Construction Of Sacrificial Units In Bio-based Elastomers And Its Effects On The Performance

Nowadays,because of the increasing depletion of chemical resources and the increasing pressure of energy worldwide,the petroleum related industries are facing great challenges.The research on the replacement of petroleum-based polymers by renewable resources has attracted more and more attention.Bio-based elastomer is an alternative elastomer of petroleum-based elastomer.On the one hand,the reactive monomers can be extracted from a large number of biomass residues.The monomers can be polymerized to yiled bio-based elastomers.On the other hand,in addition to natural rubber,there are also other natural polymer resources such as Eucommia Ulmoides gum(EUG).Due to the capability of strain-induced crystallization,natural rubber exhibits high tensile strength and elongation at break while it has low modulus.Eucommia gum is easy to crystallize at room temperature,resulting in low extensionablity.In this thesis,the sacrificial bond is constructed into the synthesized bio-based polyester elastomer by introducing quadruple hydrogen bonds,and scarificial domain is constructed into the natural rubber by incorporating Eucommia Ulmoides particles with high crosslinking density.The effects of the sacrificial units on the performance of the results rubbers are investigated.The main contents and conclusions are as follows.A biobased polyester elastomer(BPE)is synthesized through melting polycondensation using industrially available biobased diols and diacids as the starting materials.The biobased elastomer is covalently crosslinked by pentaerythritol tetra(3-mercaptopropionate)as the linkers,and grafted by 2-ureido-4-[1H]-pyrimidinone containing acrylate(UPy MA)through“thiol-ene” click reaction.Up deformation,the UPy dimers can preferentially break to dissipate a large amount of mechanical energy through reversible fracture-recombination events of UPy dimers,thereby significantly enhancing the fracture toughness of the BPE.The dissociation of UPy dimers under heating endows the elastomer with thermally responsive shape memory behavior.A highly cross-linked EUG is prepared with sulfur-based curing package and crushed into particles,which are then incorporated into NR as dispersion phase(hard phase).During curing of NR using sulfur-based curing package,NR matrix and EUG particles form covalently bonded interfaces,resulting in excellent interfacial interaction.Up deformation,EUG hard phases significantly improve the modulus and strength of NR by acting as sacrificial units.The heat build-up in NR filled with EUG particles is significantly lower than that in carbon black-filled NR.In addition,the incorporation of EUG hard phase into styrene-butadiene rubber(SBR)or SBR/silica composites can also significantly improve themechanical properties,indicating that this method is versatile for reinforcing different kinds of rubbers.