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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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.
A New Route for Spinning Inherently Conductive Polyaniline Fibres
We have developed a new acid-solution processing route for the conjugated polymer, polyaniline (PANi) . This new processing route has allowed us to demonstrate wet-spinning of inherently conductive PANi fibres in a one step process. The fibres have been spun into various coagulation solvents. 'As spun' fibres have Young's moduli of 40 - 60 MPa, ultimate tensile strengths (UTS) of 20 - 60 MPa and electrical conductivites of 70 - 150 Scm-1. These fibres draw at room temperature, to an extension of ~500 %, with a concomitant increase in conductivity of up to a maximum of 1950 Scm-1. It is also possible to draw fibres at elevated temperatures, then anneal them to give fibres with Young's modulus of 2 GPa and UTS 97 MPa whilst retaining conductivities of ~ 600 Scm-1.
Injection Molding of Sub-µm Grating Optical Elements
The potential applications of micro-structured optical components are numerous. The mass replication of (sub-) micron structures remains a challenge, however. For an application in a CD light path a ?/4-grating element has been designed and successfully produced that requires the replication of structures 200 nm wide and 1600 nm deep (aspect ratio of 8). A big part of the challenge is the production of mold inserts containing such structures in a suitable mold material in addition to finding the process conditions in order to successfully replicate and release such structures with a conventional thermoplastic molding equipment. It is shown that such structures can indeed be molded with Polycarbonate in a conventional molding operation. A more stable process, however, is obtained by splitting the functions over two surfaces in this way reducing the aspect ratio to 4
Deformation Mechanism of Thermoplastic Vulcanisates Investigated by Combined FTIR and Stress-Strain Measurements
Thermoplastic vulcanisates are blends of a thermoplastic matrix with a crosslinked rubber. The rubber is dynamically crosslinked during blending. Due to this procedure it is possible to get phase inversion and disperse a large amount (up to 80%) of rubber into a thermoplastic matrix. These materials, which are in our case based on polypropylene (PP) and EPDM, show a high elasticity upon tension and pressure. This, despite the fact, that the matrix consists of polypropylene, which should be deformed plastically. To understand this phenomenon we investigated these materials with time-resolved infrared spectroscopy during tensile tests. It could be shown that the amorphous and crystalline EPDM regions show orientation directly proportional to the applied strain, whereas the crystalline PP shows a very small orientation up to 300% macroscopic strain. This fact can only be explained by a model which assumes a very inhomogenous deformation of the PP matrix and a good adhesion between matrix and dispersed phase. Besides these experiments finite element calculations were done to understand the influence of the morphology of the dispersed phase and the constitutive behaviour of the matrix on the recoverability of TPVs.
Diffusion Coefficients of Single Component Linear n-Alkanes
A high coordination lattice is used in the simulations of various n-alkanes above their melt temperatures. All n-alkanes used are linear, single component, single chain systems, ranging from C12H26 to C316H634. Metropolis Monte Carlo algorithm is adopted for the moves on the high coordination lattice. All moves are possible as long as the bond length on the lattice is not altered. Short range interactions are calculated with an extended rotational isomeric state (RIS) formalism and long range interactions are calculated with a spherically isotropic Lennard-Jones (LJ) potential both of which satisfy the specifics of the coarse grained lattice.
Performance of Di-N-Hexyl Phthalate in Flexible Vinyl Formulations
Low molecular weight esters have been available to the PVC compounder for many years. They have found a significant niche in the performance vs. permanence compromise as a compound ingredient that provides manufacturing efficiency or some special property with adequate permanence for many vinyl applications. In many respects, low molecular weight esters are the processing aids of the plasticizer family. This group of plasticizer may be said to include C4 to C7 dialkyl phthalates, the benzyl phthalates and the benzoic acid esters. This paper will introduce and compare di-normal hexyl phthalate (DNHP) to other phthalates against which it will directly compete.
Dimensional Changes of PPS in Environmental Testing
The actuator arms in some hard drives were found to distort after being subjected to an 80°C environmental test. This distortion was believed to be due to a relaxation of thermal residual stresses in the glass filled polyphenylene sulfide component of the arm due to the molding process. Changes were made in the molding process and this diminished the problem but did not eliminate it. Differential scanning calorimetry test on the plastic revealed that physical aging of the PPS was occurring during the 80°C environmental test and the changes in the molding process would have little impact on the motion which resulted in this process.
Development of Filling Imbalances in Hot Runner Molds
When manufacturing plastic parts from multi-cavity tools by means of injection molding, it is common to use naturally balanced runner systems to deliver the melt to each cavity with identical flow conditions. However, a common occurrence associated with naturally balanced runner systems is that the parts molded in the inner cavities, closest to the sprue, are heavier and larger than the outside parts. Recent studies suggest the inconsistencies be due to unsymmetrical shear distributions created as the melt splits to flow through the various branches of a runner system (1-2). This paper shows the mold-filling imbalances experienced with geometrically balanced runner systems of multi-cavity hot runner molds, through computational fluid dynamics analyses.
The Effect of Phenolic Regrind on the Mechanical Properties of HDPE
The possibility for recycling cured phenolic material was evaluated by testing mechanical properties of High-Density Polyethylene (HDPE) containing phenolic regrind material. The mechanical properties evaluated were: modulus of elasticity, percent elongation, tensile strength, and impact strength. Four different levels of phenolic regrind were used for evaluation with four different levels(4.76, 9.09, 16.7%) of phenolic regrind used in the comparison. The results demonstrated that with higher levels of phenolic regrind in the base HDPE material, certain mechanical properties degraded, with increased brittleness the most apparent effect.
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