Food Contact Materials (PP, PET) In The Light, Hot And Humid Environment Life And Biosafety Assessment

The aging tests of the most commonly used food contact materials were carried out in the light environment,and the mechanical properties of PP and PET and the regularity of acetaldehyde migration in PET bottled water were obtained;The mechanical properties of PP and PET in light and hygrothermal environment were studied in detail.The service life of materials in daily environment was speculated.The safety of PET bottled water was evaluated.The main contents are as follows;(1)The photooxidation experiments of polypropylene under different illumination were carried out at 50 ℃,As a reference,the hot oxygen aging experiments were carried out at 50℃ and 60℃ for polypropylene without illumination;The relationship between the strength and time of PP is derived by using Arrhenius formula;The predicted material has a life expectancy of about 982 h,or 40 d,at a light intensity of 150w/m~2(equivalent to northern summer direct sunlight);The simulation experiment was carried out using xenon lamp aging box,and the actual life was 972h。(2)The tensile strength,flexural strength,elongation at break and bending modulus of PP were tested,It is found that the mechanical properties have different sensitivity to crystallization and degradation,resulting in different change rules;Light degradation is very destructive to materials,so in the production and life of PP products should avoid light transport storage,in order to extend its service life;On the other hand,PP waste materials can be treated by photodegradation.This method is relatively green and environmentally friendly.(3)The mechanical property of PET at 50℃,60℃,70℃,hygrothermal environment and the same temperature(50℃),300w/m~2 and 600w/m~2 were tested,elongation at break is used as index,the time temperature relation is obtained by Arrhenius formula,In the 25℃,the calculated service life is about 1014 h,that is 41 d,which is obviously inconsistent with the actual situation,The reason may be that the traditional mechanical performance evaluation method uses the injection molding standard sample and has a big structural difference and performance difference compared with the PET bottle blowing molding;Experimental methods need to be improved.(4)The acetaldehyde content of PET bottled water was tested at the same temperature(60℃),300w/m~2,600w/m~2,different light intensity and no illumination,The results showed that the amount of acetaldehyde migration was proportional to the light intensity and aging time,And under 600w/m~2 conditions(equivalent to four times the direct light in northern areas in summer),aging 1344 h,that is,56 days later,acetaldehyde concentration is still far below the drinking water safety concentration,Therefore,bottled mineral water even in the hot summer,under the influence of light,such as memory,mineral water,the removal of acetaldehyde content is still within the scope of safety,will not cause great harm to the human body.