bluuebunny/crossref_metadata_2025_split huggingface dataset:
Enzymatic degradation of blends of poly(ε‐caprolactone) and poly(styrene‐co‐acrylonitrile) by Pseudomonas lipase
Authors: Cho Kilwon , Lee Jaeyoung , Xing Pexiang 
Published: August 2002

AbstractIn polymer blends, the composition and microcrystalline structure of the blend near surfaces can be markedly different from the bulk properties. In this study, the enzymatic degradation of poly(ε‐caprolactone) (PCL) and its blends with poly(styrene‐co‐acrylonitrile) (SAN) was conducted in a phosphate buffer solution containing Pseudomonas lipase, and the degradation behavior was correlated with the surface properties and crystalline microstructure of the blends. The enzymatic degradation preferentially took place at the amorphous part of PCL film. The melt‐quenched PCL film with low crystallinity and small lamellar thickness showed a higher degradation rate compared with isothermally crystallized (at 36, 40, and 44°C) PCL films. Also, there was a vast difference in the enzymatic degradation behavior of pure PCL and PCL/SAN blends. The pure PCL showed 100% weight loss in a very short time (i.e., 72 h), whereas the PCL/SAN blend containing just 1% SAN showed ∼50% weight loss and the degradation ceased, and the blend containing 40% SAN showed almost no weight loss. These results suggest that as degradation proceeds, the nondegradable SAN content increases at the surface of PCL/SAN films and prevents the lipase from attacking the biodegradable PCL chains. This phenomenon was observed even for a very high PCL content in the blend samples. In the blend with low PCL content, the inaccessibility of the amorphous interphase with high SAN content prevented the attack of lipase on the lamellae of PCL. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 868–879, 2002
Thermal and rheological studies on the molecular composition and structure of metallocene‐ and Ziegler–Natta‐catalyzed ethylene–α‐olefin copolymers
Authors: Starck P. , Malmberg A. , Löfgren B. 
Published: August 2002

AbstractThe relationship between the molecular structure and the thermal and rheological behaviors of metallocene‐ and Ziegler–Natta (ZN)‐catalyzed ethylene copolymers and high‐density polyethylenes was studied. Of special interest in this work were the differences and similarities of the metallocene‐catalyzed (homogeneous) polymers with conventional coordination‐catalyzed (heterogeneous) polyethylenes and low‐density polyethylenes. The short‐chain branching distribution was analyzed with stepwise crystallization by differential scanning calorimetry and by dynamic mechanical analysis. The metallocene copolymers exhibited much more effective comonomer incorporation in the chain than the ZN copolymers; they also exhibited narrower lamellar thickness distributions. Homogeneous, vanadium‐catalyzed ZN copolymers displayed a very similar comonomer incorporation to metallocene copolymers at the same density level. The small amplitude rheological measurements revealed the expected trend of increasing viscosity with weight‐average molecular weight and shear‐thinning tendency with polydispersity for the heterogeneous linear low‐density polyethylene and very‐low‐density polyethylene resins. The high activation energy values (34–53 kJ/mol) and elevated elasticity found for some of our experimental metallocene polymers suggest the presence of long‐chain branching in these polymers. This was also supported by the comparison of the relationship between low shear rate viscosity and molecular weight. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1140–1156, 2002
Reinforcement of poly(dimethylsiloxane) networks by montmorillonite platelets
Authors: Osman Maged A. , Atallah Ayman , Kahr Günter , Suter Ulrich W. 
Published: August 2002

AbstractA PDMS network, synthesized from a vinyl‐terminated precursor, was reinforced by plate‐like montmorillonite (volclay) particles with different surface cations. The optimal ratio of crosslinker‐to‐PDMS precursor was ascertained from the mechanical properties of networks prepared with different crosslinker concentrations. The elastic modulus of the polymer was enhanced by the montmorillonite particles. The increase in modulus was higher in the Li– than in the Na–volclay composites. The ultimate strength of the composites was also strongly enhanced by the small platelets, especially in presence of surface Li+. The stronger influence of Li–volclay on the mechanical properties of the composites can be attributed to the partial formation of an intercalated structure, which leads to thinner particles with a high aspect ratio. Both composite strength and modulus were proportional to the filler‐volume‐fraction, but the increase in strength was limited by rising particle agglomeration at high loading. In contrast to organic‐modified montmorillonite, the inorganic surface of volclay catalyzed the thermal degradation of PDMS. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2175–2183, 2002
Mechanism of migration from agglomerated cork stoppers: I. An electron spin resonance investigation
Authors: Six Thérèse , Feigenbaum Alexandre , Riquet Anne‐Marie 
Published: August 2002

AbstractRelated to the study of interactions between food and packaging, migration from agglomerated cork stoppers was studied by electron spin resonance. Paramagnetic probes were incorporated separately in the adhesive or in the cork granules. The finished cork was obtained by an individual molding procedure. The behavior of aminoxyl probes, differing by their functional groups, was studied. Free probes, initially incorporated into the adhesive phase, partitioned into cork during processing. Their migration occurred from both the cork and the adhesive phases. With amino‐TEMPO, a probe covalently bonded to the adhesive phase, it was possible to study the penetration of the alcoholic simulant of wine (12% ethanol) into the whole structure of the cork and to demonstrate that strong swelling took place. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2644–2654, 2002
Correlation among crystalline morphology of PEEK, interface bond strength, and in‐plane mechanical properties of carbon/PEEK composites
Authors: Gao Shang‐Lin , Kim Jang‐Kyo 
Published: August 2002

AbstractThe effect of the cooling rate on in‐plane and interlaminar properties of carbon fiber/semicrystalline PEEK matrix composites was studied. Strengths and moduli were measured in tension, flexure, and interlaminar shear, all of which were shown to correlate, to different degrees, with the fiber–matrix interface adhesion and the bulk matrix properties. The in‐plane and interlaminar properties, in general, increased with a decreasing cooling rate, which was attributed to changes in the failure mechanism from adhesive failure involving fiber–matrix interface debonding at high cooling rates to matrix‐dominant cohesive failure at low cooling rates. The present study demonstrates that the mechanical properties of semicrystalline thermoplastic composites can be tailored for desired applications by controlling the processing conditions, especially the cooling rate. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1155–1167, 2002; DOI 10.1002/app.10406
Orientation and crystallinity in film casting of polypropylene
Authors: Lamberti Gaetano , Brucato Valerio , Titomanlio Giuseppe 
Published: August 2002

AbstractIn the cast film process a polymer melt is extruded through a slit die, stretched in air, and cooled on a chill roll. During the path in air the melt cools while being stretched. Film casting experiments were carried out with an isotactic polypropylene resin. The temperature and width distributions were measured along the draw direction. Further, the crystallinity and Hermans orientation factor were measured on the final film. The process was described by a simple thermomechanical model derived elsewhere. The evolution of the molecular orientation parameters was calculated on the basis of a dumbbell model coupled with velocity and temperature distributions provided by the thermomechanical model. The experimental crystalline orientations of the final films collapsed into a single step‐shaped curve (from low to high orientation) if plotted versus the stress calculated by the model at the frozen line. The experimental values of the crystallinity and Hermans orientation factors are discussed on the basis of predictions of the dumbbell model for melt orientation at the frozen line and the crystallinity data obtained in quiescent conditions under the same cooling rate. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1981–1992, 2002; DOI 10.1002/app.10422
Mechanical properties of natural rubber filled with flyash
Authors: Hundiwale D. G. , Kapadi U. R. , Desai M. C. , Bidkar S. H. 
Published: August 2002

AbstractThe mechanical properties of flyash‐filled natural rubber were investigated and compared with those filled with calcium carbonate. A number of composites with varying percentage of the fillers were prepared using a two‐roll mill and molded on compression molding press. Specimens were subjected to mechanical testing. The properties studied were tensile strength, modulus at various elongations, hardness, density, etc. From the results it was observed that flyash‐filled composites were better in mechanical properties compared to those filled with calcium carbonate. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 995–1001, 2002
Hardness evaluation of epoxy resin filled with mineral waste
Authors: D'Almeida J. R. M. , Manfredini B. H. P. 
Published: August 2002

AbstractThe care of the world environment poses many challenges to the proper disposal of mineral wastes. Particulate wastes can be used to modify the properties or lower the cost of polymers. The influence of an iron–silica rich waste on the hardness of an epoxy resin is evaluated in this work. It is shown that the hardness values are polymer dominated for volume fractions of waste lower than 0.30, but for higher volume fractions a useful increase in the hardness numbers can be achieved. The coarser the particles are the more heterogeneous is the microstructure of the composite. Nevertheless, particulate rich layers increase the hardness of the material several times. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2178–2184, 2002
Morphology and micromechanical deformation behavior of SB‐block copolymers. II. Influence of molecular architecture of asymmetric star block copolymers
Authors: Adhikari R. , Michler G. H. , Lebek W. , Goerlitz S. , Weidisch R. , Knoll K. 
Published: August 2002

AbstractThe influence of molecular architecture on morphology, mechanical properties, and micromechanical deformation behavior of asymmetric styrene/butadiene star block copolymers is investigated by transmission electron microscopy (TEM) and uniaxial tensile testing. In contrast to diblock copolymers, star block copolymers having 74% polystyrene (PS) show a lamellar morphology. Furthermore, tapered asymmetric star block copolymers having a PS core reveal additional PS domains inside the PB lamellae not observed in untapered star block copolymers. The introduction of tapered sequences in star block copolymers results in a significant improvement of tensile properties due to the increased interfacial width between the phases as well as differences in morphology. The investigated star block copolymers show a homogeneous plastic deformation of PS lamellae. This mechanism is called thin‐layer yielding of PS lamellae. The lamellae are locally deformed via inhomogeneous necking and drawing. Lamellae which are not oriented parallel to the load direction are twisted to the deformation direction. Neat star block copolymers (without tapered chains) exhibit a premature failure of PS lamellae arising from the decreased interfacial width, which results in a decrease of their ultimate strain. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 701–713, 2002
Seeded dispersion polymerization
Authors: Wang Danni , Dimonie Victoria L. , Sudol E. David , El‐Aasser Mohamed S. 
Published: August 2002

AbstractMicron‐size poly(n‐butyl acrylate) (PBA) and polystyrene (PSt) particles were used as seed in second‐stage seeded dispersion polymerizations. The effects of various polymerization parameters on the morphology of the structured particles resulting from the second‐stage seeded dispersion polymerizations were studied, and a series of uniform micron‐size structured particles was successfully prepared. In addition to the polymerization medium, the type of stabilizer (i.e., the molecular weight of the polyvinylpyrrolidone [PVP] stabilizer) that was used in the seed preparation and the subsequent seeded dispersion polymerization was found to be important. The final outcome of a seeded dispersion polymerization, that is, the morphology of the structured particles and the formation of secondary particles, was found to be primarily governed by thermodynamic factors. It was also found that the latex particles in these dispersion systems are virtually stabilized by the small amount of grafted PVP molecules. The dispersions maintain colloidal stability after repeated washing of the particles, which removes all of the soluble PVP. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2710–2720, 2002
Influence of vinyl ester/styrene network structure on thermal and mechanical behavior
Authors: Shan L. , Robertson C. G. , Verghese K. N. E. , Burts E. , Riffle J. S. , Ward T. C. , Reifsnider K. L. 
Published: August 2002

AbstractThe influence of vinyl ester/styrene network structure on thermal and mechanical properties was investigated. The crosslink density of the resins was altered by changing the molecular weight of the vinyl ester oligomer and by varying the amount of styrene used during the crosslinking reaction leading to variations in both the physical network structure and the chemical composition of the polymeric networks. The glass transition temperatures of the network polymers were found to increase systematically with increasing crosslink density without the additional influence of the chemical composition as determined from both differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). The breadth of the glass transition regions increased with crosslink density for the DSC data, but the breadth assessed from the DMA data did not vary significantly for the network materials. A secondary relaxation was observed for the materials using DMA, and this relaxation did not appear to be significantly affected by changes in either the crosslink density or the composition of the network. Cooperativity studies involving time–temperature scaling of dynamic mechanical data in the glass formation temperature region were also conducted. The degree of segmental cooperativity at Tg appeared to be primarily influenced by the chemical composition of the networks. These issues dealing with the structure of the networks provided insight into the associated fracture properties in the glassy state (ambient temperature). Specifically, an empirically based linear correlation was found between the fracture toughness of the networks and the cooperative domain size at the glass transition temperature normalized by the crosslink density. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 917–927, 2001
Hydrolysis, polycondensation, and catalytic properties of Ru(II) complex of 3‐4,5‐dihydroimidazol‐1‐yl‐propyltriethoxysilane
Authors: Seçkin Turgay , Özdemir İsmail , Çetinkaya Bekir 
Published: August 2002

AbstractThe preparation and measurements of some properties of organic–inorganic hybrid materials derived from Ru(II)‐3‐4,5‐dihyroimidazol‐1‐yl‐propyltriethoxysilane inside a polysiloxane network have been achieved. The hydrolysis and polycondensation of Ru(II)‐3‐4,5‐dihyroimidazol‐1‐yl‐propyltriethoxysilane were performed in different experimental conditions, producing a new organic–inorganic silica. The alkoxysilyl groups available were used for the construction of inorganic backbone by the sol‐gel process, and the imidazole group was found suitable for incorporating Ru(II) by coordination. The coordination of metal complex is retained because there is no leaching from the metal complex containing gels. To ensure sufficient catalytic properties, a series of hybrid materials from tetraethoxysilane was prepared. These materials were identified and catalytic activities were tested for cyclization of (Z)‐3‐methylpent‐2‐en‐4‐yn‐1‐ol to 2,3‐dimethylfuran. Heterogeneous Ru(II) catalyst can also be recycled and reused without significant loss of selectivity or activity. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1329–1334, 2001
Photoaging and stabilization of rigid PVC/wood‐fiber composites
Authors: Matuana Laurent M. , Kamdem Donatien P. , Zhang Jun 
Published: August 2002

AbstractUltraviolet (UV) weathering performance of unpigmented and rutile titanium dioxide pigmented rigid polyvinyl chloride (PVC)/wood‐fiber composites has been studied. The composite samples were manufactured by dry‐blending PVC, wood fibers, and other processing additives in a high‐intensity mixer. The dry‐blended compounds were extruded and compression molded into panel samples. The manufactured samples were artificially weathered using laboratory accelerated UV tests. Composite samples were exposed to 340‐nm fluorescent UV lamps and assessed every 200 h, for a total of 1200 h of accelerated weathering. Each assessment consisted of a visual examination of surface roughness or erosion, a contact angle measurement, a FTIR collection, and a color measurement. The experimental results indicated that wood fibers are effective sensitizers and that their incorporation into a rigid PVC matrix has a deleterious effect on the ability of the matrix to resist degradation caused ultraviolet irradiation. The light stability of these composites could be improved quite efficiently with the addition of rutile titanium dioxide photoactive pigment during formulation. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1943–1950, 2001
Crystallization of Nylon 11 under compressive high strain rates
Authors: Fernandez J. O. , Swallowe G. M. , Lee S. F. 
Published: August 2002

AbstractThe mechanical behavior of semicrystalline Nylon 11 was studied at strain rates between 10−3 and 8800 s−1. X‐ray diffraction and DSC were employed to examine the crystal structure and the crystallinity content. The as‐received material comprised a mixed structure of a predominately triclinic (α) form. DSC revealed that the material gave rise to two melting peaks. The compressive flow stress of Nylon 11 experienced a large increase at 1200 s−1 and decreased at higher strain rates. The maximum level of the flow stress corresponded with a higher level of crystallinity and a structure mainly of a pseudohexagonal form. The subsequent drop in stress at higher rates was associated with a decrease in the crystallinity content and a mixed crystal structure, different from that observed in the as‐received material. After compression, the low melting peak disappeared and the material melted over an increased temperature range. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2031–2038, 2001
On oxidation and adhesion of copper‐filled PE
Authors: Lin D. G. , Vorobieva E. V. 
Published: August 2002

AbstractThe IR‐spectroscopy and MVCIR technique were used to study the role of technological factors (filler content, film thickness) in oxidation of polyethylene coatings filled with copper powder. It was learned that copper powder introduced into polyethylene reduces the ultimate level of oxidation of both the outer surface layer and deep‐seated layers of the polymer; also, the layer thickness of the specimens oxidized at diffusion conditions was observed to be decreased. Besides, the oxidation gradient determined through the specimen thickness was decreased on increasing the filler content. For example, with copper concentration over 3 vol %, the ultimate level of oxidation within the polymer layer that undergoes diffusive oxidation remains unchanged. The filler exerts its influence on bonding of the coatings, first of all through variations in the oxidation level of the polymer layer bordering on the substrate. For example, at the filler concentration above 3 vol %, the achievable level of adhesional strength does not depend on the coat thickness (the coat thickness being smaller than that of the diffusively oxidized layer). In thicker coatings, oxidative transformations do not, in fact, take place in the zone of adhesional contact, and the adhesion strength remains unchanged during thermal treatment. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2047–2052, 2001
Rheological study of crosslinking and gelation in bismaleimide/cyanate ester interpenetrating polymer network
Authors: Hu Xiao , Fan Jing , Yue Chee Yoon 
Published: August 2002

AbstractIn searching for high performance polymer resins that have a combination of low dielectric constant and loss, high temperature resistance, ease of being processed, and other desirable properties, an interpenetrating polymer network (IPN) based on cyanate ester (CE) and 2,2′‐diallylbisphenol A (DBA) modified bismaleimide resin (BMI) was prepared via prepolymerization followed by thermal curing. This work discusses the use of multiple waveform rheological technique to investigate the crosslinking and gelation behavior of this resin system at various temperatures. The gel point can be accurately determined from a single experiment using this technique. At the point of gelation, both the storage modulus (G′) and loss modulus (G″) of the IPN follow a similar power law equation with oscillation frequency used in the rheological measurement. Both the relaxation exponent n, a viscoelastic parameter related to the cluster size of the gel, and gel strength S, related to the mobility of the crosslinked chain segments, were determined via a curve fitting method. Both n and S were found to be temperature dependent in this BMI/DBA–CE IPN system. The apparent activation energy of gelation or curing reaction was found to be approximately 47.6 kJ/mol. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2437–2445, 2001
Physical properties of PP‐g‐AA prepared by melt extrusion and its effects on mechanical properties of PP
Authors: Mai Kancheng , Li Zhengjun , Zeng Hanmin 
Published: August 2002

AbstractPolypropylene grafting with acrylic acid, PP‐g‐AA (FPP), was prepared by melt extrusion. The physical properties of FPP and effect of FPP on mechanical properties of polypropylene (PP) were investigated. Experimental results showed that an increase in the grafting rate of FPP resulted in an increase in the crystallization peak temperature, melt peak temperature, and degree of crystallization of PP. Double melting peaks were observed for OPP prepared by adding dicumyl peroxide into PP and FPP with low grafting rate due to the degradation of PP. As the grafting rate was increased, the double melt peaks converted into a single melt peak. It is suggest that FPP with higher grafting rate resulted in enhanced nucleation and crystallization ability of PP. The grafting of AA onto the PP chain improved the thermal stability and mechanical properties of PP materials. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2609–2616, 2001
Graft copolymerization of PU membranes with acrylic acid and crotonic acid using benzoyl peroxide initiator
Authors: Pulat Mehlika , Babayiğit Doğan 
Published: August 2002

AbstractTo improve water wettability of polyurethane (PU), graft copolymerization with acrylic acid (AA) and crotonic acid (CA) was performed using a benzoyl peroxide (BO) initiator. The grafting reaction was carried out by placing the membranes in aqueous solutions of AA and CA at constant temperatures. Variations of graft yield with time, temperature, initiator, and monomer concentrations were investigated. The optimum temperature, polymerization time, monomer, and initiator concentrations for AA were found to be 70°C; 3 h; 1.5 M; 5.0 × 10−2 M, and for CA 70°C; 1 h; 1.5 M; 4.0 × 10−2 M, respectively. The grafting membranes were characterized by FTIR spectroscopy and scanning electron microscopy (SEM) analysis, and the effect of grafting on equilibrium water content (EWC) of PU membranes was obtained by swelling measurements. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2690–2695, 2001