Résumé
A PP plastic film for food packaging (0. 1 mm) was prepared by adding two antioxidants of 2,6-di-tert-butyl-4-methyl-phenol(BHT) and pentaerythritol tetrakis ( 3-( 3, 5-di-tert-butyl-4-hydroxyphenyl ) propionate)(Irganox 1010) with different concentrations into polypropylene (PP) resin, then mixing extrusion granulate by the double screw plastic extruder and hot pressing the film at 190℃. The migration amount of the two antioxidants in food simulants (95% ethanol) was determined by high performance liquid chromatography (HPLC) with diode array detector (PDA) (detection wavelength is 282 nm). The migration of BHT was detected and Irganox 1010 was not detected. Based on the large amount of experimental data, the migration model was fitted by a software, then the migration model of antioxidant BHT was established, the applicability of the two migration model was compared with the actual data. The results showed that the fitting degree ( R2 ) of Weibull model to the actual migration result was greater than 0. 99 and better than Piringer model. It was found that there was a mathematical relationship as τ≈12. 2 ( L2/D) between parameters of Weibull model and Piringer model.
Résumé
The thermooxidative degradtion of ethylene oxide and tetra-hydrofuran (EO-THF) co-polyether has been studied by electron spin resonance(ESR),Fourier transform infrared (FT-IR) and nuclear magnetic resonance (NMR) spectroscopy. The initial degradation site was found to be at the α-carbon of the ether bond. Two free radicals which derived from dehydrogenation and oxygen addition were successfully detected by spin-trapping technique which used α-phenyl-N-tert-butyl nitrone (PBN) as spin trap. Both FT-IR and NMR have been used tofollow structural changes of the copolyether during degradation. Nearly 20 product frngnents including formate,carbonate,methyl,alcohol,methylene-dioxy,hydroperoxide and semiformal have been characterized by 1 D and 2 D NMR.The thermooxidtion of co-polyether preferred to occur on the THF units especially at the alternating linkage of EO and THF.Antioxidant (BHT) not only retarded the thermooxidation but also modified the degradation products with less ester and methylene-dioxy groups but more hydroxyl and methyl groups.