SPE Library

Proton exchange membrane (PEM ) fuel cells represent an attractive alternative to conventional power plants, especially the internal combustion engines (ICEs) used in motor vehicles. They are inherently more efficient than ICEs, which results in better fuel economy and lower fuel costs, have no moving parts, have lower CO2 emissions and do not emit common air-pollutants such as SO2, NOx and unsaturated hydrocarbons. A polymer electrolyte membrane is a crucial component of the PEM fuel cell. The membrane serves both as the electrolyte and as a separator to prevent direct physical mixing of the hydrogen at the anode and the oxygen at the cathode.

Global regulatory agencies are implementing strict guidelines associated with Transmissible Spongiform Encephlopathies (TSE). Medical manufacturers need to certify that their products are free of bovine derived products. In order to comply with these mandates, medical manufacturers must identify and address sources of their starting materials including active ingredients, excipients and reagents. Some additives utilized in the thermoplastic industry have bovine components.The following system allows a medical manufacturer to systematically search their processes and identify potential issues with meeting regulatory mandates.

Crosslinked rubbers and ground tyre rubber (S-GTR) have been treated using a surface grafting process allowing the incorporation of carboxyl and epoxy groups onto the polymer surface. The rubber were functionalised with glycidyl methacrylate (GMA) or methacrylic acid (MA) by photoinitiated grafting. The grafting degree of the rubber was determined by attenuated total reflectance Fourier-transform infrared (FTIR-ATR) spectroscopy. The grafted GTR can well be incorporated in various thermoplastics and thermosets. The surface grafting strongly enhances also the glueing ability of rubber sheets.

Polypropylene (PP) containing terminal unsaturation was modified with a hydride terminated polydimethylsiloxane (PDMS) through a catalytic hydrosilylation reaction in the melt phase at various temperatures. This paper presents a comprehensive study of the surface characteristics of these hydrosilylated polypropylenes (SiPP) using the axisymmetric drop shape analysis - profile (ADSA-P) technique and atomic force microscopy (AFM). Static and dynamic contact angle experiments were carried out using ADSA-P. The results of contact angle measurements show that the lower the reaction temperature, the larger the static/advancing contact angle, the smaller the permeability coefficient, and the more hydrophobic the surface. Surface topographic and compositional features were investigated using lateral force mode of AFM. All sample surfaces were rough on a micrometer scale and two different compositional domains were found to exist on the sample surfaces. The results show that decreasing the reaction temperature increases the amount of incorporated PDMS.

Mold release compounds can be transferred to molded parts and interfere in downstream painting, decorating, and bonding operations. These agents also accumulate on tool surfaces necessitating periodic cleaning which disrupts productivity and can involve the use of caustics or solvents. This study reports the promising results of using short duration exposures to UV irradiation to remove mold release compounds from both metals and non-metallic materials, such as plastics and polymer composites. In this study assorted materials were intentionally contaminated with heavy amounts of industrial mold release agents. The surfaces were rapidly and efficiently cleaned following exposure to high intensity UV light as demonstrated by a significant reduction in the water contact angle. UV treatments provide an environmentally benign alternative means to remove mold release compounds from tool or molded part surfaces.

Compared to alternative fire retardants, hydrated fillers are relatively ineffective, requiring addition levels of up to 60% by weight in order to achieve acceptable combustion resistance. This has a deleterious effect on melt viscosity and mechanical properties, commonly requiring use of surface treatments to offset these adverse effects. There would be considerable commercial benefits, therefore, if filler levels could be lowered through the combined use of synergists for hydrated fillers, without compromising fire performance.This paper reviews approaches, which have been reported or are currently being developed, for achieving more efficient fire retardant action using hydrated fillers in combination with co-agents including those formed from phosphorus, inorganic tin and boron compounds. The optimum mode of combining filler and co-additive is discussed with reference to physical admixtures and novel coated forms of hydrated filler.

The combination of properties at particle level has been accomplished by emulsion polymerization preparing core-shell polymers, to produce stable materials of technological importance. In this work, a change in properties in a more continuous way is sought varying copolymer composition during the second stage of the emulsion polymerization process. Gradient copolymer composition of the system (styrene/butyl acrylate) was followed by IR. Stress-strain, impact and mechanodynamic properties were evaluated. The results were compared with materials of equivalent global composition, obtained in two-stage seeded emulsion polymerization. Performance difference was notorious for certain compositions, showing the gradient materials higher deformation capacity.

A non-contact temperature monitoring technique based on fluorescence spectroscopy was used to measure the temperature of a polymer resin during capillary rheometry testing. Polyethylene and polycarbonate doped with a fluorescent dye, perylene, were used in experiments to measure resin temperature changes due to shear heating as shear rate in the capillary increased from 10 s-1 to 10000 s-1. Resin temperature at the exit orifice of a 1 mm diameter capillary die was found to increase monotonically with increasing shear rate reaching as much as 40 °C above the capillary set point temperature at the highest shear rates. The implications regarding rheometry testing are discussed.

Market demands that blown film processors produce multilayer film with the ability to thermoform and with improved properties such as barrier to moisture and oxygen. These properties require the use of materials with widely divergent melt temperatures. To coextrude materials of different melt temperatures, each individual material must be processed at its own ideal temperature. Temperature isolation in tested dies allows coextrusion of film consisting of materials with a melt temperature difference of up to 150°C. Based on trial results in Japan, USA and Canada this paper will demonstrate the ability to provide consistent temperature in each layer and super temperature isolation.

Many designers of plastic products have problems in understanding the complex mechanical behaviour of plastics. Their education is often more in the field of metals, which have a relatively simple mechanical behaviour up to 200 °C. Unlike for metals temperature and time (loading rate) determine the mechanical behaviour to a large extent. Moreover the structure of the polymer is of much influence on the mechanical properties.The content of this paper is based on teaching experience with students of Industrial Design Engineering. Although polymer engineering and designing in plastics are thought in each year, many students still have problems in understanding the structure related properties, the time and temperature dependent behaviour and the deformational mechanisms. I have made an attempt to summarise the mechanical behaviour using 10 essential figures.

The objective of this study was to investigate the potential of phenoxy resins as compatibilizer in the blending of polyamides and polyesters. Phenoxy resins react strongly with polyesters to produce grafted copolymers, which potentially can compatibilize immiscible blends of polyamide 6 (PA6) and polybutylene terephthalate (PBT). In this study, we considered ternary blends of two phenoxy resins with PA6 and PBT as both polymers are heavily used in automotive industry. Our study revealed that blends containing 5-30% by weight of phenoxy resins, although of two-phase nature, offered higher impact strengths and tensile modulus and much better phase-stability than uncompatibilized blends.

A siloxane oligomer, polymethylphenylsiloxane with with methoxyl end groups, was used as a toughening modifier for bisphenol-A diglycidyl ether (DGEBA) epoxy resins cured with 1,3-phenylenediamine (MPDA). The resins were synthesized by reacting the epoxy with the silxane at the catalyst tetraisopropyl titanate. The influence of siloxane contents on the thermal and mechanical properties of modified epoxy resins had a rougher fracture surface and higher fracture toughness compared to unmodified epoxy resins. The fracture resistance of the siloxane-modified epoxy resins increased with an increase of the siloxane oligomer content, while the fracture resistance at crack arrest increased only slightly. The glass transition temperature of the siloxane-modified epoxy resins did not change significantly with the content of the modifiers. A toughening mechanism based on the morphological and dynamic thermal behavior of the modified epoxy resins will be proposed.

This work examines the melting point and crystallinity behavior applying differential scanning calorimetry; mechanical properties by tension and Charpy-impact behavior and Melt Flow Index of recycled High Density Polyethylene, Polypropylene, and Polyethylen terephthalate used in blow-extruded and blow-injected bottles from post-consumer and post-industrial scrap. Some of the DSC results indicate a small decrease of the melting point for HDPE and a lower super cooling for the materials tested. Mechanical properties suffer minor deteriorations making possible the use of these recycled polymers in some industrial applications with reduction of cost.

In comparison to bisphenol-A polycarbonate, a copolycarbonate (based on bisphenol A and 30 mole% of 4, 4’-dihydroxydiphenyl) has a higher glass transition temperature and much better notched Izod impact strength under a variety of impact test conditions before and after annealing.The copolycarbonate’s outstanding impact strength is correlated with shear yielding, and well-defined secondary relaxations centered around –34 and –100°C in the dynamic-mechanical spectrum. The –34°C relaxation is attributed to the rotation of phenylene rings around the axis of “inter-ring” C-C bonds in the diphenylene groups, while the –100°C relaxation is attributable to the rotation of carbonate groups.

Some properties modifications of poly(3-hydroxybutyrate), P(3HB), by blending with ethylene-methacrylic acid copolymers either in the acid form (I-H) or partially neutralized with Zn (I-Zn) were investigated in an internal mixer. Thermal properties and the reactions between the polymers were evaluated by DSC, SEC and FTIR. A significant change in the crystallinity degree was noticed in blends containing I-Zn. The FTIR analysis of the chloroform soluble and insoluble fractions presented evidences of chemical reactions between the components during melt mixing. A significant amount of P(3HB) became insoluble in the P(3HB)/I-Zn blend, showing in this case that the reactions have occurred in significant degree.

Thermoforming represents an alternative to more common thermoplastic composite processes such as compression molding. An important step in the development of thermoformed parts is determining formability and final part thickness. Computer simulations are a low cost technique for estimating this information. This work presents a numerical model to simulate the thermoforming of a low density thermoplastic sheet reinforced with 55% glass fiber. The model stress-strain parameters were obtained as a function of temperature using a Bruckner biaxial stretcher. Pressure-thickness model parameters were obtained using a laboratory press. The results of the simulation are compared with data from a laboratory thermoformer and a small, simple mold.

Commercial thermoforming began in the late 1800s when cellulose nitrate was first skived into sheets, then steam heated and pressed against cool metal molds to produce baby rattles, hairbrush backs, and picture and mirror cases. Technological advances languished until WWII, when heavy-gauge acrylics were formed into fighter and bomber windscreens and canopies and thin-gauge cellulosics were formed into infantry relief maps. Since then, there have been many advances in plastics, machinery, and mold technology. Thin-gauge thermoforming continues to be driven by the packaging industries. Heavy-gauge forming benefits by rapid idea-to-consumer marketing needs and by the proliferation of designer" products. This paper will reflect on some of the ideas that spurred the industry growth in the past and some concepts that may lead to important advances in the future."

The complexity involved in the development and implementation of thermoforming-stamping processing techniques for continuous fiber reinforced thermoplastic composites (CFRTPs) demands the understanding of the deformation mechanisms of the composite during its forming as well as the development of the matrix microstructure as a function of the processing conditions. In this paper, after a brief presentation of some of the processes used to mold CFRTP parts, an overview of the composite deformation mechanisms inherent to the forming of 2D and 3D parts is discussed. The influence of the molding temperature, pressure and cooling rate on the development of the matrix microstructure and the mechanical behavior of CFRTPs is presented.

The joining of plastics micro parts is of high importance during the production of micro systems. Combinations of similar and different thermoplastics can be welded using the laser transmission welding process. For the selection of materials suitable for this process, the knowledge of optical properties is most essential. Laser light absorption, scattering and reflection influence the energy transport during the welding process and the quality of the joint to a high extent. The measurement of the heated area on the specimen surface by infrared thermography is a suitable test method to characterise optical properties of polymers for laser transmission welding.

Polymers with shape memory effect have garnered increased attention recently for use in real world applications. Compared with the shape memory alloys (SMAs), the shape memory polymers (SMPs) have the advantages that: (i) the transition temperature and the rubbery modulus can be tailored according to the application and (ii) the recoverable strain can exceed several hundred percent. One of the potential uses of these interesting materials is as a medical plastic; namely, SMPs offer potential use as smart" tubes and stents for both surgical implements and implantable devices. As tubes and stents SMPs can be initially fixed in a form needed and subsequently heated for strain recovery during surgery. In our lab we have designed and prepared a new type of shape memory polymer that features good shape recovery with tailored transition temperatures and recovery strength. We present thermo-mechanical characterization data for the new materials and briefly discuss their potential uses as medical plastics."