Studies on blends of polychloroprene and polybutadiene rubber containing phosphorylated cardanol prepolymer: Melt rheology,cure characteristics,and mechanical properties

Melt rheology, cure characteristics, and mechanical properties of blends of polychloroprene (CR) and polybutadiene rubber (BR) in the presence and absence of phosphorylated cardanol prepolymer (PCP) were studied. The melt rheology parameters of the blends over a wide range of shear rates and temperatures were studied using a capillary rheometer (Rheoflixer SWO). The plasticizing effect of PCP in the blends was indicated by reduction in apparent melt viscosity and activation energy for melt flow. Good compatibility between the blend components (CR and BR) in the presence of PCP was evidenced by the lower values of principal normal stress difference. The self crosslinking behavior of the blends in the presence and absence of PCP was studied at different temperatures, using a Brabender Plasicorder and the kinetic parameters of crosslinking were evaluated. The cure characteristics of blends of CR and BR containing different dosages of PCP (0–10 phr) in a semi efficient vulcanization system were also studied at temperatures ranging from 150°C to 180°C, using an oscillating disk rheometer. The increase in tensile modulus, tensile strength, and tear strength of the vulcanizates in the presence of 5 phr of PCP is presumed to be an indication of reinforcement resulting from accelerated cross linking reaction as evidenced by higher chemical crosslink density index. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3195–3200, 2006     

Study on the self-crosslinking behavior based on polychloroprene rubber and epoxidized natural rubber

This work has studied the impact of curing temperature and rubber compositions on the self-crosslinking behavior of the polychloroprene rubber (CR) and epoxidized natural rubber (ENR) blend. Variation of the temperature and blending ratios, rheological results have shown a better crosslinking result at 160°C with the optimum CR ratio at 75%. Then, Arrhenius equation was applied to verify the crosslinking kinetic and first-order kinetics has been verified. The chemical reaction routes proposed by differential scanning calorimetry have also been analyzed. Moreover, dynamic mechanical analysis and field emission scanning electron micrographs combined with energy-dispersive X-ray analysis were done to evaluate the phase compatibility. Based on the experimental results, a proposal “cross-promotion” reaction is drawn to conclude the self-crosslinking of CR and ENR. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Cross‐linking of ethylene‐octene copolymer (EOC) by dicumyl peroxide (DCP)

Ethylene‐octene copolymer (EOC) was crosslinked by dicumyl peroxide (DCP) at various temperatures (150–200°C). Six concentrations of DCP in range 0.2–0.7 wt % were investigated. cross‐linking was studied by rubber process analyzer (RPA) and by differential scanning calorimetry (DSC). From RPA data analysis real part modulus s', tan δ, and reaction rate were investigated as a function of peroxide content and temperature. The highest s'_max and the lowest tan δ were found for 0.7% of DCP at 150°C. Chain scission was analyzed by slope analysis of conversion ratio, X in times after reaching the maximum. Less susceptible to chain scission are temperatures in range 150–170°C and peroxide levels 0.2–0.5%. Heat of reaction was analyzed by DSC at various heating rates (5–40°C min⁻¹). It was found to be exothermic. By projection to zero heating rate, the reaction was found to start at 128°C with the maximum at 168°C. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Einfluß der diffusion auf die sauerstoffaufnahme bei chloroprenkautschuk

The influence of the film thickness on the course of oxygen absorption of polychloroprene rubber was investigated in the temperature range 90–120 °C. While the nature of the oxygen absorption kinetic curves was changed, the inhibition period of oxidation remained uncharged in the thickness range 4-30 μm. The critical film thickness at which the influence of the oxygen diffusion into the polymer begins to appear, depends on the temperature and is about 10 μm. The limit stage of the oxidation is influenced by the film thickness as well. The apparent activation energy of oxidation – 17 kcal/mole–was calculated from the temperature dependence, and the value 12,1 kcal/mole was obtained from the temperature of the maximum velocity. The results obtained were confirmed by the measurements of the oxidation products by means of infrared spectra.     

Exploring the filler–polymer interaction and solvent transport behavior of nanocomposites derived from reduced graphene oxide and polychloroprene rubber

Aliphatic solvent resistance of polychloroprene rubber (CR) reinforced reduced graphene oxide (RGO) nanocomposites were explored in the temperature range of 30–50 °C using hexane, heptane, and octane. Microstructure-assisted solvent resistant property is evident from transmission electron microscopy images of fabricated composites. Different transport parameters such as diffusion, permeation, and sorption constants were moderate while increasing RGO content. Diffusion mechanism was explained based on the permeating molecule and is found to be close to Fickian mechanism except for heptane. Evaluation of kinetic and thermodynamic parameters shows the ability of nanoreinforcement to alter thermodynamic characteristics and rate constant values. The extent of reinforcement was also evaluated by Kraus equation. From swelling studies, molecular mass between crosslinks was evaluated using Flory–Rehner equation and compared these values with theoretical predictions such as phantom and affine models to analyze the deformation and mobility of the network during swelling. Temperature plays a significant role in the transport of organic solvent through CR/RGO nanocomposites. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48168.     

Pressure dependence of the electric conductance of aqueous solutions of LiCl,KCl and (CH3)4NCl. Correlation of kinetic parameters

The electrical conductivity and the compression of solutions of LiCl, KCl, and (CH₃)₄NCl have been measured as a function of pressure up to 2 kbar at the temperatures 25°, 35° and 45°C in the concentration range 0·1–1 molal. The results are discussed in terms of the transition state theory in relation to kinetic parameters for viscous flow and partial molal volume.     

Therban® – The High Performance Elastomer for the New Millennium

Hydrogenated nitrile rubber (Therban) was introduced in the early 80's by Bayer as an oil‐resistant elastomer for permanent exposure to temperatures between –25°C and 150°C. By specific modification of micro‐ and macrostructural features the service temperature range could be extended. The introduction of bulky side groups hinders the crystallization of methylene sequences along the polymer backbone. The inability to crystallize leads to superior dynamic‐mechanical properties at low service temperatures. High temperature properties are determined by the plateau of rubber elasticity and are mainly influenced by the network density and structure of the crosslinked polymer matrix as well as by the polymer‐filler interactions. The temperature dependence of the latter causes a decline in the reinforcement properties of filler and polymer matrix at elevated temperatures. Above 150°C a deterioration of the polymer network is observed for standard HNBR grades. This service temperature limit can be increased by ca. 10°C being equivalent to a doubling of the service life‐time by the proper use of Therban HT.     

Studies on the alcoholysis of some seed oils

The effects of time and temperature on the alcoholysis of rubber seed, melon seed, linseed, and soyabean oils have been studied. The following temperatures were investigated: 200, 220, 245, and 260°C. Litharge (PbO) was used as the alcoholysis catalyst. The optimum alcoholysis temperature was found to be 245 ± 2 °C for each of the oils. At lower alcoholysis temperatures (<245°C), there is the preferential alcoholysis of seed oils derived from unsaturated acid; and the general alcoholysis rates were found to be in the following order: linseed oil ≈ rubber seed oil ≥ soyabean oil ≈ melon seed oil. The alcohol‐solubility of the oils is generally observed to begin at 42–45% conversion of oils to monoglycerides. The α‐monoglyceride contents of the alcoholysis mixtures of rubber seed and linseed oils were generally similar at methanol tolerance, and higher than those of melon seed and soyabean oils. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1826–1832, 2000     

Short‐term effect of distilled water,seawater and temperature on the crushed and interlaminar shear strength of fiber reinforced plastic composites made by the newly proposed rubber pressure molding technique

Fiber reinforced plastic (FRP) composites are used in adverse environmental conditions i.e., variation of temperature, humidity, seawater, acidic water, chemicals, organic fuels, etc. It is important to investigate the crushed and interlaminar shear strength (ILSS) behavior of these composite materials under adverse conditions. This study shows the effect of temperatures, seawater and distilled water on crushed and ILSS of glass fiber reinforced polyester composite panels made by a recently developed process known as rubber pressure molding (RPM) technique over a range of temperature from 0 to 150°C. The fiber volume fraction in the composite varies from 30 to 60%. The RPM technique is based on the matching die set, where the die is made of hard metal like steel and the punch from flexible rubber like materials. The use of flexible rubber punch helps to intensify and uniformly redistribute pressure (both operating pressure and developed hydrostatic pressure due to the flexible rubber punch under compression) on the surface of the complex shaped product. Natural rubber was used to prepare a rubber punch in this investigation. For performance evaluation of FRP composites made by RPM technique, FRP composites were also made by the conventional method and tested at the same temperatures. It is observed that the crushed and ILSS of FRP composites decreases towards higher extreme of the temperature range selected. FRP composites made by RPM technique show higher crushed and ILSS over the temperature range of 0–150°C compared to the FRP composites made by conventional process. Again crushed and ILSS increases with increasing fiber volume% in the composites made by both techniques. In addition to these results the crushed and ILSS decrease with dipping time both in distilled and seawater. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers.     

Synthesis,Curing Behavior and Characterization of Epoxyacrylate and Triethylamine Cured Epoxy Resin of 1,1′-Bis(3-methyl-4-hydroxy phenyl) cyclohexane

Epoxy resin of 1,1′-bis(3-methyl-4-hydroxy phenyl) cyclohexane (EMC) and its acrylate (EMCA) have been synthesized and characterized. EMC has been cured by 5–25% triethyl amine at 100°C. The cured samples are characterized by solubility, IR, DSC and TGA at 10°C/min heating rate in nitrogen atmosphere. The associated kinetic parameters for EMCA, EMCT-5 and EMCT-20 have been determined according to Freeman-Anderson method and discussed. It is observed that EMCA and EMCT-20 have almost same thermal stability (300–308°C) but for EMCT-5 it is slightly lower (285°C). Cured samples followed fractional order degradation (0.63–1.44). In case of EMCT-5, all determined kinetic parameters are marginally lower than those of EMCA and EMCT-20.     

Epoxy–imide resins from N‐(4‐ and 3‐carboxyphenyl)trimellitimides. I. Adhesive and thermal properties

Epoxy–imide resins were obtained by curing Araldite GY 250 (diglycidyl ether of bisphenol‐A and epichlorohydrin; difunctional) and Araldite EPN 1138 (Novolac–epoxy resin; polyfunctional) with N‐(4‐ and 3‐carboxyphenyl)trimellitimides derived from 4‐ and 3‐aminobenzoic acids and trimellitic anhydride. The adhesive lap shear strength of epoxy–imide systems at room temperature and at 100, 125, and 150°C was determined on stainless‐steel substrates. Araldite GY 250‐based systems give a room‐temperature adhesive lap shear strength of about 23 MPa and 49–56% of the room‐temperature adhesive strength is retained at 150°C. Araldite EPN 1138‐based systems give a room‐temperature adhesive lap shear strength of 16–19 MPa and 100% retention of room‐temperature adhesive strength is observed at 150°C. Glass transition temperatures of the Araldite GY 250‐based systems are in the range of 132–139°C and those of the Araldite EPN 1138‐based systems are in the range of 158–170°C. All these systems are thermally stable up to 360°C. The char residues of Araldite GY 250‐ and Araldite EPN 1138‐based systems are in the range of 22–26% and 41–42% at 900°C, respectively. Araldite EPN 1138‐based systems show a higher retention of adhesive strength at 150°C and have higher thermal stability and T_g when compared to Araldite GY 250‐based systems. This has been attributed to the high crosslinking possible with Araldite EPN 1138‐based systems arising due to the polyfunctional nature of Araldite EPN 1138. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1729–1736, 2000     

Isothermal oil shale pyrolysis. 2. Kinetics of product formation and composition at various pressures

A rich (250¦t^?1) Green River oil shale was retorted in a helium atmosphere. Isothermal, isobaric retort runs were conducted over a temperature range of 648–773 K (375–500 °C) and a pressure range of 78–765 kPa (11.3–111 psia). Oil was collected as a function of time. A deasphaltened, dry whole oil product (DDWO) was then separated into five fractions: polars (P), ‘weak’ polars (WP), saturates (S), aromatics (A), and olefins (O). One objective of this work was to determine the effect of pressure on the kinetic rate expressions for product oil and oil fraction formation. As the system pressure increased the kinetic rate constants, and, consequently, the product yield decreased. A second objective of the experimental programme was to determine kinetic rate constants for the five oil fractions. A first-order kinetic rate expression was utilized and kinetic parameters were determined for the product oil and oil fractions at each temperature and pressure studied. The kinetic rate constants flow an Arrhenius temperature dependence in the region 688–773 K (415–500 °C); at lower temperatures a change in the activation energy is observed.     

The degradation of guayule rubber and the effect of resin components on degradation at high temperature

Degradation of pure guayule rubber and rubber in the presence of stearic, oleic, linoleic, and linolenic acid, has been studied at high temperatures (from 150°C to 600°C) using thermogravimetric analysis (TGA). On-line mass spectrometric analysis of the products of decomposition has also been done to understand the mechanism of degradation. Degradation of rubber starts around 230°C in air and 330°C in nitrogen. Presence of acids changes the onset of degradation, because of low decomposition temperature of the acids. In the derivative curve, there is one T_max for degradation in nitrogen; two for rubber; and three for rubber containing acids are observed for degradation in air. The activation energy of degradation, as observed by isothermal kinetics, in the 1–10% weight loss region, is 225 kJ/mol in nitrogen and 167 kJ/mol in air. In the 10–100% region, however, the activation energy of degradation measured by the Freeman and Carroll method using dynamic thermogravimetry, is 239 kJ/mol in both nitrogen and air atmosphere. The main products of pyrolysis in inert atmosphere are propylene, propane, isobutylene, methyl butene, isoprene, 2,3-dimethyl cyclopentene, octene, 2,4-dimethylcyclohexene, dipentene, etc. Isoprene is found to be the most abundant. Fragments having m/e values of 136, 121, 107, 93, 79, and 53 are also produced in large quantities. The ratio of concentration of dipentene to isoprene increases marginally with temperature. The concentration of other fragments however increases drastically with temperature. The additives have no effect on the nature of products obtained. The conversion to different fragments depends upon the temperature of degradation and the stability of intermediate products. All smaller molecules are obtained from either dipentene or isoprene. A mechanism of formation of these products has been suggested.     

Effects of temperature on interlaminar fracture toughness of fibre reinforced plastic composites made by newly proposed rubber pressure moulding technique

Abstract

The present paper has investigated the effect of temperatures (i.e.?70–100°C) on the interlaminar fracture toughness (ILFT) of fibre reinforced plastic (FRP) composite panels made by a recently developed process known as the rubber pressure moulding (RPM) technique. The RPM technique is based on the matching die set, where the die is made of hard metal like steel and the punch from flexible rubber like materials. The use of flexible rubber punch helps to intensify and uniformly redistribute pressure (both operating pressure and developed hydrostatic pressure due to the flexible rubber punch) on the surface of the product. Natural rubber was used to prepare rubber punch in this investigation. For performance evaluation of FRP composites made by the RPM technique, FRP composites were also made by conventional method and tested at the same temperatures. It is observed that Mode I ILFT of FRP composites decreases towards higher and lower extremes of the temperature range selected. FRP composites made by the RPM technique show a higher Mode I ILFT over the 25–100°C temperature range than those made by the conventional process.     

Formation of poly(butylene terephthalate): Secondary reactions studied by model molecules

The secondary reactions occurring in the formation poly(butylene terephthalate), leading to thermal degradation (in the temperature range 210°–280°C) or giving rise to tetrahydrofuran (in the temperature range 160°–190°C) have been kinetically studied with the aid of model molecules: 1,4-butylene dibenzoate and 4-hydroxybutyl benzoate. Some kinetic parameters have been determined; the effect of temperature and of catalysts and stabilizers has been considered and a mechanism is proposed for the formation of tetrahydrofuran from hydroxyl end groups.     

The selectivity changes in 1-hexene isomerization and its relation to acid properties of Pd/SAPO-11, SAPO-11, HZSM-5, and H-mordenite catalysts

The activity and selectivity patterns for 1-hexene isomerrzation have been compared in the temperature range of 150–450°C for four different kinds of acidic zeolites (H-mordenite, HZSM-5, SAPO-11 and Pd/SAPO-11) differing both ir acid properties and geometric structure. At lower reaction temperatures (150–175°C) the predominant reaction pathway was double bond shift(DBS) and was not influenced by the type of catalyst. At higher temperatures significant shifts in selectivity were observed from DBS to cracking (C) or skeletal rearrangement (SR) depending on the type of catalyst. Temperature programmed desorption (TPD) patterns of chemisorbed NH₃ were also determined. Three different peaks were found for the most of TPD patterns. The first peak might be associated with Lewis acidsite, and the other two peaks at higher temperatures might be associated with Brönsted acid-sites. It was found that significant loss of strong Brönsted acidity upon Pd loading on SAPO-11. A selectivity correlation at 350°C showed strong dependence of DBS and cracking on total acidity. The reaction seems well suited for investigation of the interrelation between pore structure and surface acidity in terms of these selectivity factors.     

Effect of thermal aging on electrical conductivity of the 2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid‐doped polyaniline fiber

The thermal characteristics of inherently conductive polyaniline (PANi) fiber have been studied using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Fibers show five major weight losses at ∼100°C, 165°C, 215°C, 315°C, and 465°C, which are associated with the removal of moisture, residual solvent, decompositions of the sulfonic acid and degradation of PANi fiber, respectively. The 2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid (AMPSA) that dopes the PANi (in fiber form) performs two‐stage decompositions. The conductivity of the drawn fibers aged at 50°C, 100°C, 150°C, and 190°C under vacuum for various periods of time decreases, particularly at temperatures higher than 100°C. The reduction in conductivity of the fiber aged at temperatures lower than 100°C is mainly due to the evaporation of the residual solvent (15–20% in the as‐spun fiber). Further decrease in conductivity of the fiber aged at temperatures higher than 100°C is caused by the decomposition of the dopant AMPSA. The temperature‐dependent conductivity of the fiber was measured at 15 K (−258.5°C) to 295 K (21.5°C). The conductivity of both aged and un‐aged fibers is all temperature activated, however, the conductivity of the un‐aged fibers is higher than that of the aged fibers. Although a negative temperature coefficient was observed in the temperature range from 240 K (–24.5°C) to 270 K (–3.5°C) for the un‐aged fibers, it was disappeared when the fibers were thermal aged at 100°C for 24 h in vacuum oven. These results indicate that the residual solvent trapped inside the fiber enhanced the electrical conductivity of the fibers and its “metallic” electrical conductivity at temperatures ∼263 K (–10°C). © 2001 John Wiley & Sons, Inc. † J Appl Polym Sci 79: 2503–2508, 2001     

Crystallization kinetics of polyphenylene sulfide

The crystallization kinetics of unfilled and glass-reinforced grades of polyphenylene sulfide has been investigated by using differential scanning calorimetry. The maximum rate of crystallization is observed at about 170°C. From the crystallization data, it is recommended that the molding parameters should be so specified that the polymer spends 10–15 s over the temperature range of 155–190°C during cooling, before demolding, in order to ensure stable morphology of the molded part. The glass fibers have an accelerating influence on crystallization resulting in a 15–25% reduction in crystallization time. The kinetic data have been interpreted by using Avrami analysis followed by a discussion of the possible crystallization mechanisms.     

Properties of fullerene‐containing natural rubber

Addition of fullerene in concentration between 0.065 and 0.75 phr increases Schob elasticity, hardness, and modulus of NR‐based rubber. There is no substantial influence of fullerene on T_g, tan δ, and G‐modulus all evaluated by DMA at twisting within a temperature range ?150 to ?50°C (glassy state). At temperatures between 0 and 150°C (rubbery state) it is different, namely an increase in modulus and some changes in the slope of segments in G(T) curves were observed. It could be resulted from additional strong physical junctions of the rubber network. This suggests the growth of degradation energies of the branching junctions and related rise in the aging resistance as concentration of fullerene increases. Simultaneously, it could be expected some reduction of tire temperature at service. Because of this, introduction of fullerene could be reasonable for tread rubbers in case of reduction of its price. Permittivity and dielectric loss angle are correlated with fullerene concentration. Compounding technology when fullerene dispersed within carbon black is mixed with raw rubber on available machines could be easily implemented in the industry. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 390–398, 2006     

High‐resolution thermogravimetry/coupled mass spectrometry analysis of flame‐retardant rubber

A bromobutyl rubber composition containing a variety of conventional flame retardants, such as Saytex (decabromodiphenyl oxide), Sb₂O₃, chlorinated paraffin wax, and polychloroprene rubber, was prepared and used to coat nylon 6 fabric in a laboratory‐coating device. An attempt was made to evaluate the decomposition profile, the evolved gases, and the kinetics of the decomposition process at a dynamic heating rate with high‐resolution thermogravimetric analysis (HR‐TGA). HR‐TGA was used with mass spectrometry for evolved gas analysis (EGA). The HR‐TGA results were compared with results from conventional thermogravimetric analysis (TGA) at a constant heating rate; the former offered sharp transitions, an economic timescale, and an accurate activation energy. The resolution optimization for stability analysis and the effect of its variation on the kinetic parameters offered better results for HR‐TGA than conventional TGA. A lifetime and temperature relationship was evaluated in HR‐TGA with Toop's method, and it was observed that the shelf life decreased sharply with temperature. The effluents HBr, HCl, Br ·, and Cl ·, generated between 210 and 496°C during EGA, were correlated with the thermal stability and fire‐retardancy behavior of the material. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2051–2057, 2003