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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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.
Preparation of Polypropylene/Acrylonitrile-Styrene Copolymer Alloys by One-Step Reactive Blending
The compatibilization of PP/AS blends through the addition of peroxide (DCP) was investigated. The in-situ formed grafting copolymers of PP-g-AS and AS-g-PP were then characterized by FTIR. The optimum blending condition was obtained. The maximum degree of grafting was found to be 6wt % for the 50/50 PP/AS/DCP blend. PP was more degradable than AS in the presence of peroxide at high temperature. SEM of PP/AS/DCP and PP/AAS/DCP showed a fine dispersion and a smaller domain size of the dispersed-phase particles implied that the in-situ formed grafting copolymer acts as a compatibilizer to reduce the interfacial tension between the PP and AS phases.
Unsaturated Polyester and Vinyl Ester Resins in Vacuum-Assisted Resin Transfer Molding - SCRIMP
Seemann Composite Resin Infusion Molding Process (SCRIMP) is a room temperature vacuum-assisted resin transfer molding technique developed in recent years for high strength composite fabrication. This process is being used for marine, civil infrastructure, transportation and defense applications. Unsaturated polyester and vinyl ester resins are the two major resins used in SCRIMP today. The objective of this study is to compare the resin moldability and properties of SCRIMP molded composites based on these two kinds of resins. Effects of resin type, initiator, promoter, inhibitor and retarder on the reaction kinetics, chemorheological changes and resin shrinkage were studied by using DSC, RDA and dilatometry respectively. The surface quality of the molded samples was measured by a profilometer. A kinetic model in conjunction with a heat transfer model was developed to simulate the SCRIMP process.
Simulation and Experimental Studies of a Non-Return Valve Performance during Injection Molding
This paper presents the results of the simulation of the dynamic behavior of a non-return valve during the recovery and injection stage of the injection molding cycle. A generalized Newtonian fluid model is used to simulate the flow with FLUENT software. The results of the analysis determine pressure drop, time taken for the valve to open during the recovery stage and time taken for the valve to close during the injection stage. The simulation results are compared with experimental data for three different thermoplastics including HDPE, PC and Nylon-66. Experimental data is obtained for several injection molding runs with pressure transducers installed in the barrel. In addition, the forces that occur on the ring during each molding stage and the relative rotational speeds between the valve and ring during the recovery stage were calculated.
A Practical Approach to Polymer Rheology for Quality Control
Rheological data obtained under the conditions of temperature and shear existing in conversion processes are required for the prediction of the performance of polymer resins in those processes. The capillary rheometer simulates the conditions seen in conversion processes and can be used to produce pertinent data. The ± 3 ? variation of the viscosity verses shear rate curves (over the range of shear rates seen in a process) for a resin or compound, can be used as a tool for monitoring consistency and predicting processability. When the measured viscosities for a material fall within the tube" formed by the upper and lower limits of the variation the product is consistent. If not the way the curve moves out of the "tube" will provide information on the root causes of the product variation. This talk discusses the application of the "tube" concept to a range of filled and unfilled resins using an automated capillary rheometer system that makes the "tube" concept practical for application in quality assurance and process control."
A Practical Approach to Polymer Rheology for Quality Control
Rheological data obtained under the conditions of temperature and shear existing in conversion processes are required for the prediction of the performance of polymer resins in those processes. The capillary rheometer simulates the conditions seen in conversion processes and can be used to produce pertinent data. The ± 3 ? variation of the viscosity verses shear rate curves (over the range of shear rates seen in a process) for a resin or compound, can be used as a tool for monitoring consistency and predicting processability. When the measured viscosities for a material fall within the tube" formed by the upper and lower limits of the variation the product is consistent. If not the way the curve moves out of the "tube" will provide information on the root causes of the product variation. This talk discusses the application of the "tube" concept to a range of filled and unfilled resinsusing an automated capillary rheometer system that makes the "tube" concept practical for application in quality assurance and process control."
Blends of Ethylene/Styrene Interpolymers and Other Polymers: Benefits in Applications
Ethylene Styrene Interpolymers (ESI) exhibit compatibility with a wide range of polymers due to their inherent combination of olefinic and styrenic functionality. In particular, blends of ESI with atactic polystyrene, and polyolefins including polypropylene, have been found to offer interesting and unique combinations of performance properties. Fundamental blend morphology, structure/property relationships, and processability of ESI blends are discussed. Examples and benefits of such blends in applications such as molded articles, films, and foams are discussed.
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