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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Viscoelastic Material Characterization at Large Deformation
New method was developed for measuring stress-strain at large deformation typical for thermoforming. Method is similar to plug assisted forming with both large strain and high strain rate. Numerical method was developed to get use of reverse engineering for fitting of non-linear parameters of suitable viscoelastic model. The aim of the method is providing reliable data for computer simulation of thermoforming.
Predictive Control of Cavity Pressure during Injection Filling
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.
Syndiotactic and Commercial Isotactic Polypropylene Blends
The development of syndiotactic polypropylene (s-PP) was stimulated with the advent of metallocene catalysts. This material exhibits special mechanical and optical properties, like higher impact strength and higher clarity. These characteristics can be used to improve the commercialization of polypropylene produced nowadays. In this work syndiotactic polypropylene was synthesized by ?2C(Flu)(Cp)ZrCl2/MAO system. The resulting polypropylene was mixed with a commercial isotactic polypropylene, at different proportions, resulting in blends with improved processability.
Metallocene Catalyst Mixture for Propylene Polymerization
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
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
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
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.
Fusion Mechanism in Rigid PVC
A classic approach for studying network effects in carbon black containing rubber was applied to PVC with stabilizer. This approach involves measuring the shear modulus with increasing strain. In carbon black containing rubber, the modulus drops dramatically at a critical strain level. This is known as the Payne effect"  and is associated with the break-up of the carbon black network. PVC that was fused to different levels in a bowl mixer shows exactly the same behavior and the drop point correlates very well with the fusion peak in the mixing bowl. The relationship between network effects and fusion in PVC will be discussed."
Syndiotactic Polypropylene Using Different Supported Metallocene Catalyst
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
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
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
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
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
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.
In-Line Compounding: Effect of Screw Design on Control Pressure Stability
In-Line" compounding is defined as any process in which both the compounding and the forming steps are performed at the same time. For these applications line stability is crucial and greatly effected by equipment selection and design. Presented is a brief overview of in-line compounding including control methods and factors effecting line stability. The pumping efficiency of various screw elements is established and their effect on control pressure stability examined. A modified screw design is presented which is found to produce a more stable control pressure."
Effect of Crystallization Conditions on Spherulitic Texture and Tensile Properties of sPS/PPO Blends
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
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
Conductive TPO for Electrostatic Painting
The TPO (Polypropylene/Elastomer) market for injection molded automotive bumper fascia is driven by cost reduction, a balance of physical properties, ease of processability, and desirable aesthetics. Global volume for this application was approximately 740 MM lbs. in 1999, nearly half of which is electrostatically painted. Decreased application costs, increased productivity, and reduced environmental emissions can be realized through system optimization. This report describes the rheological and morphological phenomena governing the development of a conductive TPO (CTPO) for enhanced electrostatic painting.
Blends of Recycled Polyethylenes and Metallocene Impact Modifiers for Rotational Molding
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
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.
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