bluuebunny/crossref_metadata_2025_split huggingface dataset:
A second generation high performance screw for low extrusion temperature rigid PVC profile compounds
Authors: Kim H. T. 
Published: December 2004

AbstractThe melting and extrusion behavior of low shear rigid PVC profile compounds such as Geon 8700A were investigated in order to answer the fundamental question as to why the output rate of this type of compound is relatively low compared to other types of PVC compound. Typically, the extrusion rate of Geon 8700A is less than half those achieveable on other PVC compounds. A part of the reason is that the extrusion melt temperature of Geon 8700A has to be kept below 360°F in order to preserve primary PVC particles in extrudates and to maintain smooth extrudate surfaces.The study showed that Geon 8700A follows an entirely different melting mechanism in extrusion—quite opposite to the one previously accepted. Geon 8700A undergoes the melting mechanism observed by Menges, et al. due mainly to its nonwetting characteristic on the barrel surface while most other PVC compounds follow the mechanism described by Tadmor. The difference between the two mechanisms lies in the location of the melt pool formation—the Tadmor model in the pushing side of the screw flight and the Menges in the opposite leading side of the screw flight. Extruding Geon 8700A on screws—notably 2‐channel screws—optimized for the different Tadmor model is one of the major reasons for such a poor performance with this compound.A new dual pitch deep channel screw has been developed. It is optimized for the melting mechanism of Geon 8700A, resulting in a dramatic improvement in both output rates and extrudate quality. Rates of 350 pounds/hour at 350°F and 400 pounds/hour at 363°F have been achieved on the 3–1/2 inch extruder, whereas 150 to 200 pounds/hour at 350°F is common with the standard screws. This new screw technology, with its high output rate and superior extrudate quality capability, makes the extrusion of cube compounds on single screw extruders competitive with powder extrusion on multi‐screw extruders.
Rheology of PVC; part IV: Particulate flow
Authors: Utracki L. A. 
Published: December 2004

AbstractThe behavior of polyvinyl chloride, (PVC), formulation changes drastically with the temperature and the method of sample preparation. In the steady state shear mode, upon a decrease of the rate of deformation, the data may show either a steady increase of the shear viscosity or leveling off to a Newtonian plateau. In the dynamic test mode, the storage modulus, G′, shows a viscoelastic behavior, whereas the loss modulus, G″, shows the yield. Only at temperatures above 210°C are normal flow curves for polymer melts obtained. Rigid PVC wire coating formulation was examined at 140 to 220°C using serrated parallel plates, 2.5 cm in diameter. The data at frequencies ω = 10−2 to 102 rads/s were recorded. The results were analyzed in terms of the relation, derived for polymeric composites, in which the yield stress was explicitly incorporated. It was found that G″ (but not G*) could be easily understood in terms of the model, provided that the yield stress was allowed to vary with the temperature. Three distinct flow zones were observed with the two border‐temperatures at about 180 and 210°C, assigned respectively as due to gel and crystalline melting. These findings were supported by earlier results of the dielectric measurements. In conclusion, treating PVC as a composite provides a simple and effective means of data interpretation.
Effects of postchlorination on key product and processing properties of PVC
Authors: Neuman Richard C. 
Published: December 2004

AbstractThe behavior of PVC resins has been shown to change dramatically when postchlorinated from 57 to 70 percent chlorine. Many of these changes are beneficial: heat resistance, thermoformability, and combustion properties are improved to an extent that opens new market opportunities for properly formulated chlorinated PVC (CPVC) materials. Sharply increasing melt viscosity also results from increasing chlorine content, creating the need for compounding and processing expertise differing from that for rigid PVC. The fact that such expertise has been developed, and is constantly being improved, is expanding the use of CPVC.
Monitoring process conditions of plastisols using a dielectrometer
Authors: Lin Shiow‐Ching 
Published: December 2004

AbstractTraditionally, an instrument such as an Instron rheometer or thermal analysis is used to characterize the processing conditions of a plastisol. The Instron rheometer is useful only when the material begins to build up mechanical strength. A rheometer such as a Plasti‐corder suffers from the requirement of large sample and low sensitivity toward rheology change caused by phase variation. Thermal analysis only responds to the heat capacity and enthalpy changes at transitions occurring during plasticization. The plasticization involves only weak thermal change and is difficult to detect by thermal analysis. However, the more sensitive method of dielectrometric analysis, which needs only a small sample, was used to detect any rheological change of a plastisol during plasticization. Because the information obtained is from molecular motion, the results are accurate and the speed of characterization is rapid.
Rheology of dispersions of poly(vinyl chloride) with liquid rubbers
Authors: Drag Jiří , Šimoník Josef 
Published: December 2004

AbstractThe effect of polybutadiene and butadiene‐acrylonitrile rubbers on the rheological properties of PVC plastisols was studied. The results obtained show that the flow properties of these blends can be described by the Ostwald‐de Weale equation. Parameters of this equation depend on the amount of rubber in the blend and its solubility parameter which can be derived from the rubber structure.
Functional acrylic monomers as modifiers for PVC plastisol formulations
Authors: Weaver David L. 
Published: December 2004

AbstractFunctional acrylic monomers are used as coagents with polyvinyl chloride plastisols to improve abrasion resistance, tensile strength, chemical resistance, permanent set, hardness, and adhesion. The emphasis of this paper is on the enhancement of physical properties which can be achieved through addition of a variety of different functional acrylic monomers (mono‐, di‐, and tri‐functional) to a PVC plastisol formulation. Collected test data will be given to show the effect these monomers have on the plastisol's physical properties.
Dynamic mechanical analysis of poly(vinyl chloride) compounds and blends
Authors: Rohn Charles L. 
Published: December 2004

AbstractPVC is one of the most versatile and cost effective commercial polymers. A main limitation of PVC is optimizing its fabrication characteristics and end use properties with minimum adverse effect on either. PVC compounding technology is supersensitive due to effect of subtle variations in formulations causing “inspec” products during one production run and “out‐of‐spec” products in another. Large variations in properties are frequently due to improper mixing. Dynamic mechanical analyses provides a method of monitoring variations in mixing and their affect on morphological structure deviations which can lead to poor processing and end use properties.
Effect of morphology and refractive index on toughness and clarity balance of MBS modified vinyl bottles
Authors: Dunkelberger D. L. , Dougherty E. P. 
Published: December 2004

AbstractImpact modifiers are used to enhance the toughness of rigid vinyl by providing a dispersed rubbery phase to absorb impact energy and prevent fracture of the otherwise brittle matrix. MBS impact modifiers are complex core//shell polymer structures based on specially prepared butadiene/styrene rubber latices with multiple stages of acrylic and other polymers grafted to them. In addition to providing a rubbery dispersed phase to improve to improve the toughness of vinyl, these structures also maintain clarity by matching the refractive index of the rubber particles with that of the vinyl matrix. Data will be present showing the effect of the rubber morphology, particle size and refractive index on the balance of impact strength and clarity of MBS modified vinyl packaging formulations.
PVC/plasticizer compatibility: Evaluation and its relation to processing
Authors: Ramos‐Devalle Luis , Gilbert Marianne 
Published: December 2004

AbstractThe compatibility of suspension poly(vinylchloride) [PVC] with twelve different plasticizers was determined using calculated compatibility predictors, as well as actual measurements of compatibility. Solubility parameters were capable of classifying plasticizers of a given family in terms of their compatibility with PVC, but were not useful for comparing plasticizers from different families. A polarity parameter, the product of the molar mass of the plasticizer and its polarity ratio, was found to be a useful predictor of activity for monomeric plasticizers.
Use of organotin stabilizers—risk assessment analysis
Authors: Mesch Keith A. , Kugele Thomas G. 
Published: December 2004

AbstractOrganotin compounds have long been known in the PVC industry for their excellent performance properties in almost every application. Over the past several years, a wide variety of health and environmental studies have been conducted which demonstrate the safe use of these performance chemicals as PVC heat stabilizers. This paper introduces the “risk equation” and then applies this equation to the foreseeable exposure risks involved with the use of organotin stabilizers during PVC processing. Further, migration of organotin species from PVC end‐use articles is discussed with comparison to established long‐term no‐effect levels for these chemicals. The environmental fate of organotin compounds and their effects on some species of microorganisms is also addressed. The risk equation is used to fully evaluate all potential hazards to provide a fully informed risk assessment for the use of organotin stabilizers in PVC.
Melt filtration: The final step in the purification of PVC bottles for recycling
Authors: Sadowski Gary M. , Shaw Lane G. 
Published: December 2004

AbstractThe final step in the purification of PVC bottles for recycling is melt filtration. However, this common practice increases in complexity when dealing with a clear, thermally sensitive material such as PVC. This paper will explore both conventional and new techniques for melt filtration. This paper also describes various types of contamination found in the form of other polymers and foreign material, as well as experimental data on acceptable levels and processing conditions to purge them from the vinyl melt stream.
Factors affecting the abrasiveness of filled rigid PVC dry blends
Authors: Augustyn E. J. , Leonard J. 
Published: December 2004

AbstractAbrasion due to the high speed mixing of rigid PVC dry blends filled with CaCO3 was found to be a function of both the mixing conditions and type and level of CaCO3 used. Laboratory scale tests showed that abrasion is a function of mix time, mix speed, and mixer blade geometry. These variables were standardized to develop a laboratory abrasion test using a Hockmeyer mixer equipped with a soft 3‐in diameter aluminum mixing blade. This procedure was used to investigate the effect of CaCO3 property variables on abrasion during rigid PVC dry blending. Multiple linear regression analysis at 30 phr CaCO3 showed that abrasion increased with filler top cut, mean, acid insolubles, and MgCO3 content, but diminished with an increase in percent less than 1 micron fraction. A more generalized abrasion predictor model was developed by considering surface area to be a linear function of top cut, mean, and percent less than 1 micron properties. Abrasion was greatly minimized by using finer particle size, higher surface area CaCO3 with low acid insoluble and magnesium carbonate levels. These criteria also aid in reducing the abrasive effects of TiO2 during dry blending through a CaCO3/TiO2 interaction.
Use of misoprostol on an outpatient basis for postdate pregnancy
Authors: Kipikasa J.H. , Adair C.D. , Williamson J. , Breen J.M. , Medford L.K. , Sanchez‐Ramos L. 
Published: December 2004

AbstractObjectiveWithin the obstetric community, several studies suggest that cervical ripening and labor induction after 40 weeks' gestation leads to improved maternal and neonatal outcomes. The most effective drug regimen to safely promote labor has not been determined.MethodForty‐nine subjects followed in an outpatient obstetrical clinic with pregnancies of at least 40 weeks' gestation, and an unfavorable Bishop score were assigned randomly to receive oral misoprostol 50 or 25 μg every 3 days for a maximum of three doses.ResultsTwenty‐three subjects received misoprostol 25 μg and 26 received 50 μg. The mean interval (±standard deviation) from start of cervical ripening to delivery was 2.4 days ±0.3 vs. 3.9 days ±0.7 for the 50 and 25 μg groups (P<0.05). No adverse events were noted. However, due to small sample size, less frequent adverse events may be missed. Type II errors cannot be excluded.ConclusionIn the prevention of postdate pregnancy, outpatients use of oral misoprostol 50 μg appears to result in earlier delivery, as compared to 25 μg.
The Protective Effect of Alpha-Lipoic Acid against Oxidative Damage in Rabbit Conjunctiva and Cornea Exposed to Ultraviolet Radiation
Authors: Demir Ülkü , Demir Tamer , Ilhan Nevin 
Published: December 2004

<i>Purpose:</i> The purpose of this study was to determine the protective effect of α-lipoic acid against oxidative damage in rabbit conjunctiva and cornea exposed to ultraviolet radiation. <i>Methods:</i> 20 rabbits weighing 2,500– 3,000 g were used, and we divided them into 4 groups with 5 randomly selected rabbits. The rabbits were exposed to 2 J/cm<sup>2</sup>/h of ultraviolet A radiation (UVA) in the range of 320–405 nm for 12 h per day within 90 days. The control group did not undergo any procedure, the UVA group was only exposed to UVA radiation. The PUVA group was treated with 8-methoxypsoralen and UVA. The α-lipoic acid group was administered 8-methoxypsoralen + UVA + α-lipoic acid. At the end of 90 days, the rabbits were killed by decapitation, and the eyes were enucleated. Both eyes of each rabbit were used for biochemical evaluation. Conjunctival and corneal free malondialdehyde (MDA), glutathione peroxidase (GSH-PX) and superoxide dismutase (SOD) levels were compared among the groups. <i>Results:</i> Conjunctival free MDA levels were lower in the α-lipoic acid group compared with the UVA and PUVA groups (p < 0.05, p < 0.001, respectively). Both conjunctival SOD levels (p < 0.05, p < 0.01, respectively) and conjunctival GSH-PX levels (p < 0.01, p < 0.001, respectively) were higher in the α-lipoic acid group compared with other groups. Corneal free MDA levels were lower in the α-lipoic acid group compared with the UVA and PUVA groups (p < 0.01, p < 0.001, respectively). Both corneal SOD levels (p < 0.01, p < 0.01, respectively) and corneal GSH-PX levels (p < 0.01, p < 0.01, respectively) were higher in the α-lipoic acid group compared with the other groups. <i>Conclusion:</i> α-Lipoic acid which is considered as potent antioxidant protects the eye from the damaging effect of ultraviolet exposure.
Sensitivity Analysis of Cirrus Cloud Properties from High-Resolution Infrared Spectra. Part I: Methodology and Synthetic Cirrus
Authors: Kahn Brian H. , Eldering Annmarie , Ghil Michael , Bordoni Simona , Clough Shepard A. 
Published: December 2004

AbstractA set of simulated high-resolution infrared (IR) emission spectra of synthetic cirrus clouds is used to perform a sensitivity analysis of top-of-atmosphere (TOA) radiance to cloud parameters. Principal component analysis (PCA) is applied to assess the variability of radiance across the spectrum with respect to microphysical and bulk cloud quantities. These quantities include particle shape, effective radius (reff), ice water path (IWP), cloud height Zcld and thickness ΔZcld, and vertical profiles of temperature T(z) and water vapor mixing ratio w(z). It is shown that IWP variations in simulated cloud cover dominate TOA radiance variability. Cloud height and thickness, as well as T(z) variations, also contribute to considerable TOA radiance variability.The empirical orthogonal functions (EOFs) of radiance variability show both similarities and differences in spectral shape and magnitude of variability when one physical quantity or another is being modified. In certain cases, it is possible to identify the EOF that represents variability with respect to one or more physical quantities. In other instances, similar EOFs result from different sets of physical quantities, emphasizing the need for multiple, independent data sources to retrieve cloud parameters. When analyzing a set of simulated spectra that include joint variations of IWP, reff, and w(z) across a realistic range of values, the first two EOFs capture approximately 92%–97% and 2%–6% of the total variance, respectively; they reflect the combined effect of IWP and reff. The third EOF accounts for only 1%–2% of the variance and resembles the EOF from analysis of spectra where only w(z) changes. Sensitivity with respect to particle size increases significantly for reff several tens of microns or less. For small-particle reff, the sensitivity with respect to the joint variation of IWP, reff, and w(z) is well approximated by the sum of the sensitivities with respect to variations in each of three quantities separately.
Mechanisms Controlling the Annual Cycle of Precipitation in the Tropical Atlantic Sector in an Atmospheric GCM*
Authors: Biasutti M. , Battisti D. S. , Sarachik E. S. 
Published: December 2004

Abstract
A set of AGCM experiments is used to study the annual cycle of precipitation in the region surrounding the tropical Atlantic Ocean. The experiments are designed to reveal the relative importance of insolation over land and the (uncoupled) SST on the annual cycle of precipitation over the tropical Atlantic Ocean, Africa, and the tropical Americas.
SST variations impact the position of the maritime ITCZ by forcing the hydrostatic adjustment of the atmospheric boundary layer and changes in surface pressure and low-level convergence. The condensation heating released in the ITCZ contributes substantially to the surface circulation and the maintenance of the SST-induced ITCZ anomalies.
The remote influence of SST is felt in equatorial coastal areas and the Sahel. The circulation driven by condensation heating in the maritime ITCZ extends to the coastal regions, thus communicating the SST signal onshore. Conversely, the Sahel responds to variations in SST through boundary layer processes that do not involve the maritime ITCZ. The atmospheric response to changes in subtropical SST is advected inland and forces changes in sea level pressure and low-level convergence across a large part of tropical Africa.
The impact of local insolation on continental precipitation can be explained by balancing net energy input at the top of the atmospheric column with the export of energy by the divergent circulation that accompanies convection. Increased insolation reduces the stability of the atmosphere in the main continental convection centers, but not in monsoon regions.
Insolation over land impacts the intensity of the maritime ITCZ via its influence on precipitation in Africa and South America. Reduced land precipitation induces the cooling of the Atlantic upper troposphere and the enhancement of convective available potential energy in the maritime ITCZ.
Comparison of NOAA's Operational AVHRR-Derived Cloud Amount to Other Satellite-Derived Cloud Climatologies
Authors: Thomas Sarah M. , Heidinger Andrew K. , Pavolonis Michael J. 
Published: December 2004

Abstract
A comparison is made between a new operational NOAA Advanced Very High Resolution Radiometer (AVHRR) global cloud amount product to those from established satellite-derived cloud climatologies. The new operational NOAA AVHRR cloud amount is derived using the cloud detection scheme in the extended Clouds from AVHRR (CLAVR-x) system. The cloud mask within CLAVR-x is a replacement for the Clouds from AVHRR phase 1 (CLAVR-1) cloud mask. Previous analysis of the CLAVR-1 cloud climatologies reveals that its utility for climate studies is reduced by poor high-latitude performance and the inability to include data from the morning orbiting satellites. This study demonstrates, through comparison with established satellite-derived cloud climatologies, the ability of CLAVR-x to overcome the two main shortcomings of the CLAVR-1-derived cloud climatologies. While systematic differences remain in the cloud amounts from CLAVR-x and other climatologies, no evidence is seen that these differences represent a failure of the CLAVR-x cloud detection scheme. Comparisons for July 1995 and January 1996 indicate that for most latitude zones, CLAVR-x produces less cloud than the International Satellite Cloud Climatology Project (ISCCP) and the University of Wisconsin High Resolution Infrared Radiation Sounder (UW HIRS). Comparisons to the Moderate Resolution Imaging Spectroradiometer (MODIS) for 1–8 April 2003 also reveal that CLAVR-x tends to produce less cloud. Comparison of the seasonal cycle (July–January) of cloud difference with ISCCP, however, indicates close agreement. It is argued that these differences may be due to the methodology used to construct a cloud amount from the individual pixel-level cloud detection results. Overall, the global cloud amounts from CLAVR-x appear to be an improvement over those from CLAVR-1 and compare well to those from established satellite cloud climatologies. The CLAVR-x cloud detection results have been operational since late 2003 and are available in real time from NOAA.
Status of Surgical Margins and Prognosis in Adult Soft Tissue Sarcomas of the Extremities: A Series of Patients Treated at a Single Institution
Authors: Gronchi A. , Casali P.G. , Mariani L. , Miceli R. , Fiore M. , Lo Vullo S. , Bertulli R. , Collini P. , Lozza L. , Olmi P. , Rosai J. 
Published: December 2004

Purpose To explore the prognostic effect of microscopic marginal status after surgery for extremity soft tissue sarcomas. Patients and Methods We analyzed 911 consecutive patients surgically treated throughout a 20-year span at a single referral center. Six hundred forty-two were first seen with a primary tumor, and 269, with a locally recurrent tumor. All patients underwent macroscopically complete resection. Microscopic marginal status was negative (tumor size > 1 mm) in 748 patients and positive (≤ 1 mm) in 163 patients. Median follow-up was 107 months. Results Patients with primary disease had a lower disease-specific mortality in comparison to those first examined for recurrence (25% v 37%, respectively, at 10 years). Size, malignancy grade, depth, histotype, and local recurrence had a statistically significant prognostic effect at multivariable analysis, while microscopically positive surgical margins had not, though a trend in favor of negative margins was observed. However, an extra risk was observed for patients with positive margins after 3 to 5 years (hazard ratio, 1.8 after 5 years v 0.8 before 5 years). In patients treated for a local recurrence, the prognostic impact of positive margins was higher (hazard ratio, 1.6). Conclusion Positive surgical margins had a weak adverse prognostic effect, which was more pronounced for those patients escaping an early relapse. This would seem to justify a policy of surgical adequacy in adult soft tissue sarcomas, though clinical decision making in borderline presentations for conservative surgery might be reasonably flexible and shared with the patient. Once a local relapse has occurred, the impact of local treatments seems more critical.