Research On Extrusion Blow Molding Process And Slow Release Properties Of PVA Slow-release/Controlled-release Packaging Film

As a new type of environmental protection and biodegradable packaging film, Poly(vinyl alcohol) film has been widely used in medicine,agriculture, chemical and other fields because of its slow release/controlled release property making through processing. The innovation of this paper is preparation of PVA slow release/controlled release packaging film through extrusion blow molding method. The plasticized modification of PVA BM-1 and PVA 1799 has been carried out respectively, and the process parameters in extrusion blow molding process are optimized, and the basic performance of the release/controlled release film has been characterized,and the experimental research plan on slow release/controlled release property been made.The plasticizing modification process of PVA BM-1 and PVA 1799 has been studied through melt index curve, infrared spectra, DSC curve,rheological properties, scanning electron microscopy(SEM). The result shows that the best mix ratio of the modified PVA BM-1 are as follows: the main plasticizer glycerin:ethylene glycol=1:1, DMSO’s adding amount is5% of the PVA BM-1, and the total distribution of plasticizer is 35% of PVA BM-1. The plasticizing modification makes the melting temperature of PVA BM-1 fall from 194.1℃to 161.8℃, dropped by 32.3℃. The best mix proportion of modified PVA 1799 is glycerol: H2O: di-ethanolamine =1:2:2, and the total distribution of plasticizer accounts for 30% of PVA1799. It can make PVA 1799 melting temperature drop to 169.9℃, the melting process far beyond its thermal decomposition temperature and achieve the melting of PVA BM-1 and PVA 1799, squeezing blown film successfully through the distribution of plasticizerPVA slow release/controlled release packaging film has done the basic performance tests on extrusion blow molding process. The result shows that the performance of PVA extrusion blow molding film can reach the best when slowly add the mixed plasticizer under the mixing conditions of80℃, the appropriate material mixing time is about 20 minutes, let it stand in the oven for 12 h under the temperature of 80℃, add 0.5% additivecalcium stearate, control the temperature in a state of 160℃< head temperature< 200℃, 3.5 r/min < RPM < 7 r/min, blowing ratio 2:1, traction ratio 3:1.With the increase of PVA BM-1, intermolecular forces become strong. It enhances the PVA blown film’s molecular chain and creamy,makes the tear intensity, tear strength of PVA blown film increased. It also makes permeability coefficient of the trend first increased and then decreased, with thermo-gravimetric rate gradually decreased.In addition, this paper has also determined the swelling rate of thin film, the water dissolution rate method is adopted to determine and further research on the slow-release mechanism and regularity of PVA film slow release/controlled release and slow release rate. The results show that PVA BM–1 has excellent water soluble in PVA slow release mechanism of slow release/controlled release film and PVA 1799 will not dissolve at common temperature, which can bulk up to certain extent. With the increase of the content of PVA BM-1, its swelling rate increases gradually. With the increase of PVA BM-1, the integral dissolution rate of slow release/controlled release membrane increases. Differential dissolution rate tending to be no longer change as it first increases then decreases finally.With the membrane thickness PVA slow release/controlled release increasing, initial dissolution rate reduces, and the differential dissolution rate also gradually reduces. So the ratio of PVA 1799 and PVA BM-1 and the thickness of the PVA film affect the PVA sustained-release performance of slow release/controlled release membrane. We can control the release effect by way of controlling these two factors to achieve the PVA slow-release performance of slow release/controlled release film.