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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Evolution of Properties of a Thermosetting Epoxy/Aromatic Amine System with Increasing Cure (Conversion): Physical Aging
Isothermal physical aging below Tg of a high-Tg thermosetting difunctional epoxy/tetrafunctional aromatic amine system has been investigated at different aging temperatures (Ta) and chemical conversions (monitored by the glass transition temperature, Tg) using the TBA freely oscillating torsion pendulum technique. In the absence of chemical reaction during an isothermal aging process, the rate of isothermal physical aging passes through a minimum with increasing conversion. The minimum is related to the minimum in mechanical loss between the secondary relaxation in the glassy state (T? ) and the glass transition relaxation (Tg) [the temperatures of both of which increase with increasing conversion]. If isothermal aging rates for all conversions (beyond gelation) would have been measured directly from temperatures below T? to above Tg, it is concluded that two maxima in isothermal aging rate would have been observed corresponding to the two relaxation processes. There exists a superposition in isothermal aging rate vs. Tg-Ta [by shifting horizontally (and vertically)], which implies that the aging rate is independent of the details of the changing chemical structure due to cure. Controlling mechanisms during physical aging are segmental mobility associated with the Tg region and more localized motion associated with the glassy-state relaxation, T?.
Characterization of Diene Monomers as Self-Heagling Agent for Polymer Composite and its Microcapsules
Two different diene monomers [dicyclopentadiene (DCPD) and 5-ethylidene-2-norbornene (ENB)] as self-healing agent for polymeric composites were microencapsuled by in-situ polymerization of urea and formaldehyde. Storage modulus (G’) and tan ? vs. cure time data were obtained by dynamic mechanical analysis (DMA) to investigate cure behavior of unreacted self-healing agent mixture with catalyst. Glass transition temperature (Tg) and exothermic reaction of samples cured for 5 min and 120 min in the presence of different amounts of catalyst were analyzed by differential scanning calorimetry (DSC). In a comparison with DCPD, ENB may be advantageous as self-healing agent since it proceeds much faster in reaction at much lower amount of catalyst with no melting point and produces resin with higher Tg when cured under same conditions. Microcapsules containing the healing agent were successfully formed for both diene monomers, and characterized by thermogravimetric analysis (TGA). Optical microscope (OM) and particle size analyzer (PSA) were employed to observe morphology and size distribution of microcapsules, respectively. The microcapsules were similar in thermal property as well as particle shape and size.
Viscoelastic Properties of Crosslinked LLDPE Films
Creep and stress-relaxation of linear lowdensity polyethylene (LLDPE) crosslinked with ?- irradiation was studied as a function of irradiation dose. It was shown that both storage modulus and ?- relaxation are influenced by irradiation. An influence of relatively low gel content on stress relaxation was detected. However, the creep results showed an increase of the creep strain when the polymer is irradiated with a dose below 4 Megarad (MR) in comparison with a nonirradiated film. This increase corresponded to the disorientation in the amorphous phase, which takes place as a result of the film heating during irradiation. This disorientation was demonstrated by differential scanning calorimetry (DSC) and X-ray analysis.
Nanocomposite Formation Mediated by Specialty Controlled Architecture Materials
Controlled architecture materials (CAMs) (ie. Block copolymers) are being explored as specialty additives for the formation of polymer nanocomposites under meltprocessing conditions. These block copolymer-based additives provide interesting exfoliation solutions for clays of differing hydrophobicity in a variety of polyolefin and styrenic resins. This presentation will outline details of the nanocomposite formation process, nanocomposite characterization and highlight composite physical property enhancements.
Ultrasonic Technique and Probes for Monitoring Surface Imperfection of Microfluidic Plastic Devices during Injection Molding
Miniature ultrasonic probes were embedded into the mold of an injection molding machine for microfluidic devices. Surface imperfection of the molded parts was monitored using the ultrasonic velocity of the part obtained during molding. It was verified that the lack of sufficient holding pressure caused detachment of the molded part from the mold surface before the part sufficiently solidified, resulting in the increase of the roughness on the part surface. The presented ultrasonic technique and probes enable on-line quality control of the molded part by optimizing the holding pressure and the improvement of process efficiency by reducing the cycle time.
Study on Aerodynamics of Cooling in Film Blowing
A numerical analysis using a renormalization group (RNG) k-? model and Fluent software was performed on the air ring cooling system of the film blowing process. The calculations were in a good agreement with the experimental results to predict maximum air velocities along the bubble surface at different axial distance from the die. Outside of the air-ring, the simulation results indicated that the heat transfer coefficient function of the form, h = aVmax b, is adequate mostly at low Blow-Up-Ratio (BUR). Different bubble shapes, for the same BUR, produced significant differences in the air flow pattern as well as heat transfer coefficient. In this work we want to study the correlation between thermal inertia and aerodynamics of cooling air under different bubble geometry.
Nanoclay Exfoliation in Thermoset Polyimide
The mechanism of nanoclay exfoliation in a thermoset polyimide nanocomposite system is being investigated. It has been found that full exfoliation is not achieved simply by processing the clay in the polyimide resin. Therefore, the clay is first intercalated with a lower molecular weight resin, then dispersed into a higher molecular weight resin, and the entire system is cured to obtain the final composite material with exfoliated nanoclay particles. The lower molecular weight resin residing inside the clay galleries exerts large elastic forces on clay layers upon crosslinking due to higher crosslink density. Smaller viscous stresses are exerted against clay layer separation by the surrounding polymer matrix due to lower crosslink density. The exfoliated clay structures are characterized by wide angle X-ray diffraction and transmission electron microscopy.
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.
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