Treatment of thermoplastic rubberwith chlorine bleach as an alternative halogenation treatment in the footwear industry

Avoidance of solvents in bonding operations is a current demand in the footwear industry. Halogenation of rubber soles with solutions of trichloroisocyanuric acid (TCI) in different solvents has been successfully used to improve bonding to the leather uppers. In this study, the use of chlorine bleach as an alternative water surface treatment for a rubber has been tested. A thermoplastic block styrene thermoplastic (TR) was treated with bleach to improve its adhesion to a water-based polyurethane dispersion adhesive (PUD). T-peel testing, scanning electron microscopy (SEM), contact angle measurements (ethanediol, 25°C), and infrared spectroscopy (ATR-IR) were used to analyze the modifications produced on the rubber surface. Adhesion values were obtained from T-peel testing of joints produced with similarly treated TR rubber test pieces. Different experimental variables were considered in this study, namely the immersion time (0.5-2 min) in bleach, the active chlorine content (43.9- 55.6 g/l) in the bleach, the addition of a wetting agent (1-octyl-2-pyrrolidone) to the bleach, and the application of the surface treatment using an ultrasonic bath. The treatment with bleach produced the chlorination of the hydrocarbon chains on the TR rubber surface and slightly changed the surface roughness. Chlorination of the TR rubber with bleach (free active chlorine=55.6 g/l) was fast and needed only 30 sec immersion in the reagent mixture to produce high adhesion. Furthermore, the active chlorine content in the bleach was critical to assure an adequate T-peel strength value. The addition of 1-octyl-2-pyrrolidone to the bleach increased the wettability of the rubber surface, although it was necessary to carry out the surface treatment in the ultrasonic bath to obtain adequate adhesion to the PUD adhesive. Thermoplastic styrene-butadiene rubber Water-based polyurethane adhesive Bleach Halogenation Water-based surface treatment Contact angle ATR-IR spectroscopy SEM T-peel strength     

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

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.     

Properties of Polyurethane Elastomers with Different Hard/Soft Segment Ratio

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.     

Surface Characterization of Chlorinated Synthetic Vulcanized Styrene-Butadiene Rubber Using Contact Angle Measurements,Infra-Red Spectroscopy and XPS

The surface of a sulfur-vulcanized synthetic styrene-butadiene rubber (SBR) was treated with ethyl acetate solutions containing different amounts of trichloroisocyanuric acid (TCI). The chlorinated SBR surfaces were characterized using contact angle measurements (water, ethane diol, n-hexadecane), infra-red (IR) spectroscopy and XPS. Chlorination produced an increase of surface free energy which was mainly due to the enhancement of the acid-base component of the surface free energy, which remained almost unchanged when the amount of TCI was increased. Depending on the amount of chlorination agent, several chemical species were present on the SBR surface: i) For low amounts of TCI (up to 2 wt%), mainly chlorinated hydrocarbon and C – O species were present on the surface; ii) For medium amounts of TCI (between 2 and 5 wt%), an excess of unreacted TCI remained on the surface and a relatively small amount of isocyanuric acid was deposited; iii) For high amounts of TCI (larger than 5 wt%), a weak boundary layer (mainly composed of isocyanuric acid) was formed on the surface and thus the effects due to chlorination were decreased. There was good agreement between the experimental results obtained with contact angle measurements and XPS because both provided information on a surface region close to 100 Å, whereas IR spectroscopy results showed deeper penetration of the chlorinating agent into the SBR surface. The estimated thickness of the chlorinated layer was near 5000 Å as estimated from XPS measurements of SBR surfaces modified by argon ion bombardment.     

High polymer/surfactant ratio in the seeded semicontinuous heterogeneous polymerization of vinyl acetate

Vinyl acetate (VAc) was polymerized by a seeded semicontinuous heterogeneous process. Stable latexes with a polymer/surfactant weight ratio of 65 were obtained, which is comparable with the highest value reported in the literature for emulsion polymerization but with the advantage of obtaining smaller particles (average diameter, D_p = 53 nm) which are similar to those obtained by microemulsion polymerization. The surfactant (sodium dodecylsulfate, SDS) concentration used in the recipe (0.32 wt%) is much lower than those typically used in microemulsion polymerization. Although molar masses increased during the continuous monomer addition period, they were small at the end of the reaction (M_n = 69 × 10³ g·mol^–1) and this was attributed to bimolecular termination inside the particles. The values of polymerization rate (R_p) and monomer addition rate (F_m) were nearly the same, indicating that polymerization was performed under monomer starved conditions. POLYM. ENG. SCI., 2013. © 2013 Society of Plastics Engineers     

A Study of the Interaction of Polycyclic Derivatives of Azaquinolizinium Salts with DNA

A series of phenanthro and acenaphtho azaquinolizinium salts was selected as model heterocyclic polyaromatic compounds to study their interaction with deoxyribonucleic acid (DNA). The compounds exhibit a notable native fluorescence ( u em = 450-520 nm) in buffered aqueous solutions, as expected from planar aromatic heterocycles. However, in the presence of increasing concentrations of DNA (0, 10-90 mg/L), a loss of up to 90% of the fluorescence is observed. This fluorescence quenching can be explained by the interaction of the polycyclic ring and DNA. Application of the Stern-Volmer treatment (correlation coefficient 0.9) reveals the existence of a quenching process. The study of the interaction by UV-Vis spectrophotometry showed slight shifts (5-10 nm) in the absorption maxima of all compounds together with a decrease in the absorbance. Viscosimetry experiments confirm the association of these molecules with DNA as indicated by the increase (12-36%) of the reduced viscosity of the solutions in the presence of DNA. Equilibrium dialysis studies confirm that all compounds are bound to DNA (5-50%). These results lead to the conclusion that DNA interaction is due mainly to the carbocyclic system rather than to the heterocyclic moiety, suggesting that it takes place through hydrophobic interactions.     

Bitter potato starch-based film enriched with copaiba leaf extract obtained using supercritical carbon dioxide: Physical–mechanical,antioxidant, and disintegrability properties

Films based on bitter potato starch (BPS) and its blends with chitosan (BPS-Ch) or soy protein isolate (BPS-SPI) loaded with copaiba leaf extract (E) are prepared via the casting method. The physical–mechanical and antioxidant properties of the as-prepared films are compared with those of a control. Moreover, the half-maximal degradation (t₅₀) of the prepared films is calculated by fitting the Hill model to disintegrability kinetic data. Among the analyzed films, BPS-Ch-E exhibits the lowest (p < 0.05) solubility in water and opacity, strongest water vapor-barrier (3.58 × 10⁻¹¹ g m⁻¹ s⁻¹ Pa⁻¹), and highest tensile strength and elongation at break. The Fourier transform infrared spectra of BPS-Ch-E and BPS-SPI-E demonstrate new peaks at 1550, 1239, and 1070 cm⁻¹ corresponding to N H and C O stretching. The BPS-E and BPS-Ch-E surfaces are devoid of scratches and phase separation. The incorporation of E significantly increases the antioxidant activity of the films. BPS-SPI-E and BPS-Ch-E demonstrate the lowest (t₅₀ ≈ 1.4 days) and highest (t₅₀ ≈ 3.5 days) disintegration rates, respectively, among the prepared films. E loading facilitates the development of films possessing beneficial physical–mechanical and antioxidant properties as well as rapid disintegrability, enabling their potential application as a eco-friendly packaging material.     

Synthesis, Characterization and Cold Workability of Cast Copper-Magnesium-Tin Alloys

The use of Mg as an alloying element in copper alloys has largely been overlooked in scientific literature and technological applications. Its supposed tribological compatibility with iron makes it an interesting option to replace Pb in tribological alloys. This work describes the casting process of high-quality thin slabs of Cu-Mg-Sn alloys with different compositions by means of conventional methods. The resulting phases were analyzed using X-ray diffraction, scanning electron microscopy, optical microscopy, and energy dispersive X-ray spectroscopy techniques. Typical dendritic α-Cu, eutectic Cu₂Mg(Sn) and eutectoid non-equilibrium microstructures were found. Tensile tests and Vickers microhardness show the excellent hardening capability of Mg as compared to other copper alloys in the as-cast condition. For some of the slabs and compositions, cold rolling reductions of over 95 pct have been easily achieved. Other compositions and slabs have failed during the deformation process. Failure analysis after cold rolling reveals that one cause for brittleness is the presence of casting defects such as microshrinkage and inclusions, which can be eliminated. However, for high Mg contents, a high volume fraction of the intermetallic phase provides a contiguous path for crack propagation through the connected interdendritic regions.     

Methodology for Predicting the Phase Envelope of a Heavy Crude Oil and Its Asphaltene Deposition Onset

Abstract

We have presented general ideas to develop a new theoretical methodology, based on molecular simulation and equations of state, for obtaining the phase envelope and to predict pressure, volume, temperature (PVT) conditions of asphaltene precipitation by only taking into account the composition of the heavy crude oil and an asphaltene average molecular structure. Those results show that asphaltene precipitation is a reversible thermodynamic process. The precipitated phase is a liquid phase which consists of mainly asphaltene and some heavy fractions from the crude. This methodology can be applied to find complete phase diagrams of different crude oils based on an asphaltene average molecular structure and the composition of crude oil.