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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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.
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.
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 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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
A small-scale test methodology for the determination of plastic pipe resistance to rapid crack propagation (RCP) is proposed. Like the full-scale and S4 tests, this test determines the critical pressure (pc) and transition temperature (Tc) of RCP. At the same time it is an inexpensive and safe small-scale alternative to the standard tests. The internal pressure in the proposed test is kept constant with practically no decompression. Therefore the pressure and crack length involved in the evaluation of dynamic toughness of material are directly measured at the crack arrest. Thus it allows for the evaluation of the material resistance to RCP (dynamic toughness) in terms of the energy release rate (ERR) at crack arrest, in addition to the determination of pc and Tc. Applications of the proposed characterization of the RCP resistance for PE-100 are discussed.
An analytical solution has been developed to predict the flow of ƒ??Nƒ?layer coextruded encapsulated polymers through a round tube such as interface positions and pressure gradients. The predictions show fairly good agreement with the experimental measurements for two layer coextrusion with an equal flow rate in each layer.The effects of flow ratio total flow rate and layer composition on the interface position within the die and on the pressure gradient are examined. The knowledge of interface position and pressure gradient is important for die design and process optimization.
Temperature strongly affects the mechanical properties of pipe grade polyethylene (PGPE), such as strength and toughness. It is observed in this study that the temperature also affects the mechanisms of slow crack growth (SCG). A change in the mechanism of SCG is observed at certain temperature, named Crack Growth Transition Temperature (CGTT). The CGTT of the cold drawn (oriented) PGPE appears to be significantly higher than room temperature. At the temperature above CGTT the crack propagates discontinuously, stepwise, whereas at the temperature below CGTT the crack grows continuously. The slope of crack growth rate vs. stress intensity factor (SIF) is also noticeably different for temperatures above and below CGTT. The existence of CGTT implies certain limitations for commonly used extrapolation of SCG and lifetime data from the elevate temperature of an accelerated testing to the room temperature across CGTT.
The most recent results for the measurements and modeling of thermal diffusivity of thermoplastics under injection molding conditions are presented. The method is based on the inverse numerical solution of the differential equation that describes the cooling process of the injected part. The effect on the thermal diffusivity of different cooling rates across the thickness of the injection part the cavity pressure the thickness of the part the wall temperature of the mold and the melt temperature were investigated and included as parameters in the improved mathematical model for the description of the thermal diffusivity. The model was validated for polypropylene in a wide processing window.
A new laser welding process that uses a real time closed loop control system of the process by monitoring thermal emissions directly from the weld region. These emissions are captured, measured, interpolated, and thus correlated to a known temperature. The process has been applied on laser welding a test box molded from thermoplastic PBT material, Ultradur B4300G6.Robustness of the process and the quality of the weld joint is evaluated by performing burst testing of the welded boxes, after welding the box samples at various surface temperatures. The experiment has identified optimum surface temperature regime for laser welding a material for a given weld section design. Microscopy study shows microstructure of good weld joint and poor weld joints
Venkatesh Aungadu Kuppuswamy , Stephen L. Spanoudis , Marian Petrescu , Ben Nagaraj, May 2010
This paper evaluates several simulation approaches in Moldflow, including the use of CRIMS (Corrected Residual In-Mold Stress) data, to better predict warpage in injection-molded parts. The evaluation includes a simulation matrix in which warpage is predicted by part geometry, process conditions, material and simulation method. In addition, selected injection-molded parts are scanned at high resolution to gather actual 3-D warpage data. The paper additionally describes novel methods for making comparisons between the predicted and actual data sets within an interactive CAV environment to determine the effectiveness of CRIMS.
V. Schöppner, E. Enns, K. Anger, E. Giese, May 2010
A large number of different formulations of PE have been tested in load (creep) and displacement controlled (ramp) conditions. A certain symmetry (ƒ??mirror reflectionƒ?) between the stress ?Ÿ vs. log ?æ‹?? in ramp and creep tests and the stress ?Ÿ vs ductile failure tf in creep is observed. A procedure for prediction of PE long-term creep behavior and lifetime in ductile failure based on ramp and a short-term creep tests is formulated. The procedure employs Eyringƒ??s model for connecting stress, strain rate and temperature in yielding combined with the observed symmetry. A theoretical basis for the procedure and its experimental validation is presented.
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Any article that is cited in another manuscript or other work is required to use the correct reference style. Below is an example of the reference style for SPE articles:
Brown, H. L. and Jones, D. H. 2016, May.
"Insert title of paper here in quotes,"
ANTEC 2016 - Indianapolis, Indiana, USA May 23-25, 2016. [On-line].
Society of Plastics Engineers
Available: www.4spe.org.
Note: if there are more than three authors you may use the first author's name and et al. EG Brown, H. L. et al.
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