bluuebunny/crossref_metadata_2025 huggingface dataset:
Decrease in fluorescence and phosphorescence intensity of nylon 66 impurities by exposure to ultraviolet radiation
Authors: Brasington Chandis R. , Gadala‐Maria F.
Published: April 2003

The effects of exposure to ultraviolet radiation on the fluorescence and phosphorescence intensity of impurities in nylon 66, sometimes called gel, were measured using color image processing. The fluorescence intensity of the gel particles and of the polymer showed an approximately exponential decay with the time of exposure to ultraviolet radiation, with decay constants in the range 0.5 to 1.0 h−1. Analysis of images that were acquired over several hours also indicated a decrease in the phosphorescence intensity of the gel particles. Image processing provides a simpler and less expensive method of luminescence analysis than the spectroscopic techniques used previously to examine the effects of exposure to ultraviolet radiation on the phosphorescence properties of nylon 66 impurities. © 1995 John Wiley & Sons, Inc.
Flow properties of thermally depolymerized liquid natural rubber
Authors: Nair N. Radhakrishnan , Claramma N. M. , Mathew N. M. , Thomas Sabu , Rao S. Someswara
Published: April 2003

The flow behavior of liquid natural rubber (LNR) with reference to the effect of molecular weight, shear rate, and temperature has been studied. LNR samples were prepared by thermal depolymerization of rubber (NR) through the combined effect of mechanical, chemical, and thermal energies. High molecular weight samples, especially at lower temperatures, showed pseudoplastic behavior, whereas the low molecular weight samples were Newtonian at all temperatures. The viscosity of LNR considerably decreases with increase in temperature. The activation energy of flow was also calculated. © 1995 John Wiley & Sons, Inc.
Studies on the synthesis and properties of soluble homo‐ and copolyester–imide derived from imide–diacid
Authors: Li Chien‐Hui , Chen Chih‐Chiang , Chen Ker‐Ming , Chang Teh‐Chen
Published: April 2003

A series of polyester–imides was prepared from diacid (imid–diacid [M1–M4] or a mixture of imide–diacid and terephthalic acid [TPA]) and bisphenol A in the presence of diphenyl chlorophosphate (DPCP) and pyridine as a direct condensation agent. The inherent viscosites of homo‐ and copolyester–imides were in the range of 0.39–0.58 dL/g. Almost all these homo‐ and copolyester–imides were completely soluble in N‐methyl‐2‐pyrrolidone (NMP), N,N‐dimethylacetamide (DMAC), dimethylformamide (DMF), and m‐cresol. The thermal properties of homo‐ and copolyester–imides were examined by DSC and TGA. These copolyester–imides had glass transition temperatures in the range of 95–240°C and a 5% weight loss was observed in the range of 354–465°C. © 1995 John Wiley & Sons, Inc.
Settling characteristics of microparticles modified by hydrophilic semi‐interpenetrating polymer networks
Authors: Degrazia Janet L. , Bowman Christopher N.
Published: April 2003

Microparticles of 2‐hydroxyethyl methacrylate cross‐linked with ethylene glycol dimethacrylate were produced by suspension polymerization. Semi‐interpenetrating polymer networks were prepared by diffusion of poly(ethylene oxide) (PEO) solution into the particles. The PEO was allowed to diffuse into the dried particles and the resulting swollen particles were treated with an excess of acetone to collapse them. The ensuing networks consisted of the collapsed particles and the trapped PEO. The modified particles were allowed to settle in water, and characteristic settling times were measured as a function of swelling time. The settling times were compared to those of the unmodified particles. It was found that the settling time changes with volume fraction, particle size, degree of functionality, and amount of swelling. An increased volume fraction in both unmodified and modified particles causes a slower settling rate. The smaller particle sizes fall more slowly, and size difference plays a more significant role in hindering the settling for lower amounts of trapped PEO. As the amount of PEO increases, the settling rate decreases dramatically. Swelling also slows the settling rate, until the particles reach equilibrium. Equilibrium swelling occurs near 10 min for both unmodified and modified particles. Optical photo‐microscopy verified the amount of swelling and demonstrated the process of PEO penetration. © 1995 John Wiley & Sons, Inc.
Synthesis and characterization of block copolymers from D,L‐lactide and poly(tetramethylene ether glycol)
Authors: Xiong C. D. , Cheng L. M. , Xu R. P. , Deng X. M.
Published: April 2003

The copolymer from D,L‐lactide and poly(tetramethyene ether glycol) (PTMG) was prepared in bulk with an isotributyl aluminum–water–phosphoric acid complex catalyst as the initiator and characterized by H‐NMR, GPC, and DSC. The effects of the temperature and the amount of PTMG on the polymerization rate and the molecular weight of copolymers were studied. The behavior of the degradation and delivery rate of Levonorgestrel microspheres in vitro was observed. The results show that the degradation and the delivery rate can be controlled by adjusting the molar rate of hydrophilic and hydrophobic segments of the copolymer © 1995 John Wiley & Sons, Inc.
Study of miscibility of poly(vinyl acetate) and poly(vinyl alcohol) blends by fluorescence spectroscopy
Authors: Dibbern‐Brunelli D. , Atvars T. D. Z.
Published: April 2003

Secondary relaxation of poly(vinyl alcohol) (PVA), poly(vinyl acetate) (PVAc), and their blends in different proportions (9 : 1, 1 : 1, and 1 : 9) were studied by photoluminescence of anthracene, fluorescein, and both probes dissolved in the polymer blends. The temperature of the glass transition in the homopolymers was determined by the radiationless deactivation of anthracene as Tg(PVAc) ≅ 304 K and the photobleaching of fluorescein as Tg(PVA) ≅ 350 K. The relaxation processes of the different phases of the polymer blends occur at temperatures close to the homopolymers, which may be explained by the localization of each molecular probe within the matrix. These deactivation curves, however, are not similar to those of the individual homopolymers, suggesting a partial miscibility between these polymers. © 1995 John Wiley & Sons, Inc.
Optimal temperature for the control of the product quality in batch polymerization: Simulation and experimental results
Authors: Scali Claudio , Ciari Roberto , Bello Tiziana , Maschio Giuseppe
Published: April 2003

A method to determine an optimal temperature profile that guarantees products having controlled molecular weight distribution (MWD) and desired values of molecular weight (Mw) is presented. The base case is the batch polymerization of MethylMethAcrylate, initiated by AIBN. On the basis of the kinetic model, the optimal temperature profile is determined by imposing that the value of the instantaneous chain length is maintained constant, thus counteracting the effects of the increase of viscosity, which leads to broad MWD. Some approximations permit to express, in a straightforward way, the relationship between the optimal temperature and the conversion as a function of the initial conditions. The validity of the simplifying hypotheses that have been assumed is confirmed first by simulation results and then by a comparison with experimental runs conducted in a labscale unit, with determination of MWD made by means of GPC. The obtained results suggest that it is possible to decouple the problem: acting on the operating temperature to control the MWD, acting on initial temperature and initiator concentration to influence the Mw. The possibility of application to industrial reactors has also been investigated, taking into account their peculiarities and constraints. © 1995 John Wiley & Sons, Inc.
Transcrystalline growth of thermoplastics and LCPs during isothermal crystallization
Authors: Huang Y. , Petermann J.
Published: April 2003

Two technical methods were developed for transcrystalline growth in order to create perfect transcrystalline growth for both thermoplastics and liquid crystalline polymers. A principle was suggested for oriented crystallization that the nucleation is created with high density along a one‐dimensional or on a two‐dimensional unit, while the nucleation in the matrix is suppressed. The steric hindrance was a key factor to create the transcrystalline growth in isothermal crystallization. © 1995 John Wiley & Sons, Inc.
Fractionation of reactive perfluoropolyoxyalkylene oligomers
Authors: Levi Marinella , Turri Stefano
Published: April 2003

Fractional distillation, solubility fractionation, and column chromatographic separation have been applied in the study of fractionation of perfluoropoly(oxymethylene‐co‐oxy‐ethylene) oligomers with CH2OH end units, containing mono and bifunctional species. With a suitable choice of conditions, all three techniques proved to be useful for the preparation of fractions with narrow molecular weight distribution. Column chromatography allowed the separation of fractions having, in addition, sharp mono and bifunctionality. On the bsis of the experimental results, general indications for designing reactive oligomers fractionation procedures are discussed, prevalently centered on the copolymer end effect, which is typically present in this kind of compound. © 1995 John Wiley & Sons. Inc.
An extension of the penalty function formulation to incompressible hyperelastic solids described by general measure of strain
Authors: Kakavas P. A. , Chang W. V.
Published: April 2003

The penalty function formulation for incompressible hyperelastic solids was first proposed about 30 years ago. Since then all studies have been limited to invariant type formulation of the strain energy function, although it is well known that this formulation does not correctly describe the behavior of a real material. On the other hand more realistic constitutive equations, based on general measures of the strain only, have been incorporated to mixed finite element algorithms. In this article, a penalty function formulation is proposed for the analysis of stress field in materials with constitutive equations based on the general measure of strain. The reduced integration method is used to weaken the penalty constraint in order to obtain meaningful numerical results. The incremental equilibrium equations are solved using the regular Newton–Raphson algorithm. The method is applied to evaluate the stress field in materials subjected to plane strain conditions. Satisfactory agreements have been obtained with analytical solutions when available. © 1995 John Wiley & Sons, Inc.
Preparation and characterization of negative photosensitive polysiloxaneimide
Authors: Zhu Pukun , Li Zuobang , Feng Wei , Wang Qiang , Wang Lixin
Published: April 2003

A photosensitive polysiloxaneimide precursor was synthesized from oxydianiline, bis(p‐aminophenoxy)dimethylsilane, and a diacid chloride. This diacid chloride was prepared by the reaction of thionyl chloride with a diacid, which resulted from the reaction of pyromellitic dianhydride with hydroxyethylacrylate in N‐methylpyrrolidone (NMP). The adhesion properties between polyimide and substrates such as SiO2 wafer were improved with introduction of siloxane moiety into the polyimide chain. The dielectric constant decreased with increasing siloxane moiety content. The photocrosslinking reaction results show that an 88–90% gel fraction was reached under the irradiation of a high‐pressure mercury lamp. © 1995 John Wiley & Sons, Inc.
Bilayer thin‐film composite membranes for air separation
Authors: Huang Mei‐Rong , Li Xin‐Gui , Chen Guan‐Wen
Published: April 2003

Bilayer composite membranes suitable for separating air, consisting of poly(4‐methylpentene‐1) (PMP) thin film as a selective top layer, an ethylcellulose–heptycellulose (ECHC) blend thin film as a selective sublayer, and polysulfone as a porous support, were investigated using a constant pressure–variable volume method. By varying operating temperature, pressure, time, as well as stage cut, the membranes were characterized for their oxygen enriched air (OEA) flux and oxygen concentration in the OEA permeated in a single step. The results show that both the OEA flux and oxygen concentration through the membranes increase with increasing operating pressure. With the increase of operating temperature, the OEA flux increases largely but the oxygen concentration decreases slightly. The oxygen concentration also decreases slightly with the stage cut. On the contrary, the OEA flux decreases and oxygen concentration increases slightly with operating time. It is found that a PMP thin film plays an important role in enhancing the air‐separation capability of the membrane. The PMP/ECHC bilayer thin‐film composite membrane could enrich the OEA containing 43.6% oxygen at the OEA flux of 5.06 × 10−4 cm3 (STP)/s cm2 with a good performance stability. © 1995 John Wiley & Sons, Inc.
New catalysts for poly(ethylene terephthalate)‐bisphenol a polycarbonate reactive blending
Authors: Fiorini Maurizio , Berti Corrado , Ignatov Vladimir , Toselli Maurizio , Pilati Francesco
Published: April 2003

The effects of various catalysts on the reactive blending of poly(ethylene terephthalate) (PET) and bisphenol A polycarbonate (PC) was investigated. The various catalysts employed for PET syntheses, Ti(OBu)4, SmL3, EuL3, Ca + Sb, CeAc3, Er(NO3)3·B12C4 and Tb (acac)3·diPy (where L is o‐formylphenolate; B12C4 is a crown ether, benzo‐12‐crown‐4; acac is acetylacetonate; and diPy is 2,2′‐dipyridyl) have shown a different catalytic activity toward exchange reactions. Solubility tests, in solvents able to separate unreacted PET and PC, and selective degradation of the PC segments, combined with 1H NMR spectroscopy and size exclusion chromatography, made it possible to order the catalysts according to their catalytic activity: Ti(OBu)4 ≫ SmL3 > EuL3 > Ca + Sb > CeAc3∼Er(NO3)·B12C4 > Tb (Acac)3·diPy ≈ 0. © 1995 John Wiley & Sons, Inc.
Study of nylon 6 and poly(propylene oxide) blends by thermal measurements and carbon‐13 NMR high resolution solid‐state
Authors: Tavares Maria Inês Bruno , Castro Washington P. , Costa Dilma A.
Published: April 2003

Samples of Nylon 6/poly(propylene oxide), with poly(propylene oxide) (PPO) content varying up to 35%, have been examined using thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and nuclear magnetic resonance (NMR) carbon‐13 at solid‐state. Carbon‐13 spectra were measured by cross‐polarization (CP), magic angle spinning (MAS), and high‐power hydrogen decoupling (HPHD). The variation contact time experiment and MAS technique were also determined. The data are discussed in terms of compatibility and plasticization of the samples. © 1995 John Wiley & Sons, Inc.
Structure and mechanical properties of the compositions of polyisocyanurate polymers with low molecular weight rubbers
Authors: Askadskii Andrei A. , Shvorak Alexander E. , Frenkel Tsylia M. , Babtschinitzer Tatyana M. , Bychko Capitolina A. , Kovriga Oleg V. , Pankratov Viatscheslav A. , Rajulu A. Varada
Published: April 2003

The structure and properties of the compositions of polyisocyanurates modified with low molecular weight rubber networks have been investigated by means of dynamical mechanical analysis (DMA), electron microscopy, and stress‐relaxation experiments. The network compositions consist of two different polymeric networks. The first component (macrodi‐isocyanate based on low molecular weight polybutadiene or copolymers of tetrahydrofuran and propylene oxide) has bulky cross‐linked points connected by short flexible chains. The second component (diphenylmethanediisocyanate) also has bulky cross‐linked points of the same structure, but the linear fragments between them in this case are very small and rigid. These compositions result in the formation of the heterophase system. As a result, transparent samples were prepared, which differ from the mechanical properties of both the glassy and rubbery polymers. These materials have a modulus of elasticity (from 103 to 10 MPa) that is usual for the transition zone between the glassy and rubbery states; nevertheless, these materials show elastic (and not viscoelastic) properties. For the materials investigated, the modulus is decreased not more than 10 times in the wide temperature interval from 200 to 500 K. A new state of the polymer, which differs from both the glassy and rubbery states, has been identified in the present case. © 1995 John Wiley & Sons, Inc.
Release of radioactive steroids from dried down hydrogels of polyurethane networks
Authors: Zulfiqar M. , Quddos A. , Zulfiqar S.
Published: April 2003

The polyurethane networks were based on poly(ethylene glycol) 6000 (PEG), crosslinked with 1,1,1‐tris(hydroxy methyl)ethane and with the stoichiometric equivalence of hexamethylene diisocyanate. Radioactive steroids were incorporated into cylindrical hydrogels over a wide range of compositions. The release profiles were drawn from dried down hydrogel of polyurethane networks. The scintillation counter was used for the release study of steroids after different intervals. In vivo, the loaded hydrogels were implanted into rats. The results for constant release studies were recorded. © 1995 John Wiley & Sons, Inc.
Molecular transport of alkanes through thermoplastic miscible blends of ethylene–propylene random copolymer and isotactic polypropylene
Authors: Aminabhavi Tejraj M. , Phayde Hemant T. S.
Published: April 2003

A new experimental protocol based on the measurements of sorption (S), desorption (D), resorption (RS), and redesorption (RD) has been used to study the molecular transport of aliphatic alkanes through the miscible blends of an ethylene–propylene random copolymer and an isotactic polypropylene over the temperature interval 25–70°C. Diffusion and activation parameters are evaluated and their dependencies on solvent size, shape, and nature are discussed. Estimated values of the molar mass between chain entanglements, kinetic rate constants, and overshoot index parameters have been influenced by the polymer–solvent interactions. The sorption–diffusion mechanism is found to be of anomalous type. © 1995 John Wiley & Sons, Inc.
In‐plane shearing stress–strain response of glass‐fiber‐reinforced composites as determined from four‐point bending tests
Authors: Sideridis E. , Kyriazi E.
Published: April 2003

In this article an experimental study to determine the longitudinal (or in‐plane) shearing stress–strain response of a unidirectional fiber‐reinforced composite material is presented. The test method used is the four‐point blending of a ±45° off‐axis glass‐fiber‐reinforced laminate. Although a laminate is used for the investigation of the shearing stress–strain response, it is shown that unidirectional shear properties can be found from the laminate test data following a procedure analogous to that used in previously. Also, the 45° off‐axis test of unidirectional composite in bending was carried out to obtain the in‐plane shear modulus and compare it with that obtained by the ±45° off‐axis method. Finally both values were compared with the theoretical value of the in‐plane shear modulus obtained from a theoretical formula where the concept of boundary interphase between fiber and matrix was introduced. © 1995 John Wiley & Sons, Inc.
Structure and mechanical properties of heterogeneous polymer blends
Authors: Kozlowski M.
Published: April 2003

Material response under uniaxial stress has been reported for heterogeneous systems: low density poly(ethylene)–poly(styrene). The ystems differed in a component ratio and in a content of the macromolecular modifier type compatibilizer. Tensile properties have been determined for the systems in a molten state (473 K) and below Tg as a function of elongation rate. The modifier which diminishes the interfacial tension is advantageous for mechanical properties of the system—both in the melt and the solid state. The differences in mechanical characteristics have been related to a specific phase structure of polymer systems. © 1995 John Wiley & Sons, Inc.
Adhesive properties of DGEBA–acid homopolymer and DGEBA–acid copolymer systems
Authors: Laref F. Heba , Mouzali M.
Published: April 2003

Adhesive properties of high molecular weight acid copolymers used as hardeners for a commercial epoxy resin are investigated. For comparative purposes, physical blends of poly(acrylic acid)–polystyrene are used as hardeners. Joints prepared from physical blends exhibit lower lap shear strength than do those prepared form synthesis products. The use of copolymers is more adequate. Thermodynamic work of adhesion using wettability criteria is explored to explain the differences. The apparent energies of rupture determined by lap shear tests are 103 higher than those of the thermodynamic work of adhesion. © 1995 John Wiley & Sons, Inc.
Monodisperse poly(butadiene/styrene) particles by dispersion polymerization
Authors: Hu R. , Dimonie V. L. , Sudol E. D. , El‐Aasser M. S.
Published: April 2003

Experimental conditions for preparing monodisperse, micron‐size poly(butadiene/styrene) particles by dispersion polymerization were investigated. After some initial recipe development, the following variables were fixed: butadiene/styrene weight ratio (90/10), dispersion medium (ethanol), polymeric stabilizer [poly(vinyl pyrrohdone), K‐30], costabilizer (sodium dioctyl sulfosuccinate), initiator (2,2′‐azobisisobutryonitrile), and polymerization temperature (70°C). The primary process variables investigated were the monomer/ethanol ratio (M/S), the rpm of the bottle polymerizer, and the amount of free space (FS) in the polymerization bottles. The particle size varied from 0.77 to 1.8 μm and was found to increase with increasing M/S and rpm, and decreasing FS. © 1995 John Wiley & Sons, Inc.
Synthesis and characterization of a new degradable thermoplastic elastomer based on 1,5‐dioxepan‐2‐one and ε‐caprolactone
Authors: Lofcren A. , Renstad R. , Albertsson A.‐C.
Published: April 2003

A new, highly elastomeric ABA triblock copolymer made from ω‐caprolactone (ε‐CL) and 1,5‐dioxepan‐2‐one (DXO) has been synthesized by sequential addition of the comonomers in THF or toluene solution initiated by aluminum isopropoxide. Careful purification of the comonomers was essential to obtain high conversion of the final amount of the added monomer. The optimal conditions were found to be polymerization in toluene solution at 25°C with the addition of 1 molar equivalent (with respect to initiator) of pyridine, which gives a slight increase in the rate of polymerization. Under these conditions, poly(ε‐CL‐b‐DXO‐b‐ε‐CL) triblock copolymers of high molecular weight (Mn > 105 g/mol) with a relatively narrow molecular weight distribution were obtained. Thermal analysis shows a melting peak at 51°C and a glass transition at ca. −38°C, corresponding to the PCL block crystalline phase and the PDXO amorphous region, respectively. The mechanical properties of these materials are highly elastic and can be varied by tailoring the block lengths of the corresponding comonomers. Tensile modulus, tensile strength at break, and elongation at break were found to be 20–30 MPa, 50 MPa, and ca. 1000%, respectively. © 1995 John Wiley & Sons, Inc.
Kinetic study on simultaneous interpenetrating polymer network formation of epoxy resin and unsaturated polyester
Authors: Lin Mu‐Shih , Chang Reui‐Je , Yang Timothy , Shih Yen‐Fong
Published: April 2003

Simultaneous interpenetrating polymer networks (SIN) based on diglycidyl ether of bisphenol‐A (DGEBA) and unsaturated polyester (UP) in weight ratios of 100/0, 50/50, and 0/100 were blended and cured simultaneously by using cumene hydroperoxide (CHP) and m‐xylenediamine (MXDA) as curing agents. A kinetic study during SIN formation was carried out at 43, 53, 58, and 64°C. Concentration changes for both epoxide and CC bond were monitored with Fourier transform infrared (FTIR). Rate expressions for epoxide polymerization were established with model reactions for phenyl glycidyl ether (PGE) and benzylamine in dichloroethane containing benzyl alcohol. Experimental results revealed that a lower cure rate constant for the CC bond during SIN formation was found, compared with pure UP network formation. A model of network interlock is proposed to account for this phenomenon. During simultaneous cure of DGEBA and UP, the network interlock should provide a sterically hindered environment, which subsequently retards cure rate for UP. On the other hand, epoxide cure during SIN formation indicates higher rate constants for both uncatalyzed and catalyzed reactions, compared with those of pure DGEBA cure. Presumably the catalytic effect of hydroxyl end groups in UP overcomes the effect of network interlock. Kinetic parameters were calculated and are discussed. © 1995 John Wiley & Sons, Inc.
Miscibility and complexation behavior of poly(cyanomethyl methacrylate) and poly(2‐cyanoethyl methacrylate) with tertiary amide polymers
Authors: Yeo Y. T. , Lee S. Y. , Goh S. H.
Published: April 2003

The miscibility and complexation behavior of poly(cyanomethyl methacrylate) (PCYMMA) and poly(2‐cyanoethyl methacrylate) (PCYEMA) with various tertiary amide polymers was studied. PCYMMA and PCYEMA form interpolymer complexes with poly(N‐methyl‐N‐vinylacetamide) (PMVAc) or poly(N‐vinyl‐2‐pyrrolidone) (PVP) in tetrahydrofuran (THF) solutions. PCYMMA also forms complexes with poly(N,N‐dimethylacrylamide) (PDMA) in THF solutions. However, PCYEMA does not form complexes with PDMA in THF solutions, but the THF‐cast blends are miscible over the entire composition range. Both PCYMMA and PCYEMA do not form complexes with poly(2‐ethyl‐2‐oxazoline) (PEOx) in THF solutions and are only miscible with PEOx when the blend contains greater than 60 wt % PCYMMA or 80 wt % PCYEMA. On the other hand, both PCYMMA and PCYEMA do not form complexes with PMVAc, PVP, or PDMA in N,N‐dimethylformamide (DMF) solutions. The compositions of the complexes consist of simple mole ratios of the component polymers, and the glass‐transition temperatures of the complexes are higher than those of the DMF‐cast blends of similar compositions. Fourier‐transform infrared spectroscopy provides further evidence on the miscibility behavior through changes in the amide carbonyl absorption bands of each tertiary amide polymer in the blends as well as in the cyano absorption band of PCYEMA. © 1995 John Wiley & Sons, Inc.
Deformation of rubber‐toughened polycarbonate: Microscale and nanoscale analysis of the damage zone
Authors: Cheng C. , Hiltner A. , Baer E. , Soskey P. R. , Mylonakis S. G.
Published: April 2003

Deformation of polycarbonate (PC) impact‐modified with a core–shell rubber (MBS) was examined at the microscale and nanoscale. The stress‐whitened zone (SWZ) that formed ahead of a semicircular notch was sectioned and examined in an optical microscope and transmission electron microscope. At the microscale, the texture of the SWZ consisted of fine shear lines that formed when cavitation of the rubber particles relieved triaxiality and enabled the PC matrix in the SWZ to deform in shear. Examination of thin sections from the SWZ in the transmission electron microscope revealed nanoscale deformation of the rubber particles. When the particle concentration was low (2%), only random cavitation of rubber particles was observed. At higher particle concentrations (5 and 10%), cooperative cavitation produced linear arrays of cavitated particles. The matrix ligaments between cavitated particles were strong enough that they did not fracture; higher strains were accommodated by particle cavitation and matrix extension in the regions separating the arrays. The cavitated arrays were also observed in the damage zone that accompanied the fracture surface of specimens impacted at −20°C. Cooperative cavitation may have implications for the impact strength of blends with higher concentrations of rubber particles. The possibility that particle–particle interactions facilitate cavitation and promote matrix shear deformation is especially relevant to low‐temperature impact strength. © 1995 John Wiley & Sons, Inc.
Some epoxidized polyurethane and polyester resins based on linseed oil
Authors: Motawie A. M. , Hassan E. A. , Manieh A. A. , Aboul‐Fetouh M. E. , El‐Din A. Fakhr
Published: April 2003

Linseed oil was epoxidizedin situwith perbenzoic or peracetic acid to produce epoxidized linseed oil (I). Effect of type and concentration of the peracid and the reaction time on the characteristics of the produced epoxidized oil were studied. Various epoxidized polyurethanes (II) with different NCO/OH ratios as well as epoxidized polyesters (III) were prepared from (I). The results obtained for the evaluation of resins (II) and (III) show promising applicability as petroleum pipeline coatings. © 1995 John Wiley & Sons, Inc.
pH responsive PAIAm‐g‐PIPA microspheres: Preparation and drug release
Authors: Li Xiongwei , Huang Yushu , Xiao Jing , Yan Changhong
Published: April 2003

Poly(N‐isopropylacrylamide) (PIPA) was synthesized by radical polymerization with 2,2′‐azobisisobutyronitrile (AIBN) as an initiator and 3‐mercaptopropionic acid (MPA) as a chain‐transfer reagent in methanol (MeOH) at 70°C for 7 h. The resultant PIPA was grafted to polyallylamine hydrochloride (PAIAm · HCI) by amide formation under the influence of water‐soluble carbodiimide 1‐ethyl‐3‐(3‐dimethylaminopropyl) carbodiimide hydrochloride (EDC). The graft polymer was made into microspheres (MS) by chemical crosslinking. The pH‐responsive drug release of the graft polymer microspheres was examined by releasing phenobarbital natrium (PN), which was carried on the microspheres by physical adsorption. A dynamic dialysis technique was used in the drug‐release experiment and the drug‐release‐rate constants reflecting the drug release characteristic of polymer microspheres were obtained by constituting a mathematical model. The results indicated that the homopolymer PAIAm microspheres and the copolymer PAIAm‐g‐PIPA microspheres are both pH responsive to release PN and that in the neutral pH condition the release rate is the slowest. © 1995 John Wiley & Sons, Inc.
Unsaturated para‐linked aromatic LC polyesters: Thermotropic and lyotropic systems
Authors: Skrifvars Mikael , Schmidt Hans‐Werner
Published: April 2003

Liquid‐crystalline thermosets (LCT) are a new class of materials which combine typical properties of LC polymers with those of conventional thermosets. This article reports on the development of a lyotropic LC thermoset (LLCT) in which the solvent is a vinyl monomer. Such an LLCT is expected to have several advantages compared to conventional unsaturated polyester resins. The synthesis and characterization of a variety of novel substituted para‐linked aromatic polyesters and copolyesters containing unsaturated fumaroyl units is presented. The thermal and liquid crystal properties were investigated. It is demonstrated that it is possible to prepare a lyotropic LC solution in styrene. These lyotropic solutions are capable of thermal crosslinking by the addition of a free‐radical initiator. © 1995 John Wiley & Sons, Inc.
Preparation of polypyrrole/polythiophene double layers by electrochemical polymerization of pyrrole in the presence of thiophene
Authors: Kojima Takakazu , Hayakawa Hitoshi , Tsuchiya Masahiro , Kai Yoshiki
Published: April 2003

Studies on electrochemical polymerization of pyrrole in the presence of thiophene are given for preparation of polypyrrole (PPy)/polythiophene (PTh) double layers. At a constant current, only pyrrole is electrochemically polymerized in the electrolytic solution containing pyrrole and thiophene in the present experiments. The cyclic voltammograms on pyrrole/thiophene mixtures are similar to that on pyrrole. Preparation of PPy/PTh double layers is carried out by electrochemical polymerization of pyrrole in the presence of thiophene by adding pyrrole and by lowering voltage immediately after electrochemical homopolymerization of thiophene. The resulting double layers show good rectification characters dependent on thickness. © 1995 John Wiley & Sons, Inc.
Studies on a novel polymeric coupling agent: 3‐glycidoxypropyltrimethoxysilane‐modified polycarbonate
Authors: Huang Ying , Yu Yunzhao , Bell James P.
Published: April 2003

A Novel polymeric coupling agent was synthesized through the reaction of polycarbonate (PC) and 3‐glycidoxypropyltrimethoxysilane (GPS) in the presence of a quaternary ammonium salt. The reaction in the solid state gave a GPS‐modified PC, which had a bimodel molecular weight distribution. The solutions of the GPS‐modified PC were effective primers for promoting the adhesion of a siliceous abrasion‐resistant coating to the PC substrate. © 1995 John Wiley & Sons, Inc.
Preparation of epoxy hardeners from waste rigid polyurethane foam and their application
Authors: Xue Shuchang , Omoto Mitsuru , Hidai Takao , Imai Yoshio
Published: April 2003

Aliphatic amines were used as decomposer to decompose waste rigid polyurethane and polyisocyanurate foams, and the obtained decomposed products were directly used as curing agent of epoxy resin. Effects of the decomposing condition including amine type, foam–decomposer ratio, and reaction temperature on the decomposition reaction and properties of the decomposed products were investigated. Using amines with low molecular weight could enhance decomposition reaction rate and total amine number and lessen viscosity of the obtained decomposed products. Viscosity of the decomposed products decreased with increase of reaction temperature, but increased with increment of foam–decomposer ratio. Shear strength of adhesives consisting of decomposed products and epoxy resin was measured, and their thermal properties were analyzed. The adhesives could be cured completely over 60°C and their shear strength enhances with adding coupling agent in the adhesive system. The adhesives have good thermal stability and show satisfactory shear strength with more than 15, 15, 7, and 3 MPa at 25, 60, 100, and 150°C, respectively. The results demonstrate that the obtained adhesive systems can be used as structural adhesive. © 1995 John Wiley & Sons, Inc.
Nonlinear mechanical spectrometry of poly(methyl methacrylate)
Authors: Povolo F. , Lambri O. A.
Published: April 2003

Data on the damping spectra of commercial poly(methyl methacrylate) (PMMA) are reported, both at low (of the order of 1 Hz) and at intermediate (of the order of 50 Hz) frequencies. It is shown that the damping does not only depend strongly on temperature and frequencies. It is shown that the damping does not only depend strongly on temperature and frequency but also on the strain amplitude applied to the specimen. In other words, the dynamic mechanical behavior of PMMA is nonlinear and cannot be described in terms of linear viscoelasticity. Finally, some aging effects in the damping, measured at low frequencies, are also reported. © 1995 John Wiley & Sons, Inc.
Diffusion‐controlled semibatch emulsion polymerization of styrene
Authors: Chern C. S.
Published: April 2003

Semibatch emulsion polymerization of styrene under the monomer‐starved condition is strongly affected by the gel effect. A mechanistic model based on diffusion‐controlled reaction mechanisms is developed to predict the kinetics of semibatch emulsion polymerization. Experimental data available in the literature are employed to assess the proposed model. Reasonable agreement between the model predictions and experimental data is observed. The simulation results suggest that the reaction system approaches Smith–Ewart case II kinetics (n̄ = 0.5) when the concentration of monomer in the particles is close to the saturation value, whereas the reaction system under the monomer‐starved condition is characterized by diffusion‐limited reaction mechanisms (n̄≥0.5). © 1995 John Wiley & Sons, Inc.
Swelling of and solute exclusion by poly(N‐alkylacrylamide) gels
Authors: Jin M. R. , Wu C. F. , Lin P. Y. , Hou W.
Published: April 2003

Temperature‐sensitive hydrogels of poly(N‐isopropylacrylamide) poly(N,N‐diethylacrylamide), poly(N‐N‐propylacrylamide), copolymer of N‐isopropylacrylamide and methylacrylamide, and copolymer of N,N‐diethylacrylamide and N‐tert‐butylacrylamide were prepared. The swelling characteristics of the gels were studied and gel extraction of macromolecules, based on the solute exclusion by the gel network, were investigated. © 1995 John Wiley & Sons, Inc.
Elongational flow field as a tool for investigating helix–coil transition: Observation of helix–coil transition in poly(L‐glutamic acid) induced by pH change
Authors: Hayakawa Ichiro , Sasaki Naoki , Hikichi Kunio
Published: April 2003

Elongational flow technique has been used to investigate helix–coil transition of poly(L‐glutamic acid) (PGA) induced by pH change. The elongational flow field was generated by a four‐roller mill apparatus of the type originally used by G. I. Taylor16. The flow‐induced nonlocalized birefringence was observed all over the pH range measured. The birefringence, Δn176, at a fixed strain rate ε = 176 s−1 decreases rapidly within a narrow pH range with increasing pH. The Δn176 value is considered to contain information about both helix content, θ, of the system and the degree of orientation of polymers in the elongational flow field. From the Δn176 value, using rotational diffusion coefficient, Dr, the helix content, θ, was estimated at each iso‐pH measurement. pH dependence of θ was obtained and was found to correspond well to those determined by optical rotary dispersion (ORD) studies. Even in a hinged‐rod conformation, the PGA molecule is expected to be in an extended structure. On the basis of the hydrodynamic considerations about the molecular conformation, it is concluded that the elongational flow technique is useful to investigate conformational transitions of biopolymers. © 1995 John Wiley & Sons, Inc.
Characterization of surgical adhesives from UV‐polymerized poly(PEG dimethacrylate‐co‐2‐hydroxyethyl methacrylate) copolymers
Authors: Berkowicz Brad D. , Peppas Nikolaos A.
Published: April 2003

Polymer samples that could be used as wound adhesives were prepared from poly(ethylene glycol)dimethacrylate (PEGDMA) and 2‐hydroxyethyl methacrylate (HEMA) copolymers in concentrations from 0 to 50 mol %. The UV copolymerization was initiated by 2,2‐dimethoxy‐2‐phenylacetophenone (DMPA) and ultraviolet light intensities ranged from 0.1 to 0.5 m W/cm. The volume shrinkage during photopolymerization was observed using a dilatometric technique. The overall volume shrinkage was affected by the comonomer ratio and the nature of the PEGDMA comonomer. The rate of volume shrinkage was higher at higher ultraviolet light intensities. PEG(400)DMA‐based copolymers exhibited lower glass transition temperatures than those of PEG(200)‐based copolymers. The introduction of HEMA to the copolymers reduced both their glass transition and degradation temperatures. The equilibrium water‐swelling ratio increased with increasing PEGDMA molecular weight and HEMA content. © 1995 John Wiley & Sons, Inc.
Free volume model and diffusion of organic solvents in natural rubber
Authors: Guo C. J. , De Kee D. , Harrison B.
Published: April 2003

The concentration dependence of the diffusion coefficients and the equilibrium isotherms of benzene, o‐xylene, ethylbenzene, and chloroform in natural rubber membranes at 303 K were experimentally determined. The data were used to critically test the predictive capability of the Vrentas–Duda free volume model. It was found that although the model works well for some polymer–solvent systems such as toluene‐polystyrene, the use of some of the parameters from pure component properties yields unacceptably low diffusion rates for the rubber–solvent systems studied. The parameters Do1 and ξ obtained from experimental zero‐concentration diffusivity data, and parameter V̂1* calculated from the solvent molecular geometries are needed to achieve good predictions. The diffusion coefficients described by the revised model can be used to predict quite well the breakthrough times of the rubber–solvent systems that were also experimentally measured by a permeation method. © 1995 John Wiley & Sons, Inc.
Rheological characteristics of proanthocyanidin polymers from Pinus radiata. II. Viscoelastic properties of sequential alkaline extracts based on phenolic acid fraction
Authors: Kim Seungrok , Mainwaring David E.
Published: April 2003

Steady and dynamic oscillatory rheometry were used to characterize two members of the plant polyphenols from Pinus radiata bark, water‐soluble proanthocyanidin polymers, and phenolic acids. The viscosity‐controlling factor of the extracts could be revealed by examining the various extracts under different chemical and rheological environments. Water extracted (100°C) bark was successively extracted with aqueous NaOH solutions of increasing alkalinity at 100°C and the rheological characteristics of the each fraction were examined in detail. The significant viscoelasticity of the 100°C aqueous NaOH sequential extracts suggests that this fraction can have a critical impact on the flow characteristics of overall extracts and arises from a major contribution of colloidal interactions involving the carbohydrate component. © 1995 John Wiley & Sons, Inc.
Photoinduced crosslinking of polyolefine blends. I. Crosslinking of LDPE, PP, and LDPE/PP blends
Authors: Zamotaev P. , Chodak I. , Mityukhin O. , Chorvath I.
Published: April 2003

Photocrosslinking of low‐density polyethylene, (LDPE), polypropylene (PP) and their blends was investigated using xanthone and triallyl cyanurate as a photoinitiator and a coagent, respectively. The influence of the change of UV‐irradiation conditions on the yield of photoinitiated processes was found to be very similar at any composition, while the crosslinking efficiency decreases with increase of PP content in the blend. The mechanism of the TAC action in photocrosslinking process was proposed and the effect of TAC reactions is discussed with regards to the effectivity of crosslinking of LDPE, PP, or the blends. © 1995 John Wiley & Sons, Inc.
The influence of styrene–butadiene diblock copolymer on styrene–butadiene–styrene triblock copolymer viscoelastic properties and product performance
Authors: McKay Kevin W. , Gros William A. , Diehl Charles F.
Published: April 2003

The effects of the styrene–butadiene (SB) diblock copolymer on the viscoelastic properties of styrene–butadiene–styrene (SBS) triblock copolymers were examined in both in the the neat state and within specific product applications. The addition of the SB diblock copolymer into a pure SBS triblock copolymer resulted in a significant decrease in the plateau storage modulus and a quantitative linear rise in tan delta. In a pure triblock, in which all endblocks are anchored in polystyrene domains, all entanglements are physically trapped. The SB diblock embodies untrapped polybutadiene endblocks that are able to relax stress by chain reptation through the rubbery polybutadiene matrix. The SB diblock copolymer quantitatively lowered the microphase separation temperature (MST) of the SBS triblock copolymer. These changes in linear viscoelastic behavior manifest themselves into a reduction in the efficiency and performance of the SBS triblock copolymer in asphalt pavement binders and hot‐melt adhesive blends. Specifically, the SB diblock diminished the complex shear modulus and elasticity of a polymer‐modified asphalt, which translated into lower predicted rutting specification values. The increase in diblock content altered the viscoelastic response of the hot‐melt adhesive blend, translating into a reduction in the shear holding power and shear adhesion failure temperature. The lack of network participation, coupled with the relaxation of the polybutadiene endblocks, accounts for the lower strength and greater temperature susceptibility of the diblock‐containing systems. © 1995 John Wiley & Sons, Inc.
Mechanical properties of phenolphthalein polyether ketone: Yield stress, young's modulus, and fracture toughness
Authors: Han Yanchun , Yang Yuming , Li Binyao , Feng Zhiliu
Published: April 2003

A series of tensile and three‐point bending studies was conducted at various temperatures and loading rates using phenolphthalein polyether ketone (PEK‐C). Yield stress, Young's modulus, fracture toughness, and crack opening displacement data were obtained for various conditions. In general, both yield stress and Young's modulus increase with decreasing temperature. However, the relationships between fracture toughness, loading rate, and temperature are very complex. This behavior is due to the simultaneous intersection of viscoelasticity and localized plastic deformation. The increased yield stress is the main factor contributing to the reduction in fracture toughness and crack opening displacement. The relationship between fracture toughness and yield stress are discussed. © 1995 John Wiley & Sons, Inc.
Thermal cis–trans isomerization of 4‐diethylamino‐4′‐methoxyazobenzene in poly(D(−)3‐hydroxybutyrate) and its hydroxyvalerate copolymer as a probe for characterizing their aging
Authors: Dubini‐Paglia Ernestina , Castelli Antonella , Beltrame Pier Luigi , Seves Alberto , Marcandalli Bruno
Published: April 2003

The aging of bacterial polyester poly(D(—)3‐hydroxybutyrate) has been studied by coloring it with 4‐diethylamino‐4′‐methoxyazobenzene and determining the reduction in isomerization rate of the dye with aging, such a reduction being a measure of the loss in polymer sequential mobility that is responsible for the considered phenomenon. A preliminary test carried out on poly(ethylene terephthalate) colored with 4‐diethylaminoazobenzene proved the isomerization of the dispersed dye to be a sound probe for determining the aging process. In the case of the bacterial polyester, the aging process appeared even above the polymer Tg value measured by calorimetric analysis. The kinetics and rate coefficients of aging were determined at 30°C for the examined polymers. Aging in the copolymer poly(hydroxybutyrate‐hydroxyvalerate) was also investigated. © 1995 John Wiley & Sons, Inc.
Solid‐phase peptide synthesis on a novel hydrogenolysable linker–resin combination
Authors: Pande C. S. , Gupta N. , Bhardwaj A.
Published: April 2003

The propensity of benzyloxycarbonylamide group towards clean and rapid hydrogenolysis was exploited in designing a linker for solid phase peptide synthesis on a copoly(styrene–divinylbenzene) resin support. Hydroxymethyl copoly(styrene–divinylbenzene) on treatment with 4‐nitrophenyl chloroformate gave a resin which possessed benzyl 4‐nitrophenyl carbonate pendants. These reacted with the α‐amino group of Boc–Lys–OMe, resulting in the attachment of the latter through its side chain to the resin by a benzyloxycarbonylamide linkage. This was used to extend the peptide chain from the α‐amino end of lysine by Bocmethodology. The peptide was released from the resin through palladium acetate–ammonium formate‐based transfer hydrogenolysis. The usefulness of this linker was demonstrated by synthesizing several small peptides terminating in lysine. © 1995 John Wiley & Sons, Inc.
The radical polymerization of C12–C18 alkylmethacrylates in semibatch conditions
Authors: Di Serio M. , Santacesaria E. , Santambrogio A. , Polimeni G.
Published: April 2003

The radical polymerization of C12–C18 alkylmethacrylates in solution of mineral oil has been studied in semibatch condition by using 2,2′‐azobis (2‐methylbutyrronitrile) as initiator. Many kinetic runs of polymerization have been performed in different operative conditions. A kinetic model has been developed to interpret and simulate these runs. C12–C18 alkylmethacrylate polymerization in mineral oil concentrated solution occurs through a classical radical chain mechanism. Kinetic parameters for the initiator decomposition and for the radical chain propagation rate resulted the same as reported by the literature. A particular behavior of this system is the intervention of the gel effect observed from the beginning of the reaction as a consequence of the high initial viscosity. © 1995 John Wiley & Sons, Inc.