Study On The Properties Of Rice Straw Reinforced Linear Low Density Polyethylene Composites

Rice straw has the advantages of wide sources,low cost,environmental friendliness,and natural biodegradability.Its main components are similar to wood,and thus it can be used as an advantageous supplement for wood raw materials in the preparation of composites.Now,the main method to dispose rice straw is burning,which cause environmental pollution and resource waste.In addition,the waste plastic film from agriculture causes the damage to local ecological environment.In this study,in order to protect the environment and make full use of bio-resources,the composite with rice straw as the reinforcement and linear low-density polyethylene(LLDPE)as the matrix was developed.A method of wrapping long straw stem and then hot pressing molding was explored.The best processing temperature and the mass percent of rice straw was focused to study their influence on the properties of composites.The new molding process was further improved by changing the structures of straw stem.The obtained results provide support for utilizing agricultural straw.1.Rice straw composites were prepared by extrusion method.Roll the long stem of rice straw together with linear low-density polyethylene film,and then melt the straw/LLDPE mixture and extrude the lumber by using a single screw extruder.The effects of processing temperature(120℃,140℃ and 160℃)on the mechanical properties of the straw stem/LLDPE composite were studied.The results show that the best properties were obtained at 140℃.Then at the processing temperature of 140℃,the straw particle/LLDPE composites were prepared by the processing of mixing,melt compounding,granulating,and extruding.The results show that the mechanical properties of extruded straw particle/LLDPE composite were better when the proportion of rice straw was 40%.2.Rice straw/LLDPE composite were prepared by hot pressing method.Using linear low-density polyethylene film wrapped rice straw long stem or particles and then hot-pressed.The results showed that the mechanical properties of rice straw particle/LLDPE composite were inferior to those of the composite with rice straw long stems.When the content of rice straw was in the range of 50%-60%,the mechanical properties of the rice straw stem/LLDPE composite were better than other contents.When the content of MAPE decreased from 5%to 3%,the mechanical properties of rice straw stem/LLDPE composite accordingly decreased.3.Under the conditions of straw mass percent of 60%and processing temperature of 140℃,the extruded straw particle/LLDPE composites and hot-pressed straw stem/LLDPE composites were prepared.The results show that the later has better mechanical properties,lower density,better heat resistance,and higher elastic characteristics,however,more water absorption than the former.4.In order to improve the physical and mechanical properties of hot-pressed long straw stem/LLDPE composites,two methods were developed.One is to roll the straw stem along its length(hereinafter referred to as longitudinal split)and the other is to twist the stem into spiral structure.The results show that compared with untreated straw stem,longitudinally split straw stem can provide higher bending properties,impact toughness and water resistance for hot-pressed straw stem/HDPE/LLDPE composites,but not so obvious.Spiral structure is a good way to significantly improve the mechanical properties of hot-pressed straw stem/LLDPE composites.The research focuses on developing the new method for preparing rice straw/LLDPE composite by means of wrapping rice straw with plastic film and then hot pressing.The strength of rice stem and fiber orientation was utilized.The composite material with good performance without crushing straw can be made by this way,which is of great significance to the protection of environment and the utilization of bioresources.