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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Processing Ignition-Resistant Polystyrene Resins in Injection Molding Machines
The demand for ignition-resistant polystyrene resins (IRPS) continues to increase. Moreover, economics at the molder are requiring that these materials cycle faster and still produce high-quality parts. A new high-flow IRPS resin was developed to meet these needs, and this paper describes a plasticating screw design and the process conditions for enhanced performance and improved economics for this resin.
The Effect of a Worn Feed Casing on Plasticating Extrusion
With continued use, a worn feed casing can cause severe rate reductions and unstable operation of plasticating extruders. This paper will present the performance of a commercial extruder with a worn feed casing, and laboratory experiments that show the factors that affect plasticating performance.
Influencing the Foam Structure of CO2-Blown Polypropylene Sheets
An investigation has been conducted to analyze the influence of different process parameters as well as material properties on the structure of CO2-foamed polypropylene sheets. The use of a linear and a branched polypropylene shows the influence of the rheological melt properties on the foam density and the structure. Using the branched polypropylene, densities down to 140 kg/m3 have been achieved. These samples also show a finer and more homogeneous foam structure than the samples made with the linear polypropylene.
Control of Morphology of Polypropylene and Noryl Blend via Melt Mixing
Morphological development of polypropylene/Noryl blends as a function of composition and processing conditions is studied. Effects of processing conditions such as screw speed and residence time, on the morphology and mechanical properties of PP/Noryl blends are investigated. The processing-morphology-property relationship in PP blends is discussed.
The Effect of Processing Variables on the Quality of Injection Molded Foamed Parts
The main objective of the work presented was to determine which operating variables of an injection foam molding process had a significant effect on the physical properties of the EVA foams produced. Statistical design of experiments techniques were used to first screen potential factors and then conduct experiments involving dominant factors to develop empirical response surface models for each of the responses. The models were then verified by testing their ability to predict the results of new experiments both inside and outside the model ranges.
Application of Fused Deposition Modelling in Spray Metal Tooling for Injection Moulding
This paper presents a modified spray metal tooling procedure based on FDM rapid prototyping process, where parting lines were defined in the design stage to simplify and accelerate the spray metal tooling. Core and cavity inserts for injection moulding of a gas turbine blade were created using the modified procedure and successfully injected using LDPE. The procedure significantly shortens and simplifies the tool fabrication process, particularly for complex shapes, when manual parting lines establishment is too complicated and time consuming.
The Effect of Crystallinity on Oxygen and Carbon Dioxide Gas Barrier Properties of PET
Gas barrier of cold crystallized poly(ethylene terephthalate) (PET) was studied as a function of crystallinity. Changes of permeability and solubility versus crystallinity showed complex behavior, which can not be understood in terms of traditional two-phase approach. The data, however, were amenable to interpretation by three-phase model where, in addition to regular amorphous and crystalline phase, the rigid" amorphous phase with density lower than the density of regular amorphous phase was considered."
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.
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