Showing papers in "Journal of Applied Polymer Science in 1998"
TL;DR: In this paper, polypropylene-clay hybrid (PPCH) was prepared using a maleic anhydride-modified PP oligomer (PP-MA) as a compatibilizer.
Abstract: Polypropylene-clay hybrids (PPCH) were prepared using a maleic anhydride-modified PP oligomer (PP-MA) as a compatibilizer. PP was melt-blended with organophilic clay which was intercalated with PP-MA. In these PPCHs, the particles of silicate layers were dispersed at the nanometer level. The particles became smaller and were dispersed more uniformly, as the ratio of PP-MA to the clay was increased. The dynamic storage moduli of the PPCHs were higher than that of PP up to 130°C. For example, the modulus of the PPCH with 5 wt % clay and 22 wt % PP-MA was 1.8 times higher compared to that of PP at 80°C. As the dispersibility of the clays was improved, the reinforcement effect of the clays increased. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67: 87–92, 1998
667 citations
TL;DR: In this paper, the mechanical properties and morphology of polypropylene/wood flour (PP/WF) composites with different impact modifiers and maleated polypropane (MAPP) as a compatibilizer have been studied.
Abstract: The mechanical properties and morphology of polypropylene/wood flour (PP/WF) composites with different impact modifiers and maleated polypropylene (MAPP) as a compatibilizer have been studied. Two different ethylene/propylene/diene terpolymers (EPDM) and one maleated styrene–ethylene/butylene–styrene triblock copolymer (SEBS–MA) have been used as impact modifiers in the PP/WF systems. All three elastomers increased the impact strength of the PP/WF composites but the addition of maleated EPDM and SEBS gave the greatest improvements in impact strength. Addition of MAPP did not affect the impact properties of the composites but had a positive effect on the composite unnotched impact strength when used together with elastomers. Tensile tests showed that MAPP had a negative effect on the elongation at break and a positive effect on tensile strength. The impact modifiers were found to decrease the stiffness of the composites. Scanning electron microscopy showed that maleated EPDM and SEBS had a stronger affinity for the wood surfaces than did the unmodified EPDM. The maleated elastomers are, therefore, expected to form a flexible interphase around the wood particles giving the composites better impact strength. MAPP further enhanced adhesion between WF and impact-modified PP systems. EPDM and EPDM–MA rubber domains were homogeneously dispersed in the PP matrix, the diameter of domains being between 0.1–1 μm. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:1503–1513, 1998
441 citations
TL;DR: In this paper, the fiber loadings were 30, 40, 50, and 60 wt %, and at each fiber loading, compatibilizer doses were 0, 1, 2, 3 and 4 wt percent.
Abstract: Jute fibers were chopped to approximately 100 mm in length and then processed through a granulator having an 8-mm screen. Final fiber lengths were up to 10 mm maximum. These fibers along with polypropylene granules and a compatibilizer were mixed in a K-mixer at a fixed rpm, 5500, and dumped at a fixed temperature, 390°F, following single-stage procedure. The fiber loadings were 30, 40, 50, and 60 wt %, and at each fiber loading, compatibilizer doses were 0, 1, 2, 3 and 4 wt %. The K-mix samples were pressed and granulated. Finally, ASTM test specimens were molded using a Cincinnati injection molding machine. At 60% by weight of fiber loading, the use of the compatibilizer improved the flexural strength as high as 100%, tensile strength to 120%, and impact strength (unnotched) by 175%. Remarkable improvements were attained even with 1% compatibilizer only. Interface studies were carried out by SEM to investigate the fiber surface morphology, fiber pull-out, and fiber–polymer interface. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 329–338, 1998
325 citations
TL;DR: In this article, a new type of bamboo fiber-reinforced polypropylene (PP) composite was prepared and its mechanical properties were tested, and it was found that with 24 wt % of such MAPP being used in the composite formulation, the mechanical properties of the composite such as the tensile modulus, the Tensile strength, and the impact strength all increased significantly.
Abstract: A new type of bamboo fiber-reinforced polypropylene (PP) composite was prepared and its mechanical properties were tested. To enhance the adhesion between the bamboo fiber and the polypropylene matrix, maleic anhydride-grafted polypropylene (MAPP) was prepared and used as a compatibilizer for the composite. The maleic anhydride content of the MAPP was 0.5 wt %. It was found that with 24 wt % of such MAPP being used in the composite formulation, the mechanical properties of the composite such as the tensile modulus, the tensile strength, and the impact strength all increased significantly. The new composite has a tensile strength of 32–36 MPa and a tensile modulus of 5–6 GPa. Compared to the commercially available wood pulp board, the new material is lighter, water-resistant, cheaper, and more importantly has a tensile strength that is more than three times higher than that of the commercial product. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 1891–1899, 1998
301 citations
TL;DR: In this paper, shape-memory polyurethanes (PUs) were synthesized by 4,4′-diphenylmethane diisocyanate (MDI), 1,4-butanediol (BD), and poly(tetramethyl oxide)glycol (PTMO).
Abstract: Shape-memory polyurethanes (PUs) were synthesized by 4,4′-diphenylmethane diisocyanate (MDI), 1,4-butanediol (BD), and poly(tetramethyl oxide)glycol (PTMO). The morphology of PUs was studied using DSC, DMA, and TEM. The results indicated that the PUs would show different morphology by changing the mol ratio of MDI and BD (hard segment). The specimens would show the shape-memory behavior that was fixing and recovering the deformation at different operating temperature ranges. These results demonstrated that the shape-memory behavior of the PUs would be affected by the morphology and the modulus ratio that was defined as in DMA analysis. The amount of the hard-segment-rich phase would affect the ratio of recovery, that is, the low content would lead to the recovery of the deformed specimen being incomplete. The recovering rate would be influenced by the modulus ratio and the size of the dispersed phase in the micromorphology. On the other hand, the shape-memory behavior of PUs could be enhanced by the training process. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 1563–1574, 1998
296 citations
TL;DR: In this article, a solution-casting method was used for the analysis of poly(L-lactide) and poly(E-caprolactone) blend films for 20 months in a phosphate-buffered solution of pH 7.4 at 37°C.
Abstract: Blend films were prepared from poly(L-lactide) (PLLA) and poly(E-caprolactone) (PCL) with different PLLA contents [XPLLA (w/w) = PLLA/(PCL + PLLA)] by the solution-casting method and their hydrolysis behaviors were investigated up to 20 months in a phosphate-buffered solution of pH 7.4 at 37°C by gel permeation chromatography, tensile testing, differential scanning calorimetry, and gravimetry. Polarizing microscopic observation and dynamic mechanical analysis revealed that PCL and PLLA were phase-separated in blend films before hydrolysis. The mass remaining, molecular weight, and tensile strength of the blend films with XPLLA of 0.5 and 0.75 decreased more rapidly by hydrolysis than those of the nonblended PLLA, while the elongation at break of the blend film of XPLLA = 0.25 decreased the slowest. The rate constant for hydrolysis (k) calculated from the Mn change during hydrolysis was higher for blend films of XPLLA = 0.5 and 0.75 than those expected from k of nonblended PLLA and PCL. The melting temperature (Tm) of PLLA in the blend and nonblended films of XPLLA = 0.5, 0.75, and 1 decreased from 179 to 161, 160, and 175°C upon hydrolysis for 20 months, respectively, while that for XPLLA = 0.25 slightly increased from 176 to 177°C. On the other hand, Tm and the crystallinity of PCL was significantly increased by hydrolysis for 20 months, irrespective of XPLLA. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67: 405–415, 1998
289 citations
TL;DR: In this paper, the variability of tensile properties exhibited by cocoon silk from Bombyx mori silkworms was investigated using scanning electron microscopy, where the interspecimen variability of diameter was quantified and found to be inadequately represented by standard deviation.
Abstract: While silk exhibits high values of tensile strength and stiffness, these properties are compromised by their poor reproducibility. We present the results of experiments aimed at characterizing the variability of tensile properties exhibited by cocoon silk from Bombyx mori silkworms. Scanning electron microscopy is used to measure an average diameter for individual test specimens; the interspecimen variability of diameter is quantified and found to be inadequately represented by standard deviation. When load-extension data are converted into stress-strain curves, a marked improvement in reproducibility is realized if each specimen cross-section is calculated from diameter measurements specific to that specimen. Nevertheless, a significant variability in fracture stress remains; a Weibull analysis reveals that silkworm silk has a failure predictability comparable with that of glass and nonengineering ceramics. Unloading/reloading tests demonstrate that stiffness is not significantly affected by cumulative deformation, and the stress–strain relationship is not sensitive to strain rate. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 2439–2447, 1998
241 citations
TL;DR: In this paper, the shape-memory behavior of polyurethanes was investigated using thermal and dynamic mechanical properties using DSC and DMA; then, the morphology of the PUs was directly observed by TEM.
Abstract: Polyurethanes (PUs) of a suitable molar ratio of monomers were found to have shape-memory behavior. In this study, four series of PUs were synthesized by 4,4′-diphenylmethane diisocyanate (MDI), 1,4-butanediol (BD), and various molecular weights of poly(tetramethylene oxide)glycol (PTMO) to study the influence of the soft segment (PTMO) on the shape-memory behavior of PUs. The investigation on thermal and dynamic mechanical properties was performed using DSC and DMA; then, the morphology of the PUs was directly observed by TEM. At the range of the individual glass transition, a similar recovering behavior was found from the deformed specimen that contained the same composition but different molecular weights of PTMO. However, the phase separation between the soft and the hard segments of the PUs would influence their shape-memory behavior. On the other hand, a large number of the dispersed phase of the PUs would delay the recovery rate of the deformed specimens using a high molecular weight PTMO. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 1575–1586, 1998
239 citations
TL;DR: A polyamide 6 (PA 6)/silica nanocomposite was obtained through a novel method, in situ polymerization, by first suspending silica particles in ϵ-caproamide under stirring and then polymerizing this mixture at high temperature under a nitrogen atmosphere as discussed by the authors.
Abstract: A polyamide 6 (PA 6)/silica nanocomposite was obtained through a novel method, in situ polymerization, by first suspending silica particles in ϵ-caproamide under stirring and then polymerizing this mixture at high temperature under a nitrogen atmosphere The silicas were premodified with aminobutyric acid prior to the polymerization The effects of the addition of unmodified and modified silicas on the dispersion, interfacial adhesion, isothermal crystallization, and mechanical properties of PA 6 nanocomposites were investigated by using scanning electron microscopy, dynamic mechanical analysis, differential scanning calorimetry, and mechanical tests, respectively The results show that the silicas dispersed homogeneously in the PA 6 matrix The addition of silicas increases the glass transition temperature and crystallization rate of PA 6 The mechanical properties such as impact strength, tensile strength, and elongation at break of the PA 6/modified silica nanocomposites showed a tendency to increase and decrease with increase of the silica content and have maximum values at 5% silica content, whereas those of the PA 6/unmodified silica system decreased gradually © 1998 John Wiley & Sons, Inc J Appl Polym Sci 69: 355–361, 1998
233 citations
TL;DR: In this article, low-density polyethylene (LDPE) and plasticized starch (PLST) blends, containing different percentages of PLST, were prepared and the morphology of the blends was studied using scanning electron microscopy (SEM).
Abstract: In the present study, low-density polyethylene (LDPE) and plasticized starch (PLST) blends, containing different percentages of PLST, were prepared. In these blends, two different polyethylene/maleic anhydride graft (PE-g-MA) copolymers containing 0.4 and 0.8 mol % anhydride groups, respectively, were added as compati- bilizers at 10 wt % PLST. The compatibilization reaction was followed by FTIR spec- troscopy. The morphology of the blends was studied using scanning electron microscopy (SEM). It was found that as the amount of anhydride groups in the copolymers increases a finer dispersion of PLST in the LDPE matrix is achieved. This is reflected in the mechanical properties of the blends and especially in the tensile strength. The blends compatibilized with the PE-g-MA copolymer containing 0.8 mol % anhydride groups have a higher tensile strength, which in all blends, even in those containing 20 and 30 wt % PLST, is similar to that of pure LDPE. The biodegradation of the blends followed the exposure to activated sludge. It was found that the compatibilized blends have only a slightly lower biodegradation rate compared to the uncompatibilized blends. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 1503-1521, 1998
204 citations
TL;DR: In this paper, the isothermal and nonisothermal crystallization kinetics of Nylon-11 were analyzed using differential scanning calorimetry, where the Avrami equation and Jeziorny equation were combined to describe the primary stage of the crystallization process.
Abstract: Analysis of the isothermal, and nonisothermal crystallization kinetics of Nylon-11 is carried out using differential scanning calorimetry. The Avrami equation and that modified by Jeziorny can describe the primary stage of isothermal and nonisothermal crystallization of Nylon-11. In the isothermal crystallization process, the mechanism of spherulitic nucleation and growth are discussed; the lateral and folding surface free energies determined from the Lauritzen-Hoffman equation are sigma = 10.68 erg/cm(2) and sigma(e) = 110.62 erg/cm(2); and the work of chain folding q = 7.61 Kcal/mol. In the nonisothermal crystallization process, Ozawa analysis failed to describe the crystallization behavior of Nylon-ii. Combining the Avrami and Ozawa equations, we obtain a new and convenient method to analyze the nonisothermal crystallization kinetics of Nylon-11; in the meantime, the activation energies are determined to be -394.56 and 328.37 KJ/mol in isothermal and nonisothermal crystallization process from the Arrhonius form and the Kissinger method. (C) 1998 John Wiley & Sons, Inc.
TL;DR: In this article, silicone rubber/organomontmorillonite hybrid nanocomposites were prepared via a melt-intercalation process, which was characterized by X-ray diffraction, transmission electron microscopy (TEM), and thermogravimetric analysis.
Abstract: In this article, silicone rubber/organomontmorillonite hybrid nanocomposites were prepared via a melt-intercalation process. The resulting hybrid nanocomposites were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and thermogravimetric analysis (TGA). The results proved that the organomontmorillonite could be exfoliated into ca. 50-nm thickness and uniformly dispersed in the silicone rubber matrix during the melt-intercalation process. Furthermore, the mechanical properties and thermal stability of the hybrids were very close to those of aerosilica-filled silicone rubber. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 1557–1561, 1998
TL;DR: In this paper, the crosslinking reaction between the hydroxyl groups of SA and the aldehyde groups of GA was characterized through infrared radation, X-ray diffractometry, and the swelling measurement, and it was observed that the crosslink could reduce both the solubility of water in the resulting membrane and the permselectivity of the membrane toward water at the expense of membrane stability against water.
Abstract: Dense sodium alginate (SA) membranes crosslinked with glutaraldehyde (GA) have been prepared by the solution method, wherein a nonsolvent of SA (acetone) was used in a reaction solution instead of an aqueous salt solution. Through infrared radation, X-ray diffractometry, and the swelling measurement, the crosslinking reaction between the hydroxyl groups of SA and the aldehyde groups of GA was characterized. To investigate the selective sorption behavior of the crosslinked SA membranes, swelling measurements of the membranes in ethanol-water mixtures of 70–90 wt % ethanol contents were conducted by equipment that was able to measure precisely the concentration and amount of the liquid absorbed in the membranes. It was observed that the crosslinking could reduce both the solubility of water in the resulting membrane and the permselectivity of the membrane toward water at the expense of membrane stability against water. The pervaporation separation of a ethanol-water mixture was conducted with the membranes prepared at different GA contents in the reaction solution. When the membrane was prepared at a higher GA content, both flux and separation factor to water were found to be reduced, thus resulting from the more crosslinking structure in it. The pervaporation separations of ethanol-water mixtures were also performed at different feed compositions and temperatures ranging from 40 to 80°C. A decline in the pervaporative performance was observed due to the relaxation of polymeric chains taking place during pervaporation, depending on operating temperature and feed composition. The relaxational phenomena were also elucidated through an analysis on experimental data of the membrane performance measured by repeating the operation in the given temperature range. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67: 209–219, 1998
TL;DR: In this paper, a benzoxazine was used as a hardener of the epoxy resin and the properties of the cured epoxy resin resins were investigated, which showed good heat resistance, water resistance, electrical insulation, and mechanical properties compared with the bisphenol A type novolac.
Abstract: Bisphenol A based benzoxazine was prepared from bisphenol A, formaline, and aniline. This benzoxazine was used as a hardener of the epoxy resin. Curing behavior of the epoxy resin and the properties of the cured resin were investigated. Consequently, curing reaction proceeded without a curing accelerator. The molding compound showed good thermal stability under 150°C, which corresponded to the temperature in the cylinder of injection molding. Above 150°C, the curing reaction proceeded rapidly. The cured epoxy resin showed good heat resistance, water resistance, electrical insulation, and mechanical properties compared with the epoxy resin cured by the bisphenol A type novolac. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1903–1910, 1998
TL;DR: In this article, a broad endotherm for Nafion®-H+ at Tα ≈ 215°C was found, which was rationalized in terms of an increasing fraction of flexible D units that disrupt hydrophilic Q structures.
Abstract: Nafion®/SiO2, Nafion®/[ORganically MOdified SILicate (ORMOSIL)] and Nafion®/dimethylsiloxane hybrids were created via in situ sol–gel reactions for tetraethoxysilane, diethoxydimethylsilane, and their mixtures. Differential scanning calorimetry studies showed a broad endotherm for unfilled Nafion®-H+ at Tα ≈ 215°C that shifts upward for the Q : D = 1 : 0 (mol : mol) [Q = Si(O1/2)4, D = (O1/2)2Si(CH3)2] hybrid, then shifts downward with decreasing Q : D. This endotherm likely arises from release of H2O molecules bound to ≡Si—OH groups and condensation reactions among silanol groups. The decrease in Tα is rationalized in terms of an increasing fraction of flexible D units that disrupt hydrophilic Q structures. Tm shifts to lower temperatures with decreasing Q : D, and it is suggested that main chains are restricted by side chains embedded in silicon oxide nanoparticles, but D unit insertion causes side chains to be anchored less strongly. Thermal gravimetric analysis indicates that the first mass loss step for Nafion®-H+ shifts to higher temperatures as D : Q increases; an increase in D unit fraction inhibits Q unit degradation by evolved HF. A dynamic mechanical transition at Tα may arise from side chain motions, and the increase in Tα in passing from unfilled Nafio®-H+ to the 1 : 0 hybrid is due to side chain immobilization by their entrapment in silicon oxide domains. The progression 0 : 1 1 : 2 1 : 1 2 : 1 generates increasing mechanical tensile strength and decreasing ductility; strength enhancement might be due to entanglements between ORMOSIL and pure silicon oxide phases and side chains. Liquid sorption experiments quantified the affinity of these hybrids for solvents of varying polarity. A dielectric relaxation for the 0 : 1 hybrid at about 1.5 kHz might be related to side chain mobility. A weaker relaxation in the range 104–105 Hz exists for the 0 : 1 and 1 : 1 hybrids and Nafion®-H+, but not for the 1 : 0 hybrid that exhibits the behavior e′ ∼ f−n over a broad frequency (f) range, suggestive of intercluster proton hopping. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68:747–763, 1998
TL;DR: In this article, the nonisothermal melt crystallization kinetics of PEDEKmK linked by meta-phenyl and biphenyl was investigated by differential scanning calorimetry (DSC).
Abstract: Nonisothermal melt crystallization kinetics of PEDEKmK linked by meta-phenyl and biphenyl was investigated by differential scanning calorimetry (DSC). A convenient and reasonable kinetic approach was used to describe the nonisothermal melt crystallization behavior, and its applicability was verified when the modified Avrami analysis by the Jeziorny and Ozawa equation were applied to the crystallization process. The crystallization activation energy was estimated to be -219 kJ/mol by Kissinger method while crystallizing from the PEDEKmK melt nonisothermally. These observed crystallization characteristics were compared to those of the other members of poly(aryl ether ketone) family. (C) 1998 John Wiley & Sons, Inc.
TL;DR: In this paper, the authors demonstrate the direct intercalation of an epoxy polymer in the interlayer of Na+montmorillonite (MMT) by a step type of polymerization in an aqueous emulsion media.
Abstract: This article demonstrates the direct intercalation of an epoxy polymer in the interlayer of Na+–montmorillonite (MMT) by a step type of polymerization in an aqueous emulsion media. The synthesis and the results of structural and thermal characterizations for this hybrid composite are described. Equimolar quantities of bisphenol A and an epoxy prepolymer (n = 0.2) in an emulsion media were polymerized in the presence of Na+–MMT. X-ray diffraction (XRD) data obtained from the acetone-extracted products show that the basal spacing of the MMT is expanded from 0.96 to 1.64 nm. Thermal characterization for the postcured products by TGA and DSC gave evidence of enhanced thermal stabilities. SEM examination of the uncured products revealed that a disordered phase begins to appear with increasing polymer loading. However, the XRD profile supported that an overwhelming fraction of the nanocomposite contains intercalated clay. Also, the possibility of intercalation by the emulsion technique is proposed on the basis of the swelling characteristics of MMT in aqueous media and the sizes of micelles containing a monomer. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1997–2005, 1998
TL;DR: In this article, the authors used dynamic thermogravimetry in nitrogen and air to estimate the thermostability of cellulose and its esters, taking into account the values of initial thermal degradation temperature Td, the temperature at the maximum degradation rate Tdm, and char yield at 400°C.
Abstract: Cellulose, cellulose diacetate (CDA), cellulose triacetate (CTA), cellulose nitrate (CN), and cellulose phosphate (CP) were subjected to dynamic thermogravimetry in nitrogen and air. The thermostability of the cellulose and its esters was estimated, taking into account the values of initial thermal degradation temperature Td, the temperature at the maximum degradation rate Tdm, and char yield at 400°C. The results show that these polymers may be arranged in the following order of increasing thermostability: CN < CP < regenerated cellulose < filter cotton < CDA < CTA. The activation energy (E), order (n), and frequency factor (Z) of their degradation reactions were obtained following the Friedman, Chang, Coats–Redfern, Freeman–Carroll, and Kissinger methods. The dependence of Td, Tdm, E, n, Ln Z, and char yield at 400°C on molecular weight and test atmosphere is also discussed. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68:293–304, 1998
TL;DR: In this paper, several crosslinked polymers with various degrees of β-cyclodextrin (β-CD) were used for the recovery of various organic pollutants from aqueous solutions.
Abstract: Insoluble β-cyclodextrin (β-CD) polymers have been used for the recovery of various organic pollutants from aqueous solutions. These resins have been prepared by polymerization using epichlorohydrin (Epi) as a crosslinking agent. Several crosslinked polymers with various degrees of β-CD were used. Several studies (time, concentration, kinetics, and pH) are presented here. The results show that these sorbents exhibit high sorption capacities toward substituted benzene derivatives. The mechanism of sorption is both physical adsorption in the polymer network and/or the formation of an inclusion complex and/or the formation of hydrophobic guest–guest interactions. © 1998 John Wiley & Sons, Inc. J Appl Polm Sci 68: 1973–1978, 1998
TL;DR: In this article, a simplified method for the synthesis of thermosensitive porous hydrogels by a radical polymerization was presented and their swelling properties were examined experimentally, and it was found that these gels consisted of aggregated microgel particles, namely, a porous structure.
Abstract: The simplified method for the synthesis of thermosensitive porous hydrogels by a radical polymerization was presented and their swelling properties were examined experimentally. N,N-Diethylacrylamide (DEAAm) or N-isopropylacrylamide (NIPAm) as primary monomers and N,N′-methylenebisacrylamide (BIS) as a crosslinker were used. They were polymerized in water at various temperatures above the lower critical solution temperature (LCST) of poly-DEAAm (ca. 32°C) or poly-NIPAm (ca. 31°C) by using N,N,N′,N′-,tetramethylethylenediamine (TEMED) and ammonium peroxsodisulfate (APS) as the polymerization accelerator and initiator, respectively. From the observation by a scanning electron microscope, it was found that these gels consisted of aggregated microgel particles, namely, a porous structure. The gels swelled below their LCSTs, and the swelling degree increased with lowering temperature. Furthermore, the gels swelled or shrank very fast in response to the change in temperature, and the shrinking rate was larger than the swelling rate. Such swelling properties and mechanical properties depended on the porous structure of the gels such as the size of the microgels and the pore volume, which largely changed with the synthesis temperature and the component of the primary monomer. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 895–906, 1998
TL;DR: In this article, the effects of the solid content, particle size, type of solid particle material, and temperature on slip velocity and slip layer thickness were investigated using a parallel disk rheometer with emphasis on wall slip phenomenon.
Abstract: The rheological characterization of highly filled suspensions consisting of a Newtonian matrix (hydroxyl-terminated polybutadiene), mixed with two different sizes of aluminum powder (30% and above by volume) and two different sizes of glass beads (50% and above by volume), was performed using a parallel disk rheometer with emphasis on the wall slip phenomenon. The effects of the solid content, particle size, type of solid particle material, and temperature on slip velocity and slip layer thickness were investigated. Suspensions of small particles of aluminum (mean diameter of 5.03 μm) did not show slip at any concentration up to the maximum packing fraction. However, suspensions of the other particles exhibited slip at the wall, at concentrations close to their maximum packing fraction. In these suspensions, the slip velocity increased linearly with the shear stress, and at constant shear stress, the slip velocity increased with increasing temperature. The slip layer thickness increased proportionally with increasing size of the particles for the glass beads. Up to a certain value of (filler content/maximum packing fraction), ϕ/ϕm, the slip layer thickness divided by the particle diameter, δ/DP, was 0, but it suddenly increased and reached a value that was independent of ϕ/ϕm and the temperature. On average, the ratio of δ/DP was 0.071 for aluminum and 0.037 for glass beads. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 515–522, 1998
TL;DR: In this article, the surface morphology of Nafion 117 membrane was studied by tapping mode atomic force microscopy and three different samples were analyzed and correspond respectively to dry membrane and wet membrane equilibrated either with water or with tributylphosphate.
Abstract: Surface morphology of Nafion 117 membrane was studied by tapping mode atomic force microscopy. Three different samples were analyzed and correspond respectively to dry membrane and wet membrane equilibrated either with water or with tributylphosphate. These studies show the supermolecular structure of the membrane, which is made of nodules or spherical grains of a mean diameter of 11 nm, and are surrounded by interstitial regions of a mean thickness of 50 A. Roughness analysis of the samples shows the influence of the swelling properties of the membrane on its surface morphology. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 503–508, 1998
TL;DR: In this article, a crosslinked polyvinyl alcohol (PVA) with sulfur-succinic acid (SSA) by heat treatment and investigated the effect of the crosslinking density on the separation of water-alcohol mixtures by pervaporation technique.
Abstract: For the purposes of the water-selective membrane material development for pervaporation separation, we crosslinked poly(vinyl alcohol) (PVA) with sulfur-succinic acid (SSA), which contains —SO3OH, by heat treatment and investigated the effect of the crosslinking density on the separation of water–alcohol mixtures by pervaporation technique. The crosslinking reaction between PVA and SSA was characterized through Fourier transform infrared spectroscopy and differential scanning calorimetry tests by varying the amount of the crosslinking agent, the reaction temperature, and the swelling measurements of each pure component. The separation performance of the water–methanol mixture is not good due to the existence of sulfonic acid, hydrophilic group, in the crosslinking agent. However, for the water–ethanol mixture, the flux of 0.291 kg/m2h and the separation factor of 171 were obtained at 70°C when PVA-crosslinked membrane containing 7 wt % SSA was used. The same membrane also showed flux of 0.206 kg/m2h and a separation factor of 1969 at the same operating temperature. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1717–1723, 1998
TL;DR: In this paper, the influence of the moisture content and the woodflour chemical modification on the physical and mechanical properties of different composites was investigated, and the results indicated that mechanical properties (compression and bending tests) were severely affected by moisture and chemical modifications.
Abstract: Woodflour of Eucaliptus saligna with two different chemical treatments (mercerization and esterification with maleic anhydride) was used as filler of an unsaturated polyester matrix. Woodflour was treated to increase the interfacial adhesion with the matrix, to improve the dispersion of the particles, and to decrease the water sorption properties of the final composite. The objective of this study was to determine the influence of the moisture content and the woodflour chemical modification on the physical and mechanical properties of the different composites. Results indicated that mechanical properties (compression and bending tests) were severely affected by moisture and chemical modifications. In wet conditions, the composites made from treated woodflour had the lowest flexural modulus and ultimate stress. It was found that this was a reversible effect, because the original values of the compression properties were recovered after drying. Temperature scans in dynamic mechanical tests showed that an irreversible change occurred during exposure to humid environments, probably due to the hydrolysis of the polyester matrix. Essentially, the same behavior was observed for matrix and composites; however, a wood-related transition overlapped the main transition in the case of wet composites. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 2069–2076, 1998
TL;DR: In this paper, phase-separated blend films were prepared with the solution casting method from poly(L-lactide) (PLLA) and poly(e-caprolactone)(PCL) with different PLLA contents and their biodegradation was investigated in soil up to 20 months.
Abstract: Phase-separated blend films were prepared with the solution casting method from poly(L-lactide) (PLLA) and poly(e-caprolactone) (PCL) with different PLLA contents [XPLLA (w/w) = PLLA/(PCL + PLLA)] and their biodegradation was investigated in soil up to 20 months by gravimetry, gel permeation chromatography, tensile testing, differential scanning calorimetry, and scanning electron microscopy. The nonblended PCL film and the blend film with XPLLA = 0.25 disappeared in 4 and 12 months, respectively, while most of the initial mass remained for the blend film of XPLLA = 0.75 and the nonblended PLLA film. The decrease in weight remaining, molecular weight, tensile strength, and elongation-at-break was higher for blend films of low XPLLA. The melting temperature of PLLA in blend films of XPLLA = 0.5 and 0.75, and of nonblended film, remained around 179°C upon biodegradation in soil for 20 months. The preferred biodegradation of PCL in blend films resulted in formation of microspheres of a PLLA-rich phase at the surface for the blend film of XPLLA = 0.25 and the porous structure for blend films of XPLLA = 0.5 and 0.75. Comparison of the weight loss of blend films in biodegradation in soil with that of the nonenzymatic hydrolysis in phosphate-buffered solution revealed preferred enzymatic degradation of PCL and insignificant attack to PLLA in the blends. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 2259–2268, 1998
TL;DR: In this paper, xylan with glucuronic acid functionalities, separated from birchwood, was converted into hydrogels by dissolving it together with chitosan in acidic conditions.
Abstract: Xylan with glucuronic acid functionalities, separated from birchwood, was converted into hydrogels by dissolving it together with chitosan in acidic conditions. The hydrogels were formed at certain xylan/chitosan compositions. The mechanism of the gel formation was investigated with FTIR. Complexation between glucuronic acid functionalities of xylan and amino groups of chitosan is suggested to be responsible for network formation. The swelling behavior of these hydrogels was studied at various pH levels and salt concentrations, and the hydrogels responded in a reversible manner to various stimuli. DMA of the films showed separated transitions that may correspond to different phases. Imaging with AFM in TappingMode™ of the surfaces indicated discrete xylan and chitosan phases. A sponge-like microporous structure, as shown with SEM, was formed when a hydrogel was freeze dried. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 1661–1667, 1998
TL;DR: In this paper, a new development in polyurethane foam technology was described, whereby a renewable source of polyol derived from refined-bleached-deodorized (RBD) palm oil was used to produce polyurethsane foams.
Abstract: The reactions between polymeric diphenyl methane diisocyanate (polymeric MDI) and conventional polyols to produce foamed polyurethane products are well documented and published. Current polyurethane foams are predominantly produced from these reactions whereby the polyol components are usually obtained from petrochemical processes. This article describes a new development in polyurethane foam technology whereby a renewable source of polyol derived from refined–bleached–deodorized (RBD) palm oil is used to produce polyurethane foams. Using very basic foam formulation, rigid polyurethane foams were produced with carbon dioxide as the blowing agent generated from the reaction between excess polymeric MDI with water. The foams produced from this derivatized RBD palm oil have densities in excess of 200 kg/m3 and with compression strengths greater than 1 MPa. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 509–515, 1998
TL;DR: In this paper, the fracture toughness, flexural modulus, and flexural strength of rubber-modified polybenzoxazine were measured to investigate the effect of rubber modification.
Abstract: Polybenzoxazine as a noble phenolic resin was modified with amine-terminated butadiene acrylronitrile rubber (ATBN) and with carboxyl-terminated butadiene acrylronitrile rubber (CTBN) in order to improve its mechanical properties. The fracture toughness, flexural modulus, and flexural strength of rubber-modified polybenzoxazine were measured to investigate the effect of rubber modification. In fracture toughness, ATBN is more effective than CTBN. ATBN-modified polybenzoxazine showed better distribution of rubber particles in matrix phase than did CTBN-modified polybenzoxazine. The cure rates in these systems were monitored by differential scanning calorimetry to investigate the effect of cure rate on rubber size. The change of glass transition temperatures of rubber-modified polybenzoxazine was measured with a dynamic mechanical thermal analyzer to explain the variation of mechanical properties. In addition, the relationship between mechanical properties and the morphology of rubber-modified polybenzoxazines was also undertaken. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67: 1–10, 1998
TL;DR: In this article, the ability of poly(N-vinylimidazole) hydrogels to bind Cu, Co, Ni, Zn, Cd, Pb, Na, Hg, Na(I) and Ca(II) cations, as well as uranyl, vanadium, rhenium, and molybdenum complexes, was studied by a batch equilibrium procedure using atomic absorption spectroscopy and UV-Vis spectrophotometry.
Abstract: The ability of poly(N-vinylimidazole) hydrogels to bind Cu(II), Co(II), Ni(II), Zn(II), Cd(II), Pb(II), Hg(II), Na(I) and Ca(II) cations, as well as uranyl, vanadium, rhenium, and molybdenum complexes, was studied by a batch equilibrium procedure using atomic absorption spectroscopy and UV-Vis spectrophotometry. The optimum pH for ion adsorption was determined in any case. The influence of the crosslinking degree of the hydrogel on the sorption kinetics and the sorption capacity at equilibrium were also studied. Sorption from the binary mixture Cu(II) + U(VI) was also analyzed at the optimum pH. Elution of the ions adsorbed from single and binary solutions was achieved in all cases. A selective desorption of loaded hydrogels with two types of ions was attained. The general conclusion is that poly(N-vinylimidazole) hydrogels are excellent materials for retention of all the ions studied here [except for Pb(II), Na(I), and Ca(II)]. The elution, which can be selective, allows regeneration of the hydrogel. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:1109–1118, 1998
TL;DR: By blending a rigid polymer, sodium alginate (SA), and a flexible polymer, polyvinyl alcohol (PVA), SA/PVA blend membranes were prepared for the pervaporation separation of ethanol-water mixtures.
Abstract: By blending a rigid polymer, sodium alginate (SA), and a flexible polymer, poly(vinyl alcohol) (PVA), SA/PVA blend membranes were prepared for the pervaporation separation of ethanol–water mixtures. The rigid SA membrane showed a serious decline in flux and a increase in separation factor due to the relaxation of polymeric chains, whereas the flexible PVA membrane kept consistent membrane performance during pervaporation. Compared with the nascent SA membrane, all of the blend membranes prepared could have an enhanced membrane mobility by which the relaxation during pervaporation operation could be reduced. From the pervaporation separation of the ethanol–water mixtures along with the temperature range of 50–80°C, the effects of operating temperature and PVA content in membrane were investigated on membrane performance, as well as the extent of the relaxation. The morphology of the blend membrane was observed with PVA content by a scanning electron microscopy. The relaxational phenomena during pervaporation were also elucidated through an analysis on experimental data of membrane performance measured by repeating the operation in the given temperature range. SA/PVA blend membrane with 10 wt % of PVA content was crosslinked with glutaraldehyde to enhance membrane stability in water, and the result of pervaporation separation of an ethanol–water mixture through the membrane was discussed. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:949–959, 1998