bluuebunny/crossref_metadata_2025 huggingface dataset:
IS METABOLOMICS THE DIAGNOSTIC TOOL FOR MEDICAL DIAGNOSTICS OF CANCER? AN EXAMPLE BASED ON LUNG AND BREAST CANCER
Authors: Lamasz A. , Barg W. , Mlynarz P.
Published: September 2018

Background. Metabolomics is a relatively new diagnostic tool that allows a deep insight into the body metabolism at a cellular level. Objective. This paper provides a comprehensive view into the metabolomic methodology and shows usefulness of this approach in diagnosing and stratifying lung and breast cancers. Methods. Literature review of metabolomics studies and its clinical application in the diagnosis of cancer-selected studies.Results. In general, the metabolomic approach comprises three steps: 1) sampling and preparing biofluids or tissue homogenates, 2) identification of low-molecular weight compounds up to 1.0 kDa using nuclear magnetic resonance, mostly 1H-NMR and/or mass spectrometry, and finally 3) data processing and analysing. It is possible to identify a set of metabolites which is specific for a certain metabolic status (the metabolic fingerprint). Furthermore, this set of metabolites provides information of possible pathomechanisms involved in the disease process i.e. information about the disease etiology. It has been proven that the change in metabolome precedes other biomarkers of the disease; not only clinical symptoms but other laboratory findings as well. Consequently, this approach, if sufficiently validated, seems to be very promising especially in screening and early diagnosing. Conclusions. It was demonstrated that metabolomic approach allows to discriminate patients with cancer from healthy persons, as well as to differentiate between clinical stages of the cancer.
EPIDEMIOLOGIC EVALUATION OF THYROID DISEASES MORBIDITY OF UKRAINIAN ADULT POPULATION FROM 2000 TO 2013
Authors: Antonenko A. M. , Korshun M. M. , Vavrinevych O. P. , Omelchuk S. T. , Bardov V. H.
Published: September 2018

Background. The diseases of thyroid gland have been attracting considerable attention in recent decades. This is partly due to the fact that thyroid gland reacts actively to geochemical state and pollution of the environment with industrial and agricultural waste products with the subsequent incidence of certain pathological processes. The objective of the research was to analyze the morbidity of adult population of Ukraine for thyroid gland diseases in the period from 2000 to 2013.Methods. The methods of empirical and theoretical research of scientific information: analysis, synthesis, induction, deduction and systematization, as well as epidemiological and statistical methods were used. Using the Microsoft Office Excel (2007) and IBM SPSS StatisticsBase v.22 program the correlation and regression analyzes were conducted.Results. From 2000 to 2013, high levels of adult population endocrinopathies, thyroid in general and diffuse goiter of varying degrees, general and primary morbidity were registered in the western and northern regions of Ukraine, low – in the central, eastern and southern regions. Statistically significant (p<0.001) positive correlation between the level of prevalence and the level of incidence of endocrine pathology, diseases of thyroid gland as a whole, as well as individual nosology was detected. Conclusions. Regional peculiarities of the levels and dynamics of changes in the incidence rates of thyroid morbidity among adult population of Ukraine can be related to the urgent environmental factors for each region. This factor requires further study to develop effective methods of prophylaxis and defense.
REACTIVE OXYGEN AND NITROGEN SPECIES ROLE IN EXPERIMENTAL PERIODONTITIS DEVELOPMENT
Authors: Demkovych A. Ye.
Published: September 2018

Introduction. Activation of lipid peroxidation is one of the trigger mechanisms of periodontium injury, which is primary caused by cellular damage. Reactive oxygen and nitrogen species (RONS) are able to cause damage to a cell as well as final products of lipid peroxidation, including unsaturated aldehydes and other metabolites. Objective. The aim of the research was to determine the role of RONS and accumulation of lipid peroxidation derivatives in initial development and formation of chronical inflammatory process in periodontium. Methods. Experimental periodontitis was modeled in animals by injection of complex mixtures of microorganisms diluted in egg protein into periodontal tissues. The results of biochemical studies of free radical processes activity in blood serum were evaluated by content of diene, triene conjugates, TBA-active products and total quantity of metabolites of nitric oxide (NO2–+NO3–), which were determined on the 7th, 14th and 30th days of the experiment. Results. Generation of active forms of oxygen is more influential, providing longevity of inflammatory process. This pays attention to typical dynamics of changes in active processes of lipid peroxidation in the development and course of experimental periodontitis. The study of inflammatory process with a bacterial-immune component in the rats’ periodontal complex proved accumulation of lipid peroxidation and nitric oxide metabolites in blood serum.Conclusions. The preservation of increased lipid peroxidation and nitric oxide metabolites in blood serum of the experimental animals with acute periodontitis conduce enhance of alteration and delayed healing that result in its sequel into chronical periodontitis.
Length-weight relationships of thirteen penaeoid shrimps in the East China Sea
Authors: Li Hui Yu , Yang Lin Lin , Cheng Jia Hua , Ling Jian Zhong
Published: September 2018

Length-weight relationships of various shrimp species were examined based on data from bottom trawl surveys from May 2014 to April 2015 in the East China Sea. A total of 2335 individuals belonging to Penaeidae and Solenoceridae were measured and weighed. Significant length-weight relationships were found for all species. The b-values of the length-weight relationships ranged from 2.0855 (Trachysalambria curvirostris) to 3.4808 (Metapenaeopsis barbata) with a mean value of 3.10 (±0.05). The differences in b-values between sexes and seasons were also examined. Whenever possible, b-values were compared for the species obtained both in this study and some of the species previously reported in other studies. Differences in the b-values for the same species in different areas suggest the influence of differences in environmental or habitat factors, including temperature and depth.
Two new species of rain beetle (Coleoptera: Pleocomidae: Pleocoma Le Conte, 1856) in the Pacific Northwest of the United State of America
Authors: MARSHALL CHRISTOPHER J.
Published: September 2018

A newly discovered population of rain beetles from south central Washington, United States of America is described as Pleocoma laker Marshall, new species. The only other species known from Washington, P. crinita Linsley, 1938, is restricted to include only populations north of the Columbia River. Rain beetles from Oregon, previously considered as P. crinita, are recognized as a distinct species: Pleocoma callisto Marshall, new species. A key to the identification of all described rain beetles in Oregon and Washington is provided.
Jocquestus, a new genus of trachelid sac spiders from the Afrotropical Region (Arachnida: Araneae)
Authors: LYLE ROBIN , HADDAD CHARLES R.
Published: September 2018

The new dark sac spider genus Jocquestus gen. nov. (Araneae: Trachelidae) is proposed for two species of Afrotropical trachelid spiders, J. schenkeli (Lessert, 1923) comb. nov. (type species) from D.R. Congo, South Africa, Mozambique and Zimbabwe, and J. roeweri (Lawrence, 1938) comb. nov. from South Africa, both of which are transferred from Trachelas L. Koch, 1872. Both species are redescribed and the male of J. roeweri comb. nov. is described for the first time. Five new species are described: J. capensis sp. nov. (♂ ♀), J. harrisi sp. nov. (♀) and J. incurvus sp. nov. (♂ ♀) from South Africa, and J. griswoldi sp. nov. (♂) and J. obliquus sp. nov. (♂ ♀) from Tanzania. Present data suggests that all of the species are arboreal spiders associated with the vegetation of woody plants in savanna, forest and fynbos habitats, and are only very rarely encountered near the soil surface.
The Dependence of Daily and Hourly Precipitation Extremes on Temperature and Atmospheric Humidity over China
Authors: Wang Hong , Sun Fubao , Liu Wenbin
Published: September 2018

Precipitation extremes are expected to increase by 7% per degree of warming according to the Clausius–Clapeyron (CC) relation. However, this scaling behavior is inappropriate for high temperatures and short-duration precipitation extremes. Here, daily data from 702 stations during 1951–2014 and hourly data from 8 stations during 2000–15 are used to examine and explain this behavior in China. Both daily and hourly precipitation extremes exhibit an increase in temperature dependency at lower temperatures. The CC scaling transitions from positive to negative rates with temperatures greater than 25°C. Unlike the increase in daily data, which is similar to single-CC (1CC) scaling, the increase in hourly data resembles super-CC (2CC) scaling for temperatures greater than 13°C. Results show that the precipitation extremes are controlled by water vapor for a given temperature. At lower temperatures, precipitation extremes exhibit a positive linear dependence on daily actual vapor pressure whose value is almost equal to the saturated vapor pressure at a given temperature. At higher temperatures, actual vapor pressure has difficulty maintaining a consistent increasing rate because of the exponential increasing of the saturated vapor pressure. Higher temperatures result in larger vapor pressure deficits, which lead to sharp decreases in precipitation extremes. Similar scaling behaviors are obtained in 10 river basins over China, where the breaking point temperature increases from 17°C along the northwest inland area to 25°C along the southeast coast. These behaviors demonstrate that precipitation extremes are firmly linked to temperature when there is sufficient moisture at lower temperatures and limited by insufficient moisture at higher temperatures. Overall, precipitation extreme events require more attention in a warming climate.
New Medications in the Treatment of Peanut Allergy
Authors: Walker Scot
Published: September 2018

In the general population, the prevalence of peanut allergy has remained stable at 1.3%. However, in children, the prevalence appears to be increasing. There are no approved treatments for peanut allergy so current treatment involves educating the patient on avoiding products that contain peanut protein. Two drugs that allow controlled desensitization with controlled amounts of peanut protein have reached late stages of development.
The Consequences of Long-Term Unemployment: Evidence from Linked Survey and Administrative Data
Authors: Abraham Katharine G. , Haltiwanger John , Sandusky Kristin , Spletzer James R.
Published: September 2018

That the long-term unemployed fare worse in the labor market than do the short-term unemployed is well-known, but why? One potential explanation is that the long-term unemployed are “bad apples” who had poorer prospects from the outset of their spells (heterogeneity). Another is that these bad outcomes are a consequence of their extended unemployment (state dependence). The authors use Current Population Survey data on unemployed individuals linked to unemployment insurance wage records for the same people to distinguish between these explanations. The rich work history information contained in the wage records allows the authors to control for individual heterogeneity that could affect post-unemployment labor market outcomes. Even with these controls in place, they find that unemployment duration has a strongly negative effect on the likelihood of subsequent employment. The results are robust to accounting for differences in the labor market conditions experienced by the long-term and short-term unemployed.
Attitudes About Suicide Ideation Among Suicide Loss Survivors: A Vignette Study
Authors: Kheibari Athena , Cerel Julie , Sanford Rebecca
Published: September 2018

This study aimed to examine the attitudes of college students toward suicide and nonsuicide loss survivors’ future suicide intent—specifically the degree to which each is believed to be suicidal based on the characteristics of the loss and relationship to the deceased. Participants were asked to read a descriptive vignette about a bereaved individual and assess their judgment about the survivor’s current state of suicide-related ideation. The results revealed that the likelihood of indicating suicide-related ideation was decreased by 5.9% for each year that the participant aged. This study provides useful knowledge about the perception of suicidal ideation among bereaved individuals.
Relationship of Emotional Eating and Mood Changes Through Self-Regulation Within Three Behavioral Treatments for Obesity
Authors: Annesi James J.
Published: September 2018

An enhanced understanding of the dynamics of psychosocial change processes within behavioral weight loss treatments is required to improve their generally poor results. Based on social cognitive theory, self-regulation of eating has the possibility of affecting interrelations between psychosocial correlates of inappropriate eating behaviors such as emotional eating and negative mood. Within behavioral interventions, physical activity, treatment foci, and the length of treatment might moderate those relationships. The aim of this research was to contrast intervention effects based on treatment type, and evaluate interrelations of changes in theory-based psychosocial variables. Adult females with obesity (overall Mage = 48.6 years; overall MBMI = 35.3 kg/m2) were block randomized into groups of 28 weeks of phone-supported manual-based education (Group 1, n = 52), 58 weeks of cognitive-behavioral group treatment (Group 2, n = 52), and 99 weeks of cognitive-behavioral group treatment followed by phone-based reviews of intervention materials (Group 3, n = 48). Significant improvements in measures of emotional eating, negative mood, self-regulation for controlling eating, physical activity, and body composition were found in each group over 3, 6, 12, and 24 months, with generally larger effect sizes detected in Groups 2 and 3. Reciprocal, mutually reinforcing, relationships were found between changes in emotional eating and mood, which were significantly mediated by self-regulation changes. Physical activity level significantly moderated mood changes, treatment foci on emotional eating significantly moderated changes in emotional eating, and treatment length significantly moderated long-term changes in emotional eating, but not mood. Findings support a treatment duration of at least one year that emphasizes physical activity and self-regulatory skills usage, and interrelations between changes in emotional eating, self-regulation, mood, and physical activity.
Modeling of wear sound production based on mechanical and friction properties of woven fabric
Authors: Leclinche Floriane , Adolphe Dominque C , Drean Emilie , Schacher Laurence , Zimpfer Véronique
Published: September 2018

The objective of this study is to analyze the characteristics of frictional sounds and to determine correlations between sound parameters and mechanical properties of fabrics classically used for protective garments. The set of samples includes six fabrics whose surface was previously worn out at different degrees using a Martindale abrasion tester. The frictional sounds were obtained by a device reproducing the friction engendered under arm during walking and were recorded and analyzed using Fast Fourier Transform (FFT) analysis. In addition, the mechanical properties of samples were measured using the Kawabata Evaluation System. The FFT spectra of fabrics showed different shapes and different noise levels according to the degree of wear. Several correlations between sound parameters and mechanical properties were highlighted. It was shown that the garment’s wear increases the sound level of rustling sounds.
Preparation, structure and electrochromic behavior of PANI/PVA composite electrospun nanofiber
Authors: Meng Na , Wang Xiangqin , Xin Binjie , Chen Zhuoming , Liu Yan
Published: September 2018

In this study, the preparation of polyaniline/polyvinyl alcohol (PANI/PVA) emulsion and the fabrication of PANI/PVA nanocomposite and electrochromic device are presented systematically. The surface morphologies, chemical structural and mechanical properties of the PANI/PVA nanofibers were characterized using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and instrumental equipment. Four PANI/PVA composites with different PANI concentrations (i.e. 0 wt%, 0.2 wt%, 0.4 wt%, 0.6 wt%) were prepared to investigate the effects of PANI content on the electrochemical properties of the composites. Electrochromic properties of these PANI/PVA electrospun composite nanofibers are systematically characterized by an electrochemical workstation. Cyclic voltammetry was conducted to measure the electrochemical behavior of the PANI/PVA electrospun composite nanofibers at scanning speeds of 5 mV/s, 20 mV/s, 50 mV/s and 100 mV/s; it could be found that the redox peaks almost disappear. The discoloration of PANI/PVA composite electrospun nanofiber presents the color changing among the three mainstream colors of green, yellow, and blue.
From creator to data: the post-record music industry and the digital conglomerates
Authors: Negus Keith
Published: September 2018

This article contributes to research on the changing music industries by identifying three dynamics that underpin the shift towards a post-record music industry. First, it examines how musicians have found themselves redefined as content providers rather than creative producers; a historical change from recorded music as product to content. Second, it focuses on tensions between YouTube and recording artists as symptomatic of disputes about the changing artistic and economic value of recorded music. Third, it extends this debate about the market and moral worth of music by exploring how digital recordings have acquired value as data, rather than as a commercial form of artistic expression. The article explores how digital conglomerates have become ever-more significant in shaping the circulation of recordings and profiting from the work of musicians, and highlights emergent dynamics, structures and patterns of conflict shaping the recording sector specifically, and music industries more generally.
The Polyethylene Casing as Diffusion Barrier for Polyurethane Insulated District Heating Pipes
Authors: Olsson Maria , Jarfelt Ulf , Fröling Morgan , Ramnäs Olle
Published: September 2018

Most district heating pipes are insulated with polyurethane foam in order to minimise heat losses. A high-density polyethylene (HDPE) casing protects the insulated pipe, and its permeability properties for the polyurethane cell gases, including air, play an important role for the long-term insulating capacity.

The permeability of the HDPE casing of a district heating pipe was studied. Two methods were used to determine the permeability: I) by measuring the mass transfer through a sample, and II) by measuring the sorption and desorption of the gas in a sample. The experimental procedures are described. For carbon dioxide a permeability coefficient of about 9·10-16 mole·m-1·s-1·Pa-1 was found by both methods. For oxygen and nitrogen only method I was used and the permeability coefficients found were 1.9 and 0.6·10-16 mole·m-1·s-1·Pa-1, respectively.
The Effect of Chemical Composition, Density and Cellular Structure on the Dynamic Mechanical Response of Polyolefin Foams
Authors: Rodríguez-Pérez M.A.
Published: September 2018

Dynamic mechanical analysis has been applied to a collection of polyolefin foams with different chemical compositions and densities and manufactured from different routes. The effect of different foam characteristics, such as density, polymer morphology and cellular structure on the dynamic mechanical response is analysed. The way in which this technique can be used to obtain information about the polymer morphology of the foam is presented. In addition, examples of the use of this technique in studying specific problems are illustrated.
Ethylene – Styrene Interpolymer Foam Blends: Mechanical Properties and Sport Applications
Authors: Ankrah S. , Verdejo R. , Mills N.J
Published: September 2018

Mechanical tests were performed on foamed blends of Ethylene – Styrene Interpolymer (ESI) with low density polyethylene (LDPE). In compressive impact tests the foams, of density around 50 kg m-3, have higher initial yield stresses than Ethylene Vinyl Acetate (EVA) foam of the same density. Impact, Instron and creep tests were analysed to estimate the effective air pressure in the undeformed foam cells, and the initial yield stress. The rate dependence of the latter increases slightly with increasing ESI content. The ESI/LDPE foams have improved impact properties, compared with EVA foams of similar density, for leg protection applications. Analysis of creep tests shows that air diffuses from the cells at a similar rate to EVA foams of a greater density. The ESI/LDPE foams have potential to replace higher density EVA foams in running shoes.
Microcellular Wood Fibre Reinforced Polypropylene Composites in an Injection Moulding Process
Authors: Bledzki Andrzej K. , Faruk Omar
Published: September 2018

Microcellular foams of polypropylene containing wood fibres, cell sizes on the order of 10 to 50 μm were produced by injection moulding. The relationships of processing/structure/property were investigated for wood fibre-thermoplastics composites foaming with a chemical blowing agent. Wood polypropylene composites (WPC) of different wood content (30%, 40%, 50% and 60% by weight) were prepared using maleic anhydride-polypropylene copolymer (5% relative to the wood fibre content) as a coupling agent. Measurement of density, cell size, void content, tensile and flexural test of the prepared WPC were carried out. The shape and distribution of the voids were investigated by optical photo examination of longitudinal sections of specimens, using a polishing technique and reflected light microscopy. The density of foamed composites decreased about 24%. The cell morphology and foam properties showed improvement when the coupling agent was added. Water absorption and scanning electron microscope of the composites also investigated.
Influence of Polyether Copolymer Configuration on Polyurethane Reaction: A Mass Spectrometry Analysis
Authors: Suen Wu , Percy Jennifer , Hsu Shaw L. , Kaltashov Igor A. , Stidham Howard D.
Published: September 2018

Matrix Assisted Laser Desorption Ionization Time-of-Flight mass spectrometry has been applied to obtain the molecular weight distribution of two polyether copolymers containing ethylene oxide and propylene oxide units. The measured molecular weights and their distributions were surprisingly different from the expected. Based upon the natural isotopic abundance, it was possible to provide a quantitative description of the number of ethylene oxide and propylene oxide units as a function of molecular weight. Important information on composition drift and heterogeneity can be obtained from the 3-D bivariate deconvolution of the mass spectra. As the molecular weight of a random copolymer increased, the ethylene oxide content also increased. A copolymer system with a narrow molecular weight distribution did not necessarily have a narrow composition distribution. These results provide information at the molecular level regarding the hydrophilicity of these copolymers used in polyurethane formulations.
Key Processing Parameters for Microcellular Molded Polystyrene Material
Authors: Leicher S. , Walter A. , Schneebauer M. , Wagner M. , Kopp T. , Wintermantel E.
Published: September 2018

Microcellular injection molding was used as processing method to generate porous samples made of polystyrene material. A promising application for this kind of structures is the use as three dimensional cell culture substrate. The influence of key processing parameters on the morphology of the porous structures was examined. An increase in injection speed and a temperature decrease of the polymer melt decreased pore sizes whereas an increase in the degree of weight reduction increased pore sizes. Polystyrene samples with average pore sizes from 23 to 92 μm were produced.
Prediction of Cushion Curves for Closed Cell Polyethylene-Based Foams. Part II: Experimental
Authors: Ruiz-Herrero J.L. , Rodríguez-Pérez M.A. , de Saja J.A.
Published: September 2018

In this paper the compressive impact behaviour of a collection of low density polyethylene (LDPE) and polyethylene-co-vinyl acetate (EVA) based foams with different densities, during purely compressive impacts, has been studied. The experimental cushion curves for these materials were compared with several theoretical models. The results have shown that the simplest models, adiabatic and isothermal, are able to fit the experimental data and to predict qualitatively the evolution of the minima in the cushion curves as a function of foam thickness and falling height. In addition, it has been shown that the impact behaviour of closed cell polyethylene based foams deteriorates after compressive creepperiods. This fact should be considered in the design of real cushion systems.
Gas Diffusion in Polyolefin Foams during Creep Tests. Effect on Impact Behaviour and Recovery after Creep
Authors: Rodriguez-Perez M.A. , Ruiz-Herrero J.L. , Solorzano E. , de Saja J.A.
Published: September 2018

A method to obtain the effective diffusion coefficient of the gas contained in closed cell polyolefin foams under static loading is presented. This property is obtained from pressure decrease with time using an analytical solution of the diffusion equation. The effect of density, type of base polymer, crosslinking and sample size on the diffusion coefficient is analysed.

It has been shown that the impact behaviour of low density closed cell polyethylene based foams deteriorates after compressive creep periods and that this reduction of the cushion capabilities is directly related with the diffusion coefficient of the foams.

Moreover, the recovery of the foams after creep showed a peculiar non-homogeneous behaviour, which has been analysed. Gas diffusion during creep is the main responsible for this particular behaviour.
Compression Molding of Polyethylene Foams under a Temperature Gradient: Morphology and Flexural Modulus
Authors: Barzegari Mohamad Reza , Yao Jiaolian , Rodrigue Denis
Published: September 2018

For any type of polymer foam, it is well known that careful control of the processing temperature has an important effect on final morphology. In this work, density graded polyethylene foams were produced by imposing a temperature gradient while foaming the sample. This was done by controlling independently the top and bottom plates of a compression mold at different temperatures. By doing so, different density profiles across the part's thickness are produced. In this work, the resulting morphologies are presented with their respective flexural moduli.
Experimental Study on Microstructural, Surface Hardness and Flexural Strength of Injection Molded Microcellular Foamed Parts
Authors: Rezavand Seyed Abdol Mohammad , Behravesh Amir Hossein , Mahmoodi Mehdi , Shahi Peyman
Published: September 2018

This paper presents an experimental study on microstructural and mechanical properties of injection molded microcellular foamed parts. The effects of shot size, injection pressure and mold temperature on the relative density, unfoamed skin thickness, cell population density, surface hardness and flexural strength of various regions of the injected parts were investigated. A conventional injection molding machine was modified to produce microcellular acrylonitrile butadiene styrene (ABS) foamed plates. Nitrogen gas was used as the blowing agent. The results showed that surface hardness of microcellular foamed parts are higher and their flexural strength is lower than those of the unfoamed parts. Examining the properties throughout the parts confirmed distinct variations.
Effect of the Convergent-Filamentary Die Geometry on Volume Expansion of PS Foams Blown with CO2
Authors: Xu Donglai , Park Chul B. , Fenton Robert G.
Published: September 2018

This paper presents the effects of the convergent-filamentary die geometry on the volume expansion behaviors of extruded PS foams blown with supercritical CO2. Three groups of interchangeable convergent-filamentary dies were designed to thoroughly represent the die parameters. The experimental results reveal that the die geometry affects volume expansion of the extruded foams through its influences on the die pressure, the pressure-drop rate, and the amount of premature cell growth inside a convergent-filamentary die. Compared with the constant pressure-drop rate for a straight die, the pressure-drop rate for a convergent die increases along the die land, which is favorable for promoting cell nucleation and suppressing premature cell growth. Although the convergent shape is favorable for volume expansion, foams with a low expansion ratio were produced for those dies with a low pressure and a low pressure-drop rate because of the promoted premature cell growth.
Thermal and Mechanical Effects in Polystyrene-Montmorillonite Nanocomposite Foams
Authors: Ogunsona Emmanuel , Ogbomo Sonny , Nar Mangesh , D'Souza Nandika Anne
Published: September 2018

Nanocomposite polystyrene (PS) foams based on montmorillonite layered silicate (MLS) as nanofillers were prepared using in-situ polymerization of styrene. These nanocomposites were characterized for their thermal and mechanical properties using differential scanning calorimetry (DSC), x-ray diffraction (XRD), dynamic mechanical analyzer (DMA) and scanning electron microscope (SEM). Foamed sample microscopy revealed that the cell size reduced with the increasing amount of nanofiller. The mechanical properties showed a significant increase.
X-ray Microtomographic Study of Nanoclay-Polypropylene Foams
Authors: Ma Y. , Pyrz R. , Rodriguez-Perez M.A. , Escudero J. , Rauhe J.Ch. , Su X.
Published: September 2018

In the present paper X-ray microtomography technique has been applied to investigate internal, three dimensional structure of clay/polypropylene nanocomposite foams. Several sets of foam samples were prepared using the improved compression moulding technique that allows controlling independently the cells‘ size, cells‘ shape and density of foams. Then the X-ray images were acquired followed by an application of image processing steps and final reconstruction of foams microstructure. Volume distribution of cells has been extracted from three dimensional images and related to processing parameters. Since not only the size but also the shape of cells influences a load bearing capacity of foams, the sphericity parameter has been selected as a relative quantifier of cells shape. The sphericity parameter has been also related to different processing parameters.
Acoustic Properties of Tea-Leaf Fiber Mixed Polyurethane Composites
Authors: Çelebi Seçkin , Küçük Haluk
Published: September 2018

Natural tea-leaf fibers were used as reinforcement agents in different polyurethane-based matrixes to improve the sound absorption properties of the composite. Adding tea-leaf-fibers to rigid polyurethane foam demonstrate limited contribution to sound absorption properties of the material. Furthermore, adding tea-leaf-fibers to soft foam results in a significant improvement of sound absorption properties of the composite. In this study herein, the composite including 24% tea-leaf-fibers was observed to provide the best sound absorption coefficient. Additionally, soft foam demonstrates better acoustic properties than rigid foam.
Mode III Fracture Study of Foam Core Composite Sandwich Beams
Authors: Rizov V.
Published: September 2018

The present paper is concerned with the problem of mode III fracture in foam core composite sandwich beams. Three-dimensional linear-elastic finite element simulations were performed of sandwich beams with a crack in the mid-plane of the core. The load of the sandwich beam was chosen such that the cross-sectional bending moment in the arms at the crack front was reduced to zero in order to minimize the mode II fracture. Within the finite element analysis, the fracture was studied in terms of the strain energy release rate using the virtual crack closure technique. The calculations revealed that pure mode III loading conditions were induced along the crack front, except a small zone near the free edges of the sandwich beam cross-section, where mode II component of the strain energy release rate was also found. The influence of the sandwich core material on the mode III fracture was analyzed. For this purpose, three sandwich beam configurations were considered (it was assumed that the sandwich core was made by three different rigid cellular foams). It was found that the strain energy release rate decreases with increase of the sandwich core density.
Rheological and Thermal Behaviour of Different Molecular Structure Polypropylene Blends
Authors: Wei Liu , Bengang Liu , Xiangdong Wang
Published: September 2018

High melt strength/block polypropylene (HMSPP/PPB) blends and high melt strength/random polypropylene (HMSPP/PPR) blends were prepared by a twin-screw extruder to decrease the high stiffness of polypropylene and to improve its impact strength. Rheological properties of the two blends were investigated using a rotational rheometer. The complex viscosity and storage modulus data at low frequency region indicated that the melt elasticity and melt strength of the blends were affected by varying the content of PPB and PPR in the blends. Moreover, the melt strength of HMSPP/PPR blends was better than that of HMSPP/PPB. The non-isothermal crystallization behaviour of the blends was studied using differential scanning calorimetry with various cooling rates and was analyzed by the Avrami method. It was found that the melt and crystallization temperatures of the blends increased with the ratio of PPR and PPB. PPB also changed the crystallization process of the blends, leading to smaller spherulite size and more spherulites, but PPR only slightly affected the crystal behaviour.
Bulk Density Reduction of Injection Molded Thermoplastic Foams via a Mold Design Approach
Authors: Ahmadzai Ahmad Zia , Behravesh Amir Hossein
Published: September 2018

This study investigates the inter-relationships amongst processing parameters and mold design and their effects on relative density of injection molded foams. The limitation in lowering the overall bulk density of polymeric foams is one of the main drawbacks in injection foaming process. A sheet mold with a rectangular cavity was designed and manufactured which, includes an overflow channel connected with the main cavity via a secondary gate, the size of which was varied in this research. The effects of three parameters including chemical blowing agent weight percentage, gate width, and part thickness on reduction of relative density were investigated. Full factorial test experiments were applied in this research work. The results were used to determine the optimum conditions in terms of low foam bulk density and high cell density. The results showed that enhanced cell structure can be achieved at a larger part thickness and adjusting the secondary gate to an optimum thickness. The conclusions revealed that part thickness and secondary gate width were the most influential factors on reduction of relative density and part weight.
Properties and Physical Structure of Cellular PVC Coatings
Authors: Garbacz Tomasz
Published: September 2018

The production of cellular coatings made of polymeric materials by the extrusion process differs from solid coating extrusion in that the polymer produced by the process based on the application of blowing agents has a diphase structure (gas-polymer) with small and evenly distributed gas bubbles. The research described in the paper was conducted using blowing agents with endothermic and exothermic decomposition behaviours, dosed as pellets in the range from 0.4% to 0.8% by weight relative to the weight of the polymer being processed. The extrusion process for modified PVC was conducted using the technological line for the production of electrical cable coatings.

The content of the blowing agents applied in the tests in the amount of up to 0.8 wt% was selected in such a way as to produce cables with a solid coating and center coating. The appearance of the produced cable coatings, their thickness and dimensions comply with the current norms.

In the investigated range of the blowing agent content, the temperature of the extrudate leaving the head decreased by approximately 7%, which can probably be attributed to the endothermic blowing agent decomposition behaviour in the extruder head.

The mechanical properties of cellular products, including their hardness, are affected by the macromolecular shape, orientation and bond. A lower number of cross-linkages in the cellular polymeric material means decreased strength properties of such product.

The results of the cellular coating resistance to water and oil absorption have demonstrated considerably increased absorption of the coatings produced, depending on the residence time in the aggressive environment and type of blowing agent applied.

Analyzing the results of density, porosity and optical examination of the physical structure of thin-walled cellular coatings, it has been determined that the favourable content of the blowing agent in the polymer should amount to 0.6-0.8 wt%, which leads to density decrease by approximately 40%.
Preparation and Characterization of Biopolyols and Polyurethane Foams from Liquefied Faba Bean Stalk
Authors: Zhang Wenming , Li Ling , Li Qing , Li Xiaowei , Zhang Yucang
Published: September 2018

In this study, Faba bean stalk was liquefied for the production of biopolyols and polyurethane (PU) foams. The influences of various reaction conditions on biopolyols and PU foams were examined. Furthermore, the property relationships between biopolyols and PU foams were investigated. Biopolyols produced under the liquefaction conditions of 160°C, 90 min, 3% sulfuric acid loading, and 20% Faba bean stalk loading showed promising material properties (i.e. hydroxyl number, 496.1 mg KOH/g, acid number, 17.9 mg KOH/g, and viscosity, 1.1 Pa.s). PU foams produced from promising biopolyols showed compressive strength of 205 kPa and density of 0.035 g/cm3. The results suggested that in addition to density, the compressive strength of PU foams might also be affected by factors such as biomass residues or the chemical structures of biopolyols. The biopolyols and PU foams produced showed material properties comparable to those of conventional PU foams.
The Preparation and Characterization of Branching Poly(ethylene terephthalate) and its Foaming Behavior
Authors: Liu Haiming , Wang Xiangdong , Zhou Hongfu , Liu Wei , Liu Bengang
Published: September 2018

Chain extension was an effective method for increasing the molecular weight, the melt strength and the foaming property of linear polymer. In this paper, pyromellitic dianhydride (PMDA) was used as chain extender to improve these properties of linear poly (ethylene terephthalate) (PET). The intrinsic viscosity, rheological and thermal characterizations of various PET samples was investigated. The results demonstrated that the increasement of the viscoelasticity at low frequencies was correlated to the raise of the intrinsic viscosity and the formation of long chain branching. These structural changes resulted in the decreasement of the crystallization temperature and melt temperature as well as the increase in the cold crystallization values with the increasing content of PMDA. The cellular morphology and expansion ratio of CEPET foams were also obviously improved by the introduction of PMDA. The expansion ratio of CEPET foam with the PMDA content of 1.0 phr would reach 31.78. In addition, the effect of the chain extension reaction time on the intrinsic viscosity, the rheological behavior, and foaming properties of PET were also studied. The results showed that the intrinsic viscosity, the rheological behavior, and the foamability of CEPET also decreased gradually with increasing chain extension reaction time, which should be attributed to the occurrence of more and more intense thermal degradation.
Quantitative Assessment of the Microscopic Structure of Extruded and Injected Low-Density Polyethylene Modified with Microspheres by Image Analysis
Authors: Tor-Świątek Aneta , Garbacz Tomasz , Jachowicz Tomasz
Published: September 2018

The paper investigates the macroscopic structure of low-density polyethylene modified with polymer microspheres. The analysis is performed on specimens produced by extrusion and injection molding with the following contents of the modifying agent: 0.25%, 0.5% and 1%. The structure of the specimens is examined in six measuring regions by image analysis. In addition, the number and diameter of produced micropores and their area fraction are determined.
Fabrication of High Temperature Polyphenylsulfone Nanofoams Using High Pressure Liquid Carbon Dioxide
Authors: Guo Huimin , Nicolae Andrei , Kumar Vipin
Published: September 2018

In this paper, we describe fabrication of micro- and nano-structured foams in high temperature polyphenylsulfone (PPSU) with a Tgof 219°C using a solid-state carbon dioxide (CO2) foaming process. We have fabricated microcellular foams with cell size in 1–10 μm range, and for the first time, nanocellular foams with cell size in 20–40 nm range. We discovered a critical CO2concentration window 10.5%–11.8%, where a rapid 2–3 orders of increase in cell nucleation density is observed and cell size drops to below 100 nm. Two approaches are demonstrated to create PPSU nanofoams with a cell size of 20–40 nm: increasing saturation pressure to 7 MPa or decreasing saturation temperature to 10°C. Both approaches use high pressure liquid CO2and the CO2concentration in the polymer are above the critical concentration window, which result in the formation of nanocells. At high CO2concentration of 11.8% and 13%, as foaming temperature increases, the nanostructures transition from closed structure to an open porous structure.
Effect of Nanoparticle Modification on Static and Dynamic Behaviour of Foam Based Blast Energy Absorbers
Authors: Drdlová Martina , Frank Michal , Buchar Jaroslav , Rídký Řadek , Šoukal František
Published: September 2018

The effect of multi-wall carbon nanotubes and nanosilica (nano SiO2) content on physico-mechanical properties of glass microspheres-epoxy resin composite, designed for blast energy absorbing applications, was evaluated experimentally. Specific porous lightweight foam with high volume fraction of microspheres (70 vol.%) was prepared and modified by 1 to 5 vol.% of multi-wall carbon nanotubes and nanosilica. Compressive and flexural strength tests were conducted at quasi-static load. Split Hopkinson Pressure Bar apparatus was used to obtain high velocity characteristics of the materials. The relative absorbed energy was calculated to assess the relation between the composition of the material and its shock wave attenuation capacity. The mixtures containing nanosilica exhibited an increasing trend in the energy absorption capacity with increasing nanoparticle content up to 4 vol.%. The addition of carbon nanotubes also increased absorbed energy (again up to 4 vol.%, a significant drop was observed at higher concentrations). Comparing the values of the relative absorbed energy, the carbon nanotubes composites prevail over the nanosilica modified ones.
The Influence of Blowing Agent Addition, Glass Fiber Filler Content and Mold Temperature on Selected Properties, Surface State and Structure of Injection Molded Parts from Polyamide 6
Authors: Palutkiewicz Pawel , Garbacz Tomasz
Published: September 2018

The effects of blowing agent and glass fiber addition and also mold temperature on selected properties of PA6 molded parts was presented in this work. Blowing agent was dosed to plastic in amounts 0.5 – 1%, and glass fiber was added in amounts 15 – 30%. Furthermore, molded parts from unfilled and unfoamed PA6 was also investigated. The experimental plan was prepared using Design of Experiments (DoE) method. The results of selected part properties: molded parts weight, thickness, hardness, impact strength, tensile strength, elongation at maximum force, and also surface state of molded parts (gloss and color) was presented. The article also presents microscopic investigations (using SEM method) of molded parts with blowing agent and glass fiber. It was found, that the glass fiber content has a larger impact on mechanical properties of parts than addition of blowing agent. The use of the blowing agent in an amount of 1% wt. will allow the reduce injection cycle time by reducing the hold pressure and hold time, without significant worsening their properties. The mold temperature has an impact especially on the gloss of molded parts and the pore size.
Microstructure, Mechanical and Thermal Properties of Three-dimensional Braided Glass Fiber Reinforced Phenolic Cryogel Composites
Authors: Yao Rui , Yao Zhengjun , Zhou Jintang
Published: September 2018

Phenolic cryogel plates (PCPs) and three-dimensional braided glass fiber reinforced phenolic cryogel composite plates (PCCPs) were successfully fabricated by microemulsion-templated sol gel polymerization and freeze-drying methods. Then, pore morphology, mechanical and thermal properties of the composites were investigated. The experimental results showed that the aerogels made by freeze-drying method had the best microstructure. In addition, it was discovered that the compressive and tensile strength of the cryogel plates had equally increased for approximately 8 and 30 times after compounding with glass fiber. Simultaneously, the mechanical properties of the 20 wt% and 25% solid content (PCPs) achieved the optimal value compared with PCPs of other contents. Moreover, it was found that the cryogels had excellent thermostability, and their thermal conductivity decreased with the reducing of the solid contents, what's more, the joining of glass fiber had the increased the composites’ thermal conductivity to some degree. Finally, considering the requirement of low density, good mechanical and thermal performance, the 20 wt% solid content PCCP had the best comprehensive performance compared with others.
Sound Absorption Properties of Syntactic Foam Reinforced by Warp-knitted Spacer Fabric
Authors: Zhi Chao , Long Hairu
Published: September 2018

The aim of this study is to investigate the sound absorption properties of syntactic foam reinforced by warp-knitted spacer fabric (SF-WKSF). SF-WKSF was served as micro-perforated panel (MPP) sound absorber and different kinds of SF-WKSF samples were fabricated with warp-knitted spacer fabric (WKSF) of various surface layer structures and parameters. These parameters included inclination angle and fineness of spacer yarns, air cavity depth, microballoons types as well as microballoons contents. The acoustical behaviors of SF-WKSF and neat syntactic foam (NSF) were tested according to transfer function method. The results show that the SF-WKSF has better sound absorption properties compared to NSF. It is also demonstrated that the fabric surface structures, spacer yarn fineness and inclination angle, air cavity depth, microballoons contents and types have significant effects on the sound absorbability of SF-WKSF, meanwhile their performances of absorbing noise can be tailored by adjusting the parameters of spacer fabric, microballoons or air cavity.