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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Importance of Injection Molding Parameters for Mechanical Performance of Cold Flow Weld Lines
Tensile and tensile-impact test results are reported on specimens with a cold weld line and identical specimens without weld line. Pairs of specimens without and with weld line have been injection molded simultaneously. Test results indicate that the effect of flow-induced stresses on weld line strength should be taken into account, in addition to the well-known influence of material temperatures during molding.
A Unified Approach for Thermoforming Numerical Simulation
In this paper, we present a unified approach for numerical simulation of thermoforming process. In contrast with iterative methods and dynamic explicit scheme, we propose a high order explicit algorithm based on the classical 4th order Runge-Kutta scheme. The proposed procedure is used to solve the global equilibrium equations and to integrate the sheet viscoelastic constitutive model. The error and time step size control is performed at each level which increase the procedure robustness and efficiency.
Feasibility of the Use of Polystyrene/Polypropylene Blends
The purpose of this investigation is to study the feasibility of PS/PP blends. The analysis of the results shows that compatibilization of the blend with one kind of SBS copolymer improves some mechanical properties of the blend. However, the amount of copolymer to be added depends on the intended specific uses. The cost/profit relation must always be observed.
Study of Staggered Flow Fronts with Applications to Sensor-Based Control
The present study examines several issues of relevance in the understanding and development of techniques for characterizing and controlling flow fronts developed in the VARTM (Vacuum Assisted Resin Transfer Molding) process. A sensor-based control system was used to selectively and autonomously compensate for lagging flow fronts resulting from permeability variations in the constituent preform. The fundamental control objective was to thoroughly impregnate the entire fibrous preform in a minimum amount of time, subject to minimizing the flow lag" induced by dissimilar preform peremeabilities."
Processing Trends of Metallocene Linear Low Density Polyethylenes and Their Influence on Single Screw Design
New families of polyolefin resins using single site catalysis technology, are being produced to enhance resin properties. The changes to the molecular architecture of these resins effect the rheological, thermal, frictional, and elastic properties; all of which play a significant role in screw design. This paper will investigate several polyolefin plastomers and compare them to a conventional linear low density polyethylene (LLDPE) to determine their impact on screw design.
Computing an Injection Fill Speed from a Relative Viscosity Curve
On-machine rheology is a methodology of determining the flow characteristics of a material at a given temperature with a specific mold and machine.  This methodology can be used to help determine the best injection fill speed to be used for a given material, machine and mold combination. This study presents a mathematical method to obtain an injection fill speed starting point when setting up a new mold, machine and material combination.
In Situ Polymer-Polymer Composites
In situ polymer-polymer composites of polypropylene / polyamide (PP/PA) have been obtained by a two step process. In the first step the components were extruded and the blend has been stretched at the exit of the die. In the second step, the blend was molded either by compression or by injection to obtain real organic composite materials with enhanced mechanical and thermal properties.
Polymer Melt Formation and Densification in Rotational Molding
Polymer melt densification, involving particle coalescence followed by the formation and dissolution of bubbles, has been studied in order to evaluate how it is affected by powder properties, chemical structure, thermal properties and rheology. A variety of rotomolding grade resins have been tested, in an effort to understand the mechanisms involved in the melt formation and its subsequent densification.
Effect of Formulation and Processing Conditions on the Viscosity of Masterbatches
Adding colorants and additives in masterbatches may affect the rheological properties of the resins into which they are mixed, but the extent of this effect has not been fully investigated. This paper reports on a design of experiments (DOE) study of the effect of 3 common colorants, 2 lubricants, a filler, an antioxidant, and 2 processing parameters (melt temperature and screw speed), on the viscosity of a linear low-density polyethylene (LLDPE) masterbatch. The series of experiments determined that only the lubricant and filler had a significant impact on resin rheology.
Press Forming of Filled and Short Fiber Reinforced Nylon-6
An experimental study was undertaken to examine the feasibility of press forming mineral filled and short glass fiber reinforced nylon-6. Press forming was conducted in a matched metal die much like the stamping operation used for sheet metals. The process parameters studied were the sheet preheating temperature, die temperature, forming pressure and sheet clamping. It was shown that with proper adjustment of some of these parameters, both mineral filled and short glass fiber reinforced nylon-6 could be successfully press formed.
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.
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