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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Iinfluence of Carboxylic Acids Additives on the Flow Properties and Slip Behavior of Thermoplastic Melts
An experimental study of slippage induced in various thermoplastics in rheometers by the presence of small amount of different carboxylic acids as additives is described. Capillary and coneplate experiments are reported. A series of polymers of varying polarity including polyethylene, polypropylene, polystyrene, poly methyl methacrylate and polyamide-12 are compared. Both aliphatic fatty acids and aromatic carboxylic acids are used as additives. The aliphatic fatty acids include propionic acid, octanoic acid, decanoic acid, dodecanoic acid, tetradecanoic acid, hexadecanoic acid, octadecanoic acid, eicosanoic acid and commercial stearic acid (mixture of tetradecanoicacid, pentadecanoic acid, hexadecanoic acid, heptadecanoic acid, and octadecanoic acid). The aromatic carboxylic acids include benzoic acid, p-toluic acid, and 3-phenylpropionic acid. The greatest effects were found in polyethylene and polypropylene. Little or no effects are found with the other polymers. The most effective additives were aliphatic fatty acids. Aromatic carboxylic acids had some effectiveness. Mechanisms for this behavior are discussed.
Polymer Layers Grown from Gold and Polymer Film via Surface-Confined ATRP
Surface-confined atom transfer radical polymerization (ATRP) was tested and characterized on gold (Au) and then used to modify ethylene-acrylic acid (EAA) copolymer surfaces. For reaction from the gold surfaces, self-assembled monolayers (SAMs) consisting of alkane and acid thiols were initially prepared. This allowed for the chemistry that was developed to be transferred directly to the EAA surfaces without alteration. For both EAA and the Au-SAMs, the acid groups were used to ultimately attach the bromo-initiator. Both poly(methacrylic acid) (PMAA) and poly(methacrylamide) (PMAAm) were polymerized from the Au-SAM and EAA surfaces. The progression of the reactions and properties of the subsequent modified surfaces were studied using ER-FTIR and ATR-FTIR spectroscopies. The polymer layer that was grown gave substantial change in the polymer surface properties, but more importantly the ability to graft polymerize from polymer surfaces offers substantial potential for advanced polymer surface and device design.
Breakthrough Polymer Finishing Technology: Manufacturing Productivity and Polymer Performance Enhancements
The viscosity of polymers can be reduced at typical molding stresses and temperatures by the addition of a small amount (? 2 percent by weight) of a micron-scale solid. Although many solids may exhibit some effect on polymer viscosity, naturally occurring, non-toxic, amorphous aluminosilicate glass is the only solid that is effective over a wide range of polymer compositions and temperatures while at the same time having no demonstrable effect on nucleation of semi-crystalline polymers. Extensive research on poly(propylene), used as a representative polymer, indicates that rheologic properties described herein are dependent on particle composition, size range and concentration. The effect of the solid on the liquid polymer can thus be selected depending on the chosen particle characteristics. For most finishing applications, the practical benefit of the solid additive includes increased productivity, but may also include lower molding temperature, increased mechanical properties of the finished polymer, improved dispersion of additives, and better fit and finish of the article.
Effects of Concentration, pH, and Temperature on Ink Removal from Printed High Density Polyethylene Sheets by Alkyl-Trimethylammonium Bromides
Ink removal from printed high density polyethylene surface was performed using three different cationic surfactants: dodecyl-, tetradecyl-, and cetyltrimethylammonium bromide (i.e., DTAB, TTAB, and CTAB, respectively). These surfactants are chemically different in the number of carbon atoms of the alkyl tail group (i.e., 12, 14, and 16, respectively, for DTAB, TTAB, and CTAB). It was found that increasing the carbon chain length of cationic surfactant increased the deinking efficiency. It was also found that an increase in pH level and concentration of surfactant helped promote the deinking efficiency, while an increase in the solution temperature from 30 to 45°C either increased or decreased the ink removal.
Melt Processing of Thermally Unstable Polymers Plasticized with CO2
The effects of plasticizing acrylic copolymers, in particular a 65% (molar) polyacrylonitrile/ 25% (molar) methyl acrylate/ 10% rubber (PAN/MA/rubber) copolymer, with carbon dioxide (CO2) are studied. Previous work included differential scanning calorimetry (DSC), used to evaluate the resulting shift in the glass transition temperature (Tg) following plasticization, and pressurized capillary rheometry to evaluate the melt rheology prior to and after plasticization. A series of capillaries is used to evaluate the entry pressure effects and to observe the pressure effects of CO2 on the copolymer. The plasticizing effects of CO2 on the AN copolymer are observed to have a nonlinear pressure dependence, possibly indicating a higher plasticizing effect at higher pressures.
Controlling the Performance and Rate of Degradation of Polylactide Copolymers
An important factor in the commercial development of biodegradable polymers is the ability to control the rate of degradation. Ideally, the polymer should not degrade during functional use, but degrade quite rapidly when discarded. This paper discusses various aspects associated with the control of the rate of degradation of polylactide copolymers; both from the perspective of stabilizing the polymer during processing and product use, and subsequently accelerating the rate of degradation after disposal. Of particular interest are the influences of molecular weight, crystallinity, end-capping and plasticization.
Formulation and Processing of Natural Fibre-Reinforced Polymer Composites
The microstructure, thermal and mechanical properties of a range of natural fibres, derived from arable crops, are examined with a view to using these as reinforcing additives for thermoplastics. The fibres were characterized prior to incorporation into the polymer using a range of techniques, including SEM, image analysis and thermogravimetric analysis, at room and elevated temperatures. The thermal and mechanical properties obtained are discussed in relation to the measured composition and structural form of the fibres. Particular emphasis is given to determining the nature and consequences of fibre damage induced during meltprocessing operations, fibre orientation occurring in mouldings, and possible interfacial adhesion between the matrix and fibres, with and without the use of bonding agents. Novel processing techniques, including integrated compounding/extrusion and direct compounding injection moulding processing technologies, are considered as means for improving the quality of processed parts and the economics of manufacture.
Use of Recycled Polymer Modified Asphalt Binder in Asphalt Concrete Pavements
Since polymer modified asphalt cements (PMAC) have been employed for a decade, the lifetime and wear on of some of these roadbeds are reaching a stage where resurfacing will be necessary. This paper considers the potential problems associated with recycling of polymer modified asphalt cements, PMAC's, in particular blending aged PMAC with tank PMAC. A standard PMAC was selected and characterized using typical asphalt binder qualification techniques, i.e., the Superpave Strategic Highway Research Protocol. Procedures were developed to separate the PMAC into its asphalt resin and polymer additive components as well as to characterize the relative concentrations of each component. Infrared and chromatographic techniques were used to identify changes in the components as a result of aging. The impact of the extraction and recovery process on binder properties has been ascertained and found to be minimal.The standard PMAC was aged under accelerated aging conditions in a Pressure Aging Vessel (PAV) that produced a material equivalent to 5-8 years in the field. The aged PMAC was then reanalyzed both chemically and rheologically and all changes in its properties due to aging were noted. Finally blends of the PAV aged PMAC with fresh PMAC, as well as blends where the PAV aged PMAC was replaced with road-aged binder, were prepared and analyzed. Our initial results indicate that aged PMAC can be blended successfully with fresh PMAC. Thus we anticipate that resurfacing of aging PMAC roadbeds can proceed, but further tests will be required to establish the precise conditions necessary to conduct this process.
Reactive Process for Recycling of Cellular Phone Housing
The front cover of cellular phone housing collected was grounded to be as the same size as the original particles before use, using knife mill. The unprinted glass fiber reinforced epoxy circuit boards were size reduced and pulverized using knife mill and hammer mill. The separated epoxy powder and glycidyl methacrylate (GMA) were added as the additive and the reactive species for reactive process using the batch mixer and the twin screw extruder. Izod impact strength at various temperatures, tensile test, particle size distribution analyses for the ground circuit board, SEM on the fracture surface, and dynamic mechanical spectroscopy were performed to characterize the reactive alloys and mixtures compounded by the batch mixer and the twin screw extruder.
Low Temperature Durable of Copolyester-Poycaprolactone- Hydroxypropylcellulose Biodegradable Blends
Pittsburg State University has worked on the development of biodegradable blends for low temperature, durable applications in bull castration clips for use in the farm industry. These clips are biocompatible, to ensure that meat is not contaminated. At the same time they also exhibit biodegradability and strength in temperatures as low as –20 °C; temperatures that can be experienced in the North American farm belt. The blends contained the following materials, Eastar Bio Copolymer, Polycaprolactone, Polyethylene glycol (Carbowax), Hydroxypropylcellulose (Klucel), Cornstarch, and Titanium Dioxide. Table 1 shows the ingredients of each blend. In vitro results show degradation of the samples from 5% to over 25% of its’ original mass over a 28- day period. Differential Scanning Calorimetry results showed the Tg of the blends reaching –24.15 °C, well below the targeted value of –20 °C.
A Life Cycle Value Analysis (LCVA) Approach to the Materials Selection for the Signal Detector Control Head Unit (SDCHU) Housing
A prior advanced materials selection process via the digital logic approach (DLA) yielded five materials as suitable choices for the housing of the Signal Detector Control Head Unit (SDCHU), with ABS (acrylonitrile-butadiene-styrene) terpolymer and aluminum 1100 as the top two choices. In an effort to study the long term perspective, durability and environmental impact of the SDCHU, a life cycle value analysis (LCVA) was performed on the SDCHU with ABS as the housing material and then with aluminum 1100 as the housing material. The LCVA results indicate that ABS is the choice material in seven of the eight impact categories studied such as costs, energy usage, conventional pollutants, green house gases released, fuels used, ores used, hazardous waste generated and water used. Normalized environmental impact data show that the 5.6% increase in hazardous waste is offset by the 8 - 52% reduction in the other seven categories due to ABS use in the SDCHU housing.
Poly(Lactide); Moisture Sorption Characteristics and Storage Consequences
The attractiveness of high molecular mass poly(lactide), PLA, as a packaging material has increased in the last few years due to its natural biodegradability. PLA is a thermoplastic and compostable polymer produced from annually renewable resources, which can be totally degraded in aerobic or anaerobic environments in six months to five years. As PLA is now potentially available for use as food packaging polymeric material, one of the main concerns is to evaluate its durability with respect to the product shelf life. Since moisture sorption isotherms of polymeric materials are one of the controlling factors in the preservation of moisture-sensitive products, the aim of this research was to study the moisture-sorption characteristics of two poly(lactide) polymers at 5, 23, and 40°C for water activities (aw) from 0.1 to 0.9 as a function of short time storage. The PLA films were stored for one month at the same temperatures, and the glass transition and melting temperatures were monitored by Differential Scanning Calorimetry every week. It was found that PLA films absorb very low amounts of water, and the variation of the glass transition temperature as a function of time was statistically significant (P<0.05).
Development of an ISO Standard for Determining Anisotropic Properties of Glass-Filled Thermoplastics
During injection molding of glass-filled thermoplastics, the flow of the molten polymer causes preferential orientation of the fibers, which leads to the development of anisotropic mechanical properties across a part. These anisotropic properties pose a significant challenge to part designers, who normally assume isotropic properties measured on tensile bar samples. This paper describes the background information and test data used to prepare an ISO standard plaque (ISO 294-5: 2001) for measuring anisotropic properties and developing a relevant materials property database for plastic part design.
How to Present Expert Witness to Court
Lawyers and judges have, most of the time, little understanding about the mechanical, chemical and physical behavior of plastics. A selection of legal cases will be presented and it will be emphasized that presentation is sometimes rather an art than a science. This is illustrated by three examples of legal cases.1. Water storage tanks, consisting of an outer and an inner stainless steel tanks with insulation between the tanks. In order to prevent freezing of the wastewater a heating mat is adhered using silicon kit to the outside of the inner tank. PE tanks were ordered to substitute the expensive stainless steel tanks. The heating mats became overheated because of the poor adhesion to PE. It is rather easy to convince court that the bonding between silicon kit and PE is absent and that this is the reason that containers for silicon kit are of PE.2. Scratches on textured plastic panels. A supplier promised to manufacture panels of high surface quality, but was not able to meet the requirements and painted the panels. The supplier billed the customer for $ 400 000 and in court this claim was rejected on the basis of strict contractual liability. The lawyers even did not want to have the technical explanation, why the scratched occurred, in my failure report.3. Fatigue of flexible covers for cupboards made of ABS. The manufacturer of the cupboards covers specified ABS with a rubber content (polybutadiene) of 40 % to avoid fatigue of the covers that were subjected to bending during opening and closing of the cupboards. The covers often did to satisfy the surface gloss requirements and the manufacturer of the covers proposed ABS and PS with a lower polybutadiene content. These covers met the surface gloss requirements, but failed in surface due to the low polybutadiene content. This resulted in a loss of confidence of the Cupboard Company and almost resulted in a bankruptcy. The final solution was to use ABS from another supplier and stricter quality control.
Deformational Behavior of a Plastic Guidance Strip
Pistons and cylinders in hydraulically systems are separated using plastic guidance strips, positioned in grooves of the piston. The total compression and wear of the strip under transversal loading is critical for avoid metallic contact between pistons and cylinders. If the compression of the strip is larger than expected, severe damage occurs and, even in Europe, high liability claims are likely.The paper is about a design in which the compression of the strip was critical. The designer relied on the stress-deflection curves in the brochure of the manufacturer of plastic guidance strips. The designer was convinced to be on the safe side, but in practice metallic contact occurred.The stress-deflection curve of the guidance strip has been measured again and the difference with the values in the brochure was significant. Interesting, from the engineering standpoint, was the ambiguity of some of the data. The assumptions made by the designer of the hydraulic system and the manufacturer of the strips has been tested using FEM calculations.The predictions have been made with the FEM-program MSC/MARC using the contact option. The predictions have been compared with results of full-scale experiments.
Applications of Root Cause Analysis in Polymers Failure Investigations
In a previous publication1, I showed that root cause analysis was an effective method in revealing the true cause(s) of polymer failures and in proposing the corrective actions needed to avoid future failures. In this current work, I will discuss two polymer failure cases that explain the basic steps of root cause analysis. In these cases, I will talk about the effect of the four common factors that influence failure: part design, material choice, processing factors, and end-use conditions. An explanation of each case will be offered. Subsequently, the suggestion of the probable failure cause(s) and the exploration of the most likely cause will be presented. Finally, some corrective actions will be recommended.
Explosion of an ABS Pressurised Air Line
A compressed air line exploded suddenly and caused extensive damage to property, fortunately without casualties. The air line was used as part of a plant for annealing glass, and so was pressurised regularly up to about 10 bar. When the pressure was released, a blast of cold air was directed over the hot glass surfaces. Most of the pipework for the system was made of ABS pipe and solvent-welded fittings. The explosion was caused by catastrophic growth of an internal axial crack in one of the pipes of the system. The inside surface of the pipe was covered with deep cracks, and the first investigators concluded that the cracks had been caused by fatigue. However, a separate investigation of the remains indicated that traces of fluid from the oil of the air pump compressor had created environmental stress cracks.
Fracture Initiation in Polybutylene Tubing in Potable Water Applications
The fracture initiation in polybutylene (PB) tubing is usually observed in the form of a microcrack network within a layer of degraded PB at the inner surface of the tubing exposed to flowing water. Chemical degradation of PB is manifested in a reduction of molecular weight, increase of crystallinity and density of the material, a subtle increase in yield strength, and a dramatic reduction in toughness. An increase in material density, i.e., shrinkage of the degraded inner layer of the tubing constrained by the outer layer of unchanged material results in a buildup of tensile stress due to an increasing incompatibility between the inner and outer layers of the PB tubing. These stresses combined with preexisting manufacturing and service stresses, as well as reduction of toughness, result in fracture initiation. A mathematical model of the foregoing process is presented in this paper. An equation for determination of the critical level of degradation at the onset of fracture is derived. The critical level of degradation leading to fracture depends on the rates of toughness deterioration and buildup of the degradation related stresses as well as on manufacturing and service stresses. A method for the evaluation of the time interval prior to fracture initiation is also outlined.
Reliability Analysis of PB Tubing in Water Distribution Application
A number of water utilities in various states of USA have reported a persistent premature failure of polybutylene (PB) tubing in water distribution system. A methodology of reliability analysis of PB tubing in potable water distribution application and probabilistic model for predictions of future leaks are presented in this paper. The predictive power of the proposed methodology is validated by comparison of predicted number of failures in Harford County Water District, Maryland between 1996 and 2001 with actual events reported by the District in 2002. The proposed methodology also accounts for the effect of preventive replacement program on the reduction of emergence replacements and thus allows a rational planning of replacements. The needs to understand the failure mechanisms for proper interpretation of both descriptive and inferential statistics are also discussed.
Premature Fracture of Noryl Transformer Plugs
Small transformer plugs are widely used for consumer electrical and electronic products, designed to be fitted to mains electricity sockets by the user. Problems occurred when plugs injection moulded in Noryl started cracking at or near the weld zone on first use, exposing the user to danger. A quality audit showed that the base and cover had been moulded in mainland China in two specific weeks of 1999. Although records for that period were not available, those from adjacent batches showed that low tool temperatures (ca 55°C) had been used for the base moulding , which also showed the greatest incidence of brittle cracking. An alternative theory by a Japanese investigator that the material was faulty could not be sustained by EDAX analysis.
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