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.
A numerical simulation using a meshless method is developed to describe the cooling of injection molded slits of different thicknesses with an improved thermal diffusivity model that considers the effect of cooling rates and processing conditions. For the filling phase, the fountain flow effect is taken in account. Numerical results are analyzed by examining the effects of the traditional and improved thermal diffusivity model. The predicted effect agrees well with previous measured data. For the case studied in this paper, the use of the traditional model results in a temperature underestimation.
Heat seal technology is an essential technique for intermediate packaging material for various industries. There are different kinds of sealing technologies, which would be selected for suitable heat sealed properties of the film. Heat sealing technique is conventional technology for heat sealed film by control temperature, pressure and dwell time. The conditions of heat sealed are important for controlled peel strength and heat sealed properties of the film. Furthermore, film strength depends on the drawn ratio and molecular orientation of film. However, the heat sealing ability of higher molecular orientation films are poor due to loss the heat sealing energy for relaxation of oriented molecules in polymer films. Therefore, it is very important to investigate the relationship between heat sealing conditions, molecular orientation, and higher order structure in polymer films on properties of heat sealed film. In this study, cast polypropylene (CPP) film was heat sealed by using heat sealing technique. The heat sealed condition was set at heat sealed time of 0.1 second with pressure of 0.2 MPa at various heat sealed temperature of 145 to 150 °C. The difference of higher order structure of these films was discussed on the basis of results of micro-Raman spectroscopy, FT-IR spectroscopy, DSC and peel test. From the result, it was found that higher order structure of PP films at heat sealed parts depends on heat sealing time, temperature, and drawn ratio of PP films.
Recycled PET (RPET) is known to exhibit brittle behavior in the presence of notches. Therefore, we tried to improve the toughness and other properties of RPET by incorporating E-GMA, talc filler and engineering plastics as an impact modifier and talc to increase the rigidity and heat distortion temperature of RPET. As a result, these blends with E-GMA exhibited significantly higher stiffness and strength especially with increasing E-GMA content. In addition, these blends with talc filler indicated the high heat distortion temperature due to increase the crystalinity of RPET blends. Therefore, it was found that talc played an important role in enhancing the heat resistance of RPET. Some injection molding parts, i.e. tray, chopstick, and so on, were produced from these compound materials.
In this study we have developed “dry-less pellets”, which absorbs less moisture and do not require additional drying prior to molding. The developing technique namely “Hot Air cooling System” involves coolinging the strands slowly with hot air on a metal conveyor. This study was carried out to clarify a relationship between moisture absorption fraction and crystalline structure of dry-less recycled poly(ethylene terephthalate) (RPET) pellets. Two diffent cooling systems of extrusion processes were performed including water cooling method and hot air cooling syatem. The effect of hot air cooling temperature on properties of RPET pellets was investigated. Karl Fischer moisture titration, differential scanning calorimetry (DSC) and density measurement were used to characterize the pellets to determine the structures of the dry-less pellets. From the results, we have succeeded for preparing the “dry-less pellets” by controlling the hot air cooling temperature condition in the extrusion process. The crystallization process of RPET pellets is an important characteristic for the “dry-less RPET pellets”.
It is not uncommon to see a 25-30% post-consumer recycled (PCR) content in a carbonated soft drink (CSD) PET bottle on the market. With the growing availability of PCR resin, food and beverage brand owners are pushing for higher recycling content in their packaging. Recent studies have been published showing that high-recycling-content in PET packaging will adversely affect the performance of pressurized bottles when compared to virgin material or low-recycling-content counterparts. However, little has been done to quantify the degradation of the specific material properties that govern pressurized bottle performance. This paper focuses on quantifying changes in the short- and long-term material properties that govern a bottle’s ability to retain its original shape when subjected to sustained carbonation pressurization. This performance attribute is typically characterized as ‘thermal stability,’ which is the ability of the package to retain its shape and molded-in feature definition over time, after pressurization. Two commercially available packages, one molded of 100% recycled PET and another molded of typical PET (30% recycled PET content), are used to extract the test samples. The study indicates that the effect of the high-recycle-content on the CSD PET bottle cannot be over-looked. The results of the tensile tests show that the 100% recycled PET is stiffer and tougher in the axial direction (up to 26%), but softer and weaker in the hoop direction (up to 14%), compared with its typical PET counterpart. Based on the creep test results, the 100% recycled PET also creeps 50% faster. This will have a noticeable effect on the bottle’s thermal stability, which is only 1-2% (height and diameter growth or contraction under carbonation pressure) for most commercial packages on the market. The effect will become more pronounced for non-cylindrical designs or designs with non-cylindrical features. Failure to adequately retain the bottle’s shape (thermal stability) will a
Pennycress press cake (PPC) is evaluated as a bio-based fiber reinforcement. PPC is a by-product of crop seed oil extraction. Composites with a high density polyethylene (HDPE) matrix are created by twin screw compounding of 25% by weight of PPC and either 0% or 5% by weight of maleated polyethylene (MAPE). Tensile, flexural, and impact properties are assessed from injection molded test specimens. An improved PPC bio-filler was produced by solvent treating PPC (STPPC). Composite blends composed of STPPC were superior to their PPC counterparts. Composites made with STPPC and MAPE had significantly improved tensile and flexural properties compared to neat HDPE.
Engineering plastics are generally used for parts in the path of hot water in a water heater and a domestic co-generation system. In this research, the long-term performance of short glass-fiber or long glass-fiber reinforced mPPE, and short glass-fiber reinforced PPS were investigated for thermal resistance due to hot water immersion and hot air exposure. The acoustic emission analysis was also conducted to investigate the cause of an initial change in mechanical properties by the bending test and the Izod impact test. As a result, the bending strengths of PPE and PPS after hot water immersion decreased due to degradation at the interface between a matrix resin and a glass fiber.
The ability of maleic anhydride grafted polymers to compatibilize non-polar polyolefin polymers with polar polymers or contaminants has been confirmed and publicized by a number of experts in the field. This study reports on a new generation of random copolymers of ethylene and anhydride functional monomers specifically designed for compatibilizing blends of polyethylene polymers with polar components (other polymers or additives) in mixed recycle streams. The results show that these copolymers, with a very high level of reactive functionality (>3% wt. of anhydride), improve the impact strength of molded or extruded part made from mixed recycle streams containing Polyethylene Vinyl Alcohol (EVOH) or Polyamides (PA) even when the scrap contains high levels of moisture, lubricants or other resins. Two practical examples are discussed: use in regrind layers of extrusion blow molded containers and use in recycling of mixed polymer streams to produce other parts.
A 3.048 m x 3.048 m (10’ x 10’) non-load bearing fire wall panel was tested for its fire resistance according to ASTM E119 standard furnace test. This fiber reinforced plastic (FRP) composite wall panel was found to have 1 hour fire resistance rating. A finite element model was developed to simulate the thermal behavior of the wall panel under the ASTM E119 conditions. COMSOL 4.3a Multiphysics finite element software was used to solve the time-dependent heat and mass balance equations to determine the temperature of the unexposed face of the wall panel. Excellent agreement was found between the results of the numerical simulation and data from the ASTM E119 test indicating the usefulness of the numerical methods in evaluating fire-resistance of structures.
In order to improve the conductivity of the molding fabricated with conductive-carbon-fiber-filled polymer composites, we investigated, using layer removal method, the distribution of the residual stresses of injection-molded conductive-carbon-fiber-filled polypropylene in this paper. Integrated effects of conductive carbon-fiber(CCF) orientation and its mass fraction at different positions on the residual stresses of the molding, we calculated the modulus of the molding sample using the classical laminate theory(CLT) of composites, and obtained the residual stresses distribution.
The co-rotating twin-screw extruder is a mixing vessel with a certain free volume. The actual filled volume inside the extruder is expected to change at different screw speeds and at different feed-rates. The screw configuration plays a role in the actual filled volume in the extruder. Hitherto, the precise determination of the filled volume, a matter of great importance to understand the process, was not practical. A method based on using Residence Time Distribution (RTD) to determine filled volume is developed and presented in the form of a simple block diagram. The changes in filled volume at different conditions become the basis for a mathematical model for the twin-screw extruder.
The processability and higher-order structure of thin-wall parts with ceramics filled polymer composites as a matrix polymer of poly(butylene terephthalate) (PBT) were investigated to produce new polymer composites with high heat diffusivity. Effects of boron nitride (BN) particles, aluminum oxide (Al2O3) and aluminum nitride (AlN) fibers composition and process parameters on processability, thermal property, and internal morphology of parts were discussed. Thermal diffusivity and thermal diffusivity increased concomitantly with increasing ceramic contents. In the case of AlN fiber, the thermal property was dependent upon the polymer and AlN fiber orientation. It is important to control the AlNorientation for improvement of heat-release characteristics. Overall, high processability and thermal properties were achieved using the polymer/AlN composites.
The vulcanization kinetics of EPDM is studied using Differential Scanning Calorimetry (DSC) method. An unusual endothermic peak is found over the range of temperature where the vulcanization peak (exothermic event) occurs. Therefore, this study uses a methodology based on Design of Experiments (DOE) to determine and analyze the effect of the different additives present on the compound considering four response variables: Number of peaks presented in the range of vulcanization temperature (between 90°C and 250°C), initial and final temperature of the vulcanization peak, and the value of the heat of vulcanization. This methodology can be extrapolated to thermoplastic and thermoset material and helps to determine in an economic way the thermal effect of additives on thermal processing variables.
Polyoxymethylene (POM) or polyacetal is an engineering thermoplastic resin that has been used for the past 50 years, primarily in injection molded articles. POM’s benefit is derived from its strength, stiffness, toughness, lubricity and inherent chemical resistance. This combination of properties has made standard POM a preferred material for applications involving fuel exposure — both in gasoline and diesel fuels. An innovative development has led to the introduction of plasticized POM, a material that has substantially increased flexibility and improved low-temperature performance versus standard POM. This paper details the properties of this new material and explores the performance of extruded tubing in different fuels.
Thermoplastic polyurethanes (TPU) offer high tensile strength, good low temperature flexibility, and excellent abrasion resistance. In this paper, we describe a novel route to prepare a crosslinkable TPU that can be processed with a conventional extruder. The extruded film can then undergo a photo-crosslinking step to yield a crosslinked material with enhanced heat and scratch resistance. This novel TPU combines the ease of processing of thermoplastics and excellent heat and scratch resistance of thermoset resins. It may be used as protection film in exterior and interior applications.
The corrosion resistance and diffusivity of Polyimide-b-polyurea copolymer coatings was significantly improved by the addition of polyurea, characterized by electrochemical impedance spectroscopy (EIS) in 3.5 wt% NaCl solution. The effect of polyurea on the damping ability of the coatings was studied by dynamic mechanical analysis (DMA). The hydrophobicity of coatings was determined by water contact angle. With increasing polyurea concentration, the corrosion inhibition, hydrophobicity and durability of coatings were remarkably enhanced, and the optimized copolymer was constituted of 50 mol.% polyurea. The incorporation of polyurea also decreases the damping ability due to the restriction of polymer chain motion by hydrogen bonding.
Light-emitting diodes (LED), as a new light source, are being used more and more as display backlight and general lighting. Due to the increase of brightness and electrical current of LED packaging (PKG), there are demanding requirements of LED reflector resins on heat and light stability. A high performance polyester poly(1,4- cyclohexylenedimethylene terephthalate) (PCT) compound has outstanding reflectance stability under heat and light, enabling medium power LED PKGs for applications such as backlight in LCD televisions. In this paper, a new PCT compound is discussed in detail in the context of a LED reflector resin, and performance compared with high temperature polyamide compounds. The processing conditions for injection molding are also discussed.
High-performance thermoplastics represent the most promising candidates for the adoption of engineering resins into high demanding applications. Hence, the fundamental understanding of their structure and its effect on their expected performance in critical environments is crucial for the development of new technologies and complex processing techniques. This study provides a detailed evaluation of the morphology of poly(etherketoneketone) (PEKK), focusing on the polymorphic behavior observed in these materials when subjected to controlled heat treatment. The results presented here offer a general overview of the morphological changes observed in these systems at elevated temperatures, providing insight on the expected performance of PEKK materials in high demanding applications. We anticipate that precise control over these morphological changes is critical for the successful introduction of PEKK and other high-performance engineering resins in applications such as aerospace and oil and gas exploration among others.
Polycarbonate and poly(acrylonitrile butadiene styrene) (PC/ABS) blends are the material of choice for automotive applications in both interior and exterior trims, largely due to the combination of easy processability and good physical/mechanical properties. Recently, there is an emerging trend for higher heat and higher flow materials in addition to existing stringent long term stability requirements. To respond to this market need, developmental efforts have been under way to formulate a PC/ABS blend which meets these requirements, and this paper shall address the various aspects of the same. The use of proprietary blends technology has led to the development of a solution that exhibits improved processing characteristics in terms of flow and superior mold release.
Low-density polyethylene (LDPE) is generally blended into linear low-density polyethylene (LLDPE) to improve the processability and optical properties of blown films. The miscibility between the blend components is one of the important factors determining the extent of improvement in these characteristics. In this study we developed a method to calculate the immiscibility index between different LLDPE and LDPE resins based on van Gurp-Palmen plots. An attempt was made to correlate the immiscibility index with the optical properties of the blown films.
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