Effect Of Surface Functional Modifications Of Wheat Straw On The Properties Of Thermoplastic Starch

Because of limited global petroleum resources and growing environmental awareness, biodegradable polymeric materials have been developed rapidly in recent years. Wheat straw(WS) residues are agricultural byproducts, and large amounts of WS are generated globally every year after harvesting. Starch is one of the most promising candidates for biodegradable plastic production, because it is a degradable, cheap and abundant natural polymer. However, poor mechanical properties and bad water resistance limit the starch plastics applications. Using straw as a reinforcer, which can effectively improve the performance of thermoplastic starch, and provide a new way for crop waste disposal.In this paper,first and foremost, untreated WS was directly blended with thermoplastic starch(TPS), but the enhancement effect was poor. Then the surface pretreatment was considered: WS was converted to oxidized WS(OWS), and used as a reinforcement to prepare OWS/TPS composites. Achieve the goal of reinforced thermoplastic starch composites through the esterification crosslinking reaction of OWS with starch molecules. However, the problem of insufficient tensile toughness and impact resistance still limited the development of the production. In order to solve the the problem, different anhydride esterification reaction methods were adopted in the preparation of thermoplastic starch composites. Specfic work carried out in this paper is follows:(1) Study on TPS reinforced with WS: untreated WS reinforced thermoplastic starch(TPS) were prepared by physical blending method. WS/TPS composites were investigated by mechanical properties, thermal properties, rheological properties and water resistance properties. The results showed that WS/TPS material tensile strength increased first and then decreased with the increase of WS contents. When WS content reached 1%, the tensile strength reached the maximum value of 6.89 MPa. The impact strength decreases with the increase of the content of WS. WS can improve the thermal stability of the thermoplastic starch and can slightly improve the maximum decomposition rate of starch. WS/TPS were more difficult to process relative to the TPS. With the increase of the content of the WS its liquidity worse and worse under heat shearing action. The thermoplastic starch water resistance were improved with the increase of cellulose contents while the fluidity of TPS would be decreased with increasing WS content.(2) Study on TPS reinforced with OWS: OWS was prepared by the oxidation of WS with different ratio of Na IO4, and OWS/TPS composites were prepared using OWS as a reinforcement. OWS/TPS composites were investigated by mechanical properties, thermal properties, rheological properties and water resistance properties and so on. Research of wheat straw fiber content, oxidation degree effect on the properties of thermoplastic starch composites. The results showed that when concentration of Na IO4 was 0.045 mol/L, and OWS content was 1wt%, the tensile strength of OWS/TPS was the best of 7.66 MPa, the elongation at break was only 19.87%.(3) Study on MA-WS&ITA-WS&CTA-WS/TPS starch-based plastics: WS was modified by using maleic anhydride, itaconic acid anhydride and citraconic anhydride, respectively. The MA-WS&ITA-WS&CTA-WS/TPS composites were investigated by mechanical properties, thermal properties, rheological properties and water resistance properties. Along with the increase acid anhydride content system tensile strength and elongation at break first increased and then decreased, water resistance increased while processing flow properties decreased.(4) Study on PA-WS&SA-WS/TPS starch-based plastics: WS was modified by using propanoic anhydride and succinic anhydride, respectively. PA-WS&SA-WS/TPS composites were investigated by mechanical properties, thermal properties, rheological properties and water resistance properties. Along with the increase acid anhydride content system tensile strength and elongation at break first increased and then decreased, water resistance and processing flow properties decreased.(5) Study on MAA-WS/TPS starch-based plastics: WS was modified by using methacrylic anhydride. MAA-WS/TPS composites were investigated by mechanical properties, thermal properties, rheological properties and water resistance properties. Along with the increase acid anhydride content system tensile strength and elongation at break first increased and then decreased, water resistance and processing flow properties decreased.