Research On The Preparation And Properties Of Bamboo Charcoal/Polyamide 6 Composite

Engineering plastic with a high melting point cannot be employed as the matrix of wood-plastic composites(WPC)because of the thermal degradation of filler(plant fiber).Hence,the development and application of WPCs are limited in areas with superior mechanical strength requirements.In this paper,waste bamboo fiber was pyrolyzed at high temperatures to prepare bamboo charcoal(BC),and the BC was used as the filler while engineering plastic polyamide 6(PA6)was used as the matrix.Then,low-water-absorption,high-strength,and high-toughness PA6/BC composites were prepared by melt blending and injection molding.The relationship between BC content,particle size,carbonization temperature,additive treatment,blend modification of polyethylene resin and the processing fluidity,hydroscopicity,dimensional stability,thermal stability,melt crystallization,and mechanical properties of PA6/BC composites was studied.The interface bonding mechanism of PA6/BC composites and the strengthening/toughening mechanism of BC under different formulations were revealed.The experiment was beneficial exploration for the application of engineering plastic in the WPC field,and also finds a breakthrough for the efficient utilization of waste wood/bamboo or other biomass resources,and plays a positive role in material innovation and environmental protection.The main research results are summarized as follows:(1)The compatibility and reinforcement effects of BC and PA6 are preferable to that of carbon fiber,which can replace or partially replace the application of carbon fiber in PA6.The addition of BC improved the water resistance and thermal stability of PA6.The water absorption rate and linear thermal expansion coefficient of PA6/BC composites declined with the increase of BC content,and the maximum decreases were 46%and 50%,respectively.When BC content less than 30wt%,it is helpful to the processing liquidity of PA6,and the maximum melt index increased by 99%.BC has a heterogeneous nucleation effect in the PA6/BC composites,which helps to promote the formation of the stable alpha crystal form of PA6 and increasing the crystallization temperature and crystallinity of the composites.BC particles have good dispersibility and wettability in the PA6 matrix and generate a van der Waals force and mechanical interlocking effect with the PA6 matrix,and the interface bonding strength and mechanical properties increased.The maximum increase in tensile/flexural strength of PA6/BC composites was 41%and 72%,and the maximum decrease in impact strength was 27%.Water immersion treatment reduces the dimensional stability and mechanical strength of the composites and enhances the impact toughness.(2)High-temperature pyrolysis BC has aromaticity and self-lubricity,which improves the processing fluidity,water absorption and dimensional stability of PA6/BC composites.The maximum increase in the melt index is 36%,and the maximum decrease in water absorption,and linear thermal expansion coefficient is 33%and 42%,respectively.The specific surface area,porosity,and surface roughness of BC pyrolyzed at high temperatures are large,and the interface interaction with the PA6 matrix is strong.The PA6 melt flows into the pores of BC to form a strong interlocking structure,and the mechanical properties of the composites are improved.Compared with pure PA6,the maximum increase in tensile/flexural strength was 51%and 72%,and the maximum decrease in impact strength was 29%.(3)The processing fluidity,water absorption,crystallinity,thermal properties,mechanical properties,and dimensional stability of PA6/BC composites do not change monotonously with the particle size of BC.The small particle size BC has good dispersibility and wettability,and is easy to embed in the PA6 matrix to form a more stable binary structure;the PA6 melt easily flows into the pores of the large particle size BC to form a strong mechanical interlock.Large particle size BC has a better reinforcing effect,and small particle size BC has a less negative effect on toughness.BC with suitable particle size is compounded and hybridized,which has a good gradation effect and achieves the effect of strengthening and toughening.For example,the tensile/flexural/impact strength of PA6/BC200N/BC25M hybridized with 200 nm BC and 25 ?m BC is increased by 49%,75%and 14%,respectively.(4)The nucleating agents WBG-? and WNA108 have good heterogeneous nucleation ability in the PA6/BC composites,promote the growth of PA6 crystallites and grain refinement,and the crystallization temperature and crystallinity of the composites increased.Inorganic powder surface treatment agent WOT 108 and processing modifier WAC802 improve the dispersibility and wettability of BC particles,and the interface compatibility and interface bonding strength of PA6/BC composites increased.The addition of the four additives has achieved the enhancement and toughening of the PA6/BC composites and improved water resistance and dimensional stability.Compared with pure PA6,the tensile/flexural/impact strength of the composites increased by 51%?57%,76%?82%,12%?28%,respectively;the water absorption rate decreased by 27%?34%,and the linear thermal expansion coefficient decreased by 27%?37%.(5)MAPE has a compatibilizing and toughening effect on the PA6/BC composites.Compared with pure PA6,the tensile/flexural/impact strength of PA6/BC/MAPE is increased by 33%,61%,and 30%,respectively;water absorption and linear thermal expansion coefficient decreased by 30%and 18%,respectively.The interface compatibility of LDPE,HDPE,UHMWPE,and PA6 is poor,and the interface gap and phase separation are obvious.Compared with pure PA6,the tensile/flexural/impact strength of the composites modified by LDPE,HDPE,UHMWPE is decreased by 20%?36%,16%?39%,and 3%?18%,respectively;and the water absorption rate is reduced by 53%?64%.