Preparation of long bamboo fiber and its reinforced polypropylene membrane composites

ZHAO He;MIAO Qingxian;HUANG Liulian;ZHOU Xiaxing;CHEN Lihui;National Forestry and Grassland Administration Key Laboratory of Plant Fiber Functional Materials,College of Materials Engineering, Fujian Agriculture and Forestry University;

long bamboo fiber;;bamboo plastic composite;;polypropylene;;hot pressing technology;;mechanical property

Currently, China has become the largest country in automobile production and consumption all over the world. Research on the application of high-performance bamboo fiber reinforced polypropylene composite materials to automotive interior parts is in line with the current concept of environmental protection and sustainable development, and is of great significance to the utilization of bamboo resource advantages and the enhancement of the added value of bamboo products in China. In order to develop bamboo fiber reinforced composites for automobile interior decoration, taking green bamboo which was one of the abundant resources in Fujian province and polypropylene membrane(PP) as raw materials, the preparation process of long bamboo fiber with high production efficiency and length-width ratio(LBF), and hot pressing process parameters of LBF/PP were researched. By analyzing the effects of alkali pretreatment process on the yield of bamboo chips, the yield and whiteness of the LBF, the pretreatment process of the LBF were optimized. Furthermore, the effects of hot pressing parameters and the amount of the LBF on the physical and mechanical properties of the LBF/PP composites were investigated, and then the optimal hot pressing parameters and the amount of the LBF were determined. The main results were summarized as follows: when the treatment temperature was 100 ℃, the optimal pretreatment process was sodium hydroxide of 10%, and treatment time of 180 min. Under the optimal process conditions, cellulose content and crystallinity of the LBF increased, but the lignin content decreased, comparing with bamboo chips. Fiber length and length-width ratio of the LBF were 25.79 mm and 173.02∶1.00, respectively, and the tensile strength and tensile modulus of the LBF were 584.85 MPa and 45.41 GPa, respectively. The optimal hot pressing parameters were that hot pressing temperature of 190 ℃, hot pressing pressure of 8 MPa, and hot pressing time of 20 min, and the optimal amount of the LBF was 50%. Under the molding conditions, the tensile strength, flexural strength, flexural modulus and impact strength of the composites were 31.55 MPa, 46.11 MPa, 2 833.80 MPa and 28.55 kJ/m~2, respectively, and the water absorption and the thickness swelling were 14.19% and 8.11%, respectively, which can meet the requirements of hard dashboard, utility box and other automotive interior accessories. Scanning electron microscope(SEM) showed that the surface of the fiber was rough, and the melted PP in the hot pressing process penetrated into the pores of the surface of the bamboo fiber, which was beneficial to form a better physical and mechanical interlock.