bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

AbstractDeformation 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

AbstractLinseed 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

AbstractPoly(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

AbstractLiquid‐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

AbstractStudies 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

AbstractA 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

AbstractAliphatic 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

AbstractData 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

AbstractSemibatch 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

AbstractTemperature‐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

AbstractElongational 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

AbstractPolymer 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

AbstractThe 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

AbstractSteady 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

AbstractPhotocrosslinking 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

AbstractThe 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

AbstractA 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

AbstractThe 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

AbstractThe 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

AbstractThe 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.
Photocrosslinking of azidated poly(vinyl chloride) coated onto plasticized PVC surface: Route to containing plasticizer migration
Authors: Jayakrishnan A. , Sunny M. C. , Rajan Mini N. 
Published: April 2003

AbstractThe migration of phthalate esters which are commonly employed for plasticizing poly(vinyl chloride) (PVC) is a significant problem in PVC‐based medical devices as well as in packaging used for food stuffs and pharmaceuticals. Medical‐grade PVC resin was treated with sodium azide in dimethylformamide (DMF) to prepare the azide polymer. The polymeric azide was coated onto the surface of plasticized PVC sheets by dipping in a solution of the polymer in tetrahydrofuran (THF). Crosslinking of the azide polymer was accomplished by irradiating the surface using a 125 W UV lamp for various lengths of time. Migration of the plasticizer di 2‐(ethylhexyl phthalate) (DEHP) from coated and uncoated samples was examined in n‐hexane at 30°C. It was found that 50–80% reduction in migration of DEHP could be effected from plasticized PVC in comparison with the controls in 72 h by this technique depending on the concentration of the coating solution, coating thickness, azide concentration, and irradiation dose. © 1995 John Wiley & Sons, Inc.
Graft copolymerization of acrylonitrile and its binary mixture with 4‐vinyl pyridine onto isotactic polypropylene powder by preirradiation method
Authors: Kaur Inderjeet , Barsola Raghuvir , Misra B. N. 
Published: April 2003

AbstractGraft copolymerization of acrylonitrile (AN) and its binary mixture with 4‐vinyl pyridine (4‐VP) onto isotactic polypropylene powder in aqueous medium, using γ‐rays as an initiator, was studied. Optimum conditions for affording maximum percentage of grafting were evaluated. Rate of grafting (Rg) of AN and binary mixture (4‐VP + AN) was determined as a function of total initial monomer concentrations. The graft copolymers were characterized by IR spectroscopy and thermogravimetric analysis. © 1995 John Wiley & Sons, Inc.