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

Seek Risk©, A Methodology to Quantify Supply Related Risk
Joseph P. McCaul, May 2001

The SEEK Risk© Model was developed as a screening device to identify critical inputs to a firm and assess the effectiveness of countermeasures against potential disruptions. It is also a tool for comparing suppliers. The risk, both mitigated and unmitigated, is evaluated on a logarithmic scale. The assessment considers threats to both supply and technical competitiveness of the organization. The overall risk is scaled to resemble the well-known Richter Scale.

TiO2 Photochemistry and Color Applications
Dwight A. Holtzen, Philipp M. Niedenzu, Michael Diebold, May 2001

TiO2 is one of the most commonly used pigments in the coloring of plastics. TiO2 not only provides opacity but it is an excellent UV absorber. Hence, the pigment provides opacity and protection for plastics. This paper reviews the sources of TiO2 photochemistry and methods to control photoactivity.

A Next Generation Color Management Tool
Richard Johnston, May 2001

A knowledge-based system allowing for more effective use of color concentrates in plastics has been developed. Software and portable spectrophotometers utilized during processing present a color matching system that functions as a significant new color management tool to both injection molders and machine extruders. Used this way, as a quality or process monitor, the system can manage color consistency and product stability, because the deleterious effects of fluctuations in colorant loading on the physical properties of molded parts can be eliminated.

Biaxial Orientation of Blown Films Using an 80/20 LLDPE/LDPE Blend
Renata O. Pimentel, Rosario E.S. Bretas, May 2001

The Hermans orientation function and the White-Spruiell biaxial orientation factors [1, 2] of blown films of blends constituted of linear low density polyethylene (LLDPE) and low density polyethylene (LDPE), with 90% [3] and 80% of LLDPE, were calculated by infrared spectroscopy and differential scanning calorimetry. These films were produced by using a industrial equipment, controlling the following processing conditions: BUR=Rf/Ri, where Rf and Ri are the final and initial radius of the blown films, the temperature and the thickness of the sample.

Phenomenological and Morphological Characterization of Shear Induced Crystallization of Isotactic Polypropylene
M. Farah, R.E.S. Bretas, May 2001

The Flow Induced Crystallization (FIC) of polypropylene was studied in a slit die coupled to a twin screw extruder in several ranges of temperature and flow rate. FIC layers were measured and characterized and fitted to the Janeschitz-Kriegl model (1). A morphological investigation using TEM, SEM and WAXS were also done. Morphological results showed that the FIC layers are composed by extended lamellae in the ? phase. The ? phase was observed in the neighborhood of FIC layer generated probably by a transcrystallization effect.

Decorating Polyolefins: The Color of Change
May 2001

Processability, performance and cost make TPO’S a popular choice in various applications. Decorating polyolefins is still a challenge, but the advantages can out weigh the disadvantages if engineered with care.

Property Separation Based on Inversion of Micro-Mechanics
Zhenfeng Zhao, Xiaoshi Jin, May 2001

An inverse method to separate the matrix thermo-mechanical properties from the fiber-filled composite properties is suggested. The Tandon-Weng micro-mechanics model [1] and an orientation averaging method with orthotropic closure are used for the calculation of the anisotropic, heterogeneous properties on both a layer and element basis[2], then a combination of Newton's and least square methods are employed to solve the inverse problem. In comparison with a previously used separation method based on pvT model, the inverse method gives more accurate and reliable results.

Transfer Efficiency - Issues & Methods
Steve Stalker, May 2001

Many manufacturers of industrial coating application equipment often cite efficiencies of their spray equipment in terms of transfer efficiency (TE). While useful in comparing different types of equipment (conventional, HVLP, airless, etc.), its value as a tool in evaluating real-world situations is questionable. This article is not intended to be a full discussion of the methods for testing spray equipment efficiency. More at heart is what are the primary methods of testing and what are the issues.

The Effect of Contraction Angle on the Entrance Pressure Loss
Evan Mitsoulis, Savvas G. Hatzikiriakos, May 2001

The excess pressure losses due to end effects in the capillary flow of a metallocene linear low-density polyethylene (m-LLDPE) were studied both experimentally and theoretically. They were first determined experimentally as a function of the contraction angle (8° to 150°). It was found that the excess pressure loss function increases with increasing contraction angle from 8° to about 30° and consequently decreases up to contraction angles of 150°. Numerical simulation using a multimode K-BKZ viscoelastic equation and a purely viscous equation (Carreau model) have shown that the excess pressure loss function decreases monotonically with increasing contraction angle, an observation that contradicts the experimental results. The origin of this disagreement is also discussed.

A New Non-Reactive Polymer Processing Additive (PPA) for Use with HALS and Other Chemically Interacting Additives
Steve E. Amos, Maria P. Dillon, Susan S. Woods, William Coggio, Joyce Kunde, May 2001

Polymer processing additives are used to reduce melt fracture, increase the processing window and eliminate die lip build-up and gels in polyolefins. There are additives that can interfere with the performance of the PPA by four main mechanisms - adsorption, abrasion, site competition and chemical reaction. Strong bases such as hindered amine light stabilizers (HALS) can cause the PPA to lose effectiveness due to both site competition and chemical reaction. Introduced is a next generation, non-reactive PPA that has improved performance compared to conventional materials.

Failure Analysis of Hinges: Case Studies, Part One
Rabeh H. Elleithy, May 2001

Plastic hinges are subjected to different types of stresses during service. Some case studies are presented in this paper to show the effect of service history, processing conditions, and part design on hinge failure. Microscopic analysis was used in these investigations to identify the fracture features. Additionally, Finite Element Analysis was used to estimate the stresses on the hinges during service. The first case shows mainly the effect of adverse service history on the hinge performance. The second case illustrates primarily the importance of appropriate processing conditions in preventing hinge failure. The third case describes essentially the combined contribution of end-use and part design on limiting the hinge lifetime.

Combining Boron Nitride with a Fluoroelastomer: An Enhanced Polymer Processing Additive
Manish Seth, Franky Yip, Savvas G. Hatzikiriakos, May 2001

The effect of a new processing additive (boron nitride powder in combination with a fluoroelastomer) on the rheology and processability of molten polymers is studied. The equipment used include an Instron capillary rheometer equipped with a special annular die (Nokia Maillefer wire coating cross-head), a twin screw extruder equipped with a blow moulding unit, and a parallel-plate rheometer. Metallocene polyethylenes with and without boron nitride (BN) and fluoroelastomer are tested in extrusion and conventional high density polyethylenes with and without BN with fluoroelastomer are tested in Blow moulding operations. First, it is demonstrated that BN is a superior processing aid compared to conventional fluoropolymer ones. Secondly, it is found that the combination of BN powders with a small amount of a fluoropolymer improves even further the processability of molten polymers (melt fracture performance).

Valve Screw Design - A New Concept on Screw Design Optimization
Peter N. Wang, May 2001

Adding valve" means to a screw is a concept of screw design optimization in a way of matching four normally concerned processing functions. The four processing functions are conveying melting mixing and pressurizing. This paper discusses the relationships between these four functions and promotes design ideas as to how to change them individually. A design called "valve screw" which contains a screw body groups of shear rings and a tube shaped tip are proposed. The shear rings and tube tip serve as valve means controlling / enhancing mass flow rate melting rate and mixing rate. Pressurizing is also indirectly controlled. A high efficiency overall optimized operation is therefore achieved."

Shear Ring Screw Design - A Design against Barrier Screw Design's Philosophy
Peter N. Wang, May 2001

Barrier screw design follows a design philosophy as to keeping melt separate from solid. This leads to ununiform shearing, i.e. all shearing takes within the place of the thin film between the solid bed and the barrel inner surface while the main body of the solid bed has been left no shear at all. The present shear ring screw" breaks the solid bed into small pieces (or individual pellets) at early stage of melting. This would be achieved by using shear rings with series of angled flow through ports which makes the ring self-driven by fed material. "Drag induced melt removal melting mechanism" [12] or "laminar segregated melting mechanism" [3] converts to "pulse dissipative mix-melting mechanism". It is proved theoretically as well as experimentally by Chung and Wang [6] that the heating time required for melting decreases exponentially with decreasing the pellet size and the heat transfer coefficient h (cal/cm2-s-°C) increases substantially due to convections around pellets. These are roots of current design."

Blends of Polypropylene (PP) and Polyamide 6,6 (Pa 6,6) with Functional Polyolefin Elastomer (FPOE) as a Compatibilizer
Hui Tang, Charles L. Beatty, May 2001

The objective of this study is to evaluate the effects of functional polyolefin elastomer (FPOE) on the morphology, and mechanical properties of the blends of polypropylene (PP) and polyamide 6,6 (PA 6,6). PP was blended with different weight concentration of PA 6,6 and functional POE. All blends were carried out in a reactive twin-screw extruder. The mechanical properties of the blends, such as tensile strength at yield (?y), modulus of elasticity (E), and elongation, were examined. Moreover, their morphological behavior was investigated through scanning electron microscopy (SEM). It is clearly indicated that the morphology structure can be controlled through functional POE. It was found that the morphology of the cryogenic fracture surface of the blends was dramatically changed, from micron fibers in the mechanical blending to sub-micron fibers in the reactive blending. The tensile strengths at yield (?y), and modulus of elasticity (E) of the blends with functional POE are increased relative to mechanical blends. However, the elongation of the reactive blends is decreased. These results illustrated that the functional POE can be employed as a effective compatibilizer in the blends of PP and PA 6,6. It stands to reason that functional POE can reduce interfacial tension preventing the blends from agglomerating as well as leading to smaller domain size and better dispersion of PA 6,6 phase in the PP matrix.

The Blends of Polypropylene (PP) with Functional Polyolefin Elastomer (FPOE) for Recycling of Xerographic Toners
Hui Tang, Charles L. Beatty, May 2001

This paper presents experimental results on the blends of polypropylene (PP) with functional polyolefin elastomer (FPOE) for recycling of xerographic toners. All experiments were carried out in a co-rotated reactive twin screw extruder. The investigation of the mechanical properties and morphology for different blends consist of PP, xerographic black toners and functional POE (FPOE) through reactive compounding. It is of interest to note that the notched Izod impact resistance of the blends with functional POE (FPOE) is significantly improved relative to physical blends. However, tensile strength at yield (?y) and modulus of elasticity (E) of the reactive blends are reduced. The reason why the impact properties should be so is clearly shown by the stress-strain behavior of the blends. Morphology of the cryogenic fracture surfaces of the blends was studied through scanning electron microscopy (SEM). The results of morphological studies indicated that not only the domain size of the phase of black toners could be reduced but also the interfacial adhesion could be enhanced through proper functional POE (FPOE). The phase morphology of the blends also illustrated that better dispersion of black toners could be obtained through using FPOE whereas serious agglomeration of black toners was found in the physical blends. It is elucidated that the functional POE could be an excellent candidate of compatibilizer for recycling xerographic black toners.

Training of Operators in Extrusion and Stretch Blow Molding
Ottmar Brandau, May 2001

The current lack of qualified operators in the blow molding industry and its effects on blow molding operations is described. The need for the training of blow molding operators is illustrated. Different methods of training are described and evaluated with respect to their effectiveness. The reasons for the lack of trained operators are shown and from there new training methods are developed overcoming some of the shortcomings of other methods. It is shown that only training material closely resembling the actual plant conditions is well accepted by trainees. Engineering concepts need to be translated into understandable training materials. Retention levels are improved by giving short tests challenging the trainees into thinking about the material presented. Given the right methods, one can teach more complex relationships between material properties, machine functions, and settings.

Reciprocating-Screw Injection Molding Machine for Microcellular Foam
Jingyi Xu, David Pierick, May 2001

The reciprocating-screw (RS) injection molding machine for microcellular foam has been successfully developed. It creates the necessary conditions for a single-phase solution with a specially designed plasiticizing unit. An overall system is the key for successfully implementing a microcellular foam process. The important components for the microcellular foam molding machine system including a plasticizing unit, injection unit, hydraulic unit, clamp unit, gas unit, are discussed in this paper. The general guidelines to design an injection molding machine for microcellular foam are listed as the conclusions.

Transient in the Mold Measurements of Thermal Diffusivity Using Injection Molded Cylinders
Boris L. Serebrennikov, Nick R. Schott, Miftahur Rahman, May 2001

The thermal properties of polymers such as thermal conductivity, k, heat capacity, Cp, and thermal diffusivity, ?, are important properties that affect polymer processing economics due to their critical influence on cooling time and cycle time (1). For cooling calculations one needs the physical properties of k, ?, and Cp to calculate the thermal diffusivity. These vary with each resin and also with the additives, fillers and reinforcements. The task of collecting these data is almost insurmountable since the U.S. has about 8000 resin grades recognized by UL (Underwriter’s Laboratories) and a total of about 30,000 grades are commercially available. By injection molding and experimentally determining the thermal diffusivity under actual molding conditions one can eliminate the individual measurements of k, ? and Cp and instead measure the thermal diffusivity directly. The objective of the study was to show that this is a practical approach to the evaluation of the thermal diffusivity for injection molding cooling calculations.

Optimizing the Mechanical Performance in Semi-Crystalline Polymers: Roles of Melt Temperature and Skin-Core Crystalline Morphology of Nylon
N. Sanjeeva Murthy, Val A. Kagan, Robert G. Bray, May 2001

Crystalline texture and mechanical (tensile and flexural) properties of injection molded nylon 6 were evaluated to understand the influence of one of the key-processing variable, the melt temperature (Tmlt). We find that mechanical properties are sensitive to Tmlt only below ~ 250°C. Rapid quenching of the surface produces a skin with lower crystallinity than the core, which cools more slowly; this difference in the rate of cooling produces ? crystalline form in the skin and ? crystalline form in the core. Higher tensile strength at yield, lower elongation at break and higher flexural strength were observed in specimens molded at lower Tmlt. These characteristics are associated with thicker and less ordered skin, and a lower crystallinity core. The role of the Tmlt on micro-structure and mechanical properties of injection molded nylon 6, the development of skin and core morphologies, and the role of the residual stresses in the core are discussed.

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