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.
|= Members Only|
Thermal Stabilization of Polymers Containing Residual Catalysts
Residual polymerization catalysts are known to promote degradation reactions in many polymeric materials. Such reactions were studied in poly(methyl methacrylate) (PMMA) doped with a typical catalyst at temperatures slightly above Tg using thermogravimetric analysis. Several novel approaches to minimizing the adverse effects of residual catalyst on thermal stability were investigated. Extraction of residual catalyst using liquid CO2 and a fluorinated chelating agent was shown to significantly improve the stability of PMMA film. Encapsulation of the residual catalyst using strongly a binding chelating agent, an azo-derivative of a crown ether, is also shown to enhance thermal stability.
Interfacial Tension Measurement of Polymers with the Pendant Drop Method: A Comprehensive Experimental Review
The pendant drop apparatus is the most reliable and accurate method of measuring the interfacial tension of polymer melts. However, the lack of a defined experimental method is a possible contributor to conflicting data in the literature. This paper reviews all practical aspects of pendant drop experiments with polymers including material preparation, syringe diameter selection, drop stability, necking and capillary effects, equilibration time and interfacial tension measurement error, repeatability and dependence on drop size. Original experimental data with polyethylene and polystyrene resins is discussed and compared to literature results.
Fabrication and Characterization of Electro-Optic Polymeric E-Field Sensors
The guiding of light beams along dielectric layers, first realized experimentally in the early sixties has stimulated the growth of a new class of passive and active components using light guided by films deposited on wafer-like substrates. These optical components provide the advantage of greater bandwidth and immunity from electromagnetic radiation hence making them become sufficiently effective to herald the beginning of a sophisticated technology called integrated optics. Current integrated optics technology is based upon inorganic crystalline LiNbO3. The concept of integrating an electro-optic polymer into a reverse poled Mach-Zehnder modulator to be used as an electrode-less E-field sensor is discussed here.
Structural Investigation of Plasma-Polymerized Pyrrole Films
Fourier-transform infrared spectrometry (FT-IR) and X-ray photoelectron spectroscopy (XPS) have been carried out to characterize plasma-polymerized pyrrole (PPy) films deposited under two deposition conditions, viz. high plasma excitation power/low monomer pressure (i.e. HW/LP) and low plasma excitation power/high monomer pressure (i.e. LW/HP) in RF and DC glow discharges. LW/HP PPy films deposited with a pulsed DC discharge were also investigated. Substantial differences were found between the structures of the films deposited under different conditions. The LW/HP films appeared to contain less unsaturation and conjugation than the HW/LP films. A comparison is made of the FT-IR spectrum of pyrrole monomer with those of PPy films and electrochemically polymerized pyrrole, which consists of disubstituted pyrrole rings. Evidence is presented that in low power RF conditions, the pyrrole ring structure can be maintained. The plasma polymerization processes of pyrrole under different deposition conditions are proposed.
Study of the Curing of Polymerizable Reaction Mixtures, PMR-15
The curing of PMR-15 was investigated using Fourier transform infrared spectroscopy (FT-IR) as a function of time (3 ? t ? 150 mins) and temperature (65 ? T ? 300°C). Imidization was measured by the changes in the imide carbonyl absorption at 1778 cm-1. The imide carbonyl absorption increased with temperature and time. Very little Imidization, <5%, occurred at 65°C irrespective of time. However, between 95 and 300°C, the extent of imidization was completed in 2.5 h at 300°C. FTIR also showed that thermal imidization and anhydride formation occurred simultaneously at high curing temperatures and longer curing times. Anhydride formation peaked at 0.5 h of curing at 135°C. Kinetic analysis for imidization was performed at low conversions. An Avrami-type kinetic analysis for imidization was also performed.
Determination of the Mechanism of Formation of Polypyrrole on Reactive Metals by Infrared Spectroscopy
The formation of polypyrrole coatings on steel was performed by an electrochemical process in aqueous oxalate solutions. The pH of the reaction medium and applied current density were varied from 1.2 to 8.4 and 0.56 to 5.63 mA/cm2, respectively. The mechanism of formation of polypyrrole coatings on steel, in acdic medium (pH < 6) was found to differ from that in basic medium (pH = 8.4). In acidic reaction medium, formation of polypyrrole on steel occurred in three stages: (i) dissolution of steel, (ii) passivation of steel and (iii) formation of polypyrrole. No passivation period was observed in the basic medium. The mechanism of passivation of steel and the composition of the coatings was investigated by reflection-absorption infrared spectroscopy. Our results show that increasing the current density decreased the passivation period. In acidic medium (pH =_6.0), minimal passivation time was observed to occur at a pH 2.4. IR analysis shows that passivation of steel was due to the formation and precipitation of FeC2O4.2H2O passive films on steel .
Influence of Adhesion Promoters on Properties Short Glass Fiber/Polypropylene Composites
Acrylic acid grafted polypropylene (PP-g-AA) and two maleic anhydride grafted PP (PP-g-MA) of different viscosities and grafting levels are used, together with pyrolyzed fibers and ?-aminopropyl-triethoxysilane sized fibers. Mechanical characterization on injection-molded parts and fragmentation test on single fiber composite (SFC) are performed in order to correlate adhesion and performances. A higher level of grafting appears to be an important factor for best adhesion enhancement. The crystalline morphology was characterized in previous work and was found to play a key role on the resulting properties, in spite of good interfacial interactions. Highly grafted PP-g-MA is the best adhesion promoter characterized in this work.
Orientation Effects on the Weldability of Polypropylene Strapping Tape
Polypropylene strapping tape is commonly sealed by welding using high temperature tools. Despite the widespread use of the technique no work has been done to study the influence of the welding process parameters on the properties of the joint. In this work polypropylene strapping tape, produced with different draw ratios and types of surface embossing, was welded with a standard semi-automatic strapping machine. The effect of the process parameters (temperature, sealing pressure and surface profile of the sealing tool) and the tape properties (draw ratio and embossing pattern) on the microstructure and the joint strength was studied. An optimal temperature range could be identified. The draw ratio of the tape influences the weld efficiency.
Characterization of PP/PPgAA Blends by Contact Angle
Polypropylene (PP) was functionalized with Acrylic Acid (AA) by means of a radical-initiated melt grafting reaction. The content of AA grafted onto PP was determined by using acid-basic titration. Blends of PP with 0 to 100% wt of Polypropylene grafted with Acrylic Acid (PP-gAA) were prepared by melt mixing. The effect of the modified polymer content on the surface of cast films was characterized through contact angle and ink adhesion measurements as well as attenuated total reflection infrared spectroscopy (FTIR-ATR). The contact angles of water on cast film surfaces of PP/PPgAA blends decreases with increasing modified polymer content. A notorious improvement on ink adhesion on the surface was observed when increasing the content of modified polymer. From FTIR-ATR spectra of the blends, the carbonyl index on the films surface was calculated. It was found that the higher the carbonyl index, the lower the contact angle value for the polypropylene blends.
A Process Comparison of Orbital and Linear Vibration Welding of Thermoplastics
This paper reviews a study comparing the physical differences between orbital and linear vibration welding of thermoplastics. For the same welding conditions, it was found that orbital welding dissipated 56% more power than linear vibration welding in Phase I (solid-to-solid friction) of the process. Similarly, in phase III (steady state) orbital welding dissipated 100% more power than linear vibration welding. The duration of phase I and phase III was 36% and 50% shorter for orbital welding than for linear vibration welding. A theoretical comparison for phases I and III were consistent with the experimental results. Comparison of micrographs of welded sections shows that orbital welding produces thinner weld lines than linear vibration welding.
Development of Underfilling Encapsulant Based on Ternary Systems of Benzoxazine, Epoxy, and Phenolic Resins
We have developed a new polymeric system based on the ternary mixture of benzoxazine resin, epoxy resin, and phenolic resin. Low melt viscosity resin renders void free specimens with minimal processing steps. The material properties show a wide range of desirable reliability and processability which are highly dependent on the composition of the monomers in the mixture. A glass transition temperature as high as 170°C and considerable thermal stability up to 370°C can be obtained from these systems. The materials exhibit promising characteristics suitable for application as underfilling encapsulation and other highly fiilled systems. the curing aid of polybenzoxazine. The mixture of these three resins to form the ternary systems is believed to provide a great variety of resin properties suitable for wide applications, particularly in the microelectronic application and the highly filled systems.
Application of Composite Technology to Firearms: A Rifle Barrel
A composite rifle barrel was developed. Initial prototypes were developed to aid in understanding the complex interaction of a steel / graphite fiber-epoxy composite when subjected to the short duration dynamic loading environments caused by firing the rifle. Design improvements include creating residual stresses in the composite and the steel materials, creating crack stops to stop crack propagation through the composite material, and steel / composite interactions during cyclic loading. Ultimately, the composite material was used in conjunction with a steel skeleton to produce a lighter, cooler, longer lasting, and more accurate rifle barrel which is currently in production.
Modeling Extrusion Processability for Materials with Various Molecular Parameters
A simple superposition model was used to define the relationship between molecular weight distribution and shear viscosity for linear polymeric systems. The model was used to simulate melt extrusion in a single screw extruder with an annular die attached (3D isothermal flow simulations). The influence of material parameters (molecular weight and polydispersity) on the system operating point, power consumption and residence time distribution was analyzed. The model was used to develop windows of processing conditions for resins of different material properties. The effect of blending homologous polymers on material processability was also analyzed.
Advances in Polyolefin Stabilization
The worldwide arena of polyolefins is in a state of [r]evolution regarding the development of catalysts, polymerization processes, and olefin polymer compositions. Accordingly, the polymer producers, as well as the manufacturers of downstream products, are interested in new developments in stabilization technology that may help to maintain and even improve" the physical and aesthetic properties of their new products. Representative examples of "improvements" might include: better maintenance of melt flow rates lower initial color and better color maintenance enhanced long term thermal and light stability inhibition of gas fade discoloration enhanced additive compatibility higher clarity resistance to interactions with other additives reduced taste and odor and the suppression of visual imperfections (gels). The track record of traditional stabilization systems to fulfill the requirements of polyolefins is well known. Nevertheless intense investigations have been underway over the last few years to develop new stabilizer products based on chemistries that deliver recognizable improvements regarding the key measures described above. Most often this requires the discovery and development of new product chemistries. However there are other approaches which involve clever ways to use chemistries that have been knownbut perhaps underutilized. The impact of these new stabilization chemistries has been examinednot necessarily to simply displace existing stabilizers but also to differentiate and develop new markets and opportunities. Traditional "phenol based" as well as alternative "phenol free" stabilization concepts have been explored in new applications and the results were found to be quite promising. The performance of these new stabilization concepts and their applicability to new markets and opportunities will be discussed."
Advances in Polyolefin Stabilization
The worldwide arena of polyolefins is in a state of [r]evolution regarding the development of catalysts, polymerization processes, and olefin polymer compositions. Accordingly, the polymer producers, as well as the manufacturers of downstream products, are interested in new developments in stabilization technology that may help to maintain and even improve" the physical and aesthetic properties of their new products. Representative examples of "improvements" might include: better maintenance of melt flow rates lower initial color and better color maintenance enhanced long term thermal and light stability inhibition of gas fade discoloration enhanced additive compatibility higher clarity resistance to interactions with other additives reduced taste and odorand the suppression of visual imperfections (gels). The track record of traditional stabilization systems to fulfill the requirements of polyolefins is well known. Nevertheless intense investigations have been underway over the last few years to develop new stabilizer products based on chemistries that deliver recognizable improvements regarding the key measures described above. Most often this requires the discovery and development of new product chemistries. Howeverthere are other approaches which involve clever ways to use chemistries that have been known but perhaps underutilized. The impact of these new stabilization chemistries has been examined not necessarily to simply displace existing stabilizers but also to differentiate and develop new markets and opportunities. Traditional "phenol based" as well as alternative "phenol free" stabilization concepts have been explored in new applications and the results were found to be quite promising. The performance of these new stabilization concepts and their applicability to new markets and opportunities will be discussed."
Considerations in the Computer Aided Engineering of Pallets
Plastic pallets and containers are used increasingly for storing, moving and warehousing various industrial and consumer products, thanks mainly to its several benefits besides environmental consciousness. The conventional wooden pallets are limited in their load capacity, useful life, cleanability, and above all, imaginative product-specific design. Contrarily, the structural foam molded plastic pallet, meets the demands heavy payloads, dynamic and impact loads, hostile weather conditions, size limitations, process effects, strength and stiffness requirements. Plastic pallets are used for up to 30000 lbs carrying capacity. Beyond their passive appearance, the plastic pallets are a product of engineering optimization encompassing materials, technology, design, stress analysis, and several end-use specific constraints. This paper is a review of the various considerations involved in the computer aided engineering of pallets as a product class.
On-Line Monitoring of Polymer Orientation during Injection Molding
A non-invasive, on-line technique for monitoring the orientation of polymer in the mold cavity during injection molding is demonstrated. The propagation velocity of an ultrasonic shear wave can be used to detect anisotropic behavior in the mechanical properties of a solid. Thus, an ultrasonic shear transducer embedded in an injection mold produces a signal that is sensitive to polymer orientation. The technique is shown to be quite sensitive for semicrystalline polymers, but much less effective for amorphous polymers. Sensor results are compared to mechanical tests performed on plastic specimens.
Nylon 6,6 Glass Reinforced Composite Material for Automotive Air Intake Manifold Application
There are many advantages to air intake manifolds molded from Nylon 6,6 Glass reinforced composite material versus a pressure-cast aluminum manifold. Weight is significantly lowered and production costs generally are reduced. Performance improves with the precise control of the interior surface finish and reduced air induction temperatures. The Nylon 6,6 Glass reinforced composite material can be molded into intricate shapes by injection molding or lost-core process with reduced machining operations as well as Nylon 6,6 material is easily recycled. Production costs will continue to decrease as optimization of material, process and part integration increases. This study evaluates Nylon 6,6 Glass reinforced composite material in terms of the intake manifolds material key requirements such as thermal, heat aging, fatigue, impact, creep, stress and chemical resistance including multi fuels. This study would assist engineers in designing intake manifolds using Nylon 6,6 Glass reinforced composite material.
India's Emerging Automotive Industry
India is the world's largest democracy with a population of approximately 940 million people of which 250 million speak English. The country has a large technically trained work force, a middle class that exceeds the total population of the United States and twenty-three cities with a population of more than one million people. As a result, India has emerged as the 11th largest industrialized country in the world with the 10th largest Gross Domestic Product. According to the World Bank projections of the 15 largest economies (GDP Index) in 2020, they project India as number four behind China, U.S.A. and Japan (see Figure 1). In 1991 as the Indian government began to implement it's comprehensive reform program by liberalizing foreign investment policies, the country began to see a large influx of direct foreign investment. Consequently, India has become one of the prime candidates for foreign investment and joint ventures in the automotive industry. The industry reached a record $5.5 billion in 1995. The annual growth for passengers cars and utility vehicles this coming year is expected to be approximately ten percent while the commercial truck market is expected to increase at a rate of nine percent. There are problems within the Indian automotive industry caused by the recently announced Budget '98. Budget '98 has temporarily killed the initiatives to innovate, removed the incentives to modernize and destroyed the motivation to become and remain competitive in cost, quality, reliability and performance. Its implications and effects are to provide protection to the outdated models, sustain the manufacturing technologies that should be discarded and supports managements who refuse to change with the times. Foreign investment has had a direct impact on the $2.5 billion dollar automotive components industry as well. In the coming year industry analysts expect over $380 million to be invested in the components sector.
Three-Dimensional Finite Element Analysis of a Total Knee Prosthesis
A common problem with knee prostheses is wear failure of the polyethylene tibial plateau. The objective of this study was to compute the stresses generated in the polyethylene, and to determine how the stresses varied with changes in the minimum polyethylene thickness and the joint load. High stresses generated in the polyethylene lead to failure by wear. A three-dimensional finite element model of a metal-backed polyethylene tibial component with a conforming femoral component was generated. Nonlinear GAP elements were used to define the contact between the articulating femoral and tibial surfaces. Four load cases were considered. Two cases simulated level walking and two simulated stair climbing. For each activity, one load case considered the joint load as being equally shared between the two condyles, while the other case assumed that the joint load was acting only on one condyle. Six different model cases were considered each having a different minimum polyethylene thickness (tmin). Each model case was analyzed for each of the four load cases. The maximum Von Mises stress exceeded the yield strength of polyethylene for all thicknesses for the extreme load case of stair climbing. For tmin = 8 mm, the maximum Von Mises stress was less than the yield strength for all the other load cases. The maximum shear stress was less than the failure value for all cases. The optimum minimum polyethylene thickness for the tibial component of a knee prosthesis was concluded as 8 mm. With this thickness, the polyethylene would not yield during normal level walking and during stair climbing, yielding and subsequent wear of the polyethylene would be reduced. For a minimum thickness greater than 8 mm, the undesirable effect associated with over-resection of bone become dominant.
We're sorry, but your current web site security status does not grant you access to the resource you are attempting to view.