| With the increase of human concern about environmental pollution,the development of new environmentally friendly materials has become a general consensus.Wood-plastic composites is an environmentally friendly material prepared by compounding natural biomass waste with plastic,which can not only realize the recycling of waste biomass but also reduce the use of petroleum-based non-degradable plastics.Spent coffee grounds(SCG)is a kind of biomass waste,the main component is cellulose,hemicellulose,and other polysaccharides.Because polysaccharides contain a large number of hydrophilic hydroxyl groups,SCG is not conducive to interface compatibility when blended with hydrophobic plastics,and the mechanical properties of wood-plastic composites prepared from it are poor.Therefore,improving interfacial compatibility is a prerequisite for the preparation of high-performance wood-plastic composites.In this paper,SCG was prepared by melt blending with petroleum-based plastic polypropylene(PP)as a filler.To improve the hydrophobicity of SCG and improve the interface compatibility between SCG and PP,heat treatment and silane coupling agent modification of SCG were carried out,and the mechanical,thermal,and hydrophobicity of SCG/PP composites,as well as the influence of silane coupling agent A171 on the properties of composites after hot air aging,were studied.Specific research contents include:1.Effect of heat treatment on the properties of SCG/PP wood-plastic composites:Firstly,the influence of heat treatment conditions on SCG was studied,the results of digital camera and scanning electron microscopy showed that heat treatment would make SCG loose and particle size smaller,and it was found that heat treatment at 240 °C for1.5 h under air atmosphere,SCG residual oil content is low and hydrophobic,which is conducive to the dispersion and interface compatibility in PP.Subsequently,the obtained SCG was crushed,and the SCG/PP composites were prepared by melt blending,and the performance analysis of the composites by microscope,video contact angle meter,thermogravimetric analyzer,differential scanning calorimeter,and universal testing machine found that the SCG with low residual oil content had good dispersion in PP,and the prepared composites had strong hydrophobicity,low water absorption,and excellent mechanical properties.In addition,the particle size and content of SCG have a greater influence on the mechanical properties,and when the SCG particle size is smaller(200mesh)and the lower the content(25%),the better the comprehensive properties of the composite material.2.Effect of silane coupling agent on the properties of SCG/PP wood-plastic composites: firstly,the silane coupling agent 3-aminopropyltrimethoxysilane(KH540),3-aminopropyltrimethoxysilane(KH550)and vinyl trimethoxysilane(A171)were used to perform surface pretreatment on the surface treatment of the heat treated SCG,and the results of infrared spectroscopy and video contact goniometer showed that the three silane coupling agents were successfully grafted to the SCG,and the water contact angle of SCG was increased by about 4°.Then,the dosage of three silane coupling agents was changed,and the mechanical properties,hydrophilicity,and thermal stability tests of the prepared SCG/PP composites were carried out,and it was found that the dosage of KH540 and KH550 was 0.5%,and the dosage of A171 was 3%,the performance of the composite materials was the best,and the performance of SCG/PP composites was compared based on the above dosage,and the results showed that the silane coupling agent A171 improved the performance of the composites most obviously.Finally,the hot air aging of the modified silane coupling agent A171 showed that the damage degree of hot air aging to A171-SCG/PP composites was smaller than that of SCG/PP,and the mechanical properties showed that the mechanical properties of A171-SCG/PP composites decreased by a small margin,indicating that silane coupling agent A171 had a certain delay effect on the thermal aging behavior of the composites. |
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