Study On The Structure And Properties Of PPC/PBSA Blends And Their Blown Film

Poly(propylene carbonate)(PPC)is a biodegradable material with good properties of barrier and ductility,and PPC has good application prospect in the field of green packaging.PPC is an amorphous polymer with a low glass transition temperature(Tg).The mechanical properties,dimensional stability and thermal stability of PPC are poor,which limits the application of PPC.Poly(butylene succinate-co-butylene adipate)(PBSA)has good mechanical properties and thermal stability,but poor barrier properties.The PPC/PBSA blends are prepared by melt blending to obtain materials with excellent properties for blown film processing.PPC/PBSA blends with different component ratios are prepared by melt blending.In order to improve the compatibility between PPC and PBSA and the melt strength of PPC/PBSA blends,the ethylene-methyl acrylate-glycidyl methacrylate(AX8900)is added to the PPC/PBSA blends as a reaction compatibilizer.The mechanical properties,thermal properties and rheological properties of the blends are tested,and the relationship between the structure and properties of the blends is analyzed.Infrared test results show that there is a hydrogen bond between PPC and PBSA,and the epoxy group of AX8900 can react with the hydroxyl and carboxyl groups of PPC and PBSA.The addition of PBSA and AX8900 greatly improves the mechanical properties and thermal properties of PPC.Compared with pure PPC,the mechanical properties of PPC/PBSA/0.5AX8900 blends are increased from 6.2 MPa to 9.71 MPa,and T_gincreased from 25.7 ^oC to 29.9 ^oC,and T_-5%increased from 242.8 ^oC to 262.9 ^oC.The microscopic morphology images of the blends show that the addition of AX8900 reduce the size of the dispersed phase of the PPC/PBSA blends and the phase interface is more blurred.The rheological results show that AX8900 can improve the compatibility of PPC/PBSA blends and increase the melt strength of the blends.In order to further improve the blown film processing performance of PPC/PBSA blends,the crystallization behavior of PBSA is studied.Two nucleating agents,surlyn resin and polybutylene succinate(PBS),are melt blended with PBSA to improve the crystallization performance of PBSA.The nuclear magnetic resonance spectroscopy(NMR)and differential scanning calorimetry(DSC)analysis show that the adipic acid-butanediol(BA)unit has a dual effect on the crystallization of PBSA.On the one hand,it reduces the regularity of the molecular chain to reduce the crystallinity.On the other hand,it improves the flexibility of the molecular chain to increase the crystallization rate.The addition of surlyn resin and PBS increases the crystallinity of PBSA,but reduces the crystallization speed of PBSA.This is because surlyn resin and PBS can provide nucleation sites to promote the crystallization of PBSA.The impurity effect of Surlyn resin and PBS hinders the movement of PBSA molecular chains into the crystal lattice.The initial crystallization temperature of PBSA/PBS(abbreviated as m PBSA)is increased from 34.15 ^oC of pure PBSA to 57.08 ^oC.The crystallization rate and crystallization temperature of the blend of PPC/m PBSA/AX8900(maintained at about 57 ^oC)are both significantly higher than the PPC/PBSA/AX8900 blend,indicating that PBS has a better nucleation effect on PBSA in the PPC/m PBSA/AX8900 blend,and the problem of difficulty in crystallization of PBSA during film blowing is solved.Surlyn resin and PBS have a nucleation effect on PBSA through the theoretical analysis of the Avrami model.The mechanical performance test shows that the mechanical properties of the PPC/m PBSA blends are better than those of the PPC/PBSA blends.Polarizing microscope(POM)tests show that the BA unit can change the spherulite morphology of PBSA.PBSA shows ring-banded spherulites while PBS is ordinary spherulites,and the addition of PBS can increase the isothermal crystallization temperature of PBSA.Single-layer and multi-layer films of PPC/PBSA blend system are prepared by extrusion blow molding technology.The properties of the mechanics,barrier,degradation and dimensional stability of the films are studied,and the stability of the film blowing process of the blends is analyzed.The morphology shows that AX8900 and m PBSA can improve the surface quality of the films.Due to the amorphous and low T_g of PPC,the molecular chain of PPC is easy to de-orientate,and the degree of orientation of pure PPC films is low.The addition of PBSA can introduce the crystalline region to fix the oriented molecular chain.The mechanical properties of the 70PPC/30PBSA/1AX8900 blend film are significantly improved,and the tensile strength of the 70PPC/30PBSA/1AX8900 blend film is 2.16 times that of pure PPC film.Since the addition of m PBSA and AX8900 to PPC increases the crystallinity of the blend and the interaction of molecular chains,the barrier properties and dimensional stability of the PPC/m PBSA/AX8900 blend films are better than those of PPC/PBSA films.Studies on the stability of the films blowing process shows that the films blowing process of the blends containing AX8900 and m PBSA can stabilize at a larger blow-up ratio(BUR)and lower helical instability(DHI).Due to the good interaction between layers of the three-layer films and the high-barrier PPC component in the films with the largest aspect ratio,the comprehensive mechanical properties and barrier properties of the three-layer films are better than single layer films.The interaction between the layers of the three-layer films can limit uneven swelling and rupture of the films,and the blowing process of the three-layer films is more stable.