| poly(vinyl alcohol) is a kind of degradable synthetical polymer.PVA film has many excellent properties.It can satisfy various requirements put forward by various callings.In this paper, aimed the problems of easy to be decomposed when melting extrusion and the low degradation speed of PVA, environmental riendly PVA/starch/ZnO nano-composite was prepared by melting extrusion on the base of thermoplastification of PVA .In order to improve the processing performances and to achive the melting extrusion of PVA film , the effect of different plastilizers on melting performance of PVA , effects of the amount of glycerol on melting temperature,crystalization temperature,mechanical performances and effect of vitamin E on the thermal stabilization of PVA were studied by DSC,TG and mechanical performances testing.Results showed that glycerol was the best plastilizer. The tensile strength decreased and the elongation at break increased with the increasing of glycerol.Vitamin E made the weight loss between 100℃to 180℃decrease and enhanced the decomposition temperature.In conclusion,the optimal technics was :0.5% of vitamin E,30% of glycerol,the rotating speed of extruder is 25r/min .In order to improve the degradation of PVA, PVA/starch blending film was prepared. Cross-linked starch was used to lower the moisture absorption of film, and the technics to prepare cross-linked starch was investigated based on microwave irradiation in solid state. The optimal condition were that irradiation under 270W for 3min, the mole ratio of sodium trimetaphosphate to starch was 0.05:1, the mole ratio of starch to sodium carbonate was 30:1, water content in mixed reatants was 8.06%. The method of microwave irradiation in solid state saved about five hundred times reaction time caMPared with traditional slurry method. No waste water was drained among preparation.With the increasing of starch , the tensile strength and elongation at break of PVA/starch film decreased.When the amount of starch was 25%, the tensile strength was 17.05MPa,the elongation at break was 425.00%.These data achieved the requests for the mechanical performances of package film.The cross-linking of starch lowered the moisture absorption of PVA/starch film.In order to enhance the dispersion of nano-ZnO in PVA,the nano-ZnO was modified by coating.Effects of modification factors on the dispersion of nano-ZnO in reaction system and the average size of nano-ZnO were investigated.The optimal conditions for coating were as follows:dispersing nano-ZnO with polyacrylate sodium of 1%,coating with sodium silicate of 3% at 23℃, and neutralizing for 1h at pH 9.In order to confirm the optimal amount of nano-ZnO, PVA/ZnO nano-composite was prepared by melting extrusion in optimal conditions. The results of performances investigating showed that the tensile strength and elongation at break were the highest when the amount of nano-zinc oxide was 1.0% and 0.5%,respectively. The tensile strength was 20.27% higher than that of neat PVA film,and the elongation at break was a little higher than that of neat PVA film. Nano-ZnO also improved the thermal stability, antiaging and the crystallization degree of PVA. It made new crystal come into being in PVA.The tensile strength and the elongation at break of PVA/starch/ZnO nano-composite with 1% nano-ZnO and 30% starch was 17.50MPa and 406.25%,respectively. These data achieved the requests for the mechanical performances of package film.The degradation of PVA film, PVA/starch film and PVA/starch/ZnO nano-composite were studied in soil and under UV radiation.It can be found that PVA/starch/ZnO nano-composite is bio-degradable. The degradation speed of films increases with the increasing of starch in it.After 112days,the weight loss of PVA film was 32.74%,and the weight loss of PVA/starch films with 10%,20%,30% starch were 37.51%,44.60% and 55.32%,respectively.Nano-ZnO restrained the growth of microbe slightly. The weight loss of PVA/starch/ZnO nano-composite 52.68% was between the PVA/starch film with 20%starch and the PVA/starch film with 30%starch. UV degradation showed the remaining ratio of elongation at break of PVA/starch/ZnO nano-composite 88% was the highest because of the restraining role of nano-ZnO on the growth of microbe.The remaining ratio of elongation at break of PVA film 73% was the lowest.The non-isothermal crystallization kinetic of PVA nano-composite was studied by DSC. The results showed that with the increasing of cooling rate, crystallization rate constant and the imperfection degree of crystallization increased. Under the same cooling rate,Avrami index and Zc of PVA/starch was the smallest,and t1/2 of it was the biggest.This indicated starch restrained the crystallization of PVA and nano-ZnO increased the crystallization rate of PVA because of the inhomogeneous nucleation. The non-isothermal crystallization kinetic of PVA nano-composite has indicated the crystallization behavior and the varying rule of their properties. It can guide the production of PVA products.
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