bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ecological aspects of polymer flame retardation
Authors: Zaikov G. E. , Lomakin S. M. 
Published: April 2004

AbstractThe practical application of commercial polymer flame retardants can no longer meet present requirements in terms of effectiveness or hazard. The most effective flame retardants used thus far have been halogen‐, phosphorus‐, antimony‐, and heavy‐metal‐based compounds, which, however, have the most environmental impact, either when they perform their action or when they are burned in the incineration of waste containing fire‐retardant polymeric materials. The practical search for new ecologically friendly flame retardants requires cooperation between industry and academia. This paper is devoted to only a few of the new approaches to this very important task: polymer char formers, low‐melting‐glass systems, and morphological modifications.
Low extractable lead stabilizers
Authors: Grossman Richard F. 
Published: April 2004

AbstractAlthough lead stabilizers are less soluble and form less soluble reaction products than other types, because of the nature of the U.S. EPA Toxic Characteristic Leaching Procedure extraction, it is often difficult to certify lead‐stabilized scrap as nonhazardous waste. It has been found that lead stabilizers can be blended with additives that lead to reaction products that appear to be extremely insoluble complex phosphates. The results are lead‐stabilized compositions with significantly reduced lead extractability.
Mechanism of organotin stabilization of poly(vinyl chloride). 2: Significance for PVC stabilization of structure and equilibria of alkyltin thioglycolates/chlorides
Authors: Fisch Michael H. , Bacaloglu Radu , Biesiada Keith , Brecker Lawrence R. 
Published: April 2004

AbstractThe stabilization effect of alkyltin thioglycolates was determined by the measurement of discoloration of PVC formulations. The results were interpreted considering the structure of these compounds, their equilibration with alkyltin chlorides, and their postulated association with chlorine atoms at PVC primary particle surfaces.
Plasticizer factors influencing take‐up by PVC resins
Authors: Krauskopf Leonard G. , Godwin Allen D. 
Published: April 2004

AbstractThe ease with which plasticizer is combined with poly(vinyl chloride) resin is a measure of processing characteristics critical in the dry blending of suspension PVC and the gelation of plastisols.By using commercial grade plasticizers, this study developed predictive equations for the following processing parameters of dialkyl phthalates in PVC:

Relative dry‐blend rates in suspension PVC as a function of plasticizer viscosity.
Relative initial gelation temperatures in plastisols as a function of plasticizer molecular weight and solvating strength.
Relative final gelation temperatures in plastisols as a function of plasticizer solvating strength.
This information allows one to predict the relative processing characteristics of any dialkyl phthalate plasticizer for PVC on the basis of its chemical and physical properties.
Contribution of flow deformation to the shrinkage of injection molded PVC
Authors: Ray E. Harrell , Elleithy Rabeh H. , McFarland Coleen A. , Summers James W. 
Published: April 2004

AbstractThe viscoelastic nature of PVC cannot be ignored during the injection molding process. Strains imposed on the compound during the injection stage display recovery dynamics that are indicative of the temperature at which the strains were imposed. A mathematical model, employing “approximate” time‐temperature modulus relationships, provided the basis for interpreting the shrinkage data. A distribution map of the various relative temperatures attained within the part during injection was determined.
Stabilizers for peroxydicarbonate initiator solutions
Authors: Frenkel Peter , Pettijohn Ted 
Published: April 2004

AbstractLiquid dialkyl peroxydicarbonates are used as initiators in the PVC industry. Because of the thermal reactivity of these initiators, they require very low temperature storage, shipment, and handling. At temperatures above 10°C, most undergo autoaccelerated self‐induced decomposition. In other words, their self‐accelerating decomposition temperature (SADT) is exceeded. New additives have been discovered which increase the SADT of the initiators. These additives effectively stabilize the products, making them safer to handle, store, and ship. The proprietary additives and a mechanism of stabilization are discussed. We also include a section concerning the implications these products have for future initiator formulation.
Study of some parameters responsible for the efficiency of hindered amine light stabilizers
Authors: Geuskens G. , McFarlane D. M. 
Published: April 2004

AbstractThe photooxidation of a styrene‐butadiene‐styrene block copolymer previously hydroperoxidized by reaction with singlet oxygen has been studied by measuring the increase of the carbonyl absorbance at 1720 cm−1. Five different hindered amine light stabilizers (HALS) have been introduced into the polymer by diffusion from methanolic solutions, and their efficiencies as inhibitors of the photooxidation have been compared. The sequence of efficiency observed is:tert. amine > sec. amine > amino etherUnder the experimental conditions used HALS are localized preferentially in oxidized regions of the polymer, and their efficiency can be correlated with their ability to catalyze the decomposition of clustered hydroperoxides. As a consequence, HALS are oxidized to nitroxy radicals that are the actual inhibitors of the photooxidation. A high local concentration of HALS in oxidized regions of the polymer also contributes to their efficiency, and this effect justifies the observation that some tertiary amines are more efficient than others.
Blends of poly(vinyl chloride) with plasticized polyaniline
Authors: Pielichowski Krzysztof , Pearce Eli M. 
Published: April 2004

AbstractA series of poly(vinyl chloride) (PVC)/polyaniline (PANI) blends plasticized and protonated simulataneously by bis(2‐ethylhexyl) hydrogen phosphate, bis(4‐nitrophenyl) phosphate, diphenyl phosphate, or dibenzyl phosphate was prepared by a mass homogenization technique. Thermal analysis studies by means of thermo‐gravimetric analysis (TGA) and differential scanning calorimetry (DSC) revealed that PVC/PANI blends with bis(2‐ethylhexyl) hydrogen phosphate were characterized by the highest thermal stability values. Kinetic analysis of the decomposition process by the isoconversional Friedman method showed that the activation energy did not change substantially over the broad conversion range; further advanced kinetic analysis by a nonlinear regression method revealed that the kinetic function that was the best approximation for the experimental data was based on a reaction of nth order.
Fate of PVC polymer, plasticizers, and stabilizers in landfilled waste
Authors: Mersiowsky Ivo 
Published: April 2004

AbstractEnd‐of‐life PVC products are predominantly disposed of with construction waste or with municipal solid waste in sanitary landfills. This waste management option is currently subject to debate because of environmental issues. A material and substance flow analysis was conducted to estimate the quantitative relevance of PVC products and their constituents in municipal solid waste. Landfill simulation assays demonstrated the long‐term behavior of PVC products and the fate of additives under landfill conditions. The PVC polymer was found to be stable. A loss of plasticizers may occur in case of insufficient compatibility with the PVC compound coupled with microbial consumption at the PVC product surface. Losses of stabilizers are generally restricted to transient leaching from the product surface. Plasticized products show a somewhat stronger inclination to release their stabilizers. The findings indicated that additional measures specifically directed at post‐consumer PVC waste in landfills are not necessary.
Weatherability of plastics compared at different exposure locations
Authors: Summers James W. , Rabinovitch Elvira B. 
Published: April 2004

AbstractThe mechanisms of the weathering of plastics are often initiated by damaging radiation from the sun or by the hydrolysis of ester, carbonate, or amide groups in the polymer. The Arizona exposure is sunny and dry, while the Ohio exposure is less sunny, wetter, and has more acid rain. Arizona emphasizes ultraviolet light exposure; Ohio emphasizes hydrolysis. This paper examines the weatherability of vinyl, ABS, acrylic, and SAN/EPDM polymers in these two locations. Color retention, original impact, and impact retention are evaluated.
Additive interactions in the stabilization of film grade high‐density polyethylene. Part I: Stabilization and influence of zinc stearate during melt processing
Authors: Parrondo Aitor , Allen Norman S. , Edge Michele , Liauw Christopher M. , Fontán Eusebio , Corrales Teresa 
Published: April 2004

AbstractThe melt stabilization activity of some of the most commercially significant phenolic antioxidants and phosphites (alone and in combination), without and with zinc stearate, was studied in high‐density polyethylene (HDPE) produced by Phillips catalyst technology. Multiple pass extrusion experiments were used to degrade the polymer melt progressively. The effect of stabilizers was assessed via melt flow rate (MFR) and yellowness index (YI) measurements conducted as a function of the number of passes. The level of the phenolic antioxidant remaining after each extrusion was determined by high‐performance liquid chromatography (HPLC). Phenolic antioxidants and phosphites both improved the melt stability of the polymer in terms of elt viscosity retention; the influence of zinc stearate was found to be almost insignificant. However, phosphites and zinc stearate decreased the discoloration caused by the phenolic antioxidants. A correlation was found between the melt stabilization performance of phosphites and their hydroperoxide decomposition efficiency determind via a model hydroperoxide compound. Steric and electronic effects associated with the phosphorus atom influenced the reactivity towards hydroperoxides. Furthermore, high hydrolytic stability did not automatically result in lower efficiency. Besides phosphite molecular structure, stabilization activity was also influenced by the structure of the primary phenolic antioxidant and the presence of zinc stearate.
Additive interactions in the stabilization of film grade high‐density polyethylene. Part II: Stabilization during long‐term service
Authors: Parrondo Aitor , Allen Norman S. , Edge Michele , Liauw Christopher M. , Fontán Eusebio 
Published: April 2004

AbstractIn the second part of this study, the performance of phenol/phosphite/zinc stearate packages and the contribution of each additive to the long‐term thermal stabilization and photostabilization were evaluated in high‐density polyethylene produced by using Phillips catalyst technology. Infrared spectroscopy, ultraviolet spectroscopy, and yellowness index measurements were used to establish the performance of the different additive packages. The HPLC analysis of dichloromethane extracts of the polymer was carried out after melt processing in order to determine the amount of phenolic antioxidant remaining in the samples. The long‐term thermal stabilization was dependent only upon the phenolic antioxidant concentration, whereas both phenolic antioxidants and phosphites contributed directly to photostabilization. Zinc stearate did not show any significant influence on the stabilization under either thermooxidative or photooxidative conditions.
Some aspects of the thermal degradation of PVC. Crosslinking of macromolecules
Authors: Yanborisov V. M. , Minsker K. S. , Zaikov G. E. , Zaikov V. G. 
Published: April 2004

AbstractDirect experimental proof is presented that crosslinking of macromolecules during the thermal degradation of PVC proceeds with participation of blocks of conjugated double bonds formed upon activation by carbonylallyl groups.
A web‐based tool for dissertation writing Rosanne Strachan, Rowena Murray and Hilary Grierson
Authors: Strachan Rosanne , Murray Rowena , Grierson Hilary 
Published: April 2004

AbstractOnline web tools are becoming an important and accessible means of supporting learning in higher education. Student writing is central to teaching and learning (Lillis, 2001). This paper describes an online tool designed to support dissertation writing. By combining three types of online space—instructional material, a writing space and planning templates—this tool aimed to provide a holistic approach to writing and writing development. This paper demonstrates how the tool was used in an academic course in order to address certain teaching and learning problems identified by the course tutor. Student feedback suggests that while further development is needed, the tool was still useful. This paper raises awareness of the complex array of issues involved in dissertation writing and provides insights into solutions to writing problems. While we designed what we considered to be a web‐based tool for dissertation writing, we argue that the writing space and planning templates go some way towards creating an environment for the development of learning (Häkkinen, 2002).
An incremental analysis of the value of expanding a wilderness area
Authors: Buttle Jonathan , Rondeau Daniel 
Published: April 2004

Abstract.
Forsyth (2000) concludes from an option value analysis that when considered together, Killarney Provincial Park and two adjacent parcels of land should be preserved in an expanded park. With a simple discrete difference approach, we assess the incremental value of the adjacent land and decompose the benefits of park expansion. We identify a change in the value of the option to log the current park as a new component of value not previously reported. Applying the method to Killarney suggests that logging may be the most efficient use of the adjacent land. We also provide corrections for some of Forsyth's numerical results. JEL Classification: D81, Q20.
Effects of island isolation and feral mink removal on bird communities on small islands in the Baltic Sea
Authors: Nordström Mikael , Korpimäki Erkki 
Published: April 2004

Summary

Predation has been suggested as a major cause affecting survival, reproductive success and behaviour in vertebrate prey populations. The breeding season is a critical phase because the essential difference between selecting the proper nest site may be a question of breeding success and failure.
Islands may serve as refuges for ground‐nesting birds against natural mammalian predators. However, many of the bird species breeding on islands are currently threatened by introduced predators because they may lack mechanisms to confront the threats of the new predator.
We studied the combined effects of an introduced generalist predator, American mink (Mustela vison Schreb.), and island isolation and size on species richness, abundance and equitability of birds breeding on small islands in the outer archipelago of SW Finland, Baltic Sea. The study comprised two mink removal areas (one during 1993–2001 and the other during 1998–2001) and two comparable control areas (during 1994–2001 and 1998–2001), each covering 72–130 km2, of which between 1·07 and 1·27 km2 were land area. The mean island size in all areas was < 2 ha.
In the two control areas, both the species richness and abundance were highest on the most isolated islands, while isolation did not have obvious effects on these variables in mink removal areas. Species equitability was not influenced by mink removal or island isolation.
The distribution of a maritime species, the razorbill (Alca torda L.), has changed dramatically: in the 1973–74, before mink invaded the area, the species was found commonly on less isolated islands than in 1994, after mink invasion.
We suggest that in the presence of mink birds may have changed their breeding site selection and started to breed on the most isolated islands, which are not visited by mink as frequently as less isolated islands. Therefore, our results indicate that increasing island isolation may increase the number of bird species and their numbers, because island isolation slows down mink dispersal.
Strong density dependence in a predatory insect: large‐scale experiments in a stream
Authors: Hildrew Alan G. , Woodward Guy , Winterbottom Julie H. , Orton Stuart 
Published: April 2004

SummaryEmpirical information about the intergenerational dynamics of stream insects is scarce, and most field experiments are conducted at small temporal and spatial scales that are inappropriate for assessing effects upon population dynamics. We performed a large‐scale, intergenerational population manipulation of an abundant, stream‐dwelling predator, the alderflySialis fuliginosa, by altering its recruitment over 3 consecutive years (it has a 2‐year life cycle).Experimental treatments were assigned to three contiguous 150‐m stretches. Each year at least 92% ofS. fuliginosaeggs, that are laid on the streamside vegetation, were removed from an upstream ‘removal’ stretch and transferred below an adjacent ‘control’ stretch to a downstream ‘addition’ stretch, where recruitment was thus effectively doubled.Although manipulations were successful initially, the effects were transient. Strong density‐dependent survival stabilized the population at a similar density in all three stretches within the first 4 months of life for the 1997 cohort and somewhat later for the 1998 cohort. Survey data suggested that intraguild predation (including cannibalism) and/or starvation, particularly early in the life cycle, might be regulating theS. fuliginosapopulation.It is intriguing that this abundant predator, which is linked very richly within the complex Broadstone Stream food web, has a strongly stabilized population, even in the face of such a dramatic perturbation in recruitment.
Long‐distance dispersal and human population density allow the prediction of invasive patterns in the horse chestnut leafminerCameraria ohridella
Authors: Gilbert M. , Grégoire J.‐C. , Freise J. F. , Heitland W. 
Published: April 2004

SummaryAfter its initial discovery in Macedonia in 1985, during the last 19 years the leafminer mothCameraria ohridellahas invaded most of Central and Western Europe. The species, which causes aesthetic damage to horse chestnuts, is generally observed first in highly populated locations before colonizing the countryside. This pattern is consistent with a stratified dispersal process combining long‐distance movements and local diffusion.Using large‐scale spatial data on damage caused byCameraria ohridellain Germany, three stochastic spatial models of spread are compared: a diffusion model, a leptokurtic dispersal model and a stratified dispersal model that assumes a two‐scale dispersal process. In addition, the association between human population and moth invasion is tested in this last model by linking long‐distance infestation probability to human population density. Finally, these spatial models constructed with data from Germany are tested at the European scale and compared to historical records of first occurrence.The fat‐tailed dispersal kernel models (leptokurtic and stratified dispersal models) allowing for long‐distance dispersal provide better predictions than the diffusion model. Among these models, the stratified dispersal model incorporating the effect of human population density provides the best description of the spread ofCameraria ohridellain Germany in predictive (lowest sum of squared errors) and qualitative (similar fractal dimension) terms.The roles of short‐distance and long‐distance dispersal inCameraria ohridellainvasion ecology in relation to human population are discussed, together with the models’ scale‐dependence and limitations.
Spatial scale, heterogeneity and functional responses
Authors: Bergström Ulf , Englund Göran 
Published: April 2004

Summary

In a laboratory experiment, we studied the effect of arena size on the functional response of the mysid shrimp Neomysis integer preying on the cladoceran Polyphemus pediculus. The aim of the study was to examine mechanisms that cause the functional response to be scale‐dependent, by documenting the spatial distribution and the movement behaviour of predator and prey.
The attack rate was significantly higher in large arenas, while the handling time did not differ between arena sizes. The difference in attack rate could be explained by differences in aggregative behaviour of predator and prey and in swimming activity of the predator. It is suggested that distributions of animals are often affected by the walls of the experimental arenas and that this spatial heterogeneity is scale‐dependent, which may have a considerable impact on estimates of ecological process rates.
A method of correcting attack rate estimates for artefacts caused by such spatial heterogeneity is presented.
Spatial abundance structures in an assemblage of gall‐forming sawflies
Authors: McGeoch M. A. , Price P. W. 
Published: April 2004

SummaryExamination of the fine‐scale internal structure of species geographical ranges, and interspecific variation therein across landscapes, contributes to a more comprehensive understanding of the structure of geographical ranges. Two components of this internal structure that require further examination are the occurrence, extent and position of spatial autocorrelation, and relationships between the spatial abundance structures of closely related, ecologically similar species.Here we compare the abundance structures of an assemblage of gall‐forming sawflies (Tenthredinidae) across a landscape. We identify the relative roles of spatial and non‐spatial factors in explaining their abundance structures and test the hypothesis that sawfly density is explained by host plant quality, as has been demonstrated repeatedly at finer scales. We use these results to distinguish between alternative sets of mechanisms that may be operating at the landscape scale.Species densities were mainly multimodal across the landscape and significantly spatially structured, with patch, periodic and trend components. The abundance structures thus mimic those found generally for species across the full extent of their geographical ranges.Many abundance structure characteristics were unique to species, with differences in their correlogram profiles, distances over which densities were positively autocorrelated, and the absence of significant spatial structure in one species.In contrast to previous, fine‐scale studies, host plant quality explained little of the variation in sawfly gall density across the landscape, whereas unexplained spatial structure contributed between 30% and 50%. Based on knowledge of the biology of these species and the absence of competitive interactions, species dispersal characteristics and the Moran effect are suggested as probable alternative hypotheses at this scale.Therefore, a spatial approach has identified the hierarchical nature of mechanisms underlying the population dynamics of this sawfly assemblage for the first time. Furthermore, it has highlighted the importance of spatial processes in explaining the densities of species at the landscape scale, as well as the individualistic nature of their abundance structures.