Study On The Preparation And Properties Of Heat-Resistant Fillers/Biomass Thermoplastic Composites

Biomass thermoplastic composites were prepared by blending wood flour or woody biomass of agricultural residues with thermoplastic polyethylene or polypropylene through extrusion,injection molding or compression molding processes.Because of its low moisture absorption,low density,biocorrosion resistance,good dimensional stability,and high specific stiffness and strength,it is becoming a favorable choice for recycling agricultural residues.This paper proposes an efficient method for recycling agricultural residues,blending mulch,sandy soil and cotton stalks that were difficult to separate due to mechanized operations,and directly preparing biomass thermoplastic composites.Inspired by this,the cotton stalk-polyethylene-aluminum silicate fibers composites and the cotton stalk-polyethylene-kevlar fibers composites were prepared using aluminum silicate fiber and kevlar fibers as fillers.First of all,through a simple mixing and injection molding process,the difficult to separate mulching film,sandy soil,and cotton stalk wastes were converted into functional self-extinguishing cotton stalk-polyethylene-sandy soil composites(CS-PE-SSX),and the influence of different components on the properties of the composites were explored.It was found that due to the uniform dispersion of solid particles in polymer matrix and the promising interface combination and the potential interaction between cotton stalk and sandy soil particles,the resultant composites showed promising mechanical strength(a flexural strength of approximately 29.00 MPa,a tensile strength of approximately 15.76MPa,and an impact strength of approximately 3.17 k J/m²)and improved thermal stabilities.The addition of sandy soil particles endowed materials with favorable self-extinguishing properties.The composites with 40 wt%sandy soil contents can resist flaming ignition within 10 seconds,and the fully ignited composites can be guaranteed to flame out within55 seconds.Moreover,the actual agriculture wastes containing mulching film residues,cotton stalk,and soil from different areas of China were also successfully transformed into functional composites,showed promising mechanical,thermal,and self-extinguishing properties.The successful preparation of composites provides a simple,green,and low-cost strategy for the treatment of agricultural residues,and is expected to become a viable option for solving agricultural mulch,cotton stalks and other wastes.Next,this study used inorganic fiber(aluminum silicate fiber,ASF),organic agricultural wastes(cotton stalk,CS)and polyethylene as the main raw materials to prepare biomass thermoplastic composites(CS-PE-ASF_X),and the effects of aluminum silicate fiber on the properties of the composites were discussed.The research results show that with the increase of ASF contents,the oxygen-containing groups in the aluminum silicate fibers can form hydrogen bonds with the hydroxyl hydrogen in the cotton stalk,and the peaks of Fourier infrared spectrometer at?1740 cm^-1 shifted to lower wavenumber,indicating non-covalent interactions(hydrogen bonding,?-?stacking and electrostatic interaction)at the interface of the composites.The X-ray diffraction patterns of the composites shows the change of the ASF content without changing the crystal structures of each component.The scanning electron micrograph of the composites and the element scanning image strongly proves the good dispersion of ASF in the composites and the stable bond with the polymer matrix.The above two,together with the hydrogen bond formed by the cotton stalk and the aluminum silicate fibers,increase the tensile strength and impact strength of the composite to 39.37 MPa and 3.89 k J/m².The addition of ASF noticeably improves the creep resistance and stress relaxation resistance of the composites,and the thermal stability of the composites also enhanced with the help of ASF.Finally,this research uses ultra-high-strength,high-temperature,acid-and alkali-resistant lightweight synthetic fibers(kevlar fibers)as fillers to prepare cotton stalk-polyethylene-kevlar fibers composites(CS-HDPE-KF_X),and its properties were studied.The research results show that the addition of kevlar fibers will promote the change of the chemical environment in the composites,the formation of hydrogen bonds,and the shift of the characteristic peaks of the infrared spectrum.Scanning electron microscopy found that the kevlar fibers still exists as a long fiber in the composites,and there was no change.When the kevlar fibers was below 30 wt%,it shows a disordered form,which observably improves the mechanical properties of the composites.The maximum tensile strength was 41.89 MPa,an increase of about 231%,the maximum flexural strength was 55.28 MPa,an increase of 209%,and the maximum impact strength was 12.40 k J/m²,an increase of about 349%.Compared with rice husk,sandy soil,poplar wood powder thermoplastic composites,after adding kevlar fibers,the mechanical strength of the composites was markedly enhanced.The thermogravimetric and differential scanning calorimetry curves of the composites indicate that the remarkable increase in the residue and the increase in the melting temperature enhance the thermal stability of the composites.Creep and stress relaxation curves show that the composites have the best creep resistance at 20 wt%kevlar content and the best stress relaxation resistance at 30wt%kevlar content.Through the flame-retardant performance test,the composites have the best flame-retardant performance when the content of 20 wt%kevlar fibers,the number of ignitions in 5 s reaches three times,the flame out time and burning distance are maintained at 125 s and 2.5 mm,respectively,and the limiting oxygen index reaches 20.9%.