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.
This work examined the effect of tire-tread reclaimed rubber content on physical and mechanical properties of natural rubber, vulcanized by microwave (MW) irradiation and thermal cure (CT) systems. The results suggested that the properties of the vulcanizates from CT method was higher than those from MW method except for the swelling level in toluene. The differences in the results between these two curing systems could be explained in terms of the density and the type of crosslinks present in the NR compounds. The microwave cure was more effective as the reclaimed content was increased.
Silica contents in fly ash particles of 30 and 60phr were introduced as reinforcing filler in NR compound with varying Si69 coupling agent contents. It was found that the scorch and cure times of the NR/FA vulcanizates slightly increased with a decrease in crosslink density when increasing Si69 contents. The decrease in crosslink density was compensated by chemical bonding between the rubber and the fly ash particles as a result of Si69. Concentrations of 2.0 and 4.0 wt% Si69 coupling agent were recommended for the improvement of the tensile modulus and tear strength of the NR/FA composites. The tensile strength did not change with Si69 content.
This paper studied the effect of molecular architecture of PE on structural changes of PVC in PVC/PE blends. The thermal property results indicated that PE in the blend between PVC and PE affected the degradation mechanism of PVC. This was explained in terms of a macro-radical cross-recombination reaction between PVC and PE molecules which was confirmed by considering the chemical shift in Carbon-13 Nuclear Magnetic Resonance. The changes in decomposition and glass-transition temperature of PVC in PVC/PE blends were also affected by types and melt flow indexes of the polyethylene.
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?.
The surface mechanical properties of ethylene vinyl acetate (EVA) with various vinyl acetate (VA) contents have been investigated. These nano mechanical properties, obtained from the nanoindentation technique, were compared with bulk results from the conventional tensile test. Agreement in Young's modulus as a function of VA content is found between two data. The discrepancy in modulus value between surface and bulk was also found in EVA with higher VA content. We speculate that this is due to macroscopic structure effect on bulk modulus as well as intrinsic viscoelastic deformation behavior of EVA.
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.
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.
Plastics injection molding has been limited by the lack of observability and controllability, such that it has not been possible to know or control flow rates and pressures at multiple locations in a mold. Using cavity pressure transducers and faster than real time process simulation, the described system provides estimates of the flow rates, part weight, melt temperature, and apparent viscosity before the mold opens and the parts are ejected. Validation results for part weight are provided for a two-cavity family mold with a valve-gated hot runner system.
A new concept design for a self-energizing, wireless sensor is presented. The sensor extracts energy from the polymer melt and transmits discrete acoustic signals whose timing indicates a pressure change and whose frequency indicates the melt temperature. A receiving system outside the mold receives the transmitted signals and reconstructs the melt pressures and temperatures. It then utilizes mapping and simulation techniques to estimate the pressure, temperature, and flow rates in the entire mold in real time.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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Brown, H. L. and Jones, D. H. 2016, May.
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ANTEC 2016 - Indianapolis, Indiana, USA May 23-25, 2016. [On-line].
Society of Plastics Engineers
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