Preparation,Morphology And Properties Of The PHB/PBS Blends

Poly butylene succinate(PBS)is a typical aliphatic biodegradable polyester with excellent mechanical properties,good heat resistance and processability.PBS can be widely used as degradable packaging polymer materials and degradable biomedical material,etc.On the other hand,PBS has high brittleness,low elongation at break and low intrinsic viscosity,which is not conducive to molding processing and hinders the development of PBS applications.In addition to its good biodegradability,poly hydroxyl butyrate(PHB)also has high toughness and good biocompatibility.Based on the chemical and physical properties of PBS and PHB,combined with the blending modification principle of blends,PHB/PBS blends were prepared and their morphology and properties were studied systematically.These results lay the foundation for the preparation of high performance PBS alloy materials.The results of mechanical properties and morphological structure characterization showed that appropriate PHB had a certain toughening and strengthening effect on the PHB/PBS blends.With the increase of PHB,the tensile strength of the alloy increased from22.6 MPa to 38.5 MPa,and the impact strength increased from 5.7 kJ/m~2 to 43.1 kJ/m~2.The elongation at break and the flexural strength of the blends reached the maximum when the content of PHB was 40%,which were 1052%and 22.5 MPa,respectively.The impact fracture mode of pure PBS was brittle fracture.With the increase of PHB,the fracture mode gradually changed to ductile fracture.The glass transition temperature,crystallization melting behavior,non-isothermal crystallization kinetics and crystal morphology of PHB/PBS alloy showed that PBS and PHB were thermodynamic compatible systems.All blends had a glass transition temperature,a heating melting peak and a cooling crystallization peak.With the increase of PHB,the spherulite size was reduced and the zonal spherulites were easily formed.The relative crystallinity also decreased.At the same time,the semi-crystallization time became shorter,the crystallization rate constant increased,and the crystallization activation energy increased gradually.All these indicated that the crystallization rate of the blends improved.The results of the crystal structure and crystallinity of the PHB/PBS alloy showed that there were no crystalline transformations in the alloys,all of which were monoclinic.With the increase of PHB,the crystallinity of the blend decreased.The non-isothermal thermal decomposition processes of PHB/PBS blends were studied by using a thermogravimetric analysis in nitrogen.The results showed that the thermal degradation was a major thermal decomposition process and a first order reaction.With the increase of PHB,the temperature corresponding to the weight loss of 2wt.%and 5wt.%increased,that is,the thermal stability of the blends increased gradually.In the viscous flow state,with the increase of PHB,the viscosity and the zero shear viscosity of the blends increased rapidly.The pseudo-plasticity of the melt became more obvious,and the viscoelasticity of the melt was dominated by the viscous response.During the transition from the glassy state to the hyper elastic state,the storage modulus of the blends decreased,the loss modulus increased,and the internal friction peak temperature(glass transition temperature)decreased gradually.The effects of different mold temperatures on the impact properties,tensile properties and melting properties of PHB/PBS polymer alloys showed that the faster the cooling rate of the material,the smaller the crystal size formed,the better the toughness and tensile strength of the alloy samples when the mold temperature was 30°C.With the increase of mold temperature,the recrystallization enthalpy and melting enthalpy of PHB/PBS alloys increased gradually.The effects of UV aging time on the impact properties of PHB/PBS alloys showed that the longer the UV aging cycle,the less pronounced the change in performance.The effects of soil aging time on the degradation rate of PHB/PBS alloys showed that:With the prolonged burial time,the degradation of the alloy occurred to a certain extent,and the degradation of PBS was faster than that of PHB.After 8 weeks,the weight loss rate of pure PBS reached 1.96%,the weight loss rate of pure PHB reached 1.05%,and the weight loss rate of all alloys was somewhere in between.