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
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.
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.
A NEW FAMILY OF STYRENIC BLOCK COPOLYMERS FOR ELASTOMERIC FILMS IN PERSONAL CARE APPLICATIONS
Nanjia Zhou, Andrey Beyle, Christopher C. Ibeh, May 2010
Styrenic block copolymers are increasingly being used in the production of elastomeric films for personal care and hygiene applications. In recent years, with severe fluctuation on the supply side regarding availability and price for isoprene, butadiene, and styrene monomers, manufacturers and end-users of block copolymers have searched for ways to reduce their costs and maintain high levels of elastic performance. This paper introduces a new family of styrene-isoprene-butadiene-styrene (SIBS) quador tetra-block polymers to produce lower cost high performance products when compared to styrene-isoprene-styrene (SIS) copolymers. These new SIBS quad-block polymers are compared to triblock polymers with mixed isoprene-butadiene S(I/B)S structures.
VISCOELASTIC PROPERTIES OF EPOXY AND VINYL ESTER NANOCOMPOSITES
Nanjia Zhou , Andrey Beyle , Christopher C. Ibeh, May 2010
The influence of different nanoparticles (nanoclay silicon carbide) concentrations on viscoelastic properties of vinyl ester and epoxy nanocomposites and nanofilled conventional fiber reinforced polymers were studied using Differential Mechanical Thermal Analysis (DMTA). The shift of the glass transition temperature with addition of nanoparticles was detected. The dependencies of storage and loss moduli on temperature on type of nanoparticles and on their concentrations are compared. Maximal tangent of mechanical loss angle was found changed with concentrations of nanoparticles.
FAILURE OF HUMAN BIOPOLYMERS
Yu-Te Liao, Shi-Chang Tseng, Meng-Chih Chen, Chao-Tsai Huang, Yuan-Jung Chang, May 2010
Failure of Human Biopolymers was introduced to the SPE Failure Analysis and Prevention Special Interest Group at the 2009 ANTEC. It broadens failure of synthetic polymers (plastics) to include biopolymers that control human life. It is a vast field in which synthetic polymers and human biopolymers intersect. Both polymer types share susceptibility to failure by oxygen, free radicals, UV and X-ray radiation, heat and stress. Combining each type with the other benefits both. The basics will be reviewed briefly and other aspects of the subject will be presented.
A STUDY OF THERMALLY AND FLOW INDUCED RESIDUAL STRESSES IN INJECTION MOLDING
Yu-Te Liao , Shi-Chang Tseng , Meng-Chih Chen , Chao-Tsai Huang , Yuan-Jung Chang, May 2010
During the injection molding process, mold filling may introduce residual stresses. And the sequential cooling process may result in thermal stresses. Some cases show flow induced residual stresses dominate the final stresses. Sequential multi-component molding is one of good examples of thermal stresses. On the other hand, in the higher speed injection molding cases, higher shear stresses may be the major contribution to final residual stresses.In this study, both CAE simulation and real experiments will be conducted and compared for some cases. Specifically, how the polymer properties and process conditions affect the stresses and warpage will be discussed.
PROCESSING INTEGRAL-SKIN POLYPROPYLENE FOAMS UTILIZING EXTRUSION- ASSISTED DIRECT-FOAMING ROTATIONAL MOLDING
Emad Abdalla , Remon Pop-Iliev, May 2010
The extrusion-assisted direct-foaming rotational foam molding process maximizes the synergistic effects resulting from the recently-invented deliberate conjunction of extrusion melt-compounding and rotational foam molding aiming towards introducing timeand- energy efficient manufacture of integral-skin rotomolded foams. Multiple polypropylene (PP)-based foamable and non-foamable formulation combinations were subjected to a battery of planned experimental trials utilizing a custom-built industrial-grade lab-scale experimental setup. The obtained foam morphologies were characterized in terms of foam density, average cell size, and average cell density.
A NEW ELECTROMAGNETIC DYNAMIC MICROCELLULAR FOAMING TECHNOLOGY FOR PP/HDPE BLENDS
Ping Zhang , Nanqiao Zhou , Shengping Wen , Mingyi Wang , Wenli Zhu, May 2010
Polypropylene (PP) has poor foamability because of its low melt strength and high crystallinity. To obtain fine microcellular foams, a new electromagnetic dynamic microcellular foaming technology was used in this paper. A dynamic shear in the axial direction induced by the rotor vibration was vertically superposed on the melt flow direction, and its effects on the microcellular foaming process and cell structure were investigated theoretically and experimentally. The results showed that the shear rate and melt strength enhanced as the vibration amplitude and frequency increased, which led to great improvement of the foamability and ultimate microcellular structure.
STATISTICAL MODEL PREDICTING WATER VAPOR TRANSMISSION RATES OF HIGH-BARRIER-COATED PAPERS
Kimmo Lahtinen , Jurkka Kuusipalo, May 2010
Moisture barrier properties of extrusion-coated papers including EVOH-layer were investigated. The moisture barrier of EVOH is considerably compromised in the presence of moisture because the highly polar water molecule tends to hydrogen bond with the EVOH polar groups followed by plasticization of the polymer. To prevent the moisture effect the EVOH-layer is typically covered with a non-polar skin layer. In addition to its own barrier the skin layer improves the barrier of EVOH by decreasing its moisture concentration. This study introduces a practical model that estimates water vapor transmission rates (WVTR) of high-barrier-coated papers with an extrusion-coated EVOH-layer. The skin layer effect is taken into account when the WVTR is estimated as a function of coating structure at specific atmospheric conditions.
STATISTICAL MODEL PREDICTING WATER VAPOR TRANSMISSION RATES OF HIGH-BARRIER-COATED PAPERS
Kimmo Lahtinen , Jurkka Kuusipalo, May 2010
Moisture barrier properties of extrusion-coated papers including EVOH-layer were investigated. The moisture barrier of EVOH is considerably compromised in the presence of moisture because the highly polar water molecule tends to hydrogen bond with the EVOH polar groups followed by plasticization of the polymer. To prevent the moisture effect, the EVOH-layer is typically covered with a non-polar skin layer. In addition to its own barrier, the skin layer improves the barrier of EVOH by decreasing its moisture concentration. This study introduces a practical model that estimates water vapor transmission rates (WVTR) of high-barrier-coated papers with an extrusion-coated EVOH-layer. The skin layer effect is taken into account when the WVTR is estimated as a function of coating structure at specific atmospheric conditions.
INFLUENCE OF PULSATILE PRESSURE INDUCED INJECTION MOLDING ON PARTS PERFORMANCE
M. Meysami, C. Tzoganakis, May 2010
A self-made pulsatile pressure induced injection molding machine was adopted to explore the relationship between mechanical property and morphology for low-density polyethylene injected moldings. The main processing variables for pulsatile pressure induced injection molding are vibration frequency and vibration pressure amplitude. The experimental results show that the weights of the parts increased with the introduction of pulsatile pressure. The mechanical properties improved. The melt peak became wider and the melt point moved to high temperature with the increase of piston rod vibration amplitude/frequency.
DEVULCANIZATION OF RECYCLED TIRE RUBBER CRUMB WITH SUPERCRITICAL CO2: CURING BEHAVIOR MECHANICAL PROPERTIES AND DEGREE OF DEVULCANIZATION
M. Meysami , C. Tzoganakis, May 2010
In this work the devulcanization of tire rubber crumb was studied by using an industrial scale twin screw extruder. A reasonably high throughput extrusion process has been developed and the effect of processing conditions has been studied. The effects of different screw configurations screw speed and feed rate on the stability of process have been investigated. Crosslink density and percent of devulcanization of different samples are measured. Curing behavior tensile strength and elongation at break of different compounds consisting of blends of virgin rubber with devulcanized crumb have also been evaluated.
DEVULCANIZATION OF RECYCLED TIRE RUBBER CRUMB WITH SUPERCRITICAL CO2: CURING BEHAVIOR, MECHANICAL PROPERTIES AND DEGREE OF DEVULCANIZATION
M. Meysami , C. Tzoganakis, May 2010
In this work the devulcanization of tire rubber crumb was studied by using an industrial scale twin screw extruder. A reasonably high throughput extrusion process has been developed and the effect of processing conditions has been studied. The effects of different screw configurations, screw speed and feed rate on the stability of process have been investigated. Crosslink density and percent of devulcanization of different samples are measured. Curing behavior, tensile strength, and elongation at break of different compounds consisting of blends of virgin rubber with devulcanized crumb have also been evaluated.
NATURAL FIBER REINFORCED THERMOPLASTIC FOAMS A NEW MATERIAL GROUP FOR LIGHTWEIGHT STRUCTURES
Shi-Qing Wang, P. Boukany, S. Ravindranath, Y. Wang, May 2010
Injection molding of thermoplastic foams is not new, e.g. /1 4/. Nevertheless it is well known, that the tensile properties are decreasing due to the weakened cross section of a stressed foamed structure. Putting glass - fibers into the compound to compensate this disadvantage means an increasing weight. A part of the lightweight performance will be lost. A solution could be, to take natural fibres as reinforcement for thermoplastic foams to compare this disadvantage. The main task of the recent studies was to foam compounds made of different natural fibers and polypropylene. Blowing agents of different producers have been taken to process the polymer specimen. The results of the material tests show that composites made of natural fiber foam have a potential to become a suitable material for lightweight constructions.
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