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 Chaotic Mixing on Catalyzed Thermoplastic Polyurethane Polymerization
We investigated the effects of catalyst concentration on chemical reactions at the interfaces between the diisocyanates and diols in a bulk polymerization system where self-similar mixing microstructures were produced by chaotic mixing. It was observed that chaotic mixing conditions exerted strongest influence when the time scale of mixing and the time scale of chemical reactions were of comparable magnitude. For example, at moderate catalyst concentrations, the chemical reactions in the chaotic mixer occurred much faster than in a conventional mixer, such as in the mixing chamber formed by the kneading block elements of twin-screw extruders. It was found that chaotic mixing had almost no influence on conversion at lower catalyst concentrations.
Structure-Property Relations in Visbroken (Peroxide Treated) Impact Polypropylene Copolymers
Impact polypropylene (PP) copolymer (reactor blend) or a postreactor blend of PP and ethylene-propylene rubber (EPR), is an immisible two-phase system consisting of PP as a matrix and EPR as a dispersed phase. When the amount and the molecular weight of EPR in such a blend exceed certain limits, then visbreaking of such a blend leads to an unusual melt rheological behavior – namely, a viscosity up-turn at low frequencies as seen in the dynamic measurements of the molten polymer. We attribute this unusual behavior to the formation of an “interacting network structure” between the two immisible phases via grafted molecules created during the visbreaking process.This melt network structure is carried over into the solid state as evidenced from the optical micrographs of the isothermally crystallized samples. The control of this network structure is important because it affects such properties as stiffness, impact strength and bruise resistance. This paper describes the relation between the extent of viscosity up-turn with the impact resistance and flex modulus of the injection molded samples.
Processability and Film Performance of Single Site Bimodal sLLDPE Resins
Fractional Melt Index (MI) linear low-density polyethylene (LLDPE) resins are used in the polymer extrusion industry to manufacture films. These fractional MI resins provide excellent melt strength for bubble stability on high throughput lines as well as excellent film physical properties. Until now, most fractional MI film resins were made using Ziegler-Natta type multi-site catalysts producing unimodal MWDs. With the advent of single site dual reactor process technologies, it is now possible to produce single site bimodal sLLDPE resins. This paper will discuss the effects of molecular architecture and film processing conditions on the performance characteristics of films made from fractional MI, single site bimodal resins.
Numerical and Photoelastic Research on Residual Stress/Warpage of PC Plank
The clear plastic injection-molded parts are extensively employed in optical, optoelectronic and electronic applications. But the molded residual stress can deteriorate the optical properties of the final product. In this research, the distribution of residual stress of the transparent molded polycarbonate plank with 6.5mm thick have been inspected firstly under polarized light to understand effects of flow-induced and thermal-induced stresses and their interaction. Then based on optical experiment results of photo-elasticity, thermal-induced residual stress of different mold cooling conditions was investigated by numerical methods. A series of multicolored band or fringed pattern and simulation results showed the effect of non-uniform temperature distribution was the main cause of residual stresses/warpage of thick parts. In-molded constrain and mold deformation effects on parts warpage were also discussed by numerical method.
Preform Node Optimization for Injection Molding Warpage Analysis
Currently, warpage analysis of CAE injection molding simulation software is considered as static structural problems, and seldom uses node optimum technology. For mesh is combined with beam, bar (1D), triangular element (2D) and even tetrahedral element (3D), the quantity and quality of meshed elements & nodes affect the accuracy and run time of engineering simulation greatly. In this paper, by classifying the features of nodes and elements for the computing model, the regulars for permutation nodes used by FEM (Finite Element Methods) have been used. With the new order of the node in FEM, the bandwidth of matrix can reduce; also the efficiency of calculating is improved. Several numerical model have been renumbered the node label and reordered with arbitrary input sequence, then create optimal bandwidth for the network system, which shows the method in the paper is valid.
Extrusion Rheology of Glass-Fiber-Filled Polypropylene Melts
The advantages of glass-reinforced plastics in various branches of the industry such as automotive and aircraft industries, and also in the manufacturing of furniture and sports goods are well-known. In all these applications knowledge of the melt flow of the composite material is required, in order to design machinery for processing the filled polymer. This paper is a contribution to the quantitative description of the rheology of glass-fiber-filled polypropylene melts. The effect of shear rate, melt temperature and fiber concentration on the melt viscosity have been studied by means of a high-pressure capillary rheometer. A novel equation has been presented to correlate the melt viscosity with the fiber content, using a modified shift factor taking the melt temperature and the fiber content into account. The proposed modeling can be applied to any filled thermoplastic melt.
Asia Tooling and Molding: How to be Successful
Today companies are faced with the reality that they must investigate global sources. Doing business in Asia for American tool shops and molders has changed from a curiosity to necessity for many companies. Understanding, locating, and working through the maze & complexity of dealing with a foreign company can be intimidating. Comprehending the differences of mold construction standards in Asia vs. the U.S. is critical to being successful. There are different considerations if the mold will be used in Asia or shipped to the U.S to be run. It is important to know how to communicate effectively and what your expectations should be. This presentation will take you through how to avoid pitfalls and do the research necessary to be successful in Asia, which will put money on the bottom line.
A Radically New UV Stabilizer for Flexible PVC Roofing Membranes
Ultraviolet absorbers such as those from the hydroxyphenylbenzotriazole and hydroxybenzophenone class of compounds are typically added to flexible PVC roofing membranes to protect the membranes during long term exposure to sunlight. In this paper a radically new UV stabilizer, one that is not just another UV absorber is introduced. This new UV stabilizer was found to dramatically increase the weatherability of PVC roofing membranes. The new light stabilizer’s performance was documented and compared to traditional PVC membranes containing just a UV absorber. Although the paper focuses on PVC roofing membranes, examples were provided of other durable applications that could benefit from the new light stabilizer technology.
Empirical Evaluation of Different Groove Feed Screw Geometries
Plasticization rates can be greatly increased with the use of grooved feed extrusion. Grooved feed extruders can be used in a wide range of extrusion processes for higher output rates. This technology has doubled plasticization rates for some resins and processes as compared to smooth bore extruders.This paper will compare the performance of three different screw geometries while processing fractional melt HDPE. One of the main methods of evaluation will be the comparison of internal pressure profiles over the entire length of the screw at eleven different locations down the length of the barrel at two L/D apart.
Color Mixing in Single Screw Extruder: Simulation & Experimental Validation
We present numerical simulations for an ABS resin extrusion in an industrial conventional single screw extruder. Based upon the flow field patterns obtained in the simulations, a particle tracking procedure was employed to obtain information about the spatial distribution of particle tracers of two colors. Results of the simulation were compared with experimental data obtained under similar extrusion conditions. To evaluate the degree of color mixing and color homogeneity for the system, we employ a specific index calculated based upon the Shannon entropy for two species populations.
Development of Silver Metallic Co-Extruded Plastic Films
Although (Al) flakes are commonly used in paint applications to achieve silver metallic appearance (high lightness and high flop), they are not capable of producing similar results in co-extruded plastic films. It was shown that Al flakes are folded and/or crimpled during melt processing. As a result, the flakes lost their flat morphology that is essential to achieve good orientation and high flop. It was demonstrated that high lightness and high flop can be achieved by using “reinforced” Al flakes. It was also shown that TiO2 coated mica flakes remain flat morphology during melt processing. By understanding optical interference, additive color mixing, and light management, co-extruded polycarbonate films with high lightness and high flop close to automotive paint have been made.
Biconstituent Fiber Spinning Modeling by Using Phan Thien– Tanner Multimode Constitutive Equation
A one-dimensional model (1) for fiber spinning simulation was developed based on traditional transport phenomena equations, a Phan Thien–Tanner multimode viscoelastic model and a crystallization kinetic model.In order to solve the coupled system of differential equations a finite difference scheme and a Crank-Nicholson solution algorithm were implemented. The results of simulations were validated using data from other researchers and our experimental data from fiber spinning of Polypropylene and biconstituent fibers of Polypropylene and Polyamide 6.
Influence of Cavity Materials on the Cooling Time of Molding
The laws for optimal heat exchange in molds for injection molding of thermoplastic melts have been known for a relatively long time, more than 30 years. But from time to time we can read and hear that someone has achieved shortening of the cycle time and hence the cooling time of molding also by two-digit percentages. Based on the general equation of the cooling time of molding, for the necessary quality of molding, thus for the given process parameters (melt and cavity temperature), properties of thermoplastic melt (deflection temperature under load, thermal diffusivity) and geometry of molding the cooling time is constant. The only way to reduce the cooling time and thus the cycle time as well is the choice of proper materials for mold parts forming the cavity. Materials with low thermal properties offer great opportunity for shortening the cooling time, but their advantage is restricted to relatively small parts.
The Proposal for Classification of Injection Molding Procedures
During our investigations of the state of the art of injection molding of materials and substances we found out that there are at least 235 procedures which can be classified as injection molding of the living and the nonliving. The aim of this study is also to present these procedures in a logical order. We use two systems of codes. The aim of the first code (31 digits) is only for the proper classification of procedures into the main groups. The second one is a code with 7 digits which are for practical use. We made this description by dividing the necessary criteria into 5 main groups. The basic criterion is the injection pressure. Full description of all the 235 procedures demands an international cooperative project, which must unify the academia and the industry.
Thermoplastic Polyurethane Nanocomposites of Reactive Silicate Clays
End-tethered thermoplastic polyurethane-clay nanocomposites were prepared by bulk polymerization method; polyether and polyester polyols of molecular weight 2000 were used to form the soft segments by allowing reactions between the isocyanate groups in chain extended polymers and the hydroxyl groups in organic modifier. The mechanical and thermal properties of the resulting composites were investigated to study the effects of clay content and the nature of polyol. Composites based on polyester polyol showed better nanoclay dispersion and much improved mechanical properties. Up to 78% increase in tensile modulus, 125% increase in tensile strength, and 100% increase in elongation at break were observed with polyester polyol based nanocomposites at 5 wt% clay loading.
Application of CAE Technique in Process Optimization and Part Quality Control of Injection Molding
In injection molding, many factors affect the molding process and the final quality of the products. The production problems on materials properties, design of products, and design of molds can be solved with the help of CAE systems, but it is still relied on the experience of the operator concerning the process setup and parts quality control. In this paper, application of CAE technique in studies of relationships between process parameters and quality indexes of the part, process modeling, process parameters optimization and part quality control are introduced systemically.
Nanocomposite Systems Based on Unsaturated-Polyester and Organo-Clay: A Fundamental Approach
Unsaturated-polyester (UP) resins are bicomponent systems comprising an UP alkyd, usually dissolved in styrene monomer. This gives rise to numerous possible approaches in synthesizing UP nanocomposites. UP-resin/organo-clay nanocomposites and UP-alkyd/organo-clay nanocomposites were investigated. The effects of various mixing processes and parameters, using several organically modified clay types were studied. This methodological approach provides a basis for understanding the structuring processes involving the formation of the UP/clay nanocomposites and establishing materials-processingstructure interrelations.
Comparative Deformational Characteristics of SEBS Thermoplastic Elastomers and Vulcanized Natural Rubber
Three Poly (styrene-b-ethylene-co-butylene-bstyrene) (SEBS) thermoplastic elastomers (TPEs) are studied mechanically and compared to cross-linked natural rubber system. It is observed that subtle alterations in the mid-block of the TPEs affect the mechanical properties significantly. The stress relaxation at room temperature is reduced in systems where the ratio of ethylene to butylene segments in the mid-block is greater than one. The cyclic behavior of these systems also shows significant elastic hysteresis. Differential Scanning Calorimetry suggests that these TPEs crystallize at low temperatures, similar to the observed behavior in a vulcanized natural rubber. Simultaneous WAXD/SAXS measurements on a deformed sample highlight deformation at the nanometer and the molecular length scales. In-situ WAXD at different strains also provides evidence for strain-induced crystallization occurring in the selected systems. Strain-induced crystallization in these TPEs accounts for the retention of their highly elastic behavior. Results from Deformation Calorimetry further reinforce the evidence for strain-induced crystallization in certain systems.
Production of Conductive Multiphase Polymer Systems via Selective Localization of Carbon Black under Chaotic Mixing Conditions
Selective localization of conductive fillers such as carbon black (CB) in multiphase polymer system was exploited to reduce the percolation threshold and to obtain conductive composites. Polypropylene (PP) filled carbon black compound was mixed with polyamide 6 in a chaotic mixer. Double percolating fibers of PP/CB compounds were responsible for conductivity of the blend at low mixing strains. At higher strains, the PP fibrils, containing carbon black, formed droplets. However, the conductivity was not compromised due to selective localization of carbon black particles at or near the interfaces of the closely spaced PP droplets. At even higher strains, the blend turned into insulator as the PP-droplets distributed more uniformly in the blend and carbon black particles migrated to the interface of PP and PA6-phase.
On the Three-Dimensional Modeling of Polymer Processes
The accurate modeling of polymer processes for prediction or design purposes requires many considerations. These include defining the problem, determining the necessary physics the model should include, determining the equations needed to be solved, determining the rheological parameters important in the particular problem being solved, running rheology experiments to determine these parameters, deciding on the best" rheological model to represent the rheological data creating a 3-D representation of the flow domain volume on which the equations are to be solved determining and specifying all necessary boundary conditions obtaining or writing a 3-D flow code which incorporates all the preceding information running the program and finally determining and displaying the output data for which the modeling process was performed. Each of these considerations is discussed to some extent in this paper."
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