Preparation Of Halogenated Polyisobutene-based Elastomer By Cationic Polymerization And Its Properties

Brominated poly（isobutylene-co-p-methylstyrene）copolymer（BIMS）is a new generation of high-performance polyisobutylene-based elastomer.Despite the excellent airtightness and damping properties,BIMS shows good heat resistance（better than EPDM）,ozone resistance,and weather resistance in comparison to traditional butyl rubber.In this thesis,both two-step polymerization method and one-step polymerization method has been applied and studied to prepare halogenated polyisobutylene elastomers.Two-step polymerization is the traditional synthesize method.It includes synthetization of the polymer and bromination.The products were characterized by light scattering and nuclear magnetic resonance spectrum.Results showed the BIMS rubber was successfully synthesized.The content of benzyl bromide was 1.1 mol%depending on ¹H-NMR spectrum.It was similar to the content of commercial BIMS rubber.The produced BIMS rubber was compounded and vulcanized following the standard formula.The mechanical properties and air permeability were tested.The tensile strength of the sample was 6.70 MPa,while the elongation at break was 535%.The results were close to the commercial BIMS rubber.The air permeability coefficient was 0.328×10^-18 P/m²s^-1Pa^-1,which is in the same order of magnitude to the commercial BIMS rubber.Thus,it can be concluded that the air permeability of the copolymer is good enough for commercial usage.Despite the two-step polymerization,candidate innovatively developed a one-step method to synthesize linear high molecular weight isobutylene and chlorostyrene random copolymer.The vulcanization and mechanical properties of the products have been studied.Titanium tetrachloride（Ti Cl₄）,trichlorotriethylaluminum（Al₂Et₃Cl₃）Lewis acid were chosen as co-initiators,while 2-chloro-2,4,4-trimethylpentane（TMPCl）,H₂O were chosen as initiators.The properties of poly（isobutylene-co-chlorostyrene）was studied.The influence of monomer feeding ratio and reaction time on the copolymerization was investigated.When using p-chloromethyl styrene,benzyl chloride is easy to participate in the initiation stage of the reaction process,due to the highly branched structure.Even if relatively weak Lewis acids were used in the initiating system,the macromolecular chain would still slowly participate in the initiation stage and forming branching as the reaction time prolongs.When p-chlorostyrene is used,no branching structure forms.The synthetization progress exhibits a living polymerization features in the Ti Cl₄-initiated system.Depending on the studies,the reaction mechanism was proposed.Finally,in the Al₂Et₃Cl₃/H₂O initiation system,isobutylene,isoprene,and p-chlorostyrene terpolymerization was successfully achieved by one-step polymerization.A mode reaction has been applied to the synthesize progress to scale up the product amount.The vulcanization properties,mechanical properties are evaluated.Due to the halogen atoms.the overall polarity of the polymer has been improved.It benefits the dispersion of carbon black in the matrix.The scanning electron microscope images show that the average particle dimeter of carbon black fillers in the terpolymer is66.27±14.00 nm,which is smaller than 72.25±20.75 nm of butyl rubber.It implies that the carbon black dispersion performance of the polymer is better than that of butyl rubber.