| In this paper,the aging behavior of polyvinylidene chloride(PVDC)preservative film in thermal-oxidative aging,hot-water aging,photo-oxidative aging and microwave aging conditions was studied.In addition,the effects of different aging time and aging methods on the structure and properties of PVDC were investigated.The structure and properties of PVDC preservative film were characterized by color change,mass change,ordinary transmission microscope,FTIR,UV-Vis,fluorescence spectrophotometer,DSC,TGA and so on.Color change,FTIR and UV/Vis indicated that the PVDC preservative film degraded to produce a conjugated polyene sequence after aging.Ordinary transmission microscopy showed that the PVDC preservative film has thermal shrinkage with aging under four different aging modes,and the defects of the film were increased.The PVDC preservative film was seriously degraded under photo-oxidative aging conditions,the quality was reduced by up to 30.6%,and it was not degraded under microwave aging conditions,and the mass was reduced by 0.98%.FTIR and DSC results showed that under the conditions of thermal-oxidative aging,photo-oxidation aging and hot-water aging,the crystallization properties of PVDC preservative film were degraded,and the crystallization performance was slightly reduced under microwave aging conditions.UV/Vis results showed that the absorption bands of PVDC preservative film before and after microwave aging were basically coincident,and the optical properties changed little.The absorption bands of PVDC preservative film were red-shifted after thermal-oxidative aging,hot-water aging and photo-oxidation aging.After thermal-oxidative aging,the△C and YI of PVDC preservative film increased by 14times and 29.3 times,respectively,and T%decreased by 27.9%.After hot-water aging,the△C and YI of PVDC preservative film increased by 2.94 times and 6.74 times,respectively,T%decreased by 18.8%.After photo-oxidation aging,the△C and YI of PVDC preservative film increased by 9.3 times and 18.2 times,respectively,and T%decreased by 22.5%.The TG/DTG showed that there were two stages in the thermal weight loss of PVDC preservative film under nitrogen atmosphere,and the first stage was the main thermal weight loss stage.DSC results showed that there were two melting peaks in the PVDC preservative film.As the aging progresses,the two melting peaks were closed to each other.With the aging time prolonged,under the conditions of thermal-oxidative aging,hot-water aging and photo-oxidation aging,theΔHm andΔHc of PVDC preservative film were decreased,and t_c was prolonged.The crystallization performance was deteriorated.The microwave aging experiment showed that the PVDC preservative film had excellent performance,and only slight degradation occurred under microwave conditions,the structure and performance were not changed much,so we can use it with confidence. |
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