bluuebunny/crossref_metadata_2025 huggingface dataset:
Alginate polyelectrolyte ionotropic gels. VI. Novel synthesis of diketoalginates as biopolymer precursors
Authors: Hassan R. M. , Abd‐Alla M. A. , El‐Zohry M. F.
Published: April 2003

Sodium 2,3‐diketoalginate was quantitatively prepared by the oxidation of sodium alginate with potassium permanganate in alkaline solution at pH's > 12. The yield was 96.5%. The structure of the diketone was elucidated by microanalysis and spectroscopic data. It was found that the diketoalginate caused no gelation or precipitation with copper(II), nickel(II), or cobalt(II) divalent metal ions. © 1993 John Wiley & Sons, Inc.
Study of ketalization reaction of poly(vinyl alcohol) by ketones. VI. Reaction between poly(vinyl alcohol) and cyclic ketones and behavior of poly(vinyl ketal) in water
Authors: Nakamura Naofumi
Published: April 2003

The ketalization reaction of poly(vinyl alcohol) (PVAL) by cyclic ketones, with dimethyl sulfoxide (DMSO) as solvent, in the presence of an acidic catalyst in homogeneous system, was carried out. The synthesis of poly(vinyl ketals) was thus successfully performed, except for the case of poly(vinyl ketal) highly ketalized by cyclohexanone; these poly(vinyl ketals) with a ketalization degree of more than 60 mol % were insoluble in DMSO, and, thus, the reaction could not be carried out in a homogeneous system. The equilibrium constant at 40°C was ca. 0.50 in the case of cyclohexanone and ca. 0.35 in the case of cyclopentanone, some 10–50 times higher compared with the case of aliphatic ketones. Because the heat of reaction is 7.5 kcal/mol in all ketones, all ketalization reactions are considered to proceed by the same reaction mechanism. Films prepared from the poly(vinyl ketals) were soaked in water, and hydrolysis, degree of swell, and solubility were measured. The dissolution time of films is affected by the kind of the ketones, ketalization degree, and the pH of water, which reveals that deketalization reaction proceeds proportionally to the proton concentration. It is more difficult to dissolve poly(vinyl ketal) obtained by cyclohexanone than that by cyclopentanone. The rate of hydrolysis of poly(vinyl ketal) film obtained by cyclohexanone is nearly equal to that by methyl butyl ketone, and that by cyclopentanone is nearly equal to that by methyl propyl ketone. The contact angle, surface free energy, moisture regain, and water permeability of poly(vinyl ketal) films were measured. All the results show that poly(vinyl ketal) obtained from cyclohexanone is a more hydrophobic polymer than that from cyclopentanone. The hydrophobicity seems to depend upon the kind of the original ketones and the flexibility of the ring. © 1993 John Wiley & Sons, Inc.
Photopolymerization of methyl methacrylate using benzoin isopropyl ether as photoinitiator: Effect of thiophenol compounds
Authors: Wang W. , Hu G. H.
Published: April 2003

Effects of a series of thiophenols RArSH with substituting groups R in the para‐position and 2‐mercaptobenzoic acid on the kinetics of polymerization of methyl methacrylate (MMA) photoinitiated by benzoin isopropyl ether (BIPE) were investigated using an autorecording dilatometer. Thiophenols were found to have a dual effect on polymerization: reducing induction time and accelerating rate of polymerization. A mechanism was proposed suggesting that this increased rate of polymerization and reduced induction time with addition of a thiophenol is due to the fact that, instead of consuming radicals, the dissolved oxygen in the MMA/BIPE system can be converted into active radicals through effective photooxidation of the thiophenol. Although the maximum increase in rate of polymerization is of a minor difference between various thiophenol compounds, reduction in induction time is strongly dependent on the nature of substituting groups in the following order: CH3 > CH(CH3)2 > OCH3 or Cl > H. 2‐Mercaptobenzoic acid, on the other hand, increases induction time and decreases rate of polymerization. © 1993 John Wiley & Sons, Inc.
SEC–viscometer detector systems. II. Resolution correction and determination of interdetector volume
Authors: Cheung P. , Lew R. , Balke S. T. , Mourey T. H.
Published: April 2003

The closely related topics of resolution correction and the determination of interdetector volume were examined. In determining the interdetector volume (δ) by searching to superimpose two types of intrinsic viscosity calibration curve (one from narrow standards and one from a broad standard), the underlying equation based upon symmetrical axial dispersion theory was derived. This equation combined with experimental results showed that the local intrinsic viscosity value is very similarly affected by interdetector volume and by band spreading. The result supported the idea of using an effective δ to effect an axial dispersion correction to local intrinsic viscosity data. However, it also increased the difficulty of finding both δ and standard deviation (δ) simultaneously by numerical search. Furthermore, attempts to apply the method to the chromatograms of narrow standards showed inadequate superposition. Following calculation of skewing factors, the superposition problems were attributed to skewing of the chromatograms of the monodisperse polymer standards used. © 1993 John Wiley & Sons, Inc.
Thermal and morphological characterization of binary blends of fractions of 1‐octene LLDPE
Authors: Defoor F. , Groeninckx G. , Reynaers H. , Schouterden P. , Van Der Heijden B.
Published: April 2003

An ethylene/1‐octene linear low‐density polyethylene (LLDPE B) has been fractionated with respect to the short‐chain branching content of the molecules, using the preparative temperature‐rising elution fractionation (PTREF) technique. The LLDPE B studied, which is characterized by a high degree of heterogeneity on the level of the molecular weight and the comonomer content, was fractionated into six fractions having a more homogeneous intermolecular comonomer distribution. As a result of the differences in the chain microstructure of the fractions, a strong change in the thermal characteristics such as onset temperature of crystallization from the melt and melting temperature has been found. The morphology of the fractions, i.e., spherulitic texture and semicrystalline lamellar ordering, also strongly depends on the chain microstructure. In an attempt to elucidate the mutual influence of molecules having a different chain microstructure, as occurring within the unfractionated copolymer, blends of preparative TREF fractions were prepared and investigated with respect to their thermal behavior and morphology. © 1993 John Wiley & Sons, Inc.
Natural and artificial weathering of low‐density polyethylene (LDPE): Calorimetric analysis
Authors: Sebaa M. , Servens C. , Pouyet J.
Published: April 2003

Studies of the thermal and photodegradation of two commercial polymers, stabilized and unstabilized low‐density polyethylene, show the effects of weathering on differential scanning calorimetry (DSC) curves. The shape and the size of the melting peak vary significantly in thermal aging and in accelerated photoirradiation, but no change was observed in natural weathering, implying that the crystallinity remains steady in outdoor exposures. The melting temperatures remain steady for all exposure tests. The fall of mechanical properties and the evolution of chemical structure, followed by IR spectroscopy results, especially near the carbonyl regions, were also observed. The resistance to UV light irradiation as probed by deformation at break was superior in stabilized LDPE compared to unstabilized LDPE. Simple correlations observed between the fall of mechanical properties, the rate of oxidation, and morphology. © 1993 John Wiley & Sons, Inc.
Synthesis and characterization of cyano‐substituted maleamic acids and maleimides and their polymerization to thermally stable laminating resins
Authors: Mikroyannidis John A.
Published: April 2003

A novel class of cyano‐substituted maleimides were prepared and polymerized. Particularly, 4‐aminobenzonitrile reacted with maleic or nadic anhydride to yield the amic acid, which was then cyclodehydrated to the corresponding maleimide or nadimide. In addition, the monomaleamic acids prepared from an aromatic diamine reacted with 4‐cyanobenzaldehyde to afford maleamic acids that were cyclodehydrated to maleimides. All maleimides and nadimide as well as their intermediate amic acids were characterized by IR and 1H‐NMR spectroscopy. The curing behavior of polymer precursors was investigated by DTA. Upon curing at 240°C for 15 h, network polymers were obtained both by cross‐linking through the maleimido olefinic bonds and the trimerization reaction of the cyano groups. They were stable up to 330–310°C in N2 or air and afforded anaerobic char yield of 60–40% at 800°C. © 1993 John Wiley & Sons, Inc.
Anionic copolymers of octanelactam with laurolactam (nylon 8/12 copolymers). VII. Study of diffusion and permeation of gases in undrawn and uniaxially drawn (conditioned at different relative humidities) polyamide films
Authors: Arvanitoyannis Ioannis , Blanshard John M. V.
Published: April 2003

The permeability coefficient of a wide range (0/100–100/0 octanelactam/laurolactam [OL/LL] mol/mol) of novel copolyamides (nylon 8/nylon 12) was determined and related to the diffusion rate over a range of temperatures: Tg–30 to Tg + 40°C. An inflection in the plot of permeability vs. 1/T (K) provided an indirect indication of glass transition value and agreed satisfactory with DSC and DMTA measurements. Both uniaxially drawn and undrawn membranes were evaluated and the permeability values were correlated with the % crystallinity. The reduction in solubility, diffusivity, and permeability with increasing draw ratio was attributed to a substantial increase in % crystallinity. Finally, the effect of absorbed water on gas permeability of polyamide films was examined. In most homopolyamides and copolyamides, the higher the water absorption of films the higher the permeability values. © 1993 John Wiley & Sons, Inc.
NMR and sedimentation studies of a polymeric steric stabilizer for alumina
Authors: Parker A. A. , Armstrong G. H. , Hedrick D. P.
Published: April 2003

The sedimentation behavior of alumina powder has been studied in the presence of poly‐vinylpyrrolidone (PVP) and poly(vinylpyrrolidone‐co‐vinyl acetate) (PVP/VA) in both thermodynamically “good” and “poor” solvents for the PVP homopolymer. PVP/VA provides higher sediment densities than does its PVP homopolymer counterpart. Solutionstate 13C‐T1 spin‐lattice relaxation measurements were made on analogous mixtures both with and without alumina powder. The NMR results suggest that the PVP/VA copolymer is anchored to the alumina powder surface by means of VA moieties, whereas the PVP moieties extend into the continuous phase of the slurry medium. Thus, the higher settling densities that are observed in the presence of PVP/VA can be attributed to a steric stabilization mechanism. © 1993 John Wiley & Sons, Inc.
The use of liquid chromatography for the characterization of novolac resins
Authors: Podzimek Ŝ. , Hroch L.
Published: April 2003

Novolac resins made by condensation of phenol or p‐cresol with formaldehyde in various mole ratios were analyzed by reversed‐phase high‐performance liquid chromatography (HPLC) and gel permeation chromatography (GPC). Number‐average molecular weights (Mn) of phenol novolacs were determined by GPC and vapor‐phase osmometry (VPO) and compared. A relationship was found between the content of dihydroxydiphenylmethane (DHDPM) and Mn of phenol novolacs. Attention was also paid to the quantitative determination of the content of phenol and DHDPM in the analyzed samples. The molecular characters of novolacs synthesized from phenol or p‐cresol under the same conditions were compared. A relation was found between the molecular weight of phenol novolac and the tensile strength of abrasive material based on it. © 1993 John Wiley & Sons, Inc.
Dielectric and morphological investigations of phase separation and cure in rubber‐modified epoxy resins: Comparison between teta‐ and DDM‐based systems
Authors: Delides Costas G. , Hayward David , Pethrick Richard A. , Vatalis Argyris S.
Published: April 2003

Real‐time and equilibrium dielectric measurements, covering the frequency range 10−1–105 Hz, are reported on a series of rubber‐modified epoxy resins, based on reaction of the diglycidyl ether of bisphenol A (DGEBA) with either triethylenetetramine (TETA) or diaminodiphenylmethylene (DDM). The rubber modifier used was a carboxyl‐terminated butadiene acrylonitrile (CTBN) reactive oligomer and the phase‐separated structure, the results of which was examined using both dielectric and electron microscopic techniques. The mixture was initially homogeneous, but after a short period of time, it underwent phase separation and this process was marked by the appearance of a dielectric peak associated with ion‐charge migration within the occluded rubbery phase. Analysis of the peak provided information on the morphology of the system and these data were compared with information obtained from scanning electron microscopy. A phase‐separated morphology was observed consisting of spherical rubber particles dispersed in an epoxy matrix. For high concentrations of rubber ≥ 10 wt %, precipitation of epoxy domains within the rubbery phase was observed. Detailed dielectric studies of the peak associated with phase separation revealed that in the case of the TETA system the peak continued to shift after vitrification, whereas in the case of DDM, it was invariant with time. The point at which the peak appears was used to determine the time at which phase separation occurred. Differences observed in the lower temperature dielectric spectra were associated with variations in the form of the phase structure and possibly reflect different degrees of densification of the matrix. Good agreement was observed between the predictions of the Maxwell—Wagner—Sillers (MWS) theory and experimental observation for these systems. © 1993 John Wiley & Sons, Inc.
Surface modification of ultrahigh molecular weight polyethylene fibers by plasma treatment. I. Improving surface adhesion
Authors: Gao Shanglin , Zeng Yeguang
Published: April 2003

The fiber/epoxy resin adhesion increases after plasma treatment on ultrahigh molecular weight polyethylene (UHMW‐PE) fibers. The surface modification of UHMW‐PE monofilaments was studied using a combination of techniques: contact‐angle measurements, SEM, and pullout tests. The results may be summarized as follows: Infiuenced by different plasma parameters and draw ratios of the monofilaments, the adhesion increases by at least four times by plasma treatment. Failure in the pullout tests involve rupture within a treated monofilament and the skin of it was peeled off; the degree of peeling‐off is affected by different plasma treatment conditions and draw ratios of the monofilaments. There is only a slight decrease in the surface energy of the treated monofilaments with aging time. Ways of combining plasma etching with other chemical treatments to further improve the fiber/resin adhesion have also been studied. © 1993 John Wiley & Sons, Inc.
Electrochemically oxidative polymerization of aniline in aromatic copolyamide matrix
Authors: Xue Zhijian , Bi Xian‐Tong
Published: April 2003

Composite films from polyaniline (PAn) and a copolyamide, poly(p‐phenylene terephthalamide/diphenylether terephthalamide) (PPDTA), have been obtained by the electrochemical polymerization of aniline on a PPDTA/Pt (or Ni, stainless steel) working electrode in water or a mixed‐solvent electrolyte solution. This PAn/PPDTA composite has higher mechanical properties than does the PPDTA matrix and the electrical conductivity close to pure PAn. The electrochemical polymerization of aniline can be carried out only in the electrolyte solution with PH < 2. The PAn/PPDTA film is electroactive material and very stable in air. © 1993 John Wiley & Sons, Inc.
Kinetic and thermogravimetric analysis of thermal degradation of polychlal fiber/polyester fiber blend
Authors: Fukatsu Kazuhiko
Published: April 2003

The flammability behavior of a series of polychlal fiber/polyester fiber blends has been investigated in terms of the oxygen index and the thermal degradation characteristics. The thermal degradation behavior of these fiber blends has been studied by a conventional dynamic thermogravimetric technique in a flowing air atmosphere at several heating rates. Quantitative data are presented that pinpoint how the flammability behavior of the blends differs from that of the components. These results indicate that interactions occur between the polychlal and polyester fibers in the blends. © 1993 John Wiley & Sons, Inc.
Thermally stimulated current of iodine‐doped acrylonitrile–butadiene–styrene thin films
Authors: Bakr N. A.
Published: April 2003

Structural change of acrylonitrile–butadiene–styrene (ABS) terpolymer due to iodine doping has been reported using both infrared (IR) and thermally stimulated current (TSC) techniques. IR investigation revealed the presence of a new stretching band at 640 cm−1 that indicates the formation of the C‐I structure. The TSC spectrum consists of two different decaying charge distributions of opposite polarity, which simply superpose to yield the net current observed. The variation of the position of the negative peak relaxation and its intensity as the iodine percentages increases indicates the formation of different ionic iodine species. The induced ionic dipoles superpose the α‐relaxation of ABS. © 1993 John Wiley & Sons, Inc.
Reductions in rate of yellowing following irradiation of poly[N(n‐butoxymethyl) methacrylamide]‐grafted silk fibers
Authors: Tsukada Masuhiro , Shiozaki Hideki , Crighton John S. , Kasai Nobutami
Published: April 2003

The physical properties, including changes in the yellowness index, following UV irradiation of Bombyx mori silk fibers loaded with poly[N(n‐butoxymethyl) methacrylamide], poly(BMA), are examined in relation to the amount of held polymer. The percentage weight gain by the silk fibers observed after 45 min at 80°C increased with increasing initial amounts of BMA monomer in the reaction system. Differential scanning calorimetry (DSC) observations suggest that the thermal decomposition behavior of the heated silk fiber was little affected, with but an apparent small shift of the endothermic decomposition temperature range to higher temperatures. The tensile properties of the treated silk fibers remained effectively unchanged, independent of the polymer weight gains. There was, however, a marked effect of the poly(BMA) weight gains onto silk in maintaining the whiteness and reducing the rate of yellowing following irradiation of treated habutae silk fabrics. These observations suggest that the rate of photoyellowing of silk fabrics can be retarded by the presence of the poly(BMA) in the fabric. © 1993 John Wiley & Sons, Inc.
The viscometric methods in the investigation of the polyacid‐polybase interpolymer complexes
Authors: Staikos G. , Bokias G. , Tsitsilianis C.
Published: April 2003

Two viscometric methods in the investigation of interpolymer complexes are presented. It has been shown that a presentation of the reduced viscosity ratio (experimental to ideal value) of a mixture of a polyacid with a nonionic polymer at constant total concentration as a function of the polymer mixture composition gives a better insight into the interpolymer association than a presentation of the specific viscosity at constant polyacid concentration as a function of the unit molar ratio. The formation of an expanded structure interpolymer complex is more easily revealed by the former procedure. © 1993 John Wiley & Sons, Inc.
Properties of hydroxypropyl methylcellulose–polyvinyl alcohol water systems, dispersants in vinyl chloride suspension polymerization
Authors: Zilberman E. N. , Lerner F. , Joseph H. M. , Alon M.
Published: April 2003

Aqueous solutions of partly hydrolyzed polyvinyl acetate (polyvinyl alcohol, PVA) and hydroxypropyl methylcellulose (HPMC) are used together as dispersants in vinyl chloride suspension polymerization. Surface tension, viscosity, and cloud point (CP) of diluted PVA and HPMC solutions at room temperature, viscosity of concentrated solutions as a function of temperature, and incipient gelation temperatures (IGT) were determined. Viscosity measurements show synergism of binary polymer mixtures. The synergetic effect diminishes with rise of temperature. IGT of PVA–HPMC solutions do not differ remarkably from those of solutions containing only HPMC and are much higher than the corresponding CP. At definite relative concentrations of HPMC and PVA, separation of the mixtures into two immiscible phases occurs. Each phase contains both polymers, but in the denser and more concentrated phase (lower layer), PVA is the prevailing component. The mutual influence of the two polymers causes changes in solute–solvent interaction, that is, dehydration of the polymers' molecules. It is assumed that in the processes occurring in the system, preferential molecules of definite structure take part. The merits of a system using both polymers as dispersants in the vinyl chloride polymerization are discussed in the light of ascertained data. © 1993 John Wiley & Sons, Inc.
Heat‐resistant thermosetting polyimide matrix resins containing keto, ether, hexafluoroisopropylidene linkages and maleimido‐ and nadimido‐ end capped groups
Authors: Kumar Devendra , Kaur Jasmeet , Gupta Alka D.
Published: April 2003

Various heat‐resistant thermosetting polyimides containing hexafluoroisopropylidene and keto and ether groups suitable for fiber‐reinforced composites development have been synthesised by thermal polymerization of maleimido and nadimido end capped polymer precursors. Thermal polymerization involving addition reactions was performed at 225°C for 1.5 h and post‐curing at 290°C for 0.5 h. Tough polymers XVIII to XXIII were obtained. The thermal polymerization was monitored using infrared spectroscopy. The polymer precursors were characterized by IR,1H‐NMR, and elemental analysis. The synthesized polymers were evaluated for thermal stability using dynamic thermogravimetric analysis (TGA). All the polymers showed thermal decomposition temperatures in the range of 430–435°C in nitrogen and in air. The char yield of the polymers was in the range of 60–67% in nitrogen at 800°C. This study indicated that thermally synthesized polymers from hexafluoroisopropylidene, keto, and ether containing polymides are potential candidates for the development of advanced materials for aerospace and high‐tech applications. © 1993 John Wiley & Sons, Inc.
Preparation and characterization of electropolymerized poly(N‐substituted maleimide‐co‐styrene) coatings on copper substrates
Authors: Liang Jeng‐Li , Bell James P. , Iroh J. O. , Mehta Ashit
Published: April 2003

poly(N‐substituted maleimide‐co‐styrene) copolymer films were electropolymerized onto copper substrates as possible candidates for electronic applications. The N‐substituted moieties that were investigated include phenyi, 3‐carboxyphenyl, and 4‐carboxyphenyl. Uniform coatings of 25 μm or more thickness were successfully applied using each of the three N‐substituted maleimides. The thickness was controlled by manipulating the monomer concentration, current density, and reaction time. Not only did the 3‐ and 4‐carboxyphenylmaleimide (CMI)/styrene copolymers have high glass transition temperatures (220°C) and fairly good thermal stability (≈ 430°C), but they also have rather low dielectric constants (2.55 for 4‐CMI/styrene), comparable to those of polyimides. Polymerization of the coatings was observed by in‐situ Fourier transform infrared spectroscopy (FTIRS), using a special cell that made the observation of the polymer structure development possible. It was found by FTIRS that all three monomers, when used with styrene, produced alternating copolymers. © 1993 John Wiley & Sons, Inc.
Dynamic mechanical properties of polyurethane grafted onto styrene–styrene sulfonic acid copolymers
Authors: Rutkowska Maria , Jastrzebska Mariola , Kim Joon‐Seop , Eisenberg Adi
Published: April 2003

The object of this study was the exploration of the dynamic mechanical properties and thereby also of the phase behavior of partly sulfonated polystyrenes containing polyurethane grafts. The synthesis was accomplished by stepwise grafting onto the partly sulfonated polystyrene of N‐methyldiethanoloamine, via ionic interactions resulting from proton transfer followed by chain growth on the hydroxyl sites of the polyurethane structures. NMR spectra confirmed that the protons of the sulfonic acid groups had been transferred exclusively to the tertiary nitrogen of the N‐methyldiethanoloamine. If the grafts consist of only hard segments, then a single glass‐transition temperature is observed that depends on the length of attached hard segment. If, on the other hand, soft segments are also included in the grafts, then these phase‐separate and yield a new glass‐transition temperature. For the phase‐separated systems, the grafts yield a low Tg phase of higher purity than blending of sulfonated polystyrene with the preformed polyurethane of the same composition. © 1993 John Wiley & Sons, Inc.
Dynamic mechanical studies of a highly filled composite structure: A lightweight coated paper
Authors: Hagen Roger , Salmén Lennart , De Ruvo Alf
Published: April 2003

A composite sandwich structure, consisting of a paper sheet as a middle layer and two porous coating layers of a highly filled acrylate–styrene–butadiene copolymer, has been studied by means of a dynamic mechanical test in torsion. Stiffness and mechanical damping, tan δ, were recorded over the temperature region where the latex polymer exhibits a glass transition. The mechanical damping decreases with increasing filler content in the coating. Variations in the thickness of the coating layers did not influence the mechanical damping. The glass transition temperature of the latex polymer increases with increasing volume fraction of filler at high filler contents as an effect of filler–matrix interaction. The outer layers partly penetrate into the middle layer, as indicated by thickness measurements on the coated paper. A theoretical comparison of the peak heights of the mechanical damping using lamination theory shows a discrepancy in the experimental results. If penetration of the outer layer is allowed for, i.e., if using a thicker outer layer of the composite in the calculations, a favorable correlation between the theoretical and the experimental results is obtained. © 1993 John Wiley & Sons, Inc.
Silane cross‐linking of PVC. II. Influence of silane type and conditions on cross‐linking by water
Authors: Kelnar I. , Schätz M.
Published: April 2003

The cross‐linking of plasticized and unplasticized poly(vinyl chloride) (PVC) grafted with amino‐ and mercaptoalkyltrialkoxysilanes has been studied in water and in air at 20–140°C. In both media, the cross‐linking occurs faster for plasticized PVC grafted with aminosilanes; however, at temperatures above 100°C, the effect of degradation cross‐linking is apparent. For mercaptosilanes, a marked dependence of the cross‐linking rate on the silane structure was found; plasticized PVC with grafted 3‐mercaptopropyltrimethoxysilane was cross‐linked in water at 100°C after 6 h, whereas this process took 12 h for 5‐mercaptopentyltriethoxysilane. Practically no cross‐linking occurred in unplasticized PVC below Tg, whereas the rate at 100°C was comparable with that for plasticized PVC. The cross‐linking rate is affected by the chain mobility, water content, and diffusion of water into the material; a very slight dependence on the thickness of the material was found for plasticized PVC. © 1993 John Wiley & Sons, Inc.
The acetylation and enzymatic degradation of starch films
Authors: Parandoosh Shohreh , Hudson Samuel M.
Published: April 2003

The preparation of films from starch and their degradation by amylase enzymes is described. Starch acetate was prepared by acetylation of starch with a pyridine/acetic anhydride mixture. The resulting polymer was cast into films from solutions of 90% formic acid. A series of films with a range of acetyl content were then exposed to buffered amylase solutions and the retained tensile strength measured. It was found that with a sufficient acetyl content the wet strength of the films was maintained in the aqueous solutions, but that the acetyl content was sufficiently low enough to permit degradation by a mixture of alpha and beta amylases within a period of 1 h. These films could be useful as membranes in bioreactors, which could be degraded at will by the addition of enzymes to the system. © 1993 John Wiley & Sons, Inc.
Morphology‐property relationship of segmented polyurethaneurea: Influences of soft‐segment structure and molecular weight
Authors: Xiu Yuying , Wang Dening , Hu Chunpu , Ying Shengkang , Li Junxian
Published: April 2003

The relationships of the morphology and properties of a series of segmented polyurethaneurea (PUU) were studied in film form by using SEM and tensile stress‐strain data. The polyether‐based and polyester‐based PUU block copolymers were synthesized using poly(propylene oxide) ‐ethylene oxide polyether or poly(butylene adipate) polyester with different molecular weights, 4,4‐methylene bis(phenyl isocyanate), and diethyltoluene diamine. The extent of phase separation increased with increasing molecular weight of the soft segment. The polyether‐based PUU showed better phase separation than did polyesterbased PUU with the same molecular weight soft segment. The polyether‐ester‐based PUU showed the morphology of both polyether‐based and polyester‐based PUU but with larger domain size and interface. © 1993 John Wiley & Sons, Inc.
Melt blends of SAN with SAN‐graft‐polybutadiene (PB)
Authors: Kim B. K. , Shin G. S.
Published: April 2003

Melt blends of SAN with SAN‐graft‐polybutadiene (PB) (g‐ABS) were prepared in a Brabender plasticorder. The effect of g‐ABS on the morphology and mechanical and viscoelastic properties of the blends was studied up to 60 wt % g‐ABS. The brittle‐tough (BT) transition occurred around 20 wt % g‐ABS, and the viscosity increased monotonically with g‐ABS, showing yield behavior at ≥ 20%. The lower and higher glass transition temperatures (Tg) of g‐ABS, each corresponding to the Tg of PB and grafted SAN, decreased and increased with the addition of free SAN, and this was interpreted in terms of graft SAN—PB phase separation. © 1993 John Wiley & Sons, Inc.
Semi‐interpenetrating polymer networks composed of poly(ethylene terephthalate) and vernonia oil
Authors: Barrett L. W. , Shaffer O. L. , Sperling L. H.
Published: April 2003

Semi‐interpenetrating networks have been synthesized from vernonia oil‐sebacic acid polyester network and poly(ethylene terephthalate) (PET). Bond interchange reactions during mixing of the two materials led to the formation of a miscible copolymer mixture, in which the vernonia oil was then cross‐linked with sebacic acid. The materials were phase‐separated, exhibiting two glass transitions, when the network was synthesized at 160°C, below the crystallization temperature of PET: however, a single stable glass transition (Tg) results after the material is heated to above the melting temperature of PET and cooled. When the vernonia polyester network was completely formed at 250°C, above the crystallization temperature of PET, noncrystalline, single‐Tg material was created. The two‐phase semi‐IPNs were much tougher than were their constituent materials, with the 50% semi‐IPN over 15 times tougher than the PET from which it was made and over 50 times tougher than the neat vernonia oil elastomer, with tensile energy to break of 1780 kJ/m3. The single‐Tg material was nearly 2.5 times as tough as the two‐phase material, with energy to break of 4400 kJ/m3. The microstructure of the two‐phase 50% semi‐IPN was investigated by transmission electron microscopy, which showed regularly shaped spherulites of 10–20 μm in diameter, as compared to irregularly shaped spherulites observed in a similar 50/50 castor oil urethane/PET semi‐IPN, in which the network formed simultaneously with PET crystallization. Scanning electron microscopy of the semi‐IPN fracture surfaces showed microscopic fibrils several hundred nanometers in diameter in both the two‐phase and single‐Tg materials, although only the two‐phase semi‐IPN had a macroscopically rough surface. © 1993 John Wiley & Sons, Inc.
Study of the effect of annealing, draw ratio, and moisture upon the crystallinity of native and commercial gutta percha (transpolyisoprene) with DSC, DMTA, and X‐rays: Determination of the activation energies at Tg
Authors: Arvanitoyannis Ioannis , Kolokuris Ioannis , Blanshard John M. V. , Robinson Colin
Published: April 2003

The transitions occurring in gutta‐percha (transpolyisoprene) below the melting point were determined with DMTA and DSC. A comparison of the results obtained with these two methods showed satisfactory agreement. The thermal properties of native and commercial gutta‐percha samples (Tg = 38 ± 2°C and Tm = 69 ± 3°C) were investigated, both before and after annealing (at different times and temperatures), and at environments of different relative humidities. An increase in the draw ratio also proved to enhance the percentage crystallinity (% K) and improve the thermal stability (higher Tgs and Tms) of gutta‐percha. Finally, the activation energies ΔE (33.9–40.2 kj/mol × K) at glass transition temperature were determined and correlated to the percentage content (%) of the commercial gutta‐percha samples in native gutta‐percha. © 1993 John Wiley & Sons, Inc.
Synthesis and microbial degradation of poly(2‐methyl phenylene oxide)
Authors: Li Li‐Xia , Grulke Eric A. , Oriel Patrick J.
Published: April 2003

The synthesis and biodegradation of poly(2‐methyl phenylene oxide) was studied as an example of a synthetic polymer containing a biodegradable aromatic backbone. Polymer prepared with cuprous 2,2‐isopropoxy ethyl pyridine catalyst demonstrated good blending properties with polystyrene. In soil experiments, the homopolymer degraded readily with over 50% reduction in 40 days. No. oligomeric intermediates were observed by gel permeation chromatography, suggesting degradation by cell‐associated enzymes. © 1993 John Wiley & Sons, Inc.
Fractionation of a statistical copolymer in a demixing‐solvent system: Theory and experiment
Authors: Podešva Jiří , Stejskal Jaroslav , Prochǎzka Ondřej , Špaček Pavel , Enders Sabine
Published: April 2003

It has been shown that, under specific conditions, a demixing‐solvent fractionation according to chemical composition can be applied to statistical copolymers. Formally, identical expressions have been derived for the distribution of a copolymer between coexisting phases in precipitation (sol‐gel) and demixing‐solvent fractionations. Theory predicts that the effects of molar mass and chemical composition cannot be separated in either of the phaseequilibrium fractionations. With demixing solvents, the partition coefficient depends steeply on copolymer composition, which enables one, e.g., to separate homopolymers from a blend. Multistep demixing‐solvent fractionation of a copolymer may proceed only in specific cases, e.g., immediately below the maximum of the coexistence curve. A feasibility study was performed with a chemically heterogeneous statistical copolymer of styrene and 2‐methoxyethyl methacrylate; the experimental results have confirmed the theoretical predictions. © 1993 John Wiley & Sons, Inc.
Synthesis and characterization of metal‐containing coordination polymers of poly(methylene diphenylene terephthalamide)
Authors: Bajpai U. D. N. , Rai Sandeep , Bajpai Anjali
Published: April 2003

Amino group‐terminated poly(methylene diphenylene terephthalamide) (PMDTA) was prepared using a phosphorylation technique that was then converted into Schiff's base coordination polymers by their reaction with Co(II), Ni(II), and Cu(II) complexes of salicylaldehyde [M(SAL)2] and 2‐hydroxy‐1‐naphthaldehyde [M (NAPTHAL)2]. The resulting coordination polymers were characterized by IR, elemental analysis, magnetic susceptibility measurements, and thermogravimetric analysis (TGA). TGA shows that coordination polymers are more thermally stable than is the ligand under similar conditions. On the basis of observed results, an oxygen‐and nitrogen‐coordinated structure for polyar‐amid‐metal complexes has been proposed. © 1993 John Wiley & Sons, Inc.
The influence of the equilibrium melting temperature on the supermolecular morphology of several polymers
Authors: Murphy C. J. , Fay J. J. , Vail E. A. M. , Sperling L. H.
Published: April 2003

At a constant isothermal crystallization temperature (Tc), the crystalline morphologies of several polymers have been found to be a function of the melt‐liquid temperature (T1). At a constant Tc below a critical crystallization temperature (T [about 0.9 T(K)], a transition from a nonspherulitic to a spherulitic morphology occurs when the melt liquid is heated above a melt‐liquid transition temperature, (Tlt) [approximately 1.03 Tm (K)], where Tm is the observed melting temperature of the sample. The melt‐liquid transition temperature, Tlt, which experimentally affects the visible morphology of a semicrystalline polymer, is apparently indistinguishable from the thermodynamic melting temperature, T, determined by the Hoffman‐Weeks procedure. The X‐ray powder diffraction patterns of spherulitic and nonspherulitic morphologies were identical, independent of the heating‐cooling cycle. This suggests that the transition that occurs at TIt does not affect the arrangement of polymer molecules in the crystallite, but only the manner in which the crystallites are arranged in the supermolecular morphology. The evidence suggests, at least for the polymers studied, that a residual order exists in the melt until the T or TIt of the particular polymer is reached. © 1993 John Wiley & Sons, Inc.
The effect of plasticization and pH on film formation of acrylic latexes
Authors: Eckersley S. T. , Rudin A.
Published: April 2003

The effect of several variables relevant to film formation in 49 : 49 : 2 poly(methyl methacrylate‐co‐butyl acrylate‐co‐methacrylic acid) latexes were studied.

Plasticization of the terpolymer by both an anionic [sodium dodecyl benzene sulphonate (NaDBS)] and a nonionic [nonyl phenol ethylene oxide adduct (NP40), forty ethylene oxide units on average] surfactant were investigated. Dynamic mechanical measurements indicated that NP40 plasticized the polymer, whereas NaDBS did not. This was attributed to the compatibility of the nonionic emulsifier and the polymer. The influence of the surfactants on the film formation process was studied using minimum film temperature (MFT) measurements and scanning electron microscopy (SEM). As expected, the MFT was independent of NaDBS concentration. However, the MFT was also independent of NP40 concentration. Film formation was further investigated using SEM. The series of micrographs at varying NaDBS concentrations showed no effect on the degree of film fusion. However, surface exudates were observed. The micrographs revealed that increasing NP40 content resulted in an apparently greater degree of film coalescence. That is, there was bridging of the particles in the interstitial regions. This was attributed to localized plasticization of the polymer in these regions by NP40.

The effect of water plasticization of the latex polymer was studied using dynamic mechanical measurements. The physical character of the terpolymer was varied using mol wt modifiers (CBr4 chain transfer agent and ethylene glycol dimethacrylate crosslinker). It was found that all of the polymers were plasticized by water.

Finally, the film forming behavior was investigated as a function of latex pH. MFT measurements indicated an independence of pH. © 1993 John Wiley & Sons, Inc.
Deformation behavior of poly(dimethyl siloxane) networks. I. Applicability of various theories to modulus prediction
Authors: Venkatraman S.
Published: April 2003

The shear moduli of end‐linked poly(dimethyl siloxane) networks were measured as a function of mol wt between chemical crosslinks (Mc) and the dilution‐at‐cure (Cx). The results were interpreted in terms of theories that take into account contributions from trapped entanglements. It was found that the network deformation follows the predictions of the theory of “phantom” networks, with an added contribution from trapped entanglements. At high mol wts of the precursor polymer, network imperfections play a role, as seen in the frequency dependence of the shear modulus. This results in deviation from predicted behavior. © 1993 John Wiley & Sons, Inc.
Determination of the elastic component for polymeric melt under steady shear flow
Authors: Pham H. T. , Bosnyak C. P. , Wilchester J. W. , Christenson C. P.
Published: April 2003

Steady state shear flow in rectilinear coordinates can be generated by a direct shear rheometer. The rheological behavior of polymeric melts under shear flow can be characterized by the inception of steady shear flow and stress relaxation after cessation of steady shear flow. Experiments were performed for bisphenol A polycarbonate with various mol wts. The elastic components, such as the primary normal stress differences and the elastic recoverable shear strain of the polymeric melts, can be determined from the shear moduli. © 1993 John Wiley & Sons, Inc.
Preparation and characterization of membranes with positively charged main chain from polyethylenimine
Authors: Nagaya Jiro , Tanioka Akihiko , Miyasaka Keizo
Published: April 2003

A membrane, which has positively charged groups in the polymer main chain, was prepared from polyethylenimine by crosslinking and successive alkylation. Dibromoalkane was used as a crosslinking agent. The crosslinked membrane was alkylated using methyl iodide under several conditions. Elemental and ICP emission analyses were introduced to measure the rates of alkylation and quaternization. From the membrane potential measurement, the effective charge density was estimated. The highest value was about 1.0 M, which was obtained by a prolonged alkylation time. This value was larger than that of some commercial ion exchange membranes. The effective charge density, which was obtained by the last alkylation procedure, was 10 times larger than that of the former one, though the rate of quaternizing increased by less than a factor of two. This implies that the activity constant in the membrane increased when the charge density is increased. © 1993 John Wiley & Sons, Inc.
Enhancement of the metal‐binding properties of chitosan through synthetic addition of sulfur‐ and nitrogen‐containing compounds
Authors: Lasko C. L. , Pesic B. M. , Oliver D. J.
Published: April 2003

Several new chitosan derivatives were synthesized with the intent of forming polymers that could be used in hazardous waste remediation as toxic metal‐binding agents in aqueous environments. The ability of these derivatives to bind Cu2+, Pb2+, Cd2+, and Fe2+ was tested and compared to chitosan. Four of the new compounds, the products of the reaction of chitosan with mercaptosuccinic acid, thiirane, pyridoxal hydrochloride, and succinamide, show promising results as binding agents for the above metal ions. The compound with mercaptosuccinic acid bound twice as much Cd2+, five times as much Pb2+, and virtually no Fe2+ when compared to chitosan. The compound with thiirane bound three times as much Pb2+, whereas the pyridoxal hydrochloride derivative bound 30% more Cu2+ and twice the Pb2+. The succinamide derivative gave results comparable to chitosan, but with decreased solubility at low pH. © 1993 John Wiley & Sons, Inc.
Characterization of grafted polyethylene by contact‐angle hysteresis and ESCA studies
Authors: Konar J. , Sen A. K. , Bhowmick A. K.
Published: April 2003

Low‐density polyethylene (LDPE) has been functionalized in the bulk through dicumyl peroxide (DCP)‐initiated grafting of dibutyl maleate (DBM) and vinyltrimethoxysilane (VTMO) in the temperature range from 140 to 200°C. The functionalized surfaces have been characterized through contact angle and contact‐angle hysteresis measurements as well as through ESCA studies. The degree of grafting has been determined by infrared spectrophotometry. From the ESCA patterns of the modified polymers, the atomic ratios of oxygen to carbon and silicon to carbon have been calculated. Determination of an empirical relation between contact‐angle hysteresis and the oxygen‐carbon ratio of the functionalized polymer surfaces has been attempted. It is found that the higher the oxygen‐carbon ratio, the lower the contact‐angle value for polyethylene. Contact angle‐hysteresis increases with increase of the degree of grafting. The total surface energy increases with grafting. The surface energy of the silane‐grafted polyethylene (PEgS) is found to be the lower than that of dibutyl maleate‐grafted polyethylene (PEgDBM). © 1993 John Wiley & Sons, Inc.
Morphology‐property relationships in oriented PET films: A role of in‐plane crystalline orientation distribution on the film properties
Authors: Gohil Ramesh M.
Published: April 2003

The role of in‐plane crystalline, amorphous, and overall molecular orientation on various properties in the plane of the films was investigated using a variety of techniques. It is shown that for a fixed value of crystallinity the in‐plane crystalline orientation and the nature of the constraint imposed by the crystallites on the molecules play an important role in obtaining isotropic in‐plane expansion or shrinkage properties. Achievement of in‐plane isotropic tensile strength and elongation at the break are found to depend entirely upon an isotropic distribution of the amorphous orientation; the orientation of crystallites plays no detectable role. Furthermore, the deformation mechanisms of sequential and simultaneous biaxial stretching processes have been investigated and compared. The simulteneous stretching process is considered to be a more controlled film‐fabricating method compared to sequential stretching in achieving balanced, in‐plane film properties. © 1993 John Wiley & Sons, Inc.
High speed tensile performance and fractography of acrylic latex films
Authors: Eckersley Sarah T. , Plumtree Alan , Rudin Alfred
Published: April 2003

The performance of acrylic (50:50 MMA/BuA) latexes was investigated as a function of fusion level using high speed tensile testing. The structure of the copolymer was varied via the addition of molecular weight modifiers to the emulsion polymerizations. Chain transfer agent (CBr4) was used to reduce the copolymer modulus, and crosslinker (EGDM, ethylene glycol dimethacrylate) was added to increase the modulus. The resulting materials exhibited a wide range of viscoelastic behavior (G* varied from ∼ 107 dyne cm−2 to ∼ 109 dyne cm−2). Fracture energy and peak force at break were measured as a function of the complex modulus. It was found that both of these parameters showed a maximum with respect to G* that corresponded to intermediate levels of crosslinking. This observation was explained in terms of the degree of coalescence of the films. Fully fused films (excess CBr4) were brittle and performed poorly, conceivably because of insufficient entanglement to support stress. Marginally fused films also exhibited inferior, brittle behavior. The films cast from latexes synthesized with low levels of molecular weight modifiers showed intermediate fusion levels and superior tensile performance. The quantitative results were rationalized using scanning electron microscopy (SEM) of both the virgin films and the fracture surfaces. For comparison, the same materials were tested in a fully fused state following hot pressing. The behavior paralleled that expected for vulcanized rubbers in which lightly crosslinked materials exhibit the highest tensile strength. © 1993 John Wiley & Sons, Inc.