BM-DVB多孔共聚体及其炭化物的热性能

在相同条件下,分别以4,4'-双马来酰亚胺二苯基甲烷(BM)与二乙烯基苯(DVB)的摩尔配比1∶4、1∶1、4∶1,采用悬浮共聚法合成了BM-DVB珠状多孔共聚体.炭化前,对所制BM-DVB共聚体用二种方法进行预处理:(1)热空气稳定化(产物标名PO-C 800);(2)H3PO4浸渍(产物标名P 800).而后,将两种预处理所获产物在Ar气中800℃进行炭化.采用热重(TG)和热差(DSC)法表征了BM-DVB多孔共聚体及其炭化物的热性征.结果表明:单体配比的差异导致了初始聚合体的不同交链程度.共聚体及其炭化物的热稳定性与其组成存在一定的相关性.在BM:DVB摩尔比为4∶1时,BM-DVB共聚体的耐热性最高;其因在于共聚体中含有的氮原子浓度最高.在BM:DVB摩尔比为1∶4时,BM-DVB共聚体具有高的交链度,但热性能最差;这可能由其微孔性能和较少的含氮量所致.而它们炭化物的热性能却非常相似,几乎不受BM-DVB共聚体的影响.可以认为,影响BM-DVB炭化物热性能更重要因素是BM-DVB共聚体在预处理过程中形成的孔隙率和表面化学性能.

Thermal properties of porous copolymers of BM-DVB and their carbonization products

Thermogravimetry and differential scanning calorimetry were used for characterization of the thermal properties of new 4,4'-bismaleimidodiphenylmethane (BM) and divinylbenzene (DVB) porous copolymers and their carbonization products. Bead-shaped porous copolymers BM-DVB with the following monomer ratios 1:4, 1:1,4:1 were synthesized using suspension copolymerization under the same conditions. Differences in the monomer ratio caused a different degree of cross-linking of the starting polymers. Before carbonization, the BM-DVB copolymers were pretreated using two methods. In one method, the starting material was stabilized in hot air ( product was labeled PO-C800). In the other method, the copolymer was soaked in H3PO4 (product was named P800). Then, materials obtained by both methods were carbonized at 800 ℃ in an argon atmosphere. To characterize the heat resistance of the BM-DVB copolymers and their carbonized derivatives, their thermostabilities were evaluated. The data suggest the existence of a relationship between the composition and thermal stability of the copolymers and their carbonized derivatives. The most thermally resistant copolymer was that obtained with a 4:1 molar ratio of BM to DVB. Its thermal stability is caused by the high concentration of nitrogen atoms in the polymeric structure. 1:4 BM-DVB copolymer with a high degree of cross-linking was the least thermally stable, which might be caused by its microporous nature and small fraction of nitrogen. The derived carbons have very similar thermal properties, and an insignificant influence of the nature of the polymer precursor was observed. More important factors affecting thermal stability were the porosity and surface chemistry, which were created in the thermal pretreatment processes.