Research On The Preparation Of Bamboo Fiber And Its Application In Polypropylene Material

Green and renewable bamboo resources are extremely rich in China.Bamboo fiber(BF),as a new type of natural green and environmentally friendly fiber material extracted from bamboo,is widely used in composite materials.BF composites have become the preferred material for green building materials because of their excellent properties such as mold resistance,insect resistance,sound and heat insulation,and good stability.However,there are still some problems,such as low production efficiency,poor dispersion uniformity,and poor interface combination of BF composites.In this study,bamboo fibers(BFs)were prepared by a combination of alkali treatment and steam explosion.The effects of alkali treatment conditions,steam explosion process and bamboo age on the yield,size,microstructure,chemical composition,thermal and hygroscopic properties of BFs were explored,and the effects of bamboo fiber/polypropylene film(BF/PP)ratio on the physical-mechanical and thermal properties of the composites were investigated on the basis of the optimal preparation process.The main results are as follows:(1)The alkali treatment concentration and rolling gap had significant effects on the content of BF separation,but alkali treatment time had no significant effect on it.With the increase of alkali treatment concentration and time and the decrease of rolling gap,the dispersion degree and uniformity of BFs were significantly improved.The combined effect of alkali treatment and steam explosion on BFs resulted in a decrease in hemicellulose and lignin content,and the crystal form and crystallinity of cellulose did not change significantly.In consideration of environmental protection and preparation efficiency,the alkali treatment process with alkali treatment concentration of 5%,alkali treatment time of 1 h and rolling gap of 2 mm was finally selected to treat bamboo.(2)The solid-liquid ratio,pressure and pressure holding time of steam explosion had highly significant effects on the content of fine fibers,and also on the yield,microstructure,chemical composition and physicochemical properties of BFs.The highest content of fine fiber was 39.07% when the solid-liquid ratio of steam explosion was 2:1,the explosion pressure was2.2 MPa,and the pressure holding time was 4 min.When the solid-liquid ratio was 2:1,the bamboo fiber bundle dispersed into single fiber.With the increase of steam explosion pressure and pressure holding time,the dispersion degree and uniformity of BFs increased,and the hygroscopicity of BFs decreased.The hemicellulose and lignin in BFs were partially removed,and the crystal form of cellulose did not change.The optimal process for steam explosion is a solid-liquid ratio of 2:1,a explosion pressure of 2.2 MPa,and a holding time of 4 min.(3)Bamboo age had obvious effects on the yield,microstructure,chemical composition and physical properties of BFs.With the increase of bamboo age,the dispersion degree and uniformity of BFs increased,and the length and diameter of BFs increased first and then decreased.The hemicellulose and lignin of BFs were partially removed,and the crystal form of BFs did not change with the change of bamboo age.With the increase of bamboo age,the cellulose crystal form of BFs remained unchanged,but the crystallinity of that first decreased and then increased.The hygroscopicity and hysteresis of BFs increased slightly with the increase of bamboo age.During the process of steam explosion,high-temperature steam entered the inside of bamboo,in an instant explosion,the interface between the vascular bundle and parenchyma broke,resulting in delamination cracked,which began to extend along the vascular bundle interface to both sides,eventually leading to the fracture of bamboo.(4)With the decrease of BF content,the specific flexural strength and specific flexural modulus of BF/PP composites showed a trend of increasing first and then decreasing,and reached the maximum when the ratio of BF/PP was 6:4.When the content of BFs is 60% or less,polypropylene can fully wrap the BF.The water absorption and water absorption thickness expansion rate of BF/PP composites showed a trend of rising rapidly and then tended to be flat.When the BF content was 60% or less,the water absorption and water absorption thickness expansion rate decreased significantly.BF/PP composites has the characteristics of heat insulation low density,and is an excellent choice for home furnishing materials.Therefore,the development and preparation of BF/PP composites with excellent comprehensive properties has good practical significance and practical value.