Properties Of PLAs Effect Of POSS Grafted Polymer On The Crystallization

In the context of rapid economic and technological development,the abuse of non-renewable resources such as fossil energy has caused irreversible damage to the environment.Therefore,it is urgent to find new energy sources to replace the use of fossil resources.Polylactic acid?PLA?is a biodegradable green resource that can replace non-renewable resources such as fossil.However,it has poor crystallization ability,so it is necessary to explore the influencing factors to improve the crystallization ability of PLA.In addition,the PLA's crystallization capability is also improved to some extent by the formation of Stereoblock copolymer?SC?due to its special optical isomer.Therefore,it is particularly important to systematically discuss the factors affecting the crystallization capacity of Homo-Crystals?HC?and SC.Firstly,the effect of Monoamino-Polyclay Silsesquioxane?POSS-NH₂?as a nucleating agent on the crystallization behavior of Poly?L-lactic acid??PLLA?has been investigated.The results show that the crystallization,melting?T_c?T_m?and cold crystallization(T_cc)temperatures of PLLA decrease with the addition of POSS-NH₂.The Flash DSC?FSC?results show that PLLA₄₈₀₀₀with a critical cooling rate to inhibit nucleation behaviors of 100K/s and a critical heating rate to inhibit nucleation behaviors of 250K/s,respectively.The critical cooling rate of 10wt%POSS-NH₂/PLLA₄₈₀₀₀ to inhibit nucleation behaviors is 1000K/s.The addition of POSS-NH₂ promotes the nucleation of PLLA₄₈₀₀₀,but excessive POSS-NH₂ hinders the movement of the PLLA₄₈₀₀₀molecular segment and reduces the crystallization rate.10wt%POSS-NH₂ has the greatest effect on the improvement of PLLA₄₈₀₀₀ crystallization rate.The optimum crystallization temperature of PLLA is 100?,and the crystallization rate is 5.72×10^-3s^-1.The optimum crystallization temperature of 10 wt%POSS-NH₂/PLLA₄₈₀₀₀ decreases to 90?,and the crystallization rate is14.47×10^-3s^-1.Secondly,Polycaprolactone-Polyclay Silsesquioxane?POSS-PCL?and L-Poly?L-lactic acid?-Polyclay Silsesquioxane?POSS-PLLA?graft polymers of different molecular weights were prepared by ring-opening polymerization.The effect of nucleating agents and plasticizers on the crystallization behavior of PLLA₄₈₀₀₀ was investigated.The results show that the addition of Poly?ethylene glycol?-Polyclay Silsesquioxane?POSS-PEG?increases the crystallization temperature of PLLA₄₈₀₀₀ and and the cold crystallization peak disappeared,indicating that the crystallization capability of PLLA₄₈₀₀₀ is promoted.The results of FSC show that the temperature heating and cooling rates of 10wt%POSS-PEG/PLLA₄₈₀₀₀ inhibition nucleation are 1000K/s and4000K/s,respectively.The crystallization enthalpy of the blend and the crystallization temperature are increased with the addition of POSS-PLLA₂₇₀₀₀.The change trend of POSS-PCL₆₈₀₀/PLLA₄₈₀₀₀ is the same as that of POSS-PLLA₂₇₀₀₀/PLLA₄₈₀₀₀,indicating that the addition of POSS-PLLA₂₇₀₀₀ and POSS-PCL₆₈₀₀ improves the crystallization ability of PLLA₄₈₀₀₀.Polarizing Microscope?POM?results show that with the POSS-PEG content increases,the nucleation point of the blend decreases,so PEG plays a leading role in the crystallization process.Comparing the crystallization rates of several composites,it is found that 10%POSS-PEG has the greatest increasing in the crystallization rate of PLLA₄₈₀₀₀.Thirdly,different ratios of PLLA₄₈₀₀₀ and PDLA₅₉₀₀₀ were blended to form SC.As the mass ratio of PDLA₅₉₀₀₀ increased,the degree of SC formation gradually increased.DSC results show that when the ratio of PLLA₄₈₀₀₀ and PDLA₅₉₀₀₀ is 1:1,only the melting peak of SC can be observed in the blend.This indicates that when the quality of PLLA₄₈₀₀₀ is the same as that of PDLA₅₉₀₀₀,the chain segments of PLL_A48000 will be more complex with PDLA₅₉₀₀₀ chain segments to form SC.When the ratio of PLLA₄₈₀₀₀ and PDLA₅₉₀₀₀ is 1:9?or 9:1?,POM results show that SC and HC existed simultaneously,and HC is attached to SC growth.Finally,the effect of POSS combined with PCL,PLLA,PEG segments on the crystallization behavior of HC and SC were studied.The crystallization behavior of the blend was studied with DSC,X-Ray Diffraction?XRD?and POM.When the ratio of PLLA₄₈₀₀₀ and PDLA₅₉₀₀₀ is 1:1,increasing the mass fraction of POSS-PEG will promote SC to HC transition.The crystallization of SC in PLLA₄₈₀₀₀/PDLA₅₉₀₀₀ is inhibited when the POSS-PLLA₂₇₀₀₀ and POSS-PCL was added.When the graft polymers POSS-PCL-PLLA is blended with PDLA₅₉₀₀₀,the overall crystallization ability of SC is deteriorated.