Copolymerization And Self-Crosslinking Properties Of Poly(Butylene Itaconate)

Poly(butylene itaconate) (PBI) was prepared from itaconic acid (IA) and 1,4-butanediol (BDO) by polycondensation method. It is a new aliphatic polyester with low molecular weight and poor thermal stability, which has not been studied extensively. In this article, products with better properties were obtained by copolymerization and self-crosslinking of PBI.Three copolyesters Poly(butylene itaconate-co-butylene sebacate) (PBIS), Poly(butylene itaconate-co-butylene adipate) (PBIA) and Poly(butylene itaconate-co-butylene terephthalate) (PBIT) were synthesized using itaconic acid (IA) and 1,4-butanediol (BDO) as reaction monomers, sebacic acid (SA), adipic acid (AP) and dimethyl terephthalate (DMT) as copolymerization monomers respectively. The influencing factors of esterification and polycondensation on synthesis of the copolyesters were studied. The results showed that when the catalyst content was 0.16% (mol), the molar ratio of BDO versus (SA+IA) was 1.05:1, the esterification temperature was 150℃ and the polycondensation temperature was 220℃, the product with high molecular weight was obtained. FT-IR and 1H-NMR showed that the products were the expected polyesters. GPC showed that PBIS had the highest molecular weight, which was 12321. DSC and TG showed that the melting enthalpy, crystallization enthalpy and the initial decomposition temperature of PBIS had the highest values, and its thermal stability was the best. PBIS also had some biodegradability according to the enzymatic degradation test.A series of polyesters PBIS was synthesized using itaconic acid, sebacic acid and 1,4-butanediol as raw materials and its properties could be controlled by changing the proportion of SA in the copolyester. Its structure and properties were characterized by 1H-NMR, GPC, DSC, TG, XRD, tensile test and the enzymatic degradation test. It was found that the molecular weight of PBIS decreased firstly and then increased with the increasing of SA content. However, the melting point, melting enthalpy, crystallization temperature, crystallization enthalpy, crystallization ability, thermal stability and tensile strength increased with the increasing of SA content. Furthermore, the degradation rate had the opposite trend.The effects of DCP content and reaction time on self-crosslinking of PBI was studied. Besides, the process of PBI self-crosslinking system and the properties of crosslinked PBI were also discussed. It was found that the crosslinked PBI had better properties when the cured temperature was 155℃, DCP content was 1% mass fraction of the self-crosslinking system and the cured time was 4 hours. The self-crosslinking kinetic parameters tested by DSC and calculated by Kissinger-Crane equation were as Allows:the apparent activation energy 90.11 KJ·mol-1, reaction order 0.998, impact fa tor 2.44×1010. Furthermore, the gelation temperature, curing temperature and post cung temperature were determined by the extrapolation method and they were 96.9℃,152℃ and 200.2℃ respectively. DSC and TG results showed that the glass transi on temperature of PBI cured for 4 hours was 98.0℃, which increased the glass transition temperature of PBI by 126.2℃. And the PBI cured for 4 hours had better thermal stability, which the initial decomposition temperature was 296℃. The mechanical properties test showed that the tensile strength and bending strength of PBI cured for 4 hours were 39.3MPa and 72.63MPa respectively, which enhanced its mechanical properties.