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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Numerical Simulation of Injection Molding of Semicrystalline Thermoplasti
Injection molding process of semicrystalline plastics was simulated with a stress-induced crystallization model. Pseudo-concentration method was used to track the melt front advancement. The stress relaxation was incorporated into the model using the WFL model. Simulations were carried out under different processing condition to investigate the effect of processing parameters on the crystallinity of the final part. The simulation results reproduced most of the features reported in the literature.
Process Fingerprints for Compounding of Polymer Blends – An Industrial Prospective
A process fingerprint measurable by on-line monitoring of common process variables could aid immensely the ability of a process engineer to control the process output. The torque curve of a Brabender batch internal mixer offered many fingerprints related to the fundamental behavior the raw ingredients experienced during the mixing process. Suggestions were made how to derive fingerprints from the fundamental functions of twin screw extrusion processes.
Model Based Prediction of Permeability in Preform Materials
Knowledge of the permeability tensor in liquid composite molding is important for process modeling and optimization. However, experimental determination of the permeability is difficult and time consuming. In this work, a lattice Boltzmann simulation which has been modified for flow in porous media is used to predict permeability as a function of yarn location, orientation, and fiber fraction. Calculated permeabilities are compared with experimental measurements for a variety of systems. Good agreement is achieved as long as the mesh size is greater than the size of the smallest throats in the porous medium.
Rheological Behavior of Modified Polypropylene (PP) with Nitrile Rubber (NBR)
The rheological behavior of polypropylene (PP) modified with nitrile rubber (NBR), within the composition range of 10-30 wt% NBR content, was studied based on the blend ratio, dynamic vulcanization and additives blending effects. Results indicate all systems show a pseudoplastic behavior with an increasing melt viscosity on NBR content. Dynamically vulcanized blends present similar melt viscosity and lower die swell values than corresponding unvulcanized blends. The rheological behavior was correlated with blend morphology.
Interaction between PVA and Starch System Plasticized with Different Moisture Content
We investigated the interaction between PVA and starch blended series plasticized with different moisture content. Brabender plasticoder was applied to research the effect of gelatinization of water plasticized starch on the processability of this series. The moisture content of this series was furthermore found increasing with the increase of relative humility in different ambient condition.
Morphology Distribution of Injection Molded Polypropylene
The morphology distribution of injection-molded polypropylene (PP) was quantitatively studied using synchrotron radiation. Samples were taken from a PP plate at different positions from the gate. X-ray measurements were performed with the beam normal to the flow direction. The evaluation of x-ray data allows determination of distributions of the crystallinity, the imperfection factor, the á-phase orientation, and the â-phase concentration. Different distributions are observed at different distances from the gate.
Rheological Probing of Structure in Polypropylene / Clay Nanocomposites
Polypropylene/clay nanocomposites have been prepared with a variety of hybrid structures by melt mixing a fixed amount of organically modified clay, different levels of a maleated polypropylene and polypropylene. The structure has been investigated with X-Ray diffraction and transmission electron microscopy. An optimum level of maleated polypropylene is found to yield the greatest degree of exfoliation in polypropylene. The relative viscosity curves reveal a systematic trend with the extent of exfoliation and show promise for quantifying the hybrid structure of the nanocomposites.
Documenting Flow Segregation in Geometrically Balanced Runners
The flow distribution through a geometrically balanced runner is not evenly balanced due to the melt temperature segregation that occurs at each branch point in the runner. A test mold is built and molding trials are conducted to document the flow segregation in a four cavity mold containing a geometrically balanced runner. The extent of the flow segregation is seen to be a function of the resin type, the flow rate, and the extent of the filling.
The Effect of Blending on the Viscosity Reduction of Recycled Milk Bottle Grade HDPE
Post-consumer plastic waste in Australia contains over 50,000 tonnes p.a. of HDPE blow moulded bottles, with half still ending up in landfill. Recycled milk-bottle grade HDPE is known to be too high in molecular weight for processing by injection molding. In this study, the target was to make injection-molded compositions with a content of the recycled material of 75% or higher by blending with commodity plastics. The results of rheological, thermal and mechanical studies of the blends are presented.
Rheology and Processing of TPV's
The rheological behavior of TPV in shear and extensional is studied to help understanding the flow behavior in various processing operations. The TPV's, which are dynamically vulcanized PP/EPDM blends show in shear flow a typical rheological behavior with an apparent yield stress at low shear rates and a shear-thinning viscosity at high(er) shear rates. In extension the TPV melts appeared not to show strain-hardening. This study discusses the observed behavior in terms of composition.
Impact Modification of Poly(Ethylene Terephthalate)
Many polar thermoplastics, such as poly(ethylene terephthalate), tend to be notch sensitive and can exhibit a sharp ductile-to-brittle transition. Many studies focusing on the improvement of toughness using elastomeric particles have demonstrated that the increase in toughness is related to the ability of the rubber particles to cavitate and to morphological parameters. In this work, the mechanical properties of a poly(ethylene terephthalate) matrix containing several impact modifiers are investigated.
Processing-Structure-Properties Relationships in Multilayer Films
LDPE/PET multilayer films with and without a reactive tie layer were prepared by extrusion blowing process. PET layer showed a negligible orientation and an almost zero crystallinity. For PE layer, the crystalline a-axis was oriented along machine direction and the b-axis mainly tended to the transverse-normal plane, no orientation for amorphous phases was found. A morphological model for the different processing conditions was proposed. The shrinkage and tear strength correlated well with the orientation structure of the LDPE layer in the films.
Blends of ABS and i-PP
Blends of Acrylonitrile-Butadiene-Styrene, ABS, and isotactic Polypropylene, i-PP, have been made using a block copolymer of Styrene-Butadiene-Styrene, SBS, as compatibilizing agent. The constituents were melt mixed, one step, in a Haake chamber. The compatibility of the blends was analyzed using different techniques such as differential scanning calorimetry, DSC, and scanning electron microscopy, SEM. The mechanical properties of the blends were also evaluated. The results have been shown an improvement in mechanical properties when SBS is used in the blends.
Estimation of Elongational Viscosity of Polymers for Accurate Prediction of Juncture Losses in Injection Molding
A new elongational viscosity model along with the Carreau model for shear viscosity is used for a finite element simulation of the flow in a capillary rheometer. The entrance pressure loss predicted by the finite element flow simulation is matched with the corresponding experimental data to predict the parameters in the new elongational viscosity model.
Measurement of Strain Rate-Dependent Material Properties for Polymers
Present market forces dictates that the automotive industry must increase passengers safety. Currently, CAE-Methods such as crash-simulations are used, but due to the absence of material data of polymers at high strain rates, the results of these simulations are in general inaccurate. This study is concerned with material testing on airbag cover materials with a high speed tensile testing machine to provide material data and information on material behaviour at different strain rates and temperatures.
Analysis of Feed Characteristics on the Performance of Groove-Feed Extruders
The effect of varying the feedstock shape on the output performance of groove-feed extruders was examined. Pellets of five different aspect ratios were run, as were five different levels of bottle regrind blended with virgin pellet. The different feedstock materials were compared on two different screw designs with differing feed zone geometries. The results showed that different aspect ratios or bulk densities had no effect on the locking action of solids within the grooves, but can have a dramatic influence on the filling and packing unless a screw of appropriate design is used.
Large Part Injection Molding Product Optimization
High-density polyethylene (HDPE) is widely used in large-part injection molding applications, such as five-gallon pails, agricultural bins, and refuse carts. Certain physical properties are critical in helping to ensure a long useful life for parts in these demanding applications. This paper presents a predictive model that was developed from molded part testing and HDPE resin physical properties. By implementing this information effectively, the resin producer and the injection molder can work together to improve molded part performance.
Blow Molding Virgin and Regrind Polymers with Titanates and Zirconates - 2001
In addition to filler/pigment to polymer coupling, two parts of neoalkoxy titanates and zirconates per thousand parts of polymer provide for in situ metallocene-like Repolymerization" catalysis of the filled or unfilled polymer during the plastication phase resulting in: faster blow molding production cycles at lower temperatures; maintenance or increase in mechanical properties; the in situ regeneration of regrind polymer properties; the lowering of polymer recrystallization time; and the copolymerization of dissimilar polymers."
Three-Dimensional Simulation of Injection-Compression Molding of a Compact Disc
A finite volume algorithm for simulating polymer injection-compression molding is presented. The developed numerical model deals with non-isothermal flow of compressible, non-Newtonian fluids in complex 3D geometry. Tait equation with modification of considering cooling effect is incorporated to describe the non-equilibrium polymeric pvT behavior during compression phase. The developed methodology is applied to study the cooling, pvT behavior as well as the thermal shrinkage of the injection-compression molded compact disc.
The Effect of Contraction Angle on the Entrance Pressure Loss
The excess pressure losses due to end effects in the capillary flow of a metallocene linear low-density polyethylene (m-LLDPE) were studied both experimentally and theoretically. They were first determined experimentally as a function of the contraction angle (8° to 150°). It was found that the excess pressure loss function increases with increasing contraction angle from 8° to about 30° and consequently decreases up to contraction angles of 150°. Numerical simulation using a multimode K-BKZ viscoelastic equation and a purely viscous equation (Carreau model) have shown that the excess pressure loss function decreases monotonically with increasing contraction angle, an observation that contradicts the experimental results. The origin of this disagreement is also discussed.
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