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
The What, How and Why of Rotational Molding
Glenn L. Beall, May 2000
Rotational molding is a plastics molding process that is noted for producing seamless, hollow parts. The process is capable of molding complex, thin-walled, hollow parts in small and extremely large sizes. This paper will explain what the process is, how it works, and why the manufacturers of durable plastic products should be aware of this process's impressive capabilities.
Flexible Polyolefins and Low Density Polyethylene Blends for Film Extrusion Applications
Magda M. Castillo, Steve J. Grossman, May 2000
Polyethylene/i-PP(isotactic/crystalline) blends have been studied for years. However, these blends indicate a phase separation that detracts from compatibility and alters properties. It is expected that a combination of a novel less-crystalline polypropylene (FPO) with LDPE will allow for greater compatibility over a wide composition range. The LDPE/FPO blends appear semicompatible. Specifically, film extrusion processability increases, blocking decreases, along with better film appearance, and improvements in tensile strength without a decrease in flexibility. Alternatively, toughness, elongation and impact resistance increase. These enhanced properties may lend the blends to potential packaging applications.
Foamed Polymer Sandwich Composites Reinforced with Three-Dimensional Filler
Y. Yuan, F. Shutov, May 2000
Open-pore flexible polyurethane (PUR) foam with various pore sizes (1 - 8 mm) was used as filler to reinforce low-density closed-cell PUR flexible foam. The final composite has a sandwich structure, where the core zone has foam-in-foam" structure and skin zones are unreinforced PUR foams. Compared to the regular non-sandwich one-layer PUR flexible foam the sandwich composite exhibits improved mechanical properties: the support factor can be increased up to 65 percent and the compressive force deflection value can be increased almost 100 percent while the density of the composite increases only 25 percent."
ANSI Standards Combined with European Hazard Ranking Methods Provide Plastic Web Processors with Powerful Tools for Enhancing Workplace Safety
Donn C. Lounsbury, May 2000
A set of four safety standards for film, sheet, coating & laminating, and plastic web winding machinery has been developed under the sponsorship of SPI, and accepted as consensus standards by ANSI. The author reviews some of the more significant requirements of these standards. The standards represent an excellent tool against which to audit existing processing lines to identify hazards to personnel. The European Community has evolved a standard (EN 1050)*1 methodology for identifying and ranking the hazards in processing plants. This methodology is outlined in detail. By utilizing both of these approaches in tandem, hazards can be identified by the auditing against the appropriate ANSI standards, the identified hazards ranked for probable degree of harm to personnel, then safeguarding actions prioritized to obtain the most benefit from the minimum effort.
Continuous Polymerization of Polycaprolactone in a Modular Co-Rotating Twin Screw Extruder
Byong Jun Kim, James L. White, May 2000
Bulk polymerization of e-caprolactone (CL) has been carried out in a modular intermeshing co-rotating twin screw extruder using aluminum isopropoxide as a coordination-insertion" initiator under a range of processing condition including temperature profiles throughput and screw speed. This homo-polymerization was investigated for various ratios of monomer to initiator. GPC analysis demonstrated that significant quantities of oligomers were produced together with high molecular weight polymer under different reaction temperatures. For continuous polymerization at 130°C using a modular co-rotating twin screw extruder high molecular weight up to 200000 were produced without substantial oligomers by increasing the ratio of monomer to initiator."
Fracture and Fatigue Properties of Injection-Molded Short Glass Fiber-Reinforced Poly(cyclohexylene-dimethylene-terephthalates)s (PCT) as a Function of Molding Conditions
J. Karger-Kocsis, T.J. Pecorini, May 2000
Summary The static fracture toughness (Kc) and fatigue crack propagation (FCP) behavior of injection-molded short glass fiber (GF) reinforced poly(cyclohexylene-dimethylene- terephthalate) (PCT) composites were determined as a function of material parameters (with and without flame retardant) and molding conditions (injection speed and plaque thickness were varied). The anisotropy in the fracture mechanical response of GF-PCT, determined on compact tension (CT) specimens notched along and transverse to the mold filling direction (L- and T-notching, respectively) was interpreted by considering the molding-induced microstructure (GF layering and alignment). It was established that the effect of injection molding speed is negligible at the same specimen thickness. By contrast, increasing thickness strongly affected the GF structuring and thus the related fracture mechanical response.
Nylon and Moisture: The Real Story behind the Effects of Drying Resin and Conditioning Molded Parts on Final Properties
Michael P. Sepe, May 2000
The influence of absorbed moisture on the performance of nylon products is well documented. Similarly, the effects of excess moisture on the processing of nylon are well established. But confusion often arises in the processing community regarding the reasons for the brittle behavior of nylon parts. This paper is designed to follow the role of moisture from the pellet through to the conditioned part and separate the fact from the fiction regarding the effects of moisture on nylon properties.
Effects of Aspect Ratio on Performance Properties of Mica Reinforced Polypropylene and Nylon
Levy A. Canova, May 2000
This paper reviews a study designed to determine the effect of aspect ratio on properties of mica reinforced polypropylene and nylon composites. The study was made possible by recent developments in particle analysis software that permits determination of aspect ratio of non-spherical materials.
Virtual Instruments for Polymer Characterization and Processing
Ian R. Harrison, May 2000
It's expensive in terms of time and equipment to give students the necessary exposure to a wide variety of polymer behavior in different areas of characterization and processing. 'Virtual instruments' (VIs) consist of interactive software that simulates the response of a particular characterization instrument or a process. A characterization 'suite' contains many thermal instruments; other instruments are under development. A blown film process line has also been assembled relating film properties to operational parameters.
Predicting How the Cooling and Resulting Shrinkage of Plastics Affect the Shape and Straightness of Extruded Profiles
Randy J. Brown, May 2000
During the extrusion of complex plastic profiles, the parts often distort and bow during the cooling phase of the process. The traditional methods of dealing with this are to use heat lamps to re-warm certain sections to remove the bow or to apply jigs to distort the part in the opposite direction so that when it cools, it comes back into the proper shape. A method to look at the cooling requirements of a particular profile is proposed along with a method to calculate how the part should be cooled in order to avoid distortion and bow.
Toughening of Epoxy Resins by Partially Decomposed Polyurethane Waste
J. Karger-Kocsis, J. Gremmels, May 2000
Hygrothermally decomposed polyurethane (HD-PUR) of polyester type has been used as a cost-efficient impact modifier in tri- and tetrafunctional epoxy (EP) resins. The PUR modifier was added between 5 and 80 wt.% to the EP prior its crosslinking with a diamine compound (Diaminodiphenylsulphone, DDS). The fracture toughness (Kc) and -energy (Gc) of the modified resins were determined on static loaded compact tension (CT) specimens at ambient temperature. The mean molecular weight between crosslinks (Mc) was determined from the rubbery plateau modulus of dynamic mechanical thermal analysis (DMTA) spectra. The change in the Kc and Gc as a function of Mc followed the prediction of the rubber elasticity theory. The efficiency of the PUR modifier was compared with that of a carbonyl terminated liquid nitrile rubber (CTBN). DMTA and fractographic inspection revealed that the PUR modifier was not only present in a dispersed phase of the EP matrix but participated in the build-up of the EP crosslinked network structure. Thus HD-PUR works as active diluent and phase separating additive at the same time. As HD-PUR can be regarded as an amine-functionalized rubber, it was used as hardener alone (by replacing DDS) in some EP formulations.
Thermoplastic Elastomers of Poly(ethylene terephthalate) and Grafted Rubber Blends
N. Papke, J. Karger-Kocsis, May 2000
Thermoplastic elastomers containing 50 wt.% poly(ethylene terephthalate) (PET) and 50 wt.% rubber with and without glycidyl methacrylate (GMA) functionalization were produced by melt blending. In some cases the method of dynamic curing was also adopted. The static tensile properties and dynamic-mechanical thermal analysis (DMTA) response of the systems were studied. The phase morphology of the blends was of interpenetrating network (IPN) type according to fractographic and DMTA results. It was established that the best mechanical performance exhibited those blends which contained a GMA-grafted nitrile rubber (NBR-g-GMA). The effect of dynamic dynamic curing, for which a two-step procedure was developed, was marginal. Cost reduction opportunities of the recipes by using high-volume polyolefins have also been explored.
Structure/Process/Part Quality Relationship for BMC Injection Molding
Stéphane Menio, Eric Lafranche, José Pabiot, Claude Ollive, May 2000
Thanks to its qualities and performances, BMC injection molding has nowadays reached a satisfactory maturity level. But nevertheless, this technology remains complex. Thus, the aim of the present study is to determine the technological parameters capable of improving the surface quality of the molded parts. The experiments are performed with a semi-industrial mold for rectangular plate. A first Taguchi Design Of Experiments was used in order to quantify the effect of the feeding, filling, holding and curing parameters on the surface quality. It was completed by a second hybrid DOE, the aim of which was to estimate more precisely the incidence of the main key factors (mold surface temperature, injection flow rate and holding pressure) previously identified. These results have been then confirmed with a different gate location and a modified geometry.
Optimization of Cooling Systems in Injection Molds by an Easily Applicable Analytical Model
Natti S. Rao, Guenter Schumacher, Nick R. Schott, Keith T. O’Brien, May 2000
The production rate of injection-molded articles is determined by the cooling time of the polymer melt in the mold. By using state-of-the-art numerical software the mold design can be optimized in order to achieve fast cooling. However, the efforts required to apply this software do not always justify its use in dealing with the daily design problems. Taking the changing mold wall temperature into account a straightforward analytical procedure for optimizing the cooling channel lay-out for a thermoplastic resin has been developed. The equations in the model can be easily solved by means of a hand-held calculator, thus enabling quick estimates of the effect of relevant parameters on mold design. Results of numerous simulations and a worked-out example illustrate the application of the model which has led to good results in the practice.
Thermorheological Investigation of Entangled Branch Polybutadienes Having Different Architectures and Arm Lengths
M.T. Islam, J. Juliani, L.A. Archer, May 2000
Rheological behavior of entangled six-arm and eight-arm 1,4-polybutadiene melts of the types A3-A-A3 and A3-A- A2-A-A3 is investigated using low amplitude oscillatory shear and viscosity measurements. Experiments covered a time (frequency) and temperature range broad enough to characterize the complete relaxation spectrum. In oscillatory shear, three separate relaxation modes are identified. At high frequencies a maximum in the loss modulus is linked with segmental relaxation. At intermediate frequencies a new relaxation mode characteristic of the arms is observed. Finally, at low frequencies a terminal relaxation process is identified. This process is characterized by a lower plateau" modulus and is thought to reflect cross-bar reptation in an enlarged tube."
Clear and High Heat Resistant TPEs
Y. Martin Lu, Joe Kutka, May 2000
There is a market need for soft (35 - 70 Shore A) clear TPEs with heat resistance high enough for repeated boilable applications. Flexible PVC meets most of the requirements, but it is out of the scope of this work. Styrenic Block Copolymer based compounds have been developed to fill this need. Important parameters, such as molecular weight of the base polymer, surface quality of the molded part and rheology of the material, have been correlated with clarity and heat resistance. Some of the myths about the clarity of SBC compounds will also be discussed.
The Impossible Part-On the Verge of Failure?
Jerry Golmanavich, Barry Hofmaster, May 2000
There have been several occasions in the past where part designs have been proposed which require non-traditional approaches to manufacturing. Even with run-of-the-mill designs it seems prudent to do computer flow simulations to verify that a part is manufacturable. The case history described below details how a product was deemed impossible"; the flow simulation verified that it was "impossible" and yet the project was pursued and has now passed the prototyping stage. This paper describes a project where some risk was taken and may provide the drive to explore new limits."
Prediction of Degradation of Polyethylene during Rotational Molding
M.C. Cramez, M.J. Oliveira, R.J. Crawford, May 2000
During rotational molding the plastic is subjected to relatively high temperatures for long periods of time. This often causes degradation of the polymer at the inner surface of the molded article. The resulting degraded layer is responsible for the deterioration of the mechanical properties of the part. In practice, the optimum processing temperature and/or heating time must be obtained by means of an extensive molding and testing program. Moreover, as the degradability of polyethylene depends on many factors, such as the molecular structure of the material, the type and concentration of stabilizers and the thermal history experienced during processing, an optimization program that takes into account all these variables is very expensive and time consuming. In this work the degradation of polyethylene is studied using a technique widely used in the assessment of degradation resistance in the pipe industry - Oxygen Induction Time (OIT). The method enables the onset temperature of degradation to be identified using only a few milligrams of material. The data obtained from simple and quick experiments was used to produce an empirical model to predict the optimum inner air temperature for rotational molding of the materials. It is shown that whilst the maximum internal air temperature experienced during rotational molding is a good quality control parameter, there are many other important factors, such as the heating rate of the mold, the thickness of the mold material, etc.
Mixing Characteristics and Mechanical Properties of Polypropylene-Clay Composites
Kyu-Nam Kim, Hyung-Su Kim, Jae-Wook Lee, May 2000
Polypropylene(PP)-clay composites were prepared by melt mixing in an intensive mixer. Three grades of PP's having different melt viscosities were employed to investigate the mixing characteristics of the composites with various clays which belong to organically modified montmorillonite(org-MMT). Depending on the matrix viscosity and nature of the organic layer in MMT, significant variations in the phase structure of the composites were found. In addition to the simple combination of PP and clay, modified PP's having various content of maleic anhydride were also incorporated. Major interest was focused on the effect of varying thermodynamic affinity between the components on the phase evolution and mechanical properties of the composites. Requirements for the effective dispersion of clay in the PP matrix are discussed in terms of both rheological effect and thermodynamic interaction.
Orientation Measurements Online
Abdellah Ajj, May 2000
Orientation of polymers enhances many of their properties, particularly mechanical, impact, barrier and optical etc.. Orientation processes all involve extrusion prior to deformation and can generally be classified into three categories: fibers, films, and parts (sheets, bottles, rods, ...). The knowledge of the polymer orientation produced by the different processes is critical for establishing the process conditions and the final properties of the oriented polymer. There is a long history of investigations of orientation in polymers, mainly from off-line measurements, involving techniques such as birefringence, infrared spectroscopy, X-ray scattering, Raman, NMR, fluorescence, ultrasonic etc. In this presentation, we will focus on techniques which are or could be used for on-line monitoring of orientation processes. These include birefringence, spectroscopy, fluorescence and ultrasonic.
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