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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Improvement of the Simulation of Shrinkage and Warpage by Characterizing the Material Behaviour More Exactly
Caused by the demand on shorter development times for technical products the use of simulation programs for the rheological, thermal and geometrical mould design increases. Up to the present, the prediction of shrinkage and warpage of semi-crystalline polymers is difficult because of the complex material behavior during the crystallization [1-3]. Therefore the influence of the thermal material data und parameters on the prediction of temperature profiles is intensively discussed at the IKV. The cooling rate is also considered in the pvT-behaviour.
Foaming of Polypropylene in Extrusion Processes
Various polypropylene grades were foamed using a small general-purpose twin-screw extruder. Cell diameters of ~70 µm and foam densities of ~14 kg/m3 were achieved with a conventional linear PP, using iso-butane as foaming agent. Linear and branched PP grades were subjected to dynamic rheometry and instrumented haul-off measurements, and the results are discussed in terms of melt strength, viscosity and elasticity. Promising results were obtained for branched materials produced by reactive extrusion.
Simulation of Draw Resonance in Film Casting Using a Material Description of Motion
This paper summarizes a strategy for the numerical simulation of film casting. The strategy incorporates time-stepping, an updated Lagrangian description of motion and viscoelasticity. The results for an approximately viscous solution agree very well with the theoretical solutions. For a Maxwell fluid it is noted that, as the relaxation time increases, the thickness gradient at the die increases and the velocity decreases. Also, for the case considered, a moderate relaxation time seems to destabilize the polymer.
Designing with Glass Fiber Reinforced Vinyl Composites II - Long Term Creep Considerations
Six years ago we initiated a long term study on the effect of time and temperature on the data sheet modulus values for glass fiber reinforced vinyl composites. Results after the first year showed that the measured creep modulii were higher than those predicted by time-temperature superposition of dynamic mechanical data. This paper presents five years of additional creep data and examines the effect of sample aging on the creep predictions.
The Use of Conducting Polymer Composites in Thermoplastics for Tuning Surface Resistivity
It is often difficult to provide consistent surface resistivity in the effective static dissipative range (about 105 to 1010 ohms/square). Thermoplastics incorporating traditional conductive additives generally exhibit discontinuous electrical behavior in this range. Conducting polymer composites have been created through in-situ deposition of conducting polymers onto carbon black substrates. By utilizing the inherent flexibility of these conducting polymer composites, compounds have been developed with controlled surface resistivity.
Learning from History: A Key Part of the Development Process of Insite™ Technology
One of the very first principles used to develop INSITE™ Technology, a major revolution in the polymer industry, was that of learning from history. Analyzing and avoiding repetition of mistakes to do product development worked very much to Dow's advantage as the major piece of technology advanced. Too often not enough time is allotted for contemplation of how to do better based on our collective experiences and wisdom. Particularly in developing new products, experience really makes a huge impact on the speed and success rate.
Nylon 6 in Thin-Wall Housings
To meet the challenging processing and performance demands for thin-wall housings, plastic materials must satisfy basic requirements for flow, impact resistance, and modulus. In this paper, select mechanical and processing properties of nylon 6 materials are examined for thin-wall-molding applications and compared with those for amorphous blends.
Quality Improvement of Foamed Seals for the Automotive Industry
Automotive body seals are becoming increasingly complex. As there is still little knowledge about the manufacturing process, extensive investigations are done to analyze the influence of the rheological behavior of the materials, the parameters of the extrusion process and the foaming/vulcanization on the quality properties of the foamed seals. The evaluation allows a better process understanding which in combination with improved test methods leads to an increased product quality and reduced manufacturing costs.
Pearl Lustre Pigment Modification - Improving Handling Characteristics
Synthetic pearl lustre like other high aspect ratio pigments exhibit poor solid flow behaviour. In the extruder based manufacture of thermoplastic masterbatches this limits output, by restricting the conveying capacity of the feed zone. Proprietary wax encapsulation technology now allows four fold or greater improvements in the extruder output without changing the particle shape or size distribution of the pigment prior to the compounding process. The encapsulation process also leads to low dust characteristics.
Comparison of Three Methods to Measure the Elongational Viscostiy of Polymer Melts: Entry Flow, Fiber Spinning and Uniaxial Elongation
The melt viscosity of three commercial polyolefines (LDPE, LLDPE and HDPE) was measured in uniaxial elongational flow at constant extension rate, as well as by the Rheotens and the Entry Flow Methods. The melts showed the same MFI but differed in their extensional properties, reflecting the differences in their molecular structure. The indirect methods could also give meaningful estimates for the extensional viscosity of polymer melts, if the amount of accumulated extensional strain in each case was taken into consideration.
Linear Viscoelastic Properties of Polymeric Suspensions
Linear viscoelastic properties of a model suspension containing hydroxyl terminated polybutadiene (HTPB) and glass beads with filler concentration up to 30% by volume were investigated by using a Haake parallel disk rheometer. For all the suspensions, it was observed that the rheological properties such as the storage modulus, G', loss modulus, G and complex viscosity ?* increases with the filler content ?. The relaxation spectra was calculated by using G' and G". The relaxation moduli Gi(?i?) decreased with the relaxation time ?i but increased with the filler content ?."
Chemical Assessment of Automotive Clearcoat Weathering
The top, clearcoat layer of an automotive paint job protects the under layers while maintaining a beautiful appearance for the life of a car. To determine clearcoat durability, effects of the weathering protocol, of the physical and chemical transformations and effects on the appearance must be considered. To this end, we will describe photoacoustic infrared (PAS-IR), and ultraviolet (UV) technologies and UV microspectroscopy to assay the changes in chemical composition produced in clearcoat paint systems by weathering.
A Thermo-Viscoelastic Model for the Modulus of Epoxy during Cure
The cure kinetics for a commercial epoxy have been established and the influence of the degree of cure on the glass transition determined. Time-temperature and time-conversion superposition principles have been built into a model that successfully predicts the development of the viscoelastic properties of the epoxy during isothermal cure from gelation to vitrification
Compatibilization of PET/HDPE Blends
Blends of Polyethylene terephthalate (PET) and High Density Polyethylene (HDPE) with and without compatibilizing agent have been studied. Both materials are widely used in the soft drink bottle industry. The compatibilizing agent was a copolymer of ethylene and methacrylic acid (surlyn). The olefinic segment of surlyn will be compatible with HDPE, while the acid groups will be affine with the similar groups from PET. The compatibility was investigated using different techniques such as differential scanning calorimetry, infrared spectroscopy, scanning electron microscopy and X-ray spectroscopy.
Contribution of Flow Deformation to the Shrinkage of Injection Molded PVC
The viscoelastic nature of PVC can not be ignored during the injection molding process. Strains imposed on the compound during the injection stage display recovery dynamics that are indicative of the temperature at which the strains were imposed. A mathematical model, employing approximate" time-temperature modulus relationships provided the basis for interpreting the shrinkage data. A distribution map of the various relative temperatures attained within the part during injection was determined."
Double Bubble Tubular Film Extrusion of Polybutylene Terephthalate-Polyethylene Terephthalate Blends
A technology has been developed to produce biaxially oriented films of blends of polybutylene terephthalate (PBT) and polyethylene terephthalate (PET) using double bubble tubular film extrusion. The mechanical instabilities and the mechanisms associated with their sources of occurrence are described. The films have been structurally characterized by wide angle X-ray diffraction and optical techniques. The structure of the film is related to processing conditions.
Structure Development in Melt Processing Polypropylene, Polypropylene-EPM Blends and TPEs
Fibers have been melt spun from polypropylene and its blends with ethylene propylene rubber, as well as polypropylene based thermoplastic elastomers under various conditions. The spinline stresses as well as kinematics have been measured. The fibers have been structurally characterized using wide angle x-ray diffraction and birefringence and the results interpreted.
Transient Start-Up Flow in a Modular Co-Rotating Twin-Screw Extruder
A model for flow start-up of a Newtonian liquid in an initially empty modular co-rotating twin screw extruder is developed. The changes of length of fill in front of the die and kneading disc block elements and output flow rate with time were predicted for various modular screw configurations. Experiments were also carried out on a laboratory modular machine with windows to verify the predictions. Generally, good agreement with the flow analysis was found.
A Comparative Study of Fiber Breakage in a Buss Kneader, Modular Co-Rotating and Counter-Rotating Twin Screw Extruders
The breakage of glass fibers was measured for several different types of continuous mixers including (i) Buss Kneader (ii) modular intermeshing co-rotating twin screw extruder (iii) modular intermeshing counter-rotating twin screw extruder. Comparisons are made using different screw configurations, loadings, different feeding ports and mixing elements. Downstream feeding of glass fibers and milder screw configuration favor less breakage of glass fibers.
Ultrasonic Thickness Gauge for Multi-Layer Plastic Fuel Tanks
A newly developed instrument, the Echometer measures the thickness of a barrier layer in multilayer polyethylene fuel tanks. Measurement by conventional pulse-echo ultrasound fails for thin barriers due to the large and highly frequency-dependent attenuation in polyethylene. The present instrument instead uses tone-burst excitation. Echo arrival time determines barrier depth, and frequency of minimum amplitude determines barrier thickness. Similar techniques may be applied to other layered plastic structures.
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