SPE Library
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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Conference Proceedings
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.
A Novel Three-Dimensional Analysis of Polymer Injection Molding
The advantages of three-dimensional (3D) mold-filling analysis over the 2.5D model are twofold: improving the prediction accuracy and avoiding the mid-plane construction. Moreover, 3D analysis is essential in the simulations of GAIM or IC packaging. This paper presents a highly efficient 3D approach to simulate the non-isothermal non-Newtonian melt flow in injection molding. The proposed approach shows good agreement in comparison with 2.5D model for molding of thin parts. Some industrial examples with complex geometries are analyzed to illustrate the capabilities of the presented approach.
Morphology of PCL/EVA/PET Ternary System
The morphology of ternary blends of polycaprolactone (PCL) / ethylene-co-vinyl acetate) (EVA) / poly(ethylene terephtalate) (PET) was investigated using optical microscopy. The sample appears as an aggregate mass. After controlled heating (30 to 280°C) it was noticed that the system forms an immiscilble blend where each component had its own melting temperarture. It was observed that the PCL was the major component and EVA was the minor one. The EVA domain did not present birefrigence. The PET domain was hidden by PCL and EVA.
Cure of an Epoxy Thermoset System Modified with Engineering Thermoplastics
During the cure of a thermoset-thermoplastic blend two-phase morphologies may be formed. The phase separation process may be controlled by manipulation of the rate of polymerization of the thermoset system. In this work, the effect of the addition of different thermoplastics on the rheokinetics of an epoxy thermoset system is presented. The reactive system used was diglycidyl ether of bisphenol-A cured with 4-4' diaminodiphenyl sulfone. The kinetics was followed by differential scanning calorimetry and the change in the rheological properties during the curing by dynamic rheometry.
Energy Dissipation from a Perfectly Elastic Material
Energy dissipation is possible even from a perfectly elastic material, preferably an elastomer, when it is subjected to a shock" stretch or a "shock" contraction. This dissipation is not the usual viscoelastic or plastic losses associated with internal friction in solids. The energy values associated in this "shock" process are independent of the path of the stress-strain curve and depend only on the initial and final states for the elastic material. The sudden "shock" stretch of the elastic material is equivalent to thermodynamic free compression of a gas. Heat dissipation from an elastic rubber belt is examined."
A New Non-Reactive Polymer Processing Additive (PPA) for Use with HALS and Other Chemically Interacting Additives
Polymer processing additives are used to reduce melt fracture, increase the processing window and eliminate die lip build-up and gels in polyolefins. There are additives that can interfere with the performance of the PPA by four main mechanisms - adsorption, abrasion, site competition and chemical reaction. Strong bases such as hindered amine light stabilizers (HALS) can cause the PPA to lose effectiveness due to both site competition and chemical reaction. Introduced is a next generation, non-reactive PPA that has improved performance compared to conventional materials.
Failure Analysis of Hinges: Case Studies, Part One
Plastic hinges are subjected to different types of stresses during service. Some case studies are presented in this paper to show the effect of service history, processing conditions, and part design on hinge failure. Microscopic analysis was used in these investigations to identify the fracture features. Additionally, Finite Element Analysis was used to estimate the stresses on the hinges during service. The first case shows mainly the effect of adverse service history on the hinge performance. The second case illustrates primarily the importance of appropriate processing conditions in preventing hinge failure. The third case describes essentially the combined contribution of end-use and part design on limiting the hinge lifetime.
Combining Boron Nitride with a Fluoroelastomer: An Enhanced Polymer Processing Additive
The effect of a new processing additive (boron nitride powder in combination with a fluoroelastomer) on the rheology and processability of molten polymers is studied. The equipment used include an Instron capillary rheometer equipped with a special annular die (Nokia Maillefer wire coating cross-head), a twin screw extruder equipped with a blow moulding unit, and a parallel-plate rheometer. Metallocene polyethylenes with and without boron nitride (BN) and fluoroelastomer are tested in extrusion and conventional high density polyethylenes with and without BN with fluoroelastomer are tested in Blow moulding operations. First, it is demonstrated that BN is a superior processing aid compared to conventional fluoropolymer ones. Secondly, it is found that the combination of BN powders with a small amount of a fluoropolymer improves even further the processability of molten polymers (melt fracture performance).
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