The SPE Library contains thousands of papers, presentations, journal briefs and recorded webinars from the best minds in the Plastics Industry. Spanning almost two decades, this collection of published research and development work in polymer science and plastics technology is a wealth of knowledge and information for anyone involved in plastics.
Ethylene ionomers, such as Surlyn® from DuPont™, have been the premium sealant materials for packaging applications due to their excellent seal strength and process robustness. The ethylene ionomers achieve the unique property characteristics through the development of a network morphology. In this paper the development of new ethylene ionomers will be discussed. The versatile compositions and the unique morphology of the new ionomers will be presented together with the novel gas permeability properties. Their enhanced breathability to oxygen, carbon dioxide, moisture, etc., selective permeability, and smart barrier properties will be presented.
Cyclic olefin copolymers (COC) can provide film producers and packaging converters with an opportunity to create thermoforming films. COCs are amorphous thermoplastics with excellent moisture barrier, high temperature stability and stiffness. Mono- and multi-layer examples of LLDPE-based forming films, compared against commercially available products, clearly demonstrate how well the addition of COC improves physical properties, thermoforming and packaging performance. COC improves material distribution of LLDPE formed trays. These improvements enable the formed tray to withstand higher crushing force. Enhanced performance permits possibility of down gauging.
Car electronic components are potentially subjected to a very wide temperature range compared with electronic components in domestic appliances for example. In (very) cold regions temperatures can get as low a -60 °C and in the engine bay of a car temperatures of 100 °C and higher (near the engine) are easily reached. In cars these extreme temperatures not only put high demands on high tech components like printed circuit boards but also on the electrical wires in wire looms.We have studied the mechanical properties of PVC coated copper wire in a wide temperature range before and after subjecting the wire to an elevated temperature for a certain defined time.
In many current Liquid Crystal Display (LCD) systems, it is required to have light diffusing components. Light diffusing components are utilized to improve uniformity in illumination and increase viewing angle. They also serve to mask artifacts. For instance, the films are used to hide injection molded or printed patterns on the light guide pipe of the display or to reduce the appearance of moiré patterns generated by the interference of the LCD pixels with other regular structures within the system. In a typical LCD display, diffusion of light is introduced into the backlight assembly by adding separate films (i.e., a stack) that are comprised of a non-diffusing substrate to which a highly irregular, diffusing surface treatment is applied or attached. In this study, we present GE’s polycarbonate film systems to generate diffuse light in a monolithic film structure utilizing bulk diffusing additives. The relationship between the material properties of the bulk diffuser and the functional properties of the films is discussed.
Polylactic acid (PLA) film with good wettability and versatile reactivity was produced by photoinitiated grafting of N-vinylpyrrolidone (NVP) onto its surface using benzophenone (BP) as the initiator. The PLA film was melt extruded and a known amount of monomer solution containing the photoinitiator BP was deposited between two films, the assembled unit was irradiated under UV light at room temperature under nitrogen. The surface photografting parameters- grafting percent (Gp) and grafting efficiency (Ge) were obtained. The films resulting from this treatment were analyzed using differential UV spectroscopy, and water contact angle.
Hammer-mill processed bamboo fibers were used as the reinforcement fiber for an eco-composite made from wetlaid non-woven mats using polyethylene terephthalate (PET) fibers as the binding fibers. These eco-composites, containing up to 70 wt.% bamboo fibers, were compression molded and tested using dynamic mechanical analysis (DMA) in three-point-bending mode. The thermal behavior of the consolidated PET matrix was analyzed using a DSC. While all composites exhibited very good mechanical properties, the one with 40 wt.% bamboo fibers displayed the highest modulus. The glass transition activation energy calculated from time-temperature superposition suggests that some components from bamboo or moisture lowered the activation energy as the bamboo content increased.
Unique low molecular weight polyphenylene ether telechelic copolymers were designed specifically for use in a variety of thermosetting resins. These macromonomers have high solubility in common solvents and monomers and tailored functionality to co-polymerize via step-growth or chain-growth polymerization. The incorporation of these copolymers in epoxy and styrene based thermoset resins results in single-phase thermoset materials with enhanced performance. Noticeably, the glass transition temperature and toughness increase, the dielectric constant and loss factor decrease with increasing PPE content. These new materials thus show a property set very well suited for next generation electronic materials.
Polyethylene / montmorillonite (PE/MMT) nanocomposites films were prepared by blending in the molten state: Low-density polyethylene (LDPE), montmorillonite clay, and polyethylene grafted maleic anhydride (LDPE-g-MA) or zinc neutralized carboxylate ionomer (Surlyn B) as compatibilizers. A chemically modified clay Closite 20A has been used. Nanocomposites were prepared by melt blending in a twin-screw extruder by using two-step mixing. Characterization of the nanocomposites was performed by X-ray diffraction, infrared spectroscopy (FTIR) and transmission electronic microscope (TEM) techniques. Changes in UV irradiated nanocomposites film samples were characterized by FTIR. The results were analyzed in terms of the effect of the compatibilizing agent in the clay dispersion, and UV degradation of the nanocomposite.
Shear induced imbalanced filling in a geometrically balanced runner system is always a difficult problem to handle in injection molding. Moreover, the shear-induced temperature variation across the cross section also affects the warpage result. Previous research proposed that the melt rotation apparatus could control the warpage phenomena of parts. In this paper, we have proposed a new methodology to analyze this injection process. The comparison between the simulation and experiments can demonstrate and verify the warpage phenomena. The results show that the proposed methodology is a highly valuable tool to understand the melt rotation effects.
This paper presents the design and application of novel straight conformal cooling channels in reducing the process time for blow moulding process using the finite element analysis. Different configurations of cooling channels are designed for a blow mould of a plastic motor oil bottle and they are tested by running steady state and transient thermal analysis in Pro/Mechanica Thermal software to predict the cooling time. Results are compared with conventional channels with modified geometry. Results predict that proper layout of cooling channels can reduce the process cycle time by around 44% compared to conventional cooling layout.
Quality of injection-molded parts is determined by a lot of factors, such as machine, plastic material, operation conditions and others. Normally, using numerical or experimental method to examine and control all parameters is still very difficult. In this study, we proposed a computational intelligence-based method to obtain the optimal process windows systematically. In addition to this, this method can be used as an on-line monitor to predict part quality from process dynamics data. This method combines design of experiment (DOE) and neural network techniques for intelligent quality prediction. This approach is a potential method to improve the molding stability and molded part quality.
Through this work the rapid crack propagation of PE butt-fusion welded joints was evaluated with impact tests performed on sharp notched specimens at varying temperature and test velocity. The effect of test velocity was studied by means of the impact strength at 20ºC and 1, 2 and 3.7 m/s. The effect of test temperature was assessed at 1 m/s where dynamic effects are small and allow the application of Fracture Mechanics techniques. The Impact Toughness, Jc, was determined in a wide range of temperature (–60 to 20ºC). Complementary, SEM was carried out on fracture surfaces to elucidate the deformation mechanisms acting. It was found that independent of the testing conditions, they were only slightly inhibited in the welded samples suggesting that fracture propagation was practically not affected by the welding procedure.
The use of toughened propylene-based polymers in engineering applications has increased the demand for relevant data regarding yielding behavior in complex stress states. Through this work the yield behavior of polypropylene homopolymer, polypropylene copolymers and polypropylene elastomeric polyethylene mechanical blends was studied. This investigation proves that Modified Von Mises criterion provides reasonable predictions of the biaxial macroscopic yield behavior of these materials despite the inherent tendency of PP to deform by crazing. The incorporation of a second elastomeric-phase by melt blending or increasing crystallinity does not change the pressure dependency of PP polymers. The studied copolymers exhibited a more pronounced yield stress sensitivity to hydrostatic pressure than homopolymers and mechanical blends. Yielding envelopes decrease with increasing elastomer content in mechanical blends and enlarge with increasing crystallinity.
To illustrate the effect of crystallization rate of soft segment on shape memory effect in shape memory polyurethane (SMPU) ionomer, SMPU ionomers having ionic group within hard segments were synthesized. Isothermal crystallization kinetic method was used to analyze the effect of ionic groups within hard segments on crystallization of soft segment. Thermal cyclic tensile testing was conducted to investigate the shape memory effect. It was found that the ionic group in hard segments slows down crystallization of soft segment; when physical cross link is strong enough, the crystallization rate would be a predominant factor determining the shape fixity ratio after various cooling time; when physical cross link is weakening, the influence of crystallization rate is much less for cooling time dependence of fixity.
Phase separation of polymer blends can be directed by the difference of the attraction factors to the polymers on a patterned substrate to achieve polymer self-assembly. A 2D model of the Cahn-Hilliard equation was established using an unconditionally gradient stable time marching scheme. The morphology development in the early stage of the phase separation on a template guided self-assembly was investigated through numerical simulation. Through the numerical investigation, it was observed that the morphology evolution of the polymer blends depended on the consistency of the initial concentration, strength of forcing function, scaling factor, the gradient energy coefficient, and material properties.
Polymeric films have become more attractive materials for multipurpose applications. In order to adapt them to several kinds of applications, extra functions keeping their bulk characteristics are desired. Modification of PP films through a grafting technique is considered to be one of the main routes to overcome their limitations avoiding coating delamination and without affecting bulk polymer properties. Through this paper the superficial nano-mechanical properties, bulk mechanical properties, and fracture behavior of surface graft copolymerized with acrylic acid PP films are reported.
Designing medical appliances for plastics assembly requires a comprehension of the various plastics joining methods, a knowledge of joint designs and material selection plus an understanding of their relationships.Medical devices comprise an elite group of parts within the plastics joining arena which have a unique set of finished assembly criteria. Strength requirements due to forces exerted on commonly small mechanical devices used in surgical procedures must be such that the assembled devices are failsafe during operations.Seal requirements of vessels must be hermetic to prevent leakage of gasses or liquids either in to or out of a chamber. Surface marking of the device must be nonexistent for not only cosmetic requirements but also for the ability of the device to slide freely over living tissue. Rough surface crevices may harbor bacteria and can not be tolerated.Understanding the principles of plastics joining, the capabilities of each method and proper implementation of the appropriate joint design, can provide the designer with a clear direction at the outset and a successful an repeatable assembly result for the part.
Chain entanglement is an essential concept in polymer science. It has been explored for six decades since the 1946 transient network theory of Green and Tobolsky. Another three decades after the 1971 de Gennes' reptation idea have passed before a method has been devised in computer simulation to depict chain entanglement . More recently, the time-resolved determination of velocity profiles during and after shear of entangled polymers  have led to a specific molecular mechanism for chain disentanglement . This work describes the latest understanding on the subject of polymer flow.
A continuous chaotic (smart) blender was used to controllably produce a wide variety of morphologies in polylactide acid (PLA) - linear low density polyethylene (LLDPE) blends at LLDPE compositions of 20% and 30% by volume. The structured blends were extruded as films. In comparison to typical blends obtained by mixing consisting of droplets, results indicate that blend morphology can be selected with the chaotic blender to simultaneously improve permeability and impact toughness. Both properties benefit from high frontal area and interconnected shapes derived from multi-layers formed initially by the stretching and folding mechanism characterizing chaotic motions in the melt.
The influence of coupling agents on the melt rheological properties of HDPE/wood flour composites has been investigated in this work by means of a capillary rheometer. Scanning electron microscopy was also employed to supplement the rheological data. It was found that molecular weight and molecular weight distribution of the polymer matrix and coupling agent characteristics influence the melt flow properties of the filled composites. Generally, low molecular weight and narrow molecular weight distribution polyethylene matrix provides larger increase of the viscosity of the composites with respect to the unfilled resin. Coupling agents tend to increase the resistance to shearing, but wall slip effects may interfere with the measured values, especially at very high filler loadings.
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