Mechanical And Thermal Properties Of Bamboo And High Density Polyethylene(HDPE) Composites With Heat-treated Bamboo Flour

The objective of this paper is to study the heat-treated bamboo flour reinforced high densityPolyethylene（HDPE） composites. The physical, mechanical and chemical properties of the heat-treatedbamboo with100℃,150℃and180℃for2hours were investigated to support to explain the effects ofheat treatment temperature on the mechanical and thermal properties of the resulted composites. Fick’ssecond law was introduced to calculate the diffusion coefficient of the composites. Dynamic MechanicalAnalyzer （DMA）, Thermo-gravimetric Analyzer （TG） and Differential Scanning Calorimetry （DSC）were used to acquire the viscoelasticity, thermal decomposition kinetic properties and the crystallizationkinetic properties of the composites. The results showed that:（1） With the heat-treated temperature increasing, the content of holocellulose decreased slightlyfrom76.14%to74.6%, the content of lignin increased. Simultaneously, Air-dry density, equilibriummoisture content of bamboo reduced from0.74g/cm³to0.73g/cm³and from8.01%to6.03%,respectively. Flexure and tensile strength also decreased （from132.1MPa to112.7MPa, from177.1MPato139.6MPa, respectively）. Tensile modulus declined （7014MPa to6824MPa） and compress strengthgradually reduced from71.49MPa to67.87MPa. However, flexure modulus increased from9.47GPa to10.84GPa.（2） with the heat-treated temperature increasing, the effect of heat-treated temperature had notdistinguished influence on the mechanical properties of the composites. The properties of heat-treatedbamboo flour/HDPE composites improved except the impact strength and the tensile strain with thebamboo flour loading level increasing. The values of flexure strength of100℃treated bamboo flourreinforced HDPE composites was about49MPa, which was1.4times as that of HDPE. Additionally, theflexure and tensile modulus of the composites were2.2and2.8higher than that of HDPE.（2） The diffusion coefficient （Dm）of the composites were in a range of0.5⁵.6×10^-9cm²/s. Values ofDmdecreased with the heat-treated temperature increasing, while values of Dmincreased with thebamboo flour loading increasing. The Dmvalue of40wt%bamboo flour/HDPE composites with100℃expressed the maximum, which is5.53×10^-9cm²/s.（3） Storage modulus of heat-treated bamboo decreased with the temperature increases. Between thetesting temperatures of110℃and160℃, loss modulus of bamboo with150℃and180℃were distinguished lower than that of bamboo treated by100℃. Storage modulus and loss modulus of thecomposites were both higher than that of HDPE. Heat-treated temperature had significantly influence onthe resulted composites. Storage modulus decreased with the heat-treated temperature increasing.Nevertheless, storage modulus and loss modulus of the composites increased with the bamboo flourloading increasing.（4） Thermal decomposition of bamboo flours and the resulted composites mainly occurred within atemperature range of245℃³54℃and307℃⁴83℃, respectively. The Eavalues of bamboo floursvaried from161to177kJ/mol and increased as flour teat-treated temperatures increased. However, theEavalues of the composites decreased from the236kJ/mol to226kJ/mol as heat-treated temperatureincreased.（5） Neat HDPE and heat-treated bamboo flour/HDPE blends reflected a similar trend, thecrystallinity occurred within a range of106℃¹26℃. Effected by the cooling rates increasing, thecrystallization peak move to higher testing temperature and the shape broadened. Crystal growthprimarily relied on the three-dimensional method. Bamboo flour and coupling agent could increase thecrystallization rate of HDPE and enhance the crystal integrity.