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.
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High-Performance Poly Metal Composites Replace Lead in Many Applications
A new injection moldable thermoplastic composite has been developed to eliminate problems associated with lead. This nontoxic polymer-metal composite can be formulated to meet the density, mass, and radiation-shielding properties of lead, while offering superior strength and design flexibility. The use of this material eliminates lead-toxicity issues encountered in handling, fabrication, and disposal. Target applications include: nontoxic projectile cores and shot, radiation shielding for medical and nuclear power, counterweights, sporting goods, ballast systems, vibration dampening, sound proofing, and many other applications where a nontoxic, high-density, high-strength material is required.
Ballistic Impact Resistance of Thermoplastic Composites
The correlation between adhesive strength, stiffness, flexural properties and ballistic impact resistance of Kevlar-KM2 composites with polysulfone (PSU) resin matrix was studied through examination of the failure of the composites on different processing conditions. Processing temperature greatly changed resin molecular conformation. Resin molecular conformation directly influenced composite flexural properties as well as ballistic impact energy absorption. Composites processed at 260°C showed significantly higher ballistic impact resistance than composites processed at 350°C. Significantly different failure mechanisms of these composites that are induced by different processing conditions are considered to be responsible for this result. The former exhibited mainly tension mode of failure whereas the later failed mainly shear cut. Fiber straining accompanied with delamination due to the tension mode of failure is the preferred failure mechanism for better ballistic impact energy absorption.
New Thermally Conductive Thermoplastics Offer Freedom of Design in Heat-Management Applications
A new thermally conductive compound available in a variety of crystalline thermoplastic matrices can be used to improve material management in a variety of industrial and consumer applications, including heat sinks, thermostats, heat exchangers, and as radiant heating coils. Replacing heavy metal shrouds and non-recyclable metallized plastics, the new compounds are non-corrosive, can be processed on all conventional thermoplastic equipment, and can even be melt reprocessed for in-plant recycling. A variant on the technology also produces compounds that are simultaneously thermally and electrically conductive.
Parameters Affecting the In-Line Measurement of Gas Solubility in Thermoplastic Melts during Foam Extrusion
The knowledge of gas solubility at processing conditions is of paramount importance for the understanding and optimization of extrusion foaming by gas injection. A recently developed in-line optical method is used to generate data of the solubility of atmospheric gases in PS and PET in single or twin screw extruders with gas injection capabilities. Overall, the in-line data compare favorably with off-line data where Henry's law constants were obtained from the slope of solubility/equilibrium gas pressure plots. Results obtained with the twin-screw extruder configured for improved mixing indicate: a) better data consistency, presumably as a result of enhanced homogenization/dissolution and longer residence time, and, b) a higher degree of sensitivity in detecting differences in the solubility of different gases.
Improved Organotin Stabilizers: Continuing Health and Environmental Research
Years of experience and significant research support using organotin mercaptides as PVC stabilizers. Safe use of organotin stabilizers involves following Material Safety Data Sheet instructions and using adequate engineering controls and/or personal protective equipment. Modifications of stabilizers to develop more efficient formulations continue. Product stewardship includes continued development of data to improve our understanding of the effects of materials. An overview of stabilizer trends in the industry, existing data, and planned health/ environmental research is presented.
Preparation of Microporous Films from Immiscible Blends via Melt Processing
Microporous films from immiscible blends were produced via melt processing and post-step treatments. Polystyrene (PS)/polypropylene (PP) and poly(ethylene terephthalate) (PET)/polypropylene (PP) blend systems with different viscosity ratios were studied. The blends were first compounded in a corotating twin-screw extruder and subsequently extruded through a sheet die to obtain the precursor films. These were uniaxially or biaxially drawn (100-400%) with respect to the original dimension to induce microporous structure and post treated at elevated temperature to maintain the porous structure which consisted of uniform microcracks in the order of a few hundred nanometers. The fabrication process here is shown to be a promising technique for producing microporous films that can be used for liquid and gas separations, as suggested from permeability measurements.
Polyethylene Synthesis Using Zeolites as Support Material for Metallocene Catalysts
In the synthesis of polyethylene, sodic mordenite and acid ZSM-5 zeolites were evaluated as support material for bis (cyclopentadienyl) zirconium dichloride catalyst system. The zeolites were calcinated at 300°C before treatment with methylaluminoxane (MAO) and Cp2ZrCl2. The supported catalyst systems were evaluated in terms of polymerization activities by varying the temperature of Cp2ZrCl2 impregnation on the support and the MAO and Cp2ZrCl2 concentrations.
Use of Contact-Atomic Force Microscopy in Plastic Material Surfaces
The operating conditions of an atomic force microscope in contact mode (C-AFM) were determined for polymer surface analysis. Isotactic polypropylene (PP), polyethylene terephthalate (PET), and polystyrene (PS) film surfaces were analyzed. The most important restriction was to obtain sharp and clear 3-D images of the polymer microstructure without causing any harm to the specimens by the microscope tip. The obtained operating conditions were a force around 10-9 N and a scanning frequency range from 1.0 to 1.5Hz. These operating conditions are very far from the normal ones used for other rigid materials.
High Molecular Weight Film Resins with Increased Stiffness
High Molecular Weight High Density Polyethylene resins for film markets typically fall into a relatively narrow range of densities to provide the desired product functionality. For example, resins targeted for the tee shirt bag market require tear and puncture properties that require melt indices of around 0.05 and densities around 0.950. Development of these resins and their respective bags has allowed for substitution of HMW-HDPE for paper in many markets. Additional substitution appears available, but require resins with both high strength and higher modulus. Using technology to produce bi-modal molecular weight distributions, film resins meeting these requirements have been produced. The resins and their end-use applications will be discussed.
Properties and Applications of Sandwich Panels Based on PET Foams
PET foams of variable densities, (1 g/cc to 0.2 g/cc), based on virgin and recycled material were produced by extrusion with physical or chemical blowing agents and evaluated as low density core in sandwich panels having M/F impregnated paper or flame retardant mineral reinforced PET as skin faces. Flexural and shear stiffness of the laminates were determined by variable span three point bending. Panels were also tested for thermal and moisture stability and compared with competitive sandwich constructions based on PVC foam, flake board, particleboard and plywood. Potential applications of the PET based laminates in building and construction are presented.
On the Experimental Investigation of High-Frequency Dielectric Sealing of PVC
This feasibility study deals with the investigation of welding Polyvinyl Chloride (PVC) sheets of different formulations, using high dielectric frequency technique. The experimental work consisted of PVC formulation (rigid sheet), mold design (new products), experimental design to quantify the effect of process parameters, mechanical characterization (tensile, peel testing) of the weld area, and process optimization. Rigid PVC formulation was selected based on two primary mechanical properties, tear resistance and shear modulus. The weld was well achieved within the studied range of parameters, while the processing conditions were experimentally optimized. Finally, new office items were successfully produced as a result of the design of new molds combined with new process layout (sheets).
Comprehensive Study of a New Extensional Flow Mixer
A patented Extensional Flow Mixer (EFM) (1) has been developed in which plastics is hydrodynamically mixed by flowing through a series of convergent and divergent regions so that very efficient dispersive and distributive mixing can be achieved. The EFM can be attached to any plastics pumping machine, such as single-screw and twin-screw extruders, for injection molding, blow molding, extrusion, and compounding. Comprehensive laboratory and industrial tests have been conducted especially for film applications, which indicate the mixing of a single-screw extruder (SSE) with an EFM can outperform that of a twin-screw extruder (TSE) in certain aspects. Results of gel elimination, strength enhancement and morphology changes are presented.
Pressure-Volume-Temperature Dependence in Polyvinylidene Fluoride and Polyvinylidene Fluoride-Hexafluoropropylene Copolymers
The relationship between pressure, volume and temperature (PVT) of polyvinylidene fluoride homopolymers (PVDF) and polyvinylidene fluoride hexafluoropropylene (PVDF-HFP) copolymers was determined in the pressure range of 200 to 1200 bars and in the temperature range of 40°C to 230°C. Differential scanning calorimetry (DSC) analysis was performed on each resin to simulate the cooling process during the PVT experiments and to determine the crystallization and melting temperatures at atmospheric pressures. The TAIT state equation describing the dependence of specific volume on the zero-pressure volume (V0,T), pressure and temperature has been used to predict the specific volume of PVDF and PVDF-HFP copolymers.
On the Prediction of Crystallinity Distribution in Injection Molded Semi-Crystalline Thermoplastics
Injection molded semi-crystalline thermoplastic parts show variable morphologies across their thickness. Process parameters such as injection speed, mold temperature, and melt temperature, play important role in forming these morphologies. The heat and shear history has great effect on the crystallization process of the semi-crystalline plastics. In this study, different available crystallization models were used to predict the crystallinity distribution, and capabilities of the models compared. Based on the results from these models, a more realistic model, which considers stress relaxation during the crystallization process, is proposed.
Properties of an Oil Resistant TPV
A TPV based on a dynamically vulcanized blend of epoxidized natural rubber and polypropylene is described. Morphological and rheological properties are briefly reviewed. Basic physical properties compare well with those of other TPVs whilst oil resistance is comparable to that of a well-compounded NBR vulcanizate (34% acrylonitrile). Excellent heat resistance with good retention of properties on ageing for extended periods at 100° and 150°C is also demonstrated as is good weathering and ozone resistance.
Rheology of TPV’S
The rheological properties of various TPV's have been studied in shear flow using dynamical mechanical spectrometry, capillary rheometry, transient stress buildup and shear creep. The TPV's which are commercial dynamically vulcanised PP/EPDM blends show a typical rheological behaviour with an apparent yield stress value at low shear rates, a shear-thinning viscosity at high(er) shear rates and, moreover, they do not obey the Cox-Merz law. This study revealed that the observed phenomena could be explained by the role of the three main components: PP, EPDM and oil.
Effect of Polyolefin Structure on Grafting of Maleic Anhydride
In this study the effect of polyolefin composition, i.e. ethene/propene ratio, on MA grafting and branching/crosslinking or degradation was investigated both in the melt and solution. The MA grafting content for PE and EPM was similar, but low for polymers with a high propene content. An increase of the ethene content results in a transition from degradation to branching/crosslinking.
Factors Affecting Adhesion of Tie Layers between Polypropylene and Polyamides
Adhesion properties were determined on five-layer coextruded cast films. With a few exceptions, the cap layers consisted of polypropylene, the tie layers consisted of blends of polypropylene and maleic anhydride-grafted polypropylene, and the center layer consisted of various polyamides. Up to a point, the adhesion increased as the overall film thickness and the level of maleic anhydride-grafted polypropylene were increased. The molecular weight of the grafted resin had a small effect on adhesion. Homopolymer diluent outperformed random copolymer diluents. Adhesion did not vary much when different types of polyamides were used as the center layer, but each exhibited much greater adhesion than an ethylene-vinyl alcohol center layer.
Investigations on Stretched Block Copolymers of Poly(butylene terephthalate) and Poly(tetramethylene oxide)
The changes in phase structure under uniaxial deformation of block copolymers of Poly(butylene terephthalate) (PBT) and Poly(tetramethylene oxide) (PTMO) have been investigated using 13C solid state NMR spectroscopy and infrared spectroscopy on in-situ stretched samples. The study was focused on the strain-induced crystallization of the PTMO. It became obvious that a minimum stress level in the material is necessary for the strain-induced PTMO crystals to form and to be stable at room temperature. The amount of crystalline PTMO is dependent on the stress level and on the temperature. We also found, that the PTMO crystallization is favored by a large PTMO block length and a large PTMO content.
Microfibrillar Composites with Ultimate Properties
In the past decade, numerous novel polymeric products were introduced, including polymer blends, for various applications in the automotive and electronic industry. Up to now a homopolymer as such has to be reinforced to meet the high demands on stiffness and strength in engineering applications and glass fibres were the major reinforcing element used in these materials. Microfibrillar reinforced composites based on polycondensates are new polymeric construction materials with ultimate properties. Such a composite has specific economical and ecological advantages since, upon recycling, a polymer blend is obtained which can be re-used to make again polymeric materials with specific properties.
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