Plastic Manufacturing Industry Research Articles

Endocrine Disruptors: Bisphenol A and the Brain

Estrogens are known to trigger rapid cellular responses, including hormone secretion and cell permeability changes, in tissues as diverse as the pancreas, the pituitary gland, and the brain. Two studies published in the December 2005 issue of Endocrinology now present an intricate picture of how estradiol, the body’s primary endogenous estrogen, acts in the cerebellum, with one study building on the other and including another layer of complexity: the addition of the xenoestrogen bisphenol A to the system. The studies, conducted by researchers led by Scott Belcher at the University of Cincinnati College of Medicine, investigated an estrogen-mediated extracellular signal–regulated kinase system in developing rat cerebella neurons. The first study, conducted in vitro, identified the individual steps in a cascade of cellular responses triggered by estradiol. The second study focused on this response following injection of estradiol and bisphenol A, alone and in combination, into rat cerebella. Effects were seen at very low doses of 10−12 to 10−10 moles per liter (M) and at higher doses of 10−7 to 10−6 M, but not at intermediate doses of 10−9 to 10−8 M. Paradoxically, when bisphenol A was injected alone, it mimicked estradiol; when injected with estradiol, however, it blocked estradiol action. Bisphenol A is a known endocrine-active chemical. Low-level human exposure is widespread due to the chemical’s presence in polycarbonate plastic and epoxy resins, but understanding long-term consequences of exposure will be challenging. As illustrated in the Endocrinology papers, bisphenol A exerts an effect through a complex system at a concentration range that has not been evaluated in traditional risk assessment. “It is a fundamental part of endocrinology, and it is beautifully demonstrated [in these papers], that stimulation at [the cerebellar] cell surface receptor is able to cause effects at doses below a part per trillion,” says Frederick vom Saal, a professor of biology at the University of Missouri–Columbia. Not only are the doses many magnitudes lower than those considered in classic high-dose toxicity studies, but at extremely low doses both estradiol and bisphenol A demonstrate a response that disappears as the dose increases. “This absolutely challenges the fundamental assumption of risk assessment that once you start increasing dose you always see an increase in response,” says vom Saal. According to Belcher, an assistant professor of pharmacology and cell biophysics, labeling the effects observed in his group’s studies as harmful or negative is not possible. “With the way it’s been looked at, you can’t say whether the observed actions are safe or harmful, but it is clear that the issue needs to be looked at more carefully and seriously,” he says. Although the plastics manufacturing industry, represented by the American Plastics Council in Arlington, Virginia, generally questions several aspects of bisphenol A research, they do agree that translating findings such as those in the Endocrinology papers to the sphere of risk assessment won’t be easy. “It’s not so straightforward to figure out what the results mean for human health, even if you take the results that are published at face value,” says Steve Hentges, executive director of the American Plastics Council polycarbonate business unit. “Even to develop a testable hypothesis is not very simple at all. It’s very complex systems that they’re looking at. The mechanism is a long way from any kind of an adverse effect.” Belcher, too, believes that extending his work into risk assessment is premature. “You can’t make a conclusion whether bisphenol A is going to be safe or harmful with current risk assessment models at these low doses,” he says. Further, as shown by the paradoxical reaction to bisphenol A, responses to an estrogenic compound can depend on what else is in the system.

Interplas Show brings cheer to UK plastics

PurposeTo review manufacturing automation products and technology on show at Interplas 2005, the UK's premier exhibition of equipment for the plastics and rubber industry.Design/methodology/approachSome of the automation products on display at the show are highlighted, particularly the take‐out or beam‐type robots favoured by several of the injection moulding machine (IMM) manufacturers who produce their own version of these robots, including Arburg and Negri Bossi. Descriptions are also given of products from some independent automation equipment manufacturers including ATM, Geiger Handling and Wittmann. Beam‐type and articulated arm robots are described as well as end‐of‐arm tooling including CaviGrip exhibited by ATM, which through cooling within the tool can achieve dramatic savings by reducing the cycle time of IMMs. The contrasting benefits of beam‐type and articulated arm robots tending IMMs are debated. Also revealed is new articulated arm robot hardware and software technology developed by ABB specifically for plastics manufacturing automation. Finally, a brief case study is presented of a robot cell at Characteristix, a UK manufacturer of injection mouldings for the entertainment industry, which has helped it compete against the Far East.FindingsThere are manufacturing automation products available to the plastics industry that can help lift it out of recession. Articulated arm robots can add significant value to injection moulded products.Originality/valuePresents a review of the manufacturing automation technology now available to the plastics manufacturing industry.

Autoimmune Disease: Phthalate Linked to Lupus in Mice

No one knows to what degree genetics or environmental agents cause lupus, an autoimmune disorder that affects the skin, joints, and internal organs including the kidneys. However, researchers at Indiana State University may have strengthened the environmental evidence by discovering that phthalates trigger lupus antibodies in a mouse model. Phthalates are found in adhesives, cosmetics, fragrances, vinyl flooring, polyvinyl chloride pipe, and certain toys and medical supplies. According to a report out of the Centers for Disease Control and Prevention and the National Toxicology Program, published in the October 2000 issue of EHP, phthalate exposure is more extensive than previously suspected, especially in women aged 20–40 years. Other studies have pointed to possible links with asthma, rhinitis, and eczema in children as well as altered genital development in male infants. The new lupus findings add to a growing list of potential health effects caused by these chemicals. In lupus, the immune system loses its ability to tell the difference between foreign substances (antigens) and the body’s own cells and tissues. The immune system makes antibodies against the body itself, causing inflammation, tissue injury, and pain. Up to 1.5 million Americans have been diagnosed with lupus, and another 16,000 develop the disease each year, according to the Lupus Foundation of America. While investigating the gene sequence of a monoclonal antibody used as a marker for tumor growth, biochemist Swapan Ghosh, interim chair of the Life Sciences Department at Indiana State University, noticed that it shared 98% similarity with an antibody protein component (light chain) made by NZB mice, a popular model for autoimmune diseases. In lupus, such antibodies attack DNA in the kidneys, heart, and lungs. The finding, published in the December 2003 issue of Immunology, was a surprise: “I was not studying lupus or autoimmune diseases at all,” says Ghosh. But he took advantage of the unexpected turn and has launched a series of experiments to further explore the phthalate–lupus connection. In the latest study, Ghosh and graduate student So-Yon Lim injected four types of mice, including NZB mice, with di-(2-ethylhexyl) phthalate, or DEHP. Initially, all the mice generated antiphthalate antibodies, but only the lupus-prone NZB mice developed nephritis, which led to kidney failure and early death. The other mice initially produced antiphthalate antibodies, but the antibodies were counteracted by CD8+ suppressor T cells, which prevented kidney damage. “There’s something different about the immune systems of NZB mice [that makes them more susceptible to phthalates],” says Ghosh. The details of the investigation are reported in the August 2005 issue of the Journal of Autoimmunity. Although the phthalate–lupus connection has been observed only in mice, “many things found in the mouse immune system have proven to be true in humans,” says Ghosh. On the other hand, “not everything seen in a mouse model reflects what happens in humans,” cautions Betty Diamond, chief of rheumatology at Columbia University. Although Ghosh’s results are far from applicable to humans, they do raise several questions for future studies on the potential phthalate–lupus link in people. Do lupus patients have high levels of antiphthalate antibodies? Ghosh plans to screen lupus patients and healthy people in the future to find out. Does exposure to phthalates increase the risk for lupus? He plans to explore this, too, by measuring blood levels in workers exposed to phthalates in the plastics manufacturing industry. Lupus is five times more common in women than men. Might this be because women use more phthalate-containing cosmetics and perfumes than men do? The American Chemistry Council (ACC), an industry trade group, has criticized Ghosh’s study because he combined DEHP to proteins like bovine serum albumin. “The attached proteins may cause autoimmune and allergic responses,” says Marian Stanley, director of the ACC’s Phthalate Esters Panel. Ghosh counters, “We also studied DEHP not complexed to a protein, and it evoked an anti-DNA response.” He explains that he attached a main metabolite of DEHP to proteins because some studies have suggested that phthalate metabolites show an affinity for albumin in the body. So far, exposure to ultraviolet light is the only environmental factor that has been clearly linked to lupus in genetically susceptible patients. As lupus researchers continue to investigate other environmental causes, “we need to be open-minded, but not jump to conclusions,” Diamond says.

Alternatives for Industrial Upgrading in Global Value ChainsThe Case of the Plastics Industry in Brazil

Summaries This article addresses the challenges and limits for upgrading in the case of individual firms from developing countries. Their initial involvement in global value chains demand distinct sets of competencies depending on the characteristics of the chain, and their permanence in the chain requires a continuous process of self development dictated by the governance patterns. The conclusions are based on a study of the plastics manufacturing industry in Brazil, which has gone through a radical transition, from firms specialising in specific transformation processes supplying different types of markets to firms specialising in specific products supplying a specific type of value chain.

Elongational strength of polyethylene melt

A great deal of rheological study on polymer melts has been directed towards the flow characteristics due to shear. No doubt this is an important aspect in analyses of the polymer flow behaviour, however, product quality and the throughput rate of proceses such as blown film, melt spinning, blow moulding etc. are highly dependent on the understanding of another melt property other than shear, i.e. on elongational properties. Issues such as the blow-up-ratio of film bubbles, draw-downability, thickness of a parison etc., are dictated largely by the strength of the polymer melt under elongation. Similar to other rheological properties, elongational melt strength is a function of temperature and pressure (in terms of normal force). The present investigation was aimed at studying the effects caused by these two common processing variables (temperature and pressure) on the elongational strength of polymer melts based on a few selected polyethylenes, the findings being intended to be of practical significance for the plastics manufacturing industry.

Mineral polymer tooling system for making prototype fibre reinfoced composite parts

In the plastic and composite manufacturing industry the “time to market” and special, small series are getting increasingly important.When the production of a part is limited to a prototype or a small quantity, most conventional mould/tooling systems are either too expensive and take too much time to be build, or can not cope with the surface finish, production technology and raw materials of the future mass product.At the “Vrije Universiteit Brussel” (Belgium) new ceramic materials so called “Mineral Polymers (MiP)” are being developed. These inorganic materials can be cast, and are hardening out at atmospheric pressure and low temperature: between 15°C and 100°C. They present some attractive characteristics like low material cost, low shrinkage, low thermal expansion, fire incombustibility, high temperature resistance (up to 1200°C) and mechanical properties somewhere between those of technical ceramics and concrete.The interesting properties of mineral polymers make them well suited for prototype moulding. The mould can easily be made by pouring mineral polymer over the wax, plastic or plaster model, fitted with all inserts such as closure system, ejectors, heating and cooling devices. It is possible, by changing the amount and type of fillers and fibres, to tune the mechanical and thermal properties of the mineral polymers.The research work is focused on a number of fibre reinforced composite manufacturing processes, like: RTM, autoclave, RIM, SMC, BMC and injection. For each process a tooling system was worked out on material level. Moulds were made and tested out for prototype parts such as a three spoke bicycle wheel, a wheelchair wheel, fins for wind surfing, a part of a car body and some flat, box, curved and tube like test objects.

Melt flow rate and die swell ratio of blended polypropylene used in the fibre industry

The diversified applications of synthetic fibres of polypropylene (PP) and the advancement of spinning technologies in the recent years basically require the resin to have a broad range in its physical and mechanical properties. However, this requirement is difficult to be met due to a number of reasons including technological limitation and feasibility in the polymerization process, and the stringent properties requirements of some applications which cannot be satisfied by resin having too broad characteristics. One of the ways to overcome this situation is to adopt the practice of blending plastic resins as employed in the other branches of plastics manufacturing industry. However, such practice will greatly affect the overall characteristics of the blended materials which will in turn affect the processability and the ultimate properties of the finished products. Perhaps, melt flow rate (MFR) and die swell ratio (DSR) are the two most fundamental variables in this respect. This study, which is part of a very large project, aims to investigate the blend ratio effects on these two variables of PP used in the fibre industry.Eighteen samples were prepared for the investigation from five homopolymers having MFR in its pure form up to 800 g (10 min)−1. MFR was measured in a standard melt flow instrument, whereas, DSR was determined by a photographic technique. It was found that the MFR of the blended PP resins showed an exponential decaying characteristic rather than a linear relationship with the blended ratio as predicted by the weighted means approach. The results of DSR were, on the other hand, erratic.

Recycling of plastics

Considering the shortage of raw materials and environmental pollution, the recycling of plastic waste is a very important topic. Pilot plants for research in Funabashi Japan, Franklin (Ohio) U.S.A., and the R 80-process of Krauss Maffei, W. Germany, have demonstrated the possibility of reclaiming plastics from refuse. Old tyres and waste from the plastic producing and manufacturing industries are readily available. The pyrolysis of plastic yields gaseous and liquid products, and the exploitation of this cracking reaction has been demonstrated by pilot plants in Japan and Great Britain. Further laboratory scale experiments are taking place in W. Germany. In continuous fluidized beds and in molten salts, polyethylene, polypropylene, polyvinylchloride, polystyrene and rubber are pyrolysed and better than 98% conversion is obtained. Up to 40% of the feed can be obtained as aromatic compounds, and a pilot plant is under construction. As a first step PVC-containing material can be almost quantitatively dehydrochlorinated.