Preparation And Characterization Of Waste Paper Fiber/polylactic Acid Composite

As a biodegradable material,polylactic acid(PLA)has the advantages of good trnsparency,glossiness and reproducibility.However,PLA has the disadvantages of high cost,low toughness and brittleness,which limit its application in the field of packaging.It usually needs to be modified to improve its performance.Among many modifiers,natural plant fiber has the advantages of wide source,renewable and degradable,and has become an excellent modifier for the preparation of degradable composite materials.In view of the shortcomings of PLA,three silane coupling agents(KH550,KH560,KH570)were used as interface modifiers to modify the surface of waste paper fiber and dichloromethane was used as solvent to prepare waste paper fiber/PLA composite.The effects of beating time,amount of waste paper fiber and silane coupling agent on the microstructure,cross section structure,functional groups,mechanical properties,thermal decomposition process and crystallization properties of the composites were studied.The functional groups of the waste paper fiber before and after modification were determined by Fourier transform infrared spectrum analysis(FT-IR),and the results showed that the coupling agent was successfully connected to the surface of the waste paper fiber.Scanning electron microscopy(SEM)was used to observe the microstructure of the tensile section of the composite material.The results show that the surface of the modified waste paper fiber is more smooth,and the interface compatibility between the modified waste paper fiber and the PLA matrix is improved.The thermal properties of waste paper fiber/PLA composites were measured by differential scanning calorimetry(DSC).The results show that the use of silane coupling agent can increase the melting temperature of the composites.The mechanical properties of the composites were analyzed by electronic universal testing machine.The results show that the mechanical properties of the composites can be significantly improved by adding an appropriate amount of waste paper fiber,but the tensile strength of the composites will be reduced by adding too much waste paper fiber.At the same time,the mechanical properties of the composites can be enhanced most obviously by modifying waste paper fiber.When the amount of waste paper fiber was the same,the mechanical properties of the composite were improved most obviously when the beating time was 30 min.The mechanical properties of the composites were significantly improved when the amount of waste paper fiber was 25%,and the coupling agent KH560 had the best modification effect on the composites.The crystallization of waste paper fiber/PLA composite was analyzed by X-ray diffraction(XRD).The results show that the addition of waste paper fiber can promote the crystallization of PLA,but does not change the crystal shape of PLA.The thermal decomposition of the waste paper fiber/PLA composite was analyzed by thermogravimetric analyzer(TG).The results show that the thermal decomposition temperature of the modified composite is higher than that of the pre-modified composite.However,compared with the PLA matrix,the thermal decomposition temperature of the composite before and after modification decreased somewhat,and the thermal decomposition temperature decreased with the increase of the amount of waste paper fiber.