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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Effects of Gas Counter Pressure and Dynamic Mold Temperature Control on the Mechanical/Foaming/Surface Roughness Properties of Microcellular Injection Molded PP Parts
This study investigated the effects of the gas counter- pressure technique (GCP) and dynamic mold temperature control (DMTC) on the mechanical/foaming/surface roughness properties of microcellular injection molded Polypropylene (PP) parts. In the gas counter-pressure technique nitrogen fills up the cavity during the injection molding process. This can delay the foaming process and affect the microcellular injection molding process. The results showed that the tensile strength decreases with the counter pressure and increases as holding time is increased, while the flow length decreases as the holding time increases. The cell size decreases as the holding time increases. The surface roughness is improved by the foaming PP with high DMTC.
Systematic Determination of Parameter Influences on Wall Thickness Distribution for the New Special Injection Molding Process Direct GITBlow
The special injection molding process GITBlow, developed by Polymer Engineering Paderborn (KTP), combines the established processes gas-assisted injection molding and blow molding. With GITBlow large, thinwalled hollow space geometries can be created. The preform is produced via gas-assisted injection molding and is then further inflated via a second gas injection. In this study the influence of the varied parameters on the temperature distribution in the preform wall are analyzed. Subsequently a guideline is developed for the approximate optimization of material specific operating points, especially concerning the required parameter settings for the first gas injection.
Effects of Cycloalkylcarboxylic acid Derivatives as Coadsorbents on the Photovoltaic Performance of Dye-Sensitized Solar Cells
Effects of cycloalkylcarboxylic acid derivatives as coadsorbents on the photovoltaic performance of D908 dye sensitized nanocrystalline TiO2 solar cells were investigated. Cyclopentylacetic acid (CPAA) coadsorption was revealed to improve both the photocurrent and the photovoltage of the solar cells.
The improved photocurrent was probably due to suppression of self-quenching of the excited electrons in the dyes by coadsorption of CPAA on the TiO2 and increased the electron-injection yields from the dye to the TiO2.The improved photovoltage was probably due to suppression of recombination between the injected electrons and I3- ions on the TiO2 surface.
ATR-FTIR spectroscopy indicated that CPAA coadsorption increased the content of bound dye on the TiO2 surface. This result suggests that CPAA coadsorption improved the photocurrent of the solar cells.
New Hydrogenated Styrenic Block Copolymers for Compounding Solutions
Two new hydrogenated styrenic block copolymers of the poly(styrene-b-ethylene/butylene-b-styrene) or SEBS type, MD6958 and MD6959, were designed with high molecular weight, enhanced rubber segment midblock and relatively higher polystyrene content. MD6958 has the same molecular weight as G1633, the highest molecular weight grade produced by Kraton Polymers. The enhanced rubber segment midblock means that both polymers contain higher butylene content in the midblock than other traditional SEBSs such as G1651 and G1633. Polystyrene content is 35% for MD6958 and 40% for MD6959, respectively. This paper reports the characteristics of these polymers and properties of their compounds with oil and polyolefin. The high melt flow, decent high temperature performance and low hardness of their compounds open up new formulating opportunities to solve challenges faced by applications requiring both good processibility and excellent high temperature performance.
Compatibilized Polyetherimide and Polyarylene Sulfide Blends
Polyetherimide and Polyarylene sulfide resins are high performance thermoplastics; both are characterized by excellent combination of properties but are also deficient on few. Their blends are expected to overcome the shortcomings of the individual resins. Unfortunately, they form incompatible blends with phase separation and delamination with little or no phase interaction between the two phases which will result in reduced properties. In this report, compatibilized blends of amorphous polyetherimide, thermoplastic polyimide (TPI) and polyetherimide-siloxane copolymer resins with semi-crystalline polyarylene sulfide resins are described which offers excellent mechanical properties, thermal resistance and chemical resistance, suitable for many high temperature applications.
Synthesis and Characterization of Biopolyesters from Refined Crude Glycerol and Succinic Acid
The synthesis of biopolyesters based on refined crude glycerol and succinic acid was studied aiming to determine the influence of the molar ratio of reactants (glycerol to succinic acid) in the extent of reaction and main physic chemical properties of the products. Industrial crude glycerol refined up to 96 wt% glycerol content was employed as monomer for the synthesis along with succinic acid and the reaction was stopped before reaching the gel point in order to obtain non cross-linked products. These polyesters were characterized by gas chromatography, FTIR and thermal gravimetric analysis. It was shown that the molar ratio of reactants employed determines the amount of unreacted monomers present in the final product.
Synthesis of Lignin Based Carbon Particles and Their Performance as Fillers in Bionanocomposites
Bioethanol lignin based carbonaceous powder was prepared using carbonization and ball milling optimization to provide a material that may be used as a substitute to carbon black. The resulting carbon powder showed greater surface area and thermal conductivity to carbon black with particle sizes around 1 micrometer. The carbonized ball milled lignin was then compared against commercial carbon black as filler in the formation of thermoplastic composites. The lignin based carbon filler was able to perform similarly to carbon black by increasing the thermal conductivity but no enhancement in the electrical conductivity was evident for the biobased filler.
Impacts of Different Mechanisms on Carbon Nanotubes/ Polymer Nanocomposites? Piezoresistivity
Superior electrical conductivity and extremely high aspect ratios of carbon nanotubes (CNTs) have made them effective filler to fabricate electrically conductive polymer nanocomposites (PNCs). Through disruption of the CNT conductive network, variation in the tunneling resistance among CNTs, and piezoresistivity of CNTs, PNCs also exhibit piezoresistivity for strain sensing applications. In this work, an improved three-dimensional CNT network model has been extended to investigate the piezoresistive behaviours of PNCs. Simulation results demonstrated good agreement with various experimental measurements. Subsequently, numerical studies were conducted to elucidate the impact of each mechanism on PNCs? macroscopic piezoresistive responses to external strain.
Process Planning of Mold Components with Feature Recognition and Group Technology
The machining process of plastic injection mold components is complex and continuously changing, and traditional practices rely on the experience and technique of professionals. In order to avoid the impact on business operations and losses, the geometric information of computer-aided design (CAD) systems should be converted into the manufacturing system required for computer-aided process planning (CAPP) and computer-aided manufacturing (CAM) systems through the integration of automatic feature recognition and group technology; thereby eliminating manual planning and shortening the planned lead time to realize CAD/CAPP/CAM integration and application. As part design is feature-based, each processing step can be regarded as a feature. This study applied hybrid recognition technology integrating the graph-based approach, rule-based approach and hint-based approach to analyze and identify injection mold component shape features. Then, it established classification coding for data description according to the injection mold components before searching for the corresponding manufacturing processes in the database using the group technology. The case proved that the CAPP in this study could reduce about 90% of the working time needed. It could accelerate the component planning process and integrate with the mold manufacturing scheduling to realize automated design and manufacturing.
Thermal Analysis of Conventional and Rapid Tooling for Injection Molding
The thermal behavior of inserts manufactured via rapid tooling was compared to conventional machined inserts. Machined T-420 stainless steel, direct metal laser sintered bronze and jetted digital-ABS photopolymer inserts were studied. Full 3D models of the inserts, part, and mold geometry were created and analyzed via computer simulation of the process. The thermal gradients and their effects on the part geometry (shrinkage and warpage) were studied for each set of inserts. The thermal properties of the inserts were found to have a significant impact on the processing variables and the part quality. The results showed that the digital ABS inserts present the greatest variance in part dimensions, as well as the highest temperature gradients.
Effect of Polypropylene Contamination on Weld Strength of Recycled Polyamide 6
Two different recycled polyamide 6 resins were used in this study: post-industrial waste polyamide 6 (PIW) obtained from a fiber manufacturer; and post-consumer waste polyamide 6 (PCW) recycled from used carpets. Differential scanning calorimetry (DSC) and Dynamic mechanical analysis (DMA) proved the presence of polypropylene (PP) in PCW. Moreover, thermal gravimetric analysis (TGA) showed that PCW contained approximately 10 times more ash content than that of PIW. The PP and inorganic contamination of PCW come from PP carpet backing and calcium carbonate (CaCO3) filled latex binder, respectively . Due to higher inorganic filler content, PCW exhibited higher melt viscosity and also higher storage modulus than that of PIW. Tensile tests were performed on dog-bone specimens cut from injection molded plaques. PIW displayed approximately 20% higher tensile strength than that of PCW. However, a 70% drop in PCW vibration weld strength was observed. This is attributed to its PP contamination.
Highly Filled Thermoplastic Elastomer Compounds Made with Olefin Block Copolymers
Highly filled compounds are used in a variety of applications, from wiring to flooring to sheeting applications. Maintaining flexibility and mechanical strength at higher filler loadings can be a challenge with traditional random copolymer thermoplastic elastomers (TPEs). Olefin Block Copolymers (OBCs) enable the manufacture of highly filled TPE compounds that are flexible, maintain physical properties, and have improved heat resistance over other random copolymers. The high density polyethylene hard blocks provide mechanical strength and temperature resistance, while the low-density soft segments enable high filler loading. Improved property retention at high filler loading levels and after heat aging are achieved as compared to compounds made with random copolymer ethylene/à-olefin polyolefin elastomers (POEs).
The Influence of Blend Composition and Additive Type on the Properties of LDPE-PA6-Blends
The aim of this work was to investigate the effects of the composition on the properties of LDPE-PA6 blends with an emphasis on the addition of EVA, because this material is often used as interlayer in packaging films. Furthermore, also the effects of additional compatibilization on the blend properties should be investigated.
We found, that the addition of EVA alone shows some compatibilizing effects in blend properties, like impact strength and viscosity. Further improvements can be gained by adding prefabricated additives, like maleic anhydride grafted polyethylene and ethylene vinyl acetate, while the in situ production of such additive shows some reduced effects, likely due to some reduced accessibility of the EVA component for the in-situ grafting. Nevertheless all the investigated approaches show some effectiveness in compatibilisation, which will help to re-use such materials in other applications
Evaluation of Plastic Pipes for Hot Water Supply and Heating
In this paper, plastic pipes such as PEX and PE-RT for heating and hot water supply were tested by the hot water circulation at the average pressure of 0.2 MPa at 110 øC, the stress rupture at the pressure of 0.2 MPa at 110 øC and the simple hot water immersion and hot air exposure at 60, 80, 100(98), and 120 øC for 7000 hours or more. There were some failures for PE-RT pipes in hot water circulation and stress rupture tests. The tensile test for dumbbell specimens cut out from a pipe after hot water circulation, stress rupture, hot water immersion and hot air exposure was conducted to evaluate the effect of hot water flow in a pipe and applied pressure to a pipe. The yield stress increased and the elongation at break decreased for plastic pipes due to increment of degree of crystallization after hot water circulation, stress rupture, hot water immersion and hot air exposure. There was a rough degradation layer at the inner surface after hot water circulation for PEX and PE-RT pipes for 7000 hours. The initial oxidation temperature (IOT) at the inner surface and the middle of a pipe after hot water circulation was also measured to evaluate remaining antioxidants. As the IOT decreased at the inner surface of a pipe after hot water circulation, it was found that antioxidants were deactivated and eluded into hot water.
New Fields of Applications for the Design of Experiments (DoE) in the Development Process for Medical Products
The product development process can be divided into the following phases: Planning-, Concept-, Development-, Elaboration- and Product Optimization Phase . Especially in the development-, elaboration and product optimization phase, the statistical experimental design can support the development process of medical products considerably. In practice however the tool of the Design of Experiments (DoE) is in most cases only used in a limited area of the development process. Consequently the qualification of injection molds is increasingly planned, analyzed and documented with the help of a DoE. However, the statistical experimental design not only provides benefits for the qualification of production tools. Because a DoE can already be utilized in advance and after the start of series production, in order to analyze and optimize product and process features. In this work new scientific approaches are demonstrated, how the statistical experimental design can be utilized profitably in the entire development process of medical products. This first-time compilation has been implemented in our own work and successfully tested in practice.
Modification of Interfacial Bonding of Hybrid Glass/Carbon Fiber Polypropylene Composite Fabricated by Direct Fiber Feeding Injection Molding
The modification of interfacial bonding between carbon fiber (CF) and polypropylene (PP) in hybrid glass/carbon fiber reinforced polypropylene composites fabricated by direct fiber feeding injection molding were studied. Polyamide 6 (PA6) and maleic anhydride grafted polypropylene (MAPP) were selected as the coupling agent for carbon fiber and polypropylene. The bonding between CF and PP was not improved by the addition of PA6. The using of MAPP as coupling agent showed small improvement in interfacial bonding between CF and PP. The using of PA6 and MAPP as co-coupling agent significantly improved the interfacial bonding between CF and PP. In addition, the amino silane treated on the surface of carbon fiber further improved the bonding between carbon fiber and the co-coupling agent as compared with as-received carbon fiber.
Advances in 1D & 2D Layer Multiplication Coextrusion for Film and Non-Woven Fiber Applications
Polymer processing techniques utilizing a sequential layer multiplying die coextrusion approach to (1) produce nanolayered films from less than 100 gram batches of materials or (2) coextrude micro- or nanolayered 2D layered film architectures are described. A ?plug flow? process approach that eliminates the need for time consuming and costly kilogram scale-up of developmental polymer materials prior to development extrusion process trials was demonstrated through coextrusion of cast 350 mm wide x 30 meter long, 4,097 layer films from an 80 gram sample of custom synthesized fluoromethacrylate polymer layered against a commercial polymethylmethacrylate resin. Modifications to the conventional coextrusion process have also enabled the continuous production of two, three, or four component 2D layered structures with up to 64,000 ?layers?. A series of 2D multilayer processing trial results are discussed that demonstrate an ability to process millimeter, micron, or nanoscale 2D ?layer? thicknesses in model polypropylene/polyamide/polystyrene system for use as fibrous, non-woven mats.
Study of Sealed Parts of Fluorine Film by Laser Advanced Welding of Plastics Method
In this investigation, we demonstrate the film sealing by using LAWP method and try to evaluate the mechanical properties and internal structure of sealed parts on the basis of the results of peel test, optical microscope, and micro-Raman spectroscopy. As a result, it was found that the sealing for FEP films became completely more than or equal to about 10 W of laser irradiation power, although at more than 12 W, the small voids are observed around the film interface by using an optical microscope. Therefore, the irradiation laser power about 10 W is the most suitable value to get the good sealing of FEP films in this investigation. Moreover, it was found that the molecular orientation of FEP films was decreased with increasing the irradiation laser power by using micro-Raman spectroscopy. We consider that it is very important to investigate the relationship between the sealing properties and the interfacial structure in films.
Wall Thickness Distribution of Continuous Glass Fiber Reinforced Polyamide 6 Composite Parts Formed by Gas Pressure
Because of the uneven pressure distribution, stamp forming of thermoplastic composites leads to a non-uniform wall thickness distribution within in the part. The Twin-O-Sheet Process uses gas pressure without extra diaphragms to shape the thermoplastic composite parts. Compared to a stamp, the gas distributes the pressure uniformly over the whole part during the forming process. The wall thickness distribution of parts produced by the Twin-O-Sheet Process was measured using two different methods. Unlike the general wall thickness distribution of stamp formed parts, no thinning in the apex points could be determined. While the process parameter gas injection time and the fiber orientation of the laminate show only little effect on the wall thickness distribution, the mold design, especially the blank holder area has a great influence.
Aging Behavior of Polyamide 12 during Selective Laser Melting Process ? Influence on Mechanical Properties
Selective laser melting is a well-established manufacturing technique in prototype construction. In recent years a tendency to rapid manufacturing applications and the production of ready to use components with this technology can be observed. If components made by laser melting are desired to be applied in technical series products, their achievable properties play a major role. The high process temperatures in combination with long build times during laser melting process lead to chemical and physical aging mechanisms on the polymeric feed material. The unmolten partcake material, which acts as a supporting structure, can be removed after each building process and reused for further processes. To achieve part properties which endure the necessary mechanical loads, refreshing of partcake powder with 30 up to 50 % by weight virgin material is necessary. However, constant refreshing strategies will lead to varying component properties due to an undefined aging state of the basic partcake material. Therefore, a fundamental understanding of the correlation between the feed material aging state and resulting mechanical properties is alienable.
This paper deals with the analysis of the relationship between the aging state of the feed material focused on rheological behavior, mechanical part properties and deformation behavior. Therefore, polyamide 12 powder is used for at least five processing cycles without refreshing. Before and after each build process, bulk and material characteristics like bulk density, hausner ratio, viscosity number, melt volume rate and average molecular weight were determined. Tensile tests were conducted in order to study the mechanical material and deformation behavior. Finally, mechanical behavior as a function of feed material can be evaluated. On this basis, powder life cycles in dependency of mechanical properties can be derived.
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