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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Structure-Property Relationships for Propylene/?-Olefin Copolymers: Effect of Short Branch Length
A single active-site-type catalyst was supported onto silica and used to produce propylene/ a-olefin copolymers with high isotacticity and high molecular weight. The effects of different reaction conditions such as temperature, pressure and hydrogen content on structural properties were investigated. Several comonomers with varying length and bulkiness such as hexene, decene, octene, dodecene, hexadecene, eicosene, and styrene were copolymerized with propylene. With the knowledge of the reactivity ratios and the effect of different reaction parameters on polymer microstructure, copolymers with the same level of comonomer content and similar molecular weight were made with different comonomer types. The produced copolymers were analyzed for their structural and rheological properties using GPC, DSC, CRYSTAF, NMR and RMS. Thus, the isolated effects of comonomer type (length and bulkiness) on structural and rheological properties were studied and correlated.
Morphology Control of Ternary Polymer Blends Using Interfacial Tension
Morphological studies for various ternary polymer blends were performed. The blends were prepared using a Haake batch mixer and analyzed using SEM and TEM. Interfacial tensions and spreading coefficients were used for predicting the blending morphology, and the predicted morphology was compared to the experimental results. The interfacial tensions were calculated from surface tensions at 20°C, and the temperature dependence of the surface tension and a harmonic mean equation were also used. All blending systems chosen in this experimental work were expected to have a minor component (B or C) encapsulated by the second component (C or B) in the matrix (A). It was found that many ternary blends (PC/PMMA/PE, PMMA/SAN/PBT, PBT/SAN/PC, etc) agree with the predicted morphology. However, some blending systems show an opposite encapsulation behavior (SAN/PC/PMMA) or a complex blending behavior (PP/PC/SAN).
New Compatibilizers for Styrenic/Olefinic Blends
Styrenic block copolymers (SBC's) are increasingly being used as compatibilizers (interfacial agents) in polystyrene and polyolefin blends with either virgin and/ or recycled resins. Many technical articles and patents on blends of styrenic and olefinic polymers indicate that styrenic block copolymers and more specifically styrene-butadiene- styrene copolymers function as compatibilizers. This paper reports the effectiveness of new block copolymers to compatibilize styrenics and polyolefins. In addition, a comparison of physical properties of blends using new block copolymers is made to those currently used in the industry.
An Experimental Investigation of the Effect of Polymer Processing Additives (PPA) on the Melting and Gel Formation Mechanisms in a Single Screw Extruder
Much work has been published showing how the addition of a polymer processing aid (PPA) has improved the processing characteristics on the single screw extruder. This paper will give insight on how the PPA affects a single screw extruder. Solids conveying, melting, and melt conveying were experimentally studied to determine how the PPA affected these important processes during extrusion leading to improvements in the melt quality.
Effects of Varying Strand Length on Shielding Properties of Conductive Elastomers in Near-and Far-Field Experiments
A new study examined the effects of varying the strand length of extruded conductive thermoplastic elastomer (TPE) pellets on the shielding efficacy of plaques molded of the material in both near- and far-field experiments. Results indicated that longer strand lengths yielded parts with higher shielding efficacy but at a cost of higher durometer and modulus. Data also indicated that far-field results were consistently higher than near-field values for the same materials and frequencies.
Effects of Processing Conditions on the Failure Mode of an Aliphatic Polyketone Terpolymer
The yield and failure response of an aliphatic polyketone terpolymer subjected to multi-axial stress states has been studied, with a focus on the effects of processing conditions on the failure mode. Testing has been performed on anisotropic hollow cylindrical samples of this semi-crystalline thermoplastic material. Samples were processed under 5 different extrusion conditions. It was found that the cooling rate has some effect on the failure mode, while the rate of extrusion is less significant. Possible processing effects that may account for the differences in behavior include residual stress, amorphous orientation, or crystal morphology.
Toughness Enhancement through Conversion of Cyclic Polybutylene Terephthalate to Linear PBT
The fracture toughness of macrocyclic polybutylene terephthalate (simple ring molecules) and linear PBT is correlated with the size of the plastic zone at the crack tip, which is inversely related to the yield stress. Macrocyclic PBT (c-PBT) molecules have a lower melt viscosity than linear molecules of comparable molecular weight, making them easier to process. However, the cyclic molecules are highly crystalline, with a high yield stress, and consequently a lower toughness. A ten-minute heat treatment in the melt opens the rings, and allows molecular entanglement, causing lower crystallinity of the solid polymer, and increased toughness. Therefore, control of the molecular structure of PBT provides a polymer with low viscosity that can be toughened by an easy heat treatment.
Effects of PP-MMA Alloy and Impact Modification on Weathering Performance of Polypropylene
The weathering performance of polypropylene and a novel polypropylene/acrylic alloy with and without impact modifier was investigated. Accelerated weathering testing was completed using Xenon Arc Weather-ometer. Surface cosmetics (gloss and color change), microscopy, and FTIR were used to characterize the surface and bulk properties after exposure to accelerated weathering. Dramatic improvements in weathering performance were observed through the addition of propylene/acrylic alloys and a proprietary impact modifier to the base polypropylene homopolymer. The individual significance of the propylene/acrylic and the impact modifier on weathering performance were similar. The benefit observed with weathering when combining the propylene/acrylic alloy and proprietary impact modifier was additive with respect to weathering performance.
Prediction of the Weld Lines in Injection Molding Process Using Neural Networks
A model is developed for the prediction of the weld lines in injection molding process. The position of the weld lines in a multigate cavity system, with holes and/or inserts in the part, are predicted using a neural network-based back propagation algorithm. The neural network was trained with data obtained from simulation and actual molding experimentation. For a number of test cases, the performance of the method is investigated on comparing predicted weld lines with those obtained using a complete mold filling simulation. It was found that the proposed method can predict the position of the weld lines with a good accuracy as compared to the filling simulation. Applying the neural networks reduced the amount of computational time and eliminated the pre/post processing time as compared to simulation methods.
The Effects of Mold Filling on Living Hinge Performance
Filling characteristics of polypropylene living hinges and their performance were compared in order to create a model that will predict the quality of living hinges. In this study, three filling characteristics correlated to hinge quality: melt front advancement, skin orientation, and hinge fill time percentage. First, the melt front advancement; should be parallel to the axis of hinge rotation and free from discontinuities. Then, the skin orientation must be perpendicular to the hinge's axis of rotation. Finally, the most critical parameter was the hinge fill time as a percentage of the fill time for the part.
Applications of Gas-Assisted Injection Molding and Injection/Compression Molding in Thinwall Molding
Gas-assisted injection molding (GAIM) and injection/compression molding (ICM) processes are studied and compared with the injection molding (IM) process for thinwall applications (also called thinwall molding). In this paper, analysts for these three processes arc carried out. A cellular phone part will be used as an example. Analysis results will be reported and comparisons of these three processes will be made. Injection pressure, clamp force and deformation will be used to evaluate these processes. Injection pressure and clamp force reduction in the GAIM and ICM processes and their effectiveness in packing will be emphasized.
Measuring Frosted Glass Effects for Plastics: A Closer Look at One Frosting Agent
To produce consistent frosted plastic effects it is necessary to measure basic performance characteristics of the frosting agents. Frosted plastic, like frosted glass, serves a variety of aesthetic and functional needs. In testing, the most crucial characteristics are transmittance, haze, clarity and yellowness This paper examines two sets of data: 1. Comparative results of testing a series of frosting agents at differing loads 2. Specific, in-depth results of testing a single frosting agent at differing particle sizes.
Super Phosphorescent Additives for High-Quality Illumination at Low Additive-Loading Levels
A new super-phosphorescent additive represents a breakthrough in the use of phosphorescence for plastic products. The new additive provides a substantially longer glow time than conventional zinc sulfide phosphorescent additives. Additionally, it, can be compounded at far lower loading levels, which facilitates compounding and processing, and makes the new additive more compatible with other fillers than zinc sulfide. This paper discusses attributes, applications, and performance characteristics of this novel product, and compares it to commonly used phosphorescent compounds.
Improvement of the Molded Part Quality-Optimization of the Plastification Unit
The three-zone plastification screws traditionally used in the injection molding process are nowadays limited in their efficiency. Reasons are increasing demands on the quality of the molded part and on the machine technology which is more and more adapted to the different process groups like packaging or optical parts. Therefore different types of screw geometry, e.g. barrier screws or multi-threaded screws, are used to investigate the influence of the dosing parameters and the screw geometry on the melting capacity and the homogeneity of the melt .
Shrinkage and Warpage Analysis of Injection-Molded Parts
Hot polymer melt shrinks when it is injected into the cold mold cavity. In the injection molding process, pressure is high near the polymer entrance and low at the last-fill location. The polymer temperature is low near the mold wall surface and high at the core region. Because of these two types of non-uniformity, the part will shrink differently at different planar and thickness locations. This causes warpage. Different process conditions will result in different non-uniformity. In this study, the effects of packing time, packing pressure, fill time and mold wall temperature will be discussed. Computer-aided engineering (CAE) and design of experiment (DOE) will be carried out first. The process window will be investigated. Experimental results will also be reported.
Quantitative Relationships between the Parameters of Thermal Degradation of Polyvinyl Chloride and the Loss of Mechanical Properties
Thermal degradation of polyvinyl chloride (PVC) was studied to obtain quantitative relationships between temperature and duration of polymer degradation and the corresponding loss of tensile strength, flexural modulus, and impact strength. Test specimens of rigid PVC containing different concentrations of dibutyltin bis(isooctylthioglycolate) and barium-cadmium stearate were subjected to five different temperatures for five different durations. The selected test properties were determined before and after degradation. Percentage property retention was plotted against logarithm of heating time. Values of log heating time corresponding to acceptable levels of property retention obtained from these plots were then plotted against temperature to obtain Arrhenius-type relationships between the parameters of thermal degradation and the deterioration of properties.
Injection Molding Process Simulation: A Productivity Tool for the Processor
To be productive as an injection molder you have to be innovative in using new technologies. To produce a high quality molded part you need a well designed part and mold, a molding cell which is able to mold the part within it’s specification, a plastic material which is produced to tight specifications and employees who are well trained. Would it be nice to train employees on how to run, optimize and troubleshoot a molding machine in a classroom environment and not on the production floor. On the production floor in order to make money the machines have to run and produce. A process simulator can fill the gap between learning theoretical knowledge and hands-on molding.
Enzymatic Template Synthesis of Processable Polyphenol
Phenolic polymers and phenol formaldehyde resins are of great interest for a number of electronic and industrial applications. Unfortunately, the toxic nature of the starting materials (formaldehyde) and extreme reaction conditions required for the synthesis of these polymers have severely limited their use in today's markets. We present here an alternative, biocatalytic approach where the enzyme horseradish peroxidase is used to polymerize phenol in the presence of an ionic template. Here the template serves as a surfactant that can both emulsify the phenol and polyphenol chains during polymerization and maintain water solubility of the final polyphenol/template complex. The reactants and conditions of this approach are mild and results in high molecular weight, electrically and optically active, water-soluble complexes of polyphenol and the template used. Polystyrene sulfonate, lignin sulfonate and dodecyl benzene sulfonate (micelles) were the templates investigated in this study. In each case, soluble polyphenol complexes were formed with molecular weights ranging in the millions. Thermal analysis and UV-Vis spectroscopy shows that these complexes have exceptional thermal stability and a high degree of backbone conjugation. Conductivities on the order of 10-5 S/cm and a?(3) of 10-12 esu are also observed. In the case of the SPS template under certain conditions, a sol gel complex may be formed. This enzymatic approach offers exciting opportunities in the synthesis and functionalization of a new class of processable polyphenolic materials.
Sharksin Melt Fracture in High-Performance Hexene-LLDPEs
Several types of High-Performance Hexene (HPH)-LLDPE have been introduced in recent years for high-strength blown film applications, with substantial enhancement of film properties over conventional Ziegler-Natta LLDPEs. The present work is a study of the comparative behavior of the various types of LLDPEs under processing conditions designed to induce sharkskin melt fracture (SSMF). Both capillary rheology and blown film studies were conducted. The ability of capillary rheology to capture the difference between resins in terms of their relative tendency to sharkskin melt fracture was investigated in parallel with blown film studies at different shear rates and die gaps. Film blowing is more effective in discriminating between resins and identifying melt fracture tendency. The influence of sharkskin melt fracture on the film properties was also quantified, showing the film impact strength to be affected most sensitively, and negatively, by the presence and severity of sharkskin melt fracture (SSMF).
Carbon Dioxide Extrusion Foaming of Engineering Thermoplastics
Many engineering thermoplastics require extrusion temperatures which are too high for foaming with chemical blowing agents. Carbon dioxide foaming by direct super critical fluid injection has no such restrictions as well as offering economic benefits. This study describes preliminary work on a laboratory scale extrusion line using retrofitted parts to produce foams from a number of engineering polymers. Results of an evaluation of a very simple low cost method for measuring melt strength (an important polymer property with regard to foaming) is also included.
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