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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Sam Miller, James Donovan, William MacKnight, Roger Kambour, May 2000
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.
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.
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.
Patrick J. Brannon, Bart LiPetri, Carol M.F. Barry, May 2000
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.
T. James Wang, Shia-Chung Chen, H.H. Chiang, May 2000
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.
Z. Fan, R. Zheng, P. Kennedy, H. Yu, A. Bakharev, May 2000
The requirement to create a shell model on the midplane of the part for warpage analysis is at odds with the trend toward solid modeling. A method is introduced that enables warpage analysis without the midplane model. This ensures that the user interacts only with the solid geometry. In this paper we present results obtained with the new technique and compare them to those obtained on a midplane model.
Chaotic mixing of binary components has been recently used to produce and distribute fibers, multi-layer films, and fragmented sheets in melts. Formation mechanisms and means to promote one type over the other remain uncertain. In this study, in situ film formation and breakup in PS/LDPE blends was examined for differing extents of mixing. Results demonstrate new opportunities to develop distributed multi-layer films during blending processes.
Olga I. Kuvshinnikova, Robert E. Lee, Nick A. Favstritsky, May 2000
The purpose of this paper is to present the data on UV stabilization of flame retarded polypropylene fiber. The evaluation was conducted by exposure in the xenon arc weatherometer @ 63°C under dry conditions. Proprietary additives provided unique physical property retention for flame retarded polypropylene fiber.
Thomas M. Ellison, Stephen P. McCarthy, Arthur K. Delusky, May 2000
Thermoplastic film technology and a new plastic molding process, under development in a joint effort by ValTek and U Mass Lowell, combine to offer reductions in system cost, total emissions and weight for automotive Class A" exterior panels in the new millennium. The recyclable structural panels are fabricated using Class "A" film finishes in one step and targeted for vertical and horizontal automotive panels."
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.
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.
Dipole dynamics in network-forming polymers were investigated by broadband dielectric relaxation spectroscopy (DRS). The changes in reorientational dynamics during the advancement of reactions were used to (1) describe the molecular origin of various relaxation processes (?,?), (2) describe the dynamics in terms of the location and intensity of relaxation spectrum, and (3) advance an interpretation of network dynamics in terms of intermolecular cooperativity. The chemical state of network at various stages of cure was identified by simultaneous DRS and remote fiber-optic FTIR.
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.
Ferdinando F. Bruno, Ramaswamy Nagarajan, Jena S. Sidhartha, Ke Yang, Jayant Kumar, Sukant Tripathy, Lynne Samuelson, May 2000
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.
The idea of using an impact tower for 3-point bending for polymer testing has been developed before [1]. In this work the experimental method is refined. The vibrations are reduced by removing the ends of the specimen and by using a smaller span. Results are presented for a polypropylene. The modulus and the yield stress increase with strain rate, as predicted by viscoelastic consideration and by the Eyring theory for the yielding of polymers.
Roger Reinicker, Adriano Pangelinan, Imrich Greschler, May 2000
Polytrimethylene terephthalate (PTT) is a recently commercialized polymer with both demonstrated and potential for increasing use in fibers for carpets and textiles. It is both dyeable in the conventional sense but also readily colored in the melt phase with pigments and polymer soluble dyes. This paper explores the methods used to mass color (solution dye) PTT, the pigments and dyes that can be employed, and the color and fastness results obtained with eleven selected colorants.
Many liquid mixed metal stabilizers are colloidal microemulsions of water in oil. Their shelf stability is a function of the diameter of microemulsion droplets. Microdroplets with a diameter less than 50-60 nm and low tendency to aggregate are shelf stable. A fast procedure for estimation of shelf stability of liquid stabilizers for PVC based on determination of microdroplet diameters was developed.
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).
Colin Li Pi Shan, Kyung-Jun Chu, João B.P. Soares, Alex Penlidis, May 2000
Recently, we have developed a metallocene catalyst system that can produce polyethylene and ethylene/a-olefin copolymers with tailored molecular weight and short chain branching distributions. Ethylene/?-hexene copolymers produced with this system have narrow molecular weight distributions as expected from metallocene catalysts. However, these copolymers are quite unique in that their short chain branching distributions are broad and sometimes bimodal, similar to Ziegler-Natta LLDPE. To examine the effect of these broad short chain branching distributions on the polymer properties, tensile and viscosity characteristics were measured. It was found that the tensile properties of these broad distributions could be controlled by the relative amounts of each species. In this study, the best tensile properties were achieved with a distribution that contained a large proportion of crystalline material and a small fraction of lower crystalline material. It was also found that the distribution of short chain branches can have an effect on the viscosity behaviour of these copolymers.
Polyether block amides are known as thermoplastic elastomers with excellent chemical resistance, outstanding physical properties, and easy processing. This is closely related to the type of chosen polyamide blocks and the morphology of crystalline and amorphous phases. In contrast to other multiblock thermoplastic elastomers which are forming only net points of crystallized polyamide blocks polyether block amides exhibit a spherolithic superstructure of crystallized lamellae. As a consequence there is an intrinsically reinforcing effect in the material depending on block composition which is reflected by a unique mechanical behavior which will be discussed in the paper.
Any article that is cited in another manuscript or other work is required to use the correct reference style. Below is an example of the reference style for SPE articles:
Brown, H. L. and Jones, D. H. 2016, May.
"Insert title of paper here in quotes,"
ANTEC 2016 - Indianapolis, Indiana, USA May 23-25, 2016. [On-line].
Society of Plastics Engineers
Available: www.4spe.org.
Note: if there are more than three authors you may use the first author's name and et al. EG Brown, H. L. et al.
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