Physical Blowing Research Articles

A Method of Simulating the Dissolution Behavior of Physical Blowing Agents. Dissolution Behavior of Physical Blowing Agent in Low-pressure Foam Injection Molding Process (Part 2)

A Method of Simulating the Dissolution Behavior of Physical Blowing Agents. Dissolution Behavior of Physical Blowing Agent in Low-pressure Foam Injection Molding Process (Part 2)

Overcoming Challenges of Education: Effects of Structural Violence and Advances in Quality Education in Colombia and Pakistan

Far from solely direct, structural violence moves stealthily within the very frameworks of society, injuring in ways not seen. Its harms manifest not in physical blows but through the architecture of injustice, through inequities etched into policies, laws, norms. Having this in mind, the main goal of this paper is to present how structural violence takes place in the sustainable development goal of Quality Education (SDG4) in Colombia and Pakistan. To make it possible, structural violence will be defined, as well as the sustainable development goals, and in particular its goal 4 about quality of education. Likewise, it will be analyzed how SDG-4 correlates with other sustainable development goals. This study adopts a cyclical and exploratory approach to theory development as its scaffolding, specifically Grounded Theory methodology. data collection and analysis techniques follow the mixed method with a transformative theoretical design prioritizing qualitative interviews findings. Results highlight the current status of SDG 4 in Colombia and Pakistan, illuminating how ingrained systemic biases and discrimination undermine equitable quality education. Experts outline interlinked recommendations such as sustained investment in education systems, building societal recognition of education as a human right, engaging communities to shift discriminatory beliefs and norms, and centering marginalized groups' agency in political and social reform efforts. A multifaceted approach combining top-down resource provision and bottom-up consciousness-raising is advocated among other recommendations. Overcoming structural violence requires transforming systemic structures while simultaneously shifting societal mindsets perpetuating discrimination in education.

Overcoming Challenges of Education: Effects of Structural Violence and Advances in Quality Education in Colombia and Pakistan

Far from solely direct, structural violence moves stealthily within the very frameworks of society, injuring in ways not seen. Its harms manifest not in physical blows but through the architecture of injustice, through inequities etched into policies, laws, norms. Having this in mind, the main goal of this paper is to present how structural violence takes place in the sustainable development goal of Quality Education (SDG4) in Colombia and Pakistan. To make it possible, structural violence will be defined, as well as the sustainable development goals, and in particular its goal 4 about quality of education. Likewise, it will be analyzed how SDG-4 correlates with other sustainable development goals. This study adopts a cyclical and exploratory approach to theory development as its scaffolding, specifically Grounded Theory methodology. data collection and analysis techniques follow the mixed method with a transformative theoretical design prioritizing qualitative interviews findings. Results highlight the current status of SDG 4 in Colombia and Pakistan, illuminating how ingrained systemic biases and discrimination undermine equitable quality education. Experts outline interlinked recommendations such as sustained investment in education systems, building societal recognition of education as a human right, engaging communities to shift discriminatory beliefs and norms, and centering marginalized groups' agency in political and social reform efforts. A multifaceted approach combining top-down resource provision and bottom-up consciousness-raising is advocated among other recommendations. Overcoming structural violence requires transforming systemic structures while simultaneously shifting societal mindsets perpetuating discrimination in education.

Dissolution Mechanism of Physical Blowing Agent into the Polymer in Low-pressure Physical Foam Injection Molding Process (Part 1) Effect of Molding Conditions on Physical Blowing Agent Concentration

Dissolution Mechanism of Physical Blowing Agent into the Polymer in Low-pressure Physical Foam Injection Molding Process (Part 1) Effect of Molding Conditions on Physical Blowing Agent Concentration

Behavior Characteristics and Thermal Energy Absorption Mechanism of Physical Blowing Agents in Polyurethane Foaming Process.

Polyurethane rigid foam is a widely used insulation material, and the behavior characteristics and heat absorption performance of the blowing agent used in the foaming process are key factors that affect the molding performance of this material. In this work, the behavior characteristics and heat absorption of the polyurethane physical blowing agent in the foaming process were studied; this is something which has not been comprehensively studied before. This study investigated the behavior characteristics of polyurethane physical blowing agents in the same formulation system, including the efficiency, dissolution, and loss rates of the physical blowing agents during the polyurethane foaming process. The research findings indicate that both the physical blowing agent mass efficiency rate and mass dissolution rate are influenced by the vaporization and condensation process of physical blowing agent. For the same type of physical blowing agent, the amount of heat absorbed per unit mass decreases gradually as the quantity of physical blowing agent increases. The relationship between the two shows a pattern of initial rapid decrease followed by a slower decrease. Under the same physical blowing agent content, the higher the heat absorbed per unit mass of physical blowing agent, the lower the internal temperature of the foam when the foam stops expanding. The heat absorbed per unit mass of the physical blowing agents is a key factor affecting the internal temperature of the foam when it stops expanding. From the perspective of heat control of the polyurethane reaction system, the effects of physical blowing agents on the foam quality were ranked in order from good to poor as follows: HFC-245fa, HFC-365mfc, HFCO-1233zd(E), HFO-1336mzzZ, and HCFC-141b.

Changes and Trends-Efficiency of Physical Blowing Agents in Polyurethane Foam Materials.

This work developed a novel method for measuring the effective rate of a PBA (physical blowing agent) and solved the problem that the effective rate of a PBA could not be directly measured or calculated in previous studies. The results show that the effectiveness of different PBAs under the same experimental conditions varied widely, from approximately 50% to almost 90%. In this study, the overall average effective rates of the PBAs HFC-245fa, HFO-1336mzzZ, HFC-365mfc, HFCO-1233zd(E), and HCFC-141b are in descending order. In all experimental groups, the relationship between the effective rate of the PBA, rePBA, and the initial mass ratio of the PBA to other blending materials in the polyurethane rigid foam, w, demonstrated a trend of first decreasing and then gradually stabilizing or slightly increasing. This trend is caused by the interaction of PBA molecules among themselves and with other component molecules in the foamed material and the temperature of the foaming system. In general, the influence of system temperature dominated when w was less than 9.05 wt%, and the interaction of PBA molecules among themselves and with other component molecules in the foamed material dominated when w was greater than 9.05 wt%. The effective rate of the PBA is also related to the states of gasification and condensation when they reach equilibrium. The properties of the PBA itself determine the overall efficiency, while the balance between the gasification and condensation processes of the PBA further leads to a regular change in efficiency with respect to w around the overall average level.

In-Line Monitoring of the Physical Blowing Agent Concentration by Transmission Near-Infrared Spectroscopy with High-Pressure Resistance Fiber Optic Probes for Foam Injection Molding Processes

In-Line Monitoring of the Physical Blowing Agent Concentration by Transmission Near-Infrared Spectroscopy with High-Pressure Resistance Fiber Optic Probes for Foam Injection Molding Processes

Foamability of Cellulose Palmitate Using Various Physical Blowing Agents in the Extrusion Process

Polymer foams are widely used in several fields such as thermal insulation, acoustics, automotive, and packaging. The most widely used polymer foams are made of polyurethane, polystyrene, and polyethylene but environmental awareness is boosting interest towards alternative bio-based materials. In this study, the suitability of bio-based thermoplastic cellulose palmitate for extrusion foaming was studied. Isobutane, carbon dioxide (CO2), and nitrogen (N2) were tested as blowing agents in different concentrations. Each of them enabled cellulose palmitate foam formation. Isobutane foams exhibited the lowest density with the largest average cell size and nitrogen foams indicated most uniform cell morphology. The effect of die temperature on foamability was further studied with isobutane (3 wt%) as a blowing agent. Die temperature had a relatively low impact on foam density and the differences were mainly encountered with regard to surface quality and cell size distribution. This study demonstrates that cellulose palmitate can be foamed but to produce foams with greater quality, the material homogeneity needs to be improved and researched further.

Test Method for the Solubility Model of Physical Blowing Agent of Self-Expanding Polymer

This paper aims to present a solubility model of physical blowing agent (PBA) for a kind of commonly used self-expanding polymer on engineering. The self-expanding polymer contains Component A (isocyanate) and Component B (polyhydric alcohol, PBA, water, and catalyst). Component B grout of the polymer, which contains PBA, was heated to measure its temperature and volume variations. Based on the principle of mass conservation and Clapeyron equation, the solubility curve of PBA with respect to temperature was calculated. The solubility curve was then applied to simulate the foaming process. A two-component polymer grout foaming experiment was then carried out to verify the applicability of the measured solubility curve. The simulated changes of temperature and density with respect to time of polymer grout were analyzed and compared with experimental results. The error of both sets of curves is within 5%, which shows a good agreement among them and proves the feasibility of the solubility model. This study provides a relatively complete test and verification process for the solubility model of PBA, which lays a theoretical foundation for both the polymer grouting diffusion mechanism and engineering application.

Near-Infrared Spectroscopic Monitoring Technique of Physical Blowing Agent Concentration in Foam Injection Molding Processes

Near-Infrared Spectroscopic Monitoring Technique of Physical Blowing Agent Concentration in Foam Injection Molding Processes

A facile template-free strategy for synthesizing hydroxymethyl-poly(3,4-ethylenedioxythiophene) nanospheres

Hydroxymethyl-poly(3,4-ethylenedioxythiophene)(PEDOT-OH) nanospheres self-assembled using physical blowing method, which continually used a syringe, were successfully formed through aqueous solution polymerization under the oxidative initiators. The effect of blowing on the morphological properties of PEDOT-OH was precisely evaluated based on the different amount of initiator. The concentration of ammonium persulfate might be a driving force in the self-assembly process to create the PEDOT-OH nanospheres. The electrical and electrochemical properties of the resulting nanospheres were also characterized using four-point probe and cyclic voltammetry.

An unexpected result of playing football: Anal laceration

Severe anal region injuries are rarely seen in emergency departments, but these injuries may be associated with morbidity and mortality. This case report aims to present a patient whose anal region was injured in a sports accident. An 18-year-old male patient was admitted to the emergency room because of a knee blow to his anal region while playing football. In the anamnesis of the patient was determined pain and laceration in the anal region. The patient had no additional complaints. On physical examination of the patient; approximately 2-3 cm of laceration was observed around the patient’s anal region, extending from the anal mucosa at the 7 o’clock direction. The patient was operated by a general surgeon and discharged after 1 day of hospitalization at the general surgery service. It should not be forgotten that there may be anal region traumas during football matches, one of the common sports. People should be careful to protect themselves from physical blows that can occur when playing football.

Slapstick Violence and the Female Comedian in Early Cinema

Slapstick Violence and the Female Comedian in Early Cinema Tom Gunning (bio) specters of slapstick and silent film comediennes by maggie hennefeld A slap-stick was a theatrical prop introduced in the sixteenth century in commedia dell'arte; it consisted of two hinged wooden slats that produced a loud noise when slapped together. It accompanied pantomimes of violent slaps or punches with an exaggerated and artificial sound effect. Maggie Hennefeld, in her new book Specters of Slapstick and Silent Film Comediennes, describes it this way: "a wooden stick that creates a jarring, violent sound while delivering a disproportionately mild blow to the body" (177). This "disproportion" between the actual physical blow and its aural report defines the comic effect of the device; the sound of a violent blow without its full physical effect. It also reveals something profound about the genre of comedy it named, essential to Hennefeld's approach to the genre: violence can be rendered comic through exaggeration but not denied. The slapstick migrated from Italian pantomime to international physical comedy, including the beatings of Punch and Judy puppet shows and live rough-and-tumble physical comedy. Even after the wooden device vanished, the term became generic for forms of physically violent comedy, especially as it moved from vaudeville and the music hall to the cinema. "Slapstick" now serves as a synonym for the gag comedy of the silent era, especially Chaplin and Mack Sennett, extending ultimately to Laurel and Hardy and even the Three Stooges and cartoons such as those featuring the battles of Road Runner and Wyle E. Coyote. Hennefeld's book deals not only with genre but also with gender. The comediennes she resurrects in this book moved through this violent and comic terrain clearly marked as women performing slapstick. [End Page 197] Although slapstick violence is widely acknowledged as a component of silent film comedy, scholarly discussion of the genre has focused primarily on the sight gag. Maggie Hennefeld's furiously original book returns the spectacle of violence to the center of its discussion. I will stress this aspect of her book more than the topic signaled by the second phrase of her title, "Silent Film Comediennes." The issues of comic violence and female performers and characters are intimately related, and there is no question Hennefeld makes an important intervention in feminist film studies. But her revival of the issue of violence in slapstick comedy goes beyond the survey of silent film comediennes that one might expect from the book's title. Hennefeld's feminist analysis burrows into the nearly oxymoronic issue of comic violence. This is not to shortchange her investigation of the nearly forgotten corpus of silent film comediennes. The book includes a detailed and useful appendix that lists silent films featuring comediennes that the author viewed, films that deserve to be better known. Certainly any future study of women in silent film comedy will have to draw on Hennefeld's pioneering work. But to reduce this book to a survey of this body of work misses its point. In contrast to some historical works, existing and still to come, dedicated to recovering this aspect of female creativity in silent film, Hennefeld's work is more interpretive and theory driven, more devoted to feminist theory than to historiography. I recall a panel at the Society for Cinema and Media Studies, organized by Jennifer Bean some years ago, in which an important feminist scholar criticized the interest in early cinema as a distraction from the emphasis on feminist film theory that had had been so crucial to the early years of film studies. Hennefeld's thorough citing not only of women performers in early cinema but also of the contributions by women scholars to the study of early cinema makes clear how central this period of film history has actually been for feminist investigation. This book does more than this, probing the feminist stake not simply in early cinema but in the specific structures of slapstick comedy. However, there was a point to a feminist questioning of the historical turn in which the rediscovery of early cinema provided one of the pivot points. As valuable as the concentrated research into the women pioneers...

Foaming Behavior and Microcellular Morphologies of Incompatible SAN/CPE Blends with Supercritical Carbon Dioxide as a Physical Blowing Agent.

The foaming process and cellular morphologies of poly(styrene-co-acrylonitrile) (SAN)/chlorinated polyethylene (CPE) blends with supercritical carbon dioxide (scCO2) as a blowing agent were investigated in this study. As compared to pure SAN foam in the same batch, the foamed blends with various CPE elastomer content had smaller average pore size and larger cell density. This is probably related to the inhibition of bubble growth by elastomer, resulting in poor melt flowability and strong viscoelasticity, and the efficient bubble heterogeneous nucleation caused by numerous phase interfaces inside the incompletely compatible blend system. In addition, many tiny interconnected holes through the pore walls were formed to connect adjacent micropores in foamed blend samples. The formation mechanism of such interconnected pores is probably due to the fracture of stretched melt around the bubble from phase interfaces with weak interactions. These facts suggest an effective path to control pore size, cell density and even interconnected pores of blend foams depends on the compatibility of the blend system and difference in foamability of individual components in supercritical CO2.

Rapid and complete removal of guayule (Parthenium argentatum) leaves by cryodefoliation, and freeze and thaw induction of rubber particle coagulation

Production of natural rubber (NR), a vital natural resource for modern economies, currently is completely dependent upon tropical cultivation of the Para rubber tree (Hevea brasiliensis, Müll. Arg). One promising source of alternative rubber is guayule (Parthenium argentatum, Gray), which is currently being developed as an alternative source of NR. Guayule rubber accumulates as rubber particles in bark parenchyma and can be extracted in the form of latex by homogenizing the bark and then separating the latex from the non-latex components by centrifugation. Latex separation and purification processes are significantly hindered by fine solids from the co-homogenized leaves. Therefore, complete removal of leaves before homogenization is highly desired. However, guayule leaves do not naturally abscise and chemical defoliants cannot be utilized since these dehydrate the shrub and coagulate the latex, and physical leaf removal processes are tedious or inefficient. We demonstrate that liquid nitrogen can be used to embrittle the leaves without freezing the bark parenchyma, completely removing the leaves with a single physical blow, and then the defoliated branches can be homogenized with no loss of latex-containing bark and no leaf contamination. Under longer freezing times, rubber coagulation occurred in partially frozen tissue and during slow thawing. Furthermore, we demonstrate that the rubber coagulation, which occurs when guayule branches are frozen through and thawed before homogenization, can be avoided by rapid homogenization of the flash frozen branches in ambient temperature aqueous extraction buffer.

Computer Analysis of Polyolefins Produced with Injection Molding Process Using Physical Blowing Agents

The complexity of today's plastic parts as well as the costs, quality makes it necessary to recognize potential errors early, already in the development phase of parts and moulds. Therefore, computer analysis became requisite part of any preprocessing phases. Due to the continuous effort decrease product weight and price many new techniques were developed recently. One relatively new end very effective technique is production of light construction products with using foaming agents. The main aim of this paper is therefore focuses on verification of computer analysis of Microcellular injection moulding process using physical blowing agents for the most used group of polymers which are polyolefins.

Elaboration and Characterization of Advanced Biobased Polyurethane Foams Presenting Anisotropic Behavior

AbstractBiobased and open cell polyurethane (PU) foams are produced from a synthesized sorbitol‐based polyester polyol. Different formulations are developed with various blowing agent systems (chemical vs physical blowing). Synthetized foams are fully characterized and compared. The cell morphology is carefully investigated by tomography and scanning electron microscopy. The chemical nature of the primary compounds, foaming kinetics, density, thermal behavior, and conductivity are fully studied, with also the main transition materials temperatures. It is shown that blowing agents especially impact the foaming kinetics. In the case of chemically blowing foams, higher foaming rate and temperatures are obtained. The mechanical behavior is particularly analyzed using quasi‐static compression tests, according two main axes compared to the rise direction. A direct relationship is observed between the formulation, foam structure, foam morphology, and corresponding mechanical properties. Results clearly highlight unexpected properties of biobased PU foams with unveil anisotropic mechanical properties.

Microcellular Foam Injection Molding of Thermoplastics Using Green Physical Blowing Agent

The microcellular injection molding technology, commercially offered by Trexel Inc. and other manufacturers, is primarily a close cell foaming technique. This process is capable of offering light weight non-porous thermoplastics moldings. The foaming of thermoplastics with open cellular morphology has got various high end applications among others like tissue engineering and membrane separation. Some of the researchers were successful in synthesis of open cellular thermoplastics at laboratory scale via solid state batch process. The growing demand for microporous thermoplastics, especially the biodegradable plastics (e.g. Polylactic acid), motivated the researchers develop a specialized microcellular injection molding process for processing of open cell thermoplastics using physical blowing agents such as supercritical nitrogen or carbon dioxide gas. A brief of theoretical and conceptual treatment of microcellular injection molding is presented.

Physical Blowing Agent Residence Conditions Stimulated Morphological Transformations in Extrusion Foaming

In this study, influence of blowing agent residence conditions on foam attributes has been investigated in extrusion foaming process. The blowing agent injection location in the extrusion barrel was found to affect the residence time inside the barrel, which in turn significantly transformed the foam microstructure. The injection location providing higher gas residence time resulted in foams with lower cell size, higher expansion ratio, and enhanced cell density. Further studies were performed to analyze the synergistic influence of residence time variation on foam attributes at different screw rotational speeds, die temperatures, and blowing agent contents.

“I undo you, Master”: Uncomfortable Encounters in the Work of Kara Walker

“I undo you, Master”Uncomfortable Encounters in the Work of Kara Walker Kim Wickham I walked away from both exhibitions … feeling that I had been exposed to a deadly toxin from which I needed to leave right away and find some spiritual mind-cleaning antidote to insure that I would not be infected for life. Betty Blayton Her silhouettes reflect psychic evolutions in race and race relations, chronicling the intricate twists and turns, the nuanced dance, as it were, which has been and continues to be performed between blacks and whites. Her art is visually graphic and aesthetically poignant. It lingers between shock and recognition. Michelle Carr What is it about Kara Walker’s work that can elicit such divergent, and charged, reactions? Is her work a brave, ironic confrontation with racism, or is it a minstrel show, a work in black face that plays on damaging stereotypes to appease a white audience? Since she hit the national (and international) art scene in the 1990s, Walker has generated an impressive amount of opinions, academic articles, and press, some positive, some negative, but all of it impassioned. Criticism of Walker’s work continues, as does her praise. Working with stereotypes from the “Old South” in the antiquated “craft” art medium of silhouettes,1 Walker depicts her all-black figures in various compromising sexual and moral positions.2 Her work is in many ways overwhelming. Figures abound in her dioramas, and they are engaged in any number of contorted/distorted/carnivalesque poses: they are defecating, urinating/being urinated on, bleeding, farting, suckling/being suckled, floating in the air, fellating/being fellated, and on and on.3 It is no secret that reactions to her work are often visceral, often negative, and almost always uncomfortable. Gwendolyn Dubois Shaw, in her moving and nuanced discussion of Walker’s work in Seeing the Unspeakable: The Art of Kara Walker, describes seeing “Upon My Many Masters” in the Spring of 1997 at the San Francisco Museum of Modern Art as follows: [End Page 335] Many of my fellow gallery visitors stood before the piece, jaws slack and eyes wide, staring in puzzled disbelief at what they were seeing, or at least at what they thought they were seeing. … It was a moment of communal visuality in which the act of viewing with the space of the gallery became a spectacular spectacle, a cyclical scopic activity in which museum patrons watched other museum patrons watching them back. … The phenomenological effect of the installation … was like a physical blow to the observer; it rendered many viewers temporarily disoriented and speechless. (Seeing the Unspeakable 1) What Shaw describes—disbelief, spectacle, disorientation, communality—all of these reactions depend upon the viewer making the act of interpreting part of the work itself.4 This participation is crucial, for, as Walker herself says, the silhouettes become a “blank space that you [can] project your desire into. It can be positive or negative. It’s just a hole in a piece of paper, and it’s the inside of that hole” (qtd. in Shaw 23).5 Julie Burrel writes of Walker’s work that its “shifting meaning demands the audience’s interpretive labor” and that “for an active viewer, Walker’s ambiguous images are readable yet retain … [an] ambivalence” (140): all characters are cast into shadow (Keizer 1666). The investment required, and the potential for negative interpretations,6 of the viewers of Walker’s images is starkly apparent in the recorded reactions to her work.7 While my own position on Walker’s work will inevitably become apparent, my goal is not to decide who is right—Walker’s critics or her supporters—as this controversy is, in large part, what matters and what is necessary in her work, but rather to examine how it is within these contentions that meaning is made, or rather, discovered. This paper seeks to “interpret interpretations” in order to interpret Walker’s work, to put negative reviews of Walker’s work into conversation with critics who see her work as more than “minstrelsy,” and to examine how both the silhouette and stereotype elicit such visceral reactions in the viewer. This paper will examine work done by a...