1,3-PBO扩链改性端羧基聚乳酸的性能表征

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

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.

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 aeid-succinic anhydride copolymer （P（LA/SA） ） was synthesized via directly melt polycondensation of L, D- lactic acid with succinie anhydride and Sn（ 1] ） octoate as the catalyst at 168~C 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 eopolymerization parameters. The highest molecular weights were achieved with the molar ratio of oxazoline/carboxyl end groups being 1.0/1.4 at 150~C and 0. 098 MPa for 15 rain. The structure were characterized by spectroscopy （ FTIR and I H-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 x 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）