Study On Preparation And Properties Of Acetylated Wood Flour Thermoplastic Composites

In recent years, increasing environmental pollution has enabled more people to payattention to develop environmental friendly materials. In this context, biologic materials havebecome a new emerging resource that is used to be prepared by composites of natural biomassand traditional plastic materials. It is the inevitable development trend of composite materials.Wood flour is one of the most abundant renewable resources in nature. Its development andapplication has become one of the hottest fields of biomass materials because of its widevariety of sources, low cost, minimum pollution to the environment.Acetylated wood flour (AWF) was prepared by an esterification process. The AWF wasthen blended with traditional plastic particles and environmental friendly plasticizers to preparecomposites by an extrusion molding process. Compared with the traditional Wood-PlasticComposites, we hope the hydrophobic property and heat resistance of composites can beimproved. It provides reliable path to use the biomass to prepare excellent performance,cost-effective and environmental friendly materials.The activation temperature, activation time, reaction time, temperature and feed ratioduring AWF preparation process were investigated. The optimized condition was obtained asfollows:(1) activation conditions: the mass ratio between glacial acetic acid and wood flourwas8/1, activation temperature was40℃, activation time was two hours;(2) esterificationconditions: the mass ratio between acetic anhydride and wood flour was4/1, the mass ratiobetween perchloric acid and wood flour was1/8, acetylation temperature was50℃, acetylationtime was two hours. The structure and properties of AWF were investigated by IR, XRD,13CNMR and thermal gravimetric analysis (TGA). The degree of crystallinity decreased and heatresistance improved.I prepared a series of blend composites of AWF with LDPE or PLA by a twin-screwextrusion and injection molding process. The mechanical properties, water resistance, thermal properties and morphology of blend composites were investigated by water absorptiondetermination, the contact angle and surface energy calculation, TGA, dynamic mechanicalthermalanalysis (DMA) and scanning electron microscopy (SEM). Compared with thetraditional WF blend composites, the AWF blend composites had better hydrophobic properties,which were reduced nearly80%. The thermal stability has also improved. During theprocessing, the mechanical tests showed that the AWF blend composites have lower viscosityand torque. DMA displayed that the AWF blend composites have a wide glass transitiontemperature range, indicating a relatively high flexibility of the material.We chose four environmental friendly plasticizers, glyceryl diacetate (GD), glyceryltriacetate (GT), triethyl citrate (TEC), and tributyl citrate (TBC), to improve the AWF/LDPEblend composites. After adding the plasticizers, the blend comosites processing performancewas improved to a certain extent. Through mechanical performance testing, the elongation atbreak of the materials was improved significantly when the plasticizer proportion exceeded20%. Particularly, the composites with20%glyceryl diacetate had better mechanical properties.The thermal properties showed that the plasticizers broadened blend composites’ glasstransition temperature range. The plasticity of the blend composites was improved. Byplasticizer migration study, tributyl citrate showed a good stability.