Study On Properties Of PP-based Composites With Degradable Materials

Polypropylene(PP)plastic has the characteristics of light weight and high strength,and is widely used in automobiles,packaging,machinery and other fields.Due to the rapid development of automobiles and other industries,the amount of PP plastic is continuously increasing.A series of problems,the most serious of which are oil resource consumption and environmental pollution.In recent years,the world has become increasingly aware of sustainable development and environmental protection.China has also strengthened environmental protection laws and regulations to promote the development of production methods in the direction of environmental protection.Reducing the use of plastics is of great significance to the consumption of petroleum resources and environmental pollution.To make plastic more economical and environmentally friendly,in this project,PP plastic with a large amount is used.PP composites are prepared by adding degradable plant fibers and other degradable materials.The mechanical properties and water absorption properties of the composites are studied,and the microstructure of the tensile section is analyzed.The main content and conclusions are as follows:(1)Compare the physical and chemical properties of four plant fibers(coconut bran,palm,pennisetum,wheat straw)and the mechanical properties of four plant fibers/PP composites.Studies have shown that four plant fibers have similar composition and thermal properties as wood fibers;of the four plant fibers/PP composites,wheat straw composites have the best performance,with a tensile strength of 16.7MPa,a bending strength of 23.7MPa and the flexural modulus is 1.6GPa,the impact performance is 2.3KJ/m2,and the lowest 24-hours water absorption rate of 3.2%.The tensile section shows that the wheat straw composite has the best combination.(2)Pre-treat wheat straw with hydrothermal treatment and microwave treatment,and prepare composite materials with PP respectively.The study shows that the mechanical properties of hydrothermally treated composites are little better,with a tensile strength of 18.5MPa,a bending strength of 25.5MPa,a flexural modulus of 1.9GPa,and an impact strength of 2.5KJ/m2.Compared with the mechanical properties of untreated composites,the tensile strength is 16.7MPa,the bending strength is 23.7 MPa,the flexural modulus is 1.6GPa,and the impact strength is 2.3 KJ/m2.(3)Compare several wheat straw/PP composite materials with different wheat straw content.The research shows that the mechanical properties of the composite material are the best when the amount of wheat straw is 30%,the tensile strength is 18.8 MPa,the bending strength is 27.1 MPa,the bending modulus is 1.8GPa,and the impact strength is 2.43 KJ/m2.It is very close to the mechanical properties of pure PP plastic.Pure PP has a bending strength of 30.1 MPa,a flexural modulus of 1.9GPa,a tensile strength of 20.3 MPa,and an impact strength of 2.5 KJ/m2.The tensile cross-sectional structure shows that the matrix has a good package of wheat straw and the combination of the two phases is good.The 24-hour water absorption rate of the composite material increases with the increase of the amount of wheat straw added.(4)Add polylactic acid(PLA)and plasticized starch respectively to prepare wheat straw/PP/PLA composite material and wheat straw/PP/starch composite material.The study found that the two composite materials have the highest mechanical properties when the wheat straw content is 10%.The tensile strength,bending strength,bending modulus and impact strength of the wheat straw/PP/PLA composite are 17.7MPa,25.5MPa,1.64GPa,2.26KJ/m2,wheat straw/PP/starch composite material tensile strength,bending strength,flexural modulus and impact strength are 18.23 MPa,27.31 MPa,1.72 GPa and 2.28 KJ/m2;The water absorption rate at 24h is higher than that of wheat straw/PP composite materials.and the contact angle is smaller than that of straw/PP composite materials.Both PLA and plasticized starch exist in the PP matrix in the state of agglomerated particles and are wrapped by the PP matrix.(5)Compare injection molding and compression molding to prepare wheat straw/PP composite materials.The study found that the mechanical and hydrophobic properties of injection-molded wheat straw/PP composites are better than that of compression molding.The mechanical properties of injection-molded composites show a tendency to increase and decrease with the increase of wheat straw content.When the amount of wheat straw is 20%,the composites has the largest mechanical properties,its tensile strength is 25.9MPa,bending strength is 42.8MPa,flexural modulus is 1.9GPa,impact strength is 3.5KJ/m2.It is very close to the mechanical properties of injection-molded pure PP plastic.The injection-molded pure PP has a bending strength of 43.1 MPa,a bending modulus of 1.94GPa,a tensile strength of 26.3 MPa,and an impact strength of 3.7 KJ/m2,the tensile cross-section of the injection-molded composite is denser and its 24-hour water absorption is slightly lower than compression molding composite materials.(6)Compare injection molding and molding to prepare wheat straw/PP/PLA composite material and wheat straw/PP/starch composite material.The study found that injection molding wheat straw/PP/PLA composite materials and wheat straw/PP/starch composite materials have better mechanical and hydrophobic properties than compression molding,and as the amount of fiber added increases the mechanical properties of the composite materials decrease,and the wheat straw content is 10%The mechanical properties are the largest when the wheat straw/PP/PLA composite has a tensile strength of 22.4 MPa,a bending strength of 31.8 MPa,a bending modulus of 1.87 GPa,and an impact strength of 3.1 KJ/m2.For wheat straw/PP/starch composite tensile strength is 25.2MPa,the bending strength is 38.8MPa,flexural modulus is 1.92 GPa,impact strength is 2.95KJ/m2;injection molding composite material has fewer tensile fracture holes,better interface combination;injection molding composite material 24-hour water absorption rate is slightly lower than the molded composite material,and its contact angle is slightly higher than the molded composite material.