善,能获得最高的冲击强度和Tg,分别是1.28 kJ/m2和118.8℃。模塑料中的树脂在150℃以上会发生后固化反应,在180℃以上开始断链和降解。α-纤维素通过N-羟甲基与树脂分子发生交联反应,使纤维素的热分解速率下降,模塑料刚性增加。

Melamine-formaldehyde resins were synthesized with n（F）/n（M）=2.0～4.0,then the molding materials with cellulose were prepared.The melamine-formaldehyde cellulose molding materials were characterized by dynamic mechanical analysis（DMA）,thermogravimetry test（TG）,bending and impact test.The results show the main chemical structures present in these molding materials.A melamine-formaldehyde resin synthesized with the n（F）/n（M）=3.0～3.5 can form best crosslinking structure and obtain the maximum impact strength（1.28 kJ/m2）和and Tg（118.8 ℃）.The molding compounds have a secondary curing reaction over 150 ℃.Chain scission and degradation of MF resin will occur at more than 180 ℃.A crosslinkage reaction occurs between N-methylol groups in MF resin and hydroxy groups in α-cellulose.This reaction will decrease the cellulose pyrolysis rate and increase the rigidity of MF molding materials.