bluuebunny/crossref_metadata_2025 huggingface dataset:
The effect of modification on structure and dynamic mechanical behavior during the processing of acrylic fiber to stabilized fiber
Authors: Ko Tse‐Hao , Chiranairadul Phaichit , Ting Hsing‐Yie , Lin Chung‐Hua
Published: April 2003

Polyacrylonitrile (PAN) fibers pretreated with potassium permanganate have reduced the time required for stabilization, and also improved mechanical properties of the resultant carbon fibers. In this study, the effect of modification on the stabilization process and the dynamic mechanical properties of PAN fibers have been examined. The beta peak appeared at about 125°C on the loss tangent curves caused by molecular motion in the PAN fiber. Appearing at about 254°C, the alpha peak is attributed to chemical reactions and molecular motion in the formation of the crystalline phase of stabilized fibers. The alpha peak of the modified PAN fiber had lower absorption and had a smaller peak in the temperature range of 212–239°C. This indicated that potassium permanganate acts as a catalyst to lower the reaction temperature by about 20°C of the initial cyclization reaction. The dynamic storage modulus analysis indicated that modified PAN fibers have a lower initial transition temperature and that formation of the ladder polymer is gradual and steady.
Studies on composites from wood and polypropylenes. II
Authors: Takase Setsuko , Shiraishi Nobuo
Published: April 2003

Composites of polypropylene (PP) or maleic‐anhydride‐modified polypropylene (MPP) with refiner ground pulp (RGP) were prepared under various kneading conditions (mixing temperature, rate of rotation, and mixing time) and evaluated for their tensile strength (σmax), break elongation (ϵmax), and Young's modulus (E). Particularly, for the rate of rotation, fiber length distribution and its fibrillation were investigated in connection with mechanical properties of the composites. Also evaluated in this study was the effect of modifiers of PP on the properties. Modified PP that can be grafted or can have affinity to RGP was proved to improve the tensile strength of the molded composites as the RGP content increases, while the strength was decreased for PP–RGP composite without a modifier. MPP was also evaluated as a compatibilizer for the PP–RGP composites, and a tremendous improvement of tensile strength was achieved with MPP addition of only 2.5%, indicating that MPP can act as a compatibilizer in its system. These lines of evidence is interpreted to be caused from the improvement of the adhesion between RGP and PP through localizing MPP at the interface of these two components.
Use of wood fibers in thermoplastics. VII. The effect of coupling agents in polyethylene–wood fiber composites
Authors: Raj R. G. , Kokta B. V. , Maldas D. , Daneault C.
Published: April 2003

Linear low density polyethylene (LLDPE) was reinforced with different wood fibers, aspen chemithermomechanical pulp (bleached and unbleached), and other commerical wood pulps. Silane coupling agents A‐172, A‐174, A‐1100, and polymethylene polyphenyl isocyanate were used to improve the bonding between the fiber and matrix. LLDPE filled with pretreated wood fiber produced a significant improvement in tensile strength and modulus. Comparison of tensile and impact properties of wood fiber composites with mica and glass fiber composites shows the potential advantage (in terms of material cost and specific properties) of wood fiber as a reinforcement.
The boron trifluoride monoethyl amine complex cured epoxy resins
Authors: Chen C. S. , Pearce Eli M.
Published: April 2003

The curing exotherm pattern is affected by the equivalent ratio of curing agent, boron trifluoride monoethylamine complex (BF3 · MEA), to epoxy resin. The diglycidyl ether of 9,9‐bis(4‐hydroxyphenyl) fluorene (DGEBF) cures more slowly than the diglycidyl ether of bisphenol A (Epon 828). The glass transition temperatures (Tg's) of BF3 · MEA cured Epon 828 are increased with inceasing concentration of curing agent (0.0450–0.1350 eq.) cured DGEBF. The activation energies for the thermal decomposition for BF3 · MEA (0.0450–0.1350 eq.) cured DGEBF. The activation energies for the thermal decomposition for BF3 · MEA (0.0450 eq./epoxy eq.) cured Epon 828 and DGEBF are almost equivalent 43 and 44 kcal/mol, respectively. DGEBF when added to DGEBA improves the Tg and char yield with the BF3 · MEA curing system. The Tg of both resin systems can be increased by longer post cure, whereas the char yield does not appear to change significantly. No ester group formation is found for the BF3 · MEA‐cured DGEBF, although this has been previously reported for the DGEBA system. The BF3 · MEA cure at 120°C is better than at 140°C because of vaporization and degradation of the curing agent at the higher temperature. The rapid gelation of the epoxy resin may be another reason for the lower degree of cure at high temperature.
A solid state NMR study on crystalline forms of nylon 6
Authors: Okada Akane , Kawasumi Masaya , Tajima Ichiro , Kurauchi Toshio , Kamigaito Osami
Published: April 2003

High‐resolution 13C‐NMR spectra were studied for two different crystalline structures of nylon 6 in the solid state by the cross polarization/magic angle spinning (CP/MAS) method. Two crystalline structures, α‐form and γ‐form, gave different chemical shifts for methylene carbons. The results showed that the hydrogen bonds between intermolecular chains are stronger in the γ‐form than in the α‐form. This strongly supports the results of the X‐ray study of nylon 6 by Malta et al. Our results also showed that interamolecular delocalization of positive charges occurs in the γ‐form through hyperconjugation in which the dihedral angle between the π bond and neighboring σ bonds is 30° while no such effect can be expected in the α‐form in which the angle is 0°.
Studies on swelling of cotton fibers in alkali metal hydroxides. II. Influence of morphology and fine structure on tensile behavior
Authors: Iyer P. Bhama , Sreenivasan S. , Patel G. S. , Chidambareswaran P. K. , Patil N. B.
Published: April 2003

Cotton fibers varying widely in gravimetric fineness but having nearly same percentage mature fibers have been subjected to swelling in 4.5N LiOH, NaOH, and KOH at room temperature and 0°C. The resultant changes in fine structure are analyzed by X‐ray diffraction and infrared absorption methods while variations in surface morphology are followed by scanning electron microscopy. Extent of swelling measured by changes in gravimetric fineness follows the order LiOH ≥ NaOH ≥ KOH, the exact gradation being dependent on the variety. Analysis of tensile data shows that whereas moderate swelling leads to an increase in tenacity at 3.2 mm gauge length, excessive swelling leads to a decrease of the same, the extent of decrease being a function of swelling. KOH treatment produced uniform swelling and gave better retention of T0 and T3 for all varieties. Tensile behavior after slack swelling in the various reagents could be interpreted on the basis of fine structural variations produced by them. However, the differential response of cottons to a swelling agent is explained by postulating variations in the packing of structural elements along the radii.
The effect of chemical treatment of wood and polymer characteristics on the properties of wood–polymer composites
Authors: Manrich Sati , Agnelli José Augusto Marcondes
Published: April 2003

The physical‐mechanical properties and the microscopic structure of caixeta (Chrysophyllum viride) and slash pine (Pinus elliottii) impregnated with polystyrene (PS) were investigated. The influences of a pretreatment with hydrogen peroxide (H2O2) solutions utilized in the production of the wood–polymer composites (WPC) and the characteristics of polystyrene formed in situ on the properties of WPC were analyzed. The incorporation of polystyrene improved the compression and static bending properties of slash pine and caixeta. The micrographies confirmed that there were distinct but continuous phases of polymer and wood cell wall which granted the composites a better physical‐mechanical behavior. The sensibilizing treatment with dilute hydrogen peroxide solution led to an increase in the viscosity average molecular weight (Mv) of polystyrene, and to the graft polymerization of the monomer, which, in turn, enhanced the stress properties of caixeta–polystyrene composites. Concentrated H2O2 solutions degraded caixeta wood, decreasing its tensile properties. Lower initiator concentration favoured higher molecular weight of polystyrene formed in pine wood. A fivefold increase in Mv of PS, however, had little effect on the compression properties of pine–polystyrene composites.
Preparation and swelling of polymeric hydrogels
Authors: Andreopoulos A. G.
Published: April 2003

Hydrogel polymers find extensive biomedical applications combining the properties of hydrophilic and crosslinked materials. In this work, poly(methacrylic acid) hydrogels were prepared by the copolymerization of methacrylic acid with varying amounts of 1,4‐butanediol dimethacrylate. The polymerization reaction was followed by viscometric measurements and the swelling properties of the samples prepared were also investigated. Alkaline treatment of the hydrogels was performed, to define the changes induced. Finally, a correlation between swelling data, derived from loosely crosslinked samples, led to the determination of the interaction parameter of the system poly(methacrylic acid)–water.
Study on the drawing behavior of poly(L‐lactide) to obtain high‐strength fibers
Authors: Postema A. R. , Pennings A. J.
Published: April 2003

The tensile drawing behavior of poly(L‐lactide) has been studied in order to obtain high strength fibers. Elongational viscosity measurements indicated that the hot drawing can take place in two temperature regions with different activation energies. Up to 180°C, the deformation proceeds in the semicrystalline state of the polymer having an activation energy of 15–28 kJ/mol, presumably by shear deformation. In the range of 180–190°C, the deformation proceeds in the liquid state of the polymer having an activation energy of 145–165 kJ/mol, leading to a semicrystalline state by strain hardening after displacement of topological defects. By using high deformation rates during drawing in a temperature gradient (tube drawing), the deformation will principally proceed in the semicrystalline region and inhomogeneous draw will take place leading to inferior fiber properties, unless the deformation rate and drawing temperature are strictly adjusted. Homogeneous drawing can be achieved by applying low deformation rates so that the deformation may take place in the liquid state of the polymer in which individual chains can be easily aligned and topological defects can be removed. Poly(L‐lactide) fibers with tensile strengths of 2.3 GPa have been produced in this way.
Chemical and property modification of silk with dibasic acid anhydrides
Authors: Tsukada Masuhiro , Shiozaki Hideki
Published: April 2003

In an attempt to provide information for improving silk fiber and fabric properties including crease recovery and yellowing, silk modification has been studied by using succinic and glutaric anhydrides. Glutarylation has been found to protect silk fibers from yellowing caused by the high energy radiation and to be more effective on increasing the crease proofing. The silk fabrics did not reduce the tensile properties such as strength and elongation at break even after the chemical modification with dibasic acid anhydrides. Thermal properties of the fibers remained unchanged in spite of the succinylation or glutarylation. From all the considerations of the survey of dye uptake, it would seem that the ester crosslinks are easily formed much more by the glutarylation than by the succinylation. The recovery values and yellowness indices of the modified silk fabrics and the measuring results of thermal and thermomechanical properties are explicable, taking into account of the different reactivity of the functional groups induced by the chemical modification with the dibasic acid anhydrides.
Coconut‐fiber‐reinforced rubber composites
Authors: Arumugam N. , Selvy K. Tamare , Rao K. Venkata , Rajalingam P.
Published: April 2003

Different formulations of rubber with chopped coconut fiber (treated and untreated) as reinforcing agent were prepared. These reinforced systems were vulcanized at 153°C and the properties of the vulcanizates were studied by stress–strain, shore A hardness, and abrasion loss measurements. The bonding between the rubber and fillers were improved by the addition of bonding agents. The bonding effect of different bonding agents were compared. The reinforcing property of the treated fiber was compared with the untreated one. Aging resistance of the composites were studied. The fracture surfaces have been studied by scanning electronmicroscopy (SEM) and the failure mechanism has been explained.
Nonisothermal orientation‐induced crystallization in melt spinning of polypropylene
Authors: Jinan Cao , Kikutani Takeshi , Takaku Akira , Shimizu Jiro
Published: April 2003

Two kinds of polypropylene with different molecular weight (MI = 15 and 30) were melt‐spun at the spinning temperatures of 210–290°C and take‐up velocities of 0.15–3 km/min. In the cases of the spinning temperatures of 270 and 290°C for MI15 and 250 and 290°C for MI30, the density showed a minimum with increasing take‐up velocity at around 0.5–1 km/min. This result suggests that crystallization behavior is influenced by two competitive effects, i.e., cooling rate and crystallization rate both of which are enhanced by the increase in take‐up velocity. Crystal structures of slightly oriented monoclinic, slightly oriented pseudohexagonal, highly oriented pseudohexagonal, and highly oriented monoclinic were successively observed with increasing take‐up velocity. The change of crystallization temperature may result in the different kinds of crystal modifications. Numerical calculations on nonisothermal orientation‐induced crystallization in the melt spinning process and experimental results showed qualitative agreement in the change of crystallinity with take‐up velocity, spinning temperature, and molecular weight.
Synthesis and antibacterial activity of copolymers having a quaternary ammonium salt side group
Authors: Senuma Masao , Tashiro Tatsuo , Iwakura Masahiro , Kaeriyama Kyoji , Shimura Yukio
Published: April 2003

Copolymers with a quaternary ammonium salt side group have been prepared from vinylbenzyl–cetyldimethylammonium chloride and acrylonitrile and their antibacterial activity has been examined with Bacillus subtilis, Staphylococcus aureus, and Escherichia coli. Growth inhibitory effect has been found to increase with the increase in the quaternary ammonium salt concentration in the copolymer. The effect is small on gram‐negative bacteria and large on gram‐positive bacteria.
Pervaporation separation of water/ethanol mixtures through polysaccharide membranes. III. The permselectivity of the neutralized chitosan membrane and the relationships between its permselectivity and solid state structure
Authors: Mochizuki Akira , Amiya Shigetoshi , Sato Yoshio , Ogawara Hisashi , Yamashita Shuzo
Published: April 2003

The separation of water/alcohol mixtures through chitosan membrane neutralized by various acids was investigated. The permselectivity of the neutralized chitosan membrane was affected by the species of acids and, only when neutralized by polybasic acids, was a marked increase of the selectivity observed and a high selectivity maintained for ion free mixtures. The marked increase of the selectivity could be explained by the contraction of the “holes” produced by the thermal motion of polymer chains due to the conformation change of chitosan molecule caused by the neutralization. The conformation change was confirmed by the analysis of the solid state structure of the neutralized chitosan using CP/MAS 13C‐NMR.
Permeation and diffusion of environmental pollutants through flexible polymers
Authors: Britton Larry N. , Ashman R. Brian , Aminabhavi Tejraj M. , Cassidy Patrick E.
Published: April 2003

Permeation and diffusion characteristics of high density polyethylene (HDPE), elasticized polyolefin, and polychloroprene membranes have been determined for various organic pollutants at 22 and 50°C. A standard ASTM permeation cell method was used to measure the permeation rate while an immersion/weight gain method was used to obtain the diffusion coefficient. Thickness‐dependent permeation rates were determined for HDPE membranes. An equimolar mixture of various permeants was also used to see the possibility of synergistic effects by combination of permeants. The experimental results are discussed in relation to the suitability of HDPE membranes in severe environments.
Treated aramid fibers as reinforcement in nonpolar matrices
Authors: Petsalas H. J. , Andreopoulos A. G.
Published: April 2003

Crosslinked polyethylene finds extensive use in applications where improved thermal resistance is required. Furthermore, reinforced and crosslinked polyethylene presents high strength at elevated temperatures, so that the field of applications of such materials is considerably enlarged. Aramid fibers seem to be a promising reinforcement for the above materials since they combine high modulus with thermal resistance and light weight. The development of an adequate adhesive bond between aramid fiber and polyethylene matrix is of course the main problem, taking into consideration that both polyethylene and aramid present reduced chemical affinity to other substances. Thus, fiber pretreatment was performed in order to insert unsaturated groups in the aramid chain. These groups could be, in turn, grafted in the polyethylene backbone during the crosslinking reaction. The aramid fibers were treated with methacryloyl chloride, and then dispersed under stirring in 2% aqueous sodium hydroxide containing 0.5% of a nonionic surfactant. After washing and drying, the fibers were dry blended with polyethylene powder containing 2 phr dicumyl peroxide. The mixture was melt‐blended in a Brabender plasticorder and tensile specimens were prepared. Tensile measurements and microscopy on the fracture surface were carried out in order to evaluate changes introduced in the fiber by surface treatment.
Kinetics of reaction of C21 cycloaliphatic dicarboxylic acid and ethylenediamine
Authors: Kale Vijay , Vijayalakshmi P. , Rao T. Chandrasekhara , Subbarao R. , Lakshminarayana G. , Rao M. Bhagwant
Published: April 2003

Kinetic studies were carried out on the reaction between ethylenediamine and C21 cycloaliphatic dicarboxylic acid, prepared from dehydrated castor oil fatty acids and acrylic acid, in melt phase. The reaction was performed at six different temperatures ranging from 210 to 260°C and followed by determining the acid value of the product. The polyamidation reaction was found to follow an overall third order kinetics with an activation energy of 15.5 kcal/g mol.
Effect of alkali on filaments of poly(ethylene terephthalate) and its copolyesters
Authors: Datye Keshav V. , Palan Bharat H.
Published: April 2003

The alkali hydrolysis of poly(ethylene terephthalate), anionic copolymer of poly(ethylene terephthalate), and block copolymer of poly(ethylene terephthalate)–poly(ethylene glycol) is investigated under a variety of conditions of alkali concentration in aqueous bath, additives, time, and temperature. Measurements of loss in weight, linear density, breaking load, tenacity, elongation to break apart from intrinsic viscosity, fiber density, COOH‐end group content, diameter of filaments, and scanning electron micrographs have been analyzed to identify the differences in the action of alkali on these polymer materials.
Orientation in composite of polypropylene and talc
Authors: Rybnikář F.
Published: April 2003

X‐ray diffraction and microscopical investigation of test samples prepared by injection molding from composites of isotactic polypropylene with talc revealed a preferred orientation of the talc and polypropylene matrix. Contrary to the situation in polypropylene alone, the preferred orientation in polypropylene–talc composites survived melting and a new crystallization. Crystallization rate measurements confirmed the nucleation activity of talc for polypropylene crystallization.
Solvent‐ and glow‐discharge‐induced surface wetting and morphological changes of poly(ethylene terephthalate) (PET)
Authors: Hsieh You‐Lo , Timm Debra A. , Wu Meiping
Published: April 2003

The effects of argon glow discharge and selected organic solvents on the surface wettability of poly(ethylene terephthalate) (PET) and on the wettability decay of glow discharged PET films were studied. Glow discharge in argon (30 W/1 min) drastically reduced the initial water contact angle (CA) measurement of PET from 67.0 to 26.2°. The glow‐discharge‐induced wetting, however, decayed during the first 7 days and stabilized at 33.1°. Treatments in dimethyl sulfoxide, dimethyl formamide, pyrdine, and water at 80°C caused some improvement in surface wettability as shown by decreases of water CAs in the range of 53–56°. When the solvent and glow discharge treatments were applied consecutively on PET, additive effects on improving surface wettability were observed. The stabilized water CAs of the solvent‐and‐glow‐discharged films ranged from 25.0 to 32.1° depending upon the solvent type. The solvent treatments prior to glow discharge either reduced the extent of CA decay or the time taken to reach stabilization on PET films. Scanning electron microscopic evaluation showed no difference between the solventtreated and the untreated PET surfaces, but a finely etched surface was observed on the glow discharged PET at a 40,000 magnification and above. The distinctly different surface of the DMSO‐and‐glow‐discharged PET indicated that morphological changes on PET surface were induced by the solvent.
A comparison of chemorheological models for thermoset cure
Authors: Mijović Jovan , Lee Chee Hung
Published: April 2003

A chemorheological study of a thermoset system consisting of diglycidyl ether of bisphenol‐A (DGEBA) epoxy resin and a mixture of two armoatic amine curing agents; 4,4′ methylenedianiline (MDA) and m‐phenylene diamine (m‐PDA), was conducted. Experimentally obtained viscosity data were checked against the predictions of two different viscosity models; one based on a phenomenological equation obtained by modification of the classical Williams–Landel–Ferry (WLF) equation and the other based on an extension of the branching theory originally proposed by Flory. In general, the predictions of both models were in excellent agreement with experimentally obtained isothermal and dynamic viscosity data. The branching theory model was found to have a slight advantage over the phenomenological equation model in describing the viscosity prior to gelation in a fast heating cure cycle.
Cure behavior of very thin epoxy resin films on steel
Authors: Nigro John , Ishida Hatsuo
Published: April 2003

FT‐IR reflection absorption spectroscopy has been used to investigate the effect of a steel surface on epoxide cure. BF3 · MEA catalyzed epoxy resin films ranging in thickness from 10 to 1000 nm are cast on low carbon automotive steel and subjected to a 100°C heat treatment. The resulting epoxide conversion and aliphatic ether formation are found to be sensitive functions of film thickness, with the thinnest films exhibiting the most conversion and ether formation. Uncatalyzed epoxy resin films (5–80 nm) were subjected to an identical analysis. Prior to receiving heat treatment, some of these very thin films (up to 10 nm) exhibit a strong aliphatic ether absorption. Upon exposing these samples to the heating regimen, a strong relationship between epoxide conversion and thickness is again apparent, with thinnest films experiencing the most conversion and ether formation.
A mechanism for flame retardation of poly(ethylene terephthalate)
Authors: Chang Po‐Hui , Wilkie Charles A.
Published: April 2003

The thermolysis of vinyl methylterephthalate has been studied as a model of poly(ethylene terephthalate) (PET) thermolysis. Based upon this reaction, a potential mechanism for PET flame retardation is proposed. The assumption is made, based upon firm experimental evidence, that the initial step in PET degradation is formation of a vinyl ester and a carboxylic acid. The essentials of the mechanism are that this vinyl ester participates in a vinyl polymerization reaction and produces a linear polymer. This linear polymer then is involved in a chain‐stripping reaction with the loss of methylterephthalate and the concomitant formation of a polyene. In the last step, this polyene undergoes a cyclization reaction and yields a crosslinked product. There are two stages at which PET undergoes crosslinking: In the second step the linear vinyl polymer is produced; in the last step ultimate crosslinking with the formation of cyclic structure is observed.
Weathering of polyethylene (LDPE) and enhanced photodegradable polyethylene in the marine environment
Authors: Andrady Anthony L.
Published: April 2003

The outdoor weathering of polyethylene homopolymer under exposure in air and in sea water was studied. Rate of deterioration as indicated by the loss in mean ultimate extension was found to be slower when the material was weathered in sea water compared to that in air. The difference in rates is explained in terms of the lack of heat buildup in plastic material floating in sea water. A similar study on a commercially available ethylene–carbon monooxide copolymer indicated rapid photodegradation under both exposure conditions.
Sodium cellulose formation by activation process
Authors: Laszkiewicz B. , Wcislo P.
Published: April 2003

The formation of sodium cellulose is the first reaction step in some large scale derivatization process of cellulose, e.g., xantation or carboxymethylation, as well as in the mercerization of cotton. It was found that the sodium cellulose formation depends on some activators present in the steeping lye, as well as on the press ratio, steeping temperature, and steeping ley concentration. IR data and X‐ray scattering showed that the initial native cellulose was converted into an unoriented cellulose II in the lower concentration of steeping ley with presence of urea, thiourea, and sodium aluminate or zincate as activators. The sodium cellulose formed with activators was more reactive to xanthation than the cellulose from unactivated process.
Dynamics and structure development during high speed melt spinning of nylon 6. I. On‐line experimental measurements
Authors: Bheda Jayendra H. , Spruiell Joseph E.
Published: April 2003

On‐line experimental measurements of filament diameter, temperature, and birefringence as a function of distance from the spinneret were carried out during melt spinning of two nylon 6 resins of differing molecular weight. Filament tension was also measured. A rapid diameter attenuation or “necking” was observed in the spinline for both resins at take‐up velocities above 6000 m/min. Evidence of crystallization in the spinline was also observed at these high spinning speeds. An analytical technique was used to extract apparent elongational viscosity for each resin and heat transfer coefficient for the melt spinning process from the experimental results.
Bulk polymerization of polyurethane under high pressure
Authors: Park Kang Choo , Kim Sung Chul
Published: April 2003

The pressure effect on the reaction kinetics, molecular weight, and the microphase separation of the soft and hard segment of the polyurethane, synthesized under high pressure, was studied. The polymerization rate increased with increasing synthesis pressure and the activation energy of polymerization decreased with increasing synthesis pressure from 22.4 kcal/mol at 1 kg/cm2 to 19.4 kcal/mol at 3000 kg/cm2. The volume of activation of the polyurethane polymerization was −19.8 cm3/mol at 60°C. Microphase separation between soft and hard segment decreased with increasing synthesis pressure and increased with increasing synthesis temperature. Molecular weight and molecular weight distribution were not influenced by the synthesis pressure.
In situ reactive compatibilization in polymer blends: Effects of functional group concentrations
Authors: Saleem M. , Baker W. E.
Published: April 2003

Polystyrene (PS) and polyethylene (PE), along with their reactive counterparts, i.e., polystyrene having oxazoline reactive groups (OPS) and polyethylene with carboxylic acid groups (CPE), were melt blended in a Rheomix mixer. These blends were prepared by mixing these polymers in various proportions under a variety of conditions. In an alternate procedure the OPS, CPE graft polymer (OPS‐g‐CPE) was prepared by melt blending these two polymers beforehand, and subsequently this grafted polymer was used as a compatibilizer for PS–PE blends. The effects of the addition of OPS and CPE, on the one hand, and OPS‐g‐CPE, on the other hand, on the compatibility of PS–PE blends were investigated. The morphology of these blends was examined with a scanning electron microscope (SEM) and related to their tensile properties. The PS–PE blends are found to have the typical coarse morphology of incompatible blends and poor tensile properties while their reactive counterparts, OPS‐CPE blends, have fine grain microstructure and show improved tensile strength throughout the range and improved elongation in the PE‐rich blends. Relatively low concentrations of the reactive pair, oxazoline and carboxylic acid, are shown to be necessary to produce improved compatibility. The preblended graft copolymer OPS‐g‐CPE imparts compatibility to PS–PE blends also but not as effectively. This suggests that the addition of OPS and CPE during melt mixing of PS and PE forms OPS‐g‐CPE polymer at the interface and that these ingredients act as “in situ reactive compatibilizers” which improve physical properties.
Analysis of the cure kinetics of epoxy/imidazole resin systems
Authors: Heise M. S. , Martin G. C.
Published: April 2003

The reaction kinetics for the cure of epoxy resins with imidazoles were determined from Fourier transform infrared spectroscopy and differential scanning calorimetry studies. The diglycidyl ether of bisphenol A and phenyl glycidyl ether were cured with various concentrations of 2‐ethyl‐4‐methyl‐imidazole ranging from 4.0 to 100.0 mol %. The first step in the curing process is the formation of epoxide/imidazole adducts. These adducts initiate the etherification reaction which crosslinks the resin. The kinetics were determined and confirmed for both the adduct and the etherification reactions as a function of the imidazole concentration. A model was developed and used to predict the concentrations of the unreacted epoxide groups and the reaction products for a wide range of imidazole concentrations and cure temperatures.
Dynamic viscoelasticity of isoprene rubber reinforced with short cellulose fibers
Authors: Yano Shoichiro , Hirose Shigeo , Hatakeyama Hyoe , Westerlind Bo , Rigdahl Mikael
Published: April 2003

The dynamic viscoelasticity was investigated for isoprene rubber (IR) composites filled with untreated and chemically treated cellulose fibers. Mercerization and benzylation were employed as chemical treatments. Bleached kraft pulp and cellulose powder were used as cellulose fillers. By mixing cellulose fillers, the dynamic modulus E′ of IR composites was improved, especially above the glass transition temperature. Benzylation of cellulose fibers reduced E′ of IR composite, while mercerization increased it. A tan δ peak was observed at about −33°C at 110 Hz along with a shoulder peak at about −16°C for the IR composites. The intensity of the tan δ peak decreased when mixed with cellulose fillers. The shoulder peak next to the main peak could be separated assuming a Gaussian type equation; log E″ = D exp { −C[(1sol;T) − (1/T0)]2} where D is the maximum value of log E″ vs. 1/T curve, T0 is the maximum temperature, and C is a parameter to determine the width of the Gaussian function. From the Arrhenius plot of the frequencies against 1/T0, the apparent activation energies were calculated as 220–235 kJ/mol for the shoulder peak (α1 process) and ca. 180 kJ/mol for the main peak (α2 process). The α2 process is caused by the glass transition of the rubber matrix. The α1 process is assigned as the molecular motion of the rubber matrix strongly restricted by the fiber element.
Preparation of high modulus poly(vinyl alcohol) by drawing
Authors: Yamaura Kazuo , Tanigami Tetsuya , Hayashi Naoki , Kosuda Ken‐Ichi , Okuda Shigeyasu , Takemura Yumiko , Itok Masayasu , Matsuzawa Shuji
Published: April 2003

The preparation of PVA films and fibers with high modulus and high strength was examined. The high drawing was attained when both the drawing just before melting and the relaxation at room temperature were repeated. The maximum draw ratio was 40 for the films prepared from the gels of high molecular weight (HMW) a‐PVA (DP ‐ 12000)/water/dimethyl sulfoxide (DMSO) system (water/DMSO = 20/80). The degree of crystallinity of tthe dried gels prepared from the PVA/ethylene glycol (EG) system was high, 40–50%, and independent on the tacticity of PVA. The modulus of the fibers, prepared from the gels of HMW s‐PVA (DP = 15300)/EG system, drawn 15 times to its original length was the highest (120 GPa).
The dependence of properties of cellulose acetate propionate on molecular weight and the level of plasticizer
Authors: Sand I. Daniel
Published: April 2003

Thermal and mechanical properties were measured for solvent‐cast films of cellulose acetate propionate plasticized with triphenyl phosphate. Probabilistic models for the glass transition temperature, tensile heat deflection temperature, tensile modulus, break stress, and initial tear strength as functions of weight‐average molecular weight and level of plasticizer were developed. The glass transition temperature and the tensile heat deflection temperature were modeled well by functions of the level of plasticizer as the only variable, whereas models for the tensile modulus, break stress, and inital tear strength included molecular weight. Only the break stress showed a statistically significant term of interaction between molecular weight and level of plasticizer. This term was such that, for unplasticized films, increasing the molecular weight increased the break stress, whereas, for films formulated with 20 pph plasticizer, increasing the molecular weight decreased the break stress. Physical explanations for this interaction term are discussed.
Antisoiling of polyester (PET) by a novel method of plasma treatments and its evaluation by color measurement
Authors: Jahagirdar C. J. , Venkatakrishnan S.
Published: April 2003

Direct current and radiofrequency plasma treatment of different durations were given to polyester fabric to impart soil resistance. The soil repellency increased with increasing time of treatment. The possible mechanism of soil repellency is outlined. The evaluation of soiling has been made from CIE brightness variable Y with source D65 using Minolta Chromameter Reflectance II. This was well in agreement with the conventional reflectance measurement method using spectrophotometer. The plasma treatment system has the advantage of energy and floor space savings and pollution‐free atmosphere
Analysis of the formation and curing reactions of resole phenolics
Authors: So Solomon , Rudin Alfred
Published: April 2003

The chemical composition and molecular size distributions of a series of soluble resole phenolics was studied by high resolution 13C NMR, IR, GPC, and viscosity techniques. The curing reactions were then followed by IR and solid state 13C NMR techniques. The ultimate degree of cure increases with curing time and temperature. The molecular weight of the precursor resole can be increased with increasing formaldehyde/phenol mole ratio and increased condensation reaction time and temperature. The degree of cure achieved under given conditions is directly proportional to the molecular weight of the precursor resole. The condensation catalyst has a great effect on resole composition and molecular size. It also influences preferential methylolation at the para position to the phenolic OH group in the following increasing order Ba(OH)2, NaOH, Na2CO3. The curing pH affects the degree of cure as well as the type of linkages formed. Methylene bridges are almost exclusive at high or very low pH's, while dibenzyl ether bridges predominate at neutral pH. High resolution 13C NMR spectroscopy is the most powerful tool to study soluble resoles. Infrared spectroscopy supplies qualitative results. Solid state 13C NMR is useful to study polymers during the curing process but there are inherent limitations and potential errors in this method.
Heat resistant styrene/α‐methylstyrene copolymers made via continuous anionic polymerization at high temperature
Authors: Priddy Duane B. , Traugott T. D. , Seiss R. H.
Published: April 2003

Styrene/α‐methylstyrene (SAMS) copolymers were produced containing up to 67 weight % AMS. The polymerizations were carried out using anionic polymerization at high temperature (100°C) in a CSTR type reactor. The reactivity ratios for the anionic copolymerization of styrene (M1) and AMS (M2) were estimated to be r1 = 60 and r2 = 0.01. Thermal degradation of a SAMS copolymer containing 50 weight % AMS was studied and compared with free radical polystyrene (FRPS) and anionic polystyrene (APS). The relative rate of styrene monomer generation for the three polymers followed the order SAMS > FRPS > APS. The relative rate of loss of molecular weight for the three polymers was FRPS > APS > SAMS. This indicates that the main mechanism of thermal degradation of SAMS copolymers is depolymerization rather than chain scission.
Formation and characterization of cellulose films from a liquid crystalline solution of cellulose in ammonia/ammonium thiocyanate
Authors: Chen Yue‐Shen , Yang Kap Seung , Cuculo John A.
Published: April 2003

Films were cast from liquid crystalline solutions of cellulose in an ammonia (NH3)/ammonium thiocyanate (NH4SCN) solvent. Microscopic examination of the cellulose liquid crystalline solutions used for the film formation exhibited the so‐called conjugated phase. It displayed a fingerprint and a uniformly dispersed highly birefringent pattern. Without additives, the films made from these liquid crystalline solutions are clear, flexible, and have high strength comparable to commercial Cellophone® films. The infrared crystallinity index of the film was somewhat higher than that of other cellulose II materials.
Electrostatic properties of UV‐irradiated and surface‐grafted polymers
Authors: Uyama Yoshikimi , Ikada Yoshito
Published: April 2003

A polystyrene film, a poly(ethylene terephthalate) (PET) film, and PET fabrics were UV‐irradiated or surface‐grafted with various hydrophilic monomers. Their electrostatic properties were studied by measuring the triboelectric charges generated upon mechanical rubbing of these materials and by following the decay of the charges generated upon exposing the polymeric materials to a high electric field. The UV‐irradiated polymers carried lower electrostatic charges than those unirradiated after their surfaces were rubbed with a cotton fabrics under the same conditions. The generation of triboelectric charge depends on both the surface hydrophilicity and the past history of the specimens. Although hydrophilic groups introduced on the polymer surface by UV exposure exhibited little effect on decaying of the electrostatic charge, polymeric materials grafted with a large amount of water‐soluble polymers, especially with ionic polymers, showed lower triboelectric generation and faster decay of the static charge.
Glass transition temperatures of poly(methyl vinyl ether‐co‐maleic anhydride) (PMVEMA) and poly(methyl vinyl ether‐co‐maleic acid) (PMVEMAC) and the kinetics of dehydration of PMVEMAC by thermal analysis
Authors: Chung K. H. , Wu C. S. , Malawer E. G.
Published: April 2003

Three distinct peaks at 80, 175, and 325°C were identified in the dynamic derivative TGA curves of PMVEMA and PMVEMAC at a 10°C/min heating rate. These peaks were attributed to free water removal, anhydride formation, and polymer degradation, respectively. The kinetics of the anhydride formation were studied by isothermal TGA in the temperature range of 150–200°C. It was found to be an endothermic and first‐order intramolecular reaction with an activation energy of 18.8 kcal/mol. It was concluded from FT‐IR and DSC results that no intermolecular anhydride structure was present in the dehydration of PMVEMAC. This is different from the cases of the dehydration of poly(acrylic acid) and poly(methacrylic acid) in the literature. The limiting glass transition temperatures of PMVEMA and PMVEMAC were found to be 153 and 144°C, respectively. The higher glass transition temperature in PMVEMA as compared to PMVEMAC is attributed to the increase in stiffness in the main polymer chain by the five‐membered ring anhydride structure in PMVEMA.
The equation of state of a polydimethylsiloxane fluid
Authors: Fakhreddine Y. A. , Zoller P.
Published: April 2003

Experimental data for the dependence of the specific volume on temperature and pressure (PVT data) of a polydimethylsiloxane fluid with 100 cS viscosity are presented. The temperature range covered is 30–344°C and the pressure range is 0–200 MPa (0–29,000 psi). Coefficients for an empirical equation of state are reported. This equation of state is based on a polynomial fit to the zero‐pressure isobar, combined with the Tait equation. The maximum deviation in specific volume between the data and the fitted empirical equation of state is less than 0.006 cm3/g, or less than 0.05% of the volume, except at the highest temperature, where sample degradation is likely to occur. The isothermal compressibility and thermal expansivity are derived from the empirical equation of state, and both show a strong temperature and pressure dependence. Reducing parameters for the Simha–Somcynsky theoretical equation of state were found to be P* = 502 MPa, V* = 0.9765 cm3/g, and T* = 8175 K. A comparison between theory and experimental data at temperatures to 245°C (recommended upper use temperature) revealed volume deviations comparable to those obtained using the Tait equation.
Surface modification by continuous graft copolymerization. III. Photoinitiated graft copolymerization onto poly(ethylene terephthalate) fiber surface
Authors: Yao Zhang Pei , Rånby Bengt
Published: April 2003

Photoinitiated grafting is an excellent method to modify the surface properties of a polymer. The presoaking photografting method applied to poly(ethylene terephthalate) (PET) with acrylic acid or acrylamide as monomer using benzophenone as photoinitiator has been investigated. The photografting proceeds under nitrogen atmosphere in a continuous process. The relative intensity of the ESCA lines of nitrogen over carbon of the fiber grafted with acrylamide increased from 3–4% (background) to 8% for 20‐s irradiation time. Measured by titration, the amount of grafted poly(acrylic acid) is 0.821 and 1.528 mg/m2 with 0.5 M and 2.0 M acrylic acid concentration, respectively, in the presoaking solution at 10‐s irradiation time. The dyeability of the fiber, measured by UV absorption, improved. The concentration of initiator and monomer and the solvent used affected the grafting yield. Appropriate conditions promoted photografting of the poly(ethylene terephthalate) fiber. Acetone was a somewhat better solvent than methylethylketone and methylpropylketone.
The glass transition temperature (tg) as a parameter for monitoring the cure of an amine/epoxy system at constant heating rates
Authors: Wisanrakkit G. , Gillham J. K. , Enns J. B.
Published: April 2003

A continuous heating transformation (CHT) cure diagram displays the time and temperature of events that a material encounters during the course of continuous heating at different heating rates. For thermosetting systems, these events include gelation, vitrification, and devitrification. Analysis of isothermal data for a diglycidyl‐type epoxy/tetrafunctional aliphatic amine system, which is initially liquid at room temperature, indicated that kinetic control applied prior to vitrification; i.e., for Tg<Tcure (temperature of reaction). The parameters so obtained (i.e., order of reaction, Arrhenius pre‐exponential term, and activation energy) together with an experimental relationship between Tg and extent of reaction were used as a basis for modeling the onset of vitrification and devitrification in the CHT diagram. For heating scans from below Tgo (glass transition temperature of the reactants), initial devitrification occurs when Tcure first passes through the Tg of the initial reacting material, except for very low heating rates for which inital devitrification is not encountered. Vitrification is identified as the point at which Tg becomes equal to the increasing curing temperature. Diffusion control retards the reaction rate beyond vitrification. In the limiting case of complete retardation of the rate after vitrification, the reaction can proceed along the Tg = Tcure path as long as the additional reaction with increasing temperature is sufficient to increase Tg at least at the same rate as the heating temperature; devitrification occurs thereafter. The critical heating rates at which the material does not devitrify in the vicinity of Tgo, and that at which no vitrification is encountered, are calculated.
Study of particle morphology in polymer emulsions and their minimum film formation temperatures
Authors: Tongyu Cao , Yongshen Xu , Yuncheng Su , Fu Long , Xing Li , Yuhong Hu
Published: April 2003

In the present paper, the emulsion polymerization of methyl methacrylate–butyl acrylate and styrene–ethyl acrylate were carried out. Polymer emulsions with latex particles of different morphology were prepared. The relationship between the minimum film formation temperature of the polymer latexes and the morphology of the latex particles were studied, and the film‐forming mechanism of the polymer latexes with varied particle morphology was also discussed.
Deformation behavior of Kevlar fibers studied by Raman spectroscopy
Authors: Prasad Keshav , Grubb David T.
Published: April 2003

The tensile deformation of Kevlar fibers has been studied using Raman spectroscopy. The Raman bands shifted to lower wavenumbers and broadened with stress. The shift of the 1610 cm−1 Raman band per unit stress was about −2.5 cm−1/GPa in both Kevlar 29 and Kevlar 49. A simple one phase paracrystalline model is used to explain the observed shifts. The total increase in the width of the 1610 cm−1 Raman band was about 2.5 cm−1 and the increase in width was negligible till a stress of about 0.5 GPa.
Functionalization of polyethylenes and their use in reactive blending
Authors: Liu N. C. , Baker W. E. , Russell K. E.
Published: April 2003

The grafting of maleic anhydride (MAn) to low density polyethylenes (PEs) dissolved in 1,2‐dichlorobenzene (DCB) has been studied. Grafting was successful at temperatures of about 160°C both in air without initiator and under nitrogen with the radical initiator 2,5‐di(t‐butylperoxy)‐2,5‐dimethyl‐3‐hexyne (LPO). The presence of succinic anhydride grafts was shown by FTIR spectroscopy of the product; 1H‐NMR spectroscopy indicates that the grafts consist of single succinic anhydride units. The graft content was determined by nonaqueous titration, and the extent of crosslinking inferred from the melt flow rates (MFR) of the products. The effects of concentration of initiator, MAn, and PE on the graft content were determined; the influence of PE structure, reaction time, and temperature was also studied. Melt blending of the grafted PE with polystyrene containing oxazoline functional groups (OPS) was investigated using a Rheomix mixer. The interpolymer reaction which occurs during blending was studied by means of FTIR, and the morphology of the blends by scanning electron microscopy (SEM). Information was also gained from the change in torque viscosity during the blending process.