José Miguel Martín-Martínez

Adhesion improvement of SBR rubber by treatment with trichloroisocyanuric acid solutions in different esters

Abstract Ethyl, propyl and butyl acetates (EA, PA, BA, respectively) were used as solvents for trichloroisocyanuric acid (TCI) to chlorinate styrene–butadiene rubber (SBR). Characterization of the treated surfaces was carried out using ATR-IR spectroscopy, scanning electron microscopy (SEM), and contact angle measurements. Stress-strain measurements were also carried out to determine the mechanical properties of the treated rubber. Adhesion properties were studied using a polyurethane adhesive and the failed surfaces obtained after performing T-peel tests were analyzed in order to precisely locate the joint failure. The results showed that the solvent is a key factor in the effectiveness of the chlorination of R2 rubber. The solvents with slower evaporation rate led to more pronounced modifications on the R2 rubber surface. But these solvents could favour the migration of wax from the bulk rubber to the surface creating a weak antiadherent layer that prevented adhesion. The increase in TCI percentage in the chlorinating solution produced more marked modifications on the R2 rubber surface, avoiding the migration of wax. The solvent in the chlorinating solution also affects the effectiveness of the zinc stearate elimination from the R1 rubber surface; however, good adhesion was obtained even though this compound was not completely removed, indicating that the presence of zinc stearate in the rubber formulation did not produce a detrimental effect in the adhesion of SBRs.

Effect of Boron Carbide Filler on the Curing and Mechanical Properties of an Epoxy Resin

The curing process, wear behavior, and mechanical properties of an epoxy adhesive filled with boron carbide (B4C) were studied. Two different particle sizes and amount of reinforcing B4C were tested. One advantage of using B4C is its ability to absorb neutrons, a property of great importance in the nuclear industry. Gel time and degree of curing were measured to evaluate the effect of adding B4C to the epoxy resin. The chemical structure was studied by Fourier Transform Infrared Spectroscopy (FTIR) and the B4C distribution was analyzed by laser confocal microscopy. Dynamic Mechanical Thermal Analysis (DMTA) tests were also carried out to monitor the viscoelastic properties and the glass transition temperature (Tg) of the cured reinforced epoxy. The wear resistance against alumina was measured using a pin-on-disc test, evaluated as mass loss. The wear tracks were studied by Scanning Electron Microscopy (SEM). The bending strength was also studied to assess the degree of interaction between the B4C and the matrix. The results showed that the reinforced epoxy with B4C was very abrasive, wearing the alumina. The reinforced epoxy had excellent mechanical properties that increased with B4C content and with small particles. Moreover, the Tg value decreased slightly upon B4C addition.

Effect of Different Surface Modifications on the Adhesion of Vulcanized Styrene-Butadiene Rubber

Abstract From the above results, the following conclusions may be drawn: 1. A water ultrasonic procedure for cleaning SBR surfaces has been proposed. The peel strengths attained with polyurethane adhesives are not great and increase with the amount and especially with the viscosity of the adhesive. 2. Surface roughening improves the adhesion between SBR and PUA. There are no important changes in peel strength with the amount and viscosity of the PUA. Zinc stearate removal could be responsible for the increase in peel strength. 3. Chlorination of SBR surface increases the peel strength with regard to ultrasonic-cleaned rubber, especially when both SBR test strip pieces are halogenated. This increase depends on the solvent and percentage of TIC, as well as the amount and viscosity of the adhesive. However, the type of solvent for TIC does not induce physical differences in the SBR surface, the variations being explained in terms of the extent of the chlorine reaction with double carbon bonds of butadiene; i...

Surface characterization of synthetic vulcanized rubber treated with oxygen plasma

The surface of a synthetic vulcanized styrene-butadiene rubber (R2) was treated in an oxygen plasma to improve adhesion in joints prepared with a one-component solvent-based polyester-urethane adhesive. The modifications produced on the rubber surface by plasma treatment were assessed using advancing and receding contact angle measurements, x-ray photoelectron spectroscopy, (XPS), infrared-attenuated total reflection spectroscopy and scanning electron microscopy. Adhesion was obtained from T-peel tests of treated R2 rubber/polyurethane adhesive joints. Several experimental variables were considered, such as the radio-frequency power and the length and lifetime of the plasma treatment. The treatment in the oxygen plasma produced a noticeable decrease in contact angle, which can be mainly ascribed to the creation of C-O and C=O moieties on the rubber surface. Advancing and receding contact angles only differed by ∼10°. Depending on the experimental conditions used, some ablation was produced on the surface, which was more noticeable as the length and power of the treatment increased. An adequate performance of adhesive joints was obtained using a power of 50 W and a time for oxygen plasma treatment of <10 min. The changes in the rubber surface remained for 2 h after plasma treatment, as indicated by the variation in peel strength and XPS data. Although improved adhesion was obtained by treating the rubber in an oxygen plasma, the T-peel strength values are not sufficient to assure technical use, probably due to the migration of waxes and zinc stearate to the surface once the treatment was carried out. Finally, sulfur oxidation was produced by the plasma treatment, and for severe conditions solid crystals of a sodium salt of an oxidized sulfur compound (sodium sulphate or an organic sulphate) appeared on the treated rubber surface.

Thermoplastic polyurethane-fumed silica composites: influence of the specific surface area of fumed silica on the viscoelastic and adhesion properties

Fumed silicas of different specific surface area (90-380 m2/g) were added to a thermoplastic polyurethane (PU) solution. After solvent removal, solid fumed silica-PU composites were obtained. The viscoelastic properties of PU were improved by adding fumed silica and only a solid-like behavior in PU-fumed silica composites was obtained. The increase in the specific surface area of the fumed silica up to 200 m2 / g increased the moduli of the composites. Fumed silica-PU interactions were responsible for the improved rheological properties of the composites. The activation energies for viscous flow of the composites were 14-16 kcal/mol and increased as the specific surface area of fumed silica increased. The glass transition temperature (obtained from DMTA and DSC experiments) and the crystallization rate of fumed silica-PU composites decreased compared with PU and also decreased with increasing surface area of the fumed silica. The contact angle values were similar in all the composites and the strength of ...

Surface modifications of a vulcanized rubber using corona discharge and ultraviolet radiation treatments

Two different surface treatments have been applied to a synthetic vulcanized styrene-butadiene rubber (R1): corona discharge and UV treatment. Corona discharge treatment has been carried out on R1 rubber by varying the electrode-sample distance (2–4 mm), the duration (1 to 11 sec) and several parameters in the treatment of R1 rubber with UV treatment (lamp-sample distance between 1 and 5 cm, the duration between 30 sec and 5 min). The effects on both treatments on the surface of R1 were analyzed using contact angle measurements, ATR-IR spectroscopy, Scanning Electron Microscopy (SEM), X-ray Photoelectron Spectroscopy (XPS) and Atomic Force Microscopy (AFM). A noticeable decrease in contact angles was observed on the R1 rubber by applying both treatments, although the modifications produced on the rubber surface were different. Corona discharge mainly affected the morphology of the R1 rubber surface whereas UV treatment mainly modified its chemistry. The migration of zinc stearate was only produced by UV treatment but not with corona discharge. Therefore, the UV treatment of R1 rubber was more aggressive, facilitating the migration of moieties from the bulk to the surface and producing oxygen moieties.

Properties of Polyurethane Elastomers with Different Hard/Soft Segment Ratio

Abstract Three polyurethane elastomers (PU) containing different hard/soft (h/s) segment ratios were prepared. The PUs were characterized using Gel Permeation Chromatography (GPC), DSC, Wide Angle X-ray Diffraction (WAXD). Dynamic Mechanical Thermal Analysis (DMTA), and Stress-controlled rheometry. The surface properties were evaluated from contact angle measurements. The PUs were used as raw materials for solvent-based adhesives, whose adhesion properties were measured from T-peel tests of solvent-wiped polyvinyl chloride (PVC)/polyurethane adhesive joints. The increase in the amount of h/s segment ratio affected the structure and morphology of the PUs, reducing the degree of phase separation and the extent of the secondary interactions between polymer chains. The h/s segment ratio determined the thermal, mechanical, rheological and adhesion properties of the PUs.

Halogenation of styrene-butadiene rubber to improve its adhesion to polyurethanes

Halogenation of styrene-butadiene rubbers has been carried out using solutions containing different amounts (0.1-5 wt%) of trichloroisocyanuric acid in butan-2-one. The treated rubber surface showed increased peel strength in joints made with polyurethane adhesive. The effects of chlorination on the rubber surface were studied using scanning electron microscopy, contact angle measurements, and infrared spectroscopy. It was shown that cracks appear in the rubber surface after halogenation, a factor which favours adhesion; the larger the amount of trichloroisocyanuric acid used, the larger the number of cracks. On the other hand, chlorination of the carbon double bond (butadiene) and the formation of carboxylic acid groups seem to be the most important chemical changes in the chlorinated rubber surfaces. Chlorination increases the surface energy of the rubber, although this increase is a function of the rubber composition. In fact, for a simple rubber formulation, the polar component of the surface energy i...

Surface Characterization of Vulcanized Rubber Treated with Sulfuric Acid and its Adhesion to Polyurethane Adhesive

Abstract Modifications produced on a vulcanized styrene –butadiene rubber surface by treatment with sulfuric acid were studied and several experimental variables were considered. The treatment of R1 rubber with sulfuric acid produced a noticeable decrease in contact angle which was mainly ascribed to an increase in surface energy due to the formation of sulfonic acid moieties and C˭O bonds, and the removal of zinc stearate. The rubber surface swelled and became brittle as a result of the treatment, and when flexed microcracks were created. A rubber surface layer modification was produced with a consequent decrease in tensile strength and elongation-at-break values. The treatment enhanced the T-peel strength of R1 rubber/polyurethane adhesive joints and the locus of failure was cohesive in the rubber. The optimum immersion time in H2SO4 solution was less than 1 min., and the reaction time in air was not found to be critical; the neutralization with ammonium hydroxide and the high concentration of the sulfuric acid (95 wt%) were essential to produce adequate effectiveness of the treatment.

Influence of the hard-to-soft segment ratio on the adhesion of water-borne polyurethane adhesive

Three water-borne polyurethane dispersions were synthesised by the pre-polymer mixing process. Different hard segment contents in the polyurethanes were obtained by varying the diisocyanate/macroglycol (NCO/OH) molar ratio. A decrease in the NCO/OH ratio produced an increase in the mean particle size and in the pre-polymer viscosity, as well as a decrease in the molecular weight of the polyurethane. On the other hand, the lower the NCO/OH ratio, the more crystalline the polyurethane and the lower the resistance to flow at high temperature. Lower NCO/OH ratios improved the thermal degradation stability of the polyurethane. Finally, a high initial adhesion to PVC was obtained in all joints produced with the aqueous polyurethane dispersions and the final adhesion increased as the NCO/OH ratio in the water-borne polyurethane adhesive decreased.