| With the rapid development of social economy,environment is deteriorated,people’s awareness of environmental protection continues to improve,and the new requirements for the biodegradability of fiber reinforced composites are proposed.Developing and utilizing of agricultural waste and other renewable,biodegradable composite materials become the inevitable trend of scientific and technological development.The traditional composites have the advantages of high strength,high modulus,energy saving,but the recycling and regeneration of composites have caused a great burden on the environment.So to solve the composites be renewable,biodegradable is the development direction of green composites.The main goal of this work was to use six kinds of plant fibers(straw:rice straw,wheat straw,peanut straw;crustaceans:rice husk,wheat hull,peanut shell),four kinds of biological glues(sodium alginate,guar gum,plant protein glue,starch glue),added moisture agents(glycerol,chlorinated paraffin,glycerol&chlorinated paraffin),prepared biomass composites by a compression molding process.The optimum process parameters were determined by orthogonal test.The mechanical properties,moisture absorption and thermogravimetric properties of composites which prepared with wheat straw and different biological glue,six kinds of plant fiber and plant protein adhesive,were compared.And the effects of pretreatment method and moisture agent on the properties of wheat straw/plant protein adhesive composites were studied.The main conclusions are as follows:(1)Through the orthogonal test method L9(34),the optimum pressing parameters of the preparation of wheat straw/sodium alginate composite material were determined,with the tensile strength and bending strength as the optimization parameters.The best molding temperature was 160℃,molding pressure was 6MPa,molding time was 6min.(2)Infrared spectra of four kinds of biological glues and wheat straw were analyzed.Plant protein adhesive has stretching vibration absorption peak of—NH2,which can be a chemical reaction with wheat straw fiber to produce—O—,with a higher bond energy.Among the four kinds of biomass composites,the tensile strength,flexural strength,flexural modulus and impact strength of the wheat straw/plant protein adhesive composites were the highest,which were 5.47MPa,16.05MPa,3459.09MPa and 2.44KJ/m2 respectively,and its moisture absorption rate was 9.76%,which was the lowest.Its cross-section microstructure showed that wheat straw was better encapsulated by plant protein adhesive,and the interface between plant protein and wheat straw combine well.Mechanical properties of wheat straw/biological glues composites can be compared with the plastic matrix composites.Due to its environmental friendliness and the advantages of formaldehyde zero release,it can be used as non-load-bearing decorative materials at indoor and other dry environment.(3)According to the composition analysis of three kinds of straw fibers from rice straw,wheat straw and peanut straw,cellulose and hemicellulose content of wheat straw were the highest.The analysis of properties of composites prepared with three kinds of straw fibers and plant protein adhesive showed that mechanical properties of wheat straw/plant protein adhesive were the highest,and its moisture absorption rate was the lowest.Its cross-section is better,in which wheat straw fiber can play a good role in the transfer stress.The microstructure analysis further validated the macroscopic manifestations of its mechanical properties and hygroscopic properties.The starting temperature of wheat straw/plant protein adhesive was the highest,which was 281.9℃,and the residual mass ratio was 32.49%.Different composites have heat changes during heat loss.(4)According to the composition analysis of three kinds of chitin fibers from rice husk,wheat hull and peanut shell,cellulose and hemicellulose content of wheat hull were the highest.The analysis of properties of composites prepared with three kinds of chitin fibers and plant protein adhesive showed that the tensile strength,tensile modulus,flexural strength,flexural modulus and impact strength of wheat straw/plant protein adhesive were the highest,which were 1.89MPa,137.55MPa,4.87MPa,615.72MPa and 1.06KJ/m2 respectively.Moisture absorption rate of peanut shell/plant protein adhesive composites was 8.70%,which was the lowest.The cross-section of wheat shell/plant protein adhesive composites had few voids and defects,and wheat straw/plant protein adhesive had a good interface.The absorption peak of rice husk/plant protein adhesive composites at the wave number of 3500～3400cm-1 was strong,which leaded to the strongest hygroscopicity.The weight loss starting temperature of rice husk/plant protein adhesive was 283.4℃,which was the highest,and the residual mass ratio was 34.45%.(5)The analysis of properties of wheat straw/plant protein adhesive composites with different pretreatment conditions(hydrothermal treatment,microwave treatment,biological enzyme treatment,untreated)showed that the mechanical properties of composites prepared by the pretreated wheat straw were better than those of untreated composites.Properties of composites with hydrothermal treatment had the greatest degree of improvement,whose tensile strength,tensile modulus,flexural strength,flexural modulus and impact strength were 6.72MPa,352.65MPa,15.51MPa,1842.40MPa and 4.37KJ/m2 respectively,and equilibrium moisture absorption rate was the lowest,9.11%.Microstructure displayed that wheat straw/plant protein adhesive with hydrothermal treatment had a good interface.With different pretreatment,the FTIR characteristic peaks of the composites increased,decreased or disappeared in different degrees.The thermal stability of the composites with pretreatment was improved,and the residual mass ratio of the composites with hydrothermal treatment was 38.29%.(6)The analysis of properties of wheat straw/plant protein adhesive composites with hydrothermal treatment,which added different moisture agents(glycerol,chlorinated paraffin,glycerol&chlorinated paraffin,not added)showed that the tensile strength and bending properties of the composites with the addition of moisture agent were better than those without the addition of the moisture agent,but the impact strength of the composites added with chlorinated paraffin decreased.The vibration of the composites with the addition of the moisture agent at the C—O in the carbohydrate was weaker than that without the addition of the moisture agent,which can effectively improve the moisture resistance of the composites.The equilibrium moisture absorption of the composites with glycerol&chlorinated paraffin was the lowest,8.59%.The cross-section of composites with addition of glycerol was smooth and the material was more compact.And chlorinated paraffin can improve the thermal stability of the composites. |
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