bluuebunny/crossref_metadata_2025 huggingface dataset:
A facile antistatic modification of polyester fiber based on ion‐exchange reaction of sulfonate‐modified polyester and various cationic surfactants
Authors: Sano Yoshiyuki , Konda Marcekazu , Lee Chan Woo , Kimura Yoshiharu , Saegusa Takeo
Published: April 2003

A new technique for imparting antistatic properties to poly(ethylene terephthalate) (PET) fiber has been developed. In this technique, blend polyester fibers containing poly(ethylene terephthalate/5‐sulfoisophthalate) (SIP‐PET) were prepared by blend spinning and then treated with various cationic surfactants in the process of dyeing. The surfactants could effectively be immobilized on the fiber as the counter cations of the sulfonate groups of the 5‐sulfoisophthalate (SIP) units and aid the release of static electrons formed in the fiber. Thus, the half‐life time (t1/2) of leakage of static charge and the surface resistivity (Rs) of the blend PET fibers became much lower after treating. The best result was obtained with a methylated quaternary ammonium salt of a stearylamine‐ethylene oxide (EO) adduct or hydrochloride of a laurylamine‐EO adduct as the surfactant of which the number of EO units was around ten. Even after five washing cycles the t1/2 value of the fibers treated with these surfactants was kept lower than 30 s with the Rs value maintained in the order of 1013 Ω cm‐2. Therefore, the present technique could be useful for practical production of polyester fibers with “semi‐permanent” antistatic properties which can be recovered by re‐treatment even if they were lost.
Oxidation behavior and stabilization of metallocene and other polyolefins
Authors: Foster George N. , Wasserman Scott H. , Yacka Douglas J.
Published: April 2003

EXXPOL® metallocene catalyst technology featuring very high‐productivity catalyst systems is expected to provide ethylene polymer compositions that show excellent oxidative stability based on their minimal unsaturation content and low innocuous metal residue of a non‐acidic nature. Metallocene ethylene polymers such as mLLDPE should be comparable to the most stable, commercial polyethylenes such as linear low‐density polyethylenes (LLDPE) from the UNIPOL® gas phase PE process.

As background, the oxidation behavior and stabilization case of “total residue” polyolefins based on Ziegler‐Natta or Cr catalysis systems are reviewed. The interacting effects of polymer structure (i.e., tertiary hydrogen and unsaturation) and catalyst residue are discussed in terms of competing degradation reactions ‐ e.g., chain breakage, chain enlargement (or cross‐linking) and chain branching. The metal (Ti, V and Al) and chlorine residues from Ziegler‐Natta catalyst systems and the Cr residue for Cr catalyst systems can play a role in adversely affecting polymer oxidative stability. The residue levels and their nature govern whether there is an appreciable effect on oxidative stability, and therefore the stabilization requirements.

Discussed are thermo‐oxidative studies under melt processing conditions which compare selected EXXPOL®/UNIPOL® mLLDPEs with several state‐of‐the‐art Ti/Mg and Cr catalyzed LLDPE from the UNIPOL® gas phase PE process and a high‐pressure, low‐density polyethylene (HP‐LDPE). Standard melt flow and discoloration tests are combined with specialized experiments using dynamic oscillatory shear rheometry and size exclusion chromatographyviscometry to illustrate performance shifts due to polymer composition differences under melt processing conditions. The advantages of dynamic melt rheometry are illustrated in terms of sensitivity to subtle degradation changes in molecular structure. EXXPOL®/UNIPOL® mLLDPE having low unsaturation and metal residue which are non‐catalytic to auto‐oxidation show excellent intrinsic oxidative stability. The discoloration resistance of EXXPOL®/UNIPOL® mLLDPE is high, comparable with HP‐LDPE and the high‐activity Cr catalyzed LLDPE. Stabilization ease for EXXPOL®/UNIPOL® mLLDPE is equivalent to product counterparts (similar MI and density) made using high‐activity, state‐of‐the‐art Cr or Ti/Mg catalyst systems designed for use in the UNIPOL® gas phase PE process.
The role of charge transfer complexes in the photodegradation of polyolefins
Authors: Gijsman P.
Published: April 2003

Addition of HALS‐stabilisers, the cut‐off wavelength of the light source, the temperature and the oxygen pressure have an influence on the UV‐degradation mechanism of polyolefins. All these parameters influences the conversion of oxygen into polymeric carbonyls. The results are explained assuming that the initiation of the UV‐degradation of pololefins is due to substrate‐oxygen charge transfer complexes (CTCs).
Increasing the performance and permanence of polymer stabilizers
Authors: Gray Robert L. , Neri Carlo
Published: April 2003

A new generation of polysiloxane based polymer stabilizers is examined. The flexibility and versatility of polysiloxane backbones have allowed the development of a family of products which provide outstanding radical trapping efficiency, an unexpected resistance to extraction, and a high degree of compatibility in certain polymeric systems. Functionalization with graftable moieties results in a product which can be chemically bound to the polymer itself. The key to success in this work was optimizing the balance of graft linkages and mobility of the stabilizer chain.
Fracture behavior of exposed HDPE specimens with an embrittled layer due to UV‐exposure
Authors: Hoekstra H. D. , Breen J.
Published: April 2003

The applicability of fracture mechanics was studied on UV‐exposed HDPE Charpy specimens. The failure distribution of the stress at failure measured in three‐points bending tests showed a bifurcation in failure processes. At high stresses yielding occurs, resulting in large strain at failures. At lower stresses crack propagation causes low strain at failures. Due to the bifurcation in failure processes the ductile‐brittle transition temperature of exposed specimens is hard to determine.

Specimens notched after exposure showed a decrease in the critical stress intensity values. The effective notch depth of exposed specimens was found to be larger than the thickness of the oxidized layer measured by FT‐IR and density measurements.
Radiation induced degradation of polymers ‐an approach by using liquid paraffins as a model system
Authors: Katsumura Yosuke
Published: April 2003

Paraffins, n‐hexadecane and squalane, were employed as a model of polymers and radiation induced reactions in the polymers have been simulated. After vacuum irradiation, products were identified and their yields were determined by a variety of techniques. In the presence of the aromatic additives, the reduction of the degradation, so called protection effect, was clearly observed. Both energy and charge transfer play important roles in the protection effect. The same system was adapted to the irradiation under aerated condition in order to clarify the radiation induced oxidation. Furthermore, corresponding experiments using polypropylene were also performed and validity of the model system and phase effect were discussed. On the basis of the above results, it was revealed that the model experiment is valuable to understand the radiation induced reactions in polymers, especially amorphous phase of the polymers.

Recently, the same model system has been extended to the thermal degradation at the temperature ranges of 300 ‐ 400°C. When radiation was introduced, both a significant acceleration of the degradation and an enhancement of H2 evolution were clearly observed. This is suggesting a potential application of radiations to the degradation of polymers at elevated temperatures.
The preparation and performance of “Cage” diphosphites as secondary antioxidants in the stabilization of polyolefins
Authors: Klender G. J. , Elnagar H. Y.
Published: April 2003

“Cage” diphosphites, a new family of phosphorus antioxidants, are discussed in regard to their preparation, properties, and effectiveness in polyolefins, particularly, with phenolic stabilizers, in respect to their ability to control melt flow and color during processing. These trivalent phosphorus compounds have two different types of phosphite functionalities in their structure. One phosphorus is part of an eight membered (1,3,2‐dioxaphosphocine) ring system while the other is part of a tricyclic cage of carbon and oxygen atoms. This structures can contribute to improved hydrolytic stability over rather similar aryloxy‐alkoxy phosphites and show competitive stabilization effectiveness in the processing of polyolefins. The possible modes of formation and of hydrolysis are discussed.
Deactivation processes of 2‐hydroxyphenyl‐1,3,5‐triazines — polymeric and monomeric UV absorbers of the benzotriazole and triazine class
Authors: Keck Jürgen , Stüber Guido J. , Kramer Horst E. A.
Published: April 2003

In the 2‐hydroxyphenyl‐1,3,5‐triazines, the intramolecular hydrogen bond is stronger than in the corresponding 2‐hydroxyphenylbenzotriazoles. Compounds with only one aryl group in the 2‐hydroxyphenyl‐1,3,5‐triazine series show proton‐transferred fluorescence with large Stokes shift and high quantum yield. No such fluorescence is observed, in contrast, for compunds with three aryi groups bearing no electrondonating groups on the aryl moieties. When the hydrogen atom of the intramolecular hydrogen bond is replaced by CH3, the respective derivative shows fluorescence with a normal Stokes shift.

Various copolymers of MA‐TIN 1 (2‐[2‐hydroxy‐3‐tert.‐butyl‐5‐(O‐[2‐hydroxy‐3‐(2‐methylpropenoyloxy)propyl]‐2‐carbonyloxyethyl)phenyl]benzotriazole), and MA‐TZ 1 (2,4‐Bis(2,4‐dimethyl‐phenyl)‐6‐[2‐hydroxy‐4‐(2‐hydroxy‐3‐[2‐methylpropenoyloxy])propoxyphenyl]‐1,3,5‐triazine) with styrene, methyl methacrylate, and methacrylic acid have been synthesized by radical polymerization. The absorption spectra in the longwavelength UV region appear unchanged compared to those of the monomeric UV absorbers indicating that the stabilizer chromophores are conserved intact in the polymer. Both the monomeric and the polymeric stabilizers exhibit a strongly Stokesshifted, temperature‐dependent, low‐quantum‐yield, proton‐transferred fluorescence. This may be taken as evidence that the intramolecular hydrogen bond, which is essential for the photostability of this type of UV absorber, remains intact also in the copolymers. Activation energies of the radiationless deactivation process can be evaluated from the temperature dependence of this fluorescence. These energies lie between 4 and 5 kJ/mol for most of the benzotriazole and triazine stabilizers investigated.

Fluorescence‐decay measurements with crystalline MA‐TIN 1 at different temperatures reveal a close correspondence of the temperature dependence between decay times and relative quantum yields. The radiationless process is thence concluded to originate from the proton‐transferred level S1'. The decay time at room temperature is estimated at 70 ps, close to the value for crystalline TIN P (2‐(2‐hydroxy‐5‐methylphenyl)benzotriazole). The proton‐transferred fluorescence of MA‐TIN 1 exhibits a biexponential decay profile whereas solid TIN P, in contrast, displays only one single lifetime.
Oxidizability of lactams and lactam‐based polyamides
Authors: Lánská Božena
Published: April 2003

In the chain oxidation of N‐alkylamides with molecular oxygen, propagation is the ratedetermining step under conditions when the oxidation rate is independent of oxygen pressure. The oxidizability of lactams and lactam‐based polyamides correlates with the energy of the formation of N‐alkylamide radical by abstraction of hydrogen from the methylene group adjacent to nitrogen. While for lactams this energy depends on the number of carbons in the lactam ring, for N‐alkylamides and polylactams such dependence is not observed.
Percolation concept as applied to the degradation of elastomer networks
Authors: Ono Katsumichi
Published: April 2003

The kinetics of the degradation of elastomer networks are most conveniently disscussed by the stress relaxation which is due to the time change of the effective number of the network chain caused by thermo‐oxidative scission and/or crosslinking reaction. However, this view is only correct in the initial stage of the oxidation. In the later stage, several number of elastically effective network chains simultaneously lose their effectiveness by the scission of only one network chain. In order to explain the network behavior in the course of degradation, we introduced a percolation concept to the degradation of the network chain. The important parameter of this concept is the critical exponent. We determined the critical exponent in the vicinity of gel to sol transition of ealstomer network by comparing the tensile modulus of DCP vulcanized rubber and the gel fraction. The experimentally determined critical exponent was in good agreement with the value which was calculated for the 3D percolation. From this point of view, we can construct a universal curve for the degradation. All the experimental stress relaxation curves fall in this universal curve by taking the critical point of degradation as a standard state.
Use of EPR to image nitroxyl radicals in hals stabilized polymers
Authors: Lucarini Macro , Pedulli Gian Franco
Published: April 2003

An X‐band EPR‐Imaging apparatus which allowed us to determine the distribution of nitroxyl radicals within solid samples of polymeric materials containing hindered amine stabilizers, is described. It is shown that EPR Imaging represents a powerful tool for investigating the growth and decay of nitroxyls formed in polymers irradiated under air for long periods. Since the variations of the radical concentration can be monitored both in time and in the space, this technique provides valuable information not easily attainable by means of other methods.
Ethylene‐vinyl acetate (EVA) encapsulants for photovoltaic modules: Degradation and discoloration mechanisms and formulation modifications for improved photostability
Authors: Pern F. J.
Published: April 2003

Long‐term photothermal stability is needed for the polymeric encapsulants made of ethylenevinyl acetate (EVA) copolymer used in crystalline‐silicon (c‐Si) based photovoltaic (PV) modules. Severe browning of EVA was observed in late 1980s on Carrisa Plains PV arrays installed with reflecting mirrors and resulted in large losses of the power output. The EVA browning crisis prompted NREL scientists in 1990 to investigate the problems and search for solutions. The key degradation mechanisms and discoloration factors were investigated by using a variety of film samples, including field‐degraded EVA samples and two commercial EVA formulations, regular‐cure A9918 and fast‐cure 15295, that were laminated, cured, and subjected to accelerated environmental exposures. Chemical, thermogravimetric, absorption/transmission, colorimetric, and fluorescence analyses were employed to characterize the EVA samples. Current‐voltage (I‐V) measurements were used to determine the electrical performance characteristics of solar cells. The results show that photothermal degradation is greater than thermal degradation and that the EVA A9918 discolors earlier and faster than EVA 15295. The UV absorber, Cyasorb UV 531,TMin commercial formulations decomposes photochemically and its decomposition rate is directly related to the temporal evolution of discoloring polyenic chromophores. In general, the loss rate of the UV absorber and the progress of EVA discoloration from light yellow to brown follow a sigmoidal pattern. Physically, UV‐filtering glass superstrates that remove UV ≤ 350 nm effectively reduce the discoloration rate of both commercial EVA formulations. Chemically, the EVA discoloration rate is affected by a number of factors, but more strongly by the formulation additives and curing conditions, in which additives and curinggenerated chromophores and their concentrations show a synergistic discoloring effect. Photobleaching reactions are responsible for the non‐discolored but degraded EVA because of oxidative destruction of the curing‐generated chromophores in the presence of oxygen. By using specifically selected stabilizers and curing agents in the new formulations, a large reduction in the chromophore generation by curing has been achieved and resulted in significant improvement of the photostability against discoloration.
Photo‐oxidation mechanisms of poly(2,6‐dimethyl‐1,4‐phenylene oxide).
Authors: Scoponi Macro , Ghiglione Chiara
Published: April 2003

A re‐examination of the photo‐oxidation mechanism of poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO) at both long and short irradiation wavelengths under accelerated conditions is reported. The formation rate of poly‐2,6‐dimethylphenoxy (PDMP) radicals, have been observed by esr spectroscopy, while benzylic‐type radicals have been detected by spin trapping experiments using nitrosodurene under UV irradiation conditions. The changes of FTIR spectra obtained under accelerated photo‐oxidative conditions show the formation of primary oxidation products such as aromatic aldehydes and quinones. The direct formation of radical cations and superoxide anions by a photo‐induced electron‐transfer reaction is suggested under our conditions. In addition, some results on the of photo‐oxidation PPO/PS blends as a function of polystyrene tacticity are also reported. In the case of syndiotactic polystyrene the blend photostability shows some differences in comparison with the blend containing atactic polystyrene. This effect has been ascribed to the absence of excimers in syndiotactic polystyrene which are not revealed by fluorescence measurements. Finally, the chemical modification of PPO with bromine gave a bromomethylated PPO with different amounts of CH2 Br groups, which has been used for further substitution reactions with alkoxy sodium salts of 4‐hydroxy‐2,2,6,6‐tetramethyl‐1‐piperidinyloxy (TEMPO) and 4‐hydroxy‐1,2,2,6,6‐pentamethylpiperidine (PMPP). The accelerated photo‐oxidation of a modified copolymer PPO‐PMPP containing a 60% PMPP moieties as side groups and its blends with pure PPO has been followed by FTIR and esr spectroscopies. Some comparisons with a commercially available hindered amine light stabilizers (HALS) and a modified copolymer PPO‐PMPP are also reported under the same photo‐oxidative conditions.
The effects of desolvation methods of the recrystallized MgCl2‐alcohol adduct on catalyst characteristics and the bulk density of polyethylene
Authors: Chung Jin Suk , Han Jae Hyuck , Cho Han Suk , Lee Wha Young , Park Hong Man
Published: April 2003

The MgCl2 supports for an ethylene polymerization catalyst were prepared by the recrystallization method using methanol as a solvent. The effects of different desolvation methods of the recrystallized MgCl2‐alcohol adduct on the morphological characteristics of the catalysts were examined. The desolvation method greatly affects the characteristics of the catalyst. The prepared catalysts had different Ti/Mg ratios with respect to both surface content and entire catalyst particles. Considering Ti distribution and activity profiles, not only the polymerization conditions but also the Ti distribution on the catalyst appear to be an important factor which affects the bulk density of the polymers.
Zähigkeit und Relaxationsverhalten von Polymethylmethacrylat, Polystyrol und Polycarbonat
Authors: Grellmann Wolfgang , Lach Ralf
Published: April 2003

Innovative Kunststoffanwendungen, die die speziellen Eigenschaften polymerer Werkstoffe gezielt ausnutzen, erfordern vertiefte Kenntnisse über festigkeits‐ und zähigkeitsbestimmende Mechanismen. Das sich in Abhängigkeit von der Temperatur ändernde Werkstoffverhalten von PMMA, PS und PC wurde bei dynamischer Beanspruchung mittels instrumentierter Kerbschlagbiegeprüfung bestimmt. Mit der verformungsbestimmten Rißöffnungsverschiebung δ und dem energiebestimmten J‐Integral stehen Kenngrößen der Fließbruchmechanik zur Verfügung, die eine strukturbezogene Quantifizierung der temperaturabhängigen mikromechanischen Prozesse erlauben. Die J‐Integralwerte zeigen für PMMA bei 50°C und für PC bei −60°C ein durch einen energiedissipativen Prozeß verursachtes Maximum. Dieses Maximum steht, wie sich aus der Interpretation der Frequenzabhängigkeit des mechanischen Verlustfaktors ergibt, mit der Neben(β)‐Relaxation in Beziehung. Dabei initiiert die β‐Relaxation Scherdeformationsmechanismen, die ihrerseits die lokale Zähigkeitserhöhung bewirken. Ab −25°C führt für PC ein spannungsinduzierter Scherfließprozeß zu einer erheblichen Zähigkeitssteigerung. Durch die Einbeziehung lichtmikroskopischer Untersuchungen des stabilen Rißfortschritts auf der Bruchfläche können Morphologie‐Zähigkeits‐Korrelationen abgeleitet werden.
Thermostable block copolymers, 2. Preparation and characterization of soluble blockcopolyimides
Authors: Sychra Marcel , Gruber Heinrich
Published: April 2003

New poly(amide‐imide)‐poly(imide) block copolymers (PAI‐PI‐BCPs) were prepared by polycondensation of amino‐terminated PAI‐blocks with anhydride‐terminated PI‐blocks. For the syntheses of the blocks with molecular weights from 2000 to 15000 only commercially available monomers were used, e.g. trimellitic acid anhydride chloride, benzophenone tetracarboxylic acid dianhydride, 4,4′‐diaminodiphenylmethane, 2,4‐toluenediamine and 4,4′‐diaminodiphenylsulfone. The BCPs were shown to have better solubility compared to the pure, insoluble PIs with only minor decrease of the thermostability. Thus, BCPs with good mechanical properties, thermostabilities up to 480°C (thermogravimetric analysis, 5% weight loss) and good solubility in dimethylacetamide and other polar aprotic solvents were obtained.
Synthesis of aromatic poly(ether ketone)s with ferrocene units in the main chain
Authors: Tunca Ümit
Published: April 2003

Aromatic poly(ether ketone)s with ferrocene units in the main chain were prepared by direct polycondensation of 1,1′‐ferrocenedicarboxylic acid with diphenyl ether or 1,4‐diphenoxybenzene using various catalysts such as trifluoromethanesulfonic acid (triflic acid), a combination of methanesulfonic acid/P2O5 (Eaton's reagent) or a combination of triflic acid/P2O5. Polycondensations at room temperature for 24 h gave poly(arylene ether ketone)s with inherent viscosities up to 40 mL g−1. Monoacylation of diphenyl ether with ferrocenecarboxylic acid was studied in detail in order to show the efficiency of polymer formation employing Eaton's reagent as catalyst and solvent.
Pervaporation membranes made of functionalized block copolymers
Authors: Schauer Jan , Lochmann Lubomír , Janata Miroslav , Bleha Miroslav
Published: April 2003

Pervaporation membranes were prepared with the separation layer made of various block copolymers. These copolymers were either unsubstituted hydrogenated polystyrene‐block‐polyisoprene or its derivatives substituted with Si(CH3)3, CH2OH, or COOCH3 groups in the polystyrene block. Composite membranes with a separation layer made of the unsubstituted copolymer preferentially transported water in pervaporation of aqueous solutions of ethanol or 1,4‐dioxane. Composite membranes with a separation layer made of the copolymer with COOCH3 groups also preferentially transported water in pervaporation of aqueous solutions of ethanol and in pervaporation of aqueous solutions of 1,4‐dioxane if the concentration of 1,4‐dioxane was low in the feed mixture. Composite membranes with a separation layer made of the trimethylsilylated copolymer transported preferentially ethanol or 1,4‐dioxane. Membranes with a separation layer containing hydroxymethyl groups exhibited high permeability but no selectivity.
Block and graft copolymers with polysiloxane and poly(N‐acyliminoethylene) sequences
Authors: Simionescu Cristofor I. , Rusa Mariana , David Geta , Pinteala Mariana , Harabagiu Valeria , Simionescu Bogdan C.
Published: April 2003

A series of polysiloxane/poly(N‐acetyliminoethylene) (PSiO/PNAI) block and graft copolymers were synthesized by the initiation of 2‐methyl‐2‐oxazoline (Me‐OZO) polymerization with functional polysiloxane prepolymers. The copolymerization products were characterized by IR‐ and 1H NMR spectroscopy, elemental analysis, DSC and thermogravimetry. The insertion of both hydrophobic and hydrophilic sequences in the macromolecular structure induces a behavior characteristic of amphiphilic compounds. Their solution and solid state behavior evidenced peculiarities which make them able to act as nonionic emulsifiers, surface modifiers, gels, etc.
Compared properties of aromatic polyamides containing silicon in the main chain
Authors: Sava Ion , Szesztay Marta , Bruma Maria , Mercer Frank , Schulz Burkhard
Published: April 2003

Two series of aromatic polyamides incorporating silicon together with phenylquinoxaline or with hexafluoroisopropylidene groups have been synthesized and their properties have been characterized and compared with those of related polymers. These polymers are easily soluble in polar amidic solvents such as N‐methyl‐2‐pyrrolidinone and dimethylformamide, and in tetrahydrofuran, and can be cast into thin, transparent films from solution. The polyamides have weight‐ and number‐average molecular weights in the range of 10 000–40 000 and 3 000–6 000, respectively, and polydispersities in the range of 3–10. They show glass transition temperatures in the range of 236°C–275°C and decomposition temperatures above 400°C. The polymer films have low dielectric constants in the range of 3.26–3.68, and good mechanical properties (tensile strength 74–100 MPa, tensile modulus 180–386 MPa), thus being comparable with other high performance dielectrics.
Biological degradation of cellulose acetate films: Effect of plasticizer
Authors: Jiang L. , Hinrichsen G.
Published: April 2003

Biodegradation of plasticized cellulose acetate (PCA) was established with a standard municipal solid waste (ED 73). The relative percent weight loss of the specimen was measured, and the aerobic biodegradation was evaluated in a controlled aerobic composting system that was designed to capture CO2 produced by microbiological metabolism. Infrared spectra (FTIR), mechanical properties and molecular weight of degraded PCA films indicate that the lower molecular weight fractions, such as plasticizer and lower substituted fractions of PCA, are biodegraded and removed preferentially from the PCA.
A study of particle initiation in vinyl chloride emulsion polymerization using response surface experimentation
Authors: Lazor John T.
Published: April 2003

Vinyl chloride monomer was polymerized in an emulsion system in the presence of a redox catalyst and relatively low concentrations of emulsifier. The effects of sodium bisulfite, potassium persulfate, and commercial sodium lauryl sulfate concentrations on particle initiation were determined by response‐surface experimentation. A regression equation was developed which describes the number of particles per unit volume initiated in this vinyl chloride emulsion system. At subcritical emulsifier concentrations, the number of particles initiated was dependent primarily upon the emulsifier and sodium bisulfite concentrations and to a lesser degree upon the persulfate concentration. As the critical micelle concentration was approached, an apparent change in the particle initiation mechanism was observed, in that the sodium bisulfite concentration ceased to have an effect. In this system the change occurred at a concentration of 0.005% emulsifier.
The force‐temperature behavior of swollen cellulose model filaments
Authors: Passaglia Elio , Koppehele H. P.
Published: April 2003

The force as a function of temperature at constant length for cellulose model filaments swollen in water shows a maximum the temperature of which decreases with increasing orientation. At an orientation achieved by a prestretch of 80%, no more maximum exists, and the force decreases monotonically with increasing temperature. This behavior cannot be attributed to changes in the entropy and enthalpy of elongation with temperature, but is due rather to changes in the degree of swelling. When corrections are made for this, the positive force‐temperature coefficient observed for some of the curves becomes negative. The equilibrium stress‐strain curves are linear up to elongations of 5%. The‐oretical evaluation of these curves is not possible with the present state of theory. Filaments with predominantly a skin structure show a minimum in the force‐temperature curves; this is the more common behavior.
Preparation of porous membranes
Authors: Harper B. G.
Published: April 2003

A new method for preparing plastic membranes with very small pores is described. The method involves dissolving two or more film‐forming polymers in a common solvent. A thin layer of the resulting solution is spread on a smooth surface and the solvent is allowed to evaporate. One of the polymers is then extracted from the resulting film with a selective solvent. The selective permeability of ethyl cellulose was altered considerably using polyethylene glycol as the second polymer. The apparatus for determining the permeability of these films is described. Pictures of the membranes at different stages in their preparation are shown. Electron micrographs demonstrating the effect of this treatment on ethyl cellulose are presented.
Ultraviolet spectroscopic studies on aqueous polyvinyl alcohol solutions. Part I. Characterization of chromophores
Authors: Lloyd D. G.
Published: April 2003

The ultraviolet spectra of aqueous solutions of polyvinyl alcohol have been examined with a view to identifying the chromophores present. The spectrum may be modified by reduction with hydrogen over Raney nickel at room temperature, which is specific for ethylenic unsaturation, and by reduction with sodium borohydride, which is specific for carbonyl groups. An analysis of the resulting spectra supports the proposal that the ultraviolet absorption of aqueous polyvinyl alcohol solutions arises from polyene‐carbonyl chromophores of empirical formulas: (CHCH)nCO, where n may vary from 0 to 3.
The relationship between structure and properties of crystalline, high‐melting polyhydrocarbons
Authors: Campbell Tod W. , Haven A. C.
Published: April 2003

Twenty‐two α‐olefin monomers with varying degrees and types of branching in the lateral group have been polymerized and the polymers characterized. In general, the closer the branching in the side chain is to the polyethylene trunk, the higher the degree of crystallinity and the crystalline melting point. The degree of branching and the symmetry of the branches also affects the melting point and crystallinity markedly. Relationships have been drawn between type and position of the branch and melting point.
The aging of thiuram disulfide vulcanizates and their mechanism of vulcanization
Authors: Dunn J. R. , Scanlan J.
Published: April 2003

The aging of sulfurless tetraalkylthiuramdisulfide vulcanizates has been studied by the stress‐relaxation technique, the general behavior being independent of the nature of the alkyl group. The aging in air at 100°C. of fully cured vulcanizates is excellent before acetone extraction but rapid after it, due to removal of zine dialkyldithiocarbamates which are powerful antioxidants. In undercured vulcanizates, the network breakdown at 100°C. after extraction is much less than in fully cured samples, and there is considerable crosslinking during the aging. This behavior is attributed to the presence of a vulcanization intermediate which, at 100°C., brings about crosslinking with formation of zine dialkyldithiocarbamate and which cannot be removed by acetone extraction. The presence of such an intermediate is confirmed by the ability of extracted undercured thiuram vulcanizates to be further crosslinked in the press at 140°C. Previous theories regarding thiuram vulcanization are discussed in the light of these observations. The rapid initial relaxation of unextracted undercured vulcanizates may be due to the breakdown of this vulcanization intermediate. During the thermal aging of apparently fully cured samples, some crosslinking occurs which is considered to be due to a direct oxidative reaction of dithiocarbamates. Unextracted thiuram vulcanizates degrade very little on illumination with ultraviolet light (wavelength 365 mμ), but, after extraction, the photolytic aging becomes more rapid. There is no variation in the rate of this type of aging with degree of cure, presumably because the vulcanization intermediate is light stable.
Orientation in extruded polyethylene films
Authors: Aggarwal Sundar L. , Tilley George P. , Sweeting Orville J.
Published: April 2003

A discussion of the methods for studying orientation of crystalline and amorphous regions in polyethylene films is given. Extruded polyethylene films and films after having been stretched approximately 200% were studied by the methods of x‐ray diffraction and absorption of polarized infrared radiation. It is shown that in extruded polyethylene films the a‐axes of the crystallites are oriented parallel to the extrusion direction. The amorphous regions in these are either not oriented or show only to a slight degree the orientation of chains perpendicular to the extrusion direction. When the polyethylene films are stretched, both the crystallites and the amorphous regions become oriented. In stretched films, the orientation of the crystallites is with c‐axis parallel to the stretching direction, and the chains in the amorphous regions are also oriented parallel to the stretching direction. Two mechanisms by which a‐axis orientation may arise during extrusion of polyethylene films, and a convenient method for determining the relative degree of a‐axis orientation in polyethylene films are given. The relative degrees of a‐axis orientation as determined by x‐ray diffraction and dichroism of absorption at 13.70 μ are compared for a number of film samples.
Mastication of rubber. VII. Mechanical degradation of polymers during mastication
Authors: Ceresa R. J. , Watson W. F.
Published: April 2003

The degradation on mastication of polymers brought into a rubbery state by incorporation of liquids or rise in temperature is accounted for by the mechanicochemical mechanism previously advanced to explain the degradation of rubbers. The dependence of the reaction on shear rate has been shown indirectly, as with rubbers, by the negative temperature coefficient of reaction, and also directly by variation of masticator rotor speed and design. A further new feature is the influence of the nature as well as concentration of plasticizer on the rate of degradation and a correlation with the softening of the polymer. A limiting molecular weight is reached on prolonged mastication from whatever initial molecular weight.
The deformation of foamed elastic materials
Authors: Gent A. N. , Thomas A. G.
Published: April 2003

A theoretical treatment is given which predicts the behavior of a foamed elastic material on the basis of a model consisting of a network of thin threads. Two cases are considered: (1) small strains, and (2) finite compressions, when the major part of the deformation of the threads is attributed to buckling. The behavior is given in terms of Young's modulus of the matrix and the density of the foam. Measurements of the load‐deformation relations for small tensile strains and finite compressions are described for natural rubber foams prepared from latex. A wide range of density is covered (0.09–0.57), giving a variation of compression hardness of about 100:1. Satisfactory agreement with theory is found for both the cases considered, indicating that the basic concepts of the structure and mode of deformation are correct.
Thermal expansion measurements and transition temperatures, first and second order
Authors: Dannis Mark L.
Published: April 2003

Transitions in polymers have been studied with the use of a differential expansion apparatus modified from a design described by K. L. Floyd. Materials ranging from uncured, soft rubbers to hard, waxy solids have been studied from above room temperature down to liquid air temperatures. Both the first‐order transition temperature, Tm and the second‐order transition temperature, Tg, can be identified. Multiple changes in slope of the expansion curves indicate the possibility of additional second‐order transitions. Expansion curves for several diene rubbers are presented, illustrating typical transition phenomena. Expansion curves for several polyolefin materials are presented which illustrate changes in Tg and in the low temperature expansion coefficient with changes in the structure of the polymer.
Resistance to ozone cracking in elastomer blends
Authors: Andrews E. H.
Published: April 2003

The phenomenon of ozone cracking has been investigated for elastomer blends containing an ozone‐reactive phase (natural rubber) and an ozone‐inert phase (ethylene–propylene rubber). Electron microscopical studies reveal phase separation in the blend and the locus of ozone attack. Ozone cracks traverse the reactive phase and occasionally jump across inert particles without severing them. This mechanism provides the basis of a theory which correctly predicts the dependence of both the critical stored energy for ozone cracking and the crack density upon the blend composition.
Diffusion of liquids in cellulose membranes
Authors: Arnowich B. , Carangelo S.
Published: April 2003

Diffusion of small quantities of liquids in porous polymeric substrates has been studied by means of a radiotracer technique. The procedure has been applied to the permeation of five different types of paper stock by ethylene‐1,2‐C14 glycol. Data obtained indicate that under the experimental conditions the diffusion analogy is valid for solvent penetration in the systems studied. The method should have general applicability to studies of diffusion rates in cellulosic and other membranes and to investigations where only small quantities of diffusant are available.
The steady flow shear modulus of polymer melts
Authors: Blyler L. L. , Huseby T. W.
Published: April 2003

Relaxation times of polyethylene melts have been measured by Aloisio, Matsuoka, and Maxwell. One implication regarding their observations is that the elastic properties of polymer melts must be time‐dependent. In particular, the steady‐flow shear modulus depends on the strain rate. Some interpretations of data in the literature have been based on concepts in rubber elasticity where the steady‐flow modulus is an equilibrium value, independent of strain rate. We have used Pao's theory for viscoelastic flow together with measurements of relaxation times to discuss the strain rate dependence of the steady‐flow shear modulus of melts. The existence of a strain rate‐dependent shear modulus leads naturally to a nonlinear relation between shear stress and recoverable shear strain. The conclusions regarding the molecular weight dependence of the modulus also differ from interpretations based on rubber elasticity.
Emulsion polymerization of ethylene. III. Factors affecting the stability of polyethylene latexes
Authors: Stryker Harry K. , Helin Arthur F. , Mantell Gerald J.
Published: April 2003

A semiquantitative method for assessing the amount of visible solid matter in polyethylene latexes is described. As judged by this method and by the presence of particles larger than 50 μ, the stability of the latexes was related to (1) the type and concentration of post‐emulsifier added to the latex, (2) the average size of the polymer particles, and (3) the concentration of solids. Generally, the appearance was better when the latexes had a low (30%) concentration of solids, a large (800 A.) average particle diameter, and enough post‐emulsifier to cover most of the polymer surface. Specific samples, however, having a high (36%) concentration of solids and a small (300 A.) average particle diameter also showed good storage stability. According to tests on selected latexes, good resistance to coagulation by mechanical shear was obtained only if the surface of the polymer was completely covered with emulsifier. When polyethoxylated alkylphenols were used as post‐emulsifiers, an inverse relation appeared to exist between latex stability and average number of ethylene oxide units per emulsifier molecule. Moreover, the addition of each ethylene oxide group increased the apparent area of the emulsifier molecule by about 4 A.2
Thermally induced solid‐state polymerization in nylon 66
Authors: Griskey Richard G. , Lee Byong Il
Published: April 2003

The thermally induced solid‐state polymerization of 66 nylon was investigated. It was found that the rate‐controlling step in the process is chemical reaction. A mechanism of the form, rate = ktn was shown to hold. The reaction rate constant was found to be k = 1.53 × 1010 exp [ − 12,960/RT]. Units of k are (hours)−0.51. Activation energy determined in this work compared closely to that determined for nylon 6 solid‐state polymerization.
Application of the theory of elasticity and viscosity of two‐phase systems to polymer blends
Authors: Uemura Shinsaku , Takayanagi Motowo
Published: April 2003

An attempt was made to evaluate the apparent elastic constant of a two‐phase system G from those of the components of the system. The modulus G is expressed as follows:

where G1 and G2 are the shear moduli of the suspending medium and the suspended particles, respectively, v1 is the Poisson ratio of the medium, and v is the volume fraction of the particles. The results for modulus were extended to dynamic viscoelasticity by the corresponding principle. Experimental verifications with dynamic viscoelasticity data were conducted for the system of styrene‐acrylonitrile copolymer interpolymerized with polybutadiene particles. For shear viscosity comparisons with experiment were made for the system linear polyethylene‐polybutene‐1.
Radiation‐induced graft copolymerization of butadiene to polyethylene and polypropylene
Authors: Furuhashi Akira , Kadonaga Masao
Published: April 2003

Polyethylene and polypropylene films were irradiated by γ‐irradiation from a Co60 source in butadiene gas flow and in liquid butaidne. Irradiating in the butadiene gas flow is particularly convenient because the gas state monomer is available directly and little homopolymer is produced. In this case, there is a retardative effect on the grafting near the surface of the film and the grafting rate shows the maximum values at 50–60°C. for high‐density PE (PEH) and PP. Irradiating in the liquid butadiene decreases the retardative effect near the surface. The effect of dose rate I on the grafting rate Rp is represented by Rp ∞ I1/4 in this case. The grafting rate is always higher in PEH than in low‐density PE (PEL). Results of x‐ray diffractometry and electron microscopy indicate that the grafting reaction occurs predominantly near the surface of the crystallite (lamella) of PE and the grafting rate is not affected by the overall crystallinity of the trunk polymer but by the configurational structure, such as the degree of branching or side‐chain length.
Physical and electrical properties of polyethylene radiation crosslinked via polyfunctional monomers
Authors: Bernstein Bruce S. , Odian George , Binder Sidney , Benderly Asaf A.
Published: April 2003

The radiation crosslinking (via Co60) of both high and low density polyethylene in the presence of several tetrafunctional monomers has been studied to observe the effects of the additives on mechanical and electrical properties. The monomers employed were allyl methacrylate, divinylbenzene, and diallyl maleate. Monomer levels were such that the number of moles presented per number‐average mole of polyethylene was 2.2–2.6 for AMA and DVB with Marlex 5003 and 6009, and 9–10 for Marlex 1712. The DAM level was 3–5% of that of the other monomers on the same basis. Gel fractions, tensile strengths (at yield and break) at ambient temperature and tensile strengths, elongations, and moduli measured at a temperature above which no crystallinity remains all undergo more marked changes in the presence of tetrafunctional monomer after only 1–3 Mrad of radiation, regardless of monomer nature. Gels, tensiles, and moduli increase while elongation decreases. The magnitude of the changes depends upon the monomer nature (at the above ratios), the order being AMA>DVB>DAM> Monomer‐free. With increasing does to 8 Mrad, the trends continue. The gel swelling ratios are inversely proportional to the 3/5 power of the crosslink density, as determined by the modulus value in the absence of crystallinity. Straight radiation of monomer‐free polyethylene to higher doses not necessarily yield physical properties values attained at the lower doses with additive. The dielectric constant and dissipation factor of monomer‐containing crosslinked polyethylene are only slightly affected by the presence of the polyfunctional monomer.
Influence of polymer solubilization on latex behavior
Authors: Isaacs P. K. , Edelhauser H. A.
Published: April 2003

The effect of solubilization of latex polymers was investigated in various anionic surfactant solutions. The process of solubilization was studied by measuring the increase in light transmission and viscosity of the latexes. It was found that anionic surfactants differ widely in their ability to solubilize a given polymer, and susceptibility to solubilization is significantly affected by comonomer content of the polymer. If, for example, a poly(vinyl acetate) latex is stabilized exclusivdly by a strongly solubilizing sodium dodecyl benzene sulfonate, it is less stable and hydrolyzes faster than a similar latex made with a polyoxyethylene derivative, which has only a slight solubilizing action. Dibutyl mateate copolymers of vinyl acetate are less susceptible to solubilization than hompolymers of vinyl acetate.
Permeation of water through some heterogeneous hydrophilic membranes
Authors: Refojo Miguel F.
Published: April 2003

The permeation of water through glyceryl methacrylate (2,3‐dihydroxypropyl methacrylate) and 2hyphen;hydroxyethyl methacrylate hydrogels was increased by the incorporation of silica fillers. Both the amount of water at equilibrium and the amount of filler in the gel contribute to increase the permeability of these membranes.
Thermal degradation of polymers. Part I. Thermogravimetric and differential thermal analysis studies of atactic poly‐m‐aminostyrene and related polymers
Authors: Still R. H. , Keattch C. J.
Published: April 2003

Thermogravimetric and differential thermal analysis have been employed to study the thermal degradation patterns of poly‐m‐aminostyrenes and poly‐m‐acetamidostyrenes of different molecular weights and also the corresponding 2:1 copolymers with styrene. The thermal degradation routes have also been compared and contrasted with that of polystyrene. Experiments have been carried out in static air and dynamic nitrogen, and the different behavior exhibited by these polymers has been reconciled in terms of their differing structures and different mechanisms for pyrolytic degradation.
Pressure–volume–temperature behavior of high density polyethylene
Authors: Foster George N. , Waldman Nathan , Griskey Richard G.
Published: April 2003

Equilibrium pressure‐volume‐temperature behavior in both the solid and molten regtions was determined for a high density (ρ = 0.958 g./cm.3) polyethylene. Data were measured with a recently developed compressibility device capable of obtaining precise and accurate data. Residual curve treatment showed that the data were true equilibrium data. Compressibilities calculated from the data of this Work compared favorably to existing data which were limited to 205°C. The presented work extended the compressibility behavior to 250°C. It was also found that differences in compressibility of low and high density polyethylenes were not eliminated. in the molten region, indicating that the effect of differences in morphology was not eliminated. The Spencer‐Gilmore equation was fitted to the data of the present work. The internal pressure (π) term of the equation showed a definite relation to polymer morphology.