Study On Modification And Properties Of LDPE/EVA Blends With Different Sizes Potassium Titanate Whiskers

Due to its chemical stability,low cost,ease of processing,and recyclability,Low density polyethylene(LDPE)occupies a large share of global plastic production and is widely used in packaging,consumer goods,agriculture,and electronics.However,LDPE suffers from poor impact and puncture resistance,low elongation at break,poor resistance to environmental stress cracking,low surface hardness,brittleness and deformability.On this basis,LDPE was firstly modified with ethylene vinyl acetate copolymer(EVA,55%VA content)elastomer to make it rubber-like elasticity and toughness,and then surface-treated potassium titanate whiskers with different sizes(micron-scale potassium titanate whiskers mPTWs and nanoscale potassium titanate whiskers nPTWs)were introduced as reinforcing phases into the blend matrix LDPE/EVA.Eventually LDPE/EVA/mPTWs composites and LDPE/EVA/nPTWs nanocomposites were prepared by melt blending.The effects of different mass ratios of LDPE and EVA on the properties of the blends were investigated.The surface treatment effects of mPTWs modified by silane coupling agent KH570 and nPTWs modified with stearic acid were evaluated by scanning electron microscopy(SEM),Fourier infrared spectroscopy(FTIR)and contact angle test,respectively.The effects of mPTWs and nPTWs contents on the mechanical,tribological,and thermal properties of LDPE/EVA/mPTWs composites and LDPE/EVA/nPTWs nanocomposites were focused by using various analytical techniques such as thermogravimetric analysis(TGA),differential scanning calorimetry(DSC),electronic universal testing machine,shore hardness tester and multi-specimen test machine.Among the LDPE/EVA blends with different mass ratios,the LDPE-rich blends had a finer and more uniform distribution than the EVA-rich blends.The elongation at break of the blends increased with increasing EVA content,while the tensile strength decreased with increasing EVA content.When the mass ratio of LDPE and EVA was1:1,a clear co-continuous morphology was observed,indicating better compatibility.The thermal stability of the blend was improved and the elongation at break raised significantly,displaying excellent toughness,but the tensile strength was low.Therefore,the blend LDPE/EVA with the same mass ratio was chosen as the matrix for the subsequent study of the reinforcement system.The mPTWs treated with KH570 had a water contact angle of 138±1°,exhibiting good dispersion,hydrophobicity,and a stronger bond with the matrix LDPE/EVA interface.The addition of mPTWs not only improved the mechanical properties of the composites,but also further enhanced the tribological properties of the composites.At 25wt%mPTWs,the tensile and flexural modulus increased to 87MPa and 81 MPa respectively,and the elasticity remained almost unchanged during ten cycles of stretching.When the mPTWs content was 20wt%,the composite reached its maximum hardness of 43.4 HD,the average friction coefficient was reduced to0.3737,the wear rate was only 0.009wt%,a maximum reduction of 80.44%,and the friction stability was significantly improved.In addition,the thermal stability of the composites was also elevated.The 10%mass loss temperature(T_10%)and 50%mass loss temperature(T_50%)of the composite were heightened by 75?and 12?separately when 30wt%of mPTWs were added.The nPTWs modified by stearic acid changed from hydrophilic to hydrophobic and the water contact angle increased to 141±1°.The small amount of nPTWs helps to improve the mechanical properties and friction resistance of the nanocomposites.When 2wt%nPTWs were introduced into the blend matrix LDPE/EVA,the nanocomposites showed a 36%increase in tensile strength,22%growth in elongation at break,71%rise in tensile modulus,72%enhancement in flexural modulus,maximum hardness of 35.0 HD and great elasticity after ten cycles of stretching.The average friction coefficient of the nanocomposites was decreased substantially to0.1712,a decrease of 53%,and a wear rate of 0.017wt%.Moreover,the addition of nPTWs promoted the thermal stability of the nanocomposites.The nanocomposites containing 10wt%nPTWs manifested an increase of 70?in the second weight loss and also a slight increase of 6?at T_50%.This demonstrated a consistency between mechanical,tribological and thermal properties.