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

Stress Cracking Caused by Hot Plate Welding – Theoretical Analyses
H. Potente, J. Schnieders, May 2005

In the field of hot plate welding, experimental investigations show that the stress cracks are caused by inherent stresses in the component, which are induced in the part while it is being heated on the tool.First, the process parameters and the phenomena of stress cracking in amorphous thermoplastics are discussed. Than, the development of a theoretical model for the one-dimensional temperature and stress calculation of simple hot plate welded geometries is described.The prescribed method makes it possible to estimate the effects of the process parameters on the phenomena of stress cracking. The results of the physical-mathematical model are compared with the results of experimental investigations.Finally, our understanding of the phenomena of stress cracking, as well as of the process involved, is enhanced with the aid of the physical model that is presented.

Modification of Polymers Using Polyvinyl Butyral Based Additives
George H. Hofmann, Win-Chung Lee, May 2005

Polyvinyl butyral (PVB) is the tough polymer film widely used as the interlayer in safety glass laminates, such as automotive windshields.This material is now available in pellet form (Ecocite®) for easy blending into other polymer resins. It has been shown to act as an impact modifier and/or processing aid when blended, at low levels, into a variety of engineering resins, polyolefins and PVC. At relatively high loadings, it performs as a permanent plasticizer imparting toughness, flexibility, enhanced processibility and oil resistance.The residual hydroxyl groups in PVB provide active surface sites to enhance paintability and adhesion to other materials. PVB’s adhesion has been found to enhance stiffness/compatibility when glass fibers and minerals are incorporated into engineering resins. The hydroxyl functionality has been used as crosslinking sites to form tough oil-resistant thermoplastic elastomers (TPE) via dynamic vulcanization.

Process Monitoring of Polymer/Clay Nanocomposites Compounding Using Optical Transmission Measurements
Anthony J. Bur, Steven C. Roth, Paul R. Start, May 2005

A family of nylons, nylon 6, 11 and 12, have been compounded with organo modified clays using a twin screw extruder that was instrumented with an optical sensor. The sensor was positioned in a slit die that was attached to the end of the extruder. Optical transmission measurements were used to monitor exfoliation of the clay and to establish a scale for measuring the extent of exfoliation. Transmission of light through clay filled nylon is dependent upon the size of the scattering clay particles, and as the particles decrease in size due to exfoliation, light transmission increases.

Strategies for the Manufacture of Low-Density, Fine Celled PBS Sheet Foams Blown with CO2 Using an Annular Die
Donglai Xu, Chul B. Park, Robert G. Fenton, May 2005

This paper presents strategies for the manufacture of low-density and fine-celled biodegradable polyester foam sheets blown with CO2 using an annular die. The basic approach is to minimize gas loss by completely dissolving gas, suppressing an initial hump, promoting the number of cell layers across the foam thickness and optimizing the processing temperature. Parametric experiments with various annular dies have been performed to verify the feasibility of the proposed strategies. Low-density biodegradable polyester sheet foams with a volume expansion ratio of over 20 have been successfully achieved even with the gaseous blowing agent CO2.

Highly Transparent Elastomeric Films
Andre J. Uzee, May 2005

Styrenic block copolymers (SBCs) are increasingly being used in elastomeric film applications. Many technical articles and patents describe blends of thermoplastics with styrenic block copolymers for use in elastomeric films. This paper describes blends of styreneisoprene, styrene-butadiene and styrene-isoprene-butadiene block copolymers for use in the production of “transparent” elastomeric films. In addition, it presents new and novel blends that can be combined in a solution process to produce a single pellet product that can be extruded without the cost of additional compounding steps. The physical properties of such blends are compared to compounded blends.

Evaluation of Adjacent Flow Weldline in PC/ABS
Koji Yamada, Kiyotaka Tomari, Satoko Baba, Umaru Semo Ishiaku, Hiroyuki Hamada, May 2005

Morphology of acrylonitrile-butadiene-styrene terpolymer (ABS) phase of adjacent flow weldline in polycarbonate (PC)/ABS moldings and its mechanical properties were discussed. Observation by scanning electron microscopy (SEM) clarified that the ABS phase at the weldline interface was a very fine dispersion and sandwiched between two pairs of rows of coarser ABS phases. This characteristic morphology was not observed in the non-weld region, suggesting that the coarser ABS phases were caused by turbulent shear flow behind the obstacle generating the weldline. The strength of the weldline region was 10 % lower than that of the non-weld region and moreover decreased by 15 % in the presence of V-notch on the surface. Removal of the V-notch immediately increased the strength to the same level of weldline region having no V-notches. During tensile testing, fracture occurred in the layer containing the coarser ABS phases surrounding the weldline interface, resulting in the decrease of the strength of weldline.

Surface Modification of Polypropylene Films Using Hydrophilic Additives
Chakravarthy S. Gudipati, Douglas E. Hirt, May 2005

The ability of various end-functionalized poly(ethylene glycol)s to migrate to the surface of polypropylene-PEG films was investigated using AFM, contact angle goniometry and FTIR. The blends were prepared using PEGs of several molecular weights (2k and 10k) at 5, 10, and 15 wt% to study the effect of chain length and composition. The film surfaces exhibited phase segregated morphologies as revealed by AFM in comparison to neat PP film. The blend with 15 wt% PEG (10k) was the most hydrophilic as confirmed by water contact angle of 88°, as compared to 104° for PP. The surface hydrophilicity increased further upon aging for 3 days as well as annealing the films at elevated temperature.

Grafting Amine-Terminated Branched Architectures from Polylactide Film Surfaces for Improved Cell Proliferation
Amol V. Janorkar, Edward W. Fritz, Jr., Karen J.L. Burg, Andrew T. Metters, Douglas E. Hirt, May 2005

Poly(L-lactide) (PL) has been used as a bioabsorbable material in the medical and pharmaceutical fields. The unmodified hydrophobic PL surface generally has low cell affinity; thus, modification of PL film surface properties is necessary to improve its use as a biomaterial. Our surface modification method involved the use of photografting and typical wet chemistry to create branched architectures containing amine functionalities on the periphery. The resulting film surface was analyzed using contact angle goniometry. F3T3M mouse fibroblast cells were cultured on unmodified PL film and PL film grafted with the branched structure. Optical micrographs showed enhanced cell proliferation on the surface-modified PL film.

Injection Molding of a High Heat Polyetherimide Sulfone with Tg of ? 250°C
Mark A. Sanner, Andy May, May 2005

An injection moldable thermoplastic Polyetherimide Sulfone resin with Tg of ? 250°C (482°F) was developed for advanced automotive lighting systems and other applications requiring thermal capabilities greater than those currently achieved with Polyetherimide. With a +30°C higher Tg than Polyetherimide, the resin can still be melt processed using standard injection molding machine equipment by increasing melt temperature to 385-415°C and mold temperatures of 150- 175°C. The injection molding processibility of the resin and its properties are presented and compared with Polyetherimide.

Processing Highly Filled Pre-Compounded Pellets on Single Screw Extruders
Edward L. Steward, May 2005

One of the more popular filled polymer materials has been wood flour with polyolefins and this will be used as the example throughout this paper. Processing other highly filled polymer and filler choices will often follow the same logic as that with wood fillers, so the discussion is somewhat generic in that respect. In the realm of profile extrusion utilizing wood filled plastic materials, there are a few machinery approaches that have proven successful. Although these machinery setups will be discussed and briefly compared, the single screw machine being fed pre-pelletized material will be the main thrust of the paper. The best choice for a given installation typically comes down to economics and product physical properties. Both the capital costs and the operational costs are important when selecting the extrusion means. Some of the major processing and equipment comparisons will be discussed. Since no one machinery approach has monopolized this application to date, perhaps different extrusion houses will still decide on different means to get successful profiles from high wood (or other filler) percentages.

Advances in Understanding the Cure and Properties of Thermosetting Systems in the Laboratory of Professor John K. Gillham during His Career
John K. Gillham, May 2005

Premise of Research: (a) Properties vs. gelation and vitrification. (Vitrification occurs when Tg = Tcure); (b) Isothermal properties at T vs. conversion as a consequence of rising transition temperatures (e.g., modulus and density at T vs. T? and Tg); (c) Effect of isothermal aging in the localization of subsequent properties vs. temperature. Results in Graphical Form: (a) TTT Diagram: Isothermal Time-Temperature- Transformation Cure Diagram; (b) CHT Diagram: Continuous Heating TTT Diagram; (c) Property- Temperature-Conversion Diagram.

Stress Concentration Evaluation in an Injected Commercial Piece using Computational Tools
M. Candal, R. Morales, H. D´Armas, H. Rojas, May 2005

The stress concentration evaluation in an injected commercial piece (CD case) was studied for typical amorphous polymers (polystyrene (PS) and high impact polystyrene (HIPS). It was obtained the general stress field in critical areas by using commercial simulation and modelation programs. Three constants for each material were determined considering: nominal stress in service and nominal stress considering process conditions plus service both calculated using a simulation program (K1service and K1process) and nominal stress in service using a solid 3D modelator program (K2service). The estimated stress concentration factor in service obtained from the programs showed differences less than 6%. The estimated stress concentration factor in process plus service is 62% bigger than the estimated stress concentration factor only in service.

Durability of E-Glass Fiber Reinforced Vinyl Ester Polymer Composites with Nanoclay in an Alkaline Environment
Naveenkamal Ravindran, Shu-Kai Yeh, Eung Ha Cho, May 2005

Two kinds of GFRP (glass fiber reinforced polymer) composite samples were used: the first with 2 layers of E-glass fiber fabric in a matrix of vinyl ester resin; and the second with addition of 1wt% and 2wt% nanoclay to the polymer matrix. The samples underwent aging tests with a sustained load of 890N (12.5% of tensile strength) for 3 months and the reduction in tensile strength was determined.A study was conducted to monitor the weight change of the GFRP specimens immersed in the alkaline solution under no sustained load. Another study was conducted to monitor the weight loss of glass fiber fabric immersed in the alkaline solution, also under no sustained load. Similar tests were conducted with neat resin samples and resin samples with 1wt% and 2wt% nanoclay.The results of the sustained load tests show a 12- 17% reduction in the tensile strength of the composite samples. However, no particular distinction was observed between the two types of GFRPs. It has been found from the absorption tests conducted on GFRP samples that the rate of alkaline solution absorption is higher in the GFRP samples without nanoclay followed by samples containing 1% and 2% nanoclay in that order. It has also been found that the dissolution rate of the glass fiber piece is linear. Tests conducted on the resin samples have shown that the weight gain was the highest in samples with 2% nanoclay followed by samples with 1% nanoclay and then by plain polymer samples.

Viscoelastic Behavior of Highly Filled HDPE/Wood Flour Composites
Velichko Hristov, Elizabeth Takács, John Vlachopoulos, May 2005

Dynamic and steady shear viscoelastic properties of highly filled (50-70%) HDPE/Wood flour composites have been investigated by parallel-plate and capillary rheometers. The concentration effect of a new lubricant and coupling agent on the melt rheological properties of the composites was explored as well. The results showed that addition of both lubricant and coupling agent to the 70% filled HDPE composite considerably improved its flow behavior. An increase in the complex viscosity and storage modulus of the wood filled systems at low concentration of both modifiers was observed in case of 50% filler loading. Higher concentrations of modifiers resulted in a decrease of the complex viscosity. In capillary flow, it was observed that the lubricant improved the processability to a great extent. It was also found that all wood filled composites did not obey the Cox-Merz rule. It was concluded that dynamic and steady shear viscosity measurements by parallel plate rheometer did not correspond to capillary measurements at elevated wood flour loadings.

Flexible Thermoplastic Elastomer (TPE) Based on Ionomer Technology
J. McCoy, T. McQuaide, A. Montalvo, M.R. Sadeghi, A. Puttarudraiah, May 2005

Ionomer products have been in the marketplace for more than 30 years. These products offer outstanding toughness, high melt strength, excellent abrasion resistance with hardness values greater than 40 Shore D. This new class of patented flexible ionomer alloy thermoplastic elastomers (TPEs) have been developed with lower hardness and lower modulus for both Consumer and Automotive applications. These products have hardness values in the range of 70 to 90 Shore A with high toughness and tear strength, high mar/abrasion resistance, good chemical resistance, superior stain resistance, and controlled gloss.This paper will address the polymer science and technology for these new ionomer-based TPEs with respect to morphology, physical properties, rheological properties and aesthetics, as compared to traditional TPEs, including thermoplastic vulcanizates (TPV).

Nanostructured Polymer Blends Prepared via in Situ Polymerization and Compatibilization: Processing, Morphology and Crystallization Behavior
Samy A. Madbouly, David Rhoades, Joshua Otaigbe, May 2005

A simple and versatile method of in situ polymerization of macrocyclic carbonates in the presence of a maleic anhydride polypropylene (mPP) matrix to yield a nanostructured polymer blend consisting of polycarbonate (PC) minor phase, a polypropylene major phase, and a surface-active compatibilizer (i.e. PC grafted onto mPP polypropylene backbone) has been reported. The current method showed that PC can be dispersed in a nanostructure of an average diameter of 150 nm. The crystallization behavior of the mPP in the blend was strongly accelerated unexpectedly by the in situ polymerization/compatibilization reaction.

Failure Analysis and Failure Prevention of a Floating Device
J.L. Spoormaker, Kirill Kavelin, May 2005

Saving keys that dropped in water is possible with a device to which keys are attached. It has a built-in float, which is activated when the product drops in water. The float launches itself up on a line of about 12m and appears back on the surface. The float is snap-fitted in the inner housing of the product and has a little sponge between the case and the float. When the device drops in water, the force exerted by the wetted sponge should be sufficient to disconnect the snap-fit assembly. The device is shown in Figure 1.Major mistakes have been made in design and material selection: a very stiff snap-fit construction and Nylon 6 as material for the float.Problems with the device arose, shortly after the developer had sold his company after a successful introduction during a water sport exhibition. The first summer after the transfer of the company was very humid and hot. When tests were carried out during the summer the majority of the floats could not be pushed out the inner housing.This was the reason for a civil court case, which lasted two years. The situation with the device was so complicated for the judge that he asked me as an expert witness to assemble a few products. I had to do this with both parties and I was completely free to determine the testing of the products in order to determine if the device was reliable enough.The paper describes all the analysis work for determining the reliability. It also describes how failure could be prevented by selecting a material that absorbs less moisture than Nylon 6 and by decreasing the stiffness of the snap-fit construction.

Extruded Open-Cell Foams Using Two Semi-Crystalline Polymers with Different Crystallization Temperatures
Patrick C. Lee, Jin Wang, Chul B. Park, May 2005

This paper presents an extrusion-based open-cell foaming process with polypropylene (PP)/metallocene polyethylene (mPE) and PP/low-density polyethylene (LDPE) blends. The basic strategy for achieving a high open-cell content is to induce a hard/soft melt structure using two semi-crystalline polymers with distinctively different crystallization temperatures (Tc), and to foam this non-homogeneous melt structure with supercritical CO2. The effects of polymer blending, die geometry, and temperature on cell opening were investigated in this study.

Penetration and Residual Scratch Depth in Reduced Coordinates: Comparability of Results
Witold Brostow, Moshe Narkis, Oscar Olea-Mejia, May 2005

The scratch resistance was studied for several types of polymers: polystyrene (PS), styreneacrylonitrile (SAN), polyamide 6 (PA6), polyethersulphone (PES), polypropylene (PP), polysulphone (PSU), Santoprene® and Teflon®. Sliding wear was determined by performing multiple scratch tests were performed at different normal forces. Two new variables are introduced; reduced penetration depth and reduced residual depth in order to relate scratch test variables to Young’s modulus. Except for the elastomer Santoprene, all other polymers show similar values (the same order of magnitude) of the reduced penetration depth. Our reduced coordinates allow to recognize three types of polymers: brittle, viscoelastic and semiductile and highly elastic materials.

Surface Modification Techniques for Optimizing Adhesion to Automotive Plastics
Rory A. Wolf, May 2005

Automotive plastics with a low polarity, such as PE, PP, TPO, POM, PUR and PTFE typically require surface treatment when decoration is required. Metallic surfaces may also require cleaning to remove low molecular weight organic materials prior to decoration. Once the above-mentioned interior and exterior grades of substrate surfaces are cleaned and activated, printing, gluing and painting are possible without the use of adhesion-promoting primers. This paper describes the latest innovations in three-dimensional surface treating technology for plastics finishing which address the need to advance adhesion properties, increase product quality, and achieve environmental objectives within the automotive industry. These innovations include advanced thermal and non-thermal discharge treatment processes for raising the polarity of surfaces to be painted, bonded, decorated, laminated, printed or to have tape applied.

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