Journal of Elastomers and Plastics recent issues

Studies on the Effect of Novel Antistatic Agent on the Properties of Polyurethane Foam

Wang, J., Yang, K., Zheng, X. — Wed, 04 Nov 2009 08:56:23 PST

Novel antistatic agents containing metal salt were used to prepare polyurethane foam (PUF) in this study. The effects of different conditions such as amount of antistatic agent, type and ratio of metal salt, temperature, relative humidity and time, on the surface resistivity were studied. Typically, the research of replacement of silver metal salt with tin metal salt has been conducted. Antistatic property of these composites illustrates that AgIO₃ metal salt replaced by two-thirds amount of SnCl₄ also shows excellent conductivity. Structure and other properties of these conductive PUF were examined by FTIR, DSC, and TGA. Moreover, the antistatic mechanism of these agents was put up. It was proposed that the metal salt in the antistatic agent might develop a conducting road. This can increase conductivity of the polymeric materials and decrease the corresponding surface resistivity.

Characterization of Microwave-Devulcanized Composites of Ground SBR Scraps

Wed, 04 Nov 2009 08:56:23 PST

The recycling of waste rubber has considerable significance in terms of environmental protection and energy conservation. Considering that most of the relevant literature is concerned with tire recycling, the objective of this study is to develop and characterize styrene-butadiene rubber composites containing only industrial rubber scraps devulcanized by microwave. The styrene-butadiene rubber extruded profile scraps were collected and ground under ambient conditions. The obtained powder styrene-butadiene rubber-r was physically, thermally, and chemically characterized. From the devulcanized styrene-butadiene rubber-r two composites were prepared, varying the exposure time of the powder in the microwave (3 and 4 min). These composites were compared to a control sample supplied by the industry from which the styrene-butadiene rubber extruded profile scraps were collected. Vulcanization parameters were determined by oscillatory disk rheometry. Vulcanized composites were characterized by crosslink density and physical-mechanical properties (Shore A hardness, tensile and tear strength, and compression set) before and after a postcure process. The mechanical properties of the compositions were ~25% for tensile strength and 41% for tear strength compared to the control sample. The results for the crosslink density verified those for the mechanical properties of the composites.

Effect of Metallic Salts of Glutaric Acid on the Formation of {beta}-crystalline Form in Isotactic Polypropylene

Dou, Q., Lu, Q.-L., Li, H.-D. — Wed, 04 Nov 2009 08:56:23 PST

The effects of glutaric acid and the lithium, sodium, potassium, magnesium, calcium, strontium, barium, zinc, and cadmium salts of glutaric acid on the formation of β-crystalline form in isotactic polypropylene (iPP) at the crystallization temperatures 120 and 130°C have been investigated. It is found that glutaric acid and the sodium, potassium, and zinc salts of glutaric acid inhibit the formation of β-crystalline form in polypropylene. Lithium glutarate has a limited positive effect on the formation of β-crystalline form. Magnesium, calcium, strontium, barium salts of glutaric acid exhibit increased β-nucleation abilities with the increasing atomic radii of the combined metals. Cadmium glutarate is a good β-nucleating agent and the formation of β-crystalline form is favored at the crystallization temperature of 120°C. The increases in the orientation of b-axes of the nucleated iPP samples are due to the presences of sodium and zinc salts of glutaric acid.

Comparison of Interaction of Aromatic Solvents in Hybrid and Textile Biocomposites

John, M. J., Thomas, S., Varughese, K.T. — Wed, 04 Nov 2009 08:56:23 PST

Natural rubber was reinforced with sisal—oil palm hybrid fibers. Composites were prepared by varying the weight content of the fibers and chemical modification of the biofibers. The interaction of three different types of aromatic solvents, namely, benzene, toluene, and xylene with the rubber composites was analyzed. Textile composites were also prepared by sandwiching a single sheet of sisal fabric between two pre-weighed rubber sheets. The diffusion behavior of the textile composites in benzene, toluene, and xylene was also analyzed. The mechanics of diffusion was found to be different for hybrid and textile biocomposites. The swelling index factor was also calculated for all the composites. Swelling was found to be predominantly dependent on the aromatic solvent used and chemical treatments. Chemically modified composites were found to be less prone to solvent permeation.

Application of Factorial Design in Determination of Physico-Mechanical Properties of NR/SBR Alloy -- Influence of Sulfur Curing System

Manshaie, R., Hafezi, M., Nouri Khorasani, S. — Wed, 04 Nov 2009 08:56:23 PST

In this research physico-mechanical properties including tensile strength, elongation at break, hardness, resilience, abrasion resistance, and compression set of unsaturated natural rubber and styrene butadiene rubber (NR/SBR) alloy cured by sulfur curing system were investigated. Factorial design method was employed in order to formulate the sulfur curing system. Three different curing agents were used and their effects on physico-mechanical properties of the alloy were investigated. The results show that with increasing each curing agent, curing time and scorch time reduce and maximum torque increases. Tensile strength, % elongation at break, tear strength, and compression set decrease while hardness, resilience, and abrasion increase. The results show that application of factorial design significantly reduces research and development costs by decreasing the number of experimental configurations to be studied and the results are accurate. Results from factorial design procedure very well match the experimental results with accuracy in order of 2% variations.

Compatibilizing Effect of Fluororubber Grafted by {gamma}-Methacryloxypropyltrimethoxysliane in Fluororubber/Silicone Rubber Blends

Guo, J., Zeng, X., Luo, Q. — Wed, 04 Nov 2009 08:56:23 PST

The fluororubber/silicone rubber blends were prepared by using fluororubber grafted by -methacryloxypropyltrimethoxysliane as a compatibilizer. Fourier transform infrared Spectra revealed that -methacryloxypropyltrimethoxysliane has been grafted onto fluororubber backbone. The effect of the compatibilizer content on curing characteristics, stress—strain behavior, mechanical properties, heat aging properties, and oil resistance was investigated. The results showed that the mechanical properties and oil resistance of the blends were improved with increasing of the compatibilizer up to 11.8 wt%. The compatibility of fluororubber and silicone rubber phase was characterized by dynamic mechanical analysis.

Erratum

Wed, 04 Nov 2009 08:56:23 PST

M. J. John, S. Thomas and K. T. Varughese. Comparison of Interaction of Aromatic Solvents in Hybrid and Textile Biocomposites; first published on August 6, 2009, as DOI: 10.1177/0095244308099083. This version is no longer available. The version of record is published in Vol. 41, No. 6, DOI: 10.1177/0095244309099083.

Patents

Wed, 26 Aug 2009 04:04:40 PDT

Effect of Moisture-induced Damage on Fracture Resistance of Rubber-modified HMA Mixtures

Othman, A. M. — Wed, 26 Aug 2009 04:04:40 PDT

The impact of moisture-induced damage on the fracture resistance of rubber-modified hot mix asphalt (HMA) mixture as determined by the critical energy release rate (J_c) was investigated. Crumb rubber content of 15% by weight of binder was adapted. Semi-circular core specimens (76 mm radius and 57 mm thickness) were used for fracture resistance tests. An accelerated moisture damage program was established to evaluate the mixture resistance to moisture damage. Tested specimens were immersed in a water bath at a controlled temperature of 25°C under vacuum of 510 mm Hg at different moisture treatment periods of 0, 1, 2, and 7 days. A relationship between the moisture treatment period and the critical energy release rate was determined. The current investigation revealed a reduction on the fracture resistance and mechanical performance of the moisture treated mixtures. The reduction increased with the increase of moisture treatment period. The results also indicated significant improvement in mix stability, strength, and resistance to fracture and moisture damage when crumb rubber was applied to HMA mixtures.

Mechanical Testing and Characterization of a Swelling Elastomer

Qamar, S.Z., Al-Hiddabi, S.A., Pervez, T., Marketz, F. — Wed, 26 Aug 2009 04:04:40 PDT

Elastomers are being increasingly used for sealing and other applications in the oil and gas industry. Specifically developed elastomers possess durable properties and have the ability to withstand detrimental effects of heat, chemicals, and harsh environments. For successful modeling and simulation of various downhole processes, it is very important to determine the behavior of elastomer materials under realistic well conditions. Of special interest is the class known as swelling elastomers. This article reports some results from experiments conducted on mechanical testing and characterization of an inert (nonswelling) and a water-swelling elastomer (both belonging to the EPDM family) used for sealing purposes by a local petroleum development firm. Experiments were designed and conducted in accordance with standard ASTM test methods. Apart from regularly available testing equipment, some simple test rigs and fixtures were designed and fabricated. Elastomer behavior was tested for hardness, compression set (at different temperatures and for different periods of time), tensile set (for different periods of time), tensile properties (fracture strength and percent elongation), and swelling. In the swelling test, different sample geometries (unconfined samples and samples mounted on steel plate) were tested for a total duration of 1000 h (roughly 45 days) in salt solutions of different concentrations and at different temperatures. Results show that compression set increases with increasing temperature and testing time, while room temperature tensile set also increases with longer testing time. Compared to the inert elastomer (exhibiting nonlinear elastic behavior like normal rubbers), swelling elastomer surprisingly showed linear stress—strain response. As expected, the inert elastomer did not exhibit any change in volume, while the swelling elastomer showed significant volume/thickness increase with increasing test temperature and decreasing salt concentration.

Dynamically Vulcanized PP/EPDM Blends: Effect of Composition and Curing Agents

Nicolini, A., De Campos Rocha, T. L. A., Maldaner Jacobi, M. A. — Wed, 26 Aug 2009 04:04:40 PDT

The comparative study between two curing agents, conventional peroxide (Peroximon) and bismaleimide/dicumyl peroxide combination (BMI/DCP), and the influence of composition in TPE-Vs based on polypropylene (PP) and ethylene—propylene—diene terpolymer (EPDM) were investigated. The materials were characterized by mechanical, hardness, swelling and morphological properties. The TPE-Vs obtained using Peroximon presented lower tensile strength, remarkable lower deformation and swelling degrees than those cured with BMI/DCP. Among all the investigated PP/EPDM compositions, the content of thermoplastic increases the tensile at break. The experimental swelling values are in agreement with the theoretical for the TPE-Vs obtained using BMI/DCP and for the obtained using Peroximon all compositions showed experimental swelling degree higher than the theoretical ones. The hardness is determined by the amount of PP. We also observed in the morphology studies that the rubber domains are smaller and better defined when the BMI/DCP is used.

Effect of Kaolin on Adhesion Property of Epoxidized Natural Rubber-based Pressure-sensitive Adhesive Using Gum Rosin as the Tackifier

Poh, B.T., Chew, C.E. — Wed, 26 Aug 2009 04:04:40 PDT

The viscosity, loop tack, and peel strength of kaolin-filled epoxidized natural rubber (ENR 25 grade) adhesive was investigated using gum rosin as the tackifying resin. Kaolin loading was varied from 10—50 parts per hundred parts of rubber (phr), whereas the gum rosin concentration was fixed at 40 phr. Toluene was used as the solvent throughout the study. Polyethylene terephthalate substrate was coated at various adhesive coating thicknesses, i.e., 30, 60, 90, and 120 µm using a SHEEN hand coater. A HAAKE Rotary Viscometer Viscosity was used to measure the viscosity of the adhesive. Loop tack and peel strength were determined by a Llyod Adhesion Tester operating at 30 cm/min. Results show that viscosity of the adhesive increases gradually with increase of kaolin loading due to the concentration effect of the filler. Loop tack and peel strength, however, show maximum value at 20 phr and 30 phr kaolin, respectively, an observation which is attributed to the maximum wettability and compatibility of adhesive on the substrate.

Admicellar Polymerization of Polystyrene on Natural Rubber Particles

Magaraphan, R., Srinarang, V. — Mon, 28 Sep 2009 07:47:13 PDT

Admicellar polymerization is a reaction for coating a thin-film of polymer on a surface. The process consists of the polymerization of the adsolubilized monomer in the hydrophobic regions of the surfactant bilayers that adsorbed on the substrate surface. In this research, the admicellar polymerization of polystyrene was carried out using micron to submicron size natural rubber particles as substrates. Cetyl trimethyl ammonium bromide (CTAB) was used to form the surfactant template. The adsorption isotherm of CTAB was determined in the absence and presence of salt. Styrene adsolubilization was found to increase with initial styrene concentration and in the presence of salt. The synthesized polystyrene in the molecular bilayer of micelles surrounding the natural rubber particles was characterized by optical microscope, Fourier transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA). The observed morphology of the rubber particles after reaction was clearly two phases, a core-shell structure having the natural rubber core covered by the polystyrene shell. These core-shell particles were spheres and aggregated strongly in the emulsion. Effect of initiator type was investigated. The synthesized products showed core-shell morphology, which was still obtained after heating but after cooling phase inversion occurred and showed polystyrene-rich core and natural rubber-rich shell. Thin lamellar of both components was found in both polystyrene-rich core and natural rubber-rich shell making unique morphology and extended single transition of thermal decomposition. FTIR results show characteristic peaks of natural rubber and polystyrene and the absorbance of styrene increases with increasing styrene content. The TGA result showed that the decomposition temperatures of the products were altered by the amount of polystyrene.

Patents

Fri, 26 Jun 2009 08:01:34 PDT

New Reclaiming Process of Thermoset Polyurethane Foam and Blending with Polyamide-12 and Thermoplastic Polyurethane

Gonella, L.B., Zattera, A.J., Zeni, M., Oliveira, R.V.B., Canto, L.B. — Fri, 26 Jun 2009 08:01:34 PDT

A new method to reclaim thermoset polyurethane (PU) foam by thermo-mechanical degradation using a batch Drais mixer was investigated, and the performance of reclaimed PU in blends with polyamide-12 (PA-12) or thermoplastic polyurethane (TPU) was studied. The reclamation method used disrupts the crosslinked structure of PU, decreasing its degree of crosslinking, which was confirmed through the determination of gel content, and by DSC, TGA and FTIR analyses. Under severe reclaiming conditions, the reclaimed PU was found to retain about half of its initial gel content. The blends of original PU and reclaimed PU (PU-r) with PA-12 and with TPU were prepared using a twin-screw extruder and were characterized with respect to their mechanical properties. For the PA-12/PU 75/25 blend, the addition of PU was observed to toughen the PA-12 matrix whereas for TPU/PU blends, the rubber-like behavior of TPU was not significantly affected by the presence of PU. The remarkable mechanical behavior of the blends attests to the high compatibility of PU-r with both PA-12 and TPU. This may be due to the physical interactions between the blend components, leading to high interfacial adhesion. The reclamation of PU-r before its melt processing with PA-12 or TPU was found to improve the processability during the injection molding of the PA-12/PU-r and TPU/PU-r blends.

Thermal, Chemical, and Morphological Characterization of Microcellular Polyurethane Elastomers

Fri, 26 Jun 2009 08:01:34 PDT

In this study, three different microcellular polyurethane elastomers (MPUE) based on 4,4'-diphenylmethane diisocyanate with different rigid segment contents are prepared (Formulations 1, 2, and 3 with 32, 35, and 42% of rigid segment content, respectively). The MPUE are obtained through a two-step method using a prepolymer system. The samples are analyzed to determine their thermal, morphological, and chemical properties. The thermogravimetric analysis indicates the presence of two degradation stages, referring to the rigid and flexible phases, respectively. The differential scanning calorimetry tests indicate that for the MPUE there was an increase in the glass transition temperature of the flexible phase with an increase in the percent of the rigid phase. An increase in the quantity of the rigid phase present in the MPUE results in greater values for the crosslink density, which in turn results in an increase in the rigidity of the material. The scanning electron microscopy micrographs indicated a large number of closed cells and that a higher rigid segment content give a better cell homogeneity of the samples.

Morphology Development and Melt Linear Viscoelastic Properties of (PA6/PP/PS) Ternary Blend Systems

Mohammadigoushki, H., Nazockdast, H., Mostofi, N. — Fri, 26 Jun 2009 08:01:34 PDT

The morphology development and melt linear viscoelastic properties of PA6/PP/PS (70/15/15) ternary blends were studied. An attempt was also made to predict the morphology development of these blends using the dynamic interfacial tension of the blend components evaluated from the Palierne's viscoelastic model in conjunction with spreading coefficient approach. The blend samples were prepared by melt blending in an internal mixer at temperature of 260°C and rotor speed of 60 rpm. The ternary blend samples exhibited a pronounced low-frequency nonterminal storage modulus whose values were much greater than those predicted for elastic response of the binary blend samples. This was attributed to strong elastic resistance of a core-shell composite droplet formed in the ternary blend samples that was evidenced by the SEM micrographs of these samples. The results predicted based on spreading coefficient concept also suggested a core-shell type morphology in which PP core was encapsulated by PS shell as a composite minor phase dispersed in PA6 matrix. It was demonstrated that there is a close relationship between melt viscoelastic properties and morphology of ternary blends.

Networked Silica with Exceptional Reinforcing Performance for SBR Compounds: Interconnected by Methylene Diphenyl Diisocyanate

Fri, 26 Jun 2009 08:01:34 PDT

A networked silica (NS) prepared by interconnecting silica particles with polymeric methylene diphenyl diisocyanate (MDI) was developed for use as a highly effective reinforcing material for rubber compounds without the need to add silane coupling agents. MDI incorporated onto the silica surface formed networks among neighboring silica particles with urethane linkages and produced NS at low cost. The TEM photographs illustrated the improved dispersion and formation of openings among the silica particles, which could allow easy intrusion of rubber molecules. The NS showed a high reinforcing performance for styrene—butadiene rubber (SBR) compounds, suggesting the possibility of replacing the silica reinforcing systems with coupling agents. Due to the absence of any silane-containing coupling agents, the NS does not suffer the disadvantages associated with coupling agents. Since the NS reinforces rubber compounds by the physical entanglement between rubber molecules and the MDI chains, high loading of the NS is more effective in enhancing the mechanical properties of rubber compounds.

Natural Weathering of Poly (Lactic Acid): Effects of Rice Starch and Epoxidized Natural Rubber

Yew, G.H., Chow, W.S., Mohd Ishak, Z.A., Mohd Yusof, A.M. — Fri, 26 Jun 2009 08:01:34 PDT

Poly(lactic acid) (PLA) composites consisting of PLA, rice starch (RS), and epoxidized natural rubber (ENR50) are compounded using a twinscrew extruder followed by compression molding. Two types of thermoplastic starch are prepared by mixing RS with glycerol and water. Natural weathering tests are performed on the PLA/RS composites in Penang, Malaysia for 2 months. The average mean temperature and mean relative humidity are 29°C and 70%, respectively. Tensile tests are performed to characterize the mechanical properties of the weathered PLA/RS composites. Morphological studies are performed by using scanning electron microscopy (SEM). The tensile properties of weathered PLA/RS composites decreased slightly, on the other hand, the tensile properties of weathered PLA/SG and PLA/SGW composites decreased drastically. The retention-ability of the PLA composites are relatively low, which may be attributed to the photo-degradation of PLA, chain scission of PLA, oxidation degradation on ENR, moisture absorption of RS, and leaching of RS particles. In addition, discoloration, surface roughness, surface cracking, and embrittlement are observed for all PLA/RS composites. The extent of degradation is increased by the addition of ENR, owing to the fact that ENR is susceptible to oxygen attack, and consequently facilitates degradation. The morphological properties of the weathered PLA/RS composites are transformed to a more brittle behavior, indicating that severe degradation has occurred on the PLA/RS composites.

Patents

Fri, 01 May 2009 10:34:43 PDT

Effect of Complex Curatives on the Properties for Ethylene Propylene Diene Rubber/Polypropylene Blends

Tsai, Y., Tsai, P.-Y., Wu, Y.-T., Leu, M.-T., Wu, J.-H. — Fri, 01 May 2009 10:34:43 PDT

This study investigates the effects of different types of curatives at polypropylene (PP) and ethylene propylene diene monomer (EPDM) blend ratios (100 : 40 phr) in dynamically vulcanized products. The thermoplastic vulcanizates are prepared by batch melt mixing of PP with EPDM, using pheolic resin, dicumyl peroxide, hydrosilyation, and complex systems as curatives. Observed changes in curing characteristics and mechanical properties of blends have been correlated with phase morphology, as attested by scanning electron micrographs. On the basis of the obtained results, different curative systems control final vulcanizing characteristics, mechanical properties, morphology, intermolecular interaction, and thermal properties of EPDM/PP blends.

Preparation and Properties of Polyurethanes based on Castor Oil Chemically Modified with Yucca Starch Glycoside

Fri, 01 May 2009 10:34:43 PDT

We present novel polyurethanes from renewable materials of castor oil and starch. Castor oil is transesterified with pentaerythritol in order to obtain a wide range of polyols. Yucca starch is converted into glycoside through transglycosylation reactions with ethylene glycol and glycerol. The glycosides from starch are then chemically incorporated to the castor oil polyols by a second transesterification reaction to generate a sequence of polyol-glycosides with a high level of polyhydroxyl content. These products are characterized by the hydroxyl value, viscosity, and specific gravity as a function of the glycoside type content and the kind of castor oil polyol prepared. MALDI TOF mass spectroscopy is used to find the mass fraction of glycosides and polyol-glycosides. Polyurethanes are synthesized from the polyol-glycosides by reaction with isophorone diisocyanate, under different NCO/OH molar ratios. The polymer characterization is accomplished by Fourier transform infrared analysis, tensile stress—strain tests, Shore A hardness, thermogravimetric analysis, chemical resistance to solvents, scanning electron microscopy, and dynamic-mechanical thermal analysis.

Studies on Sugarcane Bagasse Fiber--Thermoplastics Composites

Youssef, H.A., Ismail, M.R., Ali, M.A.M., Zahran, A.H. — Fri, 01 May 2009 10:34:43 PDT

The influence of thermoplastic/bagasse fiber ratio, as well as electron beam irradiation on the physicomechanical properties of low-density polyethylene (LDPE) and high-density polyethylene (HDPE) composites has been investigated. The concentration of bagasse fibers ranges from 20 to 80 wt%. The results indicate that there is deterioration in the properties as fiber concentration increased; however, it becomes significant only beyond 50% (w/w) bagasse fibers in both LDPE and HDPE composites. Also, the data show that this decrease in the properties is more pronounced in HDPE rather than LDPE composites. It can be noticed that enhancing adhesion between fibers and thermoplastics can be achieved by irradiation of the thermoplastic phase prior to mixing at 10 up to 60 kGy; a maximum improvement in the properties is observed at 40 and 10 kGy for LDPE and HDPE, respectively. From the data it can be seen that the increase in the flexural properties is higher than 100%, while it does not exceed 65% for impact toughness. On the other hand, the reduction in water absorption is not more than 5.5%. Also, examining SEM micrographs reveals that there is some sort of adhesion between fibers and thermoplastics phases.

Properties and Mechanism Research on Polybutadiene Styrene Rubber (SBR) Composites Containing Nano-BaSO4

Wang Jincheng, , Zheng Xiaoyu, , Chen Yuehui, , Lu Zhijun, , Zhu Zengliang, — Fri, 01 May 2009 10:34:43 PDT

Nano-BaSO₄ was treated with surface modification agents and was mixed with different contents into the matrix of polybutadiene styrene rubber (SBR) to obtain composites. The cure characteristics, tensile and wear resistance properties of different nano-BaSO₄ filled SBR composites were studied using scanning electron microscopy (SEM) and the mechanism was analyzed. Experimental results demonstrated that the incorporation of 2 phr 2%-SA modified nano-BaSO₄ powder into neat SBR system can decrease the abrasion loss from 0.160 cm³ to 0.115 cm³, a decrease of about 28%.

Rheology of PVC Plastisol at Instability Region and Beyond (Proposal for Super-High Shear-Rate Coating)

Nakajima, N., Harrell, E.R. — Fri, 01 May 2009 10:34:43 PDT

The coating speed of plastisol is limited to a shear rate below the instability, because the instability results in nonuniform coating. However, there is an indication that beyond instability region the flow stabilizes again at the very high shear rates. If a plastisol is made to flow through the completely enclosed die-assembly with filled channel and let the instability taking place there, a super-high speed coating may be possible at the postinstability region. Although this work does not involve actual experiments, it explores possible mechanisms of flow at the instability and the stable flow beyond. The relation between the inter-particle interaction, (either attractive, repulsive, or neutral) and the flow type, (either clustering or nonclustering flow) is explored in order to aid designing a new device and developing formulations suitable for its use.