| The aging behavior of polycarbonate(PC)and polyethylene terephthalate(PET)in indoor and outdoor environment was studied,and the optical properties,mechanical properties and the thermal stability were investigated.The changes of structure and properties after natural aging were characterized by stereo-microscope,uv-vis absorption spectrometer(UV-Vis),mechanical properties analysis,fourier infrared spectrometer(FTIR),differential thermal scanning calorimeter(DSC),gel permeation chromatography(GPC),nuclear magnetic resonance hydrogen spectrometer(~1H-NMR),fluorescence spectrometer and thermogravimetric analyzer(TGA).The defects on the surface of the PC samples after aging and the number and size of the defects in the indoor sample gradually increase with the aging time,and the defects in the outdoor sample gradually evolve into cracks,causing the surface layer of the sample to fall off;The?C and YI of the PC sample gradually increased,the T%decreased,and the sample yellowed and gradually deepened;the?C,YI,and T%of the indoor sample remained almost unchanged;the mechanical properties of the PC gradually declined after natural outdoor aging,and later The rate of decrease in crosslinking reaction is slowed down;although the mechanical properties of the indoor samples are reduced,the decrease is not large;the strength of the ester group of the PC sample decreases after aging,and the peak intensity of the characteristic absorption peak of the phenolic hydroxyl group gradually increases.The relative content of BPA increases with the aging time.During the outdoor natural aging process,the photooxidation mechanism is more preferred than the photo-Frisian rearrangement.After natural aging indoors and outdoors,the Tg of PC samples gradually decreased,indicating that After aging,the downward trend slows down due to the cross-linking reaction and the plasticizing effect of water in the late stage of the degradation reaction;1H-NMR analysis results show that hydroxyl Closing peak,and the sample surface material structure changes,IR spectra inferred integrated PC optically pre-mainly Fries rearrangement,into the photo-oxidation,and the final product may be a phenolic acid and other substances.The PET samples have defects on the surface after indoor and outdoor aging.Due to the harsher conditions of the outdoor samples,the defects gradually evolve into cracks,which eventually lead to the destruction of the samples.After natural aging,the transmission rates of the indoor and outdoor PET samples are both Decrease,the?C and YI of the sample increase significantly with the increase of aging time,and the T%decreases.Compared with the indoor sample,the outdoor optical aging PET optical parameters change more drastically;after the outdoor natural aging,the mechanics of the PET sample The performance is obviously reduced,but the indoor sample does not change much;the fluorescence spectrum results show that the PET sample naturally absorbs the benzene ring absorption peak at 270nm after indoor and outdoor natural aging,and the intensity increases with the aging time.The effect leads to a new absorption peak at 450nm for outdoor PET samples;infrared spectroscopy results indicate that PET degradation produces carboxyl groups after natural aging,and its content increases with aging time.After outdoor aging,the trans conformation increases and the cis conformation increases.Decrease,the crystallinity increases,and the indoor sample does not change significantly;with the increase of natural aging time indoors and outdoors,Tg and Tm change little,Tp increases,Tcc?Tmc reduced,TC shortened,indoor and outdoor aging crystalline PET were improved,increasing Xc.Thermal degradation kinetics results show that there are two stages of thermal degradation of PC and PET in an air atmosphere.After natural aging indoors and outdoors,the thermal stability of PC first decreases and then rises slightly,while the thermal stability of PET first decreases and then rises high and gradually higher than the unaged sample. |
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