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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Hot Embossing of Micro-Featured Devices
Polymer microfabrication methods are becoming increasingly important as low-cost alternatives to the silicon or glass-based MEMS technologies. In this study, micro molding via hot embossing was applied to micro-featured used for DNA/RNA test. LIGA like process using UV light aligner was used to prepare silicon based SU-8 photoresist followed by electroforming to make Ni-Co based stamp. The micro features in the stamp with 5 inch diameter size and 0.2 mm thickness includes 30?m in depth by 100?m in width micro-channel size and 50?m pitch size. PMMA film of 1 mm thickness was utilized as molding substrate. Effect of molding conditions on the replication accuracy was investigated. The imprint width, imprint depth and angle of sidewall of micro-channels were analyzed and correlated. It was found that the molding condition including applied force and embossing temperature are found to all affect the molding accuracy significantly. The imprint depth increases with the imprint force until a saturation value. The imprint depth also increases with the embossing temperature until a saturation value. Basically, 20 kN and 180°C for applied force and embossing temperature can obtain acceptable results when considering molding cycle time. However, 25 kN and 220°C, respectively, under 5 minutes embossing time can obtain a nearly perfect replication in our experiment.
Effects of Molding Conditions on the Electromagnetic Interference Performance of Injection Molded ABS Parts with Conductive Fibers
Polymers filled with conducting fibers to prevent electromagnetic interference (EMI) performance have recently received great attention due to the requirements of 3C products. In this paper, effect of fiber content and processing parameters including melt temperature, mold temperature, injection velocity on the electromagnetic interference shielding effectiveness (SE) in the injection molded ABS polymer composites filled with conductive stainless steel fiber (SSF) was investigated. It was found from measured results that fiber content plays a significant role in influencing part EMI SE performance. Higher melt and mold temperature would increase shielding effectiveness due to a more uniform and random fiber orientation. However, higher injection velocity leading to highly-orientated and less uniform distribution of fiber reduces shielding effectiveness. SE value can reach highest values of approximately 40 dB, 60 dB and 72 dB at 1000 MHz frequency for fiber content 7%, 14% and 21%, respectively, if proper molding conditions were chosen. The result indicates that molding conditions are very important on the SE performance instead of fiber content alone.
Study on the Mechanical Properties of Injection Molded Nylon 6 Nanocomposites
In this study, the effects of the molding conditions including melt temperature (T), mold temperature (Tm), holding pressure (Ph), and injection speed (V) on the mechanical properties of injection molded nylon-6/fluoromica nanocomposites (Unitika) were investigated. With the additional of 5% nano-fluoromica particles, the tensile strength (?s) and flexural strength (Eb) increased and impact strength decreased as compared to those with of pure nylon-6 parts. The result also indicates that ?s and Eb of Unitika increased with T, Tm, Ph, and V. However, the impact strength of Unitika increased with T and Ph and decreased with increasing melt temperature and injection speed. The DSC measurement reveals that the crystallinity of Unitika increases with all molding parameters. SEM results also indicate the different fracture characteristics between pure nylon-6 and Unitika parts.
Development of Compression Moldable Thermoplastic Bipolar Plates
A method with the potential to produce economical bipolar plates with high electrical conductivity and mechanical properties is described. Thermoplastic composite materials consisting of graphite particles, thermoplastic fibers and glass or carbon fibers are generated by means of a wet-lay process to yield highly formable sheets. The sheets together with additional graphite particles are then stacked and compression molded to form bipolar plates with gas flow channels and other features. One of the key elements to the economical manufacturing of the plates is the minimization of the heating and cooling times. Various heating schemes are evaluated including induction, radiation, and resistance to determine how fast the composite preforms can be brought to the forming temperature and compression molded to give bipolar plates with well-defined channels. The electrical and mechanical properties of the plates were determined for several different compositions and two different polymer matrices.
3D Finite Element Modeling of the Blow Molding Process
In this work, both the heating stage and the blowing stage of the blow molding process are numerically modeled. The heat transfer between the infrared oven and the preform is modeled using a ray tracing method. The cooling fan effect is taken into account thanks to a forced convection coefficient. Regarding the blowing step, a Mooney-Rivlin hyperelastic model has been implemented in Forge3® software in order to account for the rheological behavior of the polyester. The numerical finite element model is based on velocity pressure formulation and tetrahedral elements. In order to validate the implementation of the hyperelastic behavior, computations are compared to Mooney-Rivlin analytical model results for tube free inflation. Finally, the global blow molding process of a PET bottle is studied.
Stress Cracking Caused by Hot Plate Welding – Theoretical Analyses
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
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
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
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
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
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
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
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.
Processing Highly Filled Pre-Compounded Pellets on Single Screw Extruders
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.
Stress Concentration Evaluation in an Injected Commercial Piece using Computational Tools
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
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
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
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
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
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.
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