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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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.
Influence of Cellulosic Filler Content and Morphology on the Drying and Processing of Polylactide Acid (PLA) Composites
This study examines the influence of different amounts of filler content and particle size on residual moisture in Polylactide Acid (PLA) compounds after drying. Also the influence of a hydrolysis stabilizer is verified. The measurement parameters for this study are the melt viscosity rate and differential scanning calorimetry. The results show a distinct influence of filler content and particle size on the residual moisture of the PLA compounds. An increase of both parameters leads to rising residual moistures. With increasing residual moistures, melt viscosity increased also. Due to the usage of an empirically determined formula, melt viscosity measurements of PLA compounds with varying moistures and filler content can be compared. The usage of the hydrolysis stabilizer caused a significant reduction of the melt viscosity of a PLA compound, while retaining the same residual moisture.
Engineering Resin Based on Post-consumer Recycled Polyamide 66 from Carpets
This study provides foundation for the development of a post-consumer recycle resin with low purity Post Consumer Recycle Polyamide 66 (PCR-PA66) and no delamination. These resin were developed using a novel concept of maximizing usage of low purity PCR-PA66 while maintaining part functionality. Main impurities in the PCR-PA66, which are calcium carbonate, latex, polypropylene, colorants and additives need to be taken into consideration to come up with a robust product. From these contaminants polypropylene (PP) present in the carpet backing and carried over in the PCR-PA66 stream causes serious potential for delamination and will be discussed in depth. A fixed amount of glass reinforcement provides part functionality, and total aim reinforcement was targeted to 36%. Delamination test was developed and this study aimed to uncover how to predict, measure and avoid potential of delamination while maximizing usage of low purity PCR-PA66. This paper describes the properties of optimized resins and boundary regions.
Effects of Gamma Sterilization on Low Density Polyethylene Film
Low-Density Polyethylene (LDPE) films were exposed to gamma irradiation at exposure levels of 40 kGy and 80 kGy. Virgin pellets, 0 kGy, 40 kGy, and 80 kGy films were then tested for melting behavior, crystallization behavior, secondary thermal transitions, complex tensile modulus, and molecular weight. Modulated Differential Scanning Calorimetry (mDSC) and standard DSC were used to characterize the thermal performance and Dynamic Mechanical Analysis (DMA) was used to characterize the complex modulus. GPC was used to characterize the molecular weight.
In this case, small changes in the thermal and modulus mechanical properties were found at 40 and 80 kGy irradiation levels. However, at the same time large increases to the molecular weight were observed. The antioxidant concentration was found to be relatively stable at these gamma irradiation levels. Although additional stress-strain behavior is needed for full validation, overall the LDPE film studied here offers excellent resistance to gamma sterilization. But even for this LDPE, gamma irradiation does have a significant effect on the structure in terms of defect incorporation, chain scission, and crosslinking. This study supports the understanding that it is critical to verify performance as a function of irradiation dose for new formulations, grades, or polymer chemistries of medical-grade polymers.
Linear and NonLinear Rheology of Poly(Butylene succinate)/Fumed Silica Nanocomposites
In this work, the role of shear deformation on the microstructure of nanocomposites formed by compounding poly(butylene succinate) (PBS) with neat and surface functionalized fumed silica is explored by melt state rheology. The rheology results uncover a unique structural evolution from shear start-up in nanocomposites, including formation of a physical network under steady shear. The linear viscoelastic responses show that the shear-induced network can result in increased elasticity and a second shear thinning regime at low frequency. The materials compounded with hydrophobic organically modified silica display shear-induced reinforcement at lower particle loadings than those with hydrophilic fumed silica. These results indicate that reinforcement in nanocomposites can be controlled by filler surface functionality and shearing effects. This method enables improved mechanical properties with low filler loadings.
Effects of Shear and Extensional Flows on the Electrical Properties of Polycarbonate/Carbon Nanotube Composites during Injection Molding
Electrically conductive composites made from polycarbonate (PC) and two different types of carbon nanotube (CNT) were compounded and subsequently molded in order to glean effects of the injection molding process on the electrical properties of the materials. A typical multiwalled CNT and a highly branched, crosslinked CNT were investigated to determine the effect of initial nanotube morphology. All composites were molded through three geometries: shear dominated, mixture of shear and extension, and extension dominated. It was determined that the initial nanotube morphology was the largest contributing factor to the final electrical properties of the composites.
Toughness Study of Center Cracked Polypropylene Films with Temperature Effect
The manufacturing of a cast film with high orientation has little forgiveness for imperfections embedded within the polymer web. Imperfections such as gels, dirt and other contaminants can lead to web breakage and hence downtime which affects productivity. In this study, the effect of defect size on the failure of a web is studied using a model system that simulates the defect by a slit crack. The toughness of the film can be assessed as a function of defect size. In this study, polypropylene (PP) cast films were used for this investigation and the toughness is determined using an MTS Sintech Tensile tester.
Our test results showed that un-notched PP homopolymer films exhibit fully ductile behavior at both temperatures, 23øC and 40øC. However, increasing the center crack length resulted in decreased in toughness and at above 3 mm in crack length, the PP cast film failure mechanism changed from fully ductile to brittle like failure.
Development of Crosslinked Polyethylene by Using a Tin-Free Silane Cocktail
A linear low density polyethylene was crosslinked using a vinyl cyclic alkoxy silane, initiator, and non-tin catalyst. At first, silane cocktails were developed by mixing vinyl cyclic alkoxy silane, initiator, anti-oxidant, and various non-tin catalysts. Next, using such silane cocktails, a series of crosslinked polyethylenes (XLPEs) were produced. The mechanical properties and extent of crosslinking of resulting XLPEs were compared to those of a XLPE produced by using dibutyl tin dilaurate as a catalyst. The result indicated that cyclic silane cocktails containing non-tin catalyst can effectively crosslink the polyethylene.
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