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

Integrated Simulations of Gas Injection Molding Process and Part Structural Performance under a Unified CAE Model
Shia-Chung Chen, Shen Yan Hu, Yeon-Pun Chang, May 1999

Integrated simulations of gas injection molding process and part structural performance under a unified CAE model were carried out. An analysis algorithm based on DKT/VRT elements superimposed with beam elements representing gas channels of various section geometry was first developed to evaluate the structural reinforcement of gas channel in the design stage. During melt/gas filling process, a mixed control-volume/finite-element/finite-difference method combined with dual-filling-parameter technique was implemented to trace the advancements of melt and gas fronts. For the prediction of secondary gas penetration, flow model of isotropic-shrinkage origin was introduced. Mold cooling analysis was executed utilizing cycle-averaged boundary element method considering the cooling system. Both cooling channel and the hollowed core gas channel were modeled using line-source approach. Thermal residual stresses calculated from part temperature distribution were then combined with the structural analysis to predict part warpage. The monitor support was used as the case study. The analysis accuracy from this unified model of 2 1/2-D characteristics were examined experimentally. The only difference between process simulation and structure/warpage analyses is that different values of equivalent diameters assigned to a circular pipe representing gas channel should be used, respectively.

Waxs Modeling of the Liquid State of Polyethylenes: Implications for Phase Analysis, Glass Transition, and the WLF Constants in Thermoplastic Elastomers
Kenneth Monar, Anton Habenschuss, May 1999

Waxs studies of melts of branched copolymers with varying comonomer content revealed a temperature and branch dependence of the low angle amorphous halo (LAH). Numerous studies in real space suggested a semi-quantitative method for the deconvolution of the LAH. Two linear relations for the temperature dependence (low/high branch content) were observed. The WLF constant, C2, is derived from the slopes and the Tg° from the convergence temperature. The quantity fo of C2 is ca. 4.1x10-4/K. Proper representation of the liquid state scatter (and its temperature dependence) are crucial in quantitative phase analysis, including: interfacial content, latent heat, and crystal microstructure with increasing chain defects.

Elastomeric Polypropylenes from Unbridged Metallocenes
Charles Myers, Cynthia Allen, Andreas Ernst, Houssam Naim, May 1999

The present work describes properties of a series of experimental polypropylene polymers prepared with unbridged 2-arylindene group IV catalysts. Compositions span a broad range of isotactic content and have molecular weights typically used for extruded polypropylene films and fibers. Mechanical properties encompass elastomers with moderate recovery to highly ductile soft plastics. Compared to ethylene based copolymer elastomers with similar room temperature elastic modulus and tensile properties, these polypropylene elastomers have higher softening and melting temperatures but also higher glass transition temperature.

Traditional Xbar Charts for PET Preform and Bottle Manufacture Reduce the Effectiveness of the Industry's SPC Efforts - Issues and Solutions
Stephen W. Zagarola, May 1999

Traditional Xbar charts, the most popular statistical process control charts in the PET preform and bottle manufacturing industry, are often counterproductive. The typical application ignores the fact that each mold cavity of an injection or blow mold potentially behaves differently due to characteristics of that mold cavity. This paper discusses effective control charting techniques for dealing with blow molding and injection processes. The techniques offer more accurate estimation of when it is necessary to intervene in the process, quicker forecasting of impending defective production, and better visibility of what's going on in individual molds or mold cavities.

Value-Added Internal Audits
Merry Keating, May 1999

To get the most value from your internal audit process it must be carried out in a way so as to ensure its continued ability to determine the effectiveness of the overall quality system. The quality system will always undergo change. Even as it matures, change is inevitable as a result of continuous improvement, company growth, restructuring, etc. For that reason, the internal audit process must also be a living system - consistently updated and molded to perform as the tool needed to judge the quality system effectively. It will also then meet the intention of the ISO 9001/9002 requirement of audits... scheduled on the basis of status and importance..."."

In-Line Granulation - A Key to Reduced Edge Trim Recycle Costs
J.G.S. Billingsley, Lawrence D. Bush, May 1999

In-line granulation, the size reducing of plastic trim as it comes off an extruder, tenter, frame, slitter or other production machine has many advantages over conventional trim handling methods. Small granulator size is an inherent requirement because of the limited installation space around these production machines and sound pressure levels must be low because of the proximity of the granulator to the machine operator. Precision Cutters, Inc. (PCI), has developed a unique line of small, very efficient, high productivity in-line granulators that meet all size and operating requirements for use in this advanced, closed, one-step trim to granulate process. The engineering principles of film granulation and throughput rates in kgs/kw-hr (lbs/hp-hr) are covered.

SC Coupling System Enhances the Properties of Mica Filled Polypropylene and Mica/Glass Polypropylene Hybrid Systems
Joseph Antonacci, Ahsan Khan, Iqbal Sher, May 1999

High aspect ratio mica improves the modulus and heat deflection temperature properties of thermoplastic polymers and reduces the shrink and warping of plastic composites. Tensile and flexural strength properties are usually maintained while impact properties decrease. Glass reinforced polypropylene composites offer good strength, impact and heat deflection properties; however, dimensional stability and warping of molded parts have always been a problem resulting in over engineered parts at premium costs. This study involves the development of the SC" coupled mica system to improve the bonding between the mica reinforcement and polymer matrix so as to enhance the traditional properties provided by mica to reinforce polymers."

Pressure-Volume-Temperature Relations of Polypropylene + Polymer Liquid Crystal Blends
Antje Stein de Vilchez, Witold Brostow, Robert Maksimov, Marcela Naranjo Girardi, May 1999

Blends of polypropylene + polymer liquid crystal (PLC) were investigated by a pressure-volume-temperature (PVT) technique. The focus of the project was the determination of the characteristic parameters of the Hartmann equation of state, which are usable for the analytical representation of the time-temperature superposition principle. The necessary time-temperature shift factor can be calculated by the Williams-Landel-Ferry (WLF) equation. Since the WLF equation is limited in its temperature application, an equation was derived relating the time-temperature shift factor to the temperature via the reduced volume, which depends on the characteristic parameters of the Hartmann equation of state.

Thermoforming Behavior of Olefinic Instrument Panel Skins
Thomas C. Yu, May 1999

Currently thermoplastic olefins (TPO) are being used for injection molded or extruded automotive exterior parts. Due to lack of melt strength of the polypropylene base resin, the thermoformable TPO are still under development for automotive interior skins. The advantages of TPO skins over the current PVC/ABS skins are long term aging, reduced fogging, and improved recycling. Laboratory evaluation for formability usually involves uncommon and tedious tasks. In this study, dynamic mechanical analysis in tension mode was used to predict the optimum temperature range for thermoforming, extent of network enhancement, as well as other mechanical properties.

Fourier Transform Infrared Micro Spectroscopy Mapping Studies of Weathered PVC Capstock Type Formulations. II: Outdoor Weathering in Pennsylvania
Dana Garcia, Janine Black, May 1999

FT-IR micro spectroscopy coupled with mapping techniques is a powerful methodology to evaluate dimensionally dependent changes such as those encountered in PVC weathering processes. It is based on the complexity and specificity of the infrared spectrum and the dimensional resolution of the microscope. This presentation will outline a systematic FT-IR study of changes observed during outdoor photo degradation of PVC siding capstock formulations, as a function of exposure time and TiO2 level. The results will be compared with previously obtained accelerated QUV data. Profiles through the thickness dimension will be analyzed to identify degradation species and depth distribution.

Dispersion of Birefringence and its Influence on On-Line Measurement of Stresses in Polymer Films
A.S. Redner, J. Greener, B. Treadway, May 1999

Birefringence distribution in biaxially oriented polymer films is often used to assess non-uniformities in processing and in physical properties. Off-line characterization of this property can be performed by direct measurement of anisotropy in the refractive index, a process that is slow and not suitable for on-line use. By comparison, the spectral contents analysis (SCA) method is fast and easily adaptable for on-line process monitoring and real-time process control. However, implementation of this method requires accurate knowledge of the chromatic dispersion of birefringence. This paper discusses the contribution of birefringence dispersion to the precision of birefringence measurement by the SCA method, and it describes a new spectrometric procedure for accurate measurement of this material property.

The Effect of Shrinkage Induced Interface Gap on the Thermal Contact Resistance between the Mold and Plastic in Injection Molding
L. Sridhar, Wenyue Yin, K.A. Narh, May 1999

Accurate modeling of the heat transfer from the vitrifying plastic to the mold is essential to obtain accurate simulation of the injection molding process. The thermal contact resistance is one parameter that affects the heat transfer in injection molding and is difficult to measure from laboratory experiments. In injection molding the thermal contact resistance in the post filling stage is shown to depend on the gap formed between the part and the mold wall due to part shrinkage. It is shown from shrinkage calculations that the thermal contact resistance is a time and space (location on the part surface) dependent parameter and its value can vary by orders magnitude during each molding cycle. The effects of this variation on the molding process are discussed.

A Procedure for Determination of Thermal Properties of Polymers from Transient Temperature Data
L. Sridhar, Max Roman, K.A. Narh, May 1999

Thermal properties are important parameters in both process and product design. In the case of plastics, the need for quick and accurate determination of thermal properties is gaining importance due to large variety of blends and recycled materials that are becoming available. A procedure based on an inverse method is presented for the determination of thermal conductivity and specific heat. The method makes use of transient temperature measurements. The temperature measurements are made in reference metal blocks and no temperature sensors are inserted in the plastic specimen. The method shows potential for obtaining the thermal properties over a wide range of materials and temperatures, and as a function of pressure. The method has been tested in simulation and results are presented.

Improving Economic Efficiency - Key for Market Penetration of Continuous Carbon Fibre Reinforced Thermoplastics
A. Hartmann, C. Mayer, M. Neitzel, May 1999

Due to its outstanding properties continuous carbon fibre reinforced thermoplastic is ideal for many industrial applications. But, insufficient economic efficiency has been clearly identified to be the main obstacle for future penetration of the targeted markets. A significant potential for cost saving has been identified by process optimisation. Additional cost reduction is expected from the announced introduction of low cost carbon fibres. Cost analysis shows that the level of processing cost will fall significantly in the future. However, the investigation indicates that a cost level acceptable for mass markets like the automotive industry will not be achieved in general.

An Integrated Adaptive Control for Injection Molding
K.K. Wang, J. Zhou, Y. Sakurai, May 1999

The objective of the research project is to investigate the possibility and develop a methodology and associated system to control the quality of injection molded parts on-line and adaptively. The project makes use of rigorous process simulation programs first to determine the initial machine-setup condition and then to predict the part quality. Such simulation programs are incorporated in the feed-forward loop of a multi-level control architecture which also consists of three feedback loops involving the machine parameters, process variables, and part-quality levels, respectively. This paper describes the research plans and some results up to date.

Process Monitoring and Optimisation in Injection Moulding with the Aid of New Measuring Sensors
Elmar Moritzer, Michael Neumann, May 1999

With the aid of a newly developed, high-sensitivity measuring sensor system, it is possible to record the cavity pressure profile from outside the mould cavity, using the machine deformation as a directly correlating parameter. The measurement principle involves a pre-tensioned piezo element being coupled to the machine via a deformation cross-member. The system as a whole can be readily adapted, which means it can be retrofitted to existing injection moulding machines. The results of a study are presented, which looked into potential applications for this new generation of measuring sensors for process monitoring in injection moulding.

Optimization of Thermoforming with Process Modelling
R. DiRaddo, D. Laroche, A. Bendada, T. Ots, May 1999

The thermoforming process involves three stages, sheet reheat, forming and solidification. A polymeric sheet is heated in an oven to the desired forming temperature distribution. The sheet is then deformed to take the shape of the mould cavity and subsequently solidified. This work includes the modelling and experimental validation of both the sheet reheat and vacuum forming stages. The part considered is moulded in a box shape cavity mould that is supplied by Quality Thermoform. The modelling simulations and the corresponding experimental trials were performed at the Industrial Materials Institute. The heat transfer in the oven is modelled by employing combined radiation and natural convection. The sheet forming is modelled with a non-isothermal viscoelastic constitutive equation. The process stages are modelled in sequence, namely sheet reheat, sag and vacuum forming.

PP-EPDM Blends: Influence of Structure on Brittle-Ductile Transition
Reinoud J. Gaymans, Allard van der Wal, May 1999

The impact behavior of polypropylene and polypropylene-rubber blends have been studied as function of temperature with notched Izod and single edged notched tensile methods. Varied are the rubber concentration (0-40 wt %) and the rubber particle size (0.3-4µm). With increasing rubber content and decreasing particle size the impact behavior is improved. The ductile deformation is accompanied with a strong temperature increase of the deformation zone and even a melting in the fracture zone. The impact enhancement process seem to be first a cavitation of the rubber particles, followed a strong plastic deformation of the matrix material ahead of the notch/crack. The deformation seem to be enhanced by a thermal blunting of the notch/crack.

TPE Behavior of Segmented Copolymers with Crystallizable Esteramide Units of Uniform Length
Reinoud J. Gaymans, May 1999

Segmented polyesteramides are synthesized fitm N,N'bisaibomethoxybenzoy)diamine as crystalline segments and poly(tetramethylene oxide) as soft segments. As diamine is mainly taken tetramethylene diamine, but also studied are C6 - C12 diamines. The crystalline segments are uniform in length. The poly tetramethylene oxide segments ranged in molecular weight from 250 - 2900. Also used are tetramethylene oxides with amine endgroups. As extender is sometimes used pentadiol. The polymerization is carried out in the melt at 250°C for 1 hour while vacuum is applied. The melting behavior of the copolymers is studied by differential scanning calorimetry. The mechanical properties are investigated on injection molded bars using dynamic mechanical analysis. The melting temperatures decrease with PTMO length and the length of the diamine. The glass transition temperatures were, for the polytetramethylene oxides of molecular weight of 650 and higher, little affected by the composition. The modulus decreased with PTMO length and the segmented copolymers have very high elongation's at break.

Crystallization Behavior of Regioregular Poly(3-Dodecylthiophene)
S.L. Liu, T.S. Chung, May 1999

Non-isothermal and isothermal crystallization behavior of regioregular poly(3-dodecylthiophene) (P3DT) was investigated by differential scanning calorimetry (DSC) with an emphasis on the main chain crystallization. P3DT showed a sharp exothermic peak at 114°C which was attributed to the main chain crystallization and a broad one peaked at 59°C which was due to the side chain crystallization during cooling at 2.5°C/min from the melt. During heating, the side chains melted from 27 to 80°C, while the main chains exhibited up to three overlapped melting peaks. Avrami analysis for the non-isothermal crystallization revealed a sharp transition in the log(-ln(1-?)) vs. logt curves at the relative crystallinity of 63% for all cooling rates studied. The average Avrami exponent, n, was around 4.9 when the relative crystallinity was lower than 63%, while the n is around 1.5 when the relative crystallinity was higher than 63%. The non-isothermal crystallization activation energy was estimated to be 222kJ/mol by Kissinger method. Isothermal crystallization was also investigated at different temperatures. The formation of ordered structure and subsequent melting behavior were highly dependent on the crystallization temperatures and time. At lower crystallization temperatures, three melting peaks could be discerned. However, only one melting peak could be observed when the crystallization temperature was high.

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