Effect Of Organoclay Content Research Articles

Modified resol type phenolic resin nanocomposites as surface metal coatings

AbstractNanocomposites based on resol resin as a matrix and prepared organoclay, from Egyptian bentonite clay, as reinforcement material were synthesized. The effect of organoclay content (i.e., 0.5, 1.0, 1.5, 2.0, and 2.5 phr) on the properties of the prepared samples with respect to the prepared composites and resol resin with no clay was investigated. The prepared samples with higher organoclay content (i.e., 2.0 phr) were modified with epoxy or/and urethane resin and characterized using transmission electron microscope (TEM), X‐ray diffraction (XRD), and Fourier transform infrared measurements (FTIR). TEM showed uniform dispersion of the clay while XRD showed exfoliated structures. FTIR measurements confirmed the bond formation between epoxy or/and diisocynate with phenolic hydroxyl groups of resol resin. Mechanical properties, chemical resistance, thermal properties, and electrical volume resistivity were studied. Results showed that epoxy modified resol resin film samples with 2.0 phr organoclay exhibited higher adhesion and scratch hardness values, higher chemical resistance, thermal stability, and lower electrical conductivity compared with mixed epoxy/urethane and urethane samples as well as unmodified resol resin nanocomposite film samples. The samples could be useful as surface metal coatings.

Effect of organoclay content on mechanical and rheological properties of dynamically cross-linked acrylonitrile-butadiene rubber/poly(ethylene-co-vinyl acetate)/organoclay nanocomposites

Blends of poly(ethylene-co-vinyl acetate) (EVA) and acrylonitrile-butadiene rubber (NBR) with NBR content of 50 wt% and organoclay (OC) contents of 1, 3, 5 and 7 wt% have been prepared and cross-linked with 0.3 wt% dicumyl peroxide (DCP) in an internal mixer. The results obtained from x-ray diffraction and transmission electron microscopy for the uncross-linked nanocomposites containing 7 wt% OC show that although a part of the nanofiller layers are exfoliated, the rest of the particles remained almost intercalated. However, it is found that cross-linking with DCP markedly increased the amount of exfoliated platelets. The results also reveal that gel content and cross-linking rate slightly increased in the presence of the OC. The analysis of data obtained from the tensile experiments indicates that the tensile modulus and yield stress of the nanocomposites are superior to those of the unfilled blend and the values improve with the increase in the OC content. Apart from the value of strain at break, all other mechanical properties studied are found to be higher for the cross-linked nanocomposites than those of their uncross-linked counterparts. Moreover, the relaxation ratio and relaxation rate index are decreased with an increase in the OC content for the uncross-linked and cross-linked materials.

Poly(vinyl alcohol) Hydrogel/Chitosan-Modified Clay Nanocomposites for Wound Dressing Application and Controlled Drug Release

Poly(vinyl alcohol) hydrogel films containing (1-5% (w/w)) chitosan-modified montmorrilonite (CsMMT) were prepared through phase separation method for wound dressing application. The prepared nanocomposites were characterized by Fourier transform infra-red (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The effects of organoclay content on gel fraction, water vapor permeability, water uptake and tensile/rheological properties of films were also investigated. The XRD patterns and TEM micrographs show intercalated/partially exfoliated morphology of nanocomposites. The strong interactions between the polymer matrix and silicate layers via the formation of hydrogen bonds increase the gel fraction and tensile strength of hydrogels. It was found that the equilibrium water absorption, water diffusion coefficient and water vapor permeability were strongly affected by crystallite size of PVA macromolecules and tortuous path originated from CsMMT. The most appropriate results for the examined properties were obtained for 3% CsMMT content (w/w). The rheological results indicated a dominant elastic property and strong network structure for the hydrogels. The wound dressing films were loaded with nitrofurazone (NFZ) and their drug release behavior was studied at simulated wound condition. The drug loading and the release rate of NFZ showed a dependency on the quantity of CsMMT in the membrane. The interaction between NFZ and CsMMT together with tortuosity due to the presence of silicate layers, controlled the duration of total drug release to over 6 days. A Fickian diffusion mechanism was found for the drug release from the nanocomposite membranes.

New approach for preparation of dry natural rubber nanocomposites through acid‐free co‐coagulation: Effect of organoclay content

ABSTRACTNatural rubber (NR) vulcanizates exhibit good mechanical properties compared to vulcanizates of synthetic rubbers. Incorporation of a conventional filler at higher loadings to NR enhances its modulus, while reduction in tensile strength and elongation. This paper presents a new strategy for development of a NR‐clay nanocomposite with enhanced mechanical properties by incorporation of lower loadings (2–8 phr) of cetyl trimethyl ammonium bromide modified montmorillonite clay (OMMT‐C) under acid‐free environment. The effect of OMMT‐C loading on cure characteristics, rubber‐filler interactions, crosslink density, dynamic mechanical thermal properties, and mechanical properties were evaluated. Incorporation of OMMT‐C accelerated the vulcanization process and enhanced mechanical properties. X‐ray diffraction analysis and scanning electron microscopy images revealed that the formation of intercalated clay structures at lower OMMT‐C loadings, and clay aggregates at higher loadings. A nanocomposite at OMMT‐C loading of 2 phr exhibited the best balanced mechanical properties, and was associated with highest crosslink density and rubber–filler interactions. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46502.

Morphology and mechanical properties of polypropylene/ethylene acrylic acid/maleic anhybride-grafted polypropylene/organoclay nanocomposites

Polypropylene (PP)/ethylene acrylic acid (EAA)/maleic anhybride-grafted PP (PP- g-MA)/organoclay nanocomposites were prepared using the melt mixing technique, and PP- g-MA and EAA were employed as the compatibilizers. The sodium montmorillonite (MMT) were pretreated with high-speed airflow pulverization method and then grafted using γ-glycidoxypropyltrimethoxysilane, followed by modification using trihexyltetradecylphosphonium chloride cation with supercritical carbon dioxide as the reaction medium (the obtained product was abbreviated as OGMMT). The modification of MMT was characterized by thermogravimetric analysis, X-ray diffraction (XRD), and scanning electron microscopy. The effect of organoclay content on microstructure and mechanical properties of PP/EAA/PP- g-MA/OGMMT nanocomposites was investigated by XRD, transmission electron microscopy, dynamic mechanical analysis, tensile strength, notched impact strength, flexural strength, and flexural modulus. The results show that the OGMMT has a high weight loss, a large d-spacing increment, and exfoliation predomination structure. The addition of compatibilizers benefited the formation of exfoliated structure and the dispersion of OGMMT in PP matrix, and hence, enhanced the storage modulus ( G′) below the glass transition temperature ( Tg), storage modulus ( G″), Tg, tensile strength, flexural strength, and flexural modulus of the nanocomposites. Furthermore, with the increasing OGMMT content, the nanocomposites exhibited very inconsiderable alteration in the clay dispersion level and enhanced G′ below the Tg, G″, tensile strength, flexural strength, and flexural modulus of the nanocomposites, whereas the Tg was invariant. As a whole, the introduction of compatibilizers and OGMMT led to the reduction of notched impact strength, which also nearly linearly decreased with increasing clay content.

Co-continuous structural electrolytes based on ionic liquid, epoxy resin and organoclay: Effects of organoclay content

As a vital part of structural power composites, structural electrolyte should achieve ionic conducting and load bearing functions simultaneously. In the present work, a novel method was established for optimizing the morphology and multifunctionality of a liquid/epoxy based structural electrolyte by adding different contents of organoclay (organically modified layered silicates, OLS). The OLS content had a substantial effect on the liquid/epoxy co-continuous morphology. The introduction of OLS changed the epoxy microstructure from the interconnected flakes to the parallel ridges. The increase of OLS content led to a more compact epoxy network and a more interpenetrated conductive phase. However, an excessive amount of OLS could cause the agglomeration and make the morphology parallel interconnected bars. The variation in morphology accounted for the multifunctionality increase in the structural electrolytes. The optimal formulation was determined with the best properties of 211MPa in tensile modulus and 0.09mS/cm in ionic conductivity, approaching the inferior limit of the multifunctional performance for a structural electrolyte. As a promising candidate for structural power composites, this co-continuous structural electrolyte containing ionic liquid, epoxy resin and OLS shows great potential to be used in the multifunctional energy storage devices.

Synthesis and characterization of cationic gemini surfactant modified Na–bentonite and its applications for rubber nanocomposites

A cationic gemini surfactant (N‐isopropyl‐N, N‐dimethyldodecan 1‐aminium bromide) was synthesized by quaternization reaction. The synthesized surfactant was characterized by Fourier transform infrared (FTIR) and proton nuclear magnetic resonance (1H NMR) spectroscopy. Modified Na–bentonite (organoclay) was obtained by the intercalation of a gemini surfactant between the layers of sodium bentonite and characterized by X‐ray diffraction (XRD), transmission electron microscopy (TEM), FTIR, thermogravimetry–differential thermal analysis (TGA–DTA) and differential scanning calorimetry (DSC) techniques. The results of XRD, TEM, FTIR, TGA, and corresponding DSC analysis indicate that gemini surfactant has been successfully intercalated into the clay layers. Rubber‐based nanocomposites have been prepared by incorporating various concentration of organically modified bentonite on to natural rubber/styrene–butadiene rubber (NR/SBR) rubber blend (75/25) using two roll mill. Effect of organoclay content on XRD, curing, mechanical, and scanning electron microscopy (SEM) properties of the nanocomposites are investigated. The morphological study showed the intercalation of nanoclay in NR/SBR blend chain. It was found that the organoclay decrease the optimum and scorch time of the curing reaction, increase maximum torque and the curing rate, which was attributed to the further intercalation during vulcanization process. Mechanical properties such as tensile strength, modulus and elongation at break have improved. POLYM. COMPOS., 38:396–403, 2017. © 2015 Society of Plastics Engineers

Polypropylene/organoclay nanocomposites prepared using a Laboratory Mixing Extruder (LME): crystallization, thermal stability and dynamic mechanical properties

Nanocomposites based on polypropylene and surface modified nanoclay (organoclay) masterbatch were prepared via melt blending using a Laboratory Mixing Extruder (LME). This work focused on the study of crystallization, thermal stability and dynamic mechanical properties of the nanocomposites. The effect of organoclay content (5, 10, and 15 wt.%) on non-isothermal and isothermal crystallization of the nanocomposites was studied by Differential Scanning Calorimetry (DSC). Thermal stability and dynamic mechanical properties of the nanocomposites were investigated by Thermogravimetric Analysis (TGA) and Dynamic Mechanical Analysis (DMA), respectively. The DSC results showed that the organoclay played an important role in the crystallization of nanocomposites by acting as “nucleating agent” (heterogeneous nucleation). It was confirmed by the appearance of second crystallization peak, which was attributed to crystallization process induced by heterogeneous nucleation of organoclay. There were also a crystallization temperature shift, a reduction in half-time crystallization (t 1/2), and an increase of crystallization kinetic constants of the nanocomposites. The TGA results showed that the addition of organoclay significantly increased the thermal stability of PP matrix, which was likely due to the characteristic and labyrinth effect of layered silicates/clays dispersed in PP matrix, and also the formation of multilayered carbonaceous–silicate char. A well-known Coats-Redfern method was used to evaluate the kinetic of thermal decomposition. Additionally, the stiffness characteristic of organoclay also greatly improved the dynamic mechanical properties (i.e. storage modulus, G′) of the nanocomposites. The DMA results demonstrated that the resistance and durability of PP/organoclay nanocomposites against applied stress and thermal were higher than the PP matrix.

A study on the effects of organoclay content and compatibilizer addition on the properties of biodegradable poly(butylene succinate) nanocomposites under natural weathering

Biodegradable poly(butylene succinate)/organo-montmorillonite nanocomposites were prepared at different organo-montmorillonite loadings, using maleic anhydride-grafted poly(butylene succinate) as compatibilizer. Poly(butylene succinate) nanocomposites were exposed to outdoor natural weathering for 180 days. Weight loss and decrease in mechanical properties after weathering revealed the degradation of poly(butylene succinate). Natural weathering caused photo-oxidation on poly(butylene succinate), leading to the formation of degraded products, as manifested in Fourier transform infrared spectroscopy. Gel permeation chromatography showed a significant reduction in molecular weight after weathering. It was noted that poly(butylene succinate) nanocomposite exhibited lower degradability as compared to neat poly(butylene succinate), due to the enhanced barrier properties after the addition of organo-montmorillonite. However, the incorporation of maleic anhydride-grafted poly(butylene succinate) increased the degradability. Degree of crystallinity of poly(butylene succinate) reduced after weathering, as shown in differential scanning calorimetry. Scanning electron microscopy analysis revealed fungal and bacterial colonization on the sample surface. In addition, the isolation and identification of bacterial strain were also performed.

Nanocomposites based on thermoplastic polyurethane, millable polyurethane, and organoclay: effect of organoclay content

Dynamically vulcanized thermoplastic polyurethane/millable polyurethane blend and its organoclay-based nanocomposites with co-agent assisted peroxide curative system were prepared by melt intercalation technique using batch mixer followed by compression molding to make sheets. Fourier transform infrared spectroscopy analysis revealed the presence of interfacial interactions due to hydrogen bonding of PUs with organoclays. X-ray diffraction and transmission electron microscopy analyses qualitatively established the uniform dispersion of organoclays within the PU matrix up to 5 phr Cloisite 30B (C30B) content and exhibited small aggregates at higher C30B loading. Mechanical testing reported significant improvement in tensile strength with addition of C30B up to 5 phr loading and then reduced a little but tensile modulus continuously increased with increase in C30B loading. Dynamic mechanical analysis (DMA) evaluated that the storage modulus ( E′) and glass transition temperature ( Tg) of both hard and soft segments of PU matrix substantially enhanced by incorporation of C30B. Thermogravimetric analysis revealed that the thermal stability of the PU matrix noticeably increased with C30B loading. Melt rheological characterization reported that all samples showed a strong shear thinning behavior within the scanned frequency range.

Effect of organoclay content on the mechanical properties of ethylene‐vinyl acetate copolymer/ multi‐walled carbon nanotube/organoclay foams

AbstractThe main objective of this study is to obtain ethylene‐vinyl acetate copolymer (EVA)/multi‐walled carbon nanotube (MWCNT)/organoclay foams with improved mechanical properties without increase of their density, compared with EVA/MWCNT foams. MWCNT content was fixed at 5 phr in this study. To achieve the objective, EVA was melt‐mixed with MWCNTs and organoclays in a bench kneader. And the obtained EVA/MWCNT/organoclay mixtures were mixed with chemical blowing agent and cross‐linking agent in a two roll‐mill. After being mixed in a two roll‐mill, the mixtures were put in a mold and the foams were obtained by compression‐molding. The effect of organoclay content on the mechanical properties and surface resistivity of EVA/MWCNT (5 phr)/organoclay foams was investigated. The addition of 1 phr organoclays to the EVA/MWCNT (5 phr) foams resulted in the improvement of tensile strength, 100% tensile modulus, tear strength, and compression set without increase of the density. However, further increase in content of organoclay (3 phr) leaded to a deterioration of mechanical properties. Therefore, determining the optimal content of organoclay was very important in order to achieve the main objective of this study. POLYM. COMPOS., 2013. © 2013 Society of Plastics Engineers

Effects of processing steps and organoclay content in butadiene rubber/organoclay nanocomposites

Even though polybutadiene rubber (BR) is a hydrophobic polymer, BR/organoclay nanocomposites are prepared successfully without a compatibilizer by using conventional compounding method. The main objective of this article is to investigate the effect of processing steps on the dispersion of organoclays in the BR matrix. The effect of each processing step on the dispersion of organoclays is studied by using X-ray diffraction (XRD). Also, the effect of the organoclay content on the mechanical properties is studied. According to the XRD results, mixing BR/organoclay compounds with vulcanization accelerator (MBTS) in a two-roll mill leads to the exfoliation of organoclays in this article. However, when BR/organoclay nanocomposites were heated at 155°C for the vulcanization as a next processing step, organoclays aggregated to become intercalated structure. The tensile and tear strength of BR/organoclay (9 phr) nanocomposite are 16.6 times and 3 times larger than those of BR, respectively. Over 100% and 300% modulus of BR, 300% and 350 % improvements are observed for those of BR/organoclay (9 phr) nanocomposite, respectively. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Effect of organoclay content and molecular weight on cellulose acetate nanocomposites properties

Nanocomposites based on cellulose acetate (CA), a commercial organoclay (Cloisite30B) and triethyl citrate (TEC) were obtained using a solution casting method. Different nanocomposites were prepared according to different organoclay contents (2.5, 5.0, 7.5 and 10.0 wt.%) and molecular weight of cellulose acetate (Mn 30,000 and 50,000). The properties of the nanocomposites were evaluated by means of opacity index, X-ray diffraction (XRD), differential scanning calorimetry (DSC), mechanical (modulus of elasticity, tensile strength and elongation at break), scanning electron microscopy (SEM) and oxygen transmission rate (OTR) measurements. All obtained nanocomposites showed the intercalation of polymer inside the clay structure which was slightly favored for nanocomposites with CA 30,000. Important changes on the opacity index, mechanical properties, glass transition and melting temperatures, crystalline fraction, oxygen permeability and fracture morphology of nanocomposite films were observed according to the increase of organoclay content. On the other hand, intercalation level and oxygen permeability showed some differences with the molecular weight of cellulose acetate.

Morphology, mechanical, and rheological behavior of microcellular injection molded EVA–clay nanocomposites

Ethylene vinyl acetate (EVA)/montmorillonite (MMT) nanocomposites diluted from master batch (50wt.%) with EVA and EVAgMA was used in this study. The organoclay EVA nanocomposites were then injection molded by conventional and microcellular methods. Nitrogen was used as the blowing agent. The effect of organoclay content and MA grafted EVA on the morphology and the mechanical and rheological properties of the EVA–clay nanocomposites were then investigated. The results showed that the mechanical properties (tensile and impact) increased as the clay content increased. Cell size decreased as the clay loading increased. The EVAgMA nanocomposites had better mechanical properties than the EVA nanocomposites. XRD results showed that the EVAgMA nanocomposites have an exfoliated layered structure while the EVA nanocomposites are intercalated. Rheological results showed the viscosity is clay loading dependent and that the shear thinning effect occurs at high shear rates.

Morphology, mechanical, thermal and rheological behavior of microcellular injection molded TPO-clay nanocomposites prepared by kneader

Thermoplastic olefin elastomers (TPO)/montmorillonite (MMT) nanocomposites prepared by kneader was used in this study. The organoclay TPO nanocomposites were then injection molded by conventional and microcellular methods. Nitrogen was used as the blowing agent. The effect of organoclay content on the mechanical/thermal/rheological properties of the TPO-clay nanocomposites was investigated. The results showed that the mechanical properties (tensile, impact, and wear resistance) increased as the clay content increased. Cell size decreased as the clay loading increased. The addition of MMT into TPO also improved the thermal stability of the TPO/clay nanocomposites. The XRD results showed that the nanocomposites having an intercalated layered structure. Rheological results showed the viscosity is clay loading dependent and shear thinning effect takes place at high shear rate.

Effect of organoclay on the mechanical/thermal properties of microcellular injection molded PBT–clay nanocomposites

An organically modified montmorillonite (MMT) was compounded with polybutylene terephthalate (PBT) in a twin-screw extruder. The organoclay PBT nanocomposites were then injection molded by conventional and microcellular methods. Nitrogen was used as the blowing agent. The effect of organoclay content, organoclay size (8 and 35 μm), and speed of the screw (80 and 100 rpm) on the mechanical and thermal properties were investigated. The results showed that when the MMT content was 1.0 wt.%, the nanocomposites have maximum tensile strength, wear resistance, and cell density. Moreover, the larger the particle size, the greater the tensile strength. The screw speed during compounding also affected the mechanical strength. The higher speed of the screw increased the tensile strength of the nanocomposites. The addition of MMT also helped the thermal stability of the PBT/clay nanocomposites. The WXRD results showed that when MMT loading is 1.0 wt.%, the nanocomposites have maximum d-spacing structure. TEM results showed that MMT is well dispersed on the nanocomposites at a MMT loading of 1.0 wt.%.

Mechanical properties of bioplastics and bioplastic–organoclay nanocomposites prepared from epoxidized soybean oil with different epoxide contents

AbstractThe objectives of this study were to investigate the effect of epoxide content (24–88 mol %) on the mechanical properties and characteristics of epoxidized soybean oil (ESO) and to compare the mechanical properties of ESO–organoclay nanocomposites with different epoxide contents (40 and 100 mol %). ESO was synthesized by in situ epoxidation with acetic acid and hydrogen peroxide. We prepared ESO bioplastic sheets from ESO by curing with methyltetrahydrophthalic anhydride and 1‐methylimidazole. The tensile properties and tear resistance of the synthesized bioplastic (ESO40, where the number indicates the molar percentage of epoxidation) were investigated and compared with ESO bioplastic sheets prepared from commercial ESO with 100 mol % epoxidation (ESO100). The tensile modulus, tensile strength, tensile toughness, and tear strength of the ESO bioplastics increased with increasing epoxide content, whereas the elongation at break of the ESO100 bioplastic was lowest. No trend was observed in the bioplastics prepared from ESO24–ESO88. Dynamic mechanical thermal analysis showed increases in the storage modulus and glass‐transition temperature as the epoxide content was increased. Thermal degradation also increased with increasing epoxide content. The crosslink density and chain flexibility controlled the mechanical properties and characteristics of the ESO bioplastics. ESO–organoclay nanocomposites were prepared by in situ intercalative polymerization. The addition of organoclay increased the mechanical properties of the ESO bioplastics. The effect of organoclay content (1–8 wt %) on the mechanical properties was similar to the effect of the epoxide content. The sESO100 nanocomposite showed a higher modulus but lower tensile strength and elongation at break than the ESO40 nanocomposite. Intercalation of the organoclay in the ESO nanocomposites was observed by transmission electron microscopy and X‐ray diffractometry. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Effect of organoclay on the mechanical / thermal properties of microcellular injection molded polystyrene–clay nanocomposites

An organically modified montmorillonite was compounded with polystyrene (PS) in a twin-screw extruder. The organoclay polystyrene nanocomposites were then injection molded by conventional and microcellular methods. Nitrogen was used as the blowing agent. The effect of organoclay content on the mechanical and thermal properties was investigated. The results showed that when the MMT content was 1 wt.%, the nanocomposites have maximum tensile strength, wear resistance, and cell density. Moreover, the addition of organoclay increases the glass transition and decomposition temperature of the nanocomposites. The XRD results showed that the layer spacing of the nanocomposites decreases by comparison with the organoclay. TEM pictures showed that MMT is well dispersed within the PS matrix.

Effect of organo clay content on proton conductivity and methanol transport through crosslinked PVA hybrid membrane for direct methanol fuel cell

In the present study, crosslinked poly(vinyl alcohol) (PVA) membranes were prepared using poly(styrene sulfonic acid- co-maleic acid) (PSSA_MA) (PVA:PSSA_MA = 1:7). The PSSA_MA was used both as a crosslinking agent and as a donor of the hydrophilic group (–SO 3H and/or –COOH). The hybrid membranes were prepared by modified clay such as Clay Na +, Clay 30B, and Clay 15A. The thermal, water uptake, proton and methanol transport properties of the hybrid membrane were found to be sensitive to the clay type and content. The hybrid membrane with Clay 30B shows higher proton conductivity than other hybrid membranes due to hydroxyethyl group. The membrane with Clay 15A showed the lowest methanol permeability due to lower specific gravity than other clay. Compared to the membrane without modified, the PVA/PSSA_MA/Clay 15A containing 4 wt% of Clay 15A showed both high proton conductivity (0.023 S/cm) and low methanol permeability (2.19 × 10 −7 cm 2/s).

Effect of organoclay content on the rheology, morphology, and physical properties of polyolefin elastomers and their blends with polypropylene

The effect of onium-ion exchanged montmorillonite clay (organoclay) on the rheology and physical properties of maleated ethylene–octene copolymer and ethylene–propylene rubber elastomers has been examined. The formation of a nanocomposite hybrid, containing substantial amounts of exfoliated clay, was accompanied by significant increases in the complex viscosity, elastic and loss moduli, and a narrowing of the region of linear viscoelasticity, attributed to both filler/polymer and filler/filler interactions. The properties of blends of these elastomers with polypropylene were dominated by the reinforced elastomeric matrix, into which the organoclay resided preferentially. The nanocomposite blends exhibited very fine morphologies, as well as a good balance of stiffness and ductility and enhanced thermal stability. POLYM. ENG. SCI., 46:1491–1501, 2006. © 2006 Society of Plastics Engineers