Preparation And Properties Of Poly(Ethyleneglycol-co-cyclohexane-1,4-dimetha-nol-terephthalate)/Poly Glycolic Acid(PETG/PGA)、Polylactic Acid/Polyglycolic Acid (PLA/PGA) Blends

The production of plastics has brought great convenience to human beings,and people cannot live without plastics in their daily life.However,the synthesis rate of plastics is much higher than the degradation rate of plastics,and the accumulation of plastics is becoming more and more serious,and the problem of reprocessing has not been solved.The way to solve this problem is to develop environmentally friendly plastics,that is,to develop and use plastics that are completely degradable and can be recycled twice,which can meet the needs of people’s production and life without creating plastic disposal.Poly（lactic acid）（PLA）and poly（ethylene terephthalate-1,4-cyclohexanedimethanol）（PETG）,which are both environmentally friendly and practical,are among the most promising environmentally friendly plastics.In addition,PLA and PETG have good transparency,biocompatibility,and easy processing and molding,so they are widely used in agriculture,medical devices,packaging,and everyday products.However,in order to better exploit the potential of PLA and PETG and further broaden their applications,the mechanical properties,heat resistance,and barrier properties of PLA and PETG need to be further improved.In this paper,PLA and PETG were modified by blending to address the above issues.The high modulus,high strength and high barrier fully biodegradable material polyhydroxyacetic acid（PGA）was melt blended with PLA and PETG respectively to increase their strength.In addition,the PGA was modified by adding a multiple epoxy chain extender（ADR）for chain expansion and PETG/PGA for capacity enhancement.The effects of PGA on PLA and PETG,and the effects of ADR addition on PGA and PETG/PGA blends were studied.The specific main studies are as follows.（1）PGA and ADR were used as raw materials,and PGA/ADR blends with different ratios were melt blended and injection molded.The rheological properties,chain spreading effect,mechanical properties and crystallization properties of the samples were investigated.m FR showed that the addition of ADR had a significant viscosity increasing effect on PGA and effectively reduced the MFR.torque showed that the torque value of PGA gradually increased with the increase of ADR,which said that the addition of ADR well spreading the PGA and increasing the molecular weight of PGA.The tensile results showed that the elongation at break increased from 9.82%to 57.16%for PGA and the tensile modulus increased by 30.5%after the addition of 0.9 phr ADR.DSC and XRD showed that the crystalline structure of PGA did not change due to the addition of ADR,but its crystallinity decreased.（2）The mechanical properties of PETG were improved by melt blending,using PGA as the reinforcing component.The effects of PGA on the tensile properties,microstructure,crystallinity,heat resistance,and melt flow rate of PETG/PGA blends were investigated.It was found that PGA significantly enhanced the tensile properties and heat resistance of the PETG matrix.The tensile yield strength and tensile modulus of PETG/PGA（65/35）samples increased from 44.38 MPa/1075.56 MPa of pure PETG to 48.4 MPa/1509.38 MPa,respectively,when the PGA content was increased to35 wt.%,and the VST increased from 81.0°C to 99.2°C.However,the tensile toughness of PETG/PGA（65/35）samples decreased sharply due to the poor interfacial compatibility of the PETG matrix and PGA dispersed phases.In addition,the high melt fluidity of PGA also greatly increases the MFR of PETG/PGA blends,which is not favorable for their processing by common processing techniques such as extrusion,blown film,and thermoforming.In order to improve the interfacial compatibility and rheological properties of PETG/PGA（65/35）blends,ADR was introduced as a reactive modifier to improve the properties of the blends.Torsional results showed that the melt viscosity of PETG/PGA blends increased significantly with increasing ADR content.As expected,the MFR values decreased with increasing ADR content.In addition,SEM and TEM showed that there was a significant reactive bulking effect of ADR,which increased the interfacial adhesion in PETG/PGA while greatly reducing the size of the PGA dispersed phase.Meanwhile,the addition of ADR significantly improved the tensile toughness of PETG/PGA（65/35）blends.When 0.9 phr ADR was added,the elongation at break of PETG/PGA（65/35）blends increased from 11.8%to 160.8%.However,the tensile modulus of PETG/PGA/ADR（65/35/x）blends decreased slightly with increasing ADR content.DSC and WAXD analyses showed that the PETG matrix had an amorphous structure and the PGA dispersed phase had a semi-crystalline structure.In addition,the crystallinity of PGA gradually decreased with the increase of ADR content,which reduced the enhancement of the heat resistance of PETG/PGA/ADR（65/35/x）samples by PGA.In conclusion,the microscopic morphology,mechanical properties and rheological properties of PETG/PGA blends can be effectively adjusted and changed by reasonably regulating the ADR content to better meet the requirements of different applications.（3）PLA/PGA blends with different ratios were melt blended and injection molded.The processability,mechanical properties,microscopic morphology,crystalline properties,heat resistance and barrier properties of the samples were investigated.MFR and torque showed that the PLA/PGA blends had good processability fluidity and sufficient processability time,respectively.Tensile,flexural,and DMA showed that the addition of rigid PGA effectively improved the tensile properties,flexural properties,and energy storage modulus of PLA.Tensile strength and tensile modulus were improved by 16.1%and 22.4%,respectively.The bending strength and bending modulus were increased by14.7%and 14.8%,respectively.Compared with tensile and flexural,the dynamic mechanical effect of PLA blends was more significant.When PGA was added at 40 wt.%,the energy storage modulus of the blends increased by 88.4%at 20°C and 322%at 120°C.SEM showed that the particle size of the PGA dispersed phase gradually became larger with the increase of PGA content,and phase merging occurred.d SC and XRD showed that the addition of PGA did not affect the crystalline properties of the PLA matrix.opc and WVP results showed that the barrier properties of PLA blends were significantly improved with the addition of highly crystalline PGA,increasing the oxygen and water vapor transmission paths.When the content of PGA was 40 wt.%,the OPC and WVP of PLA blends decreased to 0.25×10^-11cm³·cm/cm²·s·cm Hg and 1.81×10^-14g·cm/cm²·s,respectively,which were only 14%and 25.9%of PLA.