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

Modeling Flow-Induced Crystallization in Film Blowing
Antonios K. Doufas, Anthony J. McHugh, May 2000

A mathematical model was developed for the simulation of film blowing including the effects of flow-induced crystallization, viscoelasticity, and film cooling. The microstructural model is based on the formulation of Doufas et al. Our model predicts the location of the freezeline naturally as a result of crystallization and the stresses at the frost line, which are closely related to the mechanical and physical film properties. Depending on the processing conditions, our model predicts uniaxial or biaxial film stretching.

Bubble Growth in a Solvent-Polymer Solution
Vivek Pai, Moshe Favelukis, May 2000

A model for the growth of a non-ideal gas spherical bubble in a quiescent viscous liquid is presented. The growth of the bubble in the solvent-polymer solution is assumed to be controlled by momentum, heat, and mass transfer. Using the integral method, the differential transport equations were transformed into ordinary differential equations, which were numerically solved. The numerical results show that the pressure inside the bubble can increase to extremely high values before it decreases to a value close to the ambient pressure. It was also found that at low solvent concentrations heat transfer is not important, and the usual isothermal assumption can be applied. The relevance of this work to the process of polymer melt devolatilization is discussed.

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."

Process Monitoring Using UV-VIS Spectroscopy
J.C.J. Bart, May 2000

The paper describes process monitoring applications by spectroscopic methods for polymer/additive analysis, polymer melt analysis, additive quantitation, QA/QC purposes, on-line compositional polymer analysis, in-situ reaction monitoring (cure kinetics, polymerisation, color designation, molecular interactions, monitoring of extrusion processes, real-time measurements and use of fiber optics. In particular, the current status of on-line multicomponent additive analysis in the polymer melt by means of UV-VIS spectroscopy will be illustrated.

Effects of Processing Conditions on Extruded Polystyrene Sheet Feedstock Quality
Kolapo P. Adewale, Robert Roberts, May 2000

This work investigates the influence of various extrusion parameters on the physical properties of rubber modified polystyrene sheets. The extrusion parameters under consideration are melt temperature, chill-roll temperature, line speed and sheet thickness. Optimum extrusion conditions for producing polystyrene sheet feedstock are discussed.

Design for Rotational Molding
Jordan I. Rotheiser, May 2000

This paper will cover the details of piece part design particular to the rotational molding process. Ribs, bosses, wall thicknesses, parallel walls, internal and external corners, openings, draft angles and undercuts will be discussed. Joining features, such as inserts, hinges and molded-in threads, will also be reviewed.

Designing for the Process? (Design Details to Avoid)
Kenneth Bather, May 2000

At first glance the Rotomold process is a fairly simple one. Its capabilities are exiting and have opened new avenues for creative industrial designs including complex shapes and rugged structural parts. Successful Rotomolded designs can be obtained by keeping a few guidelines in mind from concept through to product generation. This portion of the program will cover the areas that need to be considered during the design process. Items to be highlighted are basic design guidelines, features that can compromise, complicate and delay a project and what to ask a molder about specific designs.

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.

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.

Aesthetics, Industrial Designers, and Designing for Rotational Molding
Gene Bothun, May 2000

Roto-mold is a versatile process which accomplishes many objectives which are difficult or impossible in other processes. It also has some special problems which complicate the aesthetic aspects of a design. Industrial designers working with engineers are uniquely qualified to design for this process.

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.

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.

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."

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