Synthesis Of Multi-arm Poly-D-lactic Acid And Its Effect On The Linear Crystallization Properties Of Poly-L-lactic Acid

In this paper, PDLA-EPOSS were prepared by in situ ring-opening polymerization, and their structures and dipersibility were characterized. Then PLLA/PDLA-EPOSS were prepared by melt blending of PLLA and PDLA-EPOSS. The effect of different contents of PLLA-POSS on crystallization rate for PLLA were studied mainly.PDLA-EPOSS were prepared by in situ ring-opening polymerization of D-lactide(D-LA) with EPOSS and stannous octoate(Sn(Oct)2) was used as a catalyst. FTIR, 1HNMR and XRD showed that a copolymer was formed by D-lactide and EPOSS, and EPOSS didn’t change the crystal of PLLA. The molar mass and properties of PDLA-EPOSS were studied by means of GPC, TGA, DMA and the contact angle measurement. The GPC results showed the content of EPOSS could control the molar mass of PDLA-EPOSS. The TGA analysis could be found the higher molecular mass could improve the thermostability of PDLA-EPOSS. The DMA analysis showed that, with increasing content of EPOSS, PDLA-EPOSS storage modulus, toughness and glass transition temperature increased. The test of contact angles showed that EPOSS added could improve the hydrophily of PDLA-EPOSS.Isothermal crystallization and non-isothermal crystallization of PLLA/PDLA-EPOSS were tested by DSC and the use of POM could observe the isothermal crystallization process of crystal morphologies, the conclusion of which were as following:Isothermal crystallization process of PDLA-EPOSS were analyzed Avrami equation, PDLA-EPOSS could speed up the crystallization rate of PLLA, but also significantly shorten the crystallization half time of PLLA. PLLA/PLLA-POSS1.00 5% was the best one, crystallization half time of which was minimum, only 1.45 min at 115°C. POM photoes showed that PDLA-EPOSS was introduced to speed up the crystallization rate of PLLA, increases crystallization nucleation density and become the crystal ball increasingly dense.In non-isothermal crystallization process, with the cooling rate decreases, Tp value moves to the high temperature zone. Jeziorny analyzed by the method can be obtained, PDLA-EPOSS1.00 made non-isothermal crystallization mechanism and nucleation of PLLA change. With increasing cooling rate, n value of samples decrease. While at the same cooling rate, compared with PLLA, n value of PLLA/PDLA-EPOSS changed slightly. By comparison kc, it can be found that crystallization rate of the sample with the cooling rate increases, at the same time, at the same rate of crystallization, PDLA-EPOSS1.00 5% of the maximum crystallization rate.