| In this paper,the aging behavior of food-grade polycarbonate(PC)was studied in different conditions,including indoor or outdoor environment and alkaline solution.In addition,the thermal stability and the thermal degradation activation energy of PC were further investigated with different aging methods.Investigated the migrations of phenols from PC into different food simulants.Several measurements,including Stereo-microscope,UV-Vis absorption spectrometer(UV-Vis),mechanical properties testing,Fourier infrared spectroscopy(FTIR),differential scanning calorimetry(DSC),thermogravimetric analyzer(TGA)were used to characterize the effects of aging degree of PC on structure and performance.The results were as follows,the defects on the surface of the PC samples were detected after aging in both indoor and outdoor environments,and the number of defects increased along with the aging time.Nevertheless,the defects on the surface of the PC samples aging in the indoor condition were much less than those of in the outdoor condition at the same aging time.After aging in the outdoor condition,the color difference(?C)and the yellow index(YI)of the PC samples gradually increased but the transparency(T%)decreased.Meanwhile,the PC samples aging in the outdoor condition were more yellow than the initial ones.On the contrast,the ?C,YI and T% of the PC samples aging in the indoor condition were almost unchanged.The mechanical properties of the PC samples decreased gradually after aging in the outdoor condition,and they had not changed significantly in the outdoor condition.The relative contents of bisphenol A(BPA)increased along with the aging time.The glass transition temperature(Tg)of the PC samples aging in both indoor and outdoor environments decreased along with the aging time.At the same aging time,the Tg of PC samples aging in the indoor condition is smaller than that in the outdoor.The thermal stability of the PC samples decreased after aging in both indoor and outdoor environments.After aging in the alkali solution,the white defects were randomly distributed on the surface of the PC samples.The mechanical properties had not changed significantly.In addition,?C and YI of the PC samples gradually increased but T% decreased.More importantly,the thermal stability of PC samples decreased companied with degradation reaction.With the increase of the aging time,the number and the size of defects increased.YI and ?C of the PC samples gradually increased but T% decreased along with the aging time.The relative content of BPA increased but the Tg of PC decreased with the aging time prolonged.Under the nitrogen atmosphere and several liquid medium conditions,such as hot water,acid solution,salt solution and alkaline solution,the thermal stability of the PC samples reduced with the aging time prolonged.By using the same aging methods and aging time,the aging degree of PC samples could be concluded as follows: Alkaline solution> Salt solution> Acid solution> Hot water.In the natural aging process,PC thermal stability also reduced along with the aging time.With the soaking time prolonged,the migration amount of BPA and phenol of unaged PC samples increased in different food simulants and finally up to the balance stage.With the prolongation of aging time,the migration of BPA and phenol in different food simulants also increased.Under the same aging methods and aging time,the migration amount of BPA in different food simulants was 95% ethanol solution> 65% ethanol solution> 20% ethanol solution> 4% acetic acid solution? water.The migration rule of phenol in different food simulants was 95% ethanol solution> 65% ethanol solution? 20% ethanol solution> water? 4% acetic acid solution. |
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