bluuebunny/crossref_metadata_2025 huggingface dataset:
Functional Communication Training: The Strength of Evidence Across Disabilities
Authors: Gerow Stephanie , Davis Tonya , Radhakrishnan Supriya , Gregori Emily , Rivera Gabby
Published: September 2018

Functional communication training (FCT) is a commonly used, often recommended intervention that involves teaching a functionally equivalent communicative response to replace challenging behavior. The purpose of this literature review was to evaluate the strength of the evidence for the use of FCT. A systematic review of the literature resulted in the identification of 215 single-case-design articles that evaluated the efficacy of FCT to reduce challenging behavior for individuals diagnosed with a disability. FCT resulted in a decrease in challenging behavior for 135 participants. The reviewers rated FCT as an evidence-based practice for individuals with autism, intellectual disability, other health impairments, and multiple disabilities based on What Works Clearinghouse standards. Overall, the extant literature indicates FCT consistently results in the reduction of challenging behavior in children with disabilities. Implications for practice and directions for future research are discussed.
Trump’s National Security Strategy: “America First” meets the establishment
Authors: Ettinger Aaron
Published: September 2018

Donald Trump’s 2017 National Security Strategy (NSS) promises to put “America first.” However, it is only a partial break from convention, and evinces a deep current of incoherence in Trump’s foreign policy. The NSS attempts to combine two incompatible worldviews into a single doctrine: the president’s “America First” nationalism and the seventy-year-old internationalist consensus among the US foreign policy establishment. Not only does it betray strategic dissonance, it portends an impossible working relationship between Trump’s insurgent nationalism and the traditionalism of the US foreign policy bureaucracy.
Canadian provinces and foreign policy in Asia
Authors: Labrecque Charles-Louis , Harrison Scott
Published: September 2018

Non-central governments in Canada have become increasingly active on the world stage, most notably in the Asia Pacific region. The scholarly works on Canada’s foreign policy in Asia tend to focus either on the federal government as the main actor, or on the “other diplomacies” of non-governmental actors; little attention has been paid to the increasing role of non-central governments in Asia. This article, therefore, contributes to the discussion by documenting and evaluating Canadian provinces’ international activities in the Asia Pacific. It also situates these activities within Canada’s foreign policy in the region, and assesses how important provinces have become in Canada–Asia relations. This paper first reviews the literature on non-central governments and foreign policy to expose the key forces pushing and pulling Canadian provinces to be increasingly active internationally. It then details the provinces’ international activities in Asia, and locates them within Canada’s foreign policy in the region.
Facing China: Canada between fear and hope
Authors: Paltiel Jeremy
Published: September 2018

This paper examines the challenges Canada faces in forging a diplomacy appropriate for the changing power configuration in global politics. The reshaping of the international order—with China pushing for a more hierarchical view of international relations, and the administration of Donald Trump repositioning the USA in global politics—provides Canada with the impetus to rediscover the traditional role that middle powers played as reliable middle managers for the global project. Today, such “middle management” is deprived of a reliable role. Since China has yet to articulate a coherent normative vision of a new global order, and the USA is retreating to a purely transactional view of trade and diplomacy, Canada and other middle powers have few choices other than to try to adapt to the changes in the hopes of sustaining the normative mesh that has upheld the post-war order.
An uncomfortable truth: Canada’s wary ambivalence to Chinese corporate takeovers
Authors: Chin Gregory T.
Published: September 2018

This article examines the behavioural patterns of successive Canadian governments in responding to three takeover attempts of iconic high-value Canadian corporates by large state companies from China. The first is China Minmetals Corporation’s attempt to acquire Noranda in 2004–2005 during the Liberal government of Paul Martin, the second is China National Offshore Oil Corporation’s acquisition of Nexen in 2012 during the Conservative government of Stephen Harper, and the third is China Communications Construction Corporation International’s bid for Aecon Group in 2017–2018. This analysis highlights some important similarities in the behavioural response of the Canadian governments across the three cases: ambivalence and wariness. Policy lessons are addressed in the conclusion.
The short story in South Africa post-2000: Critical reflections on a genre in transition
Authors: Fasselt Rebecca , Sandwith Corinne , Soldati-Kahimbaara Khulukazi
Published: September 2018

This editorial offers critical reflections on short story writing in South Africa post-2000. Against the background of critical scholarship on the short story form and thematic trends of short story anthologies since the late 1980s, we argue that short story criticism on apartheid as well as contemporary South African short story writing has consistently emphasized the genre’s disposition to capture the fragmented realities of socio-political transitions in the country. Critics have frequently observed a shift from the overtly politicized short story of the 1970s and 1980s to a return to a more literary and modernist aesthetics in the present. In this special issue, we intend to complicate this reading by mapping out other trajectories the short story has taken in recent years, which point toward the emergence of more popular subgenres such as speculative fiction, crime fiction, and erotic fiction. Short stories also increasingly examine and challenge conventional sexuality and/or gender-based norms.
Deconstructing a Double-Barreled Alternative: Evolution and Creationism
Authors: Grant Levy Sheldon
Published: September 2018

The problem of assessing opinions through surveys with double-barreled items has long been recognized, but nonfield experiments that examine their construction have been limited. Opinions about evolution based on an international multidecade Gallup survey were examined through an experimental design in which answers to the Gallup alternatives, one of which was double-barreled, were compared to those obtained when the components were separated. Random assignment of the original and deconstructed versions to 302 university students resulted in relatively few students who received the deconstructed version providing a pattern of answers that replicated the original item. The Harris organization had previously examined the Gallup survey, but the problem of deconstructing a double-barreled alternative in combination with an experimentally controlled procedure had not been demonstrated. The discussion includes a distinction between complex and compound (double-barreled) survey items and briefly examines the difference between explicit and implicit double-barreled items.
Influence of sea polymer removal on sound absorption behavior of islands-in-the-sea spunbonded nonwovens
Authors: Suvari Fatih , Ulcay Yusuf , Pourdeyhimi Behnam
Published: September 2018

This work presents the results of efforts focused on the development of relatively lightweight and fibrous acoustic webs. For this objective, nonwoven webs that contain bicomponent filaments with islands-in-the-sea cross sections were produced by spunbonding, which involves the extrusion of sea and island polymer melts through dies, cooling and attenuating the bicomponent filaments by high-velocity air streams. Nylon 6 and polyethylene were used as the island and sea polymers, respectively. Webs were hydroentangled with high-pressure water jets prior to the dissolving process to obtain fiber entanglement. Sea polymer was removed from the spunbonded nonwovens by using a reflux dissolution setup. Weight, thickness, air permeability, pore size and sound absorption coefficients of the nonwoven samples were measured before and after the sea polymer removal. Results demonstrated that sea polymer removal led to further bicomponent filament fibrillation, which affected sound absorption positively. The structure with the higher number of island fibers had better acoustical properties. Lightweight and fibrous acoustic nonwovens can be obtained with the method given in this study.
Detection of bending direction and amplitude by electrical resistance measurement of axial carbon fibers in braided composite tube
Authors: Cheng Xiaoying , Zhou Hongshui , Wu Zhenyu , Hu Xudong
Published: September 2018

In this paper, electrical resistance measurement (ERM) was used to detect the direction and amplitude of the bending force on fiber-reinforced polymer composite (FRPC) tubes. The method was based on research into the influence of position on the sensing behaviors of carbon fibers (CFs) as separated resistive elements under flexural tests. CFs were inserted into the fabric reinforcement fabricated by a circular braiding machine as axial tows that are separated by bias tows (Kevlar fibers) to serve as sensors. In experiments, samples of FRPC tubes with four axial tows were fabricated and bent at two different angles relative to the distribution of CFs while deformation was maintained in the elastic zone. The resistance change ratios of the CFs varies from −1.5% to 0.3% and the zero-crossing point on the tube is at 105°. The results showed that CF resistances would change in a particular pattern as the tube was being bent, and the bending direction and force amplitude could be derived from this pattern.
To Do or to Have, Now or Later, in Travel: Consumption Order Preference of Material and Experiential Travel Activities
Authors: Hwang Euejung , Kim Jungkeun , Lee Jacob C. , Kim Saetbyeol
Published: September 2018

The current research explores consumers’ preferred timing of consuming experiential and material purchases made during their travels and its downstream affective consequence. Previous research showed that people generally show relative preference toward consuming material purchases sooner than experiential purchases. Reversing this finding, we contend that travelers who are primed with the concept of an experience exhibit relative preference toward consuming experiential purchases sooner than material purchases. Further, we contend that travelers associate greater subjective happiness from the travel schedule with sooner experiential than material consumption. To provide convergent and robust evidence supporting our hypothesis, we conducted seven empirical studies, including a field study. Our work contributes to (1) researchers in the field of travel, psychology, and marketing; (2) travelers who want to optimize their travel; and (3) practitioners who want to understand travelers’ behavior and psychology.
Processing of Ceramic Foams from Polymeric Precursor-Alumina Suspensions
Authors: Nangrejo M.R. , Bao X. , Edirisinghe M.J.
Published: September 2018

A polysilane was used as the precursor for silicon carbide (SiC) and different amounts of it was dissolved in dichloromethane. Subsequently, between 10 to 80 %wt of alumina (Al2O3) powder was added into the solutions to make SiC-Al2O3 suspensions. Cubes of polyurethane (PU) foams with open cells in the size range 500-1200μm were soaked in these suspensions and pyrolysed in flowing nitrogen to produce SiC-Al2O3 composite foams. Some foams were heated further in nitrogen to 1300°C. The foams produced consist of an open cell structure and hole-free solid struts which were also cracks free in the polysilane-Al2O3 80:2Owt% formulation. The retention of shape during processing was excellent. Shrinkage observed after pyrolysis and further heating the foams was measured and can be controlled by varying the Al2O3 content. The foams produced have porosities in the range 87 to 95%. The maximum compressive strength of the pyrolysed foams prepared using the polysilane-Al2O3 80:20 wt% formulation was 2.3MPa.
Transport of 1,1,1,3,3-Pentafluorobutane (HFC-365mfc) in Rigid Polyurethane Foam and Polyethylene
Authors: Mangs Sara , Fröling Morgan , Ramnäs Olle , Jarfelt Ulf
Published: September 2018

This study focuses on the mass transfer properties of 1,1,1,3,3-pentafluorobutane (HFC-365mfc) in the insulating system used in most district heating pipes produced today, namely rigid polyurethane (PUR) foam with a protective layer of polyethylene (HDPE). The solubility, permeability and diffusion coefficients for HFC-365mfc in PUR foam and HDPE have been determined. The coefficients for HFC-365mfc in PUR foam are very similar to those of cyclopentane, currently the most common blowing agent in PUR foams used for district heating pipes in Europe. The polyethylene casing is a better diffusion barrier for HFC-365mfc than it is for cyclopentane. However, the main mass transfer resistance of HFC-365mfc in a district heating pipe is found in the PUR foam.
Sorption, Diffusion, and Dilation in Linear and Branched Polycarbonate–CO2 Systems in Relation to Solid State Processing of Microcellular Foams
Authors: Handa Y. Paul , Zhang Zhiyi
Published: September 2018

The sorption and diffusion of CO2 in linear and branched polycarbonates were investigated using a high-temperature, high-pressure gravimetric technique. The branched structure does not affect gas solubility, but affects the gas diffusivity in the sub-Tg region, with CO2 diffusing faster through the branched structure than the linear one. Both solubility and diffusivity depend linearly on pressure at temperatures above Tg, but demonstrate complicated pressure dependence at temperatures below Tg. In the sub-Tg region, volume change of the polymer matrix accompanying the gas dissolution was measured using a dilatometer. The plasticized Tgs obtained from dilation and solubility measurements agreed with those obtained directly by high-pressure DSC. In addition, a plasticization related densification phenomenon was observed in the sub-Tg region. The competing effects of dilation and densification suggest significant implications in terms of solid state processing of microcellular foams.
Foam Extrusion of Polystyrene Blown with HFC-134a
Authors: Gendron Richard , Huneault Michel , Tatibouët Jacques , Vachon Caroline
Published: September 2018

There is much interest in developing industrial processes to manufacture extruded polystyrene foam that do not involve ozone depleting blowing agents. A popular alternate candidate is HFC-134a. It has a zero ozone depletion factor and is nearer in chemical structure to standard blowing agents (CFC-22 and HCFC-142b) than carbon dioxide. Although exhibiting main good features, HFC-134a is not used widely as a blowing agent as low foam density is not readily achieved and extruder operation is difficult. A review of past and on-going works on the use of HFC-134 will be addressed first. Then attention will be paid mainly on some processing aspects, with emphasis on the plasticization behavior of polystyrene (PS) by HFC-134a and the effect of screw design on dynamic dissolution of HFC-134a in PS during foam extrusion. Solubility efficiency during extrusion processing has been assessed for different screw configurations by an in-line ultrasonic technique. These results have also been correlated to off-line solubility and diffusivity properties.
Modeling Diffusion-Induced Bubble Growth in Polymer Liquids
Authors: Venerus David C.
Published: September 2018

Accurate modeling of diffusion-induced bubble growth is essential for the development of efficient polymer foaming processes. Consequently, a large number of transport models of this complex phenomena have been formulated. In most previous studies, one or more simplifying approximations have been invoked to reduce mathematical complexity. In this paper, we present and compare several models of bubble growth in liquids and examine the effects blowing agent concentration, liquid viscosity and elasticity on bubble growth dynamics. In addition, we compare predicted and measured bubble growth behavior in two polymer foaming systems.
Effect of Key Process Variables on Microstructure of Injection Molded Microcellular Polystyrene Foams
Authors: Kawashima Hidetaka , Shimbo Minoru
Published: September 2018

The effect of control factors as key process variables on injection molds of microcellular plastics were investigated experimentally in this paper. The continuous foam processing system was constructed using screw preplasticating type injection mold machine, which is capable of supplying blowing agent, plasticity, kneading and keeping of retention time for gas/polymer solution. The propriety of foam processing system constructed in this study was verified. Control factors that affect cell nucleation and growth by injection molding were classified and some of them were considered in this study. In order to investigate cell morphology and cell structure, microcellular polystyrene samples were produced under various ranges in control factors by using the above processing system. In particular, the effect of injection velocity, mold temperature, retention time, plunger stroke and dwelling pressure on cell morphology of microcellular polystyrene were examined and discussed. It was found that cell size decreases and cell density increases with an increase in injection velocity. Cell size decreases about linearly with an increase in injection velocity and becomes about half size for five times of velocity. An increase rate of cell density is about ten times to five times of injection velocity.
The Second Expansion Cycle in Ultramicrocellular Foams
Authors: Nawaby A. Victoria , Handa Y. Paul
Published: September 2018

Ultramicrocellular PMMA foams made from the low temperature rubbery phase, obtained by saturating the polymer with CO2 at 0°C and 34 atm, was subjected to a second expansion cycle by heating it rapidly to temperatures in the range 30 to 120°C. The blowing agent for the secondary expansion was either the residual CO2 in the foam at about 19 wt% level or fresh CO2 re-equilibrated at 0°C and 34 atm to a loading level of about 29 wt%. In the former case, the second expansion cycle led to lower foam densities whereas in the latter case it led to stretching and re-orientation of the cell walls with no significant gain in further foam density reduction or cell density increase.
Evaluation of HFC-245fa as an Alternative Blowing Agent for Extruded Polystyrene
Authors: Vachon Caroline , Gendron Richard
Published: September 2018

The need for replacing conventional CFCs with alternative blowing agents has led to the development of many candidates. Among those, HFC-245fa is targeted as one of the most promising for the replacement of HCFC-141b in polyurethane foams. However, the low thermal conductivity of HFC-245fa and its interesting near room-temperature boiling point may render it suitable for other applications such as polystyrene insulating foam board manufacturing.

This work investigates the use of HFC-245fa as a potential physical blowing agent for extruded thermoplastic foams. The process was monitored using ultrasonic probes, which reveals information on the solubility behavior of the gas in the molten state. Results showed that at 190°C, HFC-245fa could be incorporated in molten polystyrene up to about 7 wt.% and generate homogeneous solutions. Higher concentrations revealed evidence of heterogeneous conditions as seen in the attenuation signal. Three concentrations of blowing agent (5, 6 and 7 wt.%) were used to produce foam samples at lower extrusion temperatures. Increasing the concentration of blowing agent or nucleating agent greatly affected the expansion profile of the foam samples. Thus, lower densities could be achieved by using an optimal combination of both.
Foaming Cyclo-Olefin Copolymers with Carbon Dioxide
Authors: Gendron Richard , Champagne Michel F. , Tatibouët Jacques , Bureau Martin N.
Published: September 2018

Cyclo-olefin copolymers (COC) based on ethylene-norbornene (E-NB) structures have been investigated with respect to their foamability. COC present interesting characteristics, such as extremely low water absorption, excellent water vapor barrier properties, high strength and very good electrical insulating properties. Varying the ratio of E versus NB monomers enables to tune the glass transition temperature (Tg) over a wide range. Due to the rigid ring structure of NB, the resin remains amorphous.

This study presents basic information related to the foam processing of different grades of COC resins with Tg varying between 80 and 130 °C, adding a special emphasis on process-relevant material characteristics: rheology, solubility and plasticization. CO2-laden COC sheets, where the gas sorption was obtained using high pressure autoclave, were foamed using a biaxial stretcher. The impact of selected processing parameters (temperature, time of pre-heating, speed of deformation, magnitude of stretching) on the microcellular foam morphology and density will be reported throughout this paper.
Fabrication of Microcellular HDPE Foams in a Sub-Critical CO2 Process
Authors: Miller Dustin , Kumar Vipin
Published: September 2018

In this paper processing conditions are presented to fabricate HDPE foams with a microcellular structure. The conventional microcellular foams are normally produced by heating a gas-saturated thermoplastic to a foaming temperature near the glass transition of the gas-polymer system. Efforts to foam HDPE in the conventional process have largely been unsuccessful, due to the low glass transition temperatures and low gas solubility in these polymers. We have found that HDPE can be successfully foamed with a microcellular structure at foaming temperatures above the melting point. Density reductions of up to 65% were obtained using sub-critical carbon dioxide as blowing agent. A unique bimodal structure was observed, consisting of closed microcells with an interconnected nanoporous interior.
Mechanical, Morphological and Thermal Properties of Rigid Polyurethane Foam: Effect of Chain Extender, Polyol and Blowing Agent
Authors: Thirumal M. , Khastgir Dipak , Singha Nikhil K. , Manjunath B.S. , Naik Y.P.
Published: September 2018

The properties of rigid polyurethane foams can be modified over a wide range depending on the raw materials used for its synthesis. The polyols, chain extender and blowing agent have major impact on the properties of the PUF. This investigation reports the effect of polyol and its blends, chain extender such as 1, 4-butanediol (1, 4-BD) and blowing agents [chemical as well as physical; such as distilled water and n-pentane (n-C5), hydrochlorofluorocarbon (HCFC)] on the properties of rigid PUF. Addition of the chain extender improves the mechanical properties initially but then it decreases the properties on further addition of the same. The thermal conductivity of the chain extended and that of the physically blown PUF was lower than the water blown PUF. Higher loading of chain extender and blended polyol decreased the glass transition temperature (Tg) of the PUF due to the decrease in cross-link density because of low –OH functionality in the presence of linear diols like hydroxyl terminated polybutadiene (HTPB). It was observed that there is no significant change in degradation temperature of the chain extended, physically blown and blended system except that observed in the case of HTPB filled PUF.
Visualization Study of Solid Poly (Ester-Amine Salt) Precursor Foaming Process
Authors: Zhang Y.Z. , Zhang G.C. , He Z. , Sun X.F. , Rajaratnam M.
Published: September 2018

In this research, solid poly (ester-amine salt) precursor was used to prepare polyimide foams. The foaming process was observed by microscope, and effects of particle size on bubble growth were highlighted. The results showed that the powder particles with a size between 25 and 150 μm favor to grow into single bubble mesostructure, and the ones which grow into a multi-bubble mesostructure beyond this size. On the contrary, the bubble growth terminated when the particle size below 25 μm. Sieving was an effective method to narrow size distribution and uniform the particle size, which is of benefit to the formation of polyimide foams. After filtrated with 100 mesh sieve, the retreated particles were situated in optimal band to produce polyimide foams with single bubble mesostructure.
Effect of Weld Lines on Injection Moulded Fibreglass Reinforced Structural Foams. 2 - Impact and Flexural Properties
Authors: Bégin Mathieu , Rodrigue Denis
Published: September 2018

In the second part of this investigation, the effects of weld lines on impact strength and flexural properties of injection moulded glass fibre reinforced structural polypropylene foams are reported. The results show that Charpy impact strength decreases with density and presence of a weld line. For three-point bending tests, a linear decrease of the flexural modulus and flexural strength as density decreases was found, the latter being more important. There is also a significant decrease of flexural properties for samples with a weld line compared to samples without one of the same density. Also, to evaluate the weakness of the weld line region, off-centre flexural tests were performed to determine the minimum distance at which load should be applied for the failure to no longer occur at the weld line. The results obtained indicate that this distance decreases as density decreases.
The Supercritical State Paradigm in Thermoplastic Foaming
Authors: Gendron Richard , Champagne Michel F. , Li Hongbo , Tatibouët Jacques
Published: September 2018

“Supercritical” has become automatically and intrinsically associated with “carbon dioxide foaming”, with this combination generally resulting into claimed benefits such as microcellular structure, high cell density and enhanced mechanical properties.

However the supercritical state remains accessible to any blowing agents. The newly-introduced hydrofluorocarbons (HFCs), following the ban put on chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) in the polystyrene foam industry, are other examples of foaming agents that are processed under temperature and pressure conditions that belong to the supercritical region. Unfortunately, such unusual conditions have resulted in the past into typical processing difficulties that make the resulting benefits associated to the supercritical state questionable. The supercritical state may not be apparently the panacea usually claimed… and sought for!

In this work, density characteristics of supercritical fluids were reviewed and linked to the foam nucleation stage. Foaming experiments using a specific polymercarbon dioxide system were conducted at the vicinity of the critical locus and the sequence leading to phase separation monitored using an ultrasonic technique. The results suggested a phase separation mechanism similar to that of spinodal decomposition. Density fluctuations reported for supercritical fluids close to their critical locus would translate for the foaming process into concentration fluctuations typical of the spinodal decomposition.
Long-term Aging of Closed-Celled Foam Insulation
Authors: Murphy John
Published: September 2018

Many factors influence the thermal efficiency [lambda value or k-factor] one obtains with foams blown with any of the commercial physical blowing agents. Factors affecting a product's thermal efficiency depend on, but are not limited to, the blowing agent itself – such items as the blowing agent's molecular weight, its boiling point, and its solubility in the foam matrix. Other factors depend on formulation parameters such as catalyst levels which affect speed of reaction and fineness of cell structure. Still others depend on the mixing efficiency of the equipment used to process the foams. Finally, a great deal of the contribution depends on the amount of protection the foam receives from its immediate environment - ranging from exposed foam to foam enclosed within impermeable facers.

The long-term aging of foams has always been filled with myth and controversy. This has been true for every blowing agent that has been commercialized. We will try to dispel some of the myths with the results of several long-term aging studies, run on ecomate® and other commercial Blowing Agents.
Reactive Nanocomposite Foams
Authors: Verdejo Raquel , Bernal M. Mar , Romasanta Laura J. , Tapiador Francisco J. , Lopez-Manchado Miguel A.
Published: September 2018

One of the most interesting and most accessible opportunities of nanofillers is the reinforcement of fine structures in which conventional fillers cannot be readily accommodated, such as polymer foams. This paper reviews the progress to date towards the development of reactive foam nanocomposites, in particular polyurethane and silicone foams. The discussed systems are summarized based on the types of nanofillers used, i.e. nanoparticles, rod-like, and plate-like systems. The effect of nanofillers on the foaming process, cellular structure and properties is critically reported along with a summary of the measured improvements in the mechanical, electrical and thermal properties of the resulting nanocomposites.
Density Graded Linear Medium Density Polyethylene Foams Produced under a Temperature Gradient with Expancel Microbeads
Authors: Yao Jiaolian , Barzegari Mohamad Reza , Rodrigue Denis
Published: September 2018

In this work, density graded foams were produced using linear medium density polyethylene as the matrix and different grades of Expancel microbeads. Local density inside the foams was controlled by setting independently the top and bottom plates of a compression mould at different temperatures and by controlling moulding time. Due to the temperature gradient, complex density profiles were produced and a complete morphological analysis was performed to extract average cell diameter and cell density across foam thickness. Finally, the tensile and flexural moduli are reported and discussed in relation with foam structure.
Uniaxial Compressive Cyclic Loading Process of a Kind of Bumper Foams
Authors: Chen Wei , Lu Zixing , Pan Bing , Guo Junhong , Li Yanjie
Published: September 2018

In this paper, the experimental and theoretical studies on the uniaxial compressive cyclic loading process of a kind of bumper foams are presented. The uniaxial cyclic loading tests are conducted to investigate the influence of the geometrical dimension and the displacement rate on the mechanical behavior of specimen. The influences of preloading process are analyzed experimentally and the residual strains are then discussed. At the same time, a modified pseudo-elastic model considering the residual strain is given to describe the unloading behavior and realized with the finite element method. The numerical results demonstrate that the present model is suitable to describe the unloading behavior of a kind of bumper foam. The limitations of this model are finally discussed.
Synthesis and Characterization of Polyurethane Nanocomposites Formulated by Incorporation of Polyols from PET Waste
Authors: Nikje Mohammad Alavi , Farazfar Mohaddeseh
Published: September 2018

Polyethylene terephthalate (PET) was depolymerized using trimethylolpropane (TMP) and glycerin as a binary solvent mixture to provide oligomeric polyol for rigid polyurethanes foam formulation. Recyclate containing rigid polyurethane foam nanocomposites were prepared by introducing of different portions (1-5%) of nanoclays namely, NaMMT, 30B, 20A, 15A Cloisites. The parallel effects of recycled polyol and nano clays on mechanical and thermal characteristics of the nanocomposites were investigated. Dispersion of clay nano particles in polymer matrix was characterized by SEM what confirm the exfoliation of nanoparticles. The thermal properties were also studied by TMA and DMA.
Density Graded Polyethylene Foams Produced by Compression Moulding Using a Chemical Blowing Agent
Authors: Yao Jiaolian , Rodrigue Denis
Published: September 2018

Density graded polyethylene foams were produced using a chemical blowing agent and compression moulding. To control the local density inside the foams, the top and bottom plates of a compression moulding set-up were placed at different temperatures and moulding times in order to produce symmetric and asymmetric structural foams. Due to different temperature gradients produced inside the samples, complex density profiles were created. From the samples obtained, a complete morphological analysis was performed to extract cell size and cell density across foam thickness in relation with density profiles. Also, to determine the effect of density profile on the mechanical properties, tensile and flexural characterizations were performed. The results obtained are discussed in relation with optimum properties vs. bulk foam density.
Mechanical Properties of Density Graded Foams: Tensile Properties
Authors: Barzegari Mohamad Reza , Yao Jiaolian , Rodrigue Denis
Published: September 2018

This work presents the production and characterization of functionally graded polymer foams produced by compression molding. For the conditions tested (temperature gradient, molding time, type and concentration of Expancel microbeads), it was possible to reach density reduction between 2 and 45% for symmetric and asymmetric polyethylene foams. Tensile properties (modulus and stress at 1% deformation) were then measured to relate with their respective density profiles. From the experimental data obtained, a simple finite element analysis was performed to determine the tensile properties of asymmetric foams. The results show that excellent predictions were obtained with a maximum deviation of 7% for all the conditions tested.
Improvement in Compressive Behavior of Alkali-treated Wood Fibre-reinforced Bio-based Polyurethane Foams
Authors: Chang Li-Chi , Sain Mohini , Kortschot Mark
Published: September 2018

Alkali-treated wood fibre-reinforced polyurethane (PU) foams were fabricated with a free-rising foaming process. The surface chemistry of alkali-treated wood fibres was characterized using in situ Fourier transform infrared spectroscopy (FTIR), and the fibre surface morphology was explored using scanning electron microscopy (SEM). X-ray computed tomography (CT) was performed to observe the cell structure of foams incorporating the treated wood fibres. Compression tests were conducted and the influence of treated fibres on the compressive strength and modulus of PU foam was investigated. The foams reinforced with treated fibres exhibited increase of 40% in strength and 64% in modulus. The high surface roughness and high aspect ratio of the treated fibres contributed to these improved mechanical properties through enhanced interfacial bond strengths.
Effectiveness of Blowing Agents in the Cellular Injection Molding Process
Authors: Garbacz Tomasz , Palutkiewicz Pawel
Published: September 2018

The study was undertaken to investigate the effect of the type and content of blowing agents in the polymeric materials being processed on the structure and selected physical and mechanical properties of the obtained injection molded parts. In the study of the cellular injection molding process, three standard and generally available thermoplastics were used. In the experiments, the blowing agent content (0–2.0% by mass, i.e. 0, 0.4, 0.8 and 2.0% (wt)) fed into the polymer being processed was adopted as a variable factor. In the present study, the blowing agents with the endothermic decomposition characteristics and exothermic decomposition characteristics, coming in a granulated form with a diameter ranging from 1.2 to 3 mm were used.

Based on the results of investigating porosity, porous structure image analysis as well as microscopic examination of the structure was shown. It has been found, that the favorable content of the blowing agent in the polymeric material should be of up to 0.8% wt.. With such content of the blowing agent in the polymeric material, favorable strength properties are retained in porous parts, the pore distribution is uniform and the pores have similar sizes.
Effect of Biaxial Stretching Temperature and Gas Diffusion Expansion on Cellular Morphology of PP/CaCO3and PP/talc Cellular Films
Authors: Audet Eric , Mighri Frej , Rodrigue Denis , Ajji Abdellah
Published: September 2018

To evaluate the impact of the stretching temperature on the morphology of cellular polypropylene (PP) films, a series of PP films filled with spherical particles of calcium carbonate (CaCO3) and platy talc particles with weight concentrations varying from 15 to 35 wt% were prepared by twin-screw extrusion then biaxially stretched at three temperatures (152, 155 and 158°C). Their corresponding cellular morphology was analyzed from scanning electron microscopy (SEM) micrographs. It was shown that film stretching at the lower temperature (152°C) led to delamination of PP/CaCO3or PP/talc interface, while it was not the case when these films were stretched at 158°C. It was also observed that, when films were stretched at 152°C, their corresponding developed cells had an average cell wall thickness t of around 3.6 μm, an average cell height b of around 13.6 μm, and an average cell aspect ratio a/b of around 5.6, where a (mm) is the average cell width. These values were within the aimed cell geometrical specifications needed for cellular piezoelectric films.
Current Issues and Challenges in Polypropylene Foaming: A Review
Authors: Mohebbi Abolfazl , Mighri Frej , Ajji Abdellah , Rodrigue Denis
Published: September 2018

Thermoplastic foams have several advantages in comparison with unfoamed polymers such as lightweight, high strength to weight ratio, excellent insulation property, high thermal stability, high impact strength and toughness, as well as high fatigue life. These outstanding properties lead cellular plastics to various industrial applications in packaging, automotive parts, absorbents, and sporting equipment. Nowadays, polypropylene (PP), because of its outstanding characteristics such as low material cost, high service temperature, high melting point, high tensile modulus, low density, and excellent chemical resistance, is a major resin in the foaming industry. However, foaming of conventional PP is limited by its low melt strength leading to poor cell morphology, cell rupture/coalescence and limited density reduction. To improve PP melt strength, several strategies including particle addition as nucleating agent, introduction of long chain branching, blending with high melt strength polymers and crosslinking have been proposed. In this review, these issues are discussed and analyzed in terms of mechanical, thermal, and rheological characterizations.
Malachite Green Adsorption Behavior of Polyurethane/Chitosan Composite Foam
Authors: Li X.X. , Li J. , Cai L.Y. , Li T.T. , Liu X.F. , Li J.R.
Published: September 2018

A composite foam of polyurethane/chitosan with chitosan content of 20 wt% was successfully prepared as an adsorbent for the removal of malachite green from aqueous solution, the structures and properties were characterized by scanning electron microscope and Fourier transform infrared spectroscopy. The results showed open cell content of polyurethane/chitosan was more than 95% and open cell structure was intuitive shown by scanning electron microscope images. It was revealed that polyurethane/chitosan exhibiting high efficiency on malachite green adsorption. Fourier transform infrared spectroscopy study showed that possible pathway for malachite green adsorption may include hydrogen bond and acetyl groups. The adsorption isotherms, kinetics and thermodynamics of polyurethane/chitosan for malachite green were studied in detail, and adsorption process followed Langmuir isotherms model rather than pseudo-second-order kinetic model. The activation energy value indicated that the adsorption was mainly physical process.
Numerical Selection of the Parameters in Producing Microcellular Polymethyl Methacrylate with Supercritical CO2
Authors: Li Ruosong , Li Lu , Zeng Dan , Liu Qinli , Fang Tao
Published: September 2018

A systematized calculation of foaming parameters in producing microcellular polymethyl methacrylate (PMMA) with supercritical carbon dioxide (SCCO2) was proposed. The calculated optimal results were saturation temperature = 313 K, pressure = 25 MPa and time = 15 h, which were achieved by the Chow model, classical nucleation theory and Fick diffusion law, respectively. Additionally, the Center-Composite Design (CCD) statistical approach in Response Surface Method (RSM) was employed to evaluate the validity of the calculated parameters. The error between the optimal parameters predicted by CCD statistical approach and the calculated ones was acceptable, demonstrating the accuracy of the calculated parameters.
Amelioration of Waves and Micro-vibrations by Micro-buckling in Open Celled Foam
Authors: Balch Samuel P. , Lakes Roderic S.
Published: September 2018

Open cell polymer foam exhibits both an intrinsic micro-vibration frequency and a cut off frequency associated with resonance of the cell ribs. Compression of the foam causes regions of local buckling of ribs. Incipient buckling gives rise to negative stiffness and enhanced amelioration of waves. Transmitted wave amplitude is reduced by compression below and near the cut off frequency.
Effect of Processing Conditions on the Cellular Morphology of Polypropylene Foamed Films for Piezoelectric Applications
Authors: Mohebbi Abolfazl , Mighri Frej , Ajji Abdellah , Rodrigue Denis
Published: September 2018

In this work, continuous extrusion-calendering was used to produce polypropylene (PP) foam films for piezoelectric applications. The setup is based on physical foaming using supercritical nitrogen (SC-N2) and calcium carbonate (CaCO3) as nucleating agent. In particular, the extrusion parameters (screw design, temperature profile, blowing agent and nucleating agent content) and post-extrusion conditions (calendaring temperature and speed) were optimized to achieve a specific stretched eye-like cellular structure with uniform cell size distribution. The morphology in both machine and transverse directions, as well as tensile properties were characterized. The results show that a cellular structure with a higher cell aspect ratio has a lower Young's modulus, which is appropriate for piezoelectric cellular films. Generally, the developed foam morphology presents high potential for the production of ferroelectret PP films used in different piezoelectric applications.
Generalization and Modelling of Rigid Polyisocyanurate Foam Reaction Kinetics, Structural Units Effect, and Cell Configuration Mechanism
Authors: Xu Jie , Wu Tao , Sun Wei , Peng Chuang
Published: September 2018

PIR/PUR ratio was derived from differential manipulation of generalized polyisocyanurate kinetic model. The structural unit effects on polymerization of isocyanurate, urethane and urea linkages were evaluated based on Mayo-Lewise tercopolymerization scheme. The cell microstructural configuration model was further developed from profiled FOAMAT reactivity parameters with integrated analysis of cell interface physics. The interstitial border area was defined by interface free energy theory, the shear viscosity was evaluated by foam motion, gas fraction, and partial pressure, and the cell inflation was re-examined by gas-liquid surface tension variability. The cell anisotropic degree, assumed as an aspect ratio of infinitesimal volume elements in cell uniformity, was characterized by equilibrated work increase of surface energy approximated by 2D stretching deformation from sphere cell to spheroid cell. The relationship between pressure and surface tension of elongated cells was also derived from modelling at the same condition of cell deformation.
The Effect of Compatibilization on the Properties and Foaming Behavior of Poly(ethylene terephthalate)/Poly(ethylene-octene) Blends
Authors: Wang Wenbo , Yu Kesong , Zhou Hongfu , Wang Xiangdong , Mi Jianguo
Published: September 2018

The methodology for improving the properties and foaming behavior of poly (ethylene terephthalate) (PET)/poly(ethylene-octene) (POE) blends through compatibilization was proposed. In this paper, PET/POE blends were prepared through a melt blending method, POE was employed as elastomer toughener, maleic anhydride grafted POE (mPOE) was selected as compatibilizer, and pyromellitic dianhydride (PMDA) was used as chain extender. The content of mPOE was changeable to study the effect of compatibility on crystallization behavior, toughness, dispersion morphology, and rheological behavior of PET/ POE blends. The results demonstrated that the crystallization peak of PET/POE blends shifted towards high temperatures from 196.97°C to 201.24°C with the content of mPOE increasing. The brittle-ductile transition for PET/POE blends occurred at the mPOE content in the range of 4–5 phr. The particle size of POE dispersed phase decline firstly and then was almost unchanged with an increasing content of mPOE. The storage modulus and complex viscosity of compatibilized PET/POE blends were obviously higher than that of uncompatibilized PET/POE blends. Then PET/POE blends were foamed using supercritical CO2 as physical blowing agent. The results showed that the cell size, cell density, and tensile properties of the PET/POE blending foams were affected by the content of mPOE strongly. With the content of mPOE, the cell size decreased and then kept stable as well as the cell density the trend of cell size increased then remained unchanged. In addition, the elongation at break of PET/POE blending foams was higher than that of the uncompatibilized PET/POE blending foam. PET/POE blending foams with fine cell morphology and good ductility could be achieved with a proper content of compatibilizer in the blends.
Multiple daytime administration of the selective orexin-2 receptor antagonist JNJ-42847922 induces somnolence in healthy subjects without residual central effects
Authors: van der Ark Peter D , Golor Georg , van Nueten Luc , Nandy Partha , de Boer Peter
Published: September 2018

Background:

Pharmacokinetics, pharmacodynamics and general safety and tolerability of JNJ-42847922, a selective orexin-2 receptor antagonist, were assessed in healthy subjects.

Methods:

Five consecutive cohorts of healthy subjects were enrolled and received doses of 5–60 mg orally once daily over 10 days of JNJ-42847922 ( n=6) or placebo ( n=2). Concentrations of drug in plasma and urine were measured over 24 h after dosing on Days 1, 5 and 10. Observed- and self-reported somnolence was used to evaluate the principal pharmacodynamic effect of JNJ-42847922. A test battery to assess vigilance state, sedation and alertness was assessed at 4, 6 and 8 h after dosing. Safety assessments included recording of adverse events, vital signs, electrocardiograms, clinical laboratory assessments and suicidality per Columbia Suicide Severity Rating Scale.

Results:

JNJ-42847922 was rapidly absorbed after the morning dose administration. The median tmax ranged from 0.5–1.5 h and mean t1/2 values from 2–3 h. At JNJ-42847922 dose levels ⩾20 mg, mean Cmax and mean area under the curve, values increased less than dose proportionally. At doses ⩾20 mg, JNJ-42847922 consistently induced somnolence on all study days. At four hours post-dose administration, dose levels >5 mg JNJ-42847922 were identified as sedating by the Addiction Research Center Inventory-49. Except for a mild decrease in attention (Bond and Lader Visual Analogue Scale Factor 1) at dose levels >10 mg at four hours post-dose, no clinically relevant changes in other central measures have been observed. JNJ-42847922 was well tolerated.