Preparation And Performance Study Of Tobacco Stalk Fiber/PBAT Composites

As one of the most important cash crops in China,the chemical composition of tobacco stalk fiber is similar to that of wood fiber,which has the characteristics of wide distribution area,large yield,low price and renewable,but low resource utilization.Polybutylene terephthalate(PBAT)has excellent ductility,toughness,easy processing and biodegradability,but it also has some problems such as poor bending property,low stiffness and high production cost.Using waste tobacco stalk fiber(TSF)in PBAT reinforced system to prepare composite materials can realize high efficiency and high value utilization of waste tobacco stalk fiber,save resources and avoid environmental pollution.It can improve the mechanical properties of PBAT,reduce the product cost,expand the application field of degradable plastic PBAT,and obtain good economic benefits.In this paper,TSF/PBAT degradable composite material was prepared by melt blending injection molding technology using waste tobacco stalk in Qinling-Ba mountain area as plant fiber raw material and PBAT as resin matrix.The effects of different fiber content,different kinds of modifiers and degradation methods on mechanics,water absorption,thermal stability,crystallization and melting,interfacial properties and degradation rate of TSF/PBAT composites were systematically studied.The main research conclusions are as follows:(1)The addition of tobacco stalk fiber reduces the tensile strength and elongation at break of pure PBAT,and the fiber content has little effect on the tensile strength of TSF/PBAT composites.The bending strength increased and then decreased with the fiber content,and the bending modulus continued to increase.When TSF content is 40%,the composite has the best mechanical properties,and the tensile strength,bending strength and bending modulus are 9.9MPa,17.8MPa and 714.0MPa,respectively.The water absorption of TSF/PBAT composites increased with the increase of the fiber content of tobacco stalk.The thermal stability of PBAT was reduced by tobacco stalk fiber,and the higher the fiber content,the worse the thermal stability of the composite.The addition of fibers hindered the movement of PBAT molecules and reduced the crystallinity of TSF/PBAT composites.The higher the fiber content of the composite material,the more holes in the tensile fracture surface,the more obvious the fiber pulled out.(2)PBAT-g-MAH,KH560,OH-MWCNTs modification and combined modification of PBAT-g-MAH/KH560(MA/K)and PBAT-g-MAH/OH-MWCNTs(MA/OM)all enhanced the mechanical properties of TSF/PBAT.MA/OM combined modification has the best improvement effect on the tensile and bending strength of TSF/PBAT composites,reaching 17.3 MPa and 28.0 MPa,which are 74.7%and 57.3%higher than those without modification.K4 has the best improvement effect on the elongation at break(8.03%),which is 96.8%higher than that without modification.The bending modulus of OM0.5 modified composite is the highest(1086.0MPa),which is 52.1%higher than that of the unmodified composite.The 7-day water absorption of MA/K modified composites was 31.84%lower than that of unmodified TSF/PBAT.The thermal stability of the modified composites was improved and the crystallinity was also increased by 7.3%to 37.5%compared to the unmodified composites.The addition of the modifier improved the interfacial compatibility of the composites,and the fiber pull-out as well as cracks at the tensile fracture surface were significantly reduced,and the holes between the fibers and the matrix almost disappeared.(3)The lowest PBAT mass loss rate was observed after 16 weeks of soil degradation,while the highest unmodified TSF/PBAT loss rate reached 10.5%.The tensile strength,flexural strength and flexural modulus of the modified TSF/PBAT composites increased and then decreased with soil degradation time.The overall mechanical properties of PBAT and unmodified composites showed a decreasing trend,and the unmodified composites mechanically failed after 16 weeks.PBAT degraded under 16 weeks of soil degradation,and most of the degradation occurred on the surface with reticulation cracks.The surface of pure PBAT degradation showed net-like cracks,and the surface of TSF/PBAT composites was obviously rough with degradation time and the cracks increased,among which the unmodified composites were more obvious.MA/OM-TP surface damage minimized,the internal pores of the composites were increased,and the modifier could significantly slow down the degradation rate of TSF/PBAT composites.(4)The lowest PBAT mass loss rate of 0.26%and the highest unmodified composite mass loss rate of 1.89%observed after 16 weeks of degradation in the simulated seawater environment.The tensile strength,flexural strength and flexural modulus of TSF/PBAT composites showed the same trend under seawater degradation,which increased and then decreased with the increase of degradation time.While the mechanical properties of PBAT decreased,the elongation at break was reduced in all samples,and the overall mechanical properties of the composites were less damaged by seawater degradation in the short term.Short-time seawater degradation had almost no effect on the PBAT surface,rough cracks were evident on the unmodified TSF/PBAT surface,cracks gradually appeared in MA2-TP and MA/K-TP after four weeks of degradation,and small damage was minimal on the MA/OM-TP surface.The material is tightly bound internally in the early stages of degradation,and the voids increase in the later stages.The modification can slow down the degradation rate of the composites in seawater.By comparing with soil degradation,PBAT and TSF/PBAT composites were more affected by microorganisms.In this paper,the preparation method of tobacco stalk fiber reinforced PBAT degradable composite was systematically studied,and the preparation,comprehensive performance improvement and degradation characteristics of TSF/PBAT composite were completed.The whole life cycle of tobacco stalk fiber reinforced PBAT composite was explored.The research results can provide theoretical reference for recycling and high-value utilization of waste tobacco stalk in the field of composite materials.