Preparation and Properties of Heat Resistant Polylactic Acid(PLA)/Nano-SiO2 Composite Filament

In order to improve the thermal properties of polylactic acid（PLA） filament,nano-SiO_2 was applied to mix with PLA,then they were spun as composite filament by melt-spinning.The dispersion of nano SiO_2 and the fracture surfaces of filaments were studied by scanning electron microscopy（SEM）.The properties of composite filament,such as orientation degree,mechanical properties,and surface friction properties,were analyzed.The thermal performances of composite filament were analyzed by differential scanning calorimetry（DSC） and thermo gravimetric analysis（TGA）.The results showed that the nano-SiO_2 modified by 5% KH-550 could disperse evenly and loosely in nano-scale,and 1 wt% and 3 wt% nano-SiO_2 dispersed throughout PLA evenly.As the quantity of nano-SiO_2 increased,the properties of composite filament,such as orientation degree,friction coefficient,thermal decomposition temperature,and glass transition temperature,increased more or less.The breaking tenacity increased when 1 wt% SiO_2 was added in PLA,but declined when 3 wt% SiO_2 was added.

Toddy Palm (Borassus Flabellifer) Fruit Fibre Bundles as Reinforcement in Polylactide (PLA) Composites: An Overview About Fibre and Composite Characteristics

Toddy palm fruit have an apparent density below 0.8 g/cm³and offer an interesting lightweight construction potential in polylactide(PLA)composites reinforced with 37 mass-%fibres.Single fibre bundles show similar mechanical properties compared with coir:tensile strength of 240 MPa,Young´s modulus of 3.8 GPa and an elongation at break of 31%.However,density and diameter(~50μm)of fruit fibre bundles are significantly lower.The compression moulded composites have a density of 0.9 g/cm³and achieved an unnotched Charpy impact strength of 12 kJ/m^(2),a tensile strength of 25 MPa,Young’s modulus of 1.9 GPa and an elongation at break of 9%.Due to the high porosity of the composites and the different stress-strain behaviour of fibre and matrix the fibre-reinforcement potential could not be fully used.Maximum stress of the composite was reached at the elongation at break of the PLA-matrix(~2%)while the fibre achieved its maximum stress at an elongation of~31%.After reaching the maximum stress of the composite,the fibres were pulled out from the matrix with low energy absorption,resulting in a decrease in stress and a limited reinforcement potential.Additionally,the study investigates whether an insect attack by the Asian fruit fly on the mesocarp has a significant influence on the mechanical fibre characteristics.The results have shown that only the rough surface of the fibre bundles is smoothed by insect infestation.The mechanical properties were not significantly affected.For this reason insect-infested fruits of the toddy palm,which are no longer suitable for food production,can be used for the production of sustainable composite materials.

Synthesis and Mechanical Properties of C/PLA 3D Printing Composites Based on Waste Rice Noodles

Spherical carbon particles were prepared by using waste Guilin rice noodles as raw materials.By blending the rice noodles based carbon(RC)powders with polylactic acid(PLA),A series of black RC/PLA 3D printing composites were synthesized and characterized.The mechanical testing result shows that the RC/PLA 3D printing composites display better mechanical properties than that of pure PLA.Moreover,the composite with carbon treated with high temperature carbonization has better impact strength.

Stereocompfexed Poiy(iactide) Composites toward Engineering Plastics with Superior Toughness, Heat Resistance and Anti-hydrolysis

Polyl(lactide),PLA,suffers from bitleness and low heat deflection temperature(HDT),which limits its application as an engineering plastic.In this work,poly(L-lactide)/poly(D-lactide)/ethylene-vinyl acetate glycidyl methacrylate random copolymer(PLLA/PDL A/EVM-GMA=1/1/x)composites were prepared by melt blending,and the in situ formed EVM-g PLA copolymers improved the compatibility between PLA and EVM-GMA.Subsequently,the blends were subjected to a two-step annealing process during compression molding,i.e.first annealing at 120℃ to rapidly form a certain amount of stereocomplex(sc)crystallites as nucleation sites,and then annealing at 200℃ to guide the formation of new sccrystallites.Both differential scanning calorimetry(DSC)and wide angle X-ray dffrction(WAXD)measurements confirmed the formation of highly stereocomplexed PLA products.Mechanical results showed that the PLLA/PDLA blend with 20 wt%of EVM-GMA had a notched impact strength up to 65 kJ/m2 and an elongation at break of 48%,while maintaining a tensile strength of 40 MPa.Meanwhile,dynamic mechanical analysis(DMA)and heat deflection tests showed that the PLA composite had an HDT up to 142℃ which is 90℃ higher than that of normal PLA products.Scanning electron microscopy(SEM)confirmed the fine dispersion of EVM-GMA particles,which facilitated to understand the toughening mechanism.Furthermore,the highly stereocomplexed PLA composites simultaneously exhibited excellent chemical and hydrolysis resistance.Therefore,these fascinating properties may extend the application range of sc PLA material as an engineering bioplastic.