SPE Library

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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Conference Proceedings

Plastics Failure Due to Oxidative Degradation in Processing and Service
Myer Ezrin, Amanda Zepke, John Helwig, Gary Lavigne, Mark Dudley, May 2000

Aliphatic hydrocarbon polymers, such as PE, PP and copolymers thereof are particularly susceptible to oxidative degradation to lower molecular weight in processing and in service. The result is reduced strength, embrittlement, and shorter service life. High temperature required for melt processing is a major factor in oxidative degradation. Decrease in oxidative induction time or induction temperature measured by differential scanning calorimetry are practical methods of monitoring the effect. Formulations need sufficient antioxidant to be protected during processing and in service.

Adding Value to Rotational Moldings with Color and Special Effects
Nick Henwood, May 2000

This paper reviews the different ways of adding color in rotational molding and provides technical and economic arguments for each method. The effects of pigment incorporation on base material properties are discussed and the importance of factors such as pigment type, pigment loading and method of mixing are examined in relation to material processing, physical properties and the aesthetics of the final rotomolded part. The use of special effects such as stone and antique look colors to give further value enhancement is discussed.

Some Reasons Not to Use Multi-Cavity (>4) Tools
John W. Bozzelli, May 2000

Injection molding continues to be the preferred plastic process for making large quantities of plastic parts. The goal is to make identical parts. When parts are not identical problems develop, not just in performance but also in assembly. The trend toward more complex parts, coupled with demanding tolerances continues to challenge processors in pursuit of the goal of identical parts. Reasons against the trend for high cavitation molds are proposed.

Polymer Melt Flow Behavior in the Coinjection Molding Process
K.T. Nguyen, E. Turcott, A. Derdouri, D. Ait Messaoudz, B. Sanschagrin, B.A. Salanton, K.A. Koppi, May 2000

An experimental study of the co-injection molding process was carried out. The fingering instability due to the difference in viscosities of the two materials gave rise to early breakthrough of the core material and non- uniform skin layer thickness. The core material was also used as tracer material for flow visualization of the injection molding process. The V formation near the wall as well as the mushroom effect, previously predicted, was observed.

Nanocomposites: The Importance of Processing
H. Ryan Dennis, Douglas L. Hunter, Dohoon Chang, Sangyup Kim, James L. White, Jae Whan Cho, Donald R. Paul, May 2000

Nanocomposites have been studied for nearly 50 years, but few references deal with the importance of how the organoclay was processed into the plastic of choice. Many articles focus on the importance of the chemistry used to modify the surface of the clay, usually montmorillonite, without including the role of processing. This paper demonstrates the importance of both the chemistry of the clay surface and how the clay was processed into the thermoplastic. Two different clay treatments were added to polyamide 6 using four different types of extruders with multiple screw designs.

Injection Molding and Physical Aging Properties of Amorphous Poly(ethylene terephthalate)
A. Bhakkad, E.A. Lofgren, S.A. Jabarin, May 2000

Physical aging characteristics of amorphous poly(ethylene terephthalate) have been evaluated in relationship to several important injection molding parameters. For these investigations; packing pressure, melt temperature, and mold temperature were each varied individually, with other conditions held constant. Aging studies were performed at three different storage temperatures, using the molded specimens. Changes in density, notched Izod impact strength, and enthalpy of relaxation were monitored as functions of aging times. Time temperature superposition analyses were performed using experimental data and master curves were constructed. Results give predictions of lower temperature long term enthalpies of relaxation and notched Izod impact strength properties.

The Effects of Compatibilizers, Polyamide-6 Grade, and Filler Type on the Properties of TPO/Polyamide-6 Blends
Luca Saggese, Carol M.F. Barry, Stephen A. Orroth, May 2000

This study examined the effect of compatibilizers, polyamide-6 grade, fillers, and injection rate on the properties of polyamide-6/TPO blends. The addition of polyamide-6 to TPO raised tensile and flexural moduli, and consequently, DTUL and scratch resistance; however, it adversely affected Izod impact strength. While a di-terminated polyamide-6 (NH2 capped) exhibited better properties than a non-terminated material (COOH end), wollastonite fillers had a greater influence on the blend properties. Compatibilizers primarily impacted elongation, impact strength, and scratch resistance whereas high injection velocities increased impact strength and scratch resistance.

Recycled Fiberglass Composite as a Reinforcing Filler in Post-Consumer Recycled HDPE Plastic Lumber
S.D. George, S.H. Dillman, May 2000

Post-consumer high-density polyethylene is commonly used to make lumber products, but such products are substantially less stiff than wood lumber. Using a two factor full factorial experimental design, the effects on tensile, flexural and impact properties of adding ground recycled fiberglass composite in combination with wood flour to high density polyethylene were investigated. The addition of ground fiberglass composite was found to significantly increase tensile and flexural modulus, while decreasing impact strength. Ground fiberglass was found to have a greater stiffening effect than wood flour, but wood flour had no significant effect on impact strength.

Polymer Near-Surface Behavior Characterized by Reflectometry and Complementary Techniques
Mark D. Foster, May 2000

Engineering the near-surface structure and properties of materials requires characterization tools that are sensitive to that structure and those properties. X-ray and neutron reflectometry provide exquisite depth resolution for near surface structure. These tools are most powerful, however, when combined with lower resolution complementary techniques that give the depth profile directly or with techniques which resolve the structure laterally. Reflectometry's capabilities are demonstrated by a study of the interfacial segregation of star-branched polymers in a blend of linear and star chains. Dynamic secondary ion mass spectroscopy and nuclear reaction analysis are used as complementary probes.

Compatibilization of PP/HDPE Blends: Morphology and Interfacial Tension
Adriana Martinelli Catelli de Souza, Nicole Raymonde Demarquette, May 2000

In this paper the compatibilization of polypropylene (PP)/high-density polyethylene (HDPE) blend was studied through morphological and interfacial tension analysis. Three types of compatibilizers were tested: ethylene-propylene-diene copolymer (EPDM), ethylene-vinylacetate copolymer (EVA) and styrene-ethylene/ butylene-styrene triblock copolymer (SEBS). The morphology of the blends was studied by Scanning Electron Microscopy. The interfacial tension between the components of the blends was evaluated using small amplitude oscillatory shear analysis. Emulsion curves relating the average radius of the dispersed phase and the interfacial tension to the concentration of compatibilizer added to the blend were obtained. It was shown that EPDM was more efficient as an emulsifier for PP/HDPE blend than EVA and SEBS.

Improving Polyethylene Performance - The Use of Metallocene Catalysed Polyethylene in Injection Moulding
M.J. Murphy, P.B. Kelly, G.M. McNally, M.P. Kearns, May 2000

A range of medium density, metallocene catalysed polyethylenes (mPEs), and conventional polyethylenes (PEs) were injection moulded using different mould cooling conditions. The results for the metallocene polyethylenes show significant improvements in impact and tensile performance. Increases of over 200% in tensile elongation for metallocene PE resins over the conventional PE resins were recorded. D.S.C. analysis shows the metallocene PE resins to be more crystalline in nature than the conventional polyethylenes.

Relative Dimensional Change of Various Nylon Products Due to Moisture Absorption
Steve Gerbig, Bonnie Richter, Brian Helfrich, May 2000

In plastic materials published data, moisture absorption is almost always expressed in terms of percent weight gain. While this information is important for comparison purposes, it doesn't truly relate to the design engineers' application and use of these materials. This study will quantify and compare the relative dimensional changes which occur in parts as they are exposed to a humid environment and move from the dry-as-molded state toward saturation using nylon types 6, 66 and 46.

New Thermoplastic Resin Compounds Utilizing Highly Efficient Conductive Filler System
Niraj Patel, May 2000

During the last few years, there has been a rapid growth of electronic equipments within industrial, commercial and domestic environments. This has led to a need to control the problem of static build-up and discharge during the manufacture, distribution and usage of products containing microprocessors. In addition, often it is necessary to contain electromagnetic radiation (EMI), which can inhibit normal operation of microprocessor containing devices. The issue of static control and discharge is also important in areas such as prevention of ignition of flammable fluids and handling of powder (to prevent dust explosion). Commercial plastic materials are insulators and hence, are often modified using conductive materials like carbon fibers to provide static dissipation and EMI shielding. This paper describes highly efficient ESD / inherently shielding engineering thermoplastic resins which can be used in a broad variety of applications. A binder was identified in this study that enhanced shielding effectiveness and reduced resisitivty of resin systems with which it was incompatible.

Gas Barrier Behavior of Syndiotactic Polystyrene
K. Hodge, S. Nazarenko, G. Capaccio, May 2000

The effect of crystallinity on barrier properties of syndiotactic polystyrene (s-PS) was studied. The crystallinity was induced in s-PS by cold crystallization and crystallization from the melt. Two thermally induced crystalline forms ? and ? were observed in all crystallized samples as well as the presence of ?-mesomorphic phase in the samples cold crystallized at lower temperatures. The oxygen permeability and diffusion occurred at finite rates in the loose a hexagonal crystalline phase while it was negligible in better-packed ? orthorhombic phase. The permeability and diffusion of oxygen increased with an increase of the amount of a ordered phase while the solubility decreased, remaining, however, still soluble for oxygen even at 100%.

Integrating Thin-Wall Molder's Needs into Polymer Manufacturing: Part II
W.G. Todd, T.J. Schwab, D.L. Wise, May 2000

Polyethylene (PE) injection molded rigid containers are widely used for food packaging and promotional drink cups. Molders of these containers have well-defined processing needs and molded part requirements. Likewise, the polymer manufacturer has well-defined manufacturing and analytical methods for characterizing resin properties. This paper presents a predictive model that was developed from molded part testing versus PE resin physical properties. Utilizing this information, the resin producer and the injection molder can work together to improve molded part performance.

A Study of the Tensile Creep Behavior of Recycled High Density Polyethylene in Aqueous Mediums
John Raybuck, Daniel Heuer, Paul Koch, May 2000

Recycled polymers are currently being used in the design of commercial products for the maritime structure industry. Marine pilings, pier fenders, and pier support elements are just some of the products being designed with recycled polymers. Understanding the effect of submersion in salt and fresh water on the mechanical properties of the material used in these products is important. This study will examine the tensile creep behavior of recycled HDPE in ocean water, fresh water from Lake Erie, distilled water, and air. A specially designed apparatus for aqueous creep testing was utilized to obtain the data for this study.

Transient Viscoelastic Simulation of Coextrusion Flows in Coat-Hanger Dies
Alberto Rincon, John Vlachopoulos, Joseph Dooley, May 2000

A 2-D transient finite element model of two-layer coextrusion has been developed with the Criminale-Erikson- Filbey (CEF) constitutive equation to study the problem of interfacial instability. Experiments were done with LDPE 132I™ (Dow Chemical Co.) in a coat-hanger die using two extruders, under well controlled temperature and flow conditions, where stable and unstable interface profiles were observed. Cross-sections of the frozen heel were taken and compared to transient simulations by quantitatively examining the position of the interface between the two layers.

Welding of Plastics: Introduction into Heating by Radiation
C. Bonten, C. Tüchert, May 2000

For welding of plastics, various procedures of heat transfer are presently in use. Non-contact heating by radiation allows heating e.g. without contamination of a heated tool and makes heating faster by volume-absorption of the material. Presently infra-red lamps and infra-red laser beams are in use for welding of plastics. This paper wants to give an introduction into the physical principles of heating by infra-red radiation, wants to divide between surface and volume absorption of different materials and wants to give a survey about the advantages and disadvantages of infra-red lamps and lasers.

Effects of Various Fillers on the Coefficient of Thermal Expansion of Epoxy Resins
Glenn E. Lawson, May 2000

It has long been recognized that the predictive ability of the rule of mixtures for coefficient of thermal expansion (CTE) is less than desired. It ignores the elastic interaction and restraint between the matrix and the filler, hence yielding values that are too high. The predictive ability of the rule of mixtures and three other theories are compared to actual measured CTE values of over 90 particulate filled epoxy formulations. It has been found that the Kerner theory can predict the CTE within 8 ppm/°C at the 95% confidence interval for the epoxy systems evaluated.

A New Impact Modifier for Toughening Clear APET
Edward J. Troy, Anthony C. Fazey, Evan Crook, May 2000

Polymers, as well as glasses, exhibit physical 'aging' which leads to embrittlement. Impact modifier additives counteract this embrittlement. In clear polymer systems, such as amorphous polyethylene terephthalate [APET], blends with typical commercial impact modifiers show a significant loss of optical clarity. The work presented here, based on a new impact modifier additive, shows that embrittlement of APET can be counteracted without significant loss of optical clarity.

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