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

Predictive Control of Cavity Pressure during Injection Filling
Rickey Dubay, May 2001

Cavity pressure is a good indicator during injection molding for achieving high part quality and maintaining consistent part weight and overall dimensions. Its trajectory during the filling phase of injection is highly dependent on other molding variables. The repeatable control of cavity pressure is therefore vital for producing parts with tight tolerances. A predictive controller for cavity pressure control during cavity filling was developed and implemented. The controller was able to provide cavity pressure ramp rates ranging from 10 to 35 KPa/ms under high injection speeds.

Metallocene Catalyst Mixture for Propylene Polymerization
Mariana Poloponsky, Érica Gervasoni Chaves, Maria de Fátima V. Marques, May 2001

Metallocene mixtures have been used in order to design polymers with broader polydispersity, intending to improve polymer processing. In this work, the properties of isotactic polypropylene obtained by a mixture of (1) SiMe2(Ind)2HfCl2 and (2) SiMe2(Ind)2ZrCl2 , in different proportions, were investigated. The catalyst activities for the mixtures were lower compared to the individual complexes. We observed polymers showing broader molecular weight distribution, with a bimodal Gel Permeation Chromatography curve at 50/50 (1)/(2).

Syndiotactic Polypropylene from Metallocene Mixture
Érica Gervasoni Chaves, Mariana Poloponsky, Maria de Fátima V. Marques, May 2001

Considering the real interest in syndiotactic polypropylene (s-PP) and the possibility to design polymers with desired properties using metallocene catalyst mixtures, this work investigates the characteristics of s-PP produced by a mixture of (1) Et(Flu)(Cp)ZrCl2 and (2) Ph2C(Flu)(Cp)ZrCl2 in different proportions. By the results we observed that the polymers obtained from the mixed systems showed higher molecular weight and broader molecular weight distribution than the isolated polypropylenes.

Thermoset Filling Imbalances in Geometrically Balanced Runner Systems
David A. Hoffman, John P. Beaumont, May 2001

Shear induced variations created within runner systems dramatically affect the filling of the industry standard geometrically balanced runner systems. These variations not only cause imbalances in cavity filling, but may also impact the polymer curing properties and the mechanical properties of the molded product. This paper reveals the severity of the imbalance within thermosetting materials, its potential effect on the molded product, and a new technique used to solve the imbalances.

Spatially Resolved Studies of Polymer Film Dynamics
Boris B. Akhremitchev, Sabah Al-Maawali, Jason E. Bemis, Gilbert C. Walker, May 2001

We have developed several new scanning probe methods for analyzing polymers at surfaces. We present a technique for studying single polymer chains. We describe model for polymer dynamics on an AFM tip, and applications of the technique to analysis of polymer surface polydispersity and irreversible aspects of adhesion. We also describe developments in apertureless near field scanning infrared microscopy (ANSIM), to obtain IR spectra of surfaces at high spatial resolution.

Syndiotactic Polypropylene Using Different Supported Metallocene Catalyst
Queli C. Bastos, Simone C. Moreira, Juliana D. Rego, Maria de Fátima V. Marques, May 2001

Polymerizations of propylene were carried out with ?2C(Flu)(Cp)ZrCl2 catalyst supported on silica, sodic modernite (NaM) and ZSM-5. The molecular weight, molecular weight distribution, melting point and crystallinity of the obtained polymers and also catalytic activity were examined. The results report very high activities for the heterogeneous systems, specially with ZSM-5 as carrier. Higher melting point and crystallinity degree were presented in polypropylene synthesized with the catalyst supported on NaM.

Dimensional Stability of LDPE Foams: Modeling and Experiments
Chi-Tai Yang, Kevin L. Lee, S.-T. Lee, May 2001

The thickness change of extruded LDPE foam to the blowing agent and air counter diffusion during the post-extrusion aging process is modeled. The blowing agent and air counter diffusion equations are coupled with the viscoelastic equations to model the foam volume shrinkage and recovery processes in a closed-cellular low-density LDPE foam. The variables studied include polymer elastic and viscous constants, foam sheet thickness, cell count and foam density. The mathematical model is also compared with experimental data.

Coaching and Mentoring: Change Management
John R. Szymankiewicz, Jill E. Sackman, May 2001

In a global economy featuring mass customization, ubiquitous information, and extreme price and service competition, many companies have found it paramount to remain flexible. Flexible to answer customer needs and wants faster, better, cheaper. For many companies the required flexibility demands organizational change at a rapid rate. Organizational change, if not managed properly can cause serious internal and external performance issues. Coaching and mentoring can be used to manage, and even drive, change in your organization while building value and employee involvement in the change.

Failure Analysis Case Study - A Systems Solution
Michael P. Sepe, May 2001

Failure analysis typically employs a series of appropriate tests that result in a conclusion about the cause or causes of a product failure. Often the problem involves an interaction between the plastic part and other components in the product or between the plastic part and application conditions. Identifying these interactions is an important part of developing a solution that resolves the problem without unduly increasing costs. This paper outlines a case study in which a proper analysis of the failure mode and knowledge of commercial alternatives led to multiple options for a solution.

What Position on the Viscosity Curve Is the Most Repeatable with Respect to End of Fill Cavity PSI
Sean Mertes, Charley Carlson, John Bozzelli, Mike Groleau, May 2001

For many years, educators in the injection molding industry have suggested that higher injection speeds result in more stable processes when using 2-Stage processes. However, little data exists to verify this assertion. In this paper, injection speeds were varied on a 2-Stage process. Cavity pressure was measured at the end of the cavity to evaluate process stability in the face of several process perturbations. Results supported the claim that higher injection rates reduced overall process variation.

Toughening of Polypropylene with Calcium Carbonate Particles
W.C.J. Zuiderduin, C. Westzaan, H. Huetink, R.J. Gaymans, May 2001

In this paper the influence of precipitated calcium carbonate (PCC) particles on the toughening of polypropylene has been studied. It has been shown that the addition of the PCC particles increase the stiffness of the system and at the same time increase the impact resistance. The brittle-to-ductile transition temperature (TBD) was lowered considerably by increasing the calcium carbonate concentration. The debonding of the calcium carbonate particles prior to the yield stress is the dominating step in the toughening mechanism.

Effect of Crystallization Conditions on Spherulitic Texture and Tensile Properties of sPS/PPO Blends
G. Dutt, K.M. Kit, May 2001

Syndiotactic polystyrene (sPS) and poly(phenylene oxide) (PPO) blends, miscible in melt state, were crystallized from melt as well as quenched state at different temperatures. The effect of processing conditions on spherulitic texture, ultimate tensile properties and the mode of fracture was studied. The study suggests that by varying composition and processing conditions in melt miscible blends it is possible to control amorphous domain sizes, which is critical in achieving better mechanical properties

CPI In-Line Compounding Systems
Marvin J. Voelker, Charles D. Weber, May 2001

Composite Products, Inc. has commercialized in-line compounding technology to produce long fiber thermoplastic composites. Turnkey systems continuously compound thermoplastic resin with reinforcements ie. ½ inch chopped glass, carbon or natural fibers to produce finished composites with outstanding toughness. The separation of thermoplastic melt processing and the introduction of glass is key to fiber length retention. The patented technology provides molders the ability to maintain the highest level of physical properties while molding appearance parts. or strongly reduce

Blends of Recycled Polyethylenes and Metallocene Impact Modifiers for Rotational Molding
E. Takács, M. Kontopoulou, J. Vlachopoulos, E. Voldner, K. Nichols, May 2001

This paper describes the development of blends of recycled polyethylenes suitable for rotational molding. The blends consist of recycled post-industrial polyethylene resins and polyolefin plastomer impact modifiers, produced by single-site (metallocene) catalysts. The rheological properties of the blends were found to be favorable for rotational molding. Rotomolded parts provided satisfactory low temperature impact strength and good tensile properties.

Toughening Mechanisms in Fiber-Containing Impact Modified Polymers
Guoxin Sui, Shing-Chung Wong, Chee-Yoon Yue, May 2001

An attempt was made to separate the toughening arising from the presence of fiber and that from the toughened matrix using the essential work of fracture. Toughening mechanisms with fiber inclusions were found to be associated with fiber bridging, debonding and pull-out. It was concluded that such fiber toughening would yield a flat curve when the specific total fracture work was plotted against the ligament length. The technique was able to produce fruitful information regarding design for property synergism in impact modified nylon 6,6.

Prediction of Transient Material Functions of PP Resins Using the Multi-Mode PTT Molecular Network Model
Jaime Bonilla Ríos, Rodolfo Mier Martínez, May 2001

The transient rheological material functions [?(t,?),N1(t,?),?e(t,?) ] of three PP resins are predicted using the multi-mode Phan-Thien and Tanner (PTT) molecular network model. The study also includes the standard quality properties (MFI, XSP, GPC, and DSC) of the resins. The model was coded in C-language, validated with published data (Phan-Thien, 1978) and then used for the prediction of transient material functions. The predictions are in good agreement with the resins' rheological data.

An Experimental Comparison of the Improved Mixing Obtained from a New Barrier Screw Design
Kevin R. Slusarz, Michael R. Thompson, John P. Christiano, May 2001

A comprehensive study looking at both distributive and dispersive mixing for a new screw design was done on a single screw extruder. The findings showed an improvement in mixing performance with this new style barrier screw over a conventional barrier screw design. Mixing performance was evaluated by means of microscopic analysis. To better quantify mixing three different systems will be studied; distribution of a pigment, distribution of an inorganic filler, and dispersion of a minor component in an immiscible blend.

Probing Local Chemical Interactions and Bond Energies with AFM
James D. Batteas, Chang Xu, James Helt, Marcus K. Weldon, May 2001

Atomic force microscopy has been utilized to examine molecular interactions of native and OTE modified silica surfaces under aqueous conditions. For native silica, depending on pH, the measured adhesion consists of convolutions of different interactions, including hydrogen bonding, anionic hydrogen bonding and covalent bond breaking. Modification with OTE allows for hydrophobic interactions to be probed, and time dependent adhesion results suggest the possibility of probing molecular reorganization within the contacts.

Polymer Blend Morphology by Dynamic AFM
Andy H. Tsou, May 2001

The reduction in lateral forces during scanning allows the tapping-mode AFM to be an extremely useful tool for evaluating the morphology of polymer blends. Without staining or etching, rubber/plastic domains and fillers in cryo-faced polymer blends can be obtained with strong contrast. Subsequent image processing and measurement of AFM micrographs can provide quantitative structural parameters in blends. Filler partition in polymer blends, compatibility and interfacial tensions between polymers, and filler and phase networking can be measured.

Chemical Imaging with near Filled Scanning Optical Microscopy
Stephan J. Stranick, D. Bruce Chase, Chris A. Michaels, May 2001

The ability to measure chemical bond changes on the nanometer scale is of critical importance for the characterization of catalytic processes, catalytic materials, and surfaces relevant to materials and biological problems. Our goal has been to develop a technique for in-situ, non-destructive measurements of site-specific chemistry on the nanometer scale. The strategy for realizing this goal involves coupling the high spatial resolution of near-field scanning optical microscopy (NSOM) with the chemical specificity of vibrational spectroscopy.

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