Study On Preparation Polysiloxane-Polycaprolactone And Toughening Polylactic Acid

Polylactide(PLA)is an environmentally friendly aliphatic polyester and has been emerging as an alternative to conventional petroleum-based polymeric materials because of its renewability,biodegradability and greenhouse gas neutrality.Although PLA is a high-strength and high-modulus polymer that is analogous to polystyrene and polypropylene,the inherent brittleness and low toughness of polylactide in its pristine state restrict its range of applications.Therefore,how to enhance PLA toughness become the focus of its applied research.In this paper,terminal hydroxyl poly(methylphenylsilane)(PMPS)was prepared,and then we have synthesized the polysiloxane-polycaprolactone copolymer(PCL-PMPS-PCL)and studied on its related performances.Polylactic/polysiloxane-polycaprolactone copolymer membranes are made by coating,and its related properties are investigated.The main works are as follows:1.Terminal hydroxyl poly(methylphenylsilane)(PMPS)was prepared via hydrolysis condensation method.FTIR and ~1H NMR prove successful synthesis of terminal hydroxyl poly(methylphenylsilane).The optimum conditions were as follows: the reaction temperature was 60 ?,the reaction time was 1.5h and the amount of catalyst was 1/200(The mass ratio of catalyst to total material).The poly(methylphenylsilane)were characterized by means of GPC,The results showed that the molecular weight and the molecular weight distribution of PMPS is 2387 and 1.25,respectively.2.Various polysiloxane-polycaprolactone copolymer(PCL-PMPS-PCL)are synthesized via ring-opening polymerization of caprolactone(CL)monomer,of which the molecular weights are design as 6387,10387,14387,respectively.FTIR and ~1H NMR prove successful synthesis of polysiloxane-polycaprolactone copolymer.GPC shows narrow molecular weight distribution of the obtained PCL-PMPS-PCL.The thermal properties,crystal structure and solubility were investigated by XRD,DSC and solubility test,respectively.The results showed that PMPS did not alter the crystal structure of PCL,and PCL-PMPS-PCL could be co-dissolved with polylactide(PLLA),which indicated that PCL-PMPS-PCL can import PMPS segments into PLLA.3.PCL-PMPS-PCL/PLLA blending membranes are prepared by coating.FTIR showed that PCL-PMPS-PCL was simply physically blended with PLLA without any chemical change in the film.The blendingr membranes are characterized by using DSC,tensile and transparency test.The effects of PCL-PMPS-PCL blending ratio on thermal properties and mechanical properties are studied in detail.The results show that blending PCL-PMPS-PCL would effect membranous thermal properties,The mechanics properties of membranes change with blending ration of PCL-PMPS-PCL adjusting,which show that the best performance at 15wt% of PCL-PMPS-PCL.In addition,the transparency test show that membranes transparency is still good after adding PCL-PMPS-PCL.