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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Shelf Life Failure Prediction Considerations for Irradiated Polypropylene Medical Devices
In a standard method for assessing polypropylene syringe durability, the maximum bend angle before failure was used as a measure of the device ductility. Since the ductility of polypropylene is heavily dependent on deformation rate, choosing a realistic testing rate is critical to predict its shelf life accurately. In addition, irradiated polypropylenes undergo degradation when free radicals deposited by the radiation react with atmospheric oxygen to form a brittle surface layer. This brittle layer can create sharp notches and magnify the local strain rates causing the entire device to fail. Therefore, it is important to incorporate the effect of strain rate and degraded surface in the shelf life prediction of the polypropylene devices. For thin film applications, we found that oxidative induction time (OIT) test combined with oven testing can be used to predict its shelf life quite satisfactorily.
Radiation Resistance of Multilayer Films by Instrumented Impact Testing
Olefinic multi-layer films are becoming increasingly cost-effective in the medical industry for a wide variety of applications. And terminal sterilization by gamma or electron beam is also becoming wide spread due to its economy and simplicity. However, during the irradiation process, much of the antioxidant in the polymer can be depleted, and in the case of high glass transition (Tg) polymers like polypropylene, could lead to brittleness during the shelf life storage of the product. We have utilized an instrumented impact test where film samples' high strain rate ductility and toughness can be quantified at deep subambient temperatures. The test system was constructed using the Lab-View( instrument interface system with an personal computer as the controller. Temperature control, velocity sensing and high speed strain gage data acquisition were all handled automatically. After the impact event, data presentation, energy integration and file archiving were built into the system. Using this system, we quantified the post irradiation embrittlement behavior of a multilayer film and developed an effective impact modifier system which insured ductility retention long after irradiation at high doses.
Development of Poly(Phenylene Sulfide)/Nylon66/Glass Fiber Composites with High Elongation and Impact Strength Using EGMA
In this study, the toughenning effect of Nylon66 on the PPS/glass fiber composite at various Nylon66 contents and testing temperatures was analyzed using tensile and notched Izod impact test. Also the corresponding fracture surface morphology was observed. First, compatibility of PPS with Nylon66 was examined. It was found that compatibility was low when Nylon66 was a dispersed phase. However, when PPS was a dispersed phase, increased compatibility could be observed. This tendency was similarly observed when glass fiber was added, and the overall effect was an increase of mechanical strength in terms of absolute values. Thus, when Nylon66 was a dispersed phase(minor component), negative deviation from the rule of mixtures relationship was found. In order to improve these deficiencies, compatibilizer EGMA was used. Optimum EGMA content which can improve the strain at break and impact strength was found to be between 3~5wt%.
World Volume Polymer Markets Slow
This marketing paper, like the similar one last year, is being written in November 1998 for presentation in six months. During that time, a lot can happen. Therefore, this paper is being written for the SPE ANTEC preprint book, but the actual paper, come May 1999, may be significantly updated, as it was in 1998. In the next few pages, this paper will discuss some of the major factors affecting the world volume polymer industry in 1999. The major issues to be discussed include: 1. The Supply and demand for the Polymers 2. Industry restructuring 3. Globalization 4. New technology developments Overriding all of these is profitability. As of October 1998, the margins polymer producers are achieving are relatively low or non existent. Margin is defined as the difference between the selling price of the polymer and cost of the monomer. This is the amount of money the resin producer has available to make the resin, deliver it to the fabricator, pay all manufacturing costs including catalysts and additives, pay for all overheads including sales expenses, advertizing, R&D, corporate management and taxes, pay interest on all loans and hopefully return something to the stockholders. In Oct. 1998, margins for polypropylene, PVC and LLDPE producers are at very low levels. The lowest levels of this decade! To correct this situation, either monomer prices will have to continue to decline or the polymer prices will have to increase. Or the polymer producer will have to reduce costs as outlined above or by possibly combining the business with another producer or shut down the business.
The Rotational Molding of Glass Fibre Reinforced Polyethylene
The rotational molding industry has a current growth rate of 15% per annum. It is progressing rapidly from a method for manufacturing toys to a process that is considered seriously by the designer for complex load bearing articles coupled with improved mechanical properties. The main obstacle in the path to a greater growth rate lies in its dependence on polyethylene (PE) to meet the material property demands of the end user. Unfortunately PE is at the low end of the strength and stiffness bands for plastics. Increasing the thickness of products made from PE will increase the mechanical stiffness but at an additional cost which may be prohibitive. As a result, rotationally molded PE products are currently restricted to the less demanding applications. This research gives a detailed investigation into a means of reinforcing polyethylene with glass fibre and fillers. Under the best conditions, tensile strength of virgin PE will be shown to have increased by 54% and flexural modulus by 40% for a glass loading of 25% by weight.
Manufacturing Close Tolerance Medical Tubing
Medical tubing producers and those interested in becoming producers in today's market are faced with guarantying product reliability, material consistency, dimensional tolerance, and overall process validation. This paper will: (Refer to Item #1) • Give a brief history of medical tubing. • Describe some of the types of tubing in demand. • Outline the manufacturing process, including Bump, Bubble or tapered tubing. • Give an overall view of the extrusion line used in the manufacturing process. • Highlight the important features in the individual components of the system. • Review the various types of controls available to insure consistency in day to day operation.
Production of Electrically Conducting Plastics at Reduced Carbon Black Concentrations by Three-Dimensional Chaotic Mixing
Multitudinous, continuos structures were produced in polystyrene melts from initially coarse bodies of conducting carbon black particles under three-dimensional chaotic mixing conditions. At a larger scale, such structures formed extended networks, which were captured by solidification, and rendered the composite materials electrically conducting. Micrographs showed complex structures exhibiting patterns characteristic of chaos. Electrical conductivity was achieved at carbon black loadings significantly lower than by common mixing methods and still lower than reported by the authors recently for two-dimensional chaotic mixing.
Crystallization and Microstructure of Ziegler-Natta and Metallocene Based Isotactic Polypropylenes: Simulation and Experiment
The quiescent crystallization and microstructure of Ziegler-Natta and metallocene based isotactic polypropylenes (i-PP's) of comparable molecular weights were studied. This allowed to elucidate the differences in their crystallization behavior. In particular, the isothermal and nonisothermal rate of crystallization, induction time, and spherulite growth rate were measured. These results were used to obtain the parameters for a crystallization model. The i-PP's slabs were quenched and the gapwise spherulite size distribution in the quenched slabs was measured. Simulations of the temperature field and microstructure in slabs during quenching were performed. Simulation results were found to be in good agreement with the experimental data.
Yield Maximization in Injection Molding by the Virtual Search Method
The Virtual Search Method (VSM) is an efficient method of tuning for injection molding. The salient feature of this method is its utilization of an input-output (I-O) model as a virtual process to search for the process inputs. VSM uses learning to update the I-O model after each tuning iteration so as to improve its representation of the process. The VSM has already been tested experimentally for regulation of part dimensional and qualitative attributes. This paper focuses on extension of VSM to improving the quality of the part, where it can be used for maximization of production yield and molded part consistency. VSM's performance with two I-O models is investigated using production of optical media with six input parameters and four quality attributes.
Effects of Complexity on Tooling Cost and Time-To-Market of Plastic Injection Molded Parts
The injection molding process is increasingly being used in the manufacture of complex net shaped parts. Designers are taking advantage of improvements in the process and the development of engineering materials with superior properties by consolidating multiple parts and functions into single complex parts. However, the effects of complexity on tooling and manufacturing costs as well as time-to-market of injection molded parts are still largely undetermined. This paper proposes the use of the number of dimensions that are used in detailing a part as a measure of its complexity. The metric was tested with empirical data and found to correlate well with mold cost and to a lesser extent with tooling lead-time.
Shrinkage Study of Thermoformed Parts
Most thermoforming product development processes rely on costly and time consuming forming trials to determine adequacy of the mold and process. This paper describes the predictive capabilities, which were developed from experimental, statistical and analytical methods in order to provide estimates of shrinkage for various process conditions. On the basis of theoretical analysis, additional transfer functions have been developed to predict shrinkage for different sets of materials, process conditions, and mold geometry. A turnkey finite element analysis system utilizing commercial software is being developed and validated for commercial applications for shrinkage prediction.
Mixing Analysis of a Reactive Extrusion Process in a Co-Rotating Twin-Screw Extruder Screw Element Channel
Simulations of steady-state non-isothermal non-Newtonian reactive flow of molten polypropylene in a channel of a forward conveying screw element from a self-wiping co-rotating twin-screw extruder, performed using the commercial finite element simulation package FIDAP, are described. The reaction is peroxide-initiated controlled degradation of polypropylene. In the simulations, the screw speed, entering peroxide distribution, and pressure-to-drag flow ratio in the channel are all varied, and a mixing analysis of the flows is performed based on computed values of the flow efficiency parameter.
Utilization of the Derivatives of Fullerene (C60) Modified Phenolic Resin to Prepare Carbon/Carbon Composites (I)
The improvement on the toughness of the cured phenolic resin modified with linear PU and star C60-PU was investigated. The modified phenolic resins were utilized to prepare carbon/carbon composites. Impact strength of cured resin specimen contains 3phr linear PU is 27 % higher than that of neat phenolic resin while the impact strength of specimen contains 3phr C60-PU is 57 % higher than that of neat phenolic resin. The flexural strength of carbon/carbon composite contains 3phr linear PU is 25 % lower than that of composite contains only neat phenolic resin. The flexural strength of carbon/carbon composite contains 3phr C60-PU is 40% higher than that of composite contains only neat phenolic resin.
Syndiotactic Polystyrene Can Help Solve the 3-Piece Material Selection Puzzle: Properties, Processing, Cost
For injection molding, material selection involves three factors: properties, processing, and cost. Summing the factors determines part cost and profitability. Material properties are prerequisite to application requirements. Processing is prerequisite to part design. Cost vs. the marketable price of the application determines if and how the part should be made. A material must meet the prerequisite performance for the application but it does not need to have the highest available properties. Processing conditions, particularly cycle time, directly affect cost. Price and the forgotten property, specific gravity, directly go to the bottom line. Graphs show costs of semi-crystalline thermoplastics vs. properties, processing, and part cost. New materials like syndiotactic polystyrene provide cost effective solutions vs. established semi-crystalline polymers.
Effects of Injection Parameters on Fiber Attrition and Mechanical Properties of Polystyrene Molded Parts
Fiber degradation of injection molded fiber reinforced polystyrene has been analyzed using a statistical approach. Results showed that fiber concentration as well as injection speed are responsible for the onset of fiber degradation. The same experimental design has been used to evaluate the effects of injection processing parameters on mechanical properties of molded parts. Results have been used to generate a statistical model to predict fiber degradation and mechanical properties using the most significant parameters identified in the statistical analysis. The statistical approach has proven to be satisfactory for the analysis of fiber attrition during the injection molding process.
Fractal Description of Interlaminar Contact Development during Thermoplastic Composites Processing
Fabrication of layered thermoplastics and thermoplastic-matrix composites using processes such as tow placement, tape laying, and resistance welding, is fundamentally based on the principle of fusion bonding, which involves applying heat and pressure to contacting thermoplastic surfaces. One of the important processing steps-intimate contact-is considered in this paper. Interlaminar intimate contact development is a strong function of thermoplastic surface geometry. Profilometric measurements of thermoplastic prepreg tows show that surface roughness features can be found at several length scales, which implies that the surfaces have a fractal structure. In this paper, principles of fractal geometry are used to describe prepreg surfaces. Based on this description, an axisymmetric squeeze flow model is developed to relate degree of intimate contact to the process parameters-pressure, temperature, and time-and the fractal parameters of the surface. The model development and comparisons with available experimental data are presented and discussed in this paper.
Plastics in fuel Cell Applications: An In-Lab Developed and Fabricated Molten Carbonate Fuel Cell (MXFC) Electrolyte Matrix Support with Polyolefin-Based Binders
A low pressure compression molding, in-lab fabricating process has been used to produce crack-free, Molten Carbonate Fuel Cell (MCFC) electrolyte matrix support that are prospectively conductive and have volume resistivities much lower than those of standard insulative materials (1013 - 1016 Ohm-m). The volume resistivities of the in-lab produced MCFC electrolyte matrix support are expected to be much lower at the system's 650°C operating temperature than their currently room temperature measured resistivities (103 - 106 Ohm-m).
Injection Molding of Thermoplastic Composites Using Novel Mixing Nozzles
Injection molding of PET/PE, one of immiscible thermoplastic composites, was carried out with original novel mixing nozzles equipped with torpedoes. An ability of the nozzles to promote plasticizing and mixing of dry-blended PET/PE to achieve high performance as same as a melt mixed composite was investigated. Mixing of dry-blended PET/PE was promoted by high shear effect of the mixing nozzle with a torpedo which allowed homogeneous and fine dispersion. The dispersion structure was equal to that made using a twin-screw extruder with high ability to knead materials. When a torpedo which has barriers and grooves was used, a fine dispersion structure was also obtained by its effect of distribution and collision of materials.
In Situ Polymerization of Conducting Composite Films and Some Characterizations
Electrically conducting composite films were prepared by a vapor phase in situ polymerization of pyrrole in the methyl cellulose film containing a copper(II) perchlorate. Methylcellulose had a high affinity to pyrrole and was used as a matrix polymer. Conducting polypyrrole was embedded in the methylcellulose film forming a conducting network and the conductivity of the composite films ranged 10-1 to 10-7 S/cm. The conductivities and mechanical properties of conducting composite films were depentent showed on the concentration of oxidant and polymerization time. In situ polymerization of pyrrole was observed in the matrix polymer and confirmed by UV-vis spectra and FT-IR spectra. From the results of the thermogravimetric analysis, the chemical oxidative polymerization of pyrrole in the matrix polymers did not give any negative effect on the thermal stability of the composite films. Dynamic mechanical analysis suggested a certain degree of miscibility of the polymeric components in the composites.
Selection of Silicone Sealants for Heavy Truck and Off-Road Vehicle Applications
The unique sealing requirements encountered in Heavy Truck and Off-Road Vehicle applications warranted the investigation of silicone sealants for this marketplace. The candidate sealants were subjected to a selection protocol based on lap shear strength as a function of cure time and after immersion in water, engine wash fluid, and common automotive fluids. An acid cure silicone did not adhere well to chromate plated steel, and its adhesion to brass deteriorated after fluid immersions. A neutral cure silicone adhered well on any of the substrates, and retained adhesion after fluid immersions. Neutral cure materials were recognized as the best choice for future product performance testing.
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