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.
An injection molded container has been developed for built up roofing asphalt. The container is consumable in the roofer's kettle unlike the paper carton it supplants. The development of the container consisted of three elements. The first element was the development of a compound that could be injection molded, withstand filling with molten asphalt, and later melt completely in the roofer's kettle. The second element was the design of a container that met processing, cost and customer requirements. The third element was the development of a cost-effective injection molding process.
Honeycomb-cored composite sandwich panels are widely used in commercial airplane interiors. Sandwich-panel warpage can cause assembly difficulties and has been a deterrent to implementation of determinant assembly techniques. A series of statistical experiments were used to minimize sandwich-panel warpage on an airplane stowage-bin shell. Warpage was broken down into three components to facilitate analysis. Twist was shown to be influenced by prepreg orientation. Spring-in was affected by the presence of a decorative poly(vinyl fluoride) film; this effect was counteracted primarily by the addition of a ply of style-120 prepreg on the opposite side of the panel. The additional ply of 120 prepreg also helped to minimize bow.
A numerical analysis of the RTM/VARTM processes using an hp-adaptive finite element method is presented in this paper. The constitutive behavior of the resin is modeled using the Carreau-Yasuda 5-parameter model with the WLF and the Arrhenius functions for describing the temperature dependence of the viscosity. In addition, the viscosity can also be read in as a tabular function of the effective shear rate and the temperature. The RTM process is modeled as a three-dimensional, two-phase flow of resin and air (weakly compressible fluid) using a modified Darcy's model. Examples demonstrating the role of SUPG smoothing, viscosity variation, vacuum conditions, and dynamic adaptivity are presented in this work.
Solid-State Shear Pulverization (S3P) is a novel process that uses mechanical energy to cause mechanochemical alteration of some of the polymer chains. The process pulverizes polymers and results in fine powders. Fragmentation events involve a limited amount of chain cleavage depending upon the levels of mechanical strain developed and the molecular weight distribution of the materials. Several virgin ethylene homo- and copolymers were used in this study. It is seen that S3P can alter the flow properties but leaves molecular weight distributions and the thermal properties of these polymers unchanged.
Effective dispersion of chopped glass fibers into thermoplastic matrices is critical for achieving optimum properties. In an effort to further understand the mechanisms by which dispersion occurs, model experiments are conducted using 4 mm long chopped glass fiber bundles embedded in polystyrene. The effects of the process variables of temperature and shear rate upon the onset and mechanism of dispersion are investigated with optical microscopy. Two distinct breakup mechanisms can be identified: rupture and erosion. Rupture results in clusters of fibers separating from the bundle. Erosion occurs when single fibers are removed from a bundle's edge. The onset of dispersion in both simple shear and squeezing flow experiments is a stochastic process.
Excimer lasers have been employed to modify the surfaces of a range of polymers to enhance adhesion. Considerable increases in joint strength were achieved as a result of laser treatment. Many lap shear joints, exposed to hot/wet environments, provided high retention of joint strength and durability. Laser-treated PEEK and APC-2 joints exposed at 50°C and 96%RH for several weeks, showed excellent resistance to ageing.
Stereolithography inserts shells for injection molding tools are filled in the backside, aiming to support high pressures and to improve the cooling efficiency on the mold. A common backfilling material used is an alloy of bismuth. However, there are other alternatives, such as tin, which has a higher thermal conductivity. This article discusses the pros" and "cons" to use tin as a backfill and investigates if it provides a better cooling condition improving mold's life."
Enhancement of fiber-matrix interaction for a jute-epoxy composite system was attempted by surface modification of the fibers. The surface modification of jute fibers was achieved using bi-functional amines, which were capable of bonding with both the fiber and the matrix. The changes in interface bonding were observed by measuring the flexure modulus of the composite samples.
Ethylene/alpha-olefin copolymer elastomers based on single site constrained geometry catalysts exhibit a number of physical properties that make them extremely useful for automotive interior applications. Due to the low level of unsaturation in these polymers, they exhibit outstanding heat and UV aging resistance. Their molecular structures enable these polymers to exhibit low glass transition temperatures (Tg). Thus, compositions containing these polymers exhibit very good low temperature impact properties. Furthermore, these products impart inherent flexibility and soft touch to compositions and eliminate the need for plasticizers. Ethylene/1-octene copolymers exhibit an optimum combination of ultimate tensile and low temperature properties. Ethylene/1-octene copolymers can be compounded to produce flexible TPO compositions with elevated temperature and desirable softness suitable for automotive interior applications.
Fly ash is a by-product of the ground coal burning process used in power generation plants. Since fly ash primarily consists of inorganic materials, it is a potential filler substitute for conventional fillers in the plastic industry. In this work, the mechanical, physical, and thermal properties of fly ash filled polypropylene were determined and the effect of adding fly ash on the properties of the resin was studied. Driven by the economical potential and environmental aspect of the usage of fly ash, this study enabled us to determine the viability of coal fly ash to be used as a substitute filler in plastic resins.
A new biological strategy has been developed to synthesize water-soluble conducting polyaniline. In this approach, anilines are polymerized by the enzyme horse-radish peroxidase (HRP) catalysis in aqueous buffer solution at pH 4.3 in the presence of a template. Strong acid polyelectrolytes such as polystyrene sulfonate (SPS) and the aqueous micelles formed by strong acid surfactants such as dodecylbenzenesulfonic acid (SDBS) are favor-able templates to form nano-scale reactors for the growth of conducting polyaniline. The properties of this enzymatically synthesized polyaniline are consistent with the polyaniline that is traditionally prepared via either chemical or electrochemical procedures. This biological approach offers unsurpassed ease of synthesis, processability, stability (electrical and chemical), and environmental compatibility.
The development of a reactive compounding process to provide an economical route for the production of film grade polylactic acid is discussed. The development of this process required the synchronization of a large number of unit operations. The unit operations were combined in a manner to optimize throughput and devolatilization, while minimizing gel formations and blocking. Free radical branching, plasticization, devolatilization, underwater pelletization and surface treatment techniques were employed during the development process. Process development was accomplished on a co-rotating, intermeshing twin screw extruder equipped with both devolatilization and underwater pelletizing systems.
Polymer engineering courses are now being taught in a variety of departments of numerous engineering schools all over the world. In many cases, a single introductory course is offered, sometimes shared by departments. A practically-oriented project, designed to alert the students to the strong interdisciplinary nature of the field and to prepare them for the type of work that many engineers do in this field, will be discussed in the light of over thirty years of experience in our school. The project can be integrated in an introductory polymer engineering course or, in an expanded form, made into a complementary course. The presentation will include the general objectives, as well as many practical considerations which are important to the success of such project or course.
The action of two differents organic peroxides at 290°C on the mechanical properties of linear low density polyethylene (LLDPE) viewing its application as internal pipeline coating was studied. When the amount of crosslinking agent increased on polyolefin it was observed that for both peroxides a decreasing of elastic modulus and stress at yield. The stress at break raised and the drop of elongation at break cocurred from 0,5% of peroxide.
In the synthesis of polyethylene, sodic mordenite and acid ZSM-5 zeolites were evaluated as support material for bis (cyclopentadienyl) zirconium dichloride catalyst system. The zeolites were calcinated at 300°C before treatment with methylaluminoxane (MAO) and Cp2ZrCl2. The supported catalyst systems were evaluated in terms of polymerization activities by varying the temperature of Cp2ZrCl2 impregnation on the support and the MAO and Cp2ZrCl2 concentrations.
A TPV based on a dynamically vulcanized blend of epoxidized natural rubber and polypropylene is described. Morphological and rheological properties are briefly reviewed. Basic physical properties compare well with those of other TPVs whilst oil resistance is comparable to that of a well-compounded NBR vulcanizate (34% acrylonitrile). Excellent heat resistance with good retention of properties on ageing for extended periods at 100° and 150°C is also demonstrated as is good weathering and ozone resistance.
The rheological properties of various TPV's have been studied in shear flow using dynamical mechanical spectrometry, capillary rheometry, transient stress buildup and shear creep. The TPV's which are commercial dynamically vulcanised PP/EPDM blends show a typical rheological behaviour with an apparent yield stress value at low shear rates, a shear-thinning viscosity at high(er) shear rates and, moreover, they do not obey the Cox-Merz law. This study revealed that the observed phenomena could be explained by the role of the three main components: PP, EPDM and oil.
A rugged new process rheometer employs a cam rotating in a cylindrical cavity containing a flush mounted pressure transducer. The cam generates excess hydrodynamic pressure in the wedge-shaped region between its outer edge and the cavity wall. As the cam passes the transducer, the measured pressure increases, reaches a maximum and then decreases. The amplitudes of the pressure fluctuations are proportional to viscosity. The shear rate of the viscosity measurement is the cam speed divided by the gap distance. The instrument continuously records and analyzes pressure versus time profiles. For dual shear rate measurements, two cams are keyed to an extruder screw or the shaft of a gear pump. For continuous shear rate sweeps, external variable speed drive motors can be used with side stream and reactor vessel versions. In-line and referee lab data are presented for typical polymers and rheometer configurations.
Polyolefins such as polypropylenes need to be stabilized effectively against UV radiation in order to have a useful product life. The use of hindered amine light stabilizers (HALS) in polypropylene fibers and molded articles has been gaining popularity. Specific applications include automotive bumpers, medical devices and polypropylene fibers for carpets. A novel method was developed to detect the presence of a hindered amine light stabilizer (HALS), based on silicon technology in polypropylene. The method consists of extracting the HALS from the polypropylene matrix followed by detection and quantification using proton NMR spectroscopy.
A theoretical method is proposed for optimum design of a crosshead annular die used for medical tubing. According to this method, the geometric variables are determined to minimize the change in gapwisely-averaged flow velocities due to the variation in flow patterns inside the transitional region of the flow channel of the die, namely the gum space. To achieve this, a numerical approach to flow analysis is put forward based upon the simplified motion and energy equations as well as the approximation of the flow channel using a series of varying annular slits, each having constant geometric parameters. Accordingly, the numerical schemes for flow analysis and design optimization are established, and the computer program is developed using Microsoft Visual C++ 6.0. For an optimum die design, the heat adhesion between the cold-fed inner tube and the hot melt during the over-extrusion is evaluated based upon the temperature rise and pressure profile of the melt in the die land. Based upon the optimum die design obtained from the method, the flow is well balanced with enhancement of extrusion quality. Also, it is found that the optimum die designs are less sensitive to extrusion conditions within a certain range.
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Brown, H. L. and Jones, D. H. 2016, May.
"Insert title of paper here in quotes,"
ANTEC 2016 - Indianapolis, Indiana, USA May 23-25, 2016. [On-line].
Society of Plastics Engineers
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