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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CHARACTERIZATION OF MICRONIZED RUBBER POWDERS WITH COST EFFECTIVE PERFORMANCE BENEFITS IN RUBBER COMPOUNDS
Micronized Rubber Powder (MRP) is classified as dry, powdered elastomer in which a significant proportion of particles are less than 100 microns. It is used as a compound extender to offset the spiraling prices of natural and synthetic virgin rubber materials. MRP is typically made from cured elastomer feedstock via a cryogenic process at a temperature below the Tg of the polymer. A better understanding of MRP surface properties is needed to facilitate efforts to utilize the material as a high value, sustainable material for use in various industrial and consumer rubber products. An update on MRP characterization is presented, including surface morphology by SEM, surface chemistry by XPS, surface area by Kr BET, and particle size distribution by laser diffraction. An example is given that demonstrates how the surface chemistry can be used to explain the effect of MRP on cure and physical properties in rubber compounds.
MULTIFUNCTIONAL COMPOUNDS USING CARBON NANOSTRUCTURE ENHANCED GLASS REINFORCEMENTS IN ELECTROMAGNETIC COMPATIBILITY APPLICATIONS
A new class of thermoplastic reinforcements was recently developed using technology whereby carbon nanostructures (CNS) are grown on the surface of glass fibers. This hybrid reinforcement results in specialized, multifunctional thermoplastic compounds that exhibit 60 dB of electromagnetic interference (EMI) shielding. This paper will discuss the recent research that has been conducted in incorporating the carbon nanostructure/glass fiber hybrid into polycarbonate/acrylonitrile-butadiene-styrene (PC/ABS) and polyamide-6,6 (PA-6,6) and give a highlight of the material properties of the resulting compounds.
AN OVERVIEW OF SIZING CHEMISTRY AND ITS IMPORTANCE IN COMPOSITE PROCESSING AND PROPERTIES
Sizing is applied to carbon and glass fiber during manufacturing to protect the fiber during and after production, impart processability, enable composite fabrication and provide interfacial adhesion between the fiber and matrix resin. If the sizing’s only function was to improve processability then it would be possible for one sizing to “fit all”, however interfacial adhesion is critical and for every matrix resin a different sizing chemistry is required. This presentation will provide an overview of sizing chemistries available and examples of their impact on processing and mechanical properties.
COMPARISON OF MASS TRANSIT MATERIAL FLAMMABILITY REQUIREMENTS AND TRENDS FOR AIRCRAFT AND TRAIN APPLICATIONS IN EUROPE AND NORTH AMERICA
Establishing meaningful and reliable flame, smoke and toxicity (FST) requirements for aircraft and train components made from engineering thermoplastics is an ever-evolving task for the mass transit authorities throughout the globe. This paper attempts to clarify the current state of the US and EU regulations, the associated test methods and typical FST performance of the polymeric materials used today in the mass transit markets. Pending improvements to current FST requirements by the US FAA and the EU EASA regulating bodies, including provisions for heat release and smoke density, are also discussed.
RHEOLOGY AND MELT FRACTURE OF BIODEGRADABLE POLY (?-CAPROLACTONE) POLYESTERS
The viscoelastic behaviour of a number of commercial and newly synthesized linear biodegradable polyesters - poly (?-caprolactone) (PCLs) with different molecular characteristics was investigated using both rotational and capillary rheometry. The variation of the zero-shear viscosity and relaxation spectrum with molecular weight was studied in detail. The PCL processing instabilities were studied by capillary extrusion using a number of capillary dies having various diameter and length-to- diameter ratios. Sharkskin and gross melt fracture was observed at different shear rates depending on the molecular characteristics of the resins and the geometrical details of the capillary dies.
UNDERSTANDING THE IMAPCT OF PIGMENT LOADING LEVEL ON INJECTION MOLDED COMPONENTS
Pigment loading level is one of the most critical factors, governing the properties of the injection molded components. Changing the ratio of the pigment (Colorant) to the base resin could result in failure of the molded component. Material characterization such as Thermo Gravimetric Analysis (TGA) can be conducted to determine the pigment loading level and correlate the failure with functional characteristics of the molded component. Higher concentration of the pigment results in loosing mechanical property of the plastic and thus resulting failure during end use of the product.
DEVELOPMENT OF A METHOD FOR MEASURING THE THERMAL CONTACT RESISTANCE AND THERMAL CONDUCTIVITY OF ELECTRONIC MOLDING COMPOUNDS
The process simulation of thermoset molding processes (e.g. transfer molding, liquid injection molding) becomes increasingly important, because it can significantly reduce the cost of product development. This demands the correct determination of heat transfer and rheological coefficients. The aim of this study was the designing and construction of an apparatus which can measure the thermal contact resistance and thermal conductivity of epoxy molding compounds in the same circumstances which they encounter during processing.
ELECTROMAGNETIC INDUCTION COIL DESIGN FOR MOLD SURFACE HEATING
The objective of this study is to find an optimal design of electromagnetic induction coil for mold surface heating. To simulate the temperature distribution of mold surface in the induction heating process, the commercial software of COMSOL Multiphysics is employed. Design parameters such as induction coils include coil diameter, heating distance, coil space, and electromagnetic induction frequency are considered in this research. The Taguchi method is used to analysis the effects of process parameters on the mold surface temperature distribution and heating rate. The simulation shows that: (1) coil diameter and coil space are the most significant parameters of affecting heating rate and temperature uniformity. (2) Small coil diameter increases the heating rate but results in non-uniform heating temperature. (3) Short heating distance is helpful for the heating rate but creates worse temperature variation. (4) Small coil space results in fast heating rate but generates significant temperature difference. (5) High induction frequency facilitates heating rate.
NANO-COMPOSITES CHARACTERIZATION BY HYPER DIFFERENTIAL SCANNING CALORIMETRY (HYPERDSC)
Thermal analytical techniques that are used to characterize nanocomposite formulations. Differential Scanning Calorimetry (DSC, HyperDSC™), Thermogravimetry (TGA), Dynamic Mechanical Analysis (DMA), and the hyphenated technique Thermogravimetry-Gas Chromatography-Mass Spectrometry (TGA-GC-MS), are used to measure nanocomposites. These measurements help ensure that the nanocomposite manufacturing process is stable, reproducible, and reliable. This poster concentrates on the formulation and end product validation through Differential Scanning Calorimetry (HyperDSC™) characterization of the rigid and mobile amorphous fractions of a nanocomposite.
USING SIMULTANEOUS DSC-RAMAN TECHNOLOGY TO STUDY CRYSTALLIZATION OF NYLON 6
Nylon 6 (polycaprolactam) is a polyamide that is widely used in the form of fibers. There are two crystalline forms, ? and ?. The common ? form has a fully extended planar zigzag conformation. The ? form differs in the hydrogen bonding between chains which produces a twisted gauche conformation about the C-N bond of the amide group. This change in conformation leads to significant differences in the Raman spectra of the two forms. The crystallization behavior of nylon-6 is known to differ between virgin and previously extruded material. DSC measurements show that crystallization from the melt occurs at about 173°C for virgin material but at about 185°C for samples that have previously been extruded. Combined Raman and DSC measurements provide different insights into thermally induced phase changes. In the case of semi-crystalline materials Ramandata gives qualitative information about molecular conformations to complement the purely quantitative information from DSC. We have used this approach to study crystallization in nylon-6.
CO-ROTATING FULLY INTERMESHING TWIN-SCREW COMPOUNDING EXTRUDERS: ADVANCEMENTS FOR IMPROVED PERFORMANCE AND PRODUCTIVITY
The co-rotating fully intermeshing twin-screw extruder is the primary production unit for compounding of polymer based materials. It also has had a long term presence in processing material in the chemical and food industry and more recently in pharmaceuticals. While this equipment celebrated its 50th anniversary several years ago and might be considered a “mature” technology, it has not experienced a decline in new developments as might be expected, but rather a significant number of advancements continue to evolve. This paper will highlight several significant developments of the past 10 to 15 years. These are the implementation of high torque (power) designs, the use of increased rpm in conjunction with high torque for improved operating flexibility and productivity, and finally a technology breakthrough for feeding difficult to handle low bulk density materials.
EFFECT OF NANOCLAYS ON THE COMPATIBILITY OF MALEIC ANHYDRIDE-GRAFTED-POLYPROPYLENE/POLY (ETHYLENE OXIDE) BLEND
This study investigated the effect of surface modification of nanoclays on the compatibility of Maleic Anhydride-grafted polypropylene (PP-g-MA)/poly (ethylene oxide) (PEO) blends. Rheological testing confirmed the network formation of nanaoclays of all types. SEM confirmed the emulsifying role of nanoclays by reducing the PEO domain size. For the case of using dialkyl (C18)-modified nanoclays, mechanical testing showed that the elastic modulus and the toughness were respectively improved by 20% and 55% compared to unfilled samples.
TEMPERATURE DEPENDENCE OF THE INTERFACIAL SHEAR STRENGTH IN GLASS–FIBER POLYPROPYLENE COMPOSITES INVESTIGATED BY A NOVEL SINGLE FIBER TECHNIQUE
To obtain information on the temperature dependence of the interfacial strength (IFSS) in glass – polypropylene composites a thermomechanical analyser was adapted to enable microbond testing to be carried out in a well controlled temperature environment. Test results obtained by TMA-microbond testing showed excellent comparability with those obtained by normal microbond testing. The of IFSS of glass – polypropylene was measured from -40°C up to 100°C. The IFSS showed a highly significant inverse dependence on testing temperature.
COMPOUNDING EXTRUSION OF POLYPROPYLENE CARBON NANOTUBE COMPOSITES: OPTIMISING AND ECONOMIZING PROCESS WITH A COMMERCIAL PERSPECTIVE – A CASE STUDY
Compounding extrusion of Polypropylene-Carbon nanotube composite is presented as a case study with Design of Experiments approach to identify best processing parameters for optimum dispersions and conductivity. Influence of Specific Mechanical Energy input on resulting morphology and volume resistivity of extruded strands are analyzed with statistical viewpoints. Resistances of the melt are measured with an online process monitoring approach and correlated with measurements on extruded strands. This aids process planning, and economization.
INVESTIGATIONS OF THE BRITTLE FAILURE CAUSED BY AN ENVIRONMENTAL STRESS CRACKING OF A PLASTIC ENCLOSURE
The causes of a drastic reduction in the service life of plastic enclosures molded from an acrylonitrilebutadiene- styrene (ABS) resin have been investigated. The mechanism and type of failure have been deduced from a detailed morphological examination of the fracture surface. Various factors responsible for a rapid failure of the enclosure have been identified. Analytical testing such as infrared spectroscopy and differential scanning calorimetry were performed to identify a specific material characteristic responsible for the failure. The results obtained during the evaluation indicated that the failure was due to environmental stress cracking, which occurred as a consequence of the presence of an incompatible chemical and assembly stress. The nature of the chemical agent was found and its effect on the properties of the ABS is discussed.
FLOW BEHAVIOR OF DIFFERENT POLYETHYLENES IN CAPILLARY FLOW
Three major polyethylene (PE) engineering plastics, linear-low-density (LLDPE), low-density (LDPE) and high- density (HDPE) are studied in capillary flow. The purpose is to find experimentally and predict numerically their flow behaviour, namely the pressure drop in flow through tapered dies. This behavior is related to their individual rheological and flow properties. Using a series of capillary dies having different diameters D and length-to-diameter L/D ratios, a full rheological characterization has been carried out, and the experimental data have been fitted with the viscoelastic K-BKZ/PSM model. The branched LDPE has a strong pressure-dependence of viscosity, with a pressure-dependent coefficient ?p. For the linear LLDPE and HDPE melts, the pressure-dependence of viscosity is weak, but slip at the wall is strong and affects their flow behaviour. Thermal effects due to viscous dissipation are included but are rather mild. It is found that the viscoelastic simulations are capable of reproducing the experimental data well, in the whole range of apparent shear rates and L/D ratios.
SOME ISSUES ARISING IN FINDING THE DETACHMENT POINT IN CALENDERING OF PLASTIC SHEETS
Calendering is a process for producing plastic sheets of a desired final thickness and appearance. The thickness of the exiting sheet during a calendering operation is uniquely found by the Lubrication Approximation Theory (LAT) and the application of the Swift boundary conditions, which dictate that both the pressure and its axial derivative are zero at detachment. This cannot be used in a 2-D analysis of the process, where the detachment point is the anchor of a free surface, and hence a singular point where both the pressure and the stresses go through numerical oscillations. This difficulty can be circumvented by using the Boundary Element Method (BEM), which uses as primary variables velocities and tractions, and thus avoids pressures and stresses. Then the detachment point is found as the point where the tangential traction becomes zero. Numerical tests undertaken here with the Finite Element Method (FEM) show that the LAT results can be used as a good approximation for the detachment point, which is then fixed. Comparisons with 2-D BEM results show a good agreement for all flow field variables. However, the exact position of the detachment point in a 2-D FEM analysis is still elusive, since for viscous polymer melts the contact angle is not known and should be part of the solution. Some thoughts are given about how to tackle this still unresolved issue, based on double nodes with discontinuous velocities and pressures.
MISCIBILITY CHARACTERIZATION OF INDOMETHACIN AND EUDRAGIT® E PO BY RHEOLOGICAL AND THERMAL ANALYSIS
The miscibility between drug indomethacin and excipient Eudragit® E PO were extensively characterized by rheological and thermal analysis. The evolution of glass transition temperature and activation energy with indomethacin concentration indicates the existence of overall positive deviation which represents anti-plasticization effect. The rheological analysis is in agreement with the thermal analysis, and both methods indicate that the miscibility between them is very good for indomethacin concentrations up to 60~70%.
BLOWN FILMS OF NANOCOMPOSITES PREPARED FROM ORGANOCLAY/COPPER-NANOPARTICLE POLYPROPYLENE
Polypropylene blown film containing 1 wt% nanoparticles was fabricated which organoclay and copper nanoparticles were incorporated for barrier and antimicrobial purpose. Effect of copper nanoparticle content (5, 10, 15 and 20 wt% of total nano-fillers) on clarity and mechanical properties of polypropylene nanocomposite film was investigated. Nanocomposite PP films were fabricated via water-quenched blown film extrusion. A sodium neutralized ethylene-methacrylic acid ionomer of 2 phr was used to modify compatibility between polypropylene and nano-fillers.
ENHANCED DIELECTRIC LIFETIME OF MULTILAYERED PC/PVDF-HFP FOR CAPACITOR APPLICATIONS
The dielectric lifetime and breakdown mechanism of PC/PVDF-HFP systems were studied under constant DC field. The 32 L and 256 L PC/PVDF-HFP systems show two orders of magnitude longer dielectric lifetime compared with blend system of PC/PVDF-HFP. It is attributed that the layered structure can impede the breakdown process by deflecting the fracture propagation pathway. The DC resistivity of PC/PVDF-HFP systems was measured and correlates well with the dielectric lifetime in PC/PVDF-HFP system, which implied that the DC resistivity is also an important factor contributing to the enhancement of dielectric lifetime of the layered films.
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