一种镧基金属有机框架的制备及其对聚碳酸酯火安全性和热稳定性的影响

Fabrication of a La-based Metal Organic Framework and Its Effect on Fire Safety and Thermal Stability of Polycarbonate

通过热溶剂法合成了一种镧基金属有机框架(La-BDC),再通过熔融共混的加工方法将La-BDC加入至聚碳酸酯(PC)中制备复合材料(PC/La-BDC).经热失重(TGA)、锥形量热(Cone)、垂直燃烧等测试,结果证明,La-BDC明显改善了PC的火安全性能,并提升了其热稳定性.与纯PC相比,2 wt%La-BDC可以使PC在空气下的2个最大分解温度(Tmax1和Tmax2)分别提升43和40°C;4 wt%La-BDC可以使PC的峰值热释放速率(PHRR)降低高达50%,平均比消光面积(ASEA)下降38%,且在垂直燃烧测试中达到UL-94V-0等级.一方面,裸露的镧金属离子簇作为配位中心使得La-BDC在PC高温燃烧和降解阶段具有催化氧化、异构化等反应的能力,促进了基体的交联成炭,扫描电子显微镜(SEM)、拉曼光谱(Raman)等测试证实形成了更加致密、高度石墨化的炭层,有效抑制了热量、可燃产物和有毒烟雾的溢出;另一方面,La-BDC的棒状晶体结构及其自身骨架含有的介孔结构,使得其在吸附、延缓烟雾产生方面有一定作用.

A La-based metal organic framework(La-BDC) was synthesized by a solvothermal method and then compounded with polycarbonate(PC) to prepare PC/La-BDC composites. The experimental(TGA, cone, vertical burning test, etc.) results showed that La-BDC improved the fire safty and thermal stability of PC. Compared with the neat PC, 2 wt% La-BDC could increase the two maximum decomposition temperatures(Tmax1 and Tamx2) of PC in air atmosphere by 43 and 40 °C, respectively;4 wt% La-BDC could reduce the values of peak heat release rate(PHRR) and average specific extinction area(ASEA) by 50% and 38%, respectively. PC/LaD-4 composites reached UL-94 V-0 rating in vertical burning test. On the one hand, naked La metal ion cluster, as a coordinated center, afforded La-BDC activity in catalytic oxidation, isomerization reactions etc., imparting it the ability to catalyze char formation(cross-linking) in the combustion and degradation process of PC matrix. From SEM images and Raman spectrum, the denser and highly graphitized char layers were obtained. The char layers reduced the contact between the matrix and oxygen, effectively suppressing the spillover of heat, pyrolysis products and toxic fumes. On the other hand, the rod-like crystal structure of La-BDC and the mesopores contained in its own framework structure made it play a role in adsorption and retarded of smoke generation.