离子液体增塑生物基聚丁内酰胺的热分解机理

Thermal Degradation Mechanism of Bio-based Polybutylactam Plasticized by Ionic Liquids

采用疏水性1-丁基-3-甲基咪唑六氟磷酸盐([BMIM]PF_(6))和亲水性1-丁基-3-甲基咪唑四氟硼酸盐([BMIM]BF_(4))两种咪唑类离子液体(IL)增塑聚丁内酰胺(PBL),探讨了IL对PBL结晶性能及热性能的影响.研究发现,两种IL都会削弱PBL分子间氢键,并抑制PBL晶体在(200)晶面的生长,降低PBL结晶度.当IL添加质量分数为5%时,增塑膜熔点下降7~8℃.与纯PBL膜相比,[BMIM]BF_(4)增塑PBL膜热稳定性下降,而[BMIM]PF_(6)增塑PBL膜的热稳定性提高.[BMIM]PF_(6)增塑PBL膜热分解过程的热动力学分析结果表明,其热分解反应活化能为46.68 kJ/mol,反应级数为1,热分解最概然机理函数模型符合Mampel单行法则(一级),即PBL受到热刺激后,在聚合物和分解产物界面无规律成核,反应核心具备反应活性,随后反应逐步扩大,直至结束.

Polybutyllactam(PBL)has attracted increasing attention in recent years since it can be degraded in various natural environments including water.However,due to the melting point is close to the thermal decomposition temperature,it cannot be melting processed and the application is limited.Therefore,reducing melting point and improving thermal stability of PBL becomes an urgent problem.Herein,two imidazolium-based ionic liquids(ILs),hydrophobic 1-butyl-3-methyl-imidazolium hexafluorophosphate([BMIM]PF_(6))and hydrophilic 1-butyl-3-methyl-imidazolium tetrafluoroborate([BMIM]BF_(4)),were applied to plasticize PBL,and their effects on the crystallization and thermal properties of PBL were investigated.It was found that both ILs weakened the intermolecular hydrogen bonds of PBL,inhibited the growth of PBL crystals at the(200)crystal plane and reduced the crystallinity of PBL.When the addition mass fraction of ILs was 5%,the melting temperature of PBL was decreased by 7—8℃.Compared with pure PBL film,the thermal stability of[BMIM]BF_(4)plasticized PBL film decreased slightly,while that of[BMIM]PF_(6)plasticized PBL film improved.The results of thermal kinetic analysis of[BMIM]PF_(6)plasticized PBL film showed that the activation energy(E)of thermal decomposition is 46.68 kJ/mol,and the reaction order(n)is 1.The most probable mechanism function model of thermal degradation follows the Mampel power law(first order).It indicates that when PBL is thermally stimulated,it irregularly nucleates at the interface between polymer and decomposition products.The reaction core is of reactivity and the reaction gradually expands until the end.