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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Orientation, Stress and Shrinkage Relationships for Amorphous and Semicrystalliane Polymers
The dimensional stability, such as shrinkage strain or stress, of oriented films and sheets is an important factor in the application of these articles. High shrinkage may be desired for some applications or need to be minimized for others. Thus shrinkage control and monitoring is of paramount importance. On the other hand, it is well established for most polymer melts that the birefringence is simply related to the stress through the stress optical rule, and simple theories relate the stress and birefringence to the strain. In this paper, we investigate these relationships for oriented amorphous (polystyrene, PS) and semi-crystalline polymers (PE, PET, and sPS) in relation with their shrinkage stress and/or strain. For low orientations, it is found that the stress and strain can be simply related to birefringence. For semicrystalline polymers, the relationship is more complex. At high degrees of orientation, some modifications to the theories are required.
Miscible Blends of Nylon 6 and TDAI, an Oligomeric Aromatic Nylon, with Improved Melt Flow and Moisture Resistance Properties
A high Tg, aromatic nylon oligomer based on poly (tolyleneisophthalamide) (TDAI) was designed and evaluated as an additive for melt blending with conventional aliphatic nylons (PA 6 and PA66) to achieve miscible blends with improved Tg and property retention upon moisture equilibration. Blending only 10w% of TDAI in GF-PA6 and GF-PA66, a nearly complete retention of modulus and strength could be achieved at 50%RH, validating the general concept of wet Tg enhancement of nylons through miscible Tg-boosting additives. Moisture insensitive oxygen barrier properties could also be obtained in cast PA6 film. The oligomeric nature of TDAI contributes to improved melt flow in PA 6 and permits higher glass loading to give products with moisture-insensitive stiffness and dimensional stability.
Microstructural Effects on the Properties of Injection Molded Nylon 6 Nanocomposites
Nylon 6 nanocomposites consisting of extremely thin, nanometer scale dispersions of platelet type silicates have been prepared and their injection molded properties and morphology have been investigated. The high surface area of such silicate dispersions contribute to a high reinforcement efficiency at low loadings, resulting in high specific modulus, strength and DTUL. However, such ultra-thin platelets cause some unusual structure development during the injection molding. Flow induced orientation of the platelets and an apparent surface nucleation promotes faster crystallization of nylon 6. Higher crystallinity was observed in the nylon 6 nanocomposites, particularly at the surface and in thin-wall moldings compared to the conventional nylon 6. The crystallization, skin-core morphology effects in the injection molded nylon 6 nanocomposites correlate well with the observed mechanical properties, weld-line and surface UV/ weathearing behavior.
Effect of the Addition of a Polycarbonate on the Cure of an Epoxy Thermoset System
During the cure of a thermoset-thermoplastic blend two-phase morphologies may be formed. The phase separation process can be controlled by manipulation of the rate of polymerization of the thermoset system. In this work, the effect of the addition of different amounts of polycarbonate (PC) on the rheokinetics of an epoxy thermoset system is presented. The reactive system used was diglycidyl ether of bisphenol-A cured with 4-4 diaminodiphenylsulfone. The blends of the PC and the epoxy resin were prepared using two different procedures: (a) hot melt blending and (b) dissolution in a common solvent. The kinetics was followed by differential scanning calorimetry and the change in the rheological properties during the curing by dynamic rheometry.
Morphology Development in Carbon Dioxide Assisted Polymer Blending In Batch and Continuous Processes
The compatibility of individual homopolymers is one of the most important parameters influencing polymer blending. Often times blending involves components with vastly different viscosities and interfacial tensions. Supercritical carbon dioxide can be added to polymer melts as a processing aid such that effective polymer blending will occur. A blend system of a high viscosity polymethylmethacrylate (PMMA) and low viscosity polystyrene is analyzed in this work. Carbon dioxide has a higher affinity for PMMA than for polystyrene (1). Therefore, a greater plasticizing effect will occur for the PMMA than for the polystyrene. The improved results in polymer blending will be shown in this work. The morphology development of the polymer blends is analyzed in a high-pressure batch mixer and the continuous extrusion process.
Viscoelastic Properties of Multiphase Polymeric Blends
Rheological analysis of multi-phase systems is very difficult because the morphology is strongly related to the flow history. The small amplitude oscillatory shear flow does not affect the morphology and is very useful to predict the viscoelastic behavior of immiscible blends. In this work we study the dynamic rheological properties of Polypropylene based ternary blends with linear low density polyethylene and ethylene/propylene terpolymers of different viscosities taking into account the effects of changing the composition and concentration of the dispersed phase. The predictions of a constitutive equation for emulsions of viscoelastic fluids are also included.
Evolved Gas Analysis of Polymer Decomposition Processes via Highly Integrated Thermal/Spectroscopic Measurement Techniques
Simultaneous thermal analysis techniques, for example TG-DSC/DTA (Thermogravimetric-Differential Scanning Calorimetry/Differential Thermal Analysis), yield vital information on polymer makeup based on heat flow behavior and mass change characteristics during heating. These techniques offer little direct information, however, on exact composition of evolved gas products. It has recently been found quite powerful to combine simultaneous thermal analyzers directly in tandem with both Mass and FTIR (Fourier Transform Infrared) spectrometers. The challenge is effectively coupling the instruments such that optimized evolved gas analysis is possible. Practical applications of evolved gas analysis for polymeric materials include analysis of decomposition and aging processes, additives, residues, outgassing, desorption behavior and more. This paper will examine results of thermoanalytical experiments on polymeric materials via TG-DSC/DTA closely coupled with both a quadrupole mass spectrometer (QMS) and an FTIR spectrometer.
Advancements in Polymer Characterization Using Fast Response DSC at Elevated Temperatures and Pressures
Proper characterization of polymers by Differential Scanning Calorimetry (DSC) may be compromised when calorimetric transitions coincide or when components volatilize at the same time as critical transitions are expected to occur. To increase the utility of DSC for polymer characterization, it is highly desirable to minimize system time constant and improve signal-to-noise ratio in order to improve sensitivity and peak resolution. As well, operation under conditions of increased pressure may succeed in preventing unwanted volatilization, permitting resolution of certain transitions. This paper describes in detail specific polymer applications emphasizing the significance of DSC cell time constant reduction in terms of improved peak resolution as well as the importance of cell baseline stability throughout a broad temperature range and over increasing pressure conditions.
Stabilizers for Peroxydicarbonate Initiator Solutions
Liquid dialkylperoxydicarbonates are used as initiators in the PVC industry. Due to the thermal reactivity of these initiators, they require very low temperature storage, shipment and handling. At temperatures above 10°C, most undergo auto-accelerated self-induced decomposition. In other words, their self-accelerating decomposition temperature (SADT) is exceeded. New additives have been discovered which increase the SADT of the initiators. These additives effectively stabilize the product, making them safer to handle, store, and ship. The proprietary additives and a mechanism of stabilization will be discussed. We will also include a section concerning the implications these products have for future initiator formulation.
Fish Oil Polymeric Systems: Synthesis, Structure, Properties and Their Relationships
Fish oil or conjugated fish oil was copolymerized with divinylbenzene and norbornadiene or dicyclopentadiene using BF3·OEt2 as an initiator in an effort to develop useful biodegradable polymers with rationally designed structures from natural renewable resources. Dynamic mechanical analysis, DSC, TGA and nuclear magnetic resonance spectroscopy have been used to characterize the resulting fish oil polymers. The results show that viable fish oil products ranging from rubbers to hard plastics may be synthesized by changing the type and amount of the comonomers used. The fish oil products are thermosetting polymers having highly crosslinked structures, glass transition temperatures ranging from 50 to 130°C, room temperature modulus of about 109 Pa, and excellent thermal stability, making the products useful for applications where current biodegradable plastics are not useable.
Development of New Flame-Resistant, Lightweight Foam Composites Based on Polyimides
We report a method for making novel, lightweight (0.3-1.1 kg/dm3) polymer composites based on high-temperature foam polyimide binder, carbon fiber or organic fiber felt. The density and mechanical properties of the foam composite can be varied over a wide range, depending on the volume contents of the fiber and air pores. The thermal degradation temperature of the foam composite is around 570°C, and thermolysis products of foam binder are comparable to those of wood. The combination of excellent thermal stability, superior specific mechanical properties, exceptional flame resistance of polyimides, and facile processing of the foam composites can provide unusual performance for new design of advanced materials and structures.
Rheological Investigation of Effect of Coupling Agent and Particle Size on Processing of Polymer-Bonded Magnets
The effect of coupling agents and particle size on melt rheology of polyphenylene sulfide-bonded neodymium-iron- boron (Nd-Fe-B) alloy magnets was studied with oscillatory flow experiments to accelerate efforts to optimize their processing. The minimum viscosity of the polymer-bonded magnets near 290°C was obtained with Nd-Fe-B fillers (106-150 particle size range) that were coupled with a silane coupling agent. All the samples tested followed power-law fluid flow behavior. Morphological and dynamic mechanical analysis of the samples showed that the beneficial function of the coupling agent may be ascribed to enhanced wetting of the magnetic Nd-Fe-B powders by the polymer, improving the processability of the polymer bonded magnets.
Batch and Continuous Processing of Protein Films
This research is directed at the thermal processing and physical characterization of films derived from natural proteins, viz. soy, corn-zein, egg white and beef-broth. Twin screw extrusion was employed for pre-process compounding of proteins and the plasticizer. The thermal processing was accomplished with compression molding (a batch process) and extrusion (a continuous process). Single component soy films were light yellow in color, translucent, flexible and well consolidated, with a thickness of approximately 300µm. The tensile strength of these films was about 3 MPa. Continuous chill-roll film extrusion was also carried out and the process is being refined.
Advances in the Fabrication of UHMWPE for Joint Prostheses
It is well recognized that Ultrahigh Molecular Weight Polyethylene(3.6x106) (UHMWPE) has been used as a component in joint prostheses for over 95 years. Essentially all fabricated UHMWPE during this period has exhibited incomplete fusion and/or severe molecular weight degradation. It is most likely that these features have compromised the potential wear resistance as well as the mechanical properties of this material. By fabricating UHMWPE in a vacuum, complete densification without fusion defects while maintaining the 3-4 million starting molecular weight was achieved. This paper discusses the results of the vacuum fabrication of UHMWPE.
Hard Tools from Soft Tools via PowderFlo Technology
The ability to procure rapid tooling for plastic molding and other near-net shape forming processes remains one of the largest technical challenges facing our manufacturing industry today. Advances in rapid prototyping and desk top manufacturing e.g., selective laser sintering, solid free forming, ....., etc have cut lead-times by as much as and are capable of producing relatively precise tooling which requires minor secondary machining. This paper presents a new technology developed by AlliedSignal which is capable of fabricating metal and ceramic components via powder injection molding, as well as the added capability of producing hard tooling from soft tooling.
The Use of Chemical Coupling Agents to Improve the Performance of Polymer Bonded Nd-Fe-B Magnets
Due to their poor heat-resistant properties, polymer bonded magnets are limited in their applications in aggressive environment. By using high temperature engineering polymers the heat-resistance of polymer bonded magnets can be significantly improved. However, the extreme tendency for thermal oxidation of Nd-Fe-B alloy powder limits the use of high temperature polymers. This paper discusses the application of silane coupling agents to the thermoplastic polymer bonded Nd-Fe-B magnets. The results show that after the treatment of coupling agent, the thermal stability and oxidation/corrosion resistant properties of the Nd-Fe-B alloy powder at high temperature improved significantly, making it usable for high-temperature processing and high-temperature application. An enhanced wetting of the Nd-Fe-B particles in polymer matrix has been observed. The bonding between the Nd-Fe-B powders and polymer matrix was improved by the coupling agents. In turn, the enhanced bonding between the powder and the polymer dramatically increased the mechanical properties of polymer-bonded Nd-Fe-B magnets.
When Does Plastic Yield Occur?
The yield point of a ductile plastic material is commonly taken to be the maximum in the engineering stress-strain curve conducted in a constant cross-head rate experiment. With most plastic materials permanent strain actually occurs well before the maximum point is reached. In metals the point where permanent strain occurs can be determined by performing loading-unloading experiments. In plastics the determination of this point must also take into account the time under load because plastic deformation processes are time/rate dependent. There is a corresponding change in the microstructure when permanent deformation occurs. Uniaxial tensile deformation experiments on a polyacetal copolymer are used to illustrate these points. Scanning electron microscopy is used to show that permanent microstructural deformations develop over time. In polyacetal the deformation involves the formation of voids and fissures.
Designing Toughened Plastics through Control of Morphology and Properties of the Toughening Phase
The fracture resistance of homogeneous plastics can be increased by the incorporation of a second phase which may be an elastomer, a thermoplastic, or even an inorganic material. The choice of the second phase depends on the intrinsic deformation mechanisms of the host matrix. The microstructure of the toughening phase may have significant effects on the toughening efficiency. The inclusion of a third phase in the toughening phase is often desirable for facilitating cavitation. The desirable properties and morphologies of the toughening phase for triggering such mechanisms are discussed in this paper.
Design Tools for Rapid Thermal Cycling
Mold temperature control is very important in injection molding, influencing both the part quality and production rate. The solid freeform fabrication (SFF) processes such as 3D Printing have demonstrated the ability to construct complex internal channels inside the tool to improve the process temperature condition. By running the hot and the cold oil alternately through the conformal channels, the mold surface temperature is well controlled so that isothermal filling and rapid cooling are achieved for the high part quality and the short cycle time. A low thermal inertia tool and a rapid thermal cycling system are being developed at MIT. This paper discusses models and design rules involved in the design of tools for rapid thermal cycling.
Scratch Resistance and Material Property Relationship in Polymers
The scratch/mar damage in polymers is a complicated mechanical process and cannot be directly related to material properties of polymers. Scratch performance of materials is determined both by scratching stress field and by various material properties. Testing methods, which include two types of scratch tests and a depth sensing indentation test, are described. A scratch model is applied to simulate the scratch process under constant load. The roles of basic material properties, i.e. Young's modulus, yield stress, tensile strength, friction coefficient, hardness, elastic recovery on scratch resistance of polymers are addressed. Approaches for improving scratch resistance in relationship to material properties are discussed.
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