Study On Preparation And Properties Of Waxy Rice Flour-based Biodegradable Composites

Starch is a kind of natural polymer with extensive sources, which is renewable andbiodegradable, but there are shortcomings easy to absorb water，and it can not melt. Theexpanded waxy rice flour-based biodegradable composites were prepared with the expandedwaxy rice flour (PSt) of lower crystallinity, the ε-caprolactone of good biodegradability andthe lamellar organic montmorillonite, they will be of wide application prospect in the fields ofthe general polymer materials and the medical materials, and will produce the enormouseconomic benefits. The main contents and results list below:1. The expanded waxy rice flour-g-polycaprolactone (PSt-g-PCL) copolymer withthermoplasticity was synthesized via the ring-opening graft copolymerization ofε-caprolactone onto the backbone of expanded waxy rice flour in the presence of stannousoctoate catalyst. Determining the best feeding for ε-caprolactone monomer and expandedwaxy rice flour ratio was3.3:1(mL/g). The maximum grafting content was89.16%. DSCresults showed that PSt-g-PCL was a kind of thermoplastic coplymer, and its melting pointwas64.66℃; TGA results showed that the thermal decomposition temperature of the part ofPSt lowered when PCL grafted onto the backbone of the expanded waxy rice flour; XRDanalysis indicated that the PSt-g-PCL was a kind of crystalline polymer; SEM observationshowed that the surface morphology of PSt changed and formed the new morphology aftergrafting PCL onto the backbone of the expanded waxy rice flour.2. The expanded waxy rice flour grafted-g-polycaprolactone (PSt-g-PCL)/organicmontmorillonite (OMMT) nanocomposites were prepared through the method of in-situintercalated polymerization. DSC results indicated that the crystallization temperature was35.49℃in PSt-g-PCL/OMMT nanocomposite with5wt%amount loading OMMT. XRDresults showed that the layer spacing increased and the peak of original OMMT at2θ=4.90°became broader and shifted to2θ=4.70°in PSt-g-PCL/OMMT nanocomposite with15wt%amount loading OMMT; SEM observation showed that the stack lamellar structure of OMMTwas destroyed and morphology changed. It indicated the PSt-g-PCL had intercalated intosilicate layers of OMMT. TGA results indicated that the thermal stability of nanocompositeswere improved by adding OMMT. When adding15%OMMT in PSt-g-PCL/OMMT nanocomposite, the thermal decomposition temperature of maximum decomposition rate ofthe part of PSt and the part of PCL were345.75℃and411.29℃, respectively.3. LDPE/EAA/(PSt-g-PCL/OMMT) ternary blend composites were prepared by themethod of melt blending. This article discussed the effect of adding different amounts ofethylene acrylic acid (EAA)(3%,5%,7%,9%and11%) on properties of ternary blendcomposites. FT-IR analysis showed that the hydrogen bonding was formed between the C=Oof the carboxyl of EAA and the residual hydroxyl of PSt-g-PCL. DSC results indicated thatthe compatibility of LDPE and PSt-g-PCL/OMMT were poor, but the addition of EAA couldimprove the compatibility between them. Mechanics performance test showed that the tensilestrength of the ternary blend composites decreased and the elongation at break increased withthe increase of EAA.4. This article discussed the effect of adding different amounts of PSt-g-PCL/OMMTnanocomposite (7%,17%,27%and47%) on properties of LDPE/EAA/(PSt-g-PCL/OMMT)ternary blend composites. Mechanics performance test showed that the mechanical propertiesof the ternary blend composites decreased when adding the PSt-g-PCL/OMMT nanocomposite.It had better comprehensive mechanical properties in the ternary blend composite with17wt%amount loading PSt-g-PCL/OMMT nanocomposite. The tensile strength of the ternary blendcomposite was8.0Mpa, and the elongation at break was90.41%. SEM observation indicatedthat the ternary blend composites had good compatibility when the additive amount ofPSt-g-PCL/OMMT nanocomposites were7wt%and17wt%. The maximum water absorptionof the ternary blend composite was2.43%when adding47wt%PSt-g-PCL/OMMTnanocomposite. It had good resistance to water, and quality retention was92.766%after soilburial biological degradation test for100days; it proved that the ternary blend composite hadbetter biological degradability.5. It can be concluded that the addition of OMMT improved the tensile strength andwater resistance of LDPE/EAA/(PSt-g-PCL/OMMT) ternary blend composite compared withLDPE/EAA/PSt-g-PCL ternary blend composite, but it led to the decrease of the elongation atbreak and the biodegradability.