bluuebunny/crossref_metadata_2025 huggingface dataset:
Molecular weight distribution of PVC blends from resins with different K values
Authors: Pepperl G.
Published: April 2004

The molecular weight distribution (MWD) of blends of commercial suspension grade PVC resins with different molecular weights (MW) or K values is calculated. If the K‐value difference is not too high, the polydispersity of the blend is only slightly increased as compared to those of the components. It is not possible to get bimodal MWDs by blending. Additionally, a model calculation of mean molecular weights has been performed for temperature‐programmed polymerization. On the basis of the most realistic model, which takes into account the increasing polymerization reaction rate with increasing temperature and increasing conversion, it can be predicted that a linear temperature program will give a product corresponding to an isothermal resin polymerized at a temperature near the high end of the temperature program and showing only a slightly increased polydispersity.
High‐molecular‐weight flexibilizers in low‐smoke flame‐retardant PVC compounds
Authors: Griffin E. R.
Published: April 2004

Ethylene copolymer resin (ECR) modifiers play an important role in low‐smoke PVC. As high‐molecular‐weight flexibilizers, these resins reduce smoke and add strength and low temperature flexibility. This combination allows compounders to increase the amounts of flame‐retardant additives without compromising strength or flexibility or by adding liquids which increase smoke. This paper demonstrates these attributes versus liquid plasticizers used in PVC compounds.
Influence of various molding conditions on the uni‐, bi‐, and triaxial impact properties of poly(vinyl chloride) (PVC)
Authors: Elleithy Rabeh H. , Abu‐Ali Amjad , Harrell E. Ray , Summers James W.
Published: April 2004

This study discusses the influence of molecular weight, melt temperature, mold temperature, and aging on the impact characteristics of molded PVC. Tensile impact (uniaxial), instrumented drop‐dart impact (biaxial), and Izod impact (triaxial) methods were utilized to assess the impact properties of the material under investigation. It was found that the impact properties were affected by aging more than by the changes in the melt temperature or the mold temperature. Additionally, the molecular weight played a significant role in influencing the impact properties of PVC.
Effect of combining boron nitride with fluoroelastomer on the melt fracture of HDPE in extrusion blow molding
Authors: Yip Franky , Diraddo Robert , Hatzikiriakos Savvas G.
Published: April 2004

Boron nitride (BN) is a new polymer processing aid which not only eliminates surface melt fracture in the extrusion of molten polymers, but also postpones the critical shear rate for the onset of gross melt fracture to significantly higher values that depend on resin type and additive concentration. In this work, the influence of BN as a polymer processing additive is first examined in the extrusion blow molding of high‐density polyethylene (HDPE) resins in order to evaluate its usefulness and performance in operations other than continuous extrusion. The equipment used includes both a Battenfeld/Fisher 50‐mm extrusion blow molding machine and a parallel‐plate rheometer. Two types of HDPE, which are blended with boron nitride at various concentration levels, are tested accordingly. It is found that the degree of BN dispersion, characteristics of the HDPE resins, extrusion temperature, and induction time play an important role in eliminating melt fracture. Finally, the influence of combining BN with fluoroelastomer, as an enhanced and potentially better processing aid on the melt fracture of a third HDPE is examined. It is found that such a combination is a superior processing aid that allows extrusion blow molding at very high shear rates.
Cross‐Linking of polystyrene by friedel‐crafts chemistry: Multifunctional additives
Authors: Yao Hongyang , Zhu Jin , McKinney Michael A. , Wilkie Charles A.
Published: April 2004

Various multifunctional aromatic compounds were synthesized and tested to ascertain if they were able to cross‐link polystyrene. Catalysis and inhibition at high temperature were studied to achieve control over the cross‐linking temperature, in order to develop suitable formulations which may function as flame retardants.
Thermoset/(Thermoplastic elastomer) blends: Epoxy/EVA
Authors: Siddhamalli Sridhar K.
Published: April 2004

Phase separation behavior and phase morphology of mixtures of methylene dianiline (MDA)‐cured diglycidyl ether of Bisphenol A (DGEBA) epoxy oligomer and 0–30 wt % of ethylene‐(vinyl acetate) copolymer (70% vinyl acetate content) were investigated by means of small angle light scattering (SALS), optical microscopy, and scanning electron microscopy (SEM). Epoxies with EVA modified were also characterized by tensile, flexural, thermal, and hardness properties. Epoxy/EVA blend compositions, during isothermal curing, showed a ring pattern of light scattering, an increase of intensity, and a shift of peak angle to smaller scattering angle, all of which are hallmarks of spinodal decomposition. Optical microscopy studies revealed a two‐phase structure with unique periodicity and phase connectivity. Physical property measurements indicated that there was no toughening achieved by EVA modification of epoxy, and this result was explained with morphological information obtained by SEM.
Effect of curprous oxide in combination with molybdenum trioxide on smoke suppression in rigid poly(vinyl chloride)
Authors: Li Bin , Wang Jianqi
Published: April 2004

Further investigation of the synergistic effect of smoke suppression between cuprous oxide and molybdenum trioxide in rigid poly(vinyl chloride) (PVC) was carried out by using a cone calorimeter (cone) at a high incident heat flux of 50 kW m−2. Experimental data derived from the cone calorimeter indicated that binary mixtures of Cu2O and MoO3 clearly showed the synergistic effect in reducing smoke by decreasing total smoke production (TSP), average specific extinction area (av‐SEA), and smoke production rate (SPR). This result is in good agreement with that obtained from the NBS smoke chamber. However, the combustion process of rigid PVC could clearly be seen from the heat release rate (HRR), curve, SPR, and fire degradation obtained from the cone test, which could not be determined from the NBS smoke chamber. It was also found that the binary mixture showed the synergistic effect by increasing was also found that the binary mixture showed the synergistic effect by increasing char residue and reducing the fire degradation of the PVC backbone at a high incident heat flux of 50 kW.m−2. All experimental data well supported the early cross‐linking mechanism of the PVC backbone mentioned in the literature and were consistent with the fire degradation behavior obtained from the cone calorimeter.
Effect of various acid neutralizers on the crystallization temperature of nucleated polypropylene
Authors: Dieckmann Dale
Published: April 2004

Polypropylene is often nucleated with sodium benzoate in order to raise its crystallization temperature (TOC). Conventional wisdom holds that calcium stearate is detrimental to TOC elevation because it chemically interacts with the sodium benzoate. This paper examines the effect of calcium stearate, sodium stearate, calcium lactate, and other substances on the TOC of nucleated polypropylene. We have found a definite effect on TOC elevation that correlates with neutralizer type. However, we find little evidence of chemistry occurring directly between neutralizer and nucleator.
Printing on vinyl—part II. FTIR and TOF‐SIMS studies
Authors: Burley Joseph W.
Published: April 2004

Earlier surface analysis studies have suggested that, at least in some situations, the print adhesion properties of barium/zinc stabilized, stearic acid‐lubricated PVC are influenced by the migration (exudation) of a barium/zinc stearate complex. This paper expands the previous study in attempts to reproduce the effects observed on samples of commercially produced films, explain the origin of the migrating specie, and identify the variables that influence the extent to which the phenomenon occurs. The effects of different lubricants, stabilizers, and processing conditions are studied. Mechanistic work suggests that a revised hypothesis is appropriate and that the hydrolyzed complex is actually formed in the PVC matrix and not at the surface.
Combustion products of lead stabilizers. 2: Dibasic lead phosphite
Authors: Grossman Richard F.
Published: April 2004

The volatile products of combustion of dibasic lead phosphite in air were found to contain water with traces of acetic acid. In the absence of air, phosphine is the principal volatile decomposition product.
New opportunities with wood‐flour‐foamed PVC
Authors: Patterson John
Published: April 2004

Composites of wood with polyethylene, polypropylene, and poly(vinyl chloride) represent an emerging class of materials that combine the favorable performance and cost attributes of both wood and thermoplastics. One of the major disadvantages, however, of these materials is a relatively high specific gravity compared with those of many natural wood products. A PVC‐wood composite, for example, has a specific gravity of about 1.3 g/cc. This paper looks at producing cellular PVC‐based wood composites and the properties that are achieved as the foam density is reduced. Overall, even with densities as low as 0.6 g/cc, the physical properties should be adequate for many wood replacement applications. The composites also offer the aesthetics of wood and economics that are favorable compared to those of both rigid and cellular PVC.
Study of PVC degradation using a fast computer scanning procedure
Authors: Bacaloglu Radu , Stewen Ulrich
Published: April 2004

A computer scanning procedure for the determination of total double‐bond concentration resulting from PVC degradation is described. It is fast, fully automated, and has a very high sensitivity (5 ppm of degraded monomer units). This high sensitivity makes possible the monitoring of discoloration on a very small surface and generates very large amounts of experimental data allowing corrections for inhomogeneities and surface irregularities. The measured extinctions (Ergb) correlate with the concentrations of double bonds and allow the estimation of degradation rates. The measuring of stabilization times and the reaction rates of stabilizers with allylic chlorides and HCI offers the capability to optimize the PVC stabilization.
Computational simulation of poly(vinyl chloride) reduction with tri‐n‐butyltin hydride. The use of revised rate constants
Authors: Knudson S. K. , Starnes W. H.
Published: April 2004

The computer simulation of the reductive dechlorination of poly(vinyl chloride) (PVC) with Bu3SnH is reexamined by using a new set of rate constants that has been corrected (a) statistically for the presence of different numbers of chloro substituents and (b) for a triad reactivity factor used to determine the constants for rr‐and mm‐VVV triads from that for mr‐VVV triads. The simulation method is verified by comparison with analytic kinetic results for the reduction of 2,4‐dichloropentane and 2,4,6‐trichloroheptane model compounds. The revised rate constants should and do lead to a smaller ratio of racemic to meso diads in PVC as reaction nears completion, compared to the ratio obtained from the original set of rate constants that had been proposed by previous workers. Experimental data are not sufficiently accurate to distinguish between the two sets of simulation results.
Identification, quantitation, and qualification of PVC multifunctional systems with near‐infrared spectroscopy and chemometrics
Authors: Garcia Dana , Borden Farrel , Bouveresse Eric
Published: April 2004

Multifunctional systems (MFS) comprising impact modifiers, processing aids, lubricants, stablizers, and fillers are utilized throughout the PVC industry to impart greater consistency, obtain faster and easier blending cycles, reduce inventory, and minimize cross‐contamination. Qualitative and quantitative product analysis, to ensure adherence to performance specifications, is an integral part of any quality control function. Near‐Infrared (NIR) spectroscopy coupled with chemometrics techniques enables one to distinguish clearly among different MFS formulations (product identification) and to detect changes in product composition for each formulation (product qualification). Additionally, models can be developed to provide a completed compositional analysis.
Photostabilization of poly(vinyl chloride) by protective coatings
Authors: Decker Christian
Published: April 2004

The light stability of poly(vinyl chloride) plates has been substantially increased by protecting their surface with a UV‐cured acrylic clearcoat containing both a UV absorber and a HALS radical scavenger. To ensure a long‐lasting adhesion, the coating was photochemically grafted onto the PVC substrate. The coated PVC sample remained transparent, non‐colored, and glossy upon accelerated QUV‐B weathering for up to 3000 hours. An additional advantage of this method of photostabilization is to improve some of the surface properties of the coated polymer, such as its resistance to solvents, abrasion, and scratching. The method was also successfully used to recover highly photodegraded PVC and make it even more weathering‐resistant than the original polymer.
Gamma‐radiation‐induced graft copolymerization of N‐[4‐(N′‐substituted amino carbonyl)phenyl] maleimide onto poly(vinlyl chloride) films
Authors: Abdel‐Naby Abir S.
Published: April 2004

Three types of N[4‐(N‐substituted amino carbonyl)phenyl] maleimide (RPhMI:N‐substituent (R) = phenyl, cyclohexyl, p‐chlorophenyl) were grafted onto poly(vinyl chloride) (PVC) films by using gamma irradiation. The effects of different parameters on the graft yield were investigated. These parameters included radiation dose and monomer concentration. Thermal properties of the grafted polymer were investigated by the determination of dehydrochlorination rate, thermal gravimetric behavior, and UV stability.
Thermal stabilization of PVC by “plasticizer thiols”
Authors: Starnes W. H. , Du B. , Zaikov V. G.
Published: April 2004

Various new carboxylate esters containing one or more sulfhydryl groups are shown to be remarkably effective as both thermal stabilizers and plasticizers for poly(vinyl chloride) (PVC). These “plasticizer thiols” function well as primary stabilizers in the absence of metal‐containing additives when they are introduced at either a typical plasticizer level or a conventional stabilizer level. Their syntheses are straightforward and, in some cases, require only an acid‐catalyzed esterification performed with commercially available starting materials. Unlike typical thiols, the purified plasticizer thiols do not have offensive odors when their molecular weights are relatively high.
Zinc stannate–coated fillers: Novel flame retardants and smoke suppressants for polymeric materials
Authors: Cusack P. A. , Hornsby P. R.
Published: April 2004

Novel zinc hydroxystannate‐ or zinc stannate‐coated hydrated fillers are shown to be highly effective flame‐retardant and smoke‐suppressant additives for chlorinated polymers. The performance of these systems is discussed, with reference to PVC, polychloroprene, halogenated polyester resin and polypropylene formulations. Relative to unmodified magnesium hydroxide and alumina trihydrate, coated variants of these fillers can achieve similar fire‐retardant properties at significantly lower additive levels.
Study of the processability of commercial PVC plastisols by rheology
Authors: García‐Quesada J. C. , Marcilla A. , Beltrán M.
Published: April 2004

A qualitative model that satisfactorily explains the rheological behavior of PVC plastisols during gelation and fusion is shown. Several industrial production cases have been analyzed, and the rheological characterization of the corresponding plastisols during gelation and fusion processes has proved to be a valuable technique to improve the knowledge and understanding of the industrial rotomolding process.
Mechanism of organotin stabilization of poly(vinyl chloride). 1: The structure and equilibria of alkyltin thioqlycolates and their compatibility with PVC
Authors: Fisch Michael H. , Bacaloglu Radu , Biesiada Keith , Brecker Lawrence R.
Published: April 2004

A series of alkyltin thioglycolates was synthesized and their structure and equilibria with alkyltin chlorides studied by infrared analysis. Dynamic mechanical analysis was used to determine their compatibility with PVC. The implications of these results on PVC stabilization were discussed
Statistical experimental design to optimize formulations for foam vinyl applications
Authors: Thomas Noreen L. , Harvey Ray
Published: April 2004

Statistical experimental design has been used to study the effects of blowing agents, processing aids and fillers in rigid vinyl foam formulations. It is shown how this approach provides information about interactions between variables and can be used to help to predict an optimum formulation.
Effects of formulation variables on rheology of rigid PVC
Authors: Hayes Virginia Odle
Published: April 2004

The effects of lubricants, impact modifier, and process aid on the processing and physical properties of a rigid PVC compound have been modeled using a central composite designed experiment. Capillary rheology was used to evaluate the flow properties of the various formulations in the study. By modeling the rheological properties it is possible to optimize simultaneously the flow, extruder conditions, and final part properties.
Phenomenon of color change in colored poly(vinyl chloride) compound
Authors: Kann Yelena
Published: April 2004

This paper addresses a phenomenon of color shift found during the development of a colored poly(vinyl chloride) (PVC) compound for exterior automotive application containing, among other pigments, red anthraquinone (C.I. Pigment Red 177) and titanium dioxide (TiO2). Color was found to shift about 2 points delta b* on a CIELAB scale from yellow to blue during the first one month and a half since the compound had been processed. The shift took place at the regular conditions: room temperature with no exposure to sunlight or heat.
Performance of Di‐n‐Hexyl phthalate in flexible vinyl formulations
Authors: Kozlowski Richard R. , Gallagher Thomas K.
Published: April 2004

Low‐molecular‐weight esters have been available to the PVC compounder for many years. They have found a significant niche in the performance vs. permanence compromise as a compound ingredient that provides manufacturing efficiency or some special property with adequate permanence for many vinyl applications. In many respects, low‐molecular‐weight esters are the processing aids of the plasticizer family. This group of plasticizers may be said to include C4 to C7 dialkyl phthalates, the benzyl phthalates and the benzoic acid esters. This paper will introduce and compare di‐n‐hexyl phthalate (DNHP) to other phthalates against which it will directly compete.
Prediction of plasticizer solvency using hansen solubility parameters
Authors: Krauskopf Leonard G.
Published: April 2004

The solvating strength of a plasticizer for poly(vinyl chloride) resin is a measure of the interactive forces between these two materials. Hansen's three‐dimensional solubility parameters provide a quantitative measure of these interactive forces. By using CO‐ACTSM service, a computer program designed for solvent systems with various resins, plasticizers were found to lie near the edge of the solvency “sphere” of PVC. The relative positions of various plasticizer structures are in the expected order, while known solvents show strong association and lubricating additives fall outside the solvency sphere of PVC.
Initial mechanisms of dispersion of core‐shell impact modifiers in a polymer matrix
Authors: Scott Chris E. , Rockford Lee D.
Published: April 2004

Core‐shell impact modifiers are effective toughening agents for many thermoplastics. In order to achieve optimum performance, agglomerates of these particles must be dispersed and the individual submicron particles well distributed within the polymer matrix. The focus of this paper is a description of the initial mechanisms of dispersion during compounding of core‐shell impact modifiers into polymer matrices. Model experiments were conducted with acrylic‐based modifiers in a poly(methyl methacrylate) matrix by using a batch intensive mixer. Based on the observed morphologies at numerous mixing times, a qualitative description of the mechanism is developed. Significant structural changes occur in all three of the classical processing regimes: solids conveying, melting, and melt flow. Differences in the form of modifier addition, pellet or powder, are explored. The degree of fill of the mixer is found to have a critical effect on the dispersion mechanism.
The effect of lubricants on processing—part I. detection by PVC melt flow
Authors: Riley David W.
Published: April 2004

For decades it has been recognized that one can detect molecular structural changes in the processing of PVC by using ASTM D 3364 [PVC Melt Flow Test]. In the course of this work, we also realized that this Melt Flow Test could detect small changes in the ingredients as well. Through a special design of experiment, the effect of three lubricants on extrusion of dry blends of PVC (with and without calcium stearate) has now been investigated. The effects of extrusion on extruded pellets have also been studied as part of this design. To detect the changes in lubricity, the techniques of ASTM D 3364 have been modified to include new higher pressures on the ram as well as other revisions. This report shows how the various lubricants at differing concentrations and types can alter the PVC Melt Flow Test results and imply differences in processing.
Recent developments: Benzoate esters in polyvinyl resilient flooring
Authors: Bohnert T. , Izadi R. , Pitman S. , Stanhope B.
Published: April 2004

Benzoate plasticizers provide excellent foam quality, stain resistance, and UV light stability. They are used as primary plasticizers in resilient flooring applications but are limited in use because of viscosity. New benzoate‐based blends have been developed that result in reduced‐viscosity plastisols and lower VOC emissions than for existing benzoate products. A variety of European and North American formulations have been used to evaluate the processing and performance properties of these benzoate‐based blends and are highlighted in this paper.
Effect of iron compounds (oxide, salt, or complexes) on poly(vinyl chloride) thermal and photochemical stability
Authors: Girois Stephane
Published: April 2004

The color requirements for vinyl siding have drastically evolved over the last decade and have moved toward medium to dark colors. Therefore, manufacturers are exploring new ways to modify their formulations in order to improve weather‐ability of these challenging colors. Examination of some of the PVC additives typically used in these formulations has led to some interesting revelations about the performance of iron‐containing pigments, which are extensively used in darker colors. A quick weathering test was designed to evaluate the effect of iron in PVC formulations, and this test clearly demonstrates the correlation between iron content and PVC photodegradation.
Chemical coupling of polypropylene systems containing nonglass fillers
Authors: Roberts Darilyn H.
Published: April 2004

Maleic anhydride (MAH) modified polypropylene (PP) was demonstrated to be a chemical coupling agent in filled PP compounds. Improved properties were shown for talc and wollastonite filled PP compounds with MAH modified PP as a coupling agent. Partial replacement of glass fiber with wollastonite showed no reduction in properties.
The effects of filler size on the properties of thermoplastic polyolefin blends
Authors: Wong Tony L. , Barry Carol M. F. , Orroth Stephen A.
Published: April 2004

The effects of filler size on the properties of a thermoplastic polyolefin (TPO) blend were examined by using wollastonite and talc with particle sizes ranging from 1.2 to 40 μm. While addition of filler produced significant changes in the mechanical properties of the blend, filler size affected only impact strength. However, filler size, filler coating, and injection speed had a major effect on the surface properties of the blend. Faster injection produced denser “shear zone layers” which exhibited better scratch resistance and poorer paint adhesion than those obtained with slower injection. Scartch resistance and paint adhesion also decreased with increasing filler particle size. Filler coatings altered the scratch and adhesion properties of the polypropylene (PP) blends.
Role of processing aids in the extrusion of molten polymers
Authors: Achilleos E. C. , Georgiou G. , Hatzikiriakos S. G.
Published: April 2004

Product quality and, in general, processing windows and rates of production in the extrusion of molten polymers are limited by various flow instabilities (mainly melt fracture) that are observed at high production rates. While there still are unresolved issues in comprehending these phenomena, industry demands for process optimization dictate the employment of processing aids (PAs) for product quality improvement and energy requirement reduction. In this review paper, most commercially used processing aids (PAs) are discussed, namely, fluoroelastomers, stearates, small amounts of polymers blended with the process polymer, and the newly discovered boron nitride as pure and in combination with other fluoroelastomers. This paper focuses on the appropriate and optimum usage of the various PAs as well as on the mechanism that underlies their action for flow enhancement and instability elimination. Finally, numerous experimental observations are discussed, and several examples are illustrated.
Influence of atmospheric pollutants on the natural and artificial aging of rigid poly(vinyl chloride)
Authors: Belhaneche‐Bensemra Naïma
Published: April 2004

The natural aging of rigid poly(vinyl chloride) (PVC) used in building and construction areas has been studied. Bars of PVC exposed in Algiers, where the concentrations of atmospheric pollutants (NOx, O3, hydrocarbons) are known, show a small drop in strain at break and stress at break, whereas hardness remains practically constant. Analysis by IR and UV‐visible spectroscopy shows the appearance of chemical structures due to polymer degradation (carbonyl groups, hydroperoxide groups, and polyenes) after the first months of exposure at three sites. It seems that O3 exerted the most deleterious effect, followed by hydrocarbons and then by NOx. An artificial aging test was carried out to investigate the effect of O3 on the degradation of PVC, and the results were compared to those from outdoor aging.
Phosphite ester compositions for PVC compounds
Authors: Stevenson Don R. , Harr Mark E. , Jakupca Michael R.
Published: April 2004

The activity of various structural classes of liquid organophosphite esters has been examined in flexible PVC applications. Blends of the most active phosphites have been developed as alternative heat stabilizers for PVC. These new phosphite mixtures eliminate the dependence of compounders upon mixed‐metal stabilizer systems based on heavy metals such as barium and cadmium. Static oven aging tests showed the superior performance of these blends compared to that of traditional mixed‐metal stabilizers.
Effect of boron nitride on melt fracture phenomena and processability of lldpe during extrusion
Authors: Lee Sang Myung , Kim Jung Gon , Lee Jae Wook
Published: April 2004

Melt fractures related to processing instabilities limit processing rates in many commercially important polymer processing operations, such as fiber spinning, film blowing, extrusion, and various coating flows. Therefore, melt fracture is responsible for deteriorating the quality and the mechanical properties of final products for rates greater than a critical processing one at which melt fracture occurs. In this study, a commercial linear low‐density polyethylene (LLDPE) was modified by adding a small amount of boron nitride (BN) during extrusion in order to improve processability. Capillary rheometry was used to assess processability at various temperatures, levels of applied shear rate, and the length‐to‐diameter (L/D) ratio for both the pure resin and resins containing boron nitride. Also, parallel‐plate rheometry was used to evaluate the dynamic rheological properties of these resins. The relationship between the characteristic relaxation time and the critical shear rate for the onset of melt fracture and slip is discussed.
Melt blending preparation of PVC‐sodium clay nanocomposites
Authors: Wang Dongyan , Parlow Daniel , Yao Qiang , Wilkie Charles A.
Published: April 2004

Poly(vinyl chloride) (PVC)–clay nanocomposites were prepared by melt blending using a sodium montmorillonite clay. The nanocomposites were characterized by X‐ray diffraction and transmission electron microscopy techniques. The best description of these materials is as mixed immiscible‐intercalated nanocomposites. Mechanical testing showed some improvement in the mechanical properties of the nanocomposites relative to those of the virgin polymer. Cone calorimetry showed that the presence of the clay had an advantageous effect on the fire and smoke properties of the polymer.
The effects of plasticizers on the properties of poly(vinyl chloride) foams
Authors: Veličković Sava J. , Stojkov Dejan , Popović Ivanka G. , Brankov Klara , Čvorkov Ljubomir
Published: April 2004

The effects of plasticizers on poly(vinyl chloride) (PVC) plastisol mixtures were investigated. The investigations were carried out by determining the density of the PVC foam obtained by gelling the plastisol, as well as its elasticity and degree of expansion. Two series of experiments using different types of PVC were performed, using eight plasticizers, individually or as mixtures. Two‐component plasticizer mixtures showed better properties than single‐component plasticizers, and mixtures of di‐iso‐heptyl phthalate (DiHP) and butyl benzyl phthalate (BBP) proved to be the most appropriate. The effect of plasticizer amount also was investigated, and of the three parameters studied, the foam density, which steadily increased with plasticizer amount, was the critical one. It was also shown that in order to obtain consistent results, the foam expansion had to be precisely timed and the temperature carefully chosen.
Advances in the stabilization of flexible PVC by using a liquid calcium‐zinc technology
Authors: Reddy James E. , Hackett Jeremy A.
Published: April 2004

The global market for liquid mixed‐metal stabilizers is migrating toward heavy‐metal‐free products, Historically, these systems have not been performance and cost competitive. High efficiency calcium‐zinc stabilizers have the potential to replace heavy‐metal‐based products. The intrinsic value of non‐phenolic lubricating calcium intermediates and calcium‐zinc stabilizers is discussed.
Study of PVC stabilization using capillary rheometry
Authors: Bacaloglu Radu , Fisch Michael H. , Stewen Ulrich , Bacaloglu Ilze , Krainer Edward
Published: April 2004

Capillary rheometry allows monitoring of PVC thermal and shear stress degradations separately. Based on testing of PVC compounds with a capillary rheometer, stabilizers can be efficiently optimized to reduce both degradation processes. Capillary rheometry is an important tool for further improving productivity of PVC processing at high shear rates.
Co‐injection molding of PVC with other thermoplastics: Processing, properties, and applications
Authors: Parsons Mark , Toyoda Paul
Published: April 2004

Rigid poly(vinyl chloride) (PVC) was co‐injected with glass‐fiber‐reinforced PVC (GFR‐PVC), polypropylene (PP), acrylonitrile‐butadiene‐styrene copolymer (ABS), and polycarbonate (PC) by using the Mono‐sandwich co‐injection process. Up to three through‐thickness skin‐core morphologies were observed along the length of the sample. Near the gate, the core was always a single, continuous layer. In some cases, the core diverged into multiple or discontinuous layers. Farther from the gate, flow of the core ceased, leaving a skin‐only region. The skin and core layers were more uniformly distributed through the test plaque when injection speed was low. Adhesion between PVC and PP was poor. Skin and core layers delaminated, and mechanical properties were poor. The PVC adhered well to GFR‐PVC, ABS, and PC. No layer delamination occurred, and mechanical properties were intermediate between those of the skin and core components alone. Dropped dart impact energy was controlled more by the skin layer than the core. In rigid PVC/GFR‐PVC co‐injected samples, impact energy was 2.5 times greater when GFR‐PVC was the core than when GFR‐PVC was the skin.
Molecular weight distribution of commercial emulsion grade PVC
Authors: Pepperl G.
Published: April 2004

At first glance the molecular weight distributions (MWDs) of suspension and emulsion grade PVC are very similar. However, studying the MWDs for both polymerization technologies in more detail reveals systematic differences that can be explained by the differences in the polymerization processes. The MWD of continuous emulsion PVC is broader than that of batch emulsion PVC, which, in turn, is broader than that of suspension PVC. When correlating molecular weight data to K values, it has to be considered that K values from resins including polymerization additives are different from the K value of the pure polymer. The knowledge of the differences in MWD may be helpful for estimating differences in other properties of the products.
Preparation of PVC‐clay nanocomposites by solution blending
Authors: Wang Dongyan , Wilkie Charles A.
Published: April 2004

PVC‐clay nanocomposites have been prepared by solution blending of the polymer with both sodium montmorillonite and an organically modified clay. The nanocomposites have been characterized by X‐ray diffraction and transmission electron microscopy; in all cases the materials are best described as mixed immiscible—intercalated nanocomposites, Thermogravimetric analysis shows that, in some cases, the onset temperature of the degradation is enhanced, and the fraction of nonvolatile residue is always decreased. This decrease in the amount of char indicates a significant change in the degradation pathway of the polymer, caused by the presence of the clay. For some preparations, the tensile strength and modulus are enhanced, in agreement with the formation of a partially intercalated structure.
Kinetics of fatigue and creep crack propagation in PVC pipe
Authors: Hu Y. , Summers J. , Hiltner A. , Baer E.
Published: April 2004

The kinetics of creep and fatigue crack growth in PVC pipe were studied in order to develop a methodology for predicting long‐term creep fracture from short‐term fatigue tests. Fatigue and creep crack propagation followed the conventional Paris law formulations with the same power 2.7: da/dt = AfΔK2.7I and da/dt = BK2.7I, respectively. The activation energy for creep crack propagation, obtained from the temperature dependence of the Paris law prefactor, allowed extrapolation of high temperature creep fracture to low temperature creep crack growth rates. The activation energy for fatigue crack propagation was much lower than that for creep. Therefore, fatigue and creep could not be directly correlated by using the prefactor in the covenentional Paris law formulations. Furthermore, a unique value of the Paris law prefactor did not describe frequency and R‐ratio (amplitude) effects in fatigue crack propagation. Nevertheless, conformity of crack growth rates measured under all conditions to the same Paris law power suggested that correlation should be sought in alternative formulations of the crack growth rate.
PVC/wood‐flour composites compatibilized with chlorinated polyethylene
Authors: Guffey Virginia O. , Sabbagh Amiel B.
Published: April 2004

Chlorinated polyethylene has been demonstrated to be an effective compatibilizer for dissimilar materials in various mixed‐polymer or recycled‐polymer systems. In this paper the use of chlorinated polyethylene to compatibilize polymer/natural‐fiber composites is discussed. Examples of applications in PVC/wood‐flour composites are given.
Manufacture of rigid PVC/wood‐flour composite foams using moisture contained in wood as foaming agent
Authors: Matuana Laurent M. , Mengeloglu Fatih
Published: April 2004

Relatioships between the density of foamed rigid PVC/wood‐flour composites and the moisture content of the wood flour, the chemical foaming agent (CFA) content, the content of all‐acrylic foam modifier, and the extruder die temperature were determined by using a response surface model based on a four‐factor central composite design. The experimental results indicated that there is no synergistic effect between teh CFA content and the moisture content of the wood flour. Wood flour moisture could be used effectively as foaming agent in the production of rigid PVC/wood‐flour composite foams. Foam density as low as 0.4 g/cm3was produced without the use of chemical foaming agents. However, successful foaming of rigid PVC/wood‐flour composite with moisture contained in wood flour strongly depends upon the presence of all‐acrylic foam modifier in the formulation and the extrusion die temperature. The lowest densities were achieved when the all‐acrylic foam modifier concentration was between 7 phr and 10 phr and extruder die temperature was as low as 170°C.
Effect of calcium carbonate on the abrasive wear of melt processing equipment in filled systems
Authors: Mobley Gary , Boutelle Tonia , Garrett Susan , Joiner Laurie , Calhoun Allison
Published: April 2004

Calcium‐carbonate‐loaded systems were tested for abrasive wear on extruder parts through a test that measures the weight of a bronze alloy screen placed in a supporting screen pack before and after 5500 g extrusion run. The effects of particle size and mineral identity were explored in this work as well as the effect of mineral loading level. It was found that the abrasiveness of calcium carbonate is, as expected, much lower than that of titanium dioxide and increases with increased loading levels. It was also shown that the larger the median of the particle size distribution (PSD), the greater the abrasive wear on the screen. Finally, it was shown that the degree of wear could be correlated with the level of impurities present in the natural mineral.
American History/American Memory: Reevaluating Walt Whitman's Relationship with the Brooklyn Bridge
Authors: HAW RICHARD
Published: April 2004

No one did more to sanctify and enshrine the image of Abraham Lincoln than Walt Whitman. The poet never met the president, but he embraced his image and claimed him as his own. In his “Death of Abraham Lincoln” speech, delivered on numerous occasions during the last 20 years of his life, Whitman involved himself in the cultural work of national definition, of posterity and legacy. He helped bridge the gap between complex personal history and official public memory. In service to the larger, national idea of union, democracy and selfless Americanism, Whitman's Lincoln, when compared to, for example Herndon's Life of Lincoln (1889), razed the contours of ambiguity and established the exemplary image of the “Martyr Chief.” The connection is both apt and ironic. What Whitman did for Lincoln in the aftermath of his death, others would do for the poet. Since Whitman's death in 1892, the poet's life and ideas have often been radically simplified; on other occasions his words have been recontextualized and appropriated to support a variety of different causes, concerns and ideologies. A driving factor in this process has been that, like Lincoln, Whitman's name carries with it a certain legitimacy. To evoke the approval of Whitman is to learn of the authority of an ideal, more perfect, America. And where Lincoln's name is inseparable from the American Civil War, Whitman has become most strongly associated with the metropolitan idea of New York, and Brooklyn in particular.
The Organisation Strikes Back: Rhetorical Empowerment Strategies in 1950s Business Representations of White-Collar Manhood
Authors: ARTHUR ERICA
Published: April 2004

The critical appraisal of the 1950s organised society is well established in such now-classic texts such as David Riesman's The Lonely Crowd (1950), C. Wright Mills's White Collar (1951) and William H. Whyte's The Organization Man (1956). These works exposed the group-orientated, “other-directed” corporate personality, motivated by an extreme desire to belong, as a precarious foundation for individual security. If not considered from an explicitly masculine perspective, the emasculating connotations of this model of occupational identity were nevertheless evident in Mills's conception of the white-collar “little man,” Riesman's definition of the “limp” and “exceptionally sensitive” other-directed personality and Whyte's characterisation of the organisation man as the unobtrusive “man in the middle.” Collectively, the depiction of white-collar masculinity in these texts helped create the context for the stereotypical perception of 1950s business enterprise as a breeding ground for conformity and troubled male identity. Less appreciated, however, is the business community's response to this critical appraisal.
From “Informed Choice” to “Social Hygiene”: Government Control of Cigarette Smoking in the US
Authors: BAILEY CHRISTOPHER J.
Published: April 2004

In 1964 US Surgeon General Luther L. Terry published a report on smoking and health which concluded that “Cigarette smoking is a health hazard of sufficient importance in the United States to warrant appropriate remedial action.” Publication of this report marked the beginning of contemporary governmental efforts to control smoking. Over the next 40 years a range of legislative and regulatory action at all levels of government sought to restrict an activity that had become widely identified as the leading cause of preventable death in the United States. Warning labels were required on cigarette packages, restrictions placed on advertising, controls introduced on the sale of cigarettes, lists of additives in cigarettes submitted to the federal government, excise taxes increased, and restrictions introduced on smoking in public places. Efforts to assert some control over the content of cigarettes, however, were unsuccessful. Exemptions for tobacco products can be found in virtually all federal consumer safety laws.
Lawrence Welk and John Wooden: Midwestern Small-Town Boys Who Never Left Home
Authors: MILLER JOHN E.
Published: April 2004

Considered by many to be the most American part of America, the Midwest occupies a unique place in the national psyche, and its residents have been called the archetypal or quintessential Americans. The region is – and was – anything but homogenous, and any adequate treatment of it needs to take into account its many variations, complexities, and paradoxes. Any search for the essential character of the region soon founders on recognition of its cultural diversity. Yet, acknowledgment of the hazards of advancing broad generalizations about a region extending from Ohio to the Dakotas and ranging as far south as Missouri should not bar us from inquiring into the qualities and characteristics of its people. Despite the contradictions and complexities attaching to the region, the Midwest possesses a distinctive cultural identity, joining its constituent elements in an unstable and constantly changing, but nevertheless recognizable, pattern.
A correct, precise and efficient integration of set-sharing, freeness and linearity for the analysis of finite and rational tree languages
Authors: HILL PATRICIA M. , ZAFFANELLA ENEA , BAGNARA ROBERTO
Published: April 2004

It is well known that freeness and linearity information positively interact with aliasing information, allowing both the precision and the efficiency of the sharing analysis of logic programs to be improved. In this paper, we present a novel combination of set-sharing with freeness and linearity information, which is characterized by an improved abstract unification operator. We provide a new abstraction function and prove the correctness of the analysis for both the finite tree and the rational tree cases. Moreover, we show that the same notion of redundant information as identified in Bagnara et al. (2000) and Zaffanella et al. (2002) also applies to this abstract domain combination: this allows for the implementation of an abstract unification operator running in polynomial time and achieving the same precision on all the considered observable properties.
Applications of intuitionistic logic in Answer Set Programming
Authors: OSORIO MAURICIO , NAVARRO JUAN A. , ARRAZOLA JOSÉ
Published: April 2004

We present some applications of intermediate logics in the field of Answer Set Programming (ASP). A brief, but comprehensive introduction to the answer set semantics, intuitionistic and other intermediate logics is given. Some equivalence notions and their applications are discussed. Some results on intermediate logics are shown, and applied later to prove properties of answer sets. A characterization of answer sets for logic programs with nested expressions is provided in terms of intuitionistic provability, generalizing a recent result given by Pearce. It is known that the answer set semantics for logic programs with nested expressions may select non-minimal models. Minimal models can be very important in some applications, therefore we studied them; in particular we obtain a characterization, in terms of intuitionistic logic, of answer sets which are also minimal models. We show that the logic G3 characterizes the notion of strong equivalence between programs under the semantic induced by these models. Finally we discuss possible applications and consequences of our results. They clearly state interesting links between ASP and intermediate logics, which might bring research in these two areas together.
Characteristics of deep (≥13 km) Hawaiian earthquakes and Hawaiian earthquakes west of 155.55°W
Authors: Wolfe Cecily J. , Okubo Paul G. , Ekström Göran , Nettles Meredith , Shearer Peter M.
Published: April 2004

High precision relocation of earthquakes recorded by the Hawaiian Volcano Observatory (HVO) seismic network provides new information on the characteristics of seismic faulting at this oceanic hot spot. Using waveform cross correlation, we have measured correlation coefficients and travel time differences for a set of 14,605 deep (≥13 km) earthquakes recorded from 1988 to 1998. We find that about half of the analyzed earthquakes are in similar event clusters that delineate fault zones in the lower crust and upper mantle. We suggest that much of this deep seismicity reflects rupture in the brittle lithosphere away from the magma pathways, although at Kilauea the stresses from magma movement may additionally help trigger mantle earthquakes on preexisting faults in regions with high differential ambient stresses. Focal mechanisms of similar event clusters throughout Hawaii display characteristic patterns and appear consistent with the hypothesis that deep earthquakes on preexisting faults reflect the stresses due to volcano loading and flexure. We also present the results of applying cross correlation analyses and relocation to ∼7000 earthquakes at all depths located west of 155.55°W and recorded from 1988 to 1998. The pattern of relocated earthquakes at the Kealakekua fault zone is consistent with the presence of a low‐angle detachment on the west flank of Mauna Loa.