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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Reactor TPO: Innovations in Low Temperature Ductility and At-Press Dimensional Control
Material specifications for exterior TPO applications require materials which are highly ductile at temperatures as low as - 40°C. Practical impact tests such as pendulum impact on large part moldings, are simulated by multi-axial impact tests according to ISO 6603 or ASTMD3763 standards. In such tests, molded discs with a prescribed thickness (2-3 mm) are impacted at low temperatures (0 to -40°C) and impact speeds (2 to 7 m/s). Injection molded 3 mm thick discs from compounded TPOs using ethylene –? olefin copolymer elastomers are known to have total energy absorption of > 60 Joules and fail in ductile manner down to -40°C. A compounded TPO must use a particular PP, and 30-35% added elastomer to obtain such ductile performance. Thus, manufacturing complexity and an additional heat history had to be added via compounding to meet these specifications.In response, Dow R&D has developed a natural reactor TPO (product name Dow PP D143.00) which is fully ductile at - 40°C. This performance is the result of a product design based on specific elastomer design and MWD distribution while still being produced in the reactor. The resulting flexural modulus is greater than 900 MPa and coefficients of linear thermal expansion (CLTE) = 90-100?m/m·°C. This reactor TPO will meet the functional requirements for many bumper fascia designs. In cases where higher modulus and/or lower CLTE is required, talc filled master-batches are developed to allow easy dispersion within an injection molding press.
A Method for Quantifying Relative Interfacial Shear Stress in Mwnt/Polymer Composites
In order to better understand the micromechanical behavior of carbon nanotube filled polymers, the load transfer behavior and interfacial shear stress must be quantified. This paper presents preliminary work on an experimental technique for quantifying the relative interfacial shear stress in multi-walled carbon nanotube / polycarbonate composites. The procedure provides a comparison of the aspect ratio of the nanotubes pulled from a fracture surface. In addition, the correlation with pullout angle is discussed. This work showed a decrease in the aspect ratio and thus an increase in interfacial shear as a result of chemical surface modification to multiwall nanotubes.
A Durability and Adhesion Test for Fabric Covered Plastic Parts
The cross-cut adhesion test provides a rating for the adhesion of a surface material to a plastic substrate. The original ASTM standard D3359-02 for the cross-cut adhesion test was developed to measure the adhesion between thin paint films and flat, metal substrates. This test, however, is not well suited for three dimensional plastic parts that are covered with fabric. It will be shown in this study that improper cross-cut testing protocol can result in false failures and artificially low adhesion performance scores. A modified cross-cut adhesion test procedure is documented here that is based on the ASTM method and is applicable to fabric covered parts.
Effect of Screw Type on Development of Polymer Blend Morphology along an Extruder during Compounding
The morphology development of an immiscible polymer blend along a single screw extruder was investigated experimentally. Three different screw geometries were evaluated: one with conventional screw elements; the other two with a fluted and Pineapple mixing element, respectively. The experiments were conducted using a polypropylene/polyamide-6 (PP/PA6) blend. The samples of blends were collected from four different positions using specially designed sampling device along the extruder online during compounding and were then examined using scanning electron microscopy (SEM) to evaluate the morphology development. The results showed that the screw with a fluted mixing element appears to produce the finest morphology at the end of the extruder. The Pineapple mixing element, with a characteristic of chaotic mixing, facilitates to form thinner laminar layers of dispersed phase.
Hybrid Nanoclay-Rigid PVC-Wood-Flour Composites
This study examined the use of nanoclay reinforced rigid PVC prepared with a novel melt-blending approach as a matrix for PVC/wood-flour composites. The effects of nanoclay contents and chitin as coupling agent on the properties of the composites were evaluated. The flexural, tensile and dynamic mechanical properties of composites made with nanoclay reinforced PVC matrix and chitin were measured and compared to their counterparts made with unreinforced PVC matrix. The experimental results indicate that wood-plastic composites with properties similar to solid wood could be manufactured by tailoring the formulation, i.e., combining nanoclay, rigid PVC, wood flour, and coupling agent.
Micro-Injection Molding of High Aspect Ratio Features with Thermoplastic Polyurethanes
High aspect ratio (4:1) microscale features were injection molded using thermoplastic polyurethanes and silicon tooling and measured using atomic force and scanning electron microscopy. Direct filling of the features enhanced replication when compared to indirect filling (i.e., filling during melt pressurization). With direct filling, mold temperature and melt temperature equally impacted replication. For good replication, mold temperatures must selected to balance filling, stretching of molded features during ejection, and shrinkage of the features.
Chemiluminescence and Fluorescence Imaging of Virgin and Reprocessed Grades of Nylon 6,6 and Polycarbonate
Chemiluminescence and Fluorescence Imaging can be used as novel quality control techniques applied to reprocessed resins. Chemiluminescence measurements of Nylon 6,6 in both air and nitrogen atmosphere reveal increased sample oxidation with increased number of molding cycle. Fluorescence imaging of reprocessed polycarbonate pellets compared to virgin shows significantly greater intensity from reprocessed resins. GPC and Raman Spectroscopy confirm disorder in reprocessed resins. Both Chemiluminescence and Fluorescence imaging techniques performed in combination yield information related to sample morphology and contamination. By careful selection of excitation and emission filters, Fluorescence imaging can discern regrind amounts in plastics to better than 5% resolution.
Effect of Cell Shape on Mechanical Properties of Polyurethane Foams Molded under Several Conditions
Polyurethane foam is formed by various molds. The internal structure of rigid polyurethane foam is very complex. Moreover, the cell shape showes elongated shape in foaming direction, so that rigid polyurethane foams exhibit anisotropy in mechanical properties. Therefore, the effect of cell shape on the mechanical properties of polyurethane foams have been investigated on various molded condition and different mold shapes. The cell shape was evaluated by the ratio of the longitudinal diameter to the transverse diameter . The relationship among density, cell shape and compressive properties of many kinds of rigid polyurethane foams were investigated. It was found that compressive properties depended on cell shape in compared with density.
Effect of the Clay Treatment on Cure and Morphology of Epoxypolysulfone- Montmorillonite Hybrid Nanocomposites
The effect of the addition of two different organically treated clays montmorillonite on the cure and morphology of an epoxy-polysulfone (PSF) blend (5, 10 and 15 phr PSF) is studied. The epoxy system was based on diglycidyl ether of bisphenol A and diaminodiphenylsulfone. The clays used were Nanomer I.30E (NI30E) and Cloisite 15A (C15A). The curing reaction was followed by differential scanning calorimetry and the morphology was analyzed by scanning electron microscopy. The presence of NI30E accelerates the curing reaction, decreases the glass transition temperature (Tg) and increases the PSF domain size. On the other hand, there is a negligible change on the curing reaction and blend morphology for C15A modified systems.
Designing Sustainable Products Using Bio-Based Nanocomposites
Environmental materials-related factors can be best addressed in the design stage. Conversion of materials to products is critically important in dealing with new and partly unknown challenges and opportunities. Experiments to explore bio-based nanocomposites included investigating injection molding processability and product properties. Several nanocompounds with modified poly(lactic acid) were prepared and geometries were molded with typical product characteristics, including flow weld lines. Further molding optimization is needed, preferably in conjunction with new mold design principles and dedicated molding machines.
The Effects of Secondary Angle Length and Thickness on Pinchoff Strength
A properly designed pinch-off can mean the difference between a strong or weak weld in extrusion blow molding. There are few guidelines to use as when designing the pinch-off of a mold. The pinch-off area of a blow molded part is usually the weakest area the part. It is important to look at what affects the strength of the weld line in order to maximize the strength of the bottle. This experiment studies the effects of changing the depth and length in a compression type pinch-off of the compression region of the flash pocket while keeping the other dimensions of the insert constant. This will help mold designers in the future by giving them some guidelines when designing this part of the flash pocket. The results obtained from this experiment show that generally when the compression pocket length increases and compression thickness decreases, the weld strength increases. Some of the results were inaccurate, and the experiment needs to be run again with better dimensional control over the inserts.
New Polyurethanic Materials Derived from Dibenzyl Monomers: Elastomers, Films and Blends
New segmented polyurethanes have been designed and synthesized based on flexible DBDI (4,4’-dibenzyl diisocyanate) with internal –C-C- rotation axis. PUs structural and mechanical properties were investigated. DBDI giving rise to a special hard segment conformational mobility induces a specific physicalmechanical behaviour in PU and leads to a high tendency of crystallization and hard segment block phase separations in dibenzyl–based PU. The preliminary results of the structural study on such polymers have shown significant changes which are brought about by changing the geometry of the isocyanate.
Fabrication of Porous PCL Fiber with Co-Continuous and Size Adjustable Porous Structures from Immiscible Polymer Blends
Porous polymer fibers can be fabricated using different methods including hollow fiber extrusion, multicomponent fiber extrusion (e.g. with islands-in-sea morphology), and solution processing. However, with the current technology, it is difficult to achieve a continuous porous structure across the entire fiber cross-section and control the pore size. This greatly limits potential applications of such fibers in many emerging biochemical and biomedical applications. We report here a filament extrusion process of immiscible polymer blends for fabrication of highly porous fibers with continuous and size adjustable porous structures.
Predicting Shelf Life of Medical Grade Polymers Using Accelerated Heat Aging
Part failure after radiation sterilization in medical parts is a concern in the plastics industry. When the sterilization phase is complete damage to the part does not cease, but continues in a dark reaction for a period of time, often years.Damage can be noticed when melt flow index tests are performed and the reduction in molecular weight causes a higher melt flow value. Also, damage can be noticed when tensile tests are performed and decreases in ultimate elongation are noticed. The intention of this research is to derive a new Q10 constant for the Arrhenius Equation to better predict shelf life of medical polymers.Conclusions will be drawn by comparing results from the tensile and melt flow index tests.
The Effects of Shear Imbalances on Intra-Cavity Melt Flow Using Varying Melt Flow Rates in Thermoplastic Elastomers and Vulcanizates
The high shear developed in a runner creates significant melt variations and is the source of shear induced mold filling imbalances in geometrically balanced runner runners. These same shear induced melt variations can also create unexpected filling patterns in a single cavity mold. If this uneven filling pattern could be manipulated then shear induced melt variations can be used as a tool in industry. The focus of this paper is to find if the filling pattern with thermoplastic elastomers (TPE) and thermoplastic vulcanizates (TPV) can be manipulated by varying injection flow rate.
Analysis of the Relative Effects of Loading Agents and Their Interactions as a Function of Core Resistivity in Thermoset Polyurethane Foam Parts
While there has been an increase in the use of certain polymers for electrically conductive applications , thermoset polyurethane foams have been primarily used in applications that do not require any electrical conductivity. The electrically insulative properties of these materials can be accentuated by the presence of air pockets inside of the foam parts . This investigation analyzes the effect loading agents have on electrical conductivity on thermoset polyurethane foam containing a conductive core. This paper discusses the relative effects of two loading agents – carbon black and graphite – on resistivity of a thermoset urethane part containing a conductive core as determined by statistical analysis through designed experiments.
Predicting Processing Parameters for Water-Assisted Injection Molding Based on Inverse GA-LMBP Neural Network
The water-assisted injection molding (WAIM) is a new injection molding technique. It is difficult to describe the WAIM process using mathematical method due to its complexity. In this work, a predicting model for the WAIM process was developed via an inverse hybrid algorithm combining genetic algorithm (GA) with Levenberg-Marquardt back propagation (LMBP) neural network. By adopting the model, processing parameters, such as melt temperature, water pressure, water injection delay time, and short-shot size, can be predicted quickly and accurately for desired residual wall thickness of molded parts.
Selection of Colorants and Other Additives for Durable Products
Polyolefins are utilized frequently in durable products that call for extended life in a variety of environmental conditions. Many of these products require color and almost all require and enhanced degree of resistance to the stresses of an exterior environment. The selection of plastic colorants that can withstand harsh environmental conditions is critical to ensuring the long term appearance of a polyolefin based durable product. Likewise, the correct choice of plastic additives for exterior applications must be made in order to ensure acceptable product appearance and performance over time.This paper examines key design considerations for durable polyolefin products in terms of additive selection. Special consideration is made in terms of selecting colorants that are considered non-toxic. A practical example is presented.
Appraisement of the Engineering Properties of the Chemical Resistant Laminate in Products
Polymer composites on epoxy vinyl ester resins serve the needs of wide range of industrial chemical processes with the final products, such as coverings, coverings of floors, etc.To provide a good corrosion barrier over concrete, metal etc, it is necessary to use a chemical resistant laminate (CRL). The practice of FRP application shows the existence of an optimum ratio between numbers of powder bonded chopped strand mat layers and engineering properties of CRL.Analyses of scale (size) effect of strength and permeability are carried out.The analytical dependence of tensile strength and permeability from a thickness is used for appraisement of the engineering properties of CRL in products.
New Transparent Copolycarbonate Compositions with Low OSU Heat Release Values
New polyester carbonate copolymers afford the first resins with low color, high transmission and low haze combined with low OSU Heat Release values. In addition, the fabricated articles can be hard coated to provide improved levels of scratch resistance. These compositions can be varied to maximize the various mechanical properties depending on the needs of the application. The excellent clarity combined with OSU 65/65 compliance allow for applications such as interior transportation windows/dust covers, partitions, mirrors and lighting lenses. The excellent colorability also allows for the fabrication of interior opaque components for the transportation industry.
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