bluuebunny/crossref_metadata_2025 huggingface dataset:
Kinetics of emulsion copolymerization with acrylic acids
Authors: Shoaf Glenn L. , Poehlein Gary W.
Published: April 2003

A kinetic model is presented that describes the reaction behavior of emulsion copolymerization systems where significant polymerization occurs in both the particle and aqueous phases. Equations for predicting aqueous‐phase free‐radical concentrations and aqueous‐phase and particle‐phase reaction rates are developed. A method for estimating the radical entry rate coefficient is also presented. The model is applied to two seeded carboxylated emulsion copolymerization systems, acrylic acid‐styrene and methacrylic acid‐styrene. Both experimental and predicted results reveal that the reaction behavior is greatly affected by the type of acid monomer, partition of monomer between the various phases, and locus of polymerization. The mechanism for the acrylic acid‐styrene system is more complicated than that for the methacrylic acid‐styrene system. Evidence suggests that the primary reaction locus in the acrylic acid‐styrene system shifts from the particles to the aqueous phase after the hydrophobic monomer, styrene, has been consumed.
Solution and emulsion polymerization with partially neutralized methacrylic acid
Authors: Shoaf Glenn L. , Poehlein Gary W.
Published: April 2003

Polymerizations of partially neutralized methacrylic acid (MAA) were performed in both solution and emulsion systems. Polymerizations of MAA in solution were performed at an overall degree of neutralization ranging between 0 and 1. The rate of polymerization of the acid is found to decrease as the degree of neutralization increases due to increased electrostatic repulsion of the dissociated acid species (anions). The degree of neutralization of the unreacted monomer increases as the conversion increases. A kinetic model based on a copolymerization mechanism is used to describe the reaction behavior. Partially neutralized methacrylic acid was also polymerized with styrene in a seeded emulsion system. The reaction rates of both the acid and styrene decrease as the overall degree of neutralization increases. A previously developed emulsion copolymerization kinetic model is extended to account for reaction of the anions and used to investigate the overall “terpolymerization” of the acid, anions, and styrene.
A study of the response of open end and ring spun yarns to zinc chloride and sodium hydroxide
Authors: Subramaniam V. , Selvamurugan U. , Thambidurai S. , Krishnasamy V.
Published: April 2003

An investigation of the swelling behavior of open end and ring spun yarns in slack condition in 64.5% (w/w) aqueous zinc chloride and sodium hydroxide 22% (w/w) for different intervals ranging from 30 to 90 min is reported. The results show that the response of the yarns to the swelling agents is different in that the products treated with zinc chloride are found to possess higher strength and higher bending rigidities but low elongation. Swelling of yarns with sodium hydroxide has resulted in large increase in elongation. The other properties, namely, coefficient of friction and abrasion resistance, are found to be slightly higher than that of the yarns treated with sodium hydroxide. Degree of set of open end yarns is significantly higher than that of the ring spun yarns. Coefficient of friction and abrasion resistance of the zinc chloride treated yarn samples are found to be slightly higher than that of the sodium hydroxide treated samples.
Epoxy–lignin polyblends: Correlation between polymer interaction and curing temperature
Authors: Feldman D. , Banu D. , Luchian C. , Wang J.
Published: April 2003

A bisphenol A–polyamine hardener based epoxy adhesive (EP) was modified by polyblending with Kraft lignin (L). EP–L polyblends with an L content up to 40% by weight were cured at room temperature or above their glass transition temperature (Tg). Previous data have shown that the thermal and viscoelastic properties, as well as adhesive performance of the EP–L polyblends, are influenced by the curing temperature and by the L content in thermally cured polyblends. A reasonable explanation for the different behavior of EP–L polyblends as function of the curing temperature and their L content could be the enhanced degree of bonding between L and the EP network taking place at elevated temperature. This bonding was specifically considered to take place between L and possible unreacted amine groups of the hardener. Characterization of the EP–L polyblends was performed to search for evidence of irreversible chemical bonding between L and the EP network in thermally cured EP–L polyblends. FTIR studies, L extractibility from the crosslinked, polyblends, and quantitative data concerning the reactivity of L toward the polyamine hardener are discussed.
A FT‐IR analysis method for simple unsaturated polyesters
Authors: Paauw M. , Pizzi A.
Published: April 2003

A simple and reliable FT‐IR method enabling almost complete qualitative and quantitative identification of the components of unsaturated polyester resins for glass‐reinforced laminates is presented. This method is based on percentage transmission ratios of characteristic bands in a single IR spectrum. Coupled with simple chemical tests, such as resin acid number and, when needed, UV‐VIS determination of Co (II) curing accelerators, this FT‐IR method allows the qualitative and quantitative determination of the various reacted and unreacted components of the resin. Some critical discussion of the advantages of such a method over some conventional tests is presented.
Phase behavior of ternary PBT–PC/phenoxy blends
Authors: Remiro P. M. , Nazábal J.
Published: April 2003

Ternary polymer blends were obtained by melt mixing, mixing up to 30% poly(butylene terephthalate) (PBT) with polycarbonate (PC) and phenoxy in an attempt to improve the miscibility of the PC/phenoxy binary blend. Although most of the blends with a PBT content higher than 10% appear as transparent, two Tg's appeared at all the blend compositions. These Tg's correspond to PC‐rich and phenoxy‐rich phases where a low amount of the main component of the other phase and all PBT are dissolved in amounts that are a function of the PC/phenoxy ratio of the blend. Increasing the PBT contents in the blends closes to linearity the torque versus composition plot, so that a relationship between miscibility level and viscosity exists in these blends.
Miscible blends of styrene‐acrylic acid copolymers with aliphatic, crystalline polyamides
Authors: Kuphal J. A. , Sperling L. H. , Robeson L. M.
Published: April 2003

Styrene‐acrylic acid copolymers exhibit miscibility with various aliphatic, crystalline polyamides (e.g., nylon 6, 11, and 12) at 20% acrylic acid content in the copolymer. At 8% acrylic acid, phase separation is observed with the crystalline polyamides. At 14% acrylic acid, partial miscibility is observed with each polyamide, resulting in the Tg's of the constituents shifted toward the other constituent. The miscibility of the styrene‐acrylic acid copolymers ( > 14 wt % AA) can be ascribed to hydrogen bonding interactions with the polyamides. Styrene‐acrylic acid (20% AA) copolymers are miscible with other nylons with alternating amide orientation along the chain (e.g., nylon 6,6 and nylon 6,9). These samples tend to crosslink upon exposure to temperatures above the polyamide melting point unlike the nylon 6, 11, and 12 blends in which branching may only occur. Nylon 11/styrene‐acrylic acid blends were chosen for crystallization rate studies. A melting point depression of nylon 11 occurs with addition of the styrene‐acrylic acid (20% AA). The Flory‐Huggins interaction parameter from the melting point depression is calculated to be ‐0.27. The crystallization rate of nylon 11 is significantly reduced with the addition of the miscible SAA copolymers (20% AA). The spherulitic growth rate equation predicts this behavior based on a Tg increase with SAA addition.
Na+ and Cl− transport across polyimide films
Authors: Schussler A. , Bellucci F. , Senturia S. D. , Latanision R. M.
Published: April 2003

Na+ and Cl‐ transport across 2.4‐ and 5.2‐μm‐thick polyimide (PI) PMDA/ODA and 7.5‐μm‐thick du Pont Kapton films was studied in a diffusion cell using ion‐selective electrodes. The temperature was 30°C. Diffusion coefficients Dm (in cm2/s), permeability coefficients P (in cm2/s), and distribution coefficients K were obtained by applying the time lag analysis on the ion uptake transient in the acceptor compartment of the diffusion cell. Both Na+ and Cl‐ were observed to diffuse across PI. Diffusion coefficients varied in the range 10‐12‐10‐13 cm2/s whereas ionic permeability results showed more scatter ranging from 1 X 10‐11 to 8 X 10‐14 cm2/s. The latter discrepancy was ascribed to diffuse heterogeneities on the order of 0.5 μm. No significant ionic selectivity between Na+ and Cl‐ was observed. This result indicates the absence of ionic fixed charge (unreacted polyamic acid) in the polymeric matrix. An attempt is made to determine the effect of water sorption mode and contaminants in the film on the ionic permeabilities data.
Solute and penetrant diffusion in swellable polymers. XI. The dynamic swelling behavior of hydrophilic copolymers containing multiethylene glycol dimethacrylates
Authors: Shieh Lisa Y. , Peppas Nikolaos A.
Published: April 2003

Copolymers of 2‐hydroxyethyl methacrylate with a number of multiethylene glycol dimethacrylates were prepared by bulk copolymerization in the presence of AIBN s an initiator. The content of the dimethacrylate varied between 30 and 50 mol %. Additional copolymers were prepared by solution polymerization in the presence of water or ethanol. All samples were swollen in water up to thermodynamic equilibrium, and their dynamic swelling behavior was studied as a function of time. It was concluded that the mechanism of water transport in these moderately and highly crosslinked polymers was a coupled relaxation and diffusion and that the relaxational contribution to the overall transport depended on the chain length of the multiethylene glycol dimethacrylate.
Development of interchange reactions in ternary PBT‐PC/phenoxy blends
Authors: Remiro P. M. , Nazábal J.
Published: April 2003

Ternary PBT‐PC/phenoxy blends were melt mixed for periods of time up to 110 min to determine the development of interchange reactions among the blend components. This development was evaluated by means of solvent extraction and DSC measurements on blends obtained after characteristic blending times shown in the torque vs. blending time curve. PBT reacts, after very short blending times and, probably due to residual catalyst, mainly with phenoxy. Although at high phenoxy contents a single torque peak is observed, at low phenoxy contents two peaks are observed that correspond to the two stages in which the reaction takes place: at the beginning in the phenoxy‐rich phase and later in the overall blend.
Radioluminescent polymers: Preparation of deutero‐ and tritopolystyrene
Authors: Nelson David A. , Molton Peter M. , Jensen George A.
Published: April 2003

Deuterium and tritium exchanges were performed on the aromatic groups of polystyrene using DCl or TCl and TiCl4. Up to 5 deuterium atoms per monomer unit could be placed on the aromatic groups depending upon time, DCI pressure, and TiCl4 concentration. Tritiated polystyrene mixed with zinc sulfide phosphor produced 1.06 Cd/m2 of luminance.
Thermal degradation of epoxy novolac‐phenol formaldehyde novolac resin systems
Authors: Sullivan Eileen A.
Published: April 2003

The evolution of organic vapors from encapsulants at elevated temperatures has been implicated as the source of the degradation of the gold–aluminum intermetallic of the wire that connects the bond pad to the leadframe in an integrated circuit. Gas chromatography/infrared spectroscopy/mass spectrometry were used to study the decomposition of three commercial epoxy‐novolac thermosetting compounds. Outgassing products have been identified and their origins discussed. Insight into the types of initiators used in encapsulants and their possible influence upon ball bond failure rates has been gained.
Dynamic mechanical properties of binary blends of different polyethylenes. I. Nonisothermal treatment
Authors: Orozco Jose A. Gonzalez , Rego Jose M. , Katime Issa
Published: April 2003

The relaxation processes and thermal properties of a series of blends of a highly linear high‐density polyethylene (HDPE) with several branched high‐density, linear low‐density (LLDPE) and low‐density polyethylenes (LDPE) have been measured. For the sake of comparison, all the samples were subjected to the same thermal treatment, that is, a rapid quenching from the molten state. The mechanical properties have been analyzed, taking into consideration the crystallization behavior of each sample. The existance of cocrystallization provides a bigger change in the dynamic mechanical properties than when segregation takes place. The observed changes in the end‐corrected storage modulus supports this conclusion as well as those associated with the α, β, and γ relaxation temperatures.
Microstructure, mechanical properties, and fracture behavior of liquid rubber toughened thermosets
Authors: Zeng Yi‐Bing , Zhang Lian‐Zheng , Peng Wei‐Zhou , Yu Qiao
Published: April 2003

Phenolic epoxy resin was toughened by carboxyl‐randomized butadiene acrylonitrile copolymer (CRBN) for use as composite matrix. By adding different parts of butadiene acrylonitrile copolymer (BN‐26, without carboxyl contained) to CRBN, different sizes of rubber domains and different numbers of chemical bondings between the resin matrix and the rubber phase were obtained. It is found that small rubber particles (less than 0.1 μm) are cavitated during the crack development. The interaction between secondary crack zones caused by the cavitation makes the fracture toughness KIC of the materials high; by comparison, a local stress‐whitened zone is produced in the material with large rubber particles (more than 0.1 μm) when it is subjected to tensile stress. In this case, the flexure strength σf of the material is great. Using ultrasection and TEM techniques, the stress‐whitened zone was shown to be caused by the special multiple‐phase structure of the material, in which many caves and “macrocrazes” coexist.
Crosslinking and scission in radical‐promoted functionalization of polyethylene
Authors: Kwei T. K. , Pearce E. M. , Schlecht M. F. , Cheung W.
Published: April 2003

We reported earlier on grafting hexafluoroisopropanol groups onto polyethylene through the reaction of polyethylene with hexafluoroacetone and di‐t‐butyl peroxide. The modified polyethylene was partially crosslinked. In this work, we adapted the Charlesby–Pinner Equation to estimate the ratio of chain scission to crosslinking in the reaction.
Dynamic mechanical properties of binary blends of different polyethylenes. II. Isothermal treatment
Authors: Orozco Jose A. Gonzalez , Rego Jose M. , Katime Issa
Published: April 2003

The relaxation processes and thermal properties of a series of blends of a highly linear high‐density polyethylene (HDPE) with several branched high‐density, linear low‐density (LLDPE), and low‐density polyethylenes (LDPE) have been measured as a function of crystallization temperature, Tc, and content of branched polyethylene (BPE). The influence of composition on the dynamic mechanical spectrum of the HDPE has been rationalized taking into account the dilution with increasing content of BPE of those crystals formed during the isothermal crystallization. The influence of the type of second constituent (HDPE, LLDPE or LDPE) on the relaxation process of the HDPE has been explained in terms of segregation material data.
Peroxydiphosphate/bisulfite‐initiated polymerization of acrylamide and its retardation kinetics
Authors: Bajpai U. D. N. , Bajpai A. K. , Bajpai J.
Published: April 2003

The kinetics of aqueous polymerization of acrylamide with peroxydiphosphate/bisulfite redox pair was studied at 35 ± 0.2°C under atmospheric oxygen. The rate of polymerization was found to be of first power to monomer, half‐power to catalyst, and 0.75 power to activator concentration. The overall energy of activation was calculated to be 11.0 kcal/deg mol between 25 and 45°C. The effect of addition of organic solvents and dinitrobenzenes as retarders on the rate of polymerization were studied kinetically and retardation constants for nitro compounds were evaluated by a newly proposed method (intercept method), when two retarders act simultaneously.
Polymers for information storage systems. II. Polymerization kinetics for preparation of highly crosslinked polydimethacrylates
Authors: Bowman Christopher N. , Peppas Nikolaos A.
Published: April 2003

Polymers of ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, and tetraethylene glycol dimethacrylate were prepared by photoinitiated polymerizations in the presence of 2,2‐dimethoxy‐2‐phenyl‐acetophenone at 27°C. The reactions led to highly crosslinked polymeric networks. The volume shrinkage observed during polymerization was a function of the number of ethylene glycol units in the dimethacrylate monomer. The kinetic rate constants of polymerization, as determined from the photopolymerization characteristics using a dilatometric technique, were again dependent on the number of ethylene glycol units in the monomer. The importance of these results on the crosslinked structure of the prepared networks is discussed.
Effect of hydroquinone on location of methacrylic acid‐grafted chains introduced into polyethylene film by photografting
Authors: Kubota Hitoshi , Hata Yasuo
Published: April 2003

Effect of hydroquinone (HQ) on photografting of methacrylic acid (MAA) on low‐density polyethylene film (thickness = 30 μm) sensitized with xanthone was investigated at 60°C in water medium. Both the formation of grafted polymer and homopolymer were retarded by HQ. The contact angle of water on the MAA‐grafted polyethylene films (sample with HQ) prepared in the system with HQ was larger than that of the grafted films (sample without HQ) prepared in the system without HQ. Based on electron probe microanalysis of the grafted films, it was found that distribution of grafted chains in the direction of film thickness is different between the both grafted films. Namely, the grafted chains of the sample with HQ distributed in the inside of the film compared with those of the sample without HQ. The difference in the distribution of grafted chains between the grafting systems with and without HQ was discussed in terms of effect of HQ on the photodecomposition of MAA‐grafted chains and the subsequent initiation of polymerization by radicals due to the photodecomposition.
Optical rotation of dilute aqueous xanthan solutions at elevated hydrostatic pressure
Authors: Stokke B. T. , Knudsen K. D. , Smidsrød O. , Elgsaeter A.
Published: April 2003

The optical rotation of dilute aqueous xanthan solutions of ultrasonically depolymerized xanthan have been measured in the pressure range from 0.1 to 50 MPa. This was achieved using a high‐pressure cell in a spectropolarimeter of original design. The conformational melting temperature Tm of xanthan was found to decrease with increasing pressure. The pressure coefficients of the melting temperature at constant ionic strengths, I, was found to be (ΔTm/Δp)I = −(9.5 ± 4.0) 10−8 K Pa−1 and (ΔTm/Δp)I = −(20 ± 10) 10−8 K Pa−1 for solution ionic strengths of 10 mM NaCl and 25mM NaCl, respectively. The largest shift in Tm of xanthan for an increase in hydrostatic pressure from 0.1 to 50 MPa is less than −10 K. The observed decrease in conformational transition temperature can have significant implications when xanthan is used in polymer or micellar flooding processes in high‐salinity, high‐temperature oil reservoirs where the reservoir temperature is close to the structural transition temperature at ambient pressure.
Self‐condensation of oxidized lignosulfonate. II. Condensation behaviors
Authors: Chen Rubie , Wu Guoxiong
Published: April 2003

Studies have been made on the principal parameters that affect the self‐condensation of oxidized lignosulfonate, such as lignin content, pH, temperature, time of hot pressing, and oxidation. During condensation, the hydroxyl groups in both the lignosulfonate and carbohydrate molecules could react with carboxyl, sulphonic acid, and carbonyl groups to form an ester bond and result in (hemi) ketal and (hemi) acetal structures. These structures made condensation products having excellent resistance in water and in alkaline solutions. The results also demonstrated that the oxidized lignosulfonate could be condensed at a higher rate than could the untreated one.
Invariant kinetic parameters of polymer thermolysis. III. The influence of a fire‐retardant additive on polypropylene thermolysis
Authors: Vyazovkin S. V. , Bogdanova V. V. , Klimovtsova I. A. , Lesnikovich A. I.
Published: April 2003

The present paper analyzes the thermolysis gross‐kinetics of polypropylene (PP) and a PP‐based fire‐resistant composition containing 10% of hexabrominecyclododecane (HBCD) as the fire‐retardant additive. The kinetic parameters of thermolysis of an individual PP are calculated by the isoconversion method. The increasing dependence of the effective activation energy on the transformation degree has been established. This dependence is attributed to the competitive character of the processes of thermodestruction initiated by oxidation and to the PP pyrolysis. Thermolysis in the helium atmosphere leads to oxidation suppression and increases the effective activation energy at the initial stage of thermolysis. A similar effect can be attained by introducing HBCD into PP, which permits considering the ability of inhibiting the oxidation process proceeding in the condensed phase as one of the reasons of the fire‐retardant activity of this additive.
Analysis of reaction‐injection‐molded polyurethanes by near‐infrared diffuse reflectance spectroscopy
Authors: Miller Charles E. , Eichinger B. E.
Published: April 2003

The ability of near‐infrared (NIR) diffuse reflectance spectroscopy to characterize reaction‐injection‐molded (RIM) polyurethane elastomers is demonstrated. The advantage of NIR spectroscopy over other analytical methods is its ability to analyze samples without any preparation. In this work, the specific effects of composition, density, phase separation, and moisture content on the NIR spectra of the polymers are identified. In addition, the ability of NIR spectroscopy to make rapid assessments of physical properties, such as heat sag and flex modulus, is demonstrated. In order to perform these analyses, the multivariate statistical methods of principal components analysis (PCA) and partial least squares (PLS) are used.
Preparation of asymmetric film by blending two kinds of polymer emulsions having greatly different storage stabilities
Authors: Okubo Masayoshi , He Yuan
Published: April 2003

Two kinds of anionic polymer emulsions with different particle sizes were blended and cast on a release‐paper at 30°C. One was poly(butyl acrylate) emulsion, and the other was ethyl acrylate–methyl methacrylate (1 : 1, weight ratio) copolymer emulsion. They were produced by emulsifier‐free emulsion polymerization. The blend films prepared in an appropriate range of the blend ratio had a great difference in tackiness between both surfaces: The air‐side surface exhibited tackiness and the release‐paper side showed nontackiness. The forming mechanism is discussed.
Kinetics and properties of a photopolymerized dimethacrylate oligomer
Authors: Cook Wayne D.
Published: April 2003

The free radical photopolymerization of two urethane dimethacrylate oligomer systems, used in dentistry as elastomeric impression materials, was investigated. When cured in thick section, these materials have a limited depth of cure that depends on the irradiation conditions. A mathematical model is presented that considers the spatial dependence of the polymerization process on the attenuated radiation intensity and the local concentration of radical scavenging inhibitors. The predicted dependence of the depth of cure on the logarithm of radiation intensity and exposure time is confirmed. DSC studies revealed that for thin sections the rate of polymerization had the conventional square root dependence on radiation intensity over a 1000‐fold range of intensities. These results are discussed in terms of a decoupling of the mobility of the pendant methacrylate group from the chain to which it is attached. In an oxygen environment, inhibition of the photopolymerization caused an induction period that was proportional to the reciprocal radiation intensity. Modulus measurements during cure also illustrated the rapid nature of photopolymerization process and showed that in comparison to conventional two‐component materials used for the same purpose the rates of buildup in properties for the photocured materials were superior. The tear energy of the cured photocured materials were compared with conventional types of elastomeric impression material, and the differences were interpreted in terms of energy dissipation mechanisms.
Model esterification of neopentyl glycol and trimethylol propane with 1,4‐tert‐butyl benzoic acid
Authors: McCarthy Jennifer L. , Scholtens Boudewijn J. R.
Published: April 2003

The esterification kinetics of difunctional neopentyl glycol and trifunctional trimethylol propane with monofunctional 1,4‐tert‐butyl benzoic acid was studied in the melt phase at 200°C in the presence of a metal catalyst. The rate of conversion was monitored via titrations and by determination of the relative concentrations of products and reactants using HPLC with a UV detector. A small but significant positive substitution effect was found for neopentyl glycol (KDA = 1.15) and none was found for trimethylol propane. The reaction rate constant of neopentyl glycol with the acid is about 40% higher than that of trimethylol propane with the acid. A second‐order overall reaction order was used to compute the rate constants.
Studies on the preparation and properties of conductive polymers. III. Metallized polymer films by retroplating out
Authors: Huang Chueh‐Jung , Yen Chih‐Chao , Chang Teh‐Chou
Published: April 2003

A novel method to prepare polymer metallized films was found by using polymer metal chelate films treated with wetted metal plates (or metal powders). The polymer metal chelate films were prepared by metal salts mixed with the polymers containing a functional group, such as poly(vinyl alcohol) (PVA), polyamide, polyacrylamide (PAAm), and polyurethane (PU). This novel method is called the retroplating‐out method. Polymer metallized films exhibited low surface resistivity around 10−1 Ω/cm2 by using this novel method. The surfaces of these films were shown to be metallized by means of X‐ray analysis. The conduction mechanism was verified reasonably well by using scanning electron microscope (SEM) and UV‐visible absorption data.
Characterization of hydroxypropylcellulose–indomethacin grafts as a function of molecular weight
Authors: Meyer Glenn A. , Lostritto Richard T. , Johnson Julian F.
Published: April 2003

The physical characterization of hydroxypropylcellulose–indomethacin grafts (HPC–IND) is described. Using size‐exclusion chromatography (SEC) and serial differential refractive index (dRI) and ultraviolet spectrophotometric (UV) detection methods, it was possible to characterize the chemical substitution of the HPC–IND graft. Using the acid chloride of IND as the reactive intermediate, the HPC–IND graft was synthesized. The amount of IND grafted onto the polymer as a function of the HPC molecular weight (MW) was then quantitatively estimated. It was found that the substitution of IND onto the HPC was not uniform, representing chemical heterogeneity of the first kind. Increasingly higher substitution (of IND to HPC) was observed as the MW decreased (<250,000 Daltons) for the HPC backbone. Lower, more uniform substitution was observed for the higher molecular weight regions of the HPC (>250,000 Daltons). Possible contributing factors affecting the observed nonuniform substitution include (1) the chain coiling of the HPC in solution, thus limiting the availability of the pendant hydroxyl groups, (2) nonuniform substitution of the hydroxypropyl moiety onto the cellulose backbone, and (3) steric effects resulting from the incorporation of the bulky aromatic drug molecule onto the backbone HPC.
Synthetic resin. XI. Preparation and characterization of resins derived from picoline and lutidine/aromatic hydroxy, amino, and chloro compounds/formaldehyde
Authors: Mohanty Pronab K. , Lenka Subasini
Published: April 2003

A number of resin copolymers have been prepared by condensing α‐picoline, γ‐picoline, and lutidine separately with hydroxy acetophenone, hydroxy, amino, chloro benzoic acids, and toluic acid in the presence of sodium hydroxide and succinic acid as catalyst. The resins were characterized by infrared spectra of the characteristic groups. The solubility parameters were calculated from Small's group's contribution. The antifungal activity of the resins have also been investigated.
Diffusion and sorption of organic liquids through polymer membranes. I. Polyurethane versus n‐alkanes
Authors: Khinnavar R. S. , Aminabhavi T. M.
Published: April 2003

Sorption and diffusion studies of n‐alkanes through a commercial polyurethane membrane have been investigated in the temperature interval of 25–60°C. Liquid diffusivity through polyurethane was measured by using the immersion/weight gain method and the diffusion mechanism was explained in terms of the Fickian model. The activation energies of sorption and diffusion processes have been estimated and used to investigate the thermodynamic interactions between polyurethane chains and n‐alkanes. Furthermore, sorption data were used to estimate the molar mass between crosslinks of the network polymer.
Bead‐spring macromolecules that perturb the solvent: Scleronomic, monogenic, molecular forces
Authors: Grisafi S.
Published: April 2003

When linear, conservative, molecular forces are used in this bead‐spring model of a polymer solution, a viscoplastic constitutive equation results. Using nonlinear intramolecular forces removes this viscoplasticity. The analysis shows that the anisotropy of the normal stresses is related to the anisotropy of the molecular forces. At the theta temperature the anisotropy of the intramolecular force alone determines the normal stress anisotropy. Nonlinear molecular forces are necessary for the analysis to predict a shear rate dependence for the stress in steady homogeneous flow. The symmetry of the stress tensor constrains the Hooke's law constants used to model the molecular forces. No overshoot is predicted for the stress response to a step change in shear rate when linear forces are used. Using linear forces, the stress response to a unit step shear rate shows a tendency of the polymer solution to undergo plastic deformation and to take a set.
Grafting onto wool fibers: Graft copolymerization of methyl methacrylate onto wool fibers initiated by KHSO5/Fe(III) couple
Authors: Giri Gitisudha , Samal Rajani K.
Published: April 2003

Graft copolymerization of methyl methacrylate (MMA) onto wool fibers has been carried out in an aqueous medium under deaerated condition initiated by potassium monopersulphate (KHSO5/Fe(III) system, at varying concentration of the reactants and temperature. The effect of various salts and organic solvents on the extent of grafting has also been studied. Maximum graft percentage of 210.8% was obtained in 4 h at 40°C with the concentration of MMA (0.46 M), KHSO5 (0.0195 M), Fe(III) (1.25 × 10−4 M) in the presence of 50% formic acid. Various improved properties of the grafts have been studied and compared with the parent fiber.
Side reactions of phenylisocyanate in N,N‐dimethylacetamide
Authors: Matsui Toshimi , Kamatani Hiroyoshi , Arimatsu Yoshikazu , Kaji Atsushi , Hattori Kazuhiro , Suzuki Hajime
Published: April 2003

Side reactions of isocyanate groups in N,N‐dimethylacetamide (DMAC) were studied. Although 4,4′‐diphenylmethane diisocyanate (MDI) in DMAC was stable and no changes occurred at 3°C, the isocyanate content decreased and a gel was finally formed at 40°C. Using phenyl isocyanate (PI) as a model compound of MDI, the identification of PI side‐reaction products in DMAC were studied. From these experiments, the following five products were identified; (1) 1,3‐diphenylurea (DPU), (2) 1,3‐diphenyl‐5‐phenylcarbamyl‐6‐dimethylaminouracil (PUR), (3) 1,3,5‐triphenylbiuret (TPB), (4) triphenyl‐s‐triazine‐2,4,6‐trione (TTT), and (5) 1,1‐dimethyl‐3‐phenylurea (DMPU). Among these identified products, the novel side reaction product PUR, which was formed between PI and DMAC as solvent, was found along with TPB and TTT, which were already known to cause three‐dimensional network formation.
Synthesis and thermal stability, dielectric, and conductivity characteristics of polymers with pendant and backbone anthracene sulfonyl groups
Authors: Majumdar Amitava , Biswas Mukul
Published: April 2003

Anthracene‐mono‐ and disulfonyl derivatives of polystyrene and poly (N‐vinylcarbazole) have been prepared and the thermal stability, dielectric, and conductivity of these polymer pendant sulfones have been evaluated. The anthracene‐based benzene, naphthalene, anthracene, and biphenyl copolysulfones have also been prepared and characterized in regard to the above‐cited properties. Interesting variations in these properties between these two classes of polymers carrying pendant and backbone sulfonyl groups have been noted and rationalised from structural considerations.
Prefailure damage processes in highly filled glass/mica/epoxy composites
Authors: Regola M. , Baer E. , Hiltner A.
Published: April 2003

In the present study, the prefailure damage processes of a series of short glass fiber/mica/epoxy composites under three‐point bending were elucidated using acoustic emission (AE) coupled with in situ scanning electron microscopy (SEM) observations. This study consisted of a detailed investigation of the damage tolerance of composite systems that had constant inorganic content of 75% by weight with a varying ratio of glass fibers to mica. The flexural strength was found to increase from 11 to 21 ksi as the glass fiber content increased (mica content decreased), while the flexural modulus decreased from 5.0 to 2.5 Msi. By monitoring the AE during flexural deformation of the glass fiber‐to‐mica ratio composites, it was determined that low amplitude (0–42 db) AE events, which occurred throughout the deformation process, were caused by matrix cracking, whereas the high‐amplitude (43–100 db) AE events, which occurred just prior to failure, were caused by a fiber‐related mechanism. In situ SEM observations of the composites during flexural deformation allowed a correlation between the AE and the damage mechanisms as a function of strain. In the all‐mica composite, microcracking initiated in the linear region at preexisting flaws, on the order of 10 μm, located at the mica interface. These microcracks grew along the mica contours over the majority of the deformation process, emitting low‐amplitude events, until final fracture occurred at relatively low strains. In the glass fiber‐containing composites, microcracking initiated in the linear region at preexisting flaws and voids, on the order of 10 μm. These microcracks grew slowly, emitting low‐amplitude events, as the strain increased, but were prevented from causing failure at low strains because of the toughening effect of the glass fibers. At sufficiently high strains, however, fiber breakage and fiber pull‐out occurred that corresponded to the high‐amplitude events detected by the AE. At strains just prior to failure, catastrophic crack growth occurred, producing a rapid increase in both low‐and high‐amplitude events, causing ultimate failure.
Impregnation of white pine wood with unsaturated polyesters to produce wood–plastic combinations
Authors: Doss N. L. , Elawady M. M. , Elawady N. I. , Mansour S. H.
Published: April 2003

Two unsaturated polyester resins based on poly(1,2 propylene–maleate–phthalate) (PE1), and poly(oxy–diethylene–maleate–phthalate) (PE2) were used for the impregnation of oven‐dried white pine wood samples in admixture with styrene (S). Curing was affected by the initiator‐heat technique by either using 0.1–0.2% by weight of benzoyl peroxide (Bz2O2), or 1% by weight of methyl ethyl ketone peroxide (MEK). It was found that the use of PE1/S mixture resulted in the formation of wood–plastic combinations (wpc) with higher percent retention and higher percent polymer loadings than those obtained by the impregnation of wood samples with PE2/S imxtures. The use of different swelling solvents including ethanol, acetone or chloroform, did not influence the percent retention or polymer loadings of wpc for either PE1/S or PE2/S mixtures. Physical tests performed on wpc showed that compression, hardness, static bending were generally enhanced, water absorption was decreased, and dimensional change was retarded to different extents for both polyesters used, but no permanent stabilization was attained.
Analysis of thermal degradation for plastic optical fibers
Authors: Takezawa Yoshitaka , Tanno Seikichi , Taketani Noriaki , Ohara Shuichi , Asano Hideki
Published: April 2003

Attenuation loss of plastic optical fibers (POFs) gradually increases with long use at high temperatures. We separated attenuation loss of the POFs before and after heating at 150°C in air into four loss factors, and identified the main factor for attenuation loss increase as electronic transition absorption loss (αe). The increase of αe was caused by a thermal oxidation reaction of the core polymer in the POF. But, according to NMR and FT‐IR spectra, elementary analysis, etc., hardly any reaction products were detected. We assume that the reaction products were only a small amount of the conjugated carbonyl groups. So we fabricated POFs containing model compounds with conjugated carbonyl groups, and measured their attenuation loss. The attenuation loss spectra of these POFs were similar to those of thermally degraded POFs. Consequently, a very small amount of conjugated carbonyl groups were formed by the thermal oxidation reaction of core polymer so that αe increased to an unacceptable level.
Swelling effect of semicrystalline poly(vinyl alcohol) in hydrogen peroxide
Authors: Lee Ping I.
Published: April 2003

The effect of hydrogen peroxide on the physicochemical properties of semicrystalline poly(vinyl alcohol) (PVA) has been investigated. Significant and irreversible increases in equilibrium water swelling, dissolved oxygen permeability, and surface wettability have been observed in PVA samples treated with concentrated hydrogen peroxide. Based on the small amount of carbonyl content detected and the crystallinity reduction in hydrogen‐peroxide‐treated poly(vinyl alcohol) samples, a mechanism involving a combination of hydrogen‐peroxide‐induced oxidative chain scission and dissolution of crystalline regions in poly(vinyl alcohol) is proposed for the observed swelling kinetics and associated changes in polymer properties.
Synthesis of telechelic dithiol oligomers containing sulfur atoms‐moisture barrier properties
Authors: Pujol J. M. , Brossas J. , Catala J. M.
Published: April 2003

The aim of this work was to synthesize new polysulfide materials from butadiene, styrene, isoprene, and methacrylate monomers and to study their moisture vapor permeability. For this purpose, a series of telechelic dithiol polysulfide oligomers were prepared by a polycondensation reaction between dianionic species of the corresponding monomer and sulfur or by reduction of the resulting cyclic polysulfide polymers. This last process was followed by 1H‐NMR and elemental analysis. It was established that the scission of the polysulfide linkages to thiol end groups was fastest with the greatest number of sequential sulfur atoms. The thiol reactivity was used to prepare cured materials from the liquid oligomers and manganese dioxide: Networks were obtained from butadiene dithiol oligomers, whereas chain extension occurred for the others. Infrared analysis suggests that the reticulation reaction results from thiol addition to the double bond. The moisture vapor transmission test applied to these different materials showed that these new compounds present good moisture barrier properties.
Study on the crystallization kinetics of PP/GF composites
Authors: Tai Horng‐Jer , Chiu Wen‐Yen , Chen Leo‐Wang , Chu Line‐Hwa
Published: April 2003

The crystallization kinetics and morphology of glass fiber‐reinforced polypropylene (PP/GF) were investigated in this work. Both isothermal and nonisothermal crystallization behaviors of 90PP/10GF, 80PP/20GF, and 70PP/30GF were examined with a DSC instrument. It was found that the addition of glass fiber would increase the crystallization rate of PP and increase the content of β spherulite, which was most likely formed at temperatures between 390 and 400 K. The morphology of spherulites of PP/GF composites were examined with SEM and a polarized microscope. All experimental observations conformed rather well with the theoretical approach, a dynamic crystallization model, proposed in our previous work. The size of α spherulites of PP would decrease at lower crystallization temperature, or at higher cooling rate, or by adding glass fiber in it.
Optimal periodic control of a continuous “living” anionic polymerization. III. Presence of impurities in the monomer feed
Authors: Vega J. R. , Frontini G. L. , Meira G. R.
Published: April 2003

Previous publications have demonstrated that when “living” anionic polymerizations are carried out in continuous reactors under forced periodic operation of the feed flows then: (a) In the absence of impurities and within certain limitations, it is possible to produce polymers with any prespecified values of the number‐average chain length, the polydispersity and the polymer production; and (b) even small concentrations of impurities in the monomer feed, drastically inhibit such a possibility. In this work, the optimal periodic control problem has been reformulated, including the presence of impurities. In all cases, the flexibility of the control is reduced with respect to the impurities‐free case.
Plastic optical fibers with fluoroalkyl methacrylate copolymer as their core
Authors: Takezawa Yoshitaka , Tanno Seikichi , Taketani Noriaki , Ohara Shuichi , Asano Hideki
Published: April 2003

Novel plastic optical fibers having a core made of a crosslinking copolymer containing mainly fluoroalkyl methacrylate (FMA–POFs) were fabricated and their optical properties were analyzed. In the visible wavelength region, attenuation losses of as‐manufactured FMA–POFs were low and their loss spectra were similar to that of the plastic optical fiber whose core was made of methyl methacrylate copolymer (MMA–POF). But after heating at 160°C in air, increases in attenuation losses of FMA–POFs were about 10 times smaller than that of the MMA–POF. FMA–POFs had an optical window at 780 nm. There was hardly any change in loss at 780 nm compared with the loss increase at 660 nm. This indicated that FMA–POFs would be applicable to optical communications at 780 nm in the near‐IR region.
Polyurethane elastomers based on molecular weight advanced poly(ethylene ether carbonate) polyols. III. Effects of diisocyanate modified diols
Authors: Harris Robert F. , Joseph Michael D. , Davidson Carla , Deporter Craig D.
Published: April 2003

A series of diisocyanate‐modified, molecular weight advanced poly(ethylene ether carbonate) diols has been prepared, characterized, and formulated into polyurethane elastomers using a prepolymer process. Properties were compared to a polyurethane elastomer control in which the only variable was the diisocyanate modification. The diisocyanate modification produces polymers with increased modulus (445–730% at 25°C), improved tensile strength and hardness properties and reduced (improved) coefficients of linear thermal expansion, while still passing the notched Izod impact test. The tensile strength at break increases with increasing number of urethane moieties in the soft segment and the elongation at break also increases. The plaques studied appear to have a three‐phase morphology—a soft segment continuous phase containing amorphous hard segment, an amorphous hard segment phase plasticized by about 11% of the soft segment material, and a crystalline hard segment. The polymers based on the diisocyanate modified polyols are significantly more phase mixed than the control due to the increased amount of hard segment‐soft segment interactions taking place. The improved properties of the polymers made with the modified polyols are due to their higher hydrogen bonding protential which gives more physically crosslinked polymers.
Photodegradation of polyimides. I. A spectral, viscometric, chromatographic, and weight loss investigation of polyimides based on a hexafluorinated dianhydride
Authors: Hoyle C. E. , Anzures E. T.
Published: April 2003

The photodegradation of aromatic‐dianhydride‐based polyimide films in air with hexafluorinated groups in the dianhydride moiety is characterized by significant weight loss and chain cleavage. A conventional polyimide film based on pyromellitic dianhydride yields little decomposition under similar conditions of photolysis. Emission changes on photolysis of polyimide solutions demonstrate an efficient rearrangement to yield a highly fluorescent species which can be used as an effective tool for following the degradation process.
Photodegradation of polyimides. II. Thermal property changes of polyimides based on a hexafluorinated dianhydride
Authors: Hoyle C. E. , Anzures E. T.
Published: April 2003

Polyimides based on a hexafluorinated dianhydride decrease in thermal and thermal‐oxidative stability upon photolysis with an unfiltered medium pressure mercury lamp source in air. Additionally, the glass transition of photolyzed polyimides containing the hexafluorinated moiety is lowered with increasing photolysis time. By contrast, pyromellitic‐dianhydride‐based polymers are relatively thermally stable even after prolonged photolysis under similar conditions.
Response time measurements of liquid crystal dispersed in polyester resin film
Authors: Mucha M.
Published: April 2003

New material consisting of nematic liquid crystal droplets from 2‐30 μm in radius in a crosslinked UV‐cured polyester resin binder was prepared. Micrographs of the samples were taken in the optical microscope with cross‐polaroids. Reorientation of the droplets by application and removal of an electric field is discussed. Electrooptic properties of the material were measured using polarized light from a helium‐neon laser. Transmittance and response time vs. voltage applied with driving frequency 2 kHz were detected on the oscilloscope and photographed. The response times were: rise time τon shorter than 20 ms at applied voltage higher than 50 V, and decay time τoff = 80 ms. They are a promising feature for this material for a display application.
Irradiation of oriented LDPE films
Authors: Nikolova M. , Mateev M.
Published: April 2003

Low‐density polyethylene (LDPE) films deformed uniaxially at 70°C and to low draw ratios have been irradiated on a 60Co source with a dose rate of 0.33 Mrad/h in air. Their elastic modulus has been determined at room temperature and at 145°C, and their crystallinity has been studied by wide‐angle X‐ray scattering (WAXS). A two‐stage process has been proposed for the influence of irradiation on the structure and properties of the films. The first stage is characterized by enhanced chain scission in the strained regions, as a result of which structural reorganization takes place there and the crystallinity increases. This increase is greater for higher draw ratios and higher doses. The second stage is characterized by no structural changes in the material. The value of D, which separates the two stages, shifts toward higher doses for higher draw ratios. Under the conditions of the present experiment, the orientation of the films decreases the efficiency of network formation by the irradiation.