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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

THE EFFECTS OF ROTOR INCORPORATED MOLD FOR THE ELIMINATION OF THE WELDING LINE IN INJECTION MOLDING
Y.P. Tsai , J.C. Wang , T.Y. Huang , R.Q Hsu, May 2010

A built-in rotor inside the mold was designed. The rotorƒ??s surface was constructed with the purpose of disturbing the skin layer and core layer of the molten material and hopefully destroy the fountain flow structure of plastic flow. Several specimens were made by changing the rotorƒ??s surface profiles. Angular velocity four polymers were chosen as the parameters. Numerical software was used to simulation the filling process.Experimental results showed that the equipment did twist the weld line and in some cases even made the weld line disappear the effects were more apparent in ABS and ASA. Numerical analysis showed the similar results as the experiments.

MORPHOLOGY DEVELOPMENT BY CHAOTIC ADVECTION IN PA-EVOH BLENDS WITH POLYMER COMPONENT INTERACTIONS
X. Jin , D. A. Zumbrunnen, May 2010

To take advantage of the superior oxygen gas barrier property of ethylene-vinyl alcohol random copolymer (EVOH) and the balanced mechanical properties of polyamide (PA) blend morphologies with high interfacial areas at constant compositions were produced with a laboratory chaotic advection blender. This new processing technology intrinsically develops blends having very high interfacial area so it has special applicability to barrier films. Even with influences from component interactions multi-layer films with submicron layer thicknesses were formed. The layers became finer for more extensive chaotic advection as has been documented earlier in immiscible nonreacting polymer blends. Influences of structure on impact toughnesses are specifically reported.

FAILURE CHARACTERIZATION OF VIBRATION WELDED POLYPROPYLENE JOINTS
Valeria Pettarin , Laura A. Fasce , Patricia M. Frontini, May 2010

The failure behavior of vibration welded polypropylene T-peel joints was investigated. The quality of welded joints was assessed using several mechanical tests including: smooth tensile notched tensile DENT and DART. The depreciation of properties was evaluated as the ratio between the properties of the pristine material and the joint. The morphological features of deformed and fractured materials were examined using polarized light optical microscopy and scanning electron microscopy.From our investigations it emerges that the vibration welding process resulted in low weld efficiencies for all mechanical testing techniques. SEM inspection of the fracture surfaces also revealed the presence of unwelded points and scarce material inter-diffusion consistent with the low weld efficiencies achieved. The investigations also revealed the drawing capability of the pristine material was negatively affected by the thermal history involved during the welding process. Contrary to pristine material behavior welded samples developed a small outer plastic zone before fracture.

MODELING OF FLOW AND HEAT TRANSFER WITHIN HOT RUNNER SYSTEMS USING THE RADIAL FUNCTION METHOD (RFM).
Martin N. Bureau, , Tan-Minh Ton-That, Kenneth Cole, May 2010

The radial functions method (RFM) was used to model the flow and heat transfer within hot runner systems. The technique is a meshless method that deals well with highly non-linear problems. The technique was implemented to simulate the coupled flow and heat transfer effects, as well as the interaction with the metal surroundings of hot runner systems. Practical problems were simulated, and the results clearly show various effects that control the flow in injection molding runner systems, such as the thermal imbalance generated by the runner bifurcations, that may lead to flow imbalances during the filling process.

MODE I AND II INTERLAMINAR FRACTURE TOUGHNESS OF NANOCLAY-REINFORCED EPOXY/GF COMPOSITES
Martin N. Bureau , Tan-Minh Ton-That , Kenneth Cole, May 2010

Of prime importance in fiber reinforced composites is the interfacial strength between glass fiber reinforcement and matrix. A potential benefit of nanoclays (NC) is to improve the matrix-reinforcement stress transfer due to their positive interactions with glass. Double cantilever beam (DCB) and end-notch flexural (ENF) tests were performed to evaluate the interfacial fracture toughness (Gc) in mode I and II, respectively, of GF composites with a NC/epoxy matrix. Results show no benefit of NC on mode I toughness while a significant 20%+ improvement on mode II was obtained. Given the non-optimal chemistry of the epoxy/GF laminate used, this result is encouraging.

EFFECTS OF HANNEBACHITE ADDITIVE ON THE MECHANICAL BEHAVIOR OF PHENOLIC-NATURAL FIBER COMPOSITES
Stephen Hofer , Gediminas Markevicius , Vivak M. Malhotra , Charles Miller , Francois Botha, May 2010

The issue of global warming demands more effective management of our forested lands thus requiring the reduction in the consumption of natural wood products. Therefore for the last few years we have been attempting to develop structural composite materials from natural fibers derived from annual crops and phenolic polymer. Recently we systematically incorporated plate-like hannebachite (calcium sulfite) crystallites as an additive into the composites derived from phenolic and miscanthus. The concentration of hannebachite crystallites in the compressive molded composites varied between 30 to 80 wt%. The SEM measurements indicated that the hannebachite crystallites maintained their plate-like structure in the composites and the flexural strength of the materials inversely scaled with the concentration of the inorganic phase i.e. it ranged from 60 MPa to 3 MPa. The addition of jute mesh fibers in our composites further significantly improved the ductile behavior of the fabricated materials. The thermal and thermomechanical behaviors of the composites were ascertained by DSC and DMA measurements.

EFFECTS OF HANNEBACHITE ADDITIVE ON THE MECHANICAL BEHAVIOR OF PHENOLIC-NATURAL FIBER COMPOSITES
Stephen Hofer , Gediminas Markevicius , Vivak M. Malhotra , Charles Miller , Francois Botha, May 2010

The issue of global warming demands more effective management of our forested lands, thus, requiring the reduction in the consumption of natural wood products. Therefore, for the last few years, we have been attempting to develop structural composite materials from natural fibers derived from annual crops and phenolic polymer. Recently, we systematically incorporated plate-like hannebachite (calcium sulfite) crystallites as an additive into the composites derived from phenolic and miscanthus. The concentration of hannebachite crystallites in the compressive molded composites varied between 30 to 80 wt%. The SEM measurements indicated that the hannebachite crystallites maintained their plate-like structure in the composites, and the flexural strength of the materials inversely scaled with the concentration of the inorganic phase, i.e., it ranged from 60 MPa to 3 MPa. The addition of jute mesh fibers in our composites further significantly improved the ductile behavior of the fabricated materials. The thermal and thermomechanical behaviors of the composites were ascertained by DSC and DMA measurements.

STRUCTURAL COMPOSITES FROM RECYCLED HDPE AND CALCIUM SULFITE CRYSTALLITES
Gediminas Markevicius , Joshua D. Stoll , Vivak M. Malhotra , Charles E. Miller , Francois B. Botha, May 2010

Typically wood-plastic composites are manufactured from HDPE and wood byproducts. However to mitigate the concerns associated with the environment and costs attempts were made to develop structural composite materials from calcium sulfite hydrate (hannebachite) natural fibers and recycled HDPE. The hannebachite crystallites are produced during the scrubbing of coal combustion flue gases and have no commercial value. The structural thermal and mechanical behaviors of the composites as well as of raw materials were determined by SEM DSC DMA and flexural measurements. Our results suggest that it may be feasible to develop wood substitute composites without the use of wood or its byproducts. Flexural strength as high as 30 MPa was obtained.

STRUCTURAL COMPOSITES FROM RECYCLED HDPE AND CALCIUM SULFITE CRYSTALLITES
Gediminas Markevicius , Joshua D. Stoll , Vivak M. Malhotra , Charles E. Miller , Francois B. Botha, May 2010

Typically wood-plastic composites are manufactured from HDPE and wood byproducts. However, to mitigate the concerns associated with the environment and costs, attempts were made to develop structural composite materials from calcium sulfite hydrate (hannebachite), natural fibers, and recycled HDPE. The hannebachite crystallites are produced during the scrubbing of coal combustion flue gases and have no commercial value. The structural, thermal, and mechanical behaviors of the composites, as well as of raw materials, were determined by SEM, DSC, DMA, and flexural measurements. Our results suggest that it may be feasible to develop wood substitute composites without the use of wood or its byproducts. Flexural strength as high as 30 MPa was obtained.

DYNAMIC PROPERTY OF THE FROZEN-LAYER AND ITS EFFECTS ON WARPAGE IN INJECTION MOLDED PARTS
Yuing Chang , Chung Shin Liu , Shih Tsun Huang , Chao-Tsai Huang , Meng-Chih Chen , Wen-Hsien Yang, May 2010

The formation of the frozen-layer which covers skin layer and orientation layer will affect the shrinkage at mold during cooling cycle and post-shrinkage of the part after ejecting out from the mold on both flow and transverse directions. However its physical mechanism and effects on the warpage are still not fully understood. In this study the dynamic properties of the frozen-layer are investigated numerically. Through the study of dynamic behavior of the frozen-layer formation at the whole molding process including shear rate variation relaxation time change and other properties its physical mechanism and its effects on shrinkage and warpage can be observed.

DYNAMIC PROPERTY OF THE FROZEN-LAYER AND ITS EFFECTS ON WARPAGE IN INJECTION MOLDED PARTS
Yuing Chang , Chung Shin Liu , Shih Tsun Huang , Chao-Tsai Huang , Meng-Chih Chen , Wen-Hsien Yang, May 2010

The formation of the frozen-layer, which covers skin layer and orientation layer, will affect the shrinkage at mold during cooling cycle and post-shrinkage of the part after ejecting out from the mold on both flow and transverse directions. However, its physical mechanism and effects on the warpage are still not fully understood. In this study, the dynamic properties of the frozen-layer are investigated numerically. Through the study of dynamic behavior of the frozen-layer formation at the whole molding process, including shear rate variation, relaxation time change, and other properties, its physical mechanism and its effects on shrinkage and warpage can be observed.

COMPARISON OF SORBITOL AND GLYCEROL AS PLASTICIZERS FOR THERMOPLASTIC STARCH IN TPS/PLA BLENDS
Hongbo Li , Michel A. Huneault, May 2010

This paper investigates the morphology and properties of TPS/PLA blends with TPS plasticized by sorbitol, glycerol and glycerol/sorbitol mixtures. The blends were prepared using a twin-screw extruder. The plasticizers were added to starch in the first stage of the extruder to allow complete starch gelatinization. The PLA was added at mid-extruder and thoroughly mixed with the TPS. The total plasticizer concentration was remained at 36% and the TPS content was at 27%. The viscosity, blend morphology, tensile mechanical properties as well as the thermal properties of the materials were measured. It was found that the choice of the plasticizer had an important effect on the blend properties. Finer blend morphologies, higher tensile strength and modulus were found for the sorbitol plasticized blends

UNIFORM MOLD CAVITY VENTING IS FAR MORE CRITICAL TO BALANCE FILL OF MULTI-CAVITY MOLDS THEN ANY OTHER SINGLE ITEM
Terry L. Schwenk, May 2010

Venting is a major cause of imbalance filling of multicavity injection molds. Typically venting isn’t looked at closely because the perception venting is fine as along as there is no evidence of burning on the part. DO NOT under estimate the effects of back pressure in the cavity due to poor venting. The volume of air in the cavity needs to be displaced by the molten plastic. Like a syringe barrel the plunger cannot be pushed forward if the end of the needle is too small or pinched off. The size of the needle orifice will determine how fast and how much pressure is required to push the plunger forward. If you have poor venting it will require more pressure and time to displace the air.

UNIFORM MOLD CAVITY VENTING IS FAR MORE CRITICAL TO BALANCE FILL OF MULTI-CAVITY MOLDS THEN ANY OTHER SINGLE ITEM
Terry L. Schwenk, May 2010

Venting is a major cause of imbalance filling of multicavity injection molds. Typically venting isn't looked at closely because the perception venting is fine as along as there is no evidence of burning on the part. DO NOT under estimate the effects of back pressure in the cavity due to poor venting. The volume of air in the cavity needs to be displaced by the molten plastic. Like a syringe barrel, the plunger cannot be pushed forward if the end of the needle is too small or pinched off. The size of the needle orifice will determine how fast and how much pressure is required to push the plunger forward. If you have poor venting, it will require more pressure and time to displace the air

PREDICTION OF SECONDARY FLOWS IN NON-CIRCULAR DUCTS USING THE RADIAL FUNCTIONS METHOD
S. Sánchez Valdes, M. Luisa López Quintanilla, C. González Cantu, J. Guillermo Martínez Colunga, May 2010

The flow through non-circular tubes is simulated using the radial functions method (RFM). The Giesekus model is considered to reproduce viscoelastic effects. RFM is a meshless technique that does not require homogeneous grid points. The technique successfully modeled the flow through square tubes reproducing the secondary flows observed experimentally by other researchers. Furthermore, the results are in agreement with finite element and finite volume numerical approaches. When considering high Weissenberg numbers, meshless techniques avoid the limitations of typical methods using meshes, such as capturing steep stress gradients at sudden changes in geometry.

VISCOELASTIC BEHAVIOR AND RESIDUAL STRESS PREDICTION BY CAE DURING EPOXY MOLDING
Mihaela Mihai, Michel A. Huneault, Basil D. Favis, May 2010

The residual stress is generated by the molding process of epoxy changing from liquids to solids during cure. A precise process model of these materials requires a constitutive model that is able to describe the residual stress in products such as high voltage cable accessories. This residual stress is generally classified by shrinkage in the curing reaction of monomers and the non-uniform temperature distribution in the heating and cooling process. In this study, the viscoelastic properties of a commercial epoxy resin were characterized using a dynamic mechanical analyzer (DMA) to develop master curves of stress relaxation behavior. A viscoelastic model is applied to make a prediction of the residual stress in products. The numerical residual stress or temperature distributions agree qualitatively with those measured experimentally.

CRYSTALLINITY DEVELOPMENT IN CELLULAR POLY (LACTIC ACID) IN THE PRESENCE OF SUPERCRITICAL CARBON DIOXIDE
Mihaela Mihai , Michel A. Huneault , Basil D. Favis, May 2010

This paper investigates the crystallinity development in cellular poly(lactic acid) and the effect of achieved crystalline content on its microstructure and properties. Supercritical CO2 was used as expansion agent in a twinscrew extrusion line. The crystalline contents were measured by DSC and XRD techniques and the morphology of foams by SEM. The crystallinity developed upon expansion depended on L-LA content CO2 concentration polymer flow rate and die diameter. It was shown that the crystallinity development in PLA enhances the expansion of its cellular structure. The presence of PLA crystallites within expanded cell walls lead to a peculiar 2D-cavitation phenomena.

CRYSTALLINITY DEVELOPMENT IN CELLULAR POLY (LACTIC ACID) IN THE PRESENCE OF SUPERCRITICAL CARBON DIOXIDE
Mihaela Mihai , Michel A. Huneault , Basil D. Favis, May 2010

This paper investigates the crystallinity development in cellular poly(lactic acid) and the effect of achieved crystalline content on its microstructure and properties. Supercritical CO2 was used as expansion agent in a twin-screw extrusion line. The crystalline contents were measured by DSC and XRD techniques and the morphology of foams by SEM. The crystallinity developed upon expansion depended on L-LA content, CO2 concentration, polymer flow rate and die diameter. It was shown that the crystallinity development in PLA enhances the expansion of its cellular structure. The presence of PLA crystallites within expanded cell walls lead to a peculiar 2D-cavitation phenomena.

THREE-DIMENSIONAL SIMULATION OF CRYSTALLIZATION EFFECTS IN INJECTION MOLDED SEMI-CRYSTALLINE THERMOPLASTIC PARTS
Terry L. Schwenk, May 2010

The competitiveness of companies operating in high-wage countries today is depending heavily on a fast and at the same time very precise part design. Inhomogeneous inner properties have a direct influence on the local mechanical properties and therefore also on the global part performance of injection molded parts. To enable a precise prediction of part properties a software is being developed at IKV which allows the prediction of locally determined inner properties like the morphology resulting from process parameters and geometry. The paper includes the aspects mentioned above and gives a prospect on future works in this field of simulation and materials technology.

NEW PATENTED DEVICE FOR CHECKING INJECTION MOLD VENTS
Terry L. Schwenk, May 2010

Non uniform venting is a major cause of imbalance filling of multi-cavity injection molds. The size and position of vents have historically been determined by engineers with the assistance of material manufacturers. The consistency and tolerance of mold vents are entirely in the hands of the tool designers and builders. Most of the time vents sizes position and tolerances go unchecked until there is a problem. Once it has been determined there is a venting issue the toolmaker will verify vent sizes of individual components and make adjustments. Until now there hasn’t been any way to check the venting of a mold assembly. This new device can check and verify overall vent sizing and uniformity of the mold.







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