1,3-PBO扩链改性端羧基聚乳酸的性能表征

以乳酸为原料、辛酸亚锡为催化剂,采用梯度升温法,在170℃、0.098 MPa条件下直接熔融缩聚合成端羧基共聚物P(LA/SA).将其用2,2-(1,3-亚苯基)-二噁唑啉(1,3-PBO)扩链,按n(—COOH)/n(—oxazoline)=1∶1.4比例加入1,3-PBO,在150℃,0.098 MPa条件下反应15 min制得聚酰胺酯(PEA).采用GPC、FTIR、1H-NMR、DSC、XRD、TGA、SEM等手段对聚合物的结构进行了表征和性能测试.结果表明,与P(LA/SA)相比,扩链产物相对分子质量大幅度提高,重均分子量达36×104;产物Tg比PLA升高,材料的刚性增强;产物热稳定性能提高,为一步分解;产物结晶度较P(LA/SA)降低,其柔韧性较P(LA/SA)增强,但相对于PLA有所降低.

STUDY ON CHAIN EXTENTING AND MODIFICATION OF P(LA/SA) WITH 1,3-PBO

The effects of the amount of chain extender,2,2′-(1,3-phenylene)bis(2-oxazoline)(1,3-PBO),on the synthesis of lactic acid based poly(ester-amide)(PEA) were studied.The carboxyl-terminated lactic acid-succinic anhydride copolymer(P(LA/SA)) was synthesized via directly melt polycondensation of L,D-lactic acid with succinic anhydride and Sn(Ⅱ)octoate as the catalyst at 168℃ and 0.098 MPa by the method of a gradient increased temperature.Then,the PEA was synthesized with P(LA/SA) as prepolymer and 1,3-PBO as extender.High molecular weight polymer was produced within a narrow range of copolymerization parameters.The highest molecular weights were achieved with the molar ratio of oxazoline/carboxyl end groups being 1.0/1.4 at 150℃ and 0.098 MPa for 15 min.The structure were characterized by spectroscopy(FTIR and 1H-NMR) and the properties were investigated by gel permeation chromatography(GPC),differertial scanning calorimetry(DSC),X-ray Diffraction(XRD),thermogravimetric analysis(TGA) and scanning electron microscope(SEM).Results indicated that the highest molecular weight was over 36×104 measured by GPC and the chain stiffness presented a tendency upward detected in mechanical properties as a result of the introduction of benzene rings and amide groups into PLA/SA.A distinct improvement in the thermal stability of the resulting polymer with the chain extender was observed compared with the unmodified PLA by TG,just as an one-step thermal decomposition.The crystallinity of the resulting polymer was higher than that of P(LA/SA),but lower than that of PLA which indicated that the flexibility of the resulting polymer was superior to P(LA/SA).