Preparation And Performances Of Wheat Straw Powder/PBS Composites

In recent years, as the decrease of global fossil resources and worsening of "white pollution", renewable and biodegradable materials attract more and more attentions. Poly(butylene succinate)(PBS) has good mechanical properties, biodegradability and processing performance, which is the focus of hot topics in the study of biodegradable plastic material; however its application range is still limited for the high cost, relatively soft, and unsatisfied rigid requirements. Wheat straw powder is very rich in resources in our country, which has the advantages of cheap, renewable and biodegradable. As a filler of PBS, wheat straw powder will not only reduce costs, but also don’t affect the biodegradability. In this thesis, wheat straw powder/PBS composites were prepared by melt extrusion. The effects of Wheat straw powder modification, PBS modification and toughening material on mechanical properties, thermal properties and interfacial compatibility of wheat straw powder/PBS composites were studied. The main contents as following:1. A series of wheat straw powder/PBS composites were prepared by melt extrusion, and the effect of wheat straw powder content on the properties of composites was studied. The results showed that:the bending performance and heat distortion temperature of composites were improved with increasing wheat straw powder content; when wheat straw flour content was20wt%, the bending strength and bending elastic modulus increased by58.5%and234.2%, respectively, the heat distortion temperature improved by approximately10℃; but all of the tensile strength, elongation at break and impact strength of composites showed a downward trend. The compatibility between the straw powder and PBS substrate was poor, and the brittle fracture was emergence. In soil burial conditions, compared with pure PBS, the degradation rates of straw powder/PBS composites were significantly improved.2. Silane coupling agent modification on the properties of wheat straw powder/PBS composites was studied. The decline after the tensile strength and flexural strength of the composites first increased with the increase in the amount of coupling agent KH550, when KH550amount of2wt%, the tensile strength and flexural strength increased by12%and10.2%, respectively. The coupling treatment improved compatibility between the straw powder and PBS.3. The effect of radiation modification on the properties of wheat straw powder/PBS composites was studied. The tensile strength and flexural strength were enhanced with the increasing of radiation dosage, and then trend to be stable. When the fraction of TAIC was2wt%and the radiation dose was30kGy, the tensile strength and flexural strength increased by26%and39.8%, respectively. Impact strength increased firstly and then decreased, but elongation at break reduced continuously. The radiation modification made the heat distortion temperature increase6℃, and improved the adhesion of the interface between the straw powder and PBS.4. The effect of Poly (butylene adipate-co-butylene terephthalate) copolyesters (PBAT) on the properties of wheat straw powder/PBS composites was studied. SEM showed that a large number of microfibers appeared on impact fracture, which was due to the absorption of impact energy; this indicated a good compatibility was formed between PBAT and PBS. When the content of PBAT was30wt%, the elongation at break and impact strength improved57.8%and19.7%respectively, which indicated PBAT had a good toughening effect on composite materials. However, tensile strength, bending properties and heat distortion temperature were reducing with the addition of PBAT. The radiation modification improved mechanical properties and high-temperature decomposition rate of wheat straw powder/PBS/PBAT composites, and improved its heat distortion temperature about11℃.