Preparation And Properties Of High Barrier Vinylidene Chloride-methyl Acrylate Copolymer Resin Film

Oxygen and water vapor are important factors to accelerate food corruption and corrosion of metal products,and high barrier packaging can greatly delay this process.Polyvinylidene chloride?PVDC?has excellent barrier properties for both water vapor and oxygen,and the barrier properties do not change with external humidity.However,the melting temperature of PVDC is too close to its decomposition temperature,and different types of PVDC resins require specific heat stabilizers,making thermal processing difficult.In this paper,methyl acrylate?MA?was introduced into copolymerization with vinylidene chloride?VDC?to obtain a thermally processable,low melting temperature VDC-MA copolymer resin.The copolymer resin is combined with heat stabilizers and other processing aids to successfully prepare a high barrier VDC-MA copolymer resin film.The thermal oxygen aging and thermal degradation kinetic analysis were used to study the structure,performance difference and thermal degradation mechanism of the VDC-MA copolymer resin with or without thermal stabilizers.The specific research contents are as follows:First,the aqueous solution of methyl cellulose?MC?and hydroxypropyl methyl cellulose?HPMC?is used as the dispersion system,and dodecanoyl peroxide?LPO?is used as the initiator.Introduce MA monomer to suspension copolymerized with VDC monomer at 65?for 8h,VDC-MA copolymer resin particles with different monomer ratios are obtained through water washing,alcohol washing and drying.FTIR,¹H-NMR and Py-GCMS proved that VDC-MA random copolymerization copolymer resin was successfully prepared.The effects of different monomer ratios on the melting temperature,thermal stability,molecular weight,surface structure and film-forming properties VDC-MA copolymer resin were studied.The VDC-MA copolymer resin with a VDC content of 89.87.mol%was determined to be suitable for further thermoforming.Secondly,the heat stabilizer,plasticizer and toughening agent are blended,milled and hot pressed with VDC-MA copolymer resin to prepare VDC-MA copolymer resin film.The heat aging oven experiment proves that the organic-tin heat stabilizer has no heat stabilizing effect on the prepared VDC-MA copolymer resin,the calcium-zinc heat stabilizer will cause serious zinc-burning phenomenon.ESO,Ca St₂ and SBM have significantly improved the thermal stability of the resin.When the dosage of the three is 1.5:1.5:0.5,the thermal stability is the best,and the yellowing resistance time at 175?can reach 50min.When the amounts of plasticizer ATBC and toughener ACR-175P are 6-8%and 4-6%of VDC-MA resin films,the breaking elongation and tear strength of the copolymer resin film can be significantly improved.The oxygen permeability of the prepared VDC-MA copolymer resinFinally,thermal aging and thermal degradation kinetic analysis were used to explore the thermal degradation characteristics and mechanism of the prepared VDC-MA copolymer resin and the changes of thermal degradation process and mechanism of the thermal stabilizer on the resin film.GPC and FTIR indicate that thermal oxygen aging will cause inter-molecular chain crosslinking and may cause molecular chains to break,release HCl and produce a large amount of unsaturated C=C and O-H.DSC and DMA indicate that thermal oxygen aging will damge the crystallization ability of the resin,reduce the storage modulus of the resin and increase the Tg.The addition of thermal stabilizers ESO and Ca St₂ can significantly delay the effect of thermal oxygen aging on the copolymer resin.Furthermore,thermal degradation kinetic analysis finds that ESO and Ca St₂ can increase the first-stage degradation activation energy of VDC-MA copolymer resin from 158.3k J/mol to 169.3k J/mol.The Master-plot method shows that ESO and Ca St₂ can make VDC-The first-stage degradation mechanism of MA copolymer resin changed from D3 mechanism to D2 mechanism.