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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Effect of Nanosilica on Properties of Segmented Polyurethanes
Thermoplastic polyurethane elastomers having soft segment concentration (SSC) of 50% and 70% were synthesized in the presence of 12 nm silica nanoparticles. The concentration of nanosilica was varied from 0% to 30% in both series. Nanosilica had not significant effect on glass transition of the soft segment but it increased tensile strength and particularly elongation at break. Tear strength of the series with 70% SSC was not affected by the presence of nanosilica while initial decrease was observed in the series with 50% SSC.
Structure-Property Characteristics of Ethylene/1-Hexene Copolymers with Tailored Short Chain Branching Distributions
Recently, we have developed a metallocene catalyst system that can produce polyethylene and ethylene/a-olefin copolymers with tailored molecular weight and short chain branching distributions. Ethylene/?-hexene copolymers produced with this system have narrow molecular weight distributions as expected from metallocene catalysts. However, these copolymers are quite unique in that their short chain branching distributions are broad and sometimes bimodal, similar to Ziegler-Natta LLDPE. To examine the effect of these broad short chain branching distributions on the polymer properties, tensile and viscosity characteristics were measured. It was found that the tensile properties of these broad distributions could be controlled by the relative amounts of each species. In this study, the best tensile properties were achieved with a distribution that contained a large proportion of crystalline material and a small fraction of lower crystalline material. It was also found that the distribution of short chain branches can have an effect on the viscosity behaviour of these copolymers.
Superstructures in Polyamide Elastomers-The Key for Super Performance?
Polyether block amides are known as thermoplastic elastomers with excellent chemical resistance, outstanding physical properties, and easy processing. This is closely related to the type of chosen polyamide blocks and the morphology of crystalline and amorphous phases. In contrast to other multiblock thermoplastic elastomers which are forming only net points of crystallized polyamide blocks polyether block amides exhibit a spherolithic superstructure of crystallized lamellae. As a consequence there is an intrinsically reinforcing effect in the material depending on block composition which is reflected by a unique mechanical behavior which will be discussed in the paper.
HDPE Blending Technology for Enhanced LDPE Film Properties
Numerous blown film applications involve the blending of high density polyethylene (HDPE) with low density polyethylene (LDPE) to achieve desired physical properties. For example, HDPE blended with LDPE provides greater stiffness and holding power for product retention in shrink films. HDPE/LDPE blends are also used in sanitary paper packaging applications, with the HDPE component providing needed stiffness for high speed machinability. Likewise, a variety of other packaging applications utilize HDPE/LDPE blends for improved machinability, especially as downgauging opportunities are pursued. This paper documents the effect of HDPE resin choice and content on the strength, optical and shrink properties of LDPE/HDPE blown films.
The Hydraulic Permeability of Dual Porosity Fibrous Preforms
We present a computational analysis of viscous flow through arrays of fiber bundles using the Boundary Element Method (BEM) implemented on a multi-processor computer. Up to 700 individual fibers are included in each simulation. These are simple but not trivial models for fibrous preforms used in composites manufacturing - dual porosity systems characterized by different inter- and intra-tow porosities. The way these porosities affect the hydraulic permeability of a preform is currently unknown and is elucidated through our simulations. Numerical results are compared to analytical models. Through a large number of simulations we construct a master curve for the permeability of arrays of fiber bundles for various packing arrangements.
Minimizing Sandwich-Panel Warpage
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.
Induction-Assisted Bonding of Elevated Temperature Curing Adhesive Systems
Performance of elevated temperature curing adhesives by induction heating and bonding is studied. Adhesives with 250 F and 350F cure temperatures were studied with woven carbon/epoxy and glass/vinyl ester substrate material. The ability of the carbon-epoxy system to heat by induction was used to compare performance of induction bonding with autoclave baselines, without the aid of susceptor material. Lap shear tests indicate no loss in performance by induction bonding, compared to autoclave baselines, in all cases studied.
Effect of Water Sorption on Mechanical Properties of Fiber Reinforced Dental Resin
Composites from different glass fibers reinforced in dimethacrylate based dental resins were prepared for flexural tests in accordance with ISO 10477. Tests were conducted on both dry specimens and on specimens stored in water for 7 days at 37°C. Depending on type and amount of fibers, the strengths were found to decrease from moderate to minor. Loss of strengths correlated with the constituents of fibers.
Wasteless Distribution Medium: A New Development for the Resin Infusion Process
The typical resin infusion processes like SCRIMP (Seemann Composite Resin Infusion Molding Process) require the use of a distribution medium or system to increase the impregnation speed in large parts. Normally, a substantial amount of surplus resin remains in the distribution medium and has to be disposed with the medium or remains on the part as resin rich domains. A new patented type of resin infusion process is presented, which does not produce any surplus resin waste.
Welding of Polymers Using a Diode Laser
Welding polymers by using a diode laser is a fairly new joining method. The first industrial application is the joining of automotive keys. The process advantages are precisely defined heated zones, minimized melt flow and the realization of three dimensional weld lines. At the IKV a process analysis has been done and the influence of pigments on the weld strength has been investigated. It is possible to weld glass fibre reinforced polyamide, which is transparent for the laser beam, but appears black to the human eye.
Non-Isothermal, Non-Newtonian Analysis of Three Dimensional RTM/VARTM Processes Using HP-Adaptive Finite Element Method
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.
Mechanochemical Alteration of Ethylene Copolymers via Solid-State Shear Pulverization (S3P)
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.
Investigation of the Mechanisms by Which Glass Fibers Disperse in a Polystyrene Matrix
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.
Ethylene/?-Olefin Elastomer Based Compositions for Automotive Interior Applications
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.
Utilisation of Fly Ash as a Filler in Plastics
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.
Biologically Derived Conducting Plastics
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.
Elastomer Matrix Composites for Impact-Resistant Parts
The impact resistance and energy absorption capacity of most thermoset matrix composites is rather low. Use of elastomer matrix can improve the impact behavior, allowing the design of impact-resistant parts (e.g. crash elements). By using low-viscosity elastomer systems, composite parts can be produced on a commercial filament winding machine. Mechanical tests of filament wound samples show that elastomer matrix composites exhibit superior energy absorption behavior and offer a high optimization potential for impact-loaded composite parts.
Characterization of Multi-Layer Permeation Barriers Made by Microwave Plasma Polymerization
Plasma polymerization is a suitable process to deposit high quality permeation barrier coatings on plastics substrates. The process allows to stack several layers forming multi-layer coatings. In these studies, the permeation properties of single- and multi-layer coatings made by plasma polymerization are investigated. As a result, the oxygen transmission through multi-layers does not only depend on the structures of the single layers. Also, the arrangement of the layers shows great effect on the permeation properties.
Development of a Reactive Extrusion Process for the Production of Plasticized Film Grade Polylactic Acid
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.
Product Fabrication Project/Course
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.
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