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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Estimating Fully Developed Melt Temperature in Extrusion
It is very useful to be able to predict melt temperature in extrusion, particularly in the extrusion of temperature sensitive polymers. Examples are extrusion of crosslinkable polymers, foamed polymers, and polymers that are susceptible to degradation. Unfortunately, the proper calculation of melt temperature is rather involved and requires the use of numerical techniques, the most popular one being finite element analysis. This paper describes a method to predict the fully developed melt temperature in screw extruders based on simple analytical expressions. The method is easy to use and leads to quantitative results with a minimum of time expenditure.
On-Line Product Quality Measurements for Continuous Sheet Processes
Continuous sheet processes include film/ sheet flat sheet extrusion lines, PVC Calendering lines, Blown film lines, and a variety of Coating processes. Manufacturers who own one or more of these processes, are interested in knowing the thickness or weight per area of the product that they are making and whether it is being made within specification. Knowing this while the product is made can lead to a reduction in the amount of out of tolerance material and scrap. There are several measurement technologies that can be used to provide this information while the product is being made. Several of these are introduced and discussed. The pros and cons of their application are presented along with a description of the technology.
Brownian Dynamics Simulation of Non-Dilute Fibre Suspension Flows in a Centre-Gated Disk
We present a Brownian dynamics simulation method for predicting the flow-induced fibre orientation of non-dilute suspensions in the filling of a centre-gated disk cavity. The evolution of fibres is modelled by the combination of the Jeffery equation and a stochastic process to describe the deviation of the fibre motion from Jeffery's orbits due to the interaction among fibres. The present method does not require any type of closure approximations and enables us to obtain accurate solutions for a wide range of volume fractions of fibres. Results showing the fibre orientation evolution along the radial distance and through the thickness are reported.
The Study of the Optimum Processing Temperatures for Styrene-Complex/Cu Substrates
This paper is to study the adhesion enhancement of styrene copolymer with copper by the addition of different ratios of Glycidyl Methacrylate. Styrene Glycidyl Methacrylate (S-GMA) is susceptible to be an adhesion promoter due to its reactive epoxy functional group. During the hot press stage, an appropriate heating profile can provide polymer molecules enough kinetic energy for a better mechanical processing property. However, a thermally stable working window is highly required to eliminate the induction of copper to copper oxide particles, which results in the degradation of electrical, chemical and mechanical properties. Thus, a well bonding between polymer and copper can be possibly manipulated by an suitable processing condition and the corresponding GMA ratios. An FTIR-Microscope accompanied by a micro heating stage was used to monitor the dynamic behavior of polymeric functional groups at different temperatures. A relation of Cu/S-GMA bonding strength associated with thermal effects was noticed. In addition, various levels of GMA concentrations were also considered to give contributions in enhancing bonding interactions. Peel strength experiments verified the prior FTIR observations.
New Dialkyl Peroxide for Improved Controlled Rheology Polypropylene Used in FDA Applications
The use of polypropylene for food contact applications such as specialty packaging films has increased dramatically over the last decade. Much of the polypropylene resin used in this industry has rheology characteristics imparted by a reaction extrusion process. The modification of low melt flow resins is accomplished by an extrusion reaction of the polymer with an organic peroxide. The decomposition of the organic peroxide yields a radical species which modifies the molecular weight profile of the resin. The decomposition of the organic peroxide is known to lead to the formation secondary products (organoleptics) such as alcohols and ketones, which can impart disagreeable odor and taste characteristics to the resin. The US Food and Drug Administration (FDA) regulates the allowable concentration of potentially hazardous materials in food grade applications. The formation of hazardous decomposition products can be eliminated by employing an organic peroxide that does not yield regulated decomposition products. This paper reports the use of a new dialkyl organic peroxide in controlled rheology processes. The new peroxide combines improved odor and taste characteristics with ease of processing and cost advantages.
Increasing PVC Suspension Polymerization Productivity Using Temperature Programmed Reactions
PVC polymerizations are known to be auto-accelerating. The reaction rate increases with conversion. Because of this phenomenon substantial reactor productivity at early conversion can be lost because the heat removal capacity of the reactor is not fully utilized until near the end of the polymerization. For this reason it is desirable to speed up the polymerization at the beginning and slow it down near the end. This rate adjustment can be achieved by running the polymerization hotter in the beginning and then cooling. We have written a scientifically based computer model of the polymerization designed specifically to simulate such temperature programmed reactions. The model does a complete heat balance on the polymerization, has a molecular weight predictor, and will be described and demonstrated for a polymerization at 50 degrees centigrade using Sec-Butyl Peroxydicarbonate (SBP) as initiator. Using this single initiator, and a very simple straight line temperature programmed reaction, the time to 80 % conversion can be reduced from 335 minutes to 240 minutes. This is a substantial increase in productivity.
The Strategic Research Partnership: A New Business Model for Effective Outsourcing of Business Research and Analysis
Several critical issues are facing plastic industry executives today. Global cost pressures are leading to a wave of mega-consolidations and spin-offs, resulting in dramatic changes in the competitive environment. Companies/combinations such as Dow-Union Carbide, the proposed Shell-BASF polyolefins merger, Clariant, Celanese AG, BP Amoco and Exxon-Mobil to name a few, would have been unimaginable a few years ago. We are also witnessing a significant power shift toward the customer. The industry is moving from a supply driven to a demand driven dynamic. This has sometimes been whimsically referred to as the “Walmartization” of the supply chain. The cost of losing a customer has never been higher. Companies who ignore their valuable customer assets do so at their peril. At the same time, new product development cycles are being com pressed as never before. For example, new product designs developed in Europe or North America are being cloned in the Far East in a matter of months. Globalization is also proceeding at a rapid pace. Increasingly global customers are demanding suppliers who are capable of supplying products to identical specifications anywhere in the world. Management must look beyond its borders at potential competitors worldwide; competitors w ho m ay not “play by the same rules”.
Class A Thermoplastic Automotive Part Production without Painting
Class A" automotive parts with a 1.6 square meter surface area were produced using a new process of surface finishing/compression molding SFC (The Valyi SFC™ Process (1). In the process a precut Class "A" film finish blank was placed over the mold cavity of a vertical press. Molten plastic was extruded onto the film reinforcing layers added and the mold was closed. In this SFC process the melt deposited directly onto the film backing layer heats the film finish and causes it to become pliable for forming. This process eliminates the need for painting and produces large parts at low clamp forces. This paper reports the materials and process which were used to produce full sized development parts that demonstrate the capability for production of large structural panels such as roof tops hoods or trunk lids."
Satisfying Medical Device Biocompatibility Requirements: What's a Supplier to Do?
Since the early 1990's, the medical device industry biocompatibility programs have been driven by the international standard (ISO) 10993. This series of standards is now approaching 20 subparts. Demands on the device manufacturer in time and money have become substantial. This can be softened by suppliers of raw material resins and component parts that address some of these testing requirements in advance. Attention to testing requirements by the supplier often prevents duplication by the device manufacturer, and can eliminate surprising results that appear when various companies conduct their own biological and chemical testing. Providing results to the manufacturer can take the form of test certificates, formal brochures with data, or a material master file at the FDA. Such additions to the suppliers offerings can improve marketing position and marketing efforts.
Evaluation of a Wood Fiber-Based Compound by Torque Rheometry
The trend toward increased usage of renewable resources has led to the growing popularity of wood-filled materials. These emerging materials require extensive testing - beginning with formulation and ending with the final manufactured product. In the early stages of development, it is possible to acquire data comparing differences between recipes utilizing a Mixer/Measuring Head. The given blend can be compounded with a customized twin screw extruder and torque rheometer. Finally, a single screw extruder can quantify the rheology of the compound using a capillary die. The objective of this work is to investigate the behavior of a polyolefin based wood-filled compound using a torque rheometer.
The Occurrence of Fiber Exposure in Gas Assist Injection Molded Nylon Composites
Gas assist injection molding has increasingly become an important process in industry because of its tremendous flexibility in the design and manufacture of plastic parts. However, there are some unsolved problems that confound the overall success of this technique. The purpose of this report was to study the surface roughness phenomenon occurring in gas assist injection molded thermoplastic composites. The materials used were 15 % and 35% glass-fiber filled Nylon-6 composites. Experiments were carried out on an 80- ton injection molding machine equipped with a high-pressure nitrogen-gas injection unit. Two float-shape" axisymmetric cavities were used. After molding the surface quality of molded parts was measured by a roughness meter. Various processing variables were studied in terms of their influence on formation of surface roughness: melt temperature mold temperature melt filling speed short-shot size gas pressure and gas injection delay time. Scanning electronic microscopy was also employed to characterize the composites. It was found that the surface roughness mainly results from the exposure of glass fiber in the matrix. The jetting and irregular flows of the polymer melt during the filling process might be factors causing the fiber exposure."
A Study of the Weldline Strength in Gas-Assist Injection Molded Thermoplastics
Gas assist injection molding has increasingly become an important process in industry because of its tremendous flexibility in the design and manufacture of plastic parts. However, there are some unsolved problems that confound the overall success of this technique. Weldlines form wherever polymer flow fronts meet is one of them. In this report, an L'18 experimental matrix design based on the Taguchi method was conducted to optimize the weldline strength of gas assist injection molded thermoplastics. Experiments were carried out on an 80-ton injection molding machine equipped with a high-pressure nitrogen-gas injection unit. A dumbbell-shape mold cavity was used. After molding, the weldline strength of the parts was measured by a tensile tester. For the factors selected in the main experiments, melt temperature and mold temperature were found to be the principal factors affecting the weldline property of gas assist injection molded thermoplastics. Weld strength decreases with the length of gas penetration. In addition the weldline strength of gas assist injection molded parts was found to be generally weaker than that of conventional injection molded parts. area near a gate. It has been observed that the presence of weldlines significantly reduces the strength of injection molded parts. Therefore, a number of remedies for controlling processing conditions have been investigated in order to enhance the strength of the weldline area of injection molded parts.
Rotational Molding of Polyethylene Foam by Pellets
Rotational molding of polyethylene foams has increasingly become an important process in industry because of its thicker walls, low sound transfer, high stiffness and good thermal insulation. This report is to assess the rotomoldability of multi-layer polyethylene foamed parts. The polymeric material used is high-density polyethylene and the foaming agent used is endothermal chemical blowing agent. Two different molding methods, by powder and by pellet, were used to mold the multi-layer- foamed parts. Rotational molding experiments were carried out in a laboratory scale uniaxial machine which is capable of measuring internal mold temperature in the cycle. Characterization of molded part properties has been performed after molding. The final goal of this study is to investigate how the blowing agent and processing conditions can influence the process of rotational molding and the final product quality. It was found that the rotational molding of two-layer polyethylene foams has the advantage of better impact properties as well as fine outside surfaces. In addition, rotational molding of foamed parts by pellets needs shorter cycle time, but is counteracted by uneven inner surfaces.
Weldability Diagram for the Ultrasonic Welding of Thermoplastics in Far-Field
Ultrasonic welding has proven itself to be an efficient way of joining thermoplastic parts. It is accomplished by applying high frequency, small amplitude vibrations to the pieces to be joined together. To make satisfactory products, the material, the horn, and the process parameters determine the weldability of a specific system. The concept of welding areas on the critical plane can be extended from injection molding to the ultrasonic welding system of thermoplastics. This research is devoted to the development of a proper weldability diagram for ultrasonic welding in far-field. The first part of this study is to identify the relative importance of process parameters. The results show that weld time and amplitude of vibration are the two factors which most significantly affect the ultrasonic welding process. The second part of this study defines the weldability based on critical parameters. The application of the weldability concept is demonstrated in selecting the optimum part and energy director geometry. In addition, the temperature variations at the joint interface were recorded to better understand the welding process. These weldability studies are intended to give first guidelines for system optimization.
Optimizing the Joint Strength of Ultrasonically Welded Thermoplastics in Near-Field
Ultrasonic welding of thermoplastics has become an important process in industry because of its relatively low cost and high quality joints. However, the optimization of this technique has been essentially based on a trial-and-error process. In this report, an L'18 experimental matrix design based on the Taguchi method was conducted to optimize the joint strength of ultrasonically welded thermoplastics. For the factors selected in the main experiments, weld time and amplitude of vibration were found to be the principal factors affecting the joint property of ultrasonically welded thermoplastics. A weldability diagram was proposed based on the statistical results to give first guidelines for system optimization. In addition, amorphous polymers required less energy to be successfully welded than semi-crystalline polymers. Semi-circular energy directors were found to bond parts of highest strengths.
Influence of Applied Pressure on Erucamide Diffusion in LLDPE Films
There are many factors that influence the diffusion of an additive to the surface of a polymer film. One of the factors that is not often studied is applied pressure, which is an important factor because the pressure exerted on film near the inside of a roll may be significantly different than the pressure exerted on the film near the outside of a roll. We have demonstrated previously that a higher applied pressure tends to hinder additive diffusion. This paper studies additive accumulation at film/film interfaces as a function of applied pressure. The results indicate that a decrease in additive at the surface coincides with an increase in applied pressure.
Developing a Surface Texture with Film Insert Molding (FIM)
The surface texture of an Injection molded part in the film insert molding process is affected by the Molding injection machine parameters. Other variables include the molded material, the film texture and thickness, the quality of the applique, and the mold finish. In this study three different films, using two thicknesses were processed. The injection speed and mold temperatures were varied. Three different resins were evaluated. A 102 mm x 152 mm (4 in x 6 in) part with six different textures was used to determine the gloss and roughness of the finished part with each set up. The goal was to determine the affects on the finish of the final part in the FIM process.
PEN-Poly(ether imide) Blends: Melt Rheology and Stress Relaxation in Semi-Crystalline Films
Past studies on the stress relaxation of biaxially oriented polyester films are extended to a blend of poly(ethylene-2,6-naphthalate) (PEN) and poly(ether imide) (PEI) at a composition of 85/15 by wt. At this composition the polymers are fully miscible and the melt viscosity and flow activation energy of the blend are dominated by the PEN component. PEI plays a more important role in controlling the sub-Tg stress relaxation response of films produced from the corresponding blend. We show that the relaxation time of a biaxially oriented, semi-crystalline film is increased upon addition of PEI to the PEN matrix, consistent with the rise in glass transition temperature. Also, using stress relaxation data in combination with the concept of aging acceleration factors, we probe the kinetics of the physical aging process for the neat PEN and blend films over a temperature range spanning from ca. Tg - 5O°C to Tg + 10°C. Over this temperature interval both films eshibit thermorheological simplicity with respect to time-aging time and time-aging temperature superposition and the rate of physical aging peaks at ca. Tg - 20°C. However, the relative increase in the rate of aging is much lower for the blend, thus suggesting that the PEI component is well dispersed in the PEN matrix and is effectively retarding the segmental mobility of PEN.
On-Line Analysis of Stress and Birefringence Development in Simultaneous Biaxial Elongation of Poly(ethylene terephthalate)
On-line measurements of elongational stress and birefringence of poly(ethylene terephthalate) film were performed under simultaneous equal-biaxial elongation at various strain rates and temperatures. The strain hardening started to occur at a true strain of about unity, which was practically independent of drawing condition. Even though the drawing was done under the equal-biaxial condition, the PET films started to show optical anisotropy in the film plane before the strain hardening. The optical anisotropy was more significant under the drawing conditions of high strain rate and low temperature, however it only appeared in the limited range of strain and disappeared again in all the samples when strain was high enough. The starting point of the optical anisotropy corresponds to the off-plane birefringence, which is defined as the refractive index difference in the directions parallel and normal to the film plane, of about 0.03. This birefringence also corresponds to the critical point above which the stress-optical law is not applicable because of the starting of spontaneous molecular orientation. A similar spontaneous orientation behavior was also observed in the uniaxial elongation process.
Low Extractable, Low Blush, Low Color PVC with Improved Processibility for Medical Application
The present paper provides an additive system for a PVC formulation to improve processing and functional characteristics. This additive system improves melt fabrication and heat stability of the PVC (e.g., increased thermal stability for faster melt flow during extrusion without discoloration or formation of black specks; eliminates further plate-out or build-up on the processing equipment; decreased scrap and equipment down-time; permits higher use of regrind) and the desired product charateristics (e.g., low color, high clarity, low-blush, extractables and particle generation).
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