Study On Characterization Of Typical Biomass Plastic Composites

With the development of society, petrochemical energy gets shorter and shorter, and environmental pollution gets worse. Biomass and reprocessed plastic attract more attentions in the world. With economy development, environment improvement and forest protection, It’s significance to study and develop the usage of biomass and reprocessed plastic, as well as building waste resources comprehensive utilization system. Based on the development state of processing technique in biomass/plastic composite field, the paper studies four kinds of typical biomasses in China:rice husk, cotton stalk, wheat straw, and peanut shell, and deeply researches the processing technique of these biomass/plastic composites. The technique uses biomass and waste plastics as the principal raw material. The products are widely used in building materials, packaging materials, decorative material and gardens. The products can be recycled, and have no secondary pollution. So environmental problems caused by agricultural residues and waste plastic can be avoided.Firstly, modern measuring and test techniques as FTTR、DSC、SEM and element analysis are used to study the basic characteristics of the biomass. Parameters of these characteristic are got. The surface free energy affected by modified processing for biomass is quantitatively described. As the results show, the four biomasses have similar thermal properties. their thermal properties are stable under 200℃. Biomass powder stability can be improved when adding calcium carbonate superfine powder. Microstructure of the biomass is complex. They have debris, bunchiness, particle structure. There are functional groups as hydroxy, alkyl, carbonyl and acetal in associated state which are strong hydrophilic. Modified biomass can change surface functional groups, which affects the surface free energy, polar components and nonpolar components decrease. Surface free energy decrease, hydrophilicity gets weak.High efficient mixing mill, taper double-screw extruder are used to study the key processing techniques for biomass/plastic composite. Researches are done between principal components and the composite properties. The results show that impact strength and tensile strength decrease rapidly with the biomass powder quantity increases. When biomass powder quantity is up to 20%-40%, impact strength decreases to 59%-65%, tensile strength decreases 60%y72%. But continually increasing biomass powder, the trends of impact strength and tensile strength go down slowly. As the increasing of biomass powder, bending strength goes up firstly, and then goes down. Among the composites from the four biomasses, their mechanical properties are:cotton stalk>rice husk> wheat straw>peanut shell.The density and water absorption of the composites increase as biomass powder quantity increases. Their densities in descending order are:peanut shell> wheat straw> rice husk>cotton stalk. With the coupling reagent or compatilizer increase, mechanical properties of the composites go up firstly, then go down. When silane coupling agent is 3%, compatilizer is 9%～12%, mechanical properties of the composite reach the maximum. The density of biomass/plastic composite is not affected by the amount of coupling reagent or compatilizer. Water absorption of the composites decreases with the adding of coupling reagent or compatilizer.The DSC method is used to study the crystallization behavior of the fusion during biomass/plastic composite processing. Nonisothermal crystallization behavior and isothermal crystallization behavior of rice husk/HDPE composite are described quantitatively. The results show Nonisothermal crystallization behavior cooling rate increases, crystallization period shortens, enthalpy increases, relative crystallinity increases. Among the composites, the rice husk power can enhance crystallization behavior. Method of Mo Zhishen is used to show their better linear relation. At the same crystallinity, crystallization rates are:MS46 >MS28>HDPE. For rice husk/HDPE composite, as the temperature goes up, crystal nucleus doesn’t form easily, or crystal nucleus isn’t stable, thus crystallization rate decreases, crystallization time increases. Adding rice husk powder can increase crystallization rate which shows rice husk powder has obvious function of heterogeneous nucleation. Avrami equation is also used to processing the data. Avrami index of pure HDPE and the composite is betweenl.12～1.28. Therefore it can be seen rice husk powder enhance the crystallization, but don’t change the way of nucleation.Torque rheometer is used to study the rheological properties of biomass/plastic composites. With the increasing of rice husk powder,torque increases, flowing gets worse. When rice husk powder is 60%, torque reaches the maximum. Continuously increasing rice husk powder, the mixture slips in the chamber, balance torque drops rapidly. The mixture can’t mix homogeneously. For certain amount of rice husk powder, torque gradually decreases with the temperature increases, and flowing property increases. However, if the temperature is very high, rice husk powder will be slightly burned, which can influence bending between the rice husk powder and polythene. The function of lubricate 604 and 613 are almost the same.604 and 613 are alternative. Experiments show flowing property and combination property can both be guaranteed when the lubricate is 2%.Finally aging characteristics and wear-resisting properties of the four kinds of biomass/plastic composites are discussed. After aging test, the color of the composites fades, and color aberration increases. For the same amount of biomasses, color fading levels are:cotton stalk<wheat straw<peanut shell< rice husk. Wear rates of the composites go down firstly, then go up with the increasing of biomasses. The wear rates of the composites are:cotton stalk> rice husk> wheat straw> peanut shell. When CaCO3、Al2O3、SiO2 are added in the composites, wear rate decreases, thus abrasive resistance enhances. Their wear rates are CaCO3>Al2O3>SiO2.