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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Clear, Radiation Sterilizable, Autoclavable Blends Based on Metallocene Catalyzed Propylene Homopolymer
In a previous paper the formulation and characterization of clear, radiation sterilizable, autoclavable blends of Ziegler-Natta catalyzed propylene homopolymers and metallocene catalyzed plastomers was described. These studies have been extended to blends in which the propylene-based component is also produced by a metallocene catalyst. We have found that higher plastomer content is required in blends with metallocene catalyzed polypropylene than with Ziegler-Natta produced material to provide comparable radiation resistance. Despite the higher plastomer content, the blends with metallocene polypropylene are similar in stiffness and resistance to softening at elevated temperature, yet clearer than the Ziegler-Natta polypropylene based compositions.
Commercial Epoxy + Monomer Liquid Crystal Epoxy Blends: Compatability and Curing Kinetics
Epoxy resins are known to have numerous applications. To improve their performance of the epoxy, we are applying molecular reinforcement by using polymer liquid crystals (PLCs). PLCs are well known for their excellent dimensional stability, good mechanical properties, high temperature usability, and outstanding environmental resistance. A novel retention class of LC thermosets can be obtained by endcapping mesogenic rigid rod molecules with reactive glycidyl groups. These thermosets potentially combine the performance of an epoxy resin with the excellent properties of LC. We have studied the simultaneous cure of the monomer liquid crystalline epoxy (diglycidyl ether of 4,4'-dihydroxybiphenol) with an anhydride cured diglycidyl ether of bisphenol F (DGEBP-F) epoxy. As a first step to determine optimum conditions for network formation, we report on the curing kinetics of molecular reinforcement of epoxy with a monomer liquid crystalline epoxy (MLC). The study was done by Differential Scanning Calorimetry (DSC) using autocatalytic expressions. Dynamic Mechanical Analysis (DMA) is used to verify compatibility of the blended systems by investigating the glass transition temperature as a function of %composition.
ESCR Behavior of Plastic Materials in Medical Environments
Besides other facets of product development, it is imperative for medical device manufacturers to take great efforts through proper evaluation and consideration of material properties under practical conditions to prevent product failure at the end-uses. The environmental stress crack (ESCR) induced by chemical agents plays a significant role on material performances. In this contribution, in-depth studies have been carried out on different medical plastic materials, such as polycarbonate, copolyesters, ABS, acrylics, rigid thermoplastic polyurethane and their blends. More attention will be focused on a copolyester material for its unique ESCR behavior. Variation of chemical agents (such as different types of hospital disinfection solutions) have great impacts on physical and functional properties. Various plastics shows distinct environmental stress cracking phenomena under different conditions. Mechanisms of ESCR phenomenon under different environments have been explored. Fibril reinforcement by cold crystallization and chain session by hydrolysis of the copolyester may have contributed to its excellent chemical resistance against a wide range of chemicals and its catastrophic failure in acidic or basic environment. In addition, appropriate definition of product failures is also critical in making materials decisions.
Doing Business in the Former Soviet-Block Countries
With the demise of the Soviet Block, the countries of Central and Eastern Europe have started to built their own market economies and are eager to do business with Western democracies. The long duration of the monolithic political, military and economic block devastated the cultural, moral and economical fiber of the satellite countries, some of which had more or less democratic traditions in the pre-World War II time. Yet, the people have a remarkable resilience and a strong desire to become a part of the free world. This contribution deals with the historic background and current developments, shows how these are related and presents some recommendations which may be useful for those interested in doing business in this region. In the last nine years or so the region of Eastern and Central Europe has undergone the most momentous changes imaginable. The monolithic Soviet block fell apart, Germany has been reunited, and the Soviet Union, Yugoslavia and Czechoslovakia have ceased to exist. The newly formed independent countries established governments by democratic elections. The challenges for these new governments are formidable; namely, to dismantle the rigid administrative and planning system typical for the communist system and to replace it with a political democracy and a market-based economy. Additionally, they are striving to develop greater contact with the rest of the world. The development of political democracy and individual freedom brought many economic improvements for the people. The supply of goods and services has improved immensely as new opportunities have emerged for everyone to amass wealth through their initiative, hard work and response to market demands. On the other hand, these changes appear to bring about some far less beneficial aspects: joblessness, economic insecurity, fear for the future and despair. The social and industrial infrastructure in many countries has all but collapsed, crime has increased immensely, social tensions have es
A Simple Method for near Quantitative Measurement of Polymer Blend Composition and Mixing Uniformity
Mixing is an important unit operation in the formulation, and fabrication of polymers, and a knowledge of both the dispersive and distributive components are necessary to adequately characterize a specific mixing process. Dispersive mixing, a measure of structural fineness, is important for rubber toughened and filled systems. Distributive mixing, a measure of homogeneity, is important for thermoplastic blends and reactive processing. Described herein is a rapid near quantitative technique to characterize blend compositional uniformity by using selective pyrolysis of PMMA containing model systems.
Freshman Design in Plastics Engineering
Although plastics product design is typically a senior-level course, the design process provided freshmen an opportunity to assess the jobs available to plastics engineers. Consequently, the plastics engineering freshman were given the assignment of designing new promotional items for the Department. Students examined plastics manufacturing processes, introduced to basic design concepts and followed the design process while they learned a computer-aided design software. Finally, design groups selected materials and a manufacturing process, calculated part specifications, produced part drawings, performed filling simulations using commercial flow analysis software. The designs were formally presented at the end of the semester.
Orientation Texture from Polymeric Materials Using Scattering Methods
Orientation is an important determinant of the end-use properties of many products made from polymers. Scattering methods using x-rays and neutrons provide direct means of assessing such orientation texture. Oriented microstructural features possessing distance scales on the order of 10 nm to 1000 nm manifest themselves through anisotropic small-angle scattering (SAS). Oriented semicrystalline polymers exhibit anisotropic scattering in the wide-angle diffraction (WAD) range. This presentation provides an overview of the theoretical and experimental basis for measuring and interpreting these effects. Data on oriented lamellar microstructures are used to demonstrate the challenges that arise in this area.
The Effects of Steady Shear on the Order and Orientation of a Diblock Copolymer Melt Using In-Situ Small-Angle Scattering
To understand the effects of processing on polymer melts requires experimental techniques that show the orientation of materials during processing. Small-angle neutron scattering (SANS) has been recently adapted to allow for examination of polymeric materials during shear. This work will highlight the benefits of combining shear and scattering techniques to study morphology, ordering and orientation of a polystyrene-polybutadiene diblock copolymer melt under steady shear flow. The order-disorder transition temperature (TODT) is unchanged at low shear rates but increases by DTODT ?TODT = ?1.35 at high shear rates. An analysis of the degree of orientation using order parameter calculations shows that maximum ordering occurs within 30 minutes of shear and better alignment is obtained at low shear rates. A large relative increase in the order parameter (up to 600 %) is seen upon cessation of the shear flow.
Flat System and Non-Turbulent Flow Pin Point Tip - New Concepts
The Flat gating system evolved from a controlled study of gate size optimization when applying Hot Runner pinpoint gating techniques. A major objective of the study was to maximize gate cosmetics when applying these gating techniques to a variety of plastic resins, each with their own distinct characteristics. The size of the gate was determined by the type of plastic resin used. A flat diameter was established at the downstream end of a pinpoint gating tip. The size of the flat was determined by the volume of resin required to fill the part. The results of the study produced a technique that allows for the calculation of specific gate sizes. The technique can be used to achieve a minimal gate vestige while maintaining optimum flow performance. The Flat System technique is independent from tip design geometry, and can be used with most resins (filled or unfilled) without regard for material viscosity. A second study was initiated to determine the direct wear characteristics (shear effect) of pinpoint tips when processing plastic resins with abrasive fillers. In recent years, the industry has used harder steel alloys (carbide) for tip construction in an effort to com rather than trying to resist it. This allows for tips made of softer steel alloys with increased life expectancy. Applying these new concepts to pinpoint tip construction results in improved molded part quality, improved gate cosmetics and reduced tip maintenance requirements.bat tip erosion (wear). The second study resulted in a new Non-Turbulent" design that maintains laminar flow along the pinpoint tip. The new design minimizes shear that is produced by "turbulence
Flat System and Non-Turbulent Flow Pin Point Tip - New Concepts
The Flat gating system evolved from a controlled study of gate size optimization when applying Hot Runner pinpoint gating techniques. A major objective of the study was to maximize gate cosmetics when applying these gating techniques to a variety of plastic resins, each with their own distinct characteristics. The size of the gate was determined by the type of plastic resin used. A flat diameter was established at the downstream end of a pinpoint gating tip. The size of the flat was determined by the volume of resin required to fill the part. The results of the study produced a technique that allows for the calculation of specific gate sizes. The technique can be used to achieve a minimal gate vestige while maintaining optimum flow performance. The Flat System technique is independent from tip design geometry, and can be used with most resins (filled or unfilled) without regard for material viscosity. A second study was initiated to determine the direct wear characteristics (shear effect) of pinpoint tips when processing plastic resins with abrasive fillers. In recent years, the industry has used harder steel alloys (carbide) for tip construction in an effort to combat tip erosion (wear). The second study resulted in a new Non-Turbulent" design that maintains laminar flow along the pinpoint tip. The new design minimizes shear that is produced by "turbulence rather than trying to resist it. This allows for tips made of softer steel alloys with increased life expectancy. Applying these new concepts to pinpoint tip construction results in improved molded part quality, improved gate cosmetics and reduced tip maintenance requirements.
Rigid PVC Formulation Optimization Using Sequential Simplex
A rigid PVC formulation was optimized for processing window and cost using sequential simplex techniques in combination with desirability functions. This optimization was performed on seven of the ten ingredients from a 'standard' siding compound with a relatively limited number of experiments. The processing window contour mapping technique was used to evaluate the effects of formulation changes. This was combined with the formulation cost using desirability functions to give an overall response for the simplex to optimize. The basic mechanics of sequential simplex and desirability functions will be described along with the results of the optimization.
Weld Strength Behavior of Laser Butt Welds
In terms of the process sequence, laser butt welding corresponds to contactless heated tool welding. The difference lies in the heating phase in which the joining zones of the semi-finished products are periodically scanned by an Nd:YAG-laser beam at a high speed (Fig. 1). Tests carried out with laser butt welds with a meltpool, in which the joining zone is plasticised more deeply in the middle than in the outer areas, have shown parameter-independent high weld strengths over a wide range of heating time and joining displacement. Welds without a meltpool, however, showed short-time welding factors of 1. The reason for this strength behavior in contrast to heated tool and radiant heater welding must be seen in the temperature distribution in the joining zone. Different cooling processes as well as the state of internal stresses may provide an explanation for this.
Part and Mold Design Targeted to Optimized Production
CAE applied to injection molding is a relatively well known technology, which dates back to the early 80's. Its use in simultaneous engineering design is, in principle, recognized as one of the key factors for optimizing the quality of new products with the highly sought after goal of reducing the time-to-market. In spite of its potential, the use of this technology is far from being widely accepted in all cases where it can prove advantageous. The paper identifies the problems at the root of this situation and focuses on the likely evolution of the mold making industry, with particular attention to the make-or-buy decision regarding the engineering of part design prior to mold construction.
Rheology of Metallocene-Catalyzed Polyethylenes - The Effects of Branching
The shear and extensional rheology of three polyethylenes(PE's) synthesized using metallocene catalysts are compared. One of the PE's is linear i.e. no long-chain branches (LCB), while the other two have different amounts of long chain branching. The shear viscosity of the linear PE is reflective of the narrow molecular weight distribution of metallocene catalyzed PE's while the apparently branched PE's exhibit a higher viscosity and an earlier onset of shear thinning. The linear polymer exhibited lower activation energy than the branched PE with similar MW. The linear PE does not show stress-strain hyesteresis while the branched polymer does. All of them show supercooling behavior.
Evaluation of the Curing Process in a Reinforced Epoxy by Dynamic DSC (TMDSC) and DMA
The curing process of an epoxy-fiber composite prepreg is a multistep process involving polymerization, gelation, crosslinking, and vitrification. Optimization of industrial processing requires knowledge of how each step is affected by time and temperature. This is usually facilitated by construction of a time-temperaturetransformation (TTT) diagram.1,2,3 Since the overall epoxy conversion reaction is exothermic, the rate and degree of conversion can be studied isothermally using differential scanning calorimetry (DSC), by comparing the change in enthalpy with the total change in enthalpy of the reaction4. An alternative method for determining the degree of conversion is by measuring the shift in Tg between Tg0 and Tg?, which will be proportional to the degree of conversion.3 The Tg can be measured by a variety of techniques, the most common being DSC, dynamic mechanical analysis (DMA) and thermomechanical analysis (TMA).5 Although DSC can detect both exothermic change and Tg, the two events are displayed on one signal and the two events are often found to overlap, making both signals difficult to quantify. Dynamic DSC allows the separation of reversing, in-phase events like glass transitions, from non-reversing, out-of-phase events like curing and enthalpic relaxations.6-12 However, both enthalpic change and Tg shift are unable to detect the gelation point, since it is not a rate effect. They can detect vitrification, since a drop in the rate of conversion occurs at this point. Gelation, being a molecular weight effect, is only seen in viscosity or chain mobility studies. The two most common techniques for determination of the gelation point are DMA (or rheology) and dielectric analysis (DEA). There are a variety of DMA techniques available for measuring the modulus and viscosity of epoxies, the most common being torsional braid analysis (TBA), parallel plate (or cone and plate), and three point bending. Several methods, most commonly DSC and DMA, can detect vitrif
The Effect of Polypropylene Type and Filler on the Properties of TPO Blends
The effects of polypropylene type, impact modifier type and level, talc filler, and injection speed on the properties of TPO blends were examined. Polypropylene impact copolymers drastically reduced stiffness while increasing impact strength. Talc significantly increased stiffness, but decreased impact strength. Higher molecular weight polypropylene homopolymer produced smaller decreases in tensile modulus, elongation, and impact strength. Increasing the amount of impact modifier slightly increased moduli, but decreased impact strength. The impact modifier type only influenced impact strength. Injection speed had no significant effects on the bulk properties of the blends.
Advances in Thermoplastic Encapsulation of Electrical/Electronic Components
For encapsulating solenoids, sensors, motor components and most recently integrated circuit (IC) modules, manufacturers are increasingly choosing engineering thermoplastics and injection molding technology over traditional thermoset resins and processing methods. After reviewing the cost and performance advantages of thermoplastic encapsulation technology, this paper reports on recent advances that are taking the technology into new areas. The advances include improved adhesion between encapsulated object and the encapsulating plastic, new coils that can withstand high voltage surges and the encapsulation of electronic circuitry to produce new kinds of speed sensors and novel devices for data storage and information retrieval.
On Experimental and Modeling of the Coupling between Rheological Properties and Diffusion at Polymer/Polymer Interfaces
A new technique has been developed allowing the quantification of self-diffusion and mutual diffusion at polymer/polymer interfaces using rheometry. The technique consists of measuring the dynamic moduli as a function of time for a multilayer sandwich-like assembly in molten state. The technique was tested on PS/PS and PS/PVME systems sheared in oscillatory mode under small amplitudes of deformation for different times of welding. Based on the reptation and double reptation theories [1,2], an analytical expression for the self-diffusion and mutual diffusion coefficients as a function of polymer rheological material functions was derived.
Color Measurement Techniques for Rapid Determination of Residence Time Distributions
A critical issue for extruded polymer products is the up of these processes benefit from a complete knowledge effect of residence time, thermal history, and shear history of residence time distribution. on the physical properties of the extrusion product. Unfortunately, residence time data are rarely used in the In this report, a simple technique for measuring design and scale-up of compounded products. A reason residence time distributions in polymer processing for this is the time, complexity, and specialized equipment equipment is introduced. The residence time measurement required to generate these data. In this work, the literature technique was illustrated on a lab scale twin-screw and discuss a quick, simple technique for collecting extruder, but can be used equally well to characterize residence time distribution data are reviewed. A flows in laboratory or production scale single-screw colorimeter, of the variety found in most plastics lab, is extruders, injection molding machines, and other polymer used to measure the color of the pelletized extrudate.
In-Situ Monitoring of Product Shrinkage during Injection Molding Using an Optical Sensor
We have used an optical fiber sensor for in-situ monitoring of product shrinkage during injection molding. The sensor, consisting of a bundle of optical fibers with a sapphire window at its end, is positioned in the ejector pin channel of the mold so that the sapphire window sits flush with the inside cavity wall. When the molded product shrinks, it separates from the wall and sapphire window, and establishes the geometry of a Fabry-Perot interferometer. During the molding of polystyrene, polypropylene and polyethylene, we observed optical interference fringes, and by counting fringes, a measurement of shrinkage was made.
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