Preparation And Properties Of Reactive Compatibilized PBS/PLA Blends

Polybutylene succinate(PBS)is a thermoplastic aliphatic polyester with biodegradability that can be synthesized from succinic acid and 1,4-butanediol.The biodegradation products of PBS are some small molecules,such as carbon dioxide and water etc.In addition,PBS has good tensile ductility,crystallization performance and heat resistance.However,its weaker mechanical strength and melt strength should be improved in order to broaden the application field of PBS materials.As another large variety of biodegradable polymers,polylactic acid(PLA)has high mechanical strength,good biocompatibility and processing performance.Obviously,the high ductility of PBS resin and the high strength of PLA resin are highly complementary in performance.In this paper,PBS/PLA blends were prepared by using melt-mixing method,and the component of PLA was used to enhance the PBS matrix.In order to improve the interfacial compatibility of the PBS/PLA blends,multifunctional epoxide chain extender ADR was used as a reactive compatibilizer.Effects of ADR addition on rheological behavior,processing thermal stability,microstructure,tensile properties,and crystallization behavior of the PBS/PLA blends were studied in detail.Finally,the reactive compatibilized PBS/PLA blends with excellent performances were prepared successfully.Effects of PLA content on melt fluidity,mechanical properties,micro-morphology and crystallization properties of the PBS/PLA blends were studied.It is found that melt mass flow rate(MFR)decreases with increasing the PLA content.In terms of mechanical properties,the addition of PLA could enhance the strength and rigidity of the PBS material,so that the tensile yield strength and tensile modulus of the PBS/PLA blends are improved.When the content of PLA is less than or equal to30 wt.%,the tensile yield strength,tensile modulus and elongation at break of the PBS/PLA blends increases simultaneously.The tensile yield strength,tensile modulus and elongation at break of neat PBS were 32.0 MPa,473.1 MPa and 282.5%,respectively.When the content of PLA increases to 30 wt.%,the tensile yield strength,tensile modulus and elongation at break increase to 34.4 MPa,610.8 MPa and 455.2%,respectively.However,when the content of PLA increases to 40 wt.%,serious PLA phase combination occurs in the PBS/PLA(60/40)blends,resulting in a dramatic decrease in elongation at break(11.3%).The crystallization results show that the PBS matrix in the blends has a semi-crystalline structure,and the dispersed phase of PLA has an amorphous structure.Impact of ADR addition on the processing thermal stability,tensile properties,micro-morphology,crystalline properties,rheological behavior and film blowing stability were studies.From the torque and melt mass flow rate results,it can be seen that the torque of the PBS/ADR and PBS/PLA/ADR systems increases and MFR decreases while ADR is introduced into these blending systems.It is attributed to the fact that the chain extension reaction between ADR and PBS or PBS/PLA in the blending system can significantly increase the molecular weight and viscosity of the polyesters.The tensile testing results show that the elongation at break of the PBS/PLA(60/40)specimen increases significantly with the addition of ADR.While the ADR addition increases from zero to 0.6 phr,the elongation at break increases from 11.3% to the maximum of 327.8%.Compared to the neat PBS sample,the PBS/PLA/ADR(60/40/x)samples with various ADR additions show a significant improvement on the tensile yield strength,tensile modulus and elongation at break.The tensile yield strength,tensile modulus and elongation at break of neat PBS samples are 32.0 MPa,473.1 MPa and 282.5%,respectively.As comparison,PBS/PLA/ADR(60/40/0.6)sample shows the best tensile performance,which tensile yield strength,tensile modulus and elongation at break reach to 39.8 MPa,853.0 MPa and 327.8%,respectively.This is due to the fact that the chain extension/branching reaction between the ADR and the PBS/PLA macromolecules could in-situ generate the PBS-ADR-PLA macromolecules which could enhance the interfacial compatibility of the PBS matrix and PLA dispersed phase.In addition,as can be seen from scanning electron microscope(SEM)observation,the PLA domain size becomes smaller with an improved interface while increasing the amount of ADR.According to the SEM observation on the internal morphology of the stretched specimene,it is found that a serious interface de-bonding exists during the stretching process of the binary PBS/PLA(60/40)sample,leading to a rapid development of the cracks.As a result,the cracks would cause the premature fracture behavior of the binary blend specimen during tensile testing.For the ternary PBS/PLA/ADR(60/40/x)sample,when it is subjected to the tensile stress,the PBS matrix yields first and absorbs a part of the energy.And then,the PLA dispersed particles begin to yield and large-scale orientated together with the PBS matrix without interface de-bonding due to the enhanced interfacial adhesion.The continuously formed orientated and fibrous PLA dispersed phase structure can greatly improve the ability of the ternary specimen to terminate the crazes and the microcracks development.As a result,the tensile ductility of the compatibilized PBS/PLA/ADR(60/40/x)specimens can reach and even exceed to the tensile ductility of the neat PBS specimen.The capillary rheological results show that the apparent viscosity of the PBS/PLA(60/40)blend system is more sensitive to the change of shear rate,and the blend melt is a pseudoplastic fluid.As the amount of ADR increases,the pseudoplasticity of the melt tends to increase,indicating that the chain extender/branched macromolecules in the melt of the blend continuously increase.In addition,the increase of temperature will lead the fluidity of the melt increase to a certain extent and reduce the apparent viscosity of the melt.However,the sensitivity of apparent viscosity to temperature changes is significantly weaker than the shear rate changes.The blowing film test presents that PBS and binary PBS/PLA(60/40)blends show a poor film blowing stability.However,the chain extension/branching reaction of ADR enhances the melt viscosity and melt strength of the PBS/PLA/ADR(60/40/0.6)blend,and the film blowing stability is significantly improved.