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

The Use of Scanning Electron Microscopy for Analysis of Skin Thickness in Polyvinylchloride
Whitney Seiberlich, David Heck, Chris Ostrowski, Nicole Hoekstra, May 2007

Scanning Electron Microscopy (SEM) was used to evaluate the skin thickness of polyvinyl chloride under various conditions. This investigation had two objectives: to determine if SEM is a practical tool for quantifying the skin thickness of a polymer and to determine if mold temperature and lubricant concentration effect skin thickness.Even though the measurements of the skin thickness are subjective, this investigation concluded that SEM is a practical method for quantifying skin thickness when multiple measurements are made along the cross section.The hypothesis that increasing mold temperature decreases skin thickness in PVC was confirmed with SEM measurements and with hardness results. The hypothesis that increasing lubricant amount increased skin thickness was confirmed with hardness measurements.

Investigation of Fracture Mechanism of HDPE Subjected to Environmental Stress Cracking
Byoung-Ho Choi, Jeffrey Weinhold, David Reuschle, Mridula Kapur, May 2007

Environmental stress crack resistance (ESCR) is a commonly used test to characterize cracking failure of high density polyethylene (HDPE) used in rigid packaging applications. From a resin design standpoint it is important to understand the mechanism of environmental stress cracking (ESC) especially in the case of materials with significantly different ESCR values. In this report, the morphology of ESC is studied by scanning electron microscopy (SEM). A model to predict polymer ESCR using tie chain concentration considering the permeability of IGEPAL® solution is proposed.

Mold Thermal Design: A Simplified Approach to Predict Part Temperature and Minimum Safe" Cycle Time"
Yunior Hioe, Keh-Chyou Chang, Narayan Bhagavatula, Jose M. Castro, May 2007

In an injection molding operation, the mold temperature increases from its initial value until a steady state is reached, therefore the minimum required cooling time also increases. Improving the mold thermal design will decrease the cooling time thus reducing total cycle time. The goal of this work is to develop software capable of simulating multiple cycles while balancing simulation time with accurate results. Three case studies are presented, one done in our labs and two on-site at an automotive manufacturing facility.

Microstructure of Thermoplastic Laser Welded Joints
M.H. Al-Wohoush, S. Sánchez-García, Musa R. Kamal, May 2007

Laser welded joints were examined using optical and polarized light microscopy, under both reflected and transmitted light, as well as scanning electron microscopy. The following materials were used: polycarbonate, polyamide-6, and polyamide-6 reinforced with 30% glass fibers. The influence of laser power on the shape, dimensions, and quality of laser-welded joints was evaluated, in both the absorbent and non-absorbent parts of the joint. Glass fiber orientation distributions were also examined. The effects of polymer type and fiber reinforcement, as well as laser power, on the dimensions and quality of the joints are reported.

Improving the Dispersion of the Carbon Nanotubes in Polymer Based Nanocomposites by Dry Coating
K.A. Narh, J.L. Jallo, R.N. Dave, May 2007

Carbon nanotubes tend to agglomerate in the polymer matrix, and it is difficult to separate individual nanotubes, even when surfactants are used during the mixing. To overcome the problems associated with agglomeration of nanofillers, the feasibility of dispersing carbon nanotubes in a polymer matrix by a novel methodology which involves mechanically pre-coating the polymer particles with the nano-fillers in the dry state prior to melt processing is being investigated. This paper presents the results of an experimental study for the purpose of evaluating the effectiveness of the surface coating techniques versus the conventional mixing methods used in dispersing nano-fillers in polymer matrices.

Evaluation of Nanoclay Exfoliation Strategies for Thermoset Polyimide Nanocomposite Systems
Michael J. Gintert, Sadhan C. Jana, Sandi G. Miller, May 2007

Prior works show exfoliated layered silicate reinforcement improves polymer composite properties. However, achieving full clay exfoliation in high performance thermoset polyimides remains a challenge. This study explores a new method of clay exfoliation, which includes clay intercalation by lower molecular weight PMR monomer under conditions of low and high shear and sonication, clay treatments by aliphatic and aromatic surfactants, and clay dispersion in primary, higher molecular weight PMR resin. Clay spacing, thermal, and mechanical properties were evaluated and compared with the best results available in literature for PMR polyimide systems.

Effects of Processing Parameters on the Cellular Morphology and Mechanical Properties of Mineral-Filled Thermoplastic Polyolefin Microcellular Foams
Steven Wong, Hani E. Naguib, C.B. Park, May 2007

In this study, the effect of processing parameters on the cellular morphologies and tensile mechanical properties of mineral-filled thermoplastic polyolefin microcellular foams prepared by using a two-stage batch process are investigated. The findings show that the mechanical properties were significantly affected by the foaming parameters, which altered the cell morphologies. The results from this study can be used to predict the microstructure and tensile mechanical properties of microcellular polymeric DTPO foams prepared with different processing parameters.

High-Temperature De-Molding for Cycle Time Reduction in Hot Embossing
Matthew Dirckx, Hayden K. Taylor, David E. Hardt, May 2007

Hot micro-embossing is a promising manufacturing technique for replicating millimeter- to nanometer-scale features in thermoplastic parts. However, the thermal cycle time limits production rate, and thermal contraction mismatch between the part and the tool can lead to damage during cooling. It is thus desirable to reduce or eliminate the thermal cycle. One approach is to de-mold at higher temperature, but elastic recovery can degrade accuracy. The degree of recovery depends on processing conditions. Proper selection of these conditions permits de-molding near or above the glass transition with little or no degradation of quality.

Composites in the Trucking Industry
Edward Zenk, May 2007

Over the years, the transportation industry has incorporated more and more composite materials into its vehicles. The automotive industry has used composites for exterior body panels, e.g. hoods, fascias, hatches and doors, as well as under the hood and structural reinforcements. The truck industry followed, by introducing composites for hoods, doors, roofs, bumpers and fairings. This paper will focus on the advancements made in composite materials, from hand-spray up open molded parts to the various improvements in sheet molding compounds to liquid molded resin materials. It will concentrate on parts used in the trucking industry and how quality, especially in cosmetic and surface properties, has improved over the years.

Analysis of Weld Seam Quality for Laser Transmission Welding of Thermoplastics Based on Fluid Dynamical Processes
Mireia Fargas, Lars Wilke, Oliver Meier, Helmut Potente, May 2007

Even though laser transmission welding (LTW) has already been implemented in industrial production, there are still process limitations rendering it uncompetitive with conventional processes and preventing its reaching full potential. The influence of the key process parameters and their interdependence is still not completely understood. This understanding is a condition for the optimization of the weld joint along with a more detailed theoretical description of the thermo-physical processes involved. This paper will present the results of an on-line detection method, the correlation to the mechanical properties and the FEA simulation, as well as possible approaches for overcoming existing limitations.

Structure-Property Investigation of Novel Multi-Layer Nanoclay Composites Formed Controllably with a Continuous Chaotic Blender
C. Mahesha, D.A. Zumbrunnen, D. Ratnaweera, D. Perahia, M.C. Kampf, May 2007

A continuous chaotic blender (CCB) has been used in prior work to controllably form a variety of polymer blend morphologies and arrange solid additives into networks. Low permeation films, electrically conducting plastics, and toughened plastics are examples of materials produced. In this study, initial property measurements are presented for extruded nanocomposite films having platelets localized and oriented within numerous discrete layers. The films have hierarchical internal structures and multiple nano-scales. The relation of barrier properties to structure is investigated by using the controlled in situ structuring capabilities of CCBs. Internal structure, crystalline morphology, degree of crystallinity, and oxygen permeation are presented.

Diffusivity Measurement of a Hydrophilic Migratory Additive in IPP Films
Siqiang Zhu, Noah Welsh, Douglas E. Hirt, May 2007

This paper describes the measurement of the diffusivity of a commercial hydrophilic additive, Irgasurf HL560, in polypropylene (PP) films at different temperatures. The model used was a standard 1-D diffusion model, in which the film weight was expressed as a function of time as the additive concentration at the film surface was kept at zero at all times. Experimentally, two cases were compared: 1. washing additive off the film with limited contact with the solvent; 2. immersing the film in solvent with continuous stirring. The effect of solvent diffusion into PP film was evaluated by thermogravimetric analysis (TGA). In both cases, film weight was measured after completely drying the film. Diffusivity was calculated by fitting experimental data to the mathematical model. Activation energy was obtained through the plot of diffusivities at different temperatures.

Functionally Graded Shape Memory Polymer
Kyung Min Lee, Patrick T. Mather, May 2007

In this paper, we present a new concept in for shape memory polymers (SMPs): functionally graded SMP. To make such a material, a commercially available UV curable polymer, NOA63, was cured by high intensity ultraviolet irradiation for various reaction times ranging from 5 min to 3.5 hours. The photo-cured NOA63 samples were characterized using differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and optical microscopy (OM) in order to investigate the high quality of shape fixing and recovery. The glass transition temperature was precisely controlled by varying the UV exposure time, resulting in NOA63 having Tg from 30 °C to 47 °C. DMA measurements for NOA63 revealed increasing tensile storage modulus with increasing crosslink density. A NOA63 sample was photo-cured in a spatially graded fashion, with different exposure times at different positions on for the same sample, demonstrating the possible usage of an optical temperature sensor or medical devices. Bulk and surface shape memory responses were investigated, revealing high quality shape fixing and recovery.

Weldability Evaluation on Effects of Filler Content of Polypropylene Copolymers for the Electromagnetic Welding Process
Joon Park, Brendon Au, Jon Esposito, Duane Lewis, C.K. Yoon, May 2007

The weldability using the electromagnetic process has been evaluated for different grades of polypropylene copolymers being used for automotive and domestic applications. As previous publications [1 – 2] have revealed, the electromagnetic welding process has demonstrated its robustness on various resins and applications.In this paper, comparative study between the vibration welding process and the electromagnetic welding process has been performed to evaluate effects of filler (talc and glass) content on weldability for polypropylene copolymers.Extensive DOE procedures to optimize the vibration welding process and electromagnetic welding process have been performed. In Ref. [3], a definition of weldability for the material has been suggested. For more conclusive evaluation, both welding strength and failure modes of the welded plaques need to be investigated. The same definition for weldability has been used for this study.In this study, it has been found that talc and glass content adversely affects weldability, while the electromagnetic welding process showed slightly better performance in welding strengths.

Recent Developments in Infrared Weld Technology
Robert Cunningham, Ken Sanborn, May 2007

This paper will present new developments in equipment and product in the field of Infrared Welding. These developments are a significant improvement over hot plate technologies and allow infrared welding to compete with other welding techniques at a lower cost for equipment and tooling. Recent developments in Polyamide materials allow one major headache associated with infrared welding of polyamides to be reduced. The paper will cover possible uses, advantages and design considerations. The overall benefit for the industry is to allow welding of a high strength high heat material in smaller production runs and for applications that use processes other than injection molding or non-glass reinforced grades which can present welding issues for other welding techniques.

Birefringence, Anisotropic Shrinkage and Luminance in Light Guide Plates: Modeling and Experiment
A.I. Isayev, T.H. Lin, May 2007

The frozen-in birefringence and anisotropic shrinkage of an injection molded light-guide plate (LGP) was simulated using a combination of a CV/FEM/FDM technique, a nonlinear viscoelastic constitutive equation and orientation functions. Various moldings were prepared from two optical grade polycarbonates (PC) and all of the components of birefringence along with shrinkages in the length, width and thickness were measured. The numerical results have been compared with experimental measurements at various processing conditions. The luminance of LGP moldings were found to be strongly dependent on processing conditions.

Stabilizer Additives R&D for Polyesters: Their Incorporation Inpolymerization Versus Downstream Compounding
Stephen M. Andrews, May 2007

The development and incorporation of stabilizer additives for bottle resin polyesters is increasingly more challenging and sophisticated. The diversity of polyester production processes and applications provide many possible insertion points for new additive technologies (1-3). Depending on the polyester problem it may be more effective to incorporate an additive in-polymerization (‘upstream’) versus (‘downstream’) compounding or converting. This paper discusses strategies for protecting polyester properties like color & thermal stability.

PA 12: A Manufacturer's Perspective
Ken Egnor, David Jordan, May 2007

Continental Industries has supplied mechanical fittings to the natural gas distribution industry since 1960. In 1969, we developed a complete plastic piping system that included polyethylene pipe, fusion fittings, and mechanical fittings. Continental Industries no longer produces polyethylene pipe but we have become the market leader for mechanical fittings. The original mechanical fittings were molded from PVC but now, fittings molded from PA 11 are much more common. Continental has used PA 11 since 1995 and we have supplied PA 11 fittings for PA 11 piping systems operating at pressures up to 200 psig. Due to the success of PA 11, and the high cost to install and maintain steel piping systems, several manufacturers of PA 12 are entering the market. Continental has sampled PA 12 resins from four manufacturers to determine how the product compares to PA 11. Our main concerns are availability, process capability and performance of the mechanical fitting. This paper will provide information on Continental's mechanical fittings, test methods, code requirements and the results of our PA 12 evaluation.

Effect of Inclusion Size and Location on PE Pipe Lifetime
Byoung-Ho Choi, Alexander Chudnovsky, Kalyan Sehanobish, May 2007

Understanding the slow crack growth (SCG) in engineering materials is very important for the prediction of the lifetime of structures. There are many empirical and theoretical approaches to modeling of SCG. However, there are many factors controlling SCG and structural lifetime such as, as basic material properties, residual stresses, the size and location of the crack origin, the load level and rate, temperature, structure geometry, and so on. Therefore, for engineering plastics it is difficult to predict, the SCG behavior on phenomenological ground. Understanding of fracture mechanism(s), and employment of fundamental science in modeling is required in studies of SCG. In this paper, the numerical algorithm and analysis of SCG is proposed based on Crack Layer (CL) theory. In addition, the time of SCG in HDPE pipe is modeled and compared with experimental data for various stress level. The effect of the crack origin (inclusion) size and location on the lifetime of PE pipes is analyzed using the numerical technique.

Laser Writable Polymers: Markability and Durability Characteristics
Satya Meruva, Michael Barker, May 2007

Generating a durable high contrast laser mark on dark coloured polymers has long been an issue. Various ABS compounds were produced with different additives. The compounds were laser marked using a 1064nm Nd:YAG laser at different power and frequency settings. One aspect of durability analysis, namely wear testing, was carried out using a purpose built scrub tester. The mechanisms of marking were also investigated using both light and scanning electron microscopy (SEM). Results indicate a clear necessity to obtain optimum values for laser power and frequency, in order to achieve a high contrast and durable mark.

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