Study On The Performances Of Aging On Bottle-grade PET

The present work was concerned with the study about the influence of hot-water aging,solution aging and weathering aging on properties of bottle-grade PET.The relationship between the migrations of harmful substances and the degree of thermal-oxidative aging,photo-oxidation aging and weather aging were studied.The effects of different aging time and aging methods on PET structure,mechanical properties,optical properties,crystallization properties,thermal stability and migrations of harmful substances were investigated.The properties of hot-water aging PET were characterized by mechanical properties,spectroscopy,FTIR,TG and so on.The mechanical properties showed that the crystallization in the initial stage played a leading role,then water plasticization was dominant,and the hydrolysis played a main role in the later stage of hot-water aging.FTIR,XRD,DSC and other tests indicated that the crystallinity increased after hot-water aging.UV/Vis showed that the transparency of PET after hot-water aging reduced by 48.3%,?C increased by 10.1 times and YI increased by 13.4 times.TG results showed that PET had two heat loss steps in the air atmosphere,and the thermal stability increased with the hot-water aging and then decreased.Under the nitrogen atmosphere,PET had only one heat loss weight step,and the initial decomposition temperature was 43.3? higher than that in the air atmosphere.The same characterization methods were used to analyze solution aging.DSC showed that the endothermic peak appeared in the glass transition zone due to the enthalpy relaxation.With the aging of the solution,the tensile strength of PET increased by 12.7MPa,the flexural strength increased by 18.8MPa,and the elongation at break decreased from 290% to zero.UV/Vis showed that the PET transmittance increased and the ?C and YI decreased after solution aging.FTIR showed that PET didn't hydrolyze and the crystallinity did not change much after solution aging.The same characterization methods were used to analyze the effect of weather aging on the properties of PET.Stereo-microscope found surface defects on PET after weather aging,and defects in the outdoor aging is yellow.Mechanical properties of PET deteriorated after weather aging,and brittle fracture occurred.UV/Vis showed that the transparency of PET decreased after outdoor aging,and ?C and YI increased.The fluorescence spectra showed a new emission peak at 450 nm after outdoor aging.FTIR results indicated that the degradation of PET occurred after weathering aging to produce hydroxyl and carboxyl groups.The retention time of acetaldehyde was 4min,and it wasn't detected by HS-GC-MS for PET without aging,240 h of thermal-oxidative aging and 240 h of photo-oxidation aging.The other harmful substances were detected in PET by GC-MS,and it showed that an antioxidant 2246 was detected.The different aging methods and aging time on the heavy metal migration of PET were studied by ICP-MS.The results showed that the migrations of heavy metal Sb in water,acetic acid and ethanol simulants were higher under the conditions of thermal-oxidative aging,photo-oxidation aging and indoor aging.The heavy metals Cu and Pb moved out from water and acetic acid simulants after outdoor aging.The migration of Sb increased by different aging methods in water-based simulants,decreased in ethanol simulants,and was irregular in acetic simulants.The degree of influence on Sb migration by the simulants was ethanol> acetic acid> water,The degree of influence on Mn migration by the simulants was acetic acid> water> ethanol.The migrations of Mn and Cu were more affected by acetic acid simulants during indoor aging.The migrations of Mn,Cu and Pb were more affected by acetic acid simulants during outdoor aging.