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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Rheology of Polystyrene/Carbon Nanofiber Composites
Polystyrene/carbon nanofiber (CNF) composites with various CNF concentrations are prepared using melt blending and solvent casting techniques. Size and dispersion of the CNF are characterized using SEM, TEM, and optical microscopy. Linear and non-linear rheological behavior at elevated temperatures was measured to be very sensitive to the CNF aspect ratio, concentration and temperature. Orientation of the CNFs in shear and extensional flow is characterized using TEM micrographs in 2 perpendicular directions. A full 3D thermo-mechanical model is used to couple the rheology and the CNF orientation.
In-Line Monitoring of Polymer Compounding Process in a Twin-Screw Extruder
Experiments on in-line monitoring of PVC compounding process were performed with an ultrasound probe in a die. The effects of polymer melt pressure on ultrasound wave velocity and attenuation were discussed. A characterization method for polymer compounding was proposed based on the analysis of wave attenuation. The results showed that wave velocity was less dependent on melt pressure for all four PVC systems at constant die temperature, while the wave attenuation for PVC/PBA and PVC/DMP/CaCO3 systems showed slightly more dependence due to the scattering effect from existence of unmelted PVC primary particles or different dispersion levels of filler. Except the scattering effect, comparisons of wave attenuation between the four PVC compounds suggested that higher melt viscosity caused higher wave attenuation.
Modeling of Dispersed Melting Mechanism of PVC Powders in Calender Gaps in an Intermeshing Counter-Rotating Twin-Screw Extruder
Our experimental studies on unplasticized PVC (uPVC) melting process by ultrasound in-line monitoring method suggest that calendering effect between two screws dominates the melting process in an intermeshing counter-rotating twin-screw extruder. In this paper, a dispersed melting model in calender gaps is proposed to predict the melting length of PVC powders in terms of the number of calender gaps. Effects of screw geometries (channel depth, calender gap clearance) and processing conditions (screw speed, leakage flow) on melting length are discussed for both filled Newtonian and non- Newtonian fluid models. The calculated results are compared with experimental observations by “screw pulling out” method and ultrasound in-line monitoring method.
Effect of Particle Size on Mechanical Properties of Core Shell Polymers Prepared by Microemulsion Polymerization
The influence of particle size on the mechanical properties of core-shell polymers of polystyrene/poly(butyl acrylate) and poly(butyl acrylate)/polystyrene made by a two-stage microemulsion polymerization process is reported here. In the first stage the polymerization was carried out in microemulsions containing no salt or an inorganic or organic salt to modify particle size. Smaller particles were obtained in the first stage when salts were used. The mechanical properties depend on core-shell particle size, composition and location of the parent polymers.
Automatic Defect Detection on Structured Plastic Surfaces
Image processing has proved highly successful for automatic, objective quality monitoring in industry. Nowadays web inspection has become a very important application in the process of film extrusion. These systems make a complete quality inspection possible, even at high extrusion speeds commonly used in film extrusion. Nevertheless, the inspection of structured surfaces in real time seems almost impossible so far. But the combination of deterministic texture description and pattern matching makes the recognition and description of defects possible. Thereby these algorithms can enhance existing systems and allow a complete inspection of the products with structured surfaces.
Automatic Preform Shape Optimization for the Stretch Blow Molding Process
In this work, we develop a new numerical optimization strategy that targets a container thickness distribution by manipulating the preform geometry (thickness and shape) subject to process constraints (injection molding and stretch-blow molding). The proposed optimization strategy is combined with a sequential quadratic programming (SQP) method of the design optimization tools (DOTVanderplaats Reseacrh & Development Inc) to update the preform design variables while iterating over the stretch blow molding (SBM) process. The algorithm has been tested successfully on industrial parts.
Novel Spinal Brace Design and Manufacture
The present paper discusses investigations into the suitability of manufacturing, testing and using an alternative highly flexible structure incorporating innovative joints (actuators) linked together to form a sheet that can be conformed around complex three dimensional shapes which can be easily and instantaneously “switched” from a flexible state to a highly stable/rigid one and a process which can be reversed.In this paper consideration will be given to preparation, characterisation and properties of the manufactured brace and its modules. A range of techniques used to characterise these materials will be discussed, including image analysis, finite element analysis, thermo gravimetric analysis, compressive strength, impact and recovery measurements.
Mechanical, Thermal and Biodegradability Properties of Water Cross-Linked Wood Flour Reinforced Poly (Butylene Succinate) Composites
Wood flour (WF) reinforced poly (butylenes succinate) (PBS) composites have been prepared utilizing unique water-crosslinking technique to improve the physical properties of composites. Composites via water-crosslinking treatment exhibited improved mechanical properties due to the interfacial bonding between the wood fiber and the PBS matrix. Thermal analysis of water-crosslinked composites indicated that thermal degradation temperature of composite increased with the increasing water-crosslinking time. Biodegradation tests showed that adding wood flour increased the biodegradability of composite; however, the water-crosslinking reaction may reduce the biodegradability of wood composite.
Barrel Alignment- A Critical Factor in Reducing Extruder Wear
As processors increase the demand on the extruder for increased rate and product quality it is essential that the barrel, feed throat and drive are maintained properly for maximum service life. It is a common misconception that as long as the feedscrew and barrel are straight the machine will be in alignment. However, if the barrel is misaligned it can cause excessive wear and tear on the barrel and screw as well as the internal bearings and mechanisms within the gearbox which will reduce the service life. Excessive wear to the radial bearings can cause the screw to seize in the barrel. The scope of this paper is to investigate the factors that influence the extruder alignment and the proper procedure to measure and align an extruder.
Compatibilization of Blends of Polypropylene and Styrenebutadiene-Styrene Block Copolymer with DEM
Mechanical properties of Polypropylene /Styrene- Butadiene-Styrene Block copolymer blends, functionalized and non-functionalized were evaluated. Functionalization was carried out employing Benzoile Peroxide as initiator and Diethyl maleate (DEM) as functional monomer. An optimum Peroxide/DEM ratio was obtained in order to promote functionalization. Concerning mechanical properties of blends, the addition of SBS to the PP matrix increased elongation at break and reduced Young´s Modulus, while a rise on this property was achieved when the SBS was functionalized.
Water Vapor Diffusion through Glass-Fiber-Reinforced Nanocomposites: A Quantitative Approach
Moisture permeation experiments were conducted through vinyl ester films containing nano and microfillers, such as montmorillonite, carbon nanofibers, Kevlar™ pulp and glass fibers with a view to decrease the diffusion coefficient of water through fiber-reinforced plastics (FRPs). Variables examined included temperature, moisture concentration gradient, and filler content. A finite difference scheme was also used to compute the steady-state concentration profiles by solving Laplace’s equation over a region containing a regular twodimensional array of identical, impenetrable, rectangular blocks. There was good agreement between measured and calculated diffusivities; these results are also compared with results of other models existing in the literature.
Effect of a Mesoporous Silica and Silane Coupling Agents on the Reinforcing of Styrene Butadiene Rubber
Templated mesoporous silica (TMS) used as filler for SBR showed better mechanical properties for non vulcanized samples due to the polymer chains penetration within the mesopores. The reinforcement increases when TMS is used together with silane coupling agents (SiCA). The reinforcing and vulcanization kinetics on the SBR are studied with two silicas: conventional VN3 and TMS and two SiCA. The reinforcing is measured by the vulcanization degree and the mechanical properties. The swelling degree, elastic modulus and glass transition temperature (Tg) are higher for samples containing TMS. On the other hand the use of SiCA results in further increase of the swelling degree and therefore higher Tg with both sílicas. The vulcanization kinetics of the SBR is evaluated by rheometry and differential scanning calorimetry. The vulcanization rate is higher for the rubber filled with TMS indicating its autocatalytic effect. The use of SiCA decreases the cure rate and the maximum torque values.
Ultra High Molecular Weight Polyethylene Blown Film Process
Ultra high molecular weight polyethylene is one of the toughest plastics in the world. On the other hand, it is the hardest one to form into thin film, because of its extremely high melt viscosity. New blown film process enabled that granular UHMWPE powder is continuously shaped into biaxially oriented film at economical speed without any plasticizer. This process consists of a single screw extruder with full flight screw, a special rotating crosshead circular die with a coaxial screw and a tall neck type tubular film stretching unit. The UHMWPE blown film obtained by new process shows remarkably high tensile strength and abrasion resistance compared with a conventional PE films. We are expecting this film would be applied in various high performance applications i.e. lining film, covering of hydraulic hose, high strength flat yarn with stretching.
Description of the Foaming Process during the Extrusion of Foams Based on Renewable Resources
Some polymers based on renewable resources like starch containing materials can be plasticated by extrusion processing. Foams based on theses materials have an increasing importance in packaging applications, but also insulation materials have been developed. Starch contains water, which can work as a physical blowing agent for processing of these foams. The foaming process depends on process parameters like the pressure gradient in the die as well as on material properties like rheology. The main target is the production of foams with low density, high expansion ratio and a homogenous cell structure.The foaming process starts in the flow channel of the die. The cell nucleation process can be investigated by a die design with transparent inserts in the flow channel. The influence of process parameters on cell nucleation was determined. It could be shown that a higher pressure gradient in the die leads to a higher expansion ratio and thus to a later cell nucleation.Furthermore, the rheological properties also have an impact on the foaming behavior of molten starch. Shear viscosity is influenced by melt temperature, water content and mechanical energy input during the extrusion process. In this work, the dependency of the flow properties on process parameters was investigated in order to quantify the differences in pressure build-up caused by changes in screw speed and the resulting consequences on viscosity.
ABS Pipes for Chemical Transport
Polymer pipes for transport of corrosive substances have been widely adopted by the chemical industry, but problems of attack and failure have continued to occur. The present case involved ABS pipe used for carrying concentrated hydrochloric acid, where failure of a blanking plate caused a major loss of acid (2500 litres). One investigator observed that the polymer had become discoloured, and attributed the loss to poor selection of material. However, the failed parts had been lost in the incident and were not available for inspection. Intact blanking plates were available, however, and they showed absorption of impurities, producing softening of the ABS, but no brittle cracking. The problem of assessing resistance of polymers to industrial chemicals remains a problem if long-term exposure tests are not available to designers.
Ozone Cracking of Seals in Microchip Production
Lithography machines for making semiconductor chips use pneumatic circuits for the air bearings which support the tables on which the chips are etched by laser beams. The tables must be absolutely flat and perfectly still to achieve accurate circuits, a function achieved by the air bearings. An air bearing consists of a pressurised chamber enclosed by a nitrile rubber diaphragm. There have been problems however, with ozone cracking of the diaphragm seals, causing extensive machine downtime and loss of chip production. Examination of failed seals showed that very low levels of ozone (ppb) were sufficient to initiate cracks at sharp corners in the seal, the cracks growing until the seal failed. ESEM analysis of the fracture surface showed enhanced oxygen levels from traces of carbonyl compounds on the surface left by ozone attack. The problem has been eliminated by filtering the air flow both before and after the compressors.
Subsurface Anchoring of Fluorescent Probes in Poly(Ethylene-Co-Acrylic Acid) Film
Poly(ethylene-co-acrylic acid) (PEAA) films contain reactive carboxylic acid groups that can undergo chemical coupling after activation. However, the chemistry will occur not only on the surface but also in the subsurface of the film. The aim of this work was to study the surface grafting behavior and penetration reaction of a relatively small fluorescently labeled probe molecule, dansyl cadaverine, in PEAA films. A two-step reaction was conducted. First, PEAA film was activated with PCl5 at room temperature, which could occur throughout the film depending on reaction time. Second, the acid chloride was reacted with dansyl cadaverine to form a modified film. ATR-FTIR spectroscopy and fluorometry were employed to analyze the penetration behavior. Using dichloromethane as a solvent, it was found that the dansyl cadaveine penetrated throughout the analysis region (~400 nm) of the ATR-FTIR evanescent wave in few minutes and the conversion was approximately 90%. As the penetration depth increased with time, so did the amount and fluorescence intensity of grafted dansyl-cadaverine. However, insignificant changes of surface wettability for dansyl-cadaverine-modified film were observed by contact angle measurements.
Prediction of Core Deflection in Ceramic Injection Molding
A full three-dimensional finite element simulation of ceramic injection molding is performed using the PELDOM software. Predicted melt-front advancement, and pressure variation and core deflection for an airfoil-shaped mold are compared with the corresponding experimental data. The power-law-WLF model is used for strain-rate and temperature dependence of the viscosity for a ceramic/polymer mixture. A modified Herschel-Bulkley model is used to include the effect of yield stress in the viscosity model. Pressure from the mold filling simulation is used to predict the deflection of core pins in the mold. Numerical predictions are found to be in good agreement with experimental data.
Thermal Behavior during Thermoplastic Composites Resistance Welding
Two- and three-dimensional heat transfer finite element models of the resistance-welding process for joining thermoplastic composite laminates were developed. The models simulated a resistance welded single lap-shear joint using 16-layer unidirectional APC- 2/AS4 laminates. The heating element consisted of a stainless steel metal mesh sandwiched between neat PEEK films. The heat was generated at the bond surface by applying current to the heating element, using a controllable DC power supply. The 2-D model was used to investigate the effect of the length of the exposed areas of the heating element to air (clamping distance) on the local overheating at the edges and the effect of various input power levels on the thermal behavior of the welds. It was found that controlling the clamping distance could improve the thermal uniformity of the weld. The 3-D model showed that heat conduction along the length of the laminates had a great influence on the thermal uniformity of the weld interface.
Novel Coupling Agents for PVC/Wood-Flour Composites
Effective interfacial adhesion between wood fibers and plastics is crucial for both the processing and ultimate performance of wood plastic composites. Coupling agents are added to wood plastic composites to promote adhesion between the hydrophilic wood surface and hydrophobic polymer matrix, but to date no coupling agent has been reported for PVC/wood composites that significantly improved their performance and was also cost effective. This paper presents the results of a study using chitin and chitosan, two natural polymers, as novel coupling agents for PVC/wood-flour composites. Addition of chitin and chitosan coupling agents to PVC/wood flour composites increased their flexural strength by approximately 20%, their flexural modulus by approximately 16%, and their storage modulus by approximately 33-74% compared to the PVC/wood flour composite without the coupling agent. Significant improvement in the composite performance was attained with 0.5 wt% chitosan and while 6.67 wt% chitin used.
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