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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CHAIN EXTENSION OF RECYCLED POLYAMIDES : HOW TO INCREASE THE AMOUNT OF RECYCLED PA IN THE AUTOMOTIVE INDUSTRY
The present work attempted to implement reactive compatibilisation of blends of recycled engineering plastics, more particularly the case of recycled PA66 contaminated by recycled PA6. Low molecular weight, high Tg Styrene-Maleic Anhydride copolymers were tested as chain extenders / compatibilizers. It appeared that the addition of 2% by weight of SMA to an incompatible system of recycled PA6 and PA66 improved both ductility and impact performance by factors of at least 10 and 1.5 respectively. Moreover, high Tg SMA improved performances at elevated temperature, partly due to its ability to effectively crosslink but also because of its inherent heat resistance.
THICKNESS PROFILE EFFECTS ON THE BUILD-UP PROCESS OF FILM-ROLLS IN THE WINDING PROCESS
A high percentage of today’s blown-film-extrusion-machines is equipped with a reversing system. The reversing draw-up unit is supposed to rearrange tolerances of the thickness profile on the film-roll within the winding process. Most process setups in the blown-film-extrusion production have a standardized reversing speed or do not use the reversion. A new simulation model developed at the University of Duisburg-Essen can show the critical effects of these setups in the build-up of film rolls and links them to detected defects in today’s production.
CARBON NANOFIBER/POLYETHYLENE NANOCOMPOSITES FOR ESD AND EMI APPLICATIONS
Vapor grown carbon nanofiber (VGCNF) / High density polyethylene (HDPE) conductive nanocomposites were prepared by melt mixing. The nanocomposites electrical and electromagnetic (EMI) shielding properties were studies as function of filler concentration. The electrical resistivity of 1.5 vol% VGCNF/HDPE nanocomposite was 105 Ohm-cm indicating that this nanocomposite is suitable for electrostatic discharge (ESD) protection applications. In the 0.1-1.5 GHz frequency range, 2 mm thick plates made of HDPE filled with 5 vol% VGCNF showed an EMI SE of 20 dB, this level of attenuation is adequate for laptop and desktop computers shielding.
FEA SIMULATION STUDY ON DESIGN OPTIMISATION OF MOULD FEEDING SYSTEM FOR PRECISION MICRO MOULDING OF POLYMERIC MICROFLUIDIC CHIP
Moulding of micron features is a pre-requisite for manufacturing of polymeric microfluidic chips. The final quality of moulded microfluidic chips could be affected by the various types of design factors in a mould feeding system. In this paper, two design factors, notably the gate location and gate type, are extensively evaluated through finite element analysis (FEA) simulation to investigate how the melt flow behaviour of polymer could affect the quality of moulded microfluidic chips.
CROSS-LINKING OF HYDROGEL WITH A NEW WATER-SOLUBLE AGENT, DIISOSORBIDE BISEPOXIDE
Cross-linking of polymeric biomaterials has increased in interest over the last 5-10 years. One category of biomaterials is hydrogel, a chemically cross-linked network that swells when immersed in water. Dextran, a polysaccharide, can be crosslinked to form hydrogels that have found application as tissue scaffolds and delivery devices. In this study, dextran is cross-linked with diisorbide bisepoxide, a water soluble chemical cross-linker. The gelation temperature and gel time will be monitored using oscillatory rheometer.
NEW FULL DRY SYSTEM DEVELOPED FOR BI-ORIENTED PIPES BRINGS EXCELLENT OPPORTUNITIES FOR PVC-O
Systems that today exist for PVC-O piping are clearly defined in two: in-batch and in-line systems. In batch systems, stable, flexible, allowing high orientation degree and raw material savings, are at the same time not much efficient in terms of energy, labour, output, and are highly penalized by internal logistics. The development of new systems, based on air, improves dramatically energy & labour savings, speed and efficiency, allowing the integration in a standard extrusion line. The result is a stable and reliable process, highly profitable, working on a continuous way and getting efficiency of an in-line process.
THERMALLY BUTT-FUSED PVC PIPE AND THE EXPANSION OF TRENCHLESS INSTALLATIONS IN THE WATER AND WASTEWATER APPLICATIONS
The application of thermal butt-fusion joining technology to polyvinylchloride (PVC) piping has had a major impact on the waterworks market over the last seven years. The combination of a familiar, industry standard piping material with a joining method that lends itself to cutting edge trenchless installation methods has seen rapid expansion in application and use in the water and wastewater industries. Trenchless methods that involve the installation of a new pipeline, or ‘whole pipe replacement,’ include horizontal directional drilling (HDD), sliplining, and pipe bursting methodologies. These methods are characterized by the installation of a new pipeline or conduit that does not derive pressure capacity, strength, or design life from any previously installed or “host” infrastructure. Polyvinylchloride (PVC) pipe with the use of butt-fused PVC pipe technology has made great strides in these applications, due to its high tensile strength capacity, high hydrostatic design basis, good chemical compatibility, and abrasion resistance. The use of butt-fused PVC pipe has expanded the capabilities of thermoplastic pipe within these methodologies, allowing greater pull-in lengths, depths, and pressure capacities to be achieved. This paper will discuss the materials and technology that are allowing for this expansion as well as highlight the direct impact on the installation methodologies through several recent case study examples. Case studies will include a record setting horizontal directional drill for a water transmission main installation; a large diameter force main rehabilitation through the use of sliplining; and a pipe bursting replacement program for potable water distribution mains, all in North America. This information will illustrate the innovative nature of this joining methodology, flexibility and range of the current whole pipe replacement offerings, and demonstrate how they are growing in use as end users benefit from this unique application of PVC pipe.
MODELING AND ANALYSIS OF CURE KINETICS OF ALIPHATIC EPOXY RESIN WITH AND WITHOUT DIFFUSION
The curing reaction of an aliphatic epoxy resin is modeled from differential scanning calorimetry (DSC), using a methodology proposed by Hernandez-Ortiz and Osswald. The kinetics is represented by modified Kamal-Sourour model which includes the diffusion reaction control; the modeling uses a non-linear regression method and DiBenedetto’s equation for the diffusion part of reaction. The kinetic fitting methodology uses dynamic and isothermal differential scanning calorimetries for two different accelerator concentrations
NUMERICAL VISUALIZATION ON COOLING MECHANISM FOR CONFORMAL COOLING SYSTEM IN INJECTION MOLDING
In an injection molding process, cooling time usually dominates the whole cycle time. Therefore, decreasing cooling time can help save manufacturing cost. Cooling system design is one of a crucial factor to reduce cooling time. However, by using traditional molding manufacturing method, cooling system layout is restricted. For cavities with greater curvature, the distance between cooling channels and cavity may vary throughout the part. This causes local heat accumulation and hence worse product quality. By using some non-conventional methods such as laser sintering and 3D printing techniques, cooling channels can get closer to the cavity surface than using traditional method. The current study uses a true three dimensional simulator to predict the injection molding process and product deformation. The results from a conventional and a conformal cooling design were compared. The results also show flow behavior inside cooling channels which provide important indices for cooling efficiency improvement. With a shorter cycle time and better product quality, conformal cooling has a great potential in injection molding industry.
COMPOSITION-OPTIMIZED SYNTHETIC GRAPHITE/POLYMER NANOCOMPOSITES
In this study the optimization design, fabrication and characterization of synthetic graphite/phenolic nanocomposites are performed. The composition of synthetic graphite/phenolic nanocomposites was controlled across the thickness by stacking eight homogeneous layers containing 0, 5, 10, and 20wt% synthetic graphite in different sequences. Four compositional gradient patterns, as well as a homogenous nanocomposite, with the same geometry and synthetic graphite content, were fabricated to investigate the optimized design for thermomechanical properties. Results show that nanocomposites with a high concentration of synthetic graphite on the surfaces and neat resin at the center have the best thermomechanical and viscoelastic properties.
LASER WELDING OF INCOMPATIBLE SEMI-CRYSTALLINE THERMOPLASTICS BE MEANS OF INTERMEDIATE LAYERS
The weldability of dissimilar thermoplastics is restricted except for a few combinations using conventional welding processes for thermoplastics. Among these processes laser transmission welding is a relative new and innovative technology. The so called intermediate layer method is a new variant of the laser transmission welding which allows joining transparent plastic parts. This paper details with the enhancement of the intermediate layer method that leads to an improved weldability of dissimilar thermoplastics. Within the scope of a current research project the weldability of polypropylene and polyamide 6 using multi?layer films with a layer of an adhesion promoter can be demonstrated. Thereby, the film thickness is of particular significance.
EFFECTS OF MOLECULAR ORIENTATIONS AND RESIDUAL STRESSES ON THE ENVIRONMENTAL STRESS CRACKING STRESS CRACKING RESISTANCE OF POLYCARBONATE
Environmental stress cracking is the most common failure reason of plastic parts. The influence of the processing conditions has been investigated in a previous research project at IKV. Yet, it was not clear if these effects can be correlated with the molecular orientations or the residual stresses. Therefore the effects of molecular orientations and residual stresses on the ESC?resistance are analyzed. The results of these investigations are discussed in?depth.
USE OF SURFACE ENGINEERING ON MODERN PRE-HARDENED TOOL STEEL
During the last decade have modern pre-hardened tool steels been developed and introduced into the market. This has been enabled thanks to improved metallurgical techniques pertaining to make even cleaner steel, and also a rapid development in hard-machining enabling faster tool-manufacturing. The pre-hardened tool steels are usually delivered in hardness up to Approx. 380 HBW. Steels having higher hardness when delivered from the steel producer are not so common, but prehardened tool steel having 45 HRC has now been available on the market since a couple of years. Steel having hardness around 45 HRC are suitable in many molding applications. However, when molding glassfiber- reinforced plastics high mold surface hardness is required, otherwise would the mold life length be too short. Surface engineering (Nitriding, PVD-coating etc.) offer the mold designer to tailor-make mold surface properties for a specific application.
CONTRIBUTION TO THE DEVELOPMENT OF A VARIOTHERMAL PROCESS CONTROL FOR THE TWO-STAGE GITBLOW PROCESS BASED ON THE FINITE ELEMENT METHOD
The two-stage-GITBlow-process is a special injection molding process for the production of complex parts with local thin-walled hollow spaces. Wall thickness homogeneity is of major importance here to guarantee uniform strength of the hollow space geometry. In this paper, the process is simulated via the finite-element-method. The results on wall thickness homogeneity are verified with experimental findings. Finally, the application of variothermal process control is simulated and compared with previous thresholds of wall thickness homogeneity.
DEVELOPMENT OF A METHOD FOR THE LIFE-TIME DIMENSIONING OF SHORT FIBER REINFORCED PLASTICS
Short glass fiber reinforced thermoplastics are increasingly used as design material for technical plastic parts. Especially the life?time dimensioning gains increasing importance recently. At the IKV Aachen a method was developed that allows a calculation of the life?time with the help of Finite? Element?Analysis based on part?independent material Wöhler?curves. The method enables the transfer of the fatigue behavior that is determined once on a test specimen to part behavior by use of a suitable failure criterion.
EXTRUSION-CALENDERING OF FOAMED AND UNFOAMED WOOD/PLASTIC COMPOSITES
Foamed and unfoamed wood/plastic composites (WPC) were produced by extrusion-calendering. The effect of wood content on the foaming process was studied by using different amounts of wood particles (0, 10, 20 and 30%wt). The samples were characterized in terms of physical properties (DSC, morphology and density) and tensile behavior. The results show that extrusion-calendering leads to wood particle orientation in the composites and elongated bubbles in the foams, this orientation being stronger as wood content increases. The density was found to decrease by foaming, but increased with wood fibre content. According to SEM micrographs, the foamed composites presented a more homogeneous microstructure than unfoamed ones. From the tensile stress-strain curves, three parameters are reported and discussed: Young’s modulus, yield stress and strain at break. As expected, foaming decreased all the properties, while increasing fibre content led to higher Young’s modulus, but lower strain at break and yield stress.
MULTIVARIATE MODELLING, FAULT DETECTION, AND VALIDATION FOR THE EXTRUSION PROCESS
A tubing extrusion process monitoring system was implemented. The system incorporated Principal Components Analysis and Projection to Latent Structures multivariate models. A design of experiments was performed to train models using different sets of input and outputs. Validation experiments were then performed to evaluate the models’ capability to detect 18 process faults. Results indicate that Shewhart control charts of process variance and model residual errors are well suited for detecting faults in the extrusion process.
RELATION BETWEEN WATER PENETRATION BEHAVIOR AND PRODUCT QUALITY IN WATER-ASSISTED INJECTION MOLDING (WAIM) AT DIFFERENT PROCESS PARAMETERS
Measurements of water pressure and water volume flow rate during water injection were related to both the part weight and a visual inspection of part cross-section at different process settings. It was found that the residual wall thickness (RWT) as well as the formation of part defects depend on the polymer resistance, since the variation of this latter leads to a change in both the water bubble width and velocity. Therefore, product quality depends on process parameters such as water volume flow rate and water injection delay time, which have an influence on this polymer resistance.
CHAIN EXTENSION OF LOW VISCOUS PA 66 IN REACTIVE EXTRUSION PROCESS IN ORDER TO EXTRUDE THICK-WALLED PIPES
The aim of this study is to increase the complex viscosity of low viscous polyamide 66 (PA 66) by means of a chain extension process. The technical goal of the process is to extrude thick-walled pipes from chain extended PA 66 without the appearance of sagging problems. The influence of styrene maleic anhydride (SMA) and epoxide (EP) on chain extension of PA 66 were studied using a co-rotating twin- screw extruder. To evaluate the coupling effects of the different extenders on PA 66, the rheological and mechanical properties of the chain extended PA 66 were investigated. The extruded pipes, obtained from chain extended PA 66, featured a considerably improved wall-thickness distribution.
COMPARATIVE STUDY OF THE EFFECT OF NATURAL AND ARTIFICIAL WEATHERING OF POLYPROPYLENE / ETHYLENE VINYL ACETATE (PP/EVA) BLENDS
In this paper the effect of natural exposure and artificial weathering properties of PP/EVA blends was investigated. Different blends were compounded and pelletized using twin screw extruder. Then, ASTM standard samples were molded using injection molding machine. Naturally exposed samples were placed in the open air of Riyadh, Saudi Arabia for up to 7 months (from August to February). Whereas, the artificially weathered samples were exposed to UV radiation from a Xenon arc lamp at 65 °C for different times. The effect of weathering on the blends was evaluated via: Fourier transformation infrared (FTIR) analysis and Differential Scanning Calorimetry (DSC). The chemical analysis via FTIR showed that the intensity of the vinyl Acetate concentration decreased with exposure time due to acetylation. The most pronounced effect of radiation is associated with oxidative degradation which was concluded from the increase of corresponding transmittance bands located above 3000 cm-1. The crosslinking of PP/EVA blends attributed to the formation of vinylidene group. The thermal analysis via DSC illustrated that the melting temperatures of PP and PP/EVA (5%) noticeably decreased with exposure time. However, the melting temperature of PP/ EVA (20%) blend decreased slowly.
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