Study On Foaming Property Of Poly(Propylene Carbonate) Blend System

Poly(propylene carbonate)is a white or transparent aliphatic polyester,synthetic process with CO2 and propylene oxide(PO)as raw material,and it has good biocompatibility and biodegradability.Some flexible groups on the main chain of PPC increases the flexibility of the molecular chains,such as ether bond,resulting in glass transition temperature close to room temperature,PPC dimensional stability is poor when temperature over 40?,the exploratory experiment shows that the shrinkage of PPC foam is very serious at room temperature,The instantaneous expansion ratio is about 46 times and decreases to 4 times after two weeks,which is mainly due to the lower modulus of PPC at room temperature,the cell wall has a good deformability at room temperature,leading to the speed of blowing agent escaping from polymer matrix is faster than air into cell,bubble shrink caused by internal pressure is less than the external environment,which greatly limits the application of PPC foam.In this paper,PPC/nano-Si02,PPC/MDI,PPC/PBAT(MDI)blends are used to improve the shrinkage of PPC foams,and the shrinkage phenomenon was quantified to the shrinkage rate,to study the effect of different systems on foaming Performance,thermal properties,foaming properties and shrinkage:1.In the PPC/nano-SiO2 blends,the introduction of nano-SiO2 increases the nucleation point in the system,with the increase of the nano-SiO2 content,the average diameter of the cell decreases and the cell density increases gradually,the addition of appropriate amount of nano-SiO2 can form a percolation network with PPC,the network can improve the degradation of PPC at high temperature and increase the viscoelasticity of the polymer melt,inhibit the cell merging and stabilize the cell structure.However,adding nano-SiO2 has no significant effect on the thermal properties of PPC and the shrinkage after foaming,the shrinkage rate at room temperature is above 90%.2.In the PPC/MDI blends,the molecular weight,storage modulus,loss modulus,complex viscosity and glass transition temperature of PPC are significantly improved by the chain extension of MDI with PPC,the improved melt strength also makes foaming properties of PPC enhanced at high temperature,the shrinkage of PPC foam products is improved after adding MDI at the same time,but the final shrinkage rate of PPC foam products is still high,the shrinkage rate at room temperature is above 60%.3.In the PPC/PBAT blends,the compatibility between PPC and PBAT is poor,the viscoelasticity of PPC/PBAT blends is between the two matrix components,and the viscoelasticity of PPC is larger,the viscoelasticity of PPC/PBAT blend increased with the increase of PPC content,PPC and PBAT after blending has influence on their own thermal properties,with the increase of PBAT content,the glass transition temperature of PPC increases,and the melting point of PBAT increases with the increase of PPC content,moreover,the crystallization temperature and the crystallization enthalpy decreases with the increase of PPC content,and there is more foaming area and less foaming ratio when PPC/PBAT blends system is bicontinuous phase.4.In the PPC/PBAT/MDI blends,with the increase of MDI content,the interfacial tension of PPC and PBAT decreased,the shape of cell become gradually complete,the improvement of interfacial compatibility of PPC/PBAT blends slows down the escape rate of the blowing agent from the PPC matrix,the escape velocity of the foaming agent from PPC matrix is slowed down because the crystallinity areas of PBAT and the increase of Molecular chain rigidity by adding MDI,in addition,the dimensional stability of the foamed sample are increased,the shrinkage rate at room temperature is winhin 5%and the expansion ratio could maintain at 20.In order to investigate the effect of increasing the modulus of the polymer matrix resin and reducing the shrinkage rate of the foaming agent from the cell to the shrinkage of the PPC foam,the effects of the modulus and diffusion coefficient of the three blends on the shrinkage of the PPC were analyzed.Compared to control gas diffusion velocity in the PPC,the strength of the polymer matrix is more pronounced to the shrinkage of PPC.