Effect Of Surface Functionalization Modification Of Wheat Straw On The Performance Of PBS

Poly(butylene succinate)(PBS)plays an important role in biodegradable materials and has been widely used because of its excellent physical properties,biocompatibility and environmental friendliness.Wheat straw has a wide range of sources and low price.At the same time,wheat straw powder fiber itself has good mechanical properties and can be used as reinforcement material of wood plastic composites.However,because the surface of wheat straw powder contains a large number of hydrophilic polar groups,the compatibility of composites prepared by blending with PBS is poor.In this thesis,we will study the effect of different treatments on the compatibility of PBS/wheat straw powder composites from three aspects:the influence of wheat straw powder itself,the surface modification of wheat straw powder and the modification of PBS matrix.The main research contents and conclusions are as follows:(1)Effect of wheat straw powder filler itself on the performance of PBS/wheat straw powder composites.The composites were prepared by adding different sizes and contents of wheat straw powder and PBS for melt blending,and the effects of size and content on the composite properties were studied by various performance tests.The results showed that the mechanical properties of wheat straw powder were optimal at 150 mesh,and neither the stress concentration caused by too large size nor the agglomeration phenomenon caused by too small size could be observed.At the same time,the size of 100 and 150 mesh of wheat straw powder can reduce the water absorption rate of the material and slow down the degradation caused by water absorption during the use of the material.In the case of the same amount of wheat straw powder added,the size reduction can effectively improve the melt flow rate of the material,the energy storage modulus and loss modulus is reduced.And change the filling amount of wheat straw powder can be found,a small amount of wheat straw powder added to the PBS matrix can produce heterogeneous nucleation,improve the crystalline properties of the material,when the filling amount of wheat straw powder is 5%,the crystallinity of the material reached 45.43%compared with the crystallinity of pure PBS increased by 21%.Considering all the properties and cost,the subsequent experiments were carried out using 150 mesh wheat straw powder at 15%mass ratio of PBS.(2)Effect of surface chemical modification of wheat straw powder on the performance of PBS/wheat straw powder composites.Three coupling agents,aluminate,titanate and aluminum-titanium composite,were used to chemically modify the wheat straw powder fibers,and the treated wheat straw powder was melt-blended with PBS to prepare the composites.The results showed that the modification effect of aluminum-titanium composite coupling agent was the best under the same amount of the three coupling agents added.The impact strength was increased from 25.18 KJ/m~2before modification to 35.88KJ/m~2at 4%addition of Al-Ti composite coupling agent,and the impact strength was enhanced by 42%.The impact cross-section of the composite was observed by scanning electron microscope,and it was found that the phenomenon of wheat straw powder fiber being pulled out in the impact cross-section was reduced,and the pores and gaps gradually disappeared,and the compatibility of the two was improved.(3)Effect of physical modification of wheat straw powder surface on the performance of PBS/wheat straw powder composites.The physical modification of wheat straw powder by different concentrations of alkali was carried out to study the modification effect of alkali treatment concentration on the composite material.The results showed that the fibers of wheat straw powder became rough after alkali treatment,and the effective contact area with PBS increased,and the two combining ability was enhanced.At the same time,because the alkali treatment removed the amorphous components and impurities in the wheat straw powder fibers,the percentage of cellulose was increased and the thermal stability of the material was significantly improved.(4)Effect of ADR chain-spreading modified PBS and ADR as a compatibilizer on the properties of PBS/wheat straw flour composites.ADR-4400 was used as a chain spreading agent to modify the PBS matrix,and the chain spreading modified PBS was blended with wheat straw powder.The results showed that the branching of PBS molecular chains reduced the melt fluidity of the composites,and the MFR also decreased with the increase of the chain spreading agent,and the melt strength of the composites was enhanced.The mechanical property test shows that the addition of ADR can effectively improve the mechanical properties.The elongation at break increased from 13.43%to 18.26%,and the impact strength also increased from 25.175 MPa before modification to 32.925 MPa,which was about 30.8%.(5)Effect of DCP-initiated PBS crosslinking modification on the properties of PBS/wheat straw powder composites.DCP was used as a cross-linking agent to modify the cross-linking between PBS,while maleic anhydride was added to the composites as a compatibilizer to enhance the compatibility between PBS and wheat straw powder.The results showed that the cross-linked points formed by DCP initiation acted as crystallization points for heterogeneous nucleation during the crystallization of the composites,and the crystallinity was enhanced.Meanwhile,the formation of cross-linked mesh structure can effectively improve the mechanical properties of the composites.The tensile strength increased from 25.31 MPa before modification to 44.80 MPa when the DCP content was1.5%,an increase of 77%.The rheological properties of the composites were also analyzed,and it was found that the enhancement of DCP content enhanced the melt strength of the composites,and the material gradually changed from viscous deformation to elastic deformation with the increase of DCP content at the same temperature and angular frequency.