SBS Rubber Research Articles

Strategies to improve the adhesion of rubbers to adhesives by means of plasma surface modification

The surface modifications produced by treatment of a synthetic sulfur vulcanized styrene-butadiene rubber with oxidizing (oxygen, air, carbon dioxide) and non oxidizing (nitrogen, argon) RF low pressure plasmas, and by treatment with atmospheric plasma torch have been assessed by ATR-IR and XPS spectroscopy, SEM, and contact angle measurements. The effectiveness of the low pressure plasma treatment depended on the gas atmosphere used to generate the plasma. A lack of relationship between surface polarity and wettability, and peel strength values was obtained, likely due to the cohesive failure in the rubber obtained in the adhesive joints. In general, acceptable adhesion values of plasma treated rubber were obtained for all plasmas, except for nitrogen plasma treatment during 15 minutes due to the creation of low molecular weight moieties on the outermost rubber layer. A toluene wiping of the N2 plasma treated rubber surface for 15 min removed those moieties and increased adhesion was obtained. On the other hand, the treatment of the rubber with atmospheric pressure by means of a plasma torch was proposed. The wettability of the rubber was improved by decreasing the rubber-plasma torch distance and by increasing the duration because a partial removal of paraffin wax from the rubber surface was produced. The rubber surface was oxidized by the plasma torch treatment, and the longer the duration of the plasma torch treatment, the higher the degree of surface oxidation (mainly creation of C–O moieties). However, although the rubber surface was effectively modified by the plasma torch treatment, the adhesion was not greatly improved, due to the migration of paraffin wax to the treated rubber-polyurethane adhesive interface once the adhesive joint was produced. On the other hand, the extended treatment with plasma torch facilitated the migration of zinc stearate to the rubber-adhesive interface, also contributing to deteriorate the adhesion in greater extent. Finally, it has been found that cleaning of SBS rubber in an ultrasonic bath prior to plasma torch treatment produced a partial removal of paraffin waxes from the surface, and thus improved adhesion was obtained.

Monolithic catalysts for the fixed-bed hydrogenation of polymers

Monolithic catalysts were successfully applied in a true fixed-bed hydrogenation of polymers such as SBS rubbers and polystyrene.

Bulk modification of styrene–butadiene–styrene triblock copolymer with maleic anhydride

AbstractThe bulk modification of SBS rubber with maleic anhydride in a mixing chamber of a Haake rheomixer was studied. The effect of temperature, maleic anhydride, and benzoyl peroxide concentrations on the grafting efficiency was evaluated. High grafting efficiency was achieved when the ratio of peroxide and maleic anhydride concentration was high. On the other hand, on this condition high insoluble fraction was generated. The addition of a diamine, 4,4′‐diaminediphenylmethane to the reaction mixture minimizes the amount of insoluble polymer. However, the grafted MAH content also decreases. The graft copolymer was characterized by infrared spectroscopy and the grafting extension was determined by titration. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2953–2960, 2002; DOI 10.1002/app.10355

Pd/Al2O3 Catalysts for Selective Hydrogenation of Polystyrene-block-polybutadiene-block-polystyrene Thermoplastic Elastomers

The Pd catalysts were prepared by impregnating Pd(CH3COO)2 in Al2O3 supports. To investigate the influence of mass transfer on the catalytic performance, the catalysts and the polystyrene-block-polybutadiene-block-polystyrene thermoplastic elastomers (SBS rubber) were prepared with average pore size ranging from 150 to 600 A and molecule weight ranging from 100 000 to 200 000. The test reactions were carried out in a semibatch basket type reactor at 500 psig and temperature ranging from 80 to 180 °C. The experimental results indicated that, among the catalysts of different pore sizes, the catalyst with an average pore diameter of 389 A presented the highest conversion and selectivity to olefinic microstructures for the SBS rubber of 100 000 in hexane. The superior catalytic performance for the catalyst was regarded as the compromise between pore size and the Pd dispersion of the catalyst; catalyst having a larger pore has lower mass-transfer limitation whereas it also has poorer Pd dispersion. Elevating t...

Infrared studies of thermal oxidative degradation of polystyrene- block polybutadiene- block-polystyrene thermoplastic elastomers

Thermal oxidative degradation of a polystyrene- block-polybutadiene- block-polystyrene thermoplastic elastomer (SBS rubber) has been conducted in an in-situ infrared cell. By monitoring the disappearance of trans-1,4 and vinyl-1,2 double bonds and the appearance of the hydroxyl and the carboxyl/ carboxylate groups in the FTIR spectra, the temperature, air, antioxidant, and molecular microstructure dependence of the polymer degradation was studied. The experimental results indicate that the 1,4-polybutadiene portion of the SBS polymer is easier to degrade than the 1,2-polybutadiene portion and the hydroxyl group appears concomitantly with the disappearance of the polybutadiene. Based on data from the temperature-programmed desorption (TPD) of H 2O, it is concluded that the formation of hydroxyl group makes the polymer hydrophilic and promotes the H 2O adsorption on it. The amount of H 2O adsorption varies with the temperature and the process appears reversible. At low temperatures, the moisture adsorbed onto a degraded polymer sample amounts to approximately 7–10% of total hydroxyls. 1 wt% of Irganox 1076 (antioxidant) would effectively thwart the thermal oxidation process even at severe conditions as high as 225 °C for 12 h. No degradation occurs in an air-free environment.

Processable forms of conductive polyaniline

A range of sulphonic acid dispersants have been used to dope polyaniline. If polyaniline is treated with dodecylbenzene sulphonic acid (DBSA) in refluxing toluene a stable dispersion is obtained which is shows a large increase in viscosity with time on heating. Paralleling this observation are related increases in conductivity (up to σ = 150 S/cm) and crystallinity for films cast from the dispersions. Similarly the PANI. DBSA complex may be successfully dispersed in various thermoplastic polymers such as SBS rubber or polymethylmethacrylate by melt mixing to give melt processable materials of high conductivity (up to σ = 10 S/cm) at low loadings of conductive material. The long term environmental stability of the new materials has also been evaluated.

Influence of the dispersed phase upon the behaviour of nylon/rubber blends; crosslinking effect

AbstractNylon 6 and crosslinked SBS rubber blends were prepared. Their impact strength tests demonstrated the possibility of the existence of a maximum in impact strength at a moderate degree of crosslinking level. However, its peak value was not so much eminent as that happened in tensile test or brittle polymer's impact test. This seems due to complex mechanism occurred in dispersed phase. Based on our experimental data, we believe cavitation is important in nylon toughening. Interpretation of nylon toughening mechanism by cavitation and particle deformation is suggested for the reason of low peak value. Even though delamination is also possible, tensile strength data support cavitation in the rubber particle which seems to be more plausible for toughened nylon 6.

Modified Bitumens Containing Thermoplastic Polymers

Abstract The mechanical and viscoelastic behaviour of bitumen, both at high and low temperature, is noticeably improved by addition of thermoplastic polymers such as thermoplastic SBS rubbers and atactic polypropylene. These polymers can be used complementary to each other. Atactic polypropylene decreases the flow of bitumen at room temperature, thus reducing creep. The SBS block copolymer, instead, prevents excessive stiffening of bitumen at low temperature, reducing the brittleness. Characteristics of bitumen-polymer blends depend heavily upon bitumen quality, particularly upon its aromatic content and mixing process.

Stress–strain behavior of a fractionated cariflex SBS rubber

Stress–strain behavior of a fractionated cariflex SBS rubber

Anionic Graft Copolymers. I. Vinylaromatic Grafts on Polydienes

Abstract Lithiated polydienes were readily prepared by direct metalation of the diene polymers with sec-butyllithium and tetramethylethylenediamine in cyclohexane at room temperature. Reaction of the polylithiodienes with styrene or a-methylstyrene formed graft copolymers. Poly-1, 4-butadiene, poly-1, 2-butadiene, cis-poly-1, 4-butadiene, and polyisoprene were the substrates lithiated. The extent of metalation was much greater than previously reported metalations with n-butyllithium and terramethylethylenediamine. The grafting efficiencies, determined by acetone extraction and gel permeation chromatography, were greater than 95%. The physical properties of the graft copolymers are compared as a function of molecular weight, graft site level, and composition. At certain molecular weights, graft site level, and compositions, elastomers are formed without vulcanization. Their properties are comparable to SBS rubber and offer higher melt flow as an advantage.

New Thermoplastic Elastomers. Styrene Grafts on Lithiated Polydienes and Their Hydrogenated Counterparts

Abstract Metalation of diene polymers such as poly (butadiene) and poly(isoprene) with sec-butyllithium and tetramethylethylenediamine in cyclohexane at room temperature forms lithiated polydienes. Reaction of the polylithiodienes with styrene or α-methylstyrene forms graft copolymers. The extent of metalation is much greater than previously reported metalations with n-butyllithium and tetramethylethylenediamine. The grafting efficiencies, determined by acetone extraction and gel permeation chromatography, are greater than 95 per cent. Graft copolymers of poly (styrene) on EPDM rubbers may also be prepared using this technique. The physical properties of the graft copolymers are a function of molecular weight, graft site level, and composition. Products at specific compositions and graft levels are thermoplastic elastomers. Their properties are comparable to SBS rubbers, and offer as an advantage high melt flow. Graft copolymers of poly(styrene) on poly(ethylene) and poly(ethylene-co-butene-1) result from the hydrogenation of the butadiene moeities of graft copolymers of poly (styrene) on 1,4-poly(butadiene) and 1,2 and 1,4-butadiene copolymers, respectively. Complete hydrogenation results in graft copolymers of poly(vinylcyclohexane) on poly(ethylene) and on poly(ethylene-co-butene-1). In both of these cases thermoplastic elastomers result if the proper choice of composition and graft level is made.