Study On The Reinforcement Of Rubber With Bio-based Filler

With the increasing depletion of fossil fuel resources and increasing concerns about the environment protection,the bio-based materials as the renewable resources have captured much attention.There are various kinds of bio-based materials with high abundances on the earth.The effective and high value-added utilization of bio-materials through physico-chemical technology is the developing tendency of green materials,also,it is the strategic policy for the harmonious development of new material,environment and economy.In this thesis,three kinds of most bountiful biomaterials,i.e.,lignin,cellulose and chitin,are used as green reinforcing agents for rubber composites.We adopt the latex co-precipitation method to fabricate the rubber/lignin,rubber/cellulose and rubber/chitin composites,respectively,and we systematically study the preparation and microstructure-performance relationship for the rubber composites.Lignin,which is by-product of pulp industry,can be used as a novel reinforcing filler to totally/partially replace carbon black in rubber composite.We firstly prepared the SBR/lignin masterbatch through latex-compounding method to achieve a fine dispersion of lignin within the rubber matrix,and the low-molecular weight epoxy resin liquid was added in the rubber/lignin composite in the two-roll mixing procedure.During the following high temperature cure procedure,the-OH of lignin could react with the epoxy group of epoxy resin to in situ generate 3D lignin-epoxy networks,which were evidenced by the SEM study.This rigid networks could significantly enhance the strength and modulus of the composites,for instance,the 300% modulus of the rubber composite was increased by approximately 2.7 times when 20 phr epoxy resin was added.However,the addition of epoxy resin could also lead to the decrease of the elongation at break for the rubber composite.The temperature of 5% and 10% weight-loss of the composites were significantly enhanced because of the introduction of heat-resistant lignin-resin networks.On this basis,we applied the epoxy resin as a modifier for the nitrile rubber/lignin composites,again,it was found that the crosslinking reaction between epoxy resin and lignin occurred in the vulcanization procedure instead of mixing procedure,and the epoxy resin-lignin networks could not only improve the mechanical performance but also enhance the oil resistance of the rubber.We demonstrated that the lignin-epoxy networks could both prominently improve the mechanical performances of non-polar SBR and polar NBR,indicating the lignin-epoxy networks could be a universal reinforcing strategy for the rubber composite.We investigated the lignin/silica hybrid filler on the structure and properties of natural rubber composites.The lignin was incorporated into the rubber composites by latex co-precipitation methodology,and the silica was added by two roll mill.Partial replacement of silica by lignin(no more than 20 phr)did not seriously affect the mechanical properties of the composites.On the contrarily,the inclusion of lignin could significantly improve the composite processing and dynamic mechanical properties,also,the lignin could enhance the anti-aging properties of the rubber composites because the lignin contains large amouts of hindered phenol groups.Cellulose is the most abundant bio-macromolecule in the biosphere,and it is the most important substitute for the products derived from fossil fuel resources.Taking advantage of the alkaline-urea-aqueous system which could dissolve the polysaccharides in the low temperature,we firstly prepared the natural rubber/regenerated cellulose composites by simple co-precipation technology.In the rapid co-precipitation process,NR and honeycomb-like RC were formed simultanously.Both phases are interlocked to form an IPN structure,although the poor interfacial bonding between the hydrophilic RC and hydropholic NR.There is a still strong polymer-filler interaction between NR and RC due to the unique honeycomb-like RC could induce intense interlock/entanglement between NR and RC.Thus the RC could endow NR with a pronounced reinforcement,for instance,inclusion of 30 phr in NR generates a 29-fold increase in Young's modulus(from 0.69 MPa to 20.8MPa)and 3.5-fold(from 0.63 MPa to 6.03MPa)increase in tensile strength.However,the inclusion of RC into the NR decreased the thermal stability of ensuing composites.Chitin,one of the most bountiful biomaterials on earth,is rigid with high modulus and nontoxic,and it could be a promising green filler for the elastomer.In the previous reports,most researchers focused on the use of chitin nanocrystals as a reinforcing phase in elastomer composites.We prepared the natural rubber/regenerated chitin composites by co-precipating the chitin solution and NR latex,again,the regenerated chitin shows a porous structure that could lead a strong polymer-filler interaction,which makes R-chitin shows a significant reinforcement effect towards NR.Since the thermal stability of R-chtitin is lower than that of NR matrix,the incorporation of R-chitin into the NR marix decreases the thermal stability of ensuing rubber composites.