Manipulation Of Binary Modifier On Crystallization And Properties Of Poly(Lactic Acid)

In order to overcome problems of slow crystallization rate and poor toughness of poly(L-lactic acid)(PLLA).The different modifiers were simultaneously added to PLLA to overcome the difficulty of nucleation and improve the mechanical properties of PLLA.Their effects on the crystallization behaviors and toughness of PLLA were systematically investigated by differential scanning calorimetry(DSC),Wide angle X-ray diffraction(WAXD),Small angle X-ray diffraction(SAXS),scanning electron microscope(SEM),Polarized optical microscopy(POM)and mechanical properties test.Firstly,the effects of different proportions of modifier TMC-210/Talc and PLLA on the crystallization ability and mechanical properties of PLLA were investigated.The results showed that the binary modifier(TMC-210/Talc)could synergistically improve the crystallization ability including increasing of nucleating density and crystallization rate.The crystal size and long period of PLLA decreased.PLLA structure and its crystal form had no vaviration with the addition of TMC-210/Talc.Mechanical tests showed that TMC-210 and Talc could improve the plasticity and toughness of PLLA.The best elongation at break of 23.6%for PLLA could obtain under the condition of adding 4%Talc and 0.2%TMC-210 and increased by 262%Compared with PLLA/TMC-210 blends.The highest impact strength occurred when the content of the TMC-210/Talc was 0.2%and 1%.The value of the highest impact strength was 5.65 KJ/m2 and increased by 29.3%and 2.1 times than PLLA/TMC-210 blends and pure PLLA,respectively.Secondly,The PLLA/TMB-5 blends were modified by plasticizer PEG.The results showed that the addition of TMB-5 and PEG led to the glass transition temperature decrease.The crystallization temperature of PLLA/TMB-5/PEG blends shift to the high temperature,and the nucleation rate and the crystallization rate also increase.Moreover,the banded texture could be observeed with increasing of PEG content.But the structure and crystal form of PLLA was not affected.Mechanical tests showed that TMB-5 and PEG could improve the toughness of PLLA.The highest impact strength occurred when adding the content of the TMB-5/PEG was 3%and 0.5%.The value of the highest impact strength was 5.05 KJ/m2 and increased by 22.9%and 1.5 times than PLLA/TMB-5 blends and pure PLLA,respectively.Finally,the PLLA/TMC-328/TMP-6 blends were prepared through the melting method,their crystallization behavior,crystal form and mechanical properties were investigated in detail.It was found that TMC-328/TMP-6 enhances significantly the crystallization peak temperature and crystallization rate of PLLA from the melt state,and exhibits better nucleation effect than conventional modifier TMC-328.Moreover,mechanical tests showed that TMC-328 and TMP-6 could synergistically improve the toughness of PLLA.The highest impact strength occurred when the content of TMC-328/TMP-6 was 0.6%and 0.4%.The value of the highest impact strength was 4.33 KJ/m2 and increased by 10.7%and 1.3 times than PLLA/TMC-328 blends and pure PLLA,respectively.