The Preparation Of Oriented PBA Films And Crystallization Behavior

Aliphatic polyesters constitute the family of synthetic polymers with major applications as degradable materials,biodegradable polymers have a wide variety of applications in biomedical engineering and environmental protection owing to their environmental and ecological advantages,stimulates numerous studies on the properties and structure characterization of biodegradable polyesters.PBA is a typical linear polyester material obtained by condensation polymerization of adipic acid and butanediol,and it is a polycrystalline polymer with two crystal forms of a and ?.In this paper,the oriented PBA films were prepared by transfer-friction method for the first time.The properties of PBA films were characterized by polarizing microscope,XRD,polarized infrared,transmission electron microscope and Grazing incidence X-ray diffraction.The surface of PBA film prepared by transfer-friction method is uneven and has great roughness.The chain direction of PBA is parallel to the friction direction.Temperature and friction rate have great influence on the crystal form and orientation of PBA films.Under the condition of constant friction rate,PBA film changes from ?crystal to a crystal with the increase of temperature,which is due to the higher equilibrium melting point temperature of a crystal and the more stable thermodynamics.The increase of temperature is accompanied by the decrease of orientation.This is due to the increase of temperature,which leads to the increase of the ability of PBA molecular chain to move.The orderly arranged molecular chain in one direction becomes disordered due to the molecular thermal movement,which leads to the decrease of orientation.At the same temperature,the orientation degree of PBA film increases with the increase of friction rate.It is worth noting that at 30 ?-35 ?,the increase of friction rate is beneficial to the transformation of PBA ? to ?.The phase transition temperature range of PBA is 45-50? by in-situ XRD and in-situ FTIR.This is higher than the normal crystallization of ? phase transition temperature range of 42-47 ?.This is due to the fact that orientation has a fixed effect on the molecular chain of PBA,which delays the phase transition behavior of PBA.