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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

Stabilization of TPE's
Leonard Davis, May 2000

A rational approach to the stabilization of thermoplastic elastomers (TPE's) is an extension of the known technology to stabilize the constituent polymer resins. Hindered amine light stabilizers and ultraviolet light absorbers are effective in polypropylene and polyethylene. They can also be used to stabilize multiphase TPE's, based on polyolefin copolymers, against the effects of long term exposure to light and heat.

Epoxy + Montmorillonite Nanocomposite: Effect of Composition on the Catalyzed Reaction Rate
Peter Butzloff, Nandika Anne D'Souza, May 2000

Differential scanning Calorimetry was used to determine the effect of incremental change in composition of alkonium ion substituted montmorillonite clay dispersed in thermoset epoxy with a simple diamine hardener. Catalytic effects due the reactivity of the reinforcement are shown to be variable with composition. Infra-red analysis of the epoxy monomer indicate a change in the morphology of the molecular reinforcement may alter the ability of the reactants to come into contact even before the chemical reaction has begun.

Simple and Concise Design Rules for Rapid Prototyping
Barbara J. Arnold-Feret, May 2000

Shortening the design cycle by using rapid prototyping is a standard for injection molding product creation throughout the world. Developing new products while being aware of each type of prototyping technology allows the designer to judge fit, function, esthetics, economics, and product features prior to cutting a production tool; saving money and time. The use of several prototyping processes, including stereolithography (SLA) and laser sintering (SLS) are detailed with updated information on new tolerance standards and new materials.

Predictive Control of Melt Temperature Incorporating the Effect of Screw Rotation
Rickey Dubay, Janet Beyea, May 2000

Controlling the plastic melt temperature along the barrel of an injection molding machine is important for the overall product quality. In order to achieve good control performance, other process interactions such as the rotating screw should be incorporated into the controller design. The use of model-based predictive control (MPC) allows coupled processes to be model in a dynamic matrix in order to calculate the control moves to each process. By applying this control approach, higher rotating screw speeds and melt plastization back-pressure can be utilized without the effects of temperature oscillations and material degradation.

Interfacial Anchoring in Semi-Crystalline Blends
K.A. Chaffin, F.S. Bates, P. Brant, May 2000

We demonstrate that anchoring of entangled interfacial chains is responsible for toughness in immiscible blends containing a semi-crystalline component. Interfacial anchors are formed when entangled chains crystallize into lamellae, creating entanglements in the phase boundary that have chain ends secured in crystallites. The proposed toughening mechanism was demonstrated with isotactic polypropylene and polyethylene. Both scattering experiments and imaging showed that non-crystalline material placed at the phase boundary decouples the interface, diluting the number of interfacial anchors. As the degree of interfacial anchoring was reduced, the failure mode changed from bulk iPP failure to interfacial failure, reducing the tensile toughness and elongation by 40%. The interfacial structure was probed directly with peel tests. When an interfacial crack was propagated through a highly anchored interface, the 90° peel strength was 15 times greater than for a crack propagated through an interface that had no significant interfacial anchoring.

Characterization of Polyethylene Blends by Using Novel Techniques Such as the Successive Self-Nucleation and Annealing (SSA) and the Fourier Self-Deconvolution IR Spectroscopy (FSD-IR)
Juan D. Sierra, Silvio Ospina, Norberto Montoya, María del Pilar Noriega, Tim A. Osswald, May 2000

At the present, the plastic film industry has been using complex blends of Polyethylene to meet the demands of better mechanical properties, excellent sealability and adequate runnability in the processing machinery. Thus the characterization and the evaluation of processing properties are of great importance for the plastic industry. According to the present study successive self-nucleation and annealing SSA and the Fourier Self Deconvolution IR Spectroscopy, is a valuable tool for characterization of complex blends of Polyethylenes. By using the above mentioned techniques it is possible quantify metallocene Polymers and traditional LLDPEs from LDPE binary and ternary blends.

Application of the Crack Layer Model for Understanding of the Correlation between Lifetime and Creep Behavior in Polyethylene
J. Fan, D. Chen, Y. Shulkin, A. Chudnovsky, N. Jivraj, K. Sehanobish, May 2000

A closely coupled system comprising of a crack and a process zone (PZ), i.e., a domain of crazed material ahead of the crack, commonly observed in polyethylenes (PEs), constitutes the crack layer (CL). According to the CL theory, slow crack growth in polyethylenes is largely a result of degradation of the process zone material. The CL theory has been applied to model some features of slow crack growth in PE, such as the discontinuous manner of the process, the widely reported specifics of fracture surface morphology, the stress and temperature dependence of lifetime, as well as the crack speed-stress intensity factor (SIF) relation. In the present work, a simplified version of the CL theory is employed to explain and generalize the correlation between the lifetime of PE pipes in brittle mode fracture and the so-called Creep Rate Deceleration Factor (CRDF) of drawn PE.

Ductile Failure and Delayed Necking in Polyethylene
W. Zhou, D. Chen, Y. Shulkin, A. Chudnovsky, N. Jivraj, K. Sehanobish, S. Wu, May 2000

Analysis of polyethylene (PE) pipes ductile failure (ballooning) suggests that it is directly related to the delayed necking phenomena and time to ductile failure of PE pipe can be evaluated as the time to delayed necking. The necking in polyethylene (PE) is studied under displacement control (ramp test) and load control (creep) conditions. In ramp tests the dependence of the yielding and drawing stresses on strain rate are established using specimens of a European PE 100 pipe grade HDPE, It is shown that both stresses decrease with decrease of strain rate and approach a common value, the characteristic stress. In creep tests of the above material, the relation of time-to-necking vs. applied stress is obtained. It is proposed to employ the testing procedure on tensile specimens for estimation of time-to-ductile failure in PE pipes. The characteristic stress is suggested to be an indicator of the ductile-to-brittle transition in failure mechanism.

A Practical Fiber Optic Sensor to Monitor Resin Cure and Interphase Formation
Joseph L. Lenhart, John H. van Zanten, Joy P. Dunkers, Richard S. Parnas, May 2000

A fluorescent probe, covalently grafted to glass, is used to study the glass / resin interphase region near the surface. A shift in the fluorescence maximum during resin cure can be monitored when the grafted dye is immersed in epoxy. The position of the fluorescence maximum is used to detect a difference between the bulk resin and interphase. To make the technique practical as a cure sensor, the dye can be grafted to a glass fiber optic.

Structural Order and Charge Transport in Polymers
Arthur J. Epstein, Vladimir N. Prigodin, May 2000

It has long been known that polymers have a structural order intermediate between that of insulators and that of amorphous materials. We show how this intermediate type of order leads to anomalous charge conduction properties for insulating, semiconducting, and metallic polymers. Concepts such as fractal dimensionality and mesoscopic order are introduced and their unusual predictions for variation of conductivity and dielectric constant with temperature and frequency are presented. A comparison with experimental results for undoped and doped polymers is presented.

An Analysis of the Heat Exchange Phenomena in Heavy Gauge Thermoforming-Part I
Donald Hylton, Tameka Spence, Errol Sampson, Kyra Dorsey, Reginald Parker, Thorsten Emyael, May 2000

A comprehensive analysis of the heat exchanges between an instrumented Aluminum mold and various thermoforming materials were made during controlled heavy gauge production trials. Five materials Impact Polystyrene, High Density Polyethylene, PETG, ABS and Impact Polypropylene Copolymer were evaluated. Heat flux was calculated. Experimental variables were quiescent and circulated ambient air, mold and coolant temperatures.

Durability Study of Conductive Copper Traces within Polyimide Based Substrates
Elena Martynenko, Wen Zhou, Alexander Chudnovsky, Ron Li, Larry Poglitsch, May 2000

Flexible printed circuitry (FPC) is a patterned array of conductors supported by a flexible dielectric film made of high strength polymer material such as polyimide. The polyimide core is the premier dynamic structure membrane with an extraordinary ability to withstand continuous. Flexing for hundreds of millions of flexing cycles, fatigue performance and reliability are paramount issues in the design and manufacturing of FPC. In the composite structure, the conductive layers are more vulnerable to failure due to their lower flexibility compared to polyimide film. This paper is focused on the reliability assessment of FPC based on the high cycle fatigue resistance. Fatigue resistance of various material systems has been analyzed as a function of temperature and frequency. The fatigue characteristics of selected material systems are summarized in the form of S-N diagrams. Failure mechanism observations are discussed and complete fracture analysis is presented. In various FPC systems, it has been found that the changes take place in FPC failure mechanisms from well developed and aligned through the width cracks at low temperature to an array of multiple cracks with random sizes and locations at high temperature. Comparative analysis of various material systems based on fatigue performance is presented.

True Stress-Strain-Temperature Diagrams of Polyolefins and Their Application in Acceleration Tests for Lifetime Prediction
J. Liu, Z. Zhou, X. Niu, A. Chudnovsky, May 2000

True stress - strain - temperature (TSST) diagrams are being used as a tool for characterizing thermo-mechanical behavior of polymers. TSST diagrams are developed for materials that undergo necking by consideration of a material point perspective. In the present work TSST diagrams of three polyolefin types, Polyethylene, PE, polypropylene, PP, and polybutylene, PB, are constructed and their relevance to accelerated lifetime testing discussed. It is found, in contrast to PE and PP, the changes in PB deformation behavior raises the issue of validity of lifetime predictions of PB at temperatures below 70°C based on testing at temperatures above 70°C.

The Effect of Chemical Degradation on Physical Properties and Fracture Behavior of Poly(ethylene-co-carbon monoxide) and Poly(1-butene)
X. Niu, E. Martynenko, A. Chudnovsky, S.H. Patel, S.S. Stivala, May 2000

Chemical degradation is one of the dominant mechanisms of aging in polymers. To prevent a premature catastrophic failure of polymers in durable applications, an understanding of the causes and kinetics of chemical degradation are required. UV accelerated oxidation has been applied in this work to study the effect of oxidative degradation on physical and mechanical properties, such as crystallinity, density, toughness and deformability of unpigmented, unstablelized Poly (ethylene-co-carbon monoxide), ECO, and Poly (1-butene), PB. The correlations between the variation of physical, mechanical properties, and reduction of molecular weight are reported. The effect of oxidative degradation on fatigue crack growth rate and build-up of residual stresses due to densification is also addressed.

Notch Sensitivity of Pipe Grade Polyethylene and Polybutylene
X. Niu, D. Chen, W. Zhou, A Chudnovsky, N. Jivraj, May 2000

To characterize the notch sensitivity for short-term (e.g. notch sensitivity under dynamic impact conditions, sensitivity to failure under rapid crack propagation conditions) and long-term (e.g. slow crack growth resistance, pipe lifetime under creep conditions) strength of thermoplastics, the ratio of the energy-to-break in tensile impact test for notched and unnotched specimens (short term notch sensitivity factor) and the similar ratio for the time-to-failure in tension creep test (long term notch sensitivity factor) are introduced. The limits of these ratios as the notch length approaches zero are called the notch sensitivity factors. The test procedure is developed and applied to determine the factors for one pipe grade polyethylene (PE) and one pipe grade polybutylene (PB). The results indicate that both materials show short term notch sensitivity, and that PB shows very high long term notch sensitivity in contrast to PE.

Predicting Thermal Degradation of PVC Compounds during Injection Molding
Jose L. Garcia, Kurt W. Koelling, James W. Summers, May 2000

The goal of this study was to determine the degree of degradation during PVC injection molding and to compare the results with a computational model. It was found that a good agreement between experimental and computational results was obtained only if the reaction was assumed to be more thermally sensitive than found in literature. The results from this study show that during injection the activation energy for degradation was 65 kcal/mol, compared to 17-30 kcal/mol found in literature for quiescent systems.

3-D Simulation of Thin-Wall Injection Molded Part by CAE
Sooyoung Cha, Francis S. Lai, May 2000

This work reports the results of CAE simulation of thin-wall injection molded part by 3D TIMON. The model used in this simulation was a speaker grille that has thin wall and many tiny openings (net) for sound through them. These openings cause unfavorable weld lines. Effects on weld lines and effects of the number and location of gates were discussed.

An Investigation of the Rotomoldability of New Generation Polyethylene
E.Takács, M. Kontopoulou, D. Annechini, J. Vlachopoulos, May 2000

Rotational molding is a fast growing process with a constant demand for new materials. As a result of the recent advances in the metallocene single site catalyst systems, a new generation of polyethylenes with unique molecular structure has been developed. The present study compares the rotomolding characteristics of polyethylenes made by metallocene and conventional catalysts.

Profile Extrusion of Highly Filled Recycled HDPE
Zach Charlton, John Vlachopoulos, Dedo Suwanda, May 2000

Recycled high density polyethylene (HDPE) filled with up to 70 wt% rice hulls was compounded and tested for dynamic shear properties on a parallel plate rheometer. A 60 wt% formulation was extruded through two profile dies. Extrudate tearing occurred at all throughputs. The magnitude of the tearing increased with increasing throughput and decreasing land temperature. Observations, 2-dimensional finite element and fully 3- dimensional finite volume simulation suggest the tears are most severe where the wall shear stress is relatively lower.

An Anamoly in the Lifetime-Temperature Relation of a Polybutylene for Pipe Applications
X. Niu, W. Zhou, Y. Shulkin, A. Chudnovsky, N. Jivraj, May 2000

A comparative analysis of polyethylene (PE) and polybutylene (PB) tensile behavior at various temperatures is reported. It is noted that PB exhibits different tensile behavior below and above 70 °C (transition temperature). This is in contrast with PE that does not change its tensile behavior over the entire temperature range considered. PB also exhibits different crack growth mechanisms at 110 °C (above the transition temperature) than that at 50 and 23 °C (below the transition temperature). The fatigue lifetime for PB at 110 °C is observed to be more than ten times the fatigue lifetime at 23 °C. Thus the commonly accepted opinion that temperature is always an accelerating factor of fracture process is not applicable for PB within the above range of temperatures. It is suggested that the observed anomaly in temperature acceleration of fracture in PB is related to the reported transition of tensile behavior around 70 °C







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