Synthesis And Performance Study Of Styrene-Butadiene Resin

Styrene-butadiene copolymer resin is with more than70weightpercent styrene. By designing the molecular structure, small amounts ofbonded butadiene plays the role of toughening, that makes the resin havehigh impact strength and large elongation at break, meanwhile, the lighttransmittance remains excellent and haze does not obviously increase.This kind of resin with excellent processing properties, non-toxic, highgloss, impact resistance and other characteristics, was widely used inchildren’s toys, household appliances, medical equipment, office suppliesand other production. During the past years, commercial products weremainly from the United States, Japan, Germany.In this work, a systematic research in the relation of polymerproperties and molecular strucfture of styrene-butadiene resin was carriedout experimently by studying the synthesis and termination technology aswell as coupling agent. The main work is briefly concluded as follows:1、Butadiene content determines the properties of light transmittance,haze and mechanical performance, taking both the optical performance and mechanical properties into consideration,25%is better.2、A star resin having good impact resistance and high elongation at breakwas synthesized by a special process with feeding monomer three times,adding initiator twice, coupling once. The polymerization processing cansimply expressed as “St₁+RLi₁+RLi₂+St₂+Bd+X”, in which, St₁and St₂isstyrene introduced into reactor for two times, RLi₁and RLi₂is Butyllithium added for first time and second,“Bd” is butadiene monomer,“X”is coupling agent. S₁and S₂is styrene homopolymerization sectionformed by St₁and St₂,“B” is butadiene homopolymerization section.Thisstar resin with excellent impact resistance and large elongation at breakhave no non-block styrene structure. The number average molecular （Mn）of S₂decide the production’s properties, when Mn is about9500, polymerpossesses non-capture performance in Notch impact test and theelongation is more than300percent.3、Using epoxy soybean oil（ESO） as coupling agent, the couplingmechanism was studied in this thesis, research result is that the fracture ofmolecular chain of ESO occurred at ester functional group firstly, then,the activity chain mainly connected to epoxy group and the reactionactivity of epoxy group was higher than ester. The coupling arm numberaccording to the coupling agent amount ranged from2to3.4、A linear resin was synthesized by adding monomer twice and initiatingonce. The affect of content of styrene non-block structure on properties was studied. The result indicated that with the increasing of non-blockstructure hardness reduced, impact strength and elongation at breakincreased, barely affect optical performance.5、Technology of termination and neutralization process mainly affectsthe light transmittance, haze, yellow index. Using deionized water astermination agent, carbon dioxide as neutralization agent, under thecondition of90℃, terminating10minutes, neutralizing20minutes, theproduct with light transmittance more than89%and haze lower than5%was gained.6、The resin dry technology have a certain effect on production’s yellowindex and melt index. As the temperature of screw and residence timeincrease, product’s yellow index increases but melt index reduces whenscrew temperature is between160℃and180℃. Base of keeping Volatilematter bellow0.2%, low temperature and short time is needed to ensureperfect polymer.