Preparation And Application Of Starch Graft Copolymer

In this paper,starch graft copolymer(GS)was prepared by graft polymerization,and then GS was melt-compounded with polylactic acid(PLA)to prepare PLA/GS blends.Montmorillonite was incorporated into emulsion of GS to fabricate composite(MGS).And the influence of MGS on the properties of PLA was further investigated.The research work was shown in the following aspects:(1)In order to introduce C=C and long alkyl chains into the starch macromolecules,esterified starch was prepared by stearyl chloride and acryloyl chloride.The chemical structure of esterified starch was characterized by IR and laman.The contact angle test showed that the hydrophobicity was significantly improved after esterification.Then,starch graft copolymers were prepared by soap-free emulsion polymerization,in which ethyl acrylate was used as monomer and KPS was used as initiator.The result of IR indicated that the grafted starch was successfully prepared.The method in our work was more stable and efficient than traditional method,which the monomer conversion rate of the graft polymerization reaction was 91.8%,the percentage grafting was 58.4%and the grafting efficiency was 50.8%.TEM microscopy revealed that core-shell structure of GS was achieved with core of the starch and shell of polyethyl acrylate.The starch graft copolymer was thermoplastic and had good mechanical property,water resistance and biodegradability.(2)PLA/GS blends were prepared by melt blending GS with PLA.The SEM microscopy displayed that GS particles were well dispersed in PLA matrix.Investigations of mechanical properties indicated that GS could improve the toughness of PLA significantly.When the content of GS was 20 wt%,the notched impact strength of the blend was increased to 31.4 KJ/m~2,moreover the the tensile strength and elongation at break were 52.8 MPa and411%respectively.Dynamic thermomechanical analysis indicated that the two T_gs of blends were closed each other,which meant GS was partially miscible with PLA.(3)Incorporating montmorillonite to emulsion of GS to prepare MGS,which was melt blending with PLA to fabricate PLA/MGS nanocomposites.The results of XRD indicated that MMT dispersed well in the PLA matrix,almost completely exfoliated.Investigations of mechanical properties showed that MMT improved the tensile strength and heat distortion temperature(HDT)of PLA.When MMT was 5 wt%,the tensile strength was 61MPa and the HDT was increased from 55.3℃to 64.8℃.DMA showed that the higher T_g of the increased from 63.0℃to 69.1℃with the addition of MMT.DSC and XRD results observed that MMT led to an increase of the crystallinity and melting point of PLA.