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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Polyamides are susceptible to attack by environmental pollutants. The surface layer is degraded and the development of a critical thickness of this layer results in a catastrophic loss of mechanical properties. In this work nylon was exposed to nitrogen oxides and the fracture strength was measured. After a period of no change the fracture strength decreased dramatically. Exposed samples were microtomed and the molecular weight distribution of nylon was determined, as a function of depth from the surface, by Gel Permeation Chromatography (GPC). A critical depth for degradation was established beyond which the specimen exhibited unacceptably low fracture strength.
Patrick B. Smith, Walter C. Buzanowski, Judy J. Gunderson, Duane B. Priddy, Lance Pfenninger, May 2002
The phase partitioning of additives in polymer blends has a large impact on the performance of the blend. Since solubility characteristics and processing of the blends influences partitioning, it is necessary to be able to quantify the level of the additive present in each phase. An NMR method to quantify this partitioning has been developed and is based on the fact that the rubber phase and molecules dissolved therein, can be easily distinguished due to this phase’s enhanced motional characteristics. Examples will be presented for the quantification of phase partitioning within rubber modified styrenic materials.
Eliton S. de Medeiros, José A.M. Agnelli, Kuruvilla Joseph, Laura H. de Carvalho, Luiz H.C. Mattoso, May 2002
The mechanical and dynamic-mechanical properties of novolac type phenolic composite reinforced with jute-cotton hybrid woven fabric were investigated as a function of fiber orientation and type. Scanning electron microscopy (SEM) was carried out to investigate the fiber-matrix adhesion. Results showed that the composite properties are strongly influenced by the test direction and yarns characteristics. The highest tensile, flexural and impact strengths and moduli (Young’s, flexural and storage) were found along the jute yarns direction and decreased with increasing test angle. Nevertheless, failure occurred in a catastrophic manner. Along the cotton yarns direction the composite exhibited a controlled failure mode. Jute fiber exhibited a better interaction with the matrix than cotton; the former has a higher irregular surface due to its multicellular nature, which promotes a mechanical adhesion at the interface. The combination of jute/cotton properties in this composite is suitable for lightweight structural applications, this is, jute promotes a higher reinforcing effect while cotton fiber avoid catastrophic failure.
The deposition of polydimethylsiloxane (PDMS) on hair for prototype shampoos was studied against competitive products as benchmarks. SIMS reveals uniform coverage of PDMS on hair for both the prototypes and the benchmarks. XPS and SIMS results show that the benchmarks leave substantially higher amount of PDMS on hair while the prototypes deposit 1-2 monolayers. The high PDMS deposition could be related to the consumer perception of smooth feeling, manageability and good rinsability, and could also be related to high conditioner build-up. The results provide insight towards an understanding of structure-performance relationship of hair care products, which helps deliver consumer benefits in a tailored manner.
The performance of a wide range of elastomers exposed to fuel and hydraulic fluid at elevated temperatures was measured. The stability of the elastomers was determined by the degree of mass absorption, volume swell, change in hardness, and change in tensile properties. Other important parameters monitored included changes in glass transition temperature and the quantity of material extracted from the elastomer by the heated test fluids. Performance was measured after 3 and 28 days of immersion in the test fluids at either 107ºC or 135ºC. The classes of materials examined included PP/EPDM thermoplastic elastomers, thermoplastic and thermosetting polyurethane elastomers, nitrile rubbers and hydrogenated nitrile rubbers, epichlorohydrin elastomers, and several formulations of fluoroelastomers.
J. Couch, M. Toro, K. Oliphant, P. Vibien, May 2002
A test methodology to determine the effectiveness of Ultra-Violet Light (UV) stabilization on the oxidative stability of piping materials is examined. Chlorine Resistance (CR) testing is used to determine the impact of accelerated UV exposure on the oxidative resistance of crosslinked polyethylene (PEX) pipe. Following accelerated UV exposure, samples are tested to failure under accelerated test conditions designed to simulate chlorinated potable water end use environments. CR testing in conjunction with UV exposure is shown to be a sensitive method for the evaluation of the effectiveness of UV stabilization on the oxidative stability of PEX pipe. For the particular material examined, it is demonstrated that excellent retention of oxidative stability can be achieved when suitable UV protection is employed.
A.S. Bakharev, R.G. Speight, P.A. Brincat, May 2002
This paper describes an automated closed-loop control system that compensates for plastic viscosity variations by directly controlling the machine parameters of an injection molding machine. Viscosity is evaluated using a primary injection pressure integral, and compensated for by changing the temperature profile settings of injection molding machine. The shrinkage changes due to the melt temperature changing are compensated for by adjusting the holding pressure. The paper discusses the theoretical basis of the algorithm and presents experimental results on testing the algorithm.
Amol V. Janorkar, Douglas E. Hirt, Jeffrey J. Wooster, May 2002
Erucamide is incorporated into polymer films to reduce their coefficient of friction (COF). Such a reduction in COF is important in packaging lines where the performance of the film in contact with rollers can be governed by the frictional characteristics of the film. This research explores the COF behavior of multilayer films with either POP or LLDPE as the skin layer. Film-on-metal COF testing was performed repetitively with the same piece of film to investigate the extent of COF change with the number of runs. Film-on-film studies were also performed for comparison with the film-on-metal tests. Complementary analysis was conducted with atomic force microscopy (AFM) to investigate whether erucamide was being removed from the film surface or simply being smeared over the surface.
Rigid polyvinyl chloride (PVC) was co-injected with glass fiber reinforced PVC (GFR-PVC), polypropylene (PP), acrylonitrile-butadiene-styrene copolymer (ABS), and polycarbonate (PC) using the Mono-sandwich co-injection process. Up to three through-thickness skin-core morphologies were observed along the length of the sample. Near the gate, the core was always a single, continuous layer. In some cases, the core diverged into multiple or discontinuous layers. Further from the gate, flow of the core ceased, leaving a skin-only region. The skin and core layers were more uniformly distributed through the test plaque when injection speed was low. Adhesion between PVC and PP was poor. Skin and core layers delaminated and mechanical properties were poor. PVC adhered well to GFR-PVC, ABS and PC. No layer delamination occurred and mechanical properties were intermediate between those of the skin and core components alone. Dropped dart impact energy was controlled more by the skin layer than the core. In rigid PVC/GFR-PVC co-injected samples, impact energy was 2.5 times greater when GFR-PVC was the core than when GFR-PVC was the skin.
D. Ait Messaoud, B. Sanschagrin, A. Derdouri, May 2002
The co-injection molding process involve injection of two materials sequentially to form a multilayer product with a skin and core structure. Dumbbell test specimens were molded using a 150 ton Engel co-injection machine. The effect of injection speed and skin-core ratio on material distribution was first studied. The mechanical properties of different combinations using virgin polypropylene and polypropylene reinforced with 10, 20, 30 and 40 % (by weight) short glass fiber were measured.
Cold slug wells are used on nearly all cold runner molds to prevent potential problems caused by cold slugs that are introduced to the runner from the nozzle tip. However, they are often used without a full understanding of what they do, how they work, were they need to be placed, and how large they must be. This paper quantifies the effectiveness of cold-slug wells and investigates design variations. The effects of location and size are examined to determine the relevance of each. By better understanding the use of cold slug wells, a molder can design and use them more successfully to help minimize related problems.
Gas-assist injection molding was discovered in Germany 30 years ago. Even though this technology has demonstrated significant value, a relatively small number of components are manufactured utilizing this process.Since the basic technology is straightforward, why has the acceptance of gas-assist injection molding been so limited? A number of factors have played a role, including litigation, initial licensing approaches and the unfamiliarity of designer with this process.This presentation will examine a number of the key decisions made by the suppliers of this technology as well as the OEM’s and molders that impacted the acceptance and utilization and their implication on the commercialization of gas-assist injection molding.
The Compact Slide Action Mold Technology (CSAM) has been custom designed for tamper evident closure molds for carbonated and non-carbonated beverage bottle closures, as well as mineral water bottle closures.Existing mechanisms for opening and closing slides in a slide action mold typically include angled horn pins or delta cams mounted to the cavity plate and slide retainers to retain slides in an open position.The new compact slide action mechanism for lateral movement of slides has been developed with the use of an air driven rack and pinion arrangement. This paper discusses some of the common problems associated with the conventional mechanism and how the new mechanism overcomes these problems.
H. Potente, G. Fiegler, F. Becker, J. Korte, May 2002
Laser transmission welding of polymers is regarded as a promising alternative in a range of industrial applications by virtue of its characteristic properties. The new variant of laser transmission welding – quasi-simultaneous welding – can be seen as a pioneering technology offering advantages such as precise local and contact-free heating, small heat affected zone, negligible warpage, high flexibility, compensation of part tolerances, high achievable weld strengths, etc.Initial systematical investigations were carried out varying the parameters: laser beam intensity, scanning velocity, joining displacement, pigment content and joining pressure. Their influence on weld strength and welding time was recorded. A T-joint was used for welding PEEK, while both T-joints and butt joints were used for the material PC. Optimum process parameters were determined for each material.
Celso L. Lotti, Elisângela Corradini, Eliton S. de Medeiros, Luiz H.C. Mattoso, May 2002
In this work, corn starches with 21% and 1 % of amylose contents, processed in the presence of 30% (w/w) of glycerol (plasticizer), were characterized by X-ray diffraction, Dynamical Mechanical Thermal Analysis (DMTA), Tensile test and Scanning Electron Microscopy (SEM). The results showed differences in the crystalline structure and mechanical properties of the starches after processing. The 21 % amylose content starch showed fragile behavior and higher tensile at rupture than 1% amylose content starch, which showed higher elongation at break and ductile behavior.
Three cavity pressure sensor configurations were used to compare data from direct and indirect, piezoelectric and strain gage sensors. The indirect button style sensors tended to read slightly lower peaks than direct flush mount sensors, and data decayed slightly later. Also, the piezoelectric sensors tended to respond approximately 5 ms faster than the strain gage sensors. However, data from all sensor types correlated very well with one another. For all practical purposes, there is no distinguishable difference in the data utility between one sensor type and another.
PP product design and application possibilities have expanded significantly with developments in metallocene catalysis. With the large number of structural and compositional differences these resins bring to the plastics consumer, processing effects require an improved scientific understanding. A variety of isotactic and syndiotactic PP’s are described in detail regarding their tensile and (specifically) yielding behaviors, useful to predict performance characteristics, in property evaluations and as an aid for orientation processing in film and fiber applications.
Guillermo PalmerMartin, Nicole Raymonde Demarquette, May 2002
Interfacial tension between molten polymers is a key factor that helps predicting the morphology of polymer blends. In this work, the theories of Tomotika and Tjahjadi et al.[1, 2, 3] to measure interfacial tension between molten polymers using the breaking thread method are evaluated and compared. In particular, both theories were tested for PP/PS polymer pair at temperatures ranging from 200 °C to 240 °C. The results obtained using both theories corroborated. It is shown that both theories should be used in a complementary manner in order to enhance the accuracy of the breaking thread method.
Vibration-assisted injection molding (VAIM), which involves applying mechanical vibration to polymer melts during the injection and packing stages of molding processes to control polymer behavior at a molecular level, was applied on polystyrene and polycarbonate. With optimized VAIM processing conditions, the strength of polystyrene was improved by as much as 28% without sacrificing cycle time while the strength variation was reduced by 67%. With polycarbonate, however, the strength was improved only 7% and a toughness reduction resulted in some cases. In the current paper, the findings and theoretical basis related to these seemingly incompatible results are presented and discussed.
Thermolators continually pump water through a mold and have been used for cooling since the beginning of mold cooling. Thermolators, in general, are relatively large and are not considered to be energy efficient. New technology has been used to develop a system that only pumps water as needed to maintain a consistent mold temperature.A study was conducted to demonstrate the differences between usage of a thermolator and a pulse cooling system. Cost is a main factor when comparing cooling systems. In this study the cost factors that were compared were energy usage and cycle time.This study demonstrated that pulse cooling is much more energy efficient and that pulse cooling could reduce cycle time using part warpage as the controlling factor.
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