bluuebunny/crossref_metadata_2025 huggingface dataset:
The thermal and mechanical behavior of poly(ethylene terephthalate) fibers incorporating novel thermotropic liquid crystalline copolymers
Authors: Joslin Scott , Jackson Woodward , Farris Richard
Published: April 2003

This investigation explores the potential of improving the performance of poly(ethylene terephthalate) fibers by incorporating novel thermotropic liquid crystalline copolymers. Fibers were obtained by melt extrusion and the effect of processing conditions, i.e., spinning temperature, stretch ratio, and post treatment evaluated. The fibers were tested for mechanical performance, dimensional instability (shrinkage), and the development of shrinkage stresses. A segmented block copolymer consisting of rigid‐rod, diad, and flexible coil segments was found to improve the performance of poly(ethylene terephthalate) (PET) fibers. At a concentration of 20 wt %, the alternating block copolymer increased the tensile modulus of the fibers by 40% and decreased free shrinkage by 20% compared to neat PET. © 1994 John Wiley & Sons, Inc.
Young's modulus of transcrystallinities in semicrystalline thermoplastic composites
Authors: Zeng Hanmin , Zhang Zhiyi , Zhang Mingqiu , Xu Jiarui , Jian Nianbao , Mai Kancheng
Published: April 2003

In a fiber/semicrystalline polymer system, interphasial transcrystallinities might form between the fibers and the matrix bulk that is composed of spherulites. By using an analogy method, the Young's modulus Et of transcrystallinities in their growth direction was predicted by a well‐known composite modeling theory. It is shown that Et is a function of the polymeric lamellar morphology and crystallinity. It is higher than the Young's modulus Es of the bulk spherulites and positively affects the stiffness of the materials in which the transcrystallinities are formed. The study was focused on poly(ether ether ketone) (PEEK) but with polyethylene (PE) as a comparison. Also, it is demonstrated the various possibilities of the value ET and the ratio ET/Es for different polymeric matrices depending on their lamellar moduli and the amorphous‐phase ones. © 1994 John Wiley & Sons, Inc.
Demonstration of the possible competing effects of oxidation and chain scission in orientated and stressed polypropylenes
Authors: Horrocks A. R. , Valinejad K. , Crighton J. S.
Published: April 2003

A series of orientated polypropylene tapes and filaments with differing draw ratio were produced from two parent polymers containing antioxidant systems of different efficiencies. Lengths of tapes and filaments were exposed in air ovens at temperatures up to 130°C under “free” conditions, held at constant length or loaded to differing stress levels for prescribed times or to failure, whichever was earlier. Those morphological effects of oven ageing treatments as are identified from their subsequent tensile behaviors and densities have been reported elsewhere; this study reports the heat flux differential scanning calorimetric (HF‐DSC) observations of unexposed and exposed samples. The HF‐DSC curves of treated samples show, for the postfusion oxidative exotherm for oven‐exposed samples, positive shifts to lower values compared with an unexposed sample, of the extrapolated onset temperature (Ton). Analyses of the tensile, density, and HF‐DSC data suggest that during the initial stages of thermal degradation in air, chain scission competes with oxidation. The rates of the former are enhanced by the application of stress, and scission is considered the origin of the observed deterioration in tensile behavior. Concurrent oxidation during oven exposures affects subsequent autoxidative behavior but has little immediate influence upon the mechanical properties. © 1994 John Wiley & Sons, Inc.
Electropolymrization and physicochemical properties of polypyrrole p‐toluenesulfonate
Authors: Heo Gweon , Lee Dong Hoon , Kim Keu Hong
Published: April 2003

Polypyrrole p‐toluenesulfonate (PPTS) polymers were synthesized by the electrochemical technique from 0.2M pyrrole in 0:100, 1:99, 5:95, and 10:90 water/acetonitrile solutions containing 0.1M tetraethylammonium p‐toluene sulfonate (TEATS) as a supporting electrolyte. Following the cyclic voltammetry measurements, the number of electrons involved in the reaction was determined to be unity. The results of thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) showed that the weight loss was most reapid in the temperature range from 533 K to 768 K, and the maximum value of the reaction rate was 0.27 mg/min at 651 K. From the temperature dependence of the electrical condutivity and electron spin responance (ESR) measurement, a small pallaron hopping conduction was suggested for PPTS polymers. © 1994 John Wiley & Sons, Inc.
Synthesis and biocidal activities of polymer. III. Bactericical activity of homopolymer of AcDP and copolymer of acdp with St
Authors: Oh Sang Taek , Ha Chng Sik , Cho Won Jei
Published: April 2003

The bactericidal monomer 2,4,4′‐trichloro‐2′‐acrylolyoxydiphenyl ether (AcDP) was synthesized from 2,4,4′‐trichloro‐2′‐hydroxydiphenyl ether (DP) and acryoyl chloride in the presence of triethylamine in dry THF at 20°C. The synthesized AcDP was indentified by IR, 1H‐NMR, and GC‐MS spectra. The homopolymer of AcDP was obtained using BPO an an initiator in toluene at 70°C. Copolymer of AcDP and styrene (St) was synthesized with a free radical initiator at 70°C. Poly(AcDP) and poly(AcDP‐co‐St) were identified by IR and 1H‐NMR spectra. The maximum weight average molecualr weight (Mw) of poly(AcDP) and poly(AcDP‐co‐St)s were 4100 and 11600, respectively. The monomer reactivity ratios, r1 (AcDP) and r2 (St), determined by the Kelen–Tüdös method, were 0.16 and 0.33, respectively. The glass transition temperature and decomposition temperature of poly(AcDP) were 73.4°C and 348°C, respectively. The bactericidal activities of AcDP, poly(AcDP), and poly(AcDP‐co‐St) were studied using agar dish test. The bactericidal activities of AcDP and its polymers as well as DP agianst Pseudomonas Aeruginosa were very excellent compared to those of control polymers such as poly(St) and poly(ethylene‐co‐vinyl acetate). The bactericidal activities were decreased in the order DP > AcDP > poly(AcDP) > poly(AcDP‐co‐St) Against Pseudomonas Aeruginosa. © 1994 John Wiley & Sons. Inc.
Radical entry into particles during emulsion polymerization of vinyl acetate
Authors: Kshirsagar Ravindra S. , Poehlein Gary W.
Published: April 2003

The entry of free radicals (formed in the aqueous phase) into polymer particles is the subject of the present work. A model has recently been developed based on the postulate that the aqueous‐phase growth of the free radicals to a critical size is the rate‐determining step for entry. An experimental strategy was devised to study this phenomena. Polystyrene latex with a water‐insoluble inhibitor partitioned into the polymer particles was used as seed for secondary polymerization of vinyl acetate. This was done to form and isolate stable oligomers of the critical size. The presence of vinyl acetate oligomers was detected with Fourier transform infrared spectroscopy and thin‐layer chromatography. Fast atom bombardment–mass spectroscopy (MS) was used to determine the molecular weights of the oligomers. Though it was not possible to determine the precise size of the vinyl acetate oligomers formed, the MS results show that the number of monomer units in the oligomers has an upper bound of 12–14. The number of units in the oligomer of critical size was estimated to be about 5–6. These experimental results are quite close to model predictions; thus this work helps in corroborating the model. Additional work is necessary to conclusively validate this model. The experimental strategy used in this work has made it possible to determine the approximate size of oligomers formed in the aqueous phase during emulsion polymerization. © 1994 John Wiley & Sons, Inc.
A survey of polyvinylphenol blend miscibility
Authors: Landry M. R. , Massa D. J. , Landry C. J. T. , Teegarden D. M. , Colby R. H. , Long T. E. , Henriches P. M.
Published: April 2003

The effect of polymer structure on blend miscibility with polyvinylphenol (PVPh) has been studied for at least one polymer from a variety of polymer classes with potential hydrogen‐bond accepting groups: polyesters (aliphatic and aromatic), polycarbonates, polyimides, polyamides, polysulfones, polyurethanes, polyethers, polysiloxanes, poly(amideimides), and cellulose esters. Many of the polyesters, polyamides, and cellulose esters showed evidence of interaction and miscibility with PVPh. In most of the other cases, there was no sign of miscibility. Generally good correlation exists between thermal behavior and infrared spectral data. Where there is significant interaction seen between the polymers by FTIR, substantial miscibility is seen by DSC analysis. In some cases, the phase behavior depended on the blend preparation scheme. © 1994 John Wiley & Sons, Inc.
Study of thermal and dyeing behavior of isotactic polypropylene fiber graft copolymerized with acrylate monomers using preirradiation method
Authors: Mehta I. K. , Misra B. N. , Chauhan G. S.
Published: April 2003

In an attempt to modify isotactic polypropylene (IPP) fiber, grafting of acrylate monomers such as methyl acrylate (MA) and ethyl acrylate (EA) onto IPP has been carried out by preirradiation method in aqueous medium. Percentage of grafting has been determined as a function of various reaction parameters. Rate of grafting (Rg) and induction period (Ip) have been evaluated as a function of total initial monomer concentration. Methyl acrylate was found to be more reactive than ethyl acrylate toward grafting. Thermogravimetric analysis (TGA) indicates that the thermal stability of polypropylene fiber is significantly improved upon grafting. While polypropylene fiber could not be dyed by crystal violet, the grafted fiber was dyed with crystal violet, and the dye uptake has been quantitatively determined by spectrometric method. © 1994 John Wiley & Sons, Inc.
PTC effect of polymer blends filled with carbon black
Authors: Jia Wentao , Chen Xinfang
Published: April 2003

Low‐density polyethylene/ethylene‐propylene‐diene terpolymer (LDPE/EPDM) blends and LDPE/ethylene‐ethyl acrylate (EEA) blends were chosen as objects of study. Their positive temperature coefficient (PTC) phenomena and their distinctive aspects were described. The explanations were given from the structural characteristics of the blends. © 1994 John Wiley & Sons, Inc.
Polymeric phosphonium salts as a novel class of cationic biocides. X. Antibacterial activity of filters incorporating phosphonium biocides
Authors: Kanazawa Akihiko , Ikeda Tomiki , Endo Takeshi
Published: April 2003

Phosphonium salts with different alkyl chains as substituents were incorporated covalently on the surfaces of cellulose filters with silane coupling agents containing phosphonium ions, and their surface antibacterial activities against Staphylococcus aureus and Escherichia coli were explored by the viable cell‐counting method in sterile distilled water. The filters incorporating phosphonium biocides showed higher antibacterial activity, and its activity strongly depended on the structure of substituents. The surface‐treated filters may be used to sterilize air and water, including microorganisms. © 1994 John Wiley & Sons, Inc.
Dynamic mechanical properties of polyurethane–urea microcapsules on coated paper
Authors: Ichikawa Kimio
Published: April 2003

Polyurethane–urea microcapsules were prepared by an interfacial polymerization method. Dynamic mechanical measurements were carried out on the polyurethane–urea microcapsules coated on a paper substrate. The glass transition temperatures (Tg) of capsule wall were observed in the temperature scan data. Tg as the temperatures of tan δ peaks were decreased with increasing amounts of core materials. The apparent activation energies of the glass transition were estimated at about 100 kcal/mol. Master curves were obtained by shifting the tan δ spectra along the frequency axis, and the glass transition regions were unaffected by core materials studied. The shift factors were found to depend on the core/wall ratio and discussed in terms of a morphological change of microcapsules. © 1994 John Wiley & Sons, Inc.
Effect of polycyclopentene on crystallization of isotactic polypropylene
Authors: Lee Dong‐Ho , Yoon Keun‐Byoung
Published: April 2003

The application of some polymers as nucleating agents for polypropylene has been examined. Among various polymeric nucleating agents, polycyclopentene was found to be a superior nucleating agent to typical organic nucleating agents. When polycyclopentene was added to polypropylene, the crystallization temperature and the degree of crystallinity of polypropylene increased. In addition, the crystallization rate and the number of spherulites increased whereas the size of spherulites decreased remarkably. As a result of polycyclopentene addition, the transparency of polypropylene film could be improved considerably. © 1994 John Wiley & Sons, Inc.
Preparation of cationic starch containing quaternary ammonium substituents by reactive twin‐screw extrusion processing
Authors: Carr M. E.
Published: April 2003

Cationic starch, an important additive for papermaking and other uses, was prepared from native cornstarch and 3‐chloro‐2‐hydroxypropyltrimethylammonium chloride in aqueous sodium hydroxide using a twin‐screw extruder as the reactor. The effects of physical and chemical reaction variables on reaction efficiency (RE) and degree of substitution (DS) of up to 0.05 were studied. RE was based on nitrogen content contributed by cationization of the starch after the products were exhaustively washed to remove unreacted monomer. Under certain reaction conditions, exceptionally high RE (90%+) was achieved, exceeding maximum values previously reported using laboratory‐batch reaction procedures. The combined effects of high reaction temperature (90°C), intense mixing, high‐starch solids (65%), and appropriate levels of catalyst contributed to the unusually high RE values achieved by the reactive extrusion process. © 1994 John Wiley & Sons, Inc.†
Thermal analysis of controlled‐release formulations based on entrapment of a larvicide in cross‐linked carboxymethylcellulose
Authors: Prasad M. P. , Kalyanasundaram M.
Published: April 2003

Thermal analysis of controlled‐release formulations of fenthion, prepared by its entrapment in cross‐linked carboxymethylcellulose and carboxymethylcellulose–gelatin matrices was carried out by thermogravimetric analysis and under accelerated storage conditions. Thermograms of samples of sodium carboxymethylcellulose, cross‐linked polymer samples, and the formulations were studied. The thermogravimetric analysis showed improved heat resistance and retention of fenthion or its decomposition products in the formulated samples. The decomposition maximum of technical‐grade fenthion was 260°C and the corresponding weight loss was about 90%, whereas fenthion or its decomposition products appear to be retained up to temperatures ranging from 400 to 500°C in the formulations. The half‐life of fenthion in the mechanical mixture with the carrier polymer was found to range from 19.92 to 29.98 days, whereas in the formulated samples, it was found to range between 41.54 and 113.35 days. © 1994 John Wiley & Sons, Inc.
Addition‐cured silicone adhesive technology: Vinyl silicone crosslinker
Authors: Lin Shaow B.
Published: April 2003

Silicone pressure‐sensitive adhesives prepared from a platinum‐catalyzed, high solids silicone composition are described. The adhesive compositions consist of an MQ siloxane resin, vinyl‐and hydride‐terminated silicone fluids, and a multifunctional vinyl silicone crosslinker. In this study, multifunctional vinyl silicone crosslinkers of various structures, including linear polymers, T, TQ, and Q resins, were prepared and evaluated for their effect on the adhesive properties of cured silicone pressure‐sensitive adhesives. Additionally, the activity of these multifunctional vinyl silicones in hydrosilylation reaction was investigated. © 1994 John Wiley & Sons, Inc.
Simple 13C‐NMR methods for quantitative determinations of polyflavonoid tannin characteristics
Authors: Thompson D. , Pizzi A.
Published: April 2003

A simple 13C‐NMR method for the quantitative determination of polyflavonoid tannin characteristics was developed. The system is effective for use on concentrated (25–50%) solutions of natural and modified tannins. It allows the determination of the average degree of polymerization (DPn) of the polyflavonoid, resorcinol vs. phloroglucinol proportion of the A‐ring and catechol vs. pyrogallol proportion of the B‐ring. The results obtained are consistent with existing data determined by other techniques. The method was also tried with tannin extract that was modified to form thermosetting adhesive intermediates, and with tannin modified by sulfonation, a common commercial modification for these materials. The results were again consistent with what was expected. The method affords the possibility to follow by a simple technique the variations in DPn and MM̄n (number‐average molecular weight) induced by chemical modifications of polyflavonoid tannin extracts and thus to correlate them with relevant structural modifications affecting these parameters. The method is not capable of distinguishing the relative proportions of the four important flavonoid units present in commercial polymeric tannin extract. It can only distinguish the relative proportions of (i) (procyanidins + prodelphinidins) vs. (profisetinidins + prorobinetinidins) and (ii) (prorobinetinidins + prodelphinidins) vs. (profisetinidins + procyanidins). © 1995 John Wiley & Sons, Inc.
Low loss second‐order nonlinear optical polymers based on all organic sol‐gel materials
Authors: Jeng R. J. , Hsiue G. H. , Chen J. I. , Marturunkakul S. , Li L. , Jiang X. L. , Moody R. A. , Masse C. E. , Kumar J. , Tripathy S. K.
Published: April 2003

A new class of all organic sol‐gel second‐order nonlinear optical (NLO) materials based on hexa(methoxymethyl) melamine (HMM) was developed. Two NLO active chromophores, 4 (4′‐nitrophenylazo) aniline (DO3) and 4‐amino‐4′‐nitrobiphenyl (ANB), were incorporated into the melamine matrices. The samples exhibited second‐order optical nonlinearity after poling and curing at 220°C for 30 min. DO3/HMM and ANB/HMM samples showed a second harmonic coefficient, d33 of 10.7 and 1.8 pm/V at 1064 nm, respectively. The temporal stability of both systems was studied at room temperature as well as at 100°C. Waveguide optical losses of samples at 633 and 830 nm were found. © 1995 John Wiley & Sons, Inc.
Effect of process parameters on residual stress distribution in poly(ethylene terephthalate) fibers and films as revealed by chemical etching
Authors: Gupta V. B. , Radhakrishnan J. , Sett S. K.
Published: April 2003

Poly(ethylene terephthalate) fibers and films produced by varying process parameters, such as production speed and medium, temperature and rate of drawing, were annealed at temperatures between 100 and 250°C in the free‐to‐shrink and constant‐length conditions. The as‐spun, as‐drawn, and drawn and annealed samples were etched in 40% aqueous methylamine at room temperature for 4 h. The etch patterns were examined on a scanning electron microscope and were found to be related mainly to residual stress and its distribution in the samples and thereby to sample morphology. The studies clearly bring about the important role played by the processing history. © 1995 John Wiley & Sons, Inc.
Effects of added metal ions on the interaction of chitin and partially deacetylated chitin with an azo dye carrying hydroxyl groups
Authors: Shimizu Y. , Kono K. , Kim I. S. , Takagishi T.
Published: April 2003

The binding of chrome violet, which is a monoazo dye and involves two hydroxyl groups in the o and o′ positions to an azo group, to chintin and partially decetylated chitin, was examined in the presence of metal ions. Zn2+ and Cu2+ ions do not perceptively influence the binding affinity of chrome voilet to chitin. In contrast, Co2+ ion enhances the binding and Ni2+ ion suppresses it. In the lower free dye concentrations the dye uptake by partially deceteylated chitin was tremendously enhanced by adding. Co2+ ion in the buffer solution of pH 5. The dye uptake by the polymer was considerably increased by the addition of Cu2+ ion at pH 5 and became much larger at pH 6. The amount corresponded to that in the presence of Co2+ ion. To investigate further the action of added metal ions, a cobalt‐ or a chrome–complex dye was prepared, and the binding properties for the polymers were compared with those of chrome violet in the presence of Co2+ and Cu2+ ions. Some possible mechanisms for the enhancement of chrome violet binding by the addition of Co2+ and Cu2+ ions are described. © 1995 John Wiley & Sons, Inc.
Mechanism of proton doping in polyaniline
Authors: Wan Meixiang , Yang Jiping
Published: April 2003

The protonation processes of polyaniline (PANI) were examined by means of both UV‐visible and fluorescence spectra and in situ UV‐visible and in situ electron spin resonance (ESR) spectra in order to understand he mechanism of proton doping in PANI. Results obtained from UV‐visible and fluorescence spectra of PANI films indicate that the protonation processes take place on the imine segment of the polyemerldine chain consistent with MacDiarmid's suggestions. It is noted that the protonation processes consist of chemical and diffusion processes. The doping processes at the initial stage are controlled by a chemical reaction, whereas the doping processes at the middle period are dominated by a diffusion process. In situ ESR spectra of PANI films have demonstrated that a polaron is formed after protonation processes, but a splitting process of bipolaron into polaron at the measured time region was not observed. For partial protonated PANI, moreover, the fact that variation of absorption value of the peak at 630 nm with doping time supported suggestions in which a parameter of the protonation state for the molecular structure of doped PANI should be considered. © 1995 John Wiley & Sons, Inc.
Sorption of aromatic compounds on macroporous anion exchangers based on polyacrylamide: Relation between structure and sorption behavior
Authors: Drăgan Stela , Cristea Mariana , Airinei A. , Poinescu Ig. , Luca Cornelia
Published: April 2003

The sorption of phenol, p‐toluenesulfonic acid (p‐TSA), Na‐p‐toluenesulfonate (Na‐p‐TS), 1,2‐dihydroxy‐3,5‐benzene disulfonic acid disodium salt (Tiron), and 3‐hydroxy‐4(sulfonaphthyazo)‐5,7‐naphthalenedisulfonic acid trisodium salt (Poceau 4R) on the macroporus anion exchangers with acrylamide structural units (weak and strong basic anion exchangers) and on the ion exchangers with amidoxime groups were studied. The maximum specific sorption of p‐TSA was almost identical with the total exchange capacity for both the weak and strong basic anion exchangers. The sorption of Na‐p‐TS is strongly related to the functional group structure of the anion exchangers, being significant on the strong basic anion excahngers. The maximum specific sorption of Tiron was higher tan the total exchange capacity of the strong basic anion exchangers because it is mainly dependent on the ionic exchange properties. The morphological characteristics influenced only the establishement rate of the sorption equilibrium. The sorption of Ponceau 4R, which has the highest molecular weight, is important on the strong basic anion exchangers with high permanent porosity. The sorption of the organic anions is also dependent on the number of the sulfonic groups. © 1995 John Wiley & Sons, Inc.
Morphology and rheology of polysulfone/Vectra‐A950 blends
Authors: Magagnini P. L. , Paci M. , La Mantia F. P. , Surkova I. N. , Vasnev V. A.
Published: April 2003

Blends of polysulfone (PSu) with a liquid crystalline copolyester (Vectra‐A950; VA) have been prepared by melt mixing. Their morphology has been studied by scanning electron microscopy (SEM). Either blend specimens as obtained from the melt mixing or fibers drawn from the melt were used for the SEM analysis. Further information on the morphology of the blends was gained by extraction of the PSu phase with methylene chloride. Preliminary rheological characterization of the blends was made by measuring the viscosity curves at 290 and 300°C, with a capillary viscometer having a die of 1 mm diameter and L/D = 40. Finally, an attempt at improving the phase compatibility was made by synthesizing a copolyester, having the same structure of commercial VA, in the presence of preformed PSu and using the product as a possible compatibilizer.

It was demonstrated that the blends are composed of two immiscible phase showing poor adhesion. The LCP droplets could, nevertheless, be deformed into oriented fibrils under elongational flow conditions. The LCP particles were shown to coalesce into large domains, and to migrate toward the outer layer of, e.g., extruded rods, under the influence of appropriate flow conditions, thus showing that there is a strong mutual influence between morphology and rheology of these materials. © 1995 John Wiley & Sons, Inc.
Creep/recovery behavior of open‐cell foams
Authors: Phillips J. C.
Published: April 2003

Static measurements have been used to predict the dynamic response of ldquo;unboundedrdquo; open‐cell noninked (dry) and inked foam materials. Creep, ec(t), and recovery, er(t), were determined in compression from static and dynamic modes. Force measurements, f(t), and strain decay, e(t), were used to determine the change in creep, δec(t). The change in creep represents the plastic strain, ep1(t=th), and is uniquely defined by the recovery function, er(t=th), where th is the hold time. Creep and recovery results of various classes of foam materials and nonfoam materials were found to fit a master curve of the form Fr(t) =exp[–k′r(th)t] = [er(t) ‐ e00( th)]/[e0 (t = 0) ‐ e00(th)] at a reduced time of k′r(th) t [k′r(th)] C0/(th)a (where Co depends on the material's “dry” or “wet” state), a is a function of the type of material, and em is the permanent set]. These empirical results are applicable to printing ink transfer and print quality. Other important factors of concern are diffusion processes within the polymer matrix and the nature of the polymer (e. g., chemical constitution, porosity, molecular weight, and solubility). © 1995 John Wiley & Sons, Inc.
The effect of teflon™ coatings in polyethylene capillary extrusion
Authors: Hatzikiriakos Savvas G. , Hong Peter , Ho Wally , Stewart Charles W.
Published: April 2003

Two LLDPE resins were used in this work to determine the critical conditions for the occurrence of wall slip and melt fracture in capillary extrusion. It was found that the polymer‐metal interface fails at a critical value of the wall shear stress of about 0.1 MPa and, as a result, slip occurs. At values of wall shear strees of about 0.18 MPa the extrudate surface appears to be matte, while small amplitude periodic distortions (sharkskin) appear on the surface of extrudates at wall shear stresses above 0.25 MPa. Using a special slit die, the polymer–wall interface was coated with Teflon™ in order to examine the effect of this coating on the processability of polyethylenes. It was found that use of Teflon™ promotes slip, thus reducing the power requirement in extrusion and, most importantly, eliminates sharkskin at high extrusion rates. © 1995 John Wiley & Sons, Inc.
Mixed esters of chitin
Authors: Van Luyen Dang , Rossbach Volker
Published: April 2003

One of the main obstacles to the wider application of chitin in polymeric materials is its poor tractability due to unfavorable solubility properties. The solubility can be enhanced by introducing bulky acyl residues into the polymer (as in butyrylchitin and valeroylchitin). However, if modification is carried out with shorter‐chain carboxylic acids (as in acetylchitin), the solubility remains poor. By substituting the acetyl residues partially by butyryl residues (mixed ester formation), exclusive use of the bulky carboxylic acids can be avoided and yet good solubility is achieved. These relationships were shown by using high molecular weight mixed chitin esters, prepared with methanesulfonic acid as the solvent and catalyst. The mixed chitin esters, varying both in the overall degree of substitution (1.5‐1.9) and the molar ratios of butyryl‐to‐acetyl residues (1: 0.62 to 1:0.72), were characterized by IR spectroscopy, DSC, elemental analysis, and 1H‐NMR spectroscopy (in trifluoromethanesulfonic acid); the latter allowed the degree of substitution to be determined as well as the moral ratios of butyryl‐to‐acetyl residues © 1995 John Wiley & Sons, Inc.
Injection molding of semicrystalline polymers. II. Modeling and experiments
Authors: Isayev A. I. , Chan T. W. , Gmerek M. , Shimojo K.
Published: April 2003

The injection molding of an isotactic polypropylene was computer‐simulated with both quiescent and shear‐induced crystallization taken into account. A one‐dimensional finite difference model was used to simulate the filling, packing, and cooling stages of the injection‐molding cycle. The Spencer‐Gilmore equation was used to relate the density variations to the pressure and temperature traces in the packing simulation. The quiescent crystallization kinetics was modeled by the differential form of the Nakamura equation. The theory developed by Janeschitz‐Kriegl and co‐workers was used to model the shear‐induced crystallization kinetics. The pressure traces during the filling and packing stages of the molding cycle, the thickness of the shear‐induced crystallization layer, and the crystallinity profile throughout the thickness of the part were measured and compared with predicted values. © 1995 John Wiley & Sons, Inc.
Influence of gamma‐irradiation on structural and mechanical properties of polypropylene yarn
Authors: Sen Kushal , Kumar Praveen
Published: April 2003

Polypropylene multifilament yarn samples were irradiated by gamma rays in air. The effect of radiation dose on thermal, structural, and mechanical properties was studied. Melting endotherms and crystallization exotherms gave useful information regarding the structural changes. X‐ray diffraction, infrared spectroscopy, density, and viscosity data of the irradiated samples were analyzed. Although viscosity and mechanical properties decreased with irradiation, the density marginally increased. Breaking elongation has been found be a sensitive parameter for assessing deterioration. © 1995 John Wiley & Sons, Inc.
Induced accelerated autocondensation of polyflavonoid tannins for phenolic polycondensates. II. Cellulose effect and application
Authors: Pizzi A. , Meikleham N. , Stephanou A.
Published: April 2003

Polyflavonoid tannin autocondensation was found to be facilitated by the reaction occurring on cellulose and lignocellulosic substrates. Although the mechanism of polyflavonoid autocondensation induced by cellulose differs from that induced by the action of Lewis acids, the subsequent reaction of autocondensation appears to be similar. The determining step of tannin rearrangement pathways under alkaline conditions in cellulose‐induced highertemperature autocondensation is the favoring of the heterocycle pyran ring opening over the normal interflavonoid bond cleavage and catechinic acid rearrangement. This is caused by relevant bond weakening and easier cleavage induced by strong attractive forces between flavonoid and cellulosic substrate. Applied bonding of cellulosic substrates by polyflavonoid tannin autocondensation reaction appear to be feasible and to occur as predicted from theoretical predictions. © 1995 John Wiley & Sons, Inc.
Grafting of methacrylic acid to loomastate viscose fabric using KMnO4/NaClO2 system
Authors: Hafiz S. A. Abdel , El‐Rafie M. H. , Hassan S. M. , Hebeish A.
Published: April 2003

Graft polymerization of methacrylic acid (MAA) to loomstate viscose fabric (greige fabric) using KMnO4/NaClO2 system was studied. Residual thiocarbonate and/or sizing materials on the fabric as well as presence of NaClO2 act in favor of primary radical formation which, in turn, accelerate formation of cellulose macroradicals capable of initiating grafting. The polymerization reaction was studied with respect to polymer yield, graft yield, homopolymer, total conversion, and graft efficiency. The magnitude of each of these characteristics was found to depend upon parameters such as concentrations of KMnO4, NaClO2, and MAA as well as liquor ratio, reaction time, and temperature of polymerization. By and large all these parameters enhance the polymerization process with the exception of the liquor ratio. A reaction mechanism for the polymerization reaction is also reported. © 1995 John Wiley & Sons, Inc.
Choice of monomer partition model in mathematical modeling of emulsion copolymerization systems
Authors: Gugliotta Luis M. , Arzamendi Gurutze , Asua José M.
Published: April 2003

A criterion for the choice for the monomer partition model in mathematical modeling of emulsion copolymerization systems is presented. In order to develop this criterion, seeded emulsion copolymerizations of several monomer systems with a wide variety of reactivity ratios and water solubilities were simulated using monomer partition models of different complexity. The simulations included different processes, solids contents and amounts of seed. The criterion for the choice of the monomer partition model was made on the basis of using the simplest but sufficiently accurate model. © 1995 John Wiley & Sons, Inc.
HTPB‐based polyurethanes for inhibition of composite propellants
Authors: Gupta D. C. , Deo S. S. , Wast D. V. , Raomore S. S. , Gholap D. H.
Published: April 2003

Polyurethanes were synthesized by the reaction of hydroxyterminated polybutadiene (HTPB) and diisocyanates such as toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), hexamethylene diisocyanate (HMDI), and isophoron diisocyanate (IPDI). A number of fillers such as carbon black, kaolin, and antimony trioxide (Sb2O3) were used in these formulations. Mechanical and thermal stability of these polyurethanes were studied. Based on its properties, HTPB‐MDI derived filled polyurethane was selected and evaluated as an inhibitor for a composite propellant. © 1995 John Wiley & Sons, Inc.
Studies on graft copolymerization of glycidyl methacrylate onto poly(vinyl chloride) and curing behavior of its grafted copolymer
Authors: Lee Wen‐Fu , Lai Cherng‐Ching
Published: April 2003

Poly(vinyl chloride) was dehydrochlorinated in an alkali solution and then grafted with glycidyl methacrylate (GMA) using benzol peroxide as the free‐radical initator under a nitrogen atmosphere. The efficiency of grafting GMA under the influence of an alkali, GMA concentration, and duration of the grafting reaction, the viscosity properties, and the curing behavior with diamine were investigated. Maximum grafting to the extent of 46.4% was obtained. The optimum curing reaction condition were investigated. © 1995 John Wiley & Sons, Inc.
Emulsion polymerization of methyl methacrylate in concentration of emulsifiers below their CMCs—polymerization rate, particle size, and particle‐size distribution
Authors: Yu Zai‐Zhang , Li Bo‐Geng , Cai Ming‐Jian , Li Bao‐Fang , Cao Kun
Published: April 2003

The emulsion polymerization of methyl methacrylate (MMA) in concentration of emulsifiers below their critical micelle concentrations (CMCs) initiated by K2S2O8 (KPS) was studied. It was observed that the initiator concentration has little effect on both polymerization rate and particle size. However, the polymerization rate is faster and particle size is smaller obviously when decreasing the ratio of the water/monomer or increasing the temperature of polymerization or the amount of the emulsifier. In the range of a 200–400 rpm stirring speed, the polymerization rate is almost unchanged although the particle size become larger with increase in the stirring speed. The monodisperse particle (size about 100–200 nm) can be obtained using this process. The mechanism of emulsion polymerization of MMA in the emulsifier concentration below its CMC is discussed. © 1995 John Wiley & Sons, Inc.
Chemical grafted 4‐vinylpyridine onto polycarbonate membranes for pervaporation
Authors: Chen Shih‐Hsiung , Lai Juin‐Yih
Published: April 2003

4‐Vinylpyridine‐homografted‐polycarbonate (PC‐g‐4VP) membrane was prepared for water perselective pervaporation. The conditions of the chemical grafting reaction for synthesis PC‐g‐4VP were studied in terms of the reaction time, reaction temperature, monomer concentration, and the concentration of initiator in the reaction. The effect of feed composition, degree of swelling, and operation on temperature on the pervaporation performances were investigated. It was found that water permeated through the PC‐g‐4VP membrane perferential in all range of feed compositions. The permeation rate and separation factor increased with increasing 4‐vinylpyridine content in the membrane. PC‐g‐4VP membrane effectively improved both the water permeation rate and water–ethanol separation factor of the unmodified polycarbonate membrane. The total permeation rate of PC‐4‐VP membrane with 26.7% degree of grafting was 153 g/m2 h, and the separation factor was above 6300 for a 90 wt % aqueous ethanol feed solution. © 1995 John Wiley & Sons, Inc.
Structure and properties of self‐reinforced polyethylene prepared by oscillating packing injection molding under low pressure
Authors: Guan Qing , Shen Kaizhi , Ji Jiliang , Zhu Jumu
Published: April 2003

This article reports the influence of oscillating pressure on the mechanical performance of general‐grade high‐density polyethylene (HDPE). The tensile strength of 93 MPa and the Young's modulus of 5 GPa were obtained by an oscillating packing technique. The great improvement of the mechanical properties of HDPE specimens is due to the existence of the shish‐kebab crystalline structure, the orientation of the molecular chains along the flow direction, and the more perfect crystallites. © 1995 John Wiley & Sons, Inc.
Reactivity of glycidyl‐methacrylate‐grafted cellulose prepared by means of photografting
Authors: Kubota Hitoshi , Ujita Shuji
Published: April 2003

Photografting was applied to functionalize cellulose, that is, epoxy groups were introduced into the cellulose substrate by photografting of glycidyl methacrylate (GMA) using hydrogen peroxide as a photoinitiator. Dissolving pulp from softwoods was used as the cellulose sample. The GMA‐grafted cellulose (G‐Cell) was subjected to the following examinations in comparision with epoxy‐activated cellulose (E‐Cell) prepared by reaction with epichlorohydrin: (1) reactivity of G‐Cell towards amines such as ethylenediamine, tetramethylenediamine, hexamethylenediamine, diethylenetriamine, and triethylenetetramine; (2) ability of the aminated celluloses obtained by examination (1) to adsorb cupric ion; and (3) catalytic activity of the aminated cellulose–cupric ion complexes prepared by examination (2) for decomposition of hydrogen peroxide. The amount of amine residue introduced into the substrate was higher for E‐Cell than G‐Cell, showing the existence of epoxy groups in G‐Cell which cannot contribute to the reaction. The ability of the aminated celluloses to adsorb cupric ion was nearly equal for G‐Cell and E‐Cell though tetramethylenediamine and hexamethylenediamine‐introduced samples did not show the ability. It was found that all complexes prepared by reaction of the aminated cellulose with cupric ion exhibited catalytic activity for decomposition of hydrogen peroxide. © 1995 John Wiley & Sons, Inc.
Modification of industrial polypropylene film by grafting of poly(acrylic acid)
Authors: Dogué Louis Joseph , Mermilliod N. , Gandini A.
Published: April 2003

Grafting of poly(acrylic acid) onto commercial polypropylene films following irradiation by γ‐rays was carried out in order to improve their surface properties. The amount of grafting with the irradiation dose was found not to follow the expected linear dependence as it is normally observed for polypropylene films prepared in laboratory amounts. We therefore analyzed the influence of the industrial manufacture process in terms of orientation of the film and addition of antioxidants by determining the peroxide surface density and the extent of grafting therefrom. The unoriented polypropylene film presented the highest peroxide concentration and was thus the most adapated material for successful grafting. Whereas phenol antioxidants limit the peroxide formation and thus must be removed from the film for grafting, the thickness of the chemical modification and can be controlled by means of phosphites. Atomicforce microscopy and wettability measurements showed that the grafted poly(acrylic acid) was heterogeneously distributed on the surface of the film, explaining the observed low reproducibility of the grafting reaction. However, we observed that the polarity of the surface was increased by the grafting. © 1995 John Wiley & Sons, Inc.
Study of the chemical polymerization of pyrrole onto printed circuit boards for electroplating applications
Authors: Saurin M. , Armes S. P.
Published: April 2003

We have studied the deposition of thin films of a conducting polymer, polypyrrole, onto printed circuit boards (PCBs). Film formation occurs as a result of the in situ polymerization of pyrrole monomer using a 1 : 1 FeCl3/5‐sulfosalicylic acid oxidant complex in aqueous solution. We have optimized the polymerization conditions in order to coat a large number of PCBs with a single polymerization bath, while at the same time maintaining the quality of the conducting polymer coating (i.e., keeping its surface resistance below 104 Ω per square). These improvements were achieved simply by controlling the initial oxidant–monomer mole ratio such that the oxidant is always present in significant excess. We have also examined the formation of thick polypyrrole layers obtained from the progressive buildup of thin layers. The morphology and film thickness of these polypyrrole coatings have been studied by scanning electron microscopy. Some preliminary electroplating experiments using these polypyrrole–PCB composites are also described. © 1995 John Wiley & Sons, Inc.
A study on blends of liquid crystalline copolyesters with polycarbonate. I. Compatibility by transesterification
Authors: Su Koe‐Fu , Wei Kung‐Hwa
Published: April 2003

Blends of poly(bisphenol‐A carbonate) (PC) and synthesized liquid crystalline poly(oxybenzoate‐co‐ethylene terephthalate 40/60) (P46) were prepared through meltmixing in a Brabender mixer. The miscibility of the blends at different compositions and blending time was investigated with differential scanning calorimetry. The corresponding morphology of the blends was analyzed with scanning electron microscopy. It was found that for blends containing more than 20% P46 and mixed at 250°C or above the transesterification between PC and P46 took place. This transesterification was confirmed at a blend containing 40% P46 by nuclear magnetic resonance spectroscopy. The transesterification happened first between PC and the ester in the poly(ethylene terephthalate) (PET) block and then between PC and the ester in the polyoxybenzoate (POB) block. At 260°C and after 60 min' blending, the blend containing 30% P46 became an almost compatible system for appearing of a single glass transition temperature. This is also verified by the disappearing of P46 droplets in the PC matrix in the micrographs' observation. After 60 min' of blending, the compatibility of the system can be greatly improved even for the blend containing 40% P46 mixed at 260°C by the micrograph's observation. © 1995 John Wiley & Sons, Inc.
Stress–strain effects of mechanically degraded natural rubber latex
Authors: Nwanorh K. O. , Enyiegbulam M. E.
Published: April 2003

A well‐characterized fresh natural rubber latex with total solids content of 42.1% was subjected to high‐speed mechanical stirring for over 6 h. Mechanical and solution studies on samples withdrawn at intervals showed clearly that rubber degradation occurred within 4–5 h of continuous stirring. Such degradation in the liquid phase is considered to be of industrial importance in the rubber industry. © 1995 John Wiley & Sons, Inc.
Influence of disproportionated rosin acid soap on the emulsion polymerization kinetics of styrene
Authors: Mayer M. J. J. , Meuldijk J. , Thoenes D.
Published: April 2003

The effect of disproportionated rosin acid soap (DRAS) on the emulsion polymerization kinetics of styrene has been studied. Batch experiments reveal a significant influence of chain transfer and limited particle coagulation on the polymerization process. For the recipes studied, the number of growing chains in the emulsion and consequently the polymerization rate were found to be independent of the particle number during the interval of coagulation. However, for relatively large particles (dp ≈ 100 nm), the polymerization rate was proportional to the particle number, indicating Smith–Ewart case II kinetics. These effects have been shown to be well predicted by model calculations using a radical population balance over the particles. Since DRAS is derived from naturally occurring constituents found in pine trees, its performance, and with that the properties of the product latex, may vary significantly. However, if the performance of DRAS is known, the recipe and process conditions can be optimized. For this reason a procedure has been developed to quantify the performance of DRAS from the simple batch experiments discussed in this paper, the polymerization kinetics, and the information obtained about the coagulation process. © 1995 John Wiley & Sons, Inc.
Morphological and mechanical properties of PET‐LCP blend fibers
Authors: Mehta Sanjay , Deopura B. L.
Published: April 2003

Blends of poly(ethylene terephthalate‐co‐p‐oxybenzoate) (PET–PHB) with poly(ethylene terephthalate) (PET) have been studied in the form of as‐spun and drawn fibers. Mechanical properties of drawn blend fibers (DR‐6.0) up to 10 wt % liquid crystalline polymer (LCP) component exhibit significant improvement in modulus and strength. With the addition of 10 wt % LCP content in PET matrix, the modulus increases from 11.78 to 17.72 GPa, and the strength increases from 0.76 to 1.0 GPa in comparison to the PET homopolymer. With further addition of LCP content, the properties drop down. Scanning electron microscopy studies of drawn blend fibers show that up to 10 wt % LCP content the blends contain the LCP domains in the size range of 0.07–0.2 μm and are well distributed in the PET matrix. © 1995 John Wiley & Sons, Inc.
Miscibility studies of poly(ethylene oxide)–poly(vinyl acetate) blends by viscometry methods
Authors: Chen Xue , Hu Huizhen , Yin Jinghua , Zheng Changren
Published: April 2003

The intrinsic viscosities of poly(ethylene oxide)–poly(vinyl acetate) blends (PEO–PVA) have been measured in chloroform as a function of molecular weights of blend components and compositions. The interaction parameters Δb obtained from the modified Krigbaum and Wall theory and the differences between the intrinsic viscosities of polymer mixtures and the weight‐average intrinsic viscosities of the two blend components were both used to characterize the extent of miscibility of the blend mixtures. © 1995 John Wiley & Sons, Inc.
Evaluation of the amount of defects in the comonomer alternation included in the crystal phase for ethylene–tetrafluoroethylene and ethylene–chlorotrifluoroethylene alternating copolymers
Authors: De Rosa C. , Guerra G. , D'Aniello C. , Petraccone V. , Corradini P. , Ajroldi G.
Published: April 2003

A method for the evaluation of the amount of defects in the comonomer alternation included in the crystalline phase of alternating ethylene–tetrafluoroethylene (ETFE) and ethylene–chlorotrifluoroethylene (ECTFE) copolymers, is proposed. The method is based on a comparison between X‐ray fiber diffraction profiles and calculated Fourier transforms for isolated chain models. The proposed method is not affected by the regioirregularities and stereoirregularities possible for ECTFE. For the considered ECTFE sample, the chains in the crystalline phase present an amount of defects in the comonomer alternation much lower than those evaluated for all the considered ETFE samples. Substantial differences in the melting temperatures between ETFE samples are accounted for by the different amounts of defects in the comonomer alternation included in the crystalline phase. © 1995 John Wiley & Sons, Inc.