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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The Performance of Polyvinyl Chloride / Thermoplastic Polyurethane Blends
Two grades of thermoplastic polyurethane (TPU), one polyester and one polyether based, were blended with two grades of PVC with different K-values of 56 and 71. Mechanical analysis showed that impact strength and elongation at break improved significantly, and the tensile and flexural modulus decreased with progressive increase in TPU content. DMTA results suggested partial miscibility between the two polymers. The performance of the blends was shown to be more dependent on the PVC/TPU percentage content rather than the PVC or TPU type.
Steel Wire Reinforced Plastic Composite Pipe
Steel wire reinforced polyethylene composite pipelines are a new technology product. The system is used for transport of oil, water, gas, and chemicals. This paper explains its new design concepts including micro-mechanics of load sharing and stress transfer. Recent test results will be reported to bring out its advantages over common plastic pipe and steel pipe.
The Effects of High Stress and Material Constraint on the Fracture Appearance of a Polyethylene Liner Pipe
This study involves a failure analysis on polyethylene liner pipes that had been installed as a corrosion protection liner in a high-pressure steel pipeline, operated at pressures up to 1500 psig. The peculiar fracture surface features are attributed to the stresses applied in service and to the geometry of the host pipe. The field failure times correlated extremely well with the published stress-rupture performance of the material.
POLYTRAC© Full Traceability in PE Valve Manufacturing
The Who, What, When and Where of every manufacturing process is critical to the longterm performance of polyethylene (PE) valves in natural gas distribution service. To obtain and archive this knowledge about every process, Kerotest developed POLYTRAC©, a full forward and backward traceability program for the POLYBALL™ line of PE ball valves. With full traceability, one has the maximum assurance that all manufacturing processes are under control and the highest quality valve is being produced.
Modeling of Mixers for Polymer Processing
The heat transfer in a batch mixer was studied using experiments and simulation. The mechanical torque was measured experimentally. The dissipated power was calculated and compared with the simulation. The heat transfer coefficient from experiment was calculate by a lumped approximation and compared with the data from simulation. The transient temperature profiles were obtained and the temperature distributions in the nip between rotors and barrel wall were shown.
Numerical Analysis of Cable and Wire Coating: Interactions between Material Rheology, Flow Domain and Process Conditions
Wire coating, based on the drag flow is a well-known process in the cable, wire or fibre-optic industry. It has been studied extensively in experimental and computational form over recent years. During the coating a polymer melt flows through an annular converging die and then meets a wire or cable that is usually traveling at high speed. This study is concerned with the numerical simulation of the complex flows that arise in the coating system with a thermoplastic polymer. The simulation study was performed in order to better understand the influence of the rheology parameters, the chosen processing conditions and the coating die geometry dimensions.
Measurement of Interfacial Instabilities during Coextrusion of LDPEs in Flat-Dies
This paper presents the results of some coextrusion flow studies for flat film on feed-block and multi-manifold flat dies for well characterised LDPE resins. The aim is to gain a better understanding of interfacial instability phenomena. The LDPE resins included materials of high and low viscosity as well as broad and narrow molecular weight distribution. The experiments involve the coextrusion of either the same materials in both layers or various combinations of materials with different viscosities. The focus of the work was to evaluate the effects of flow rate, viscosity and other material characteristics on the interfacial instabilities. The results from these experiments showed a possibility to locate areas where low or high frequency instabilities were created.
Compensating for Die Swell in the Design of Profile Dies
Because of the effects of die swell, the final shape of an extrudate is often substantially different from that of the exit opening of the die. As a result, the design of profile dies producing complex shapes often involves more than just “balancing” the die but also compensating for the effects of die swell. Typically, a successful design of such dies is only achieved through much “cut and try”. However, with the use of a fully three-dimensional finite element flow algorithm along with quick mesh generating capabilities, the usual cut and try involved in the design of many profile dies can be greatly reduced if not eliminated.This paper demonstrates how the effects of die swell can be compensated for in the design of profile dies. For profiles with one plane of symmetry, this includes compensating for the sideways translation of the extrudate as well as the change in shape that the extrudate experiences. Completely asymmetric profiles undergo a “twisting” downstream of the die. This twisting, which appears not to have been reported in the literature (at least for isothermal extrusion) is also accounted for here along with the change in shape that the extrudate undergoes.
Real-Time Estimation of Crystallization Half Time during Blown Film Extrusion and its Influence on Final Film Properties
The development of crystallinity during film blowing of a linear low-density polyethylene at different processing conditions has been investigated using online Raman spectroscopy. The obtained trends for crystallization rates were explained using the concept of flow-induced crystallization. Further, direction dependent (machine and transverse) tensile properties were studied as a function of take-up ratio (TUR), inflation air pressure and cooling conditions. Based on the results for development of crystallinity at different conditions, the reciprocal crystallization half time was suggested as a likely essential parameter to formulate processing-structure-property relationships.
Stability and Nonlinear Dynamics of Film Blowing
Transient behavior and stability of the film blowing process have been studied using the governing equations consisting of two well-known force balances and a Phan- Thien and Tanner constitutive equation. A newly-devised numerical scheme, which incorporates an orthogonal collocation on finite elements, was employed to yield transient solutions of the film blowing operation which are hitherto difficult to obtain due to severe numerical stability problems when the system is in an instability called draw resonance. Thus obtained simulation results make possible more systematic analysis of draw resonance, e.g., draw resonance criterion based on the traveling times of kinematic waves on the free surfaces, and the effects of fluid viscoelasticity on the stability.
Measurement of the Effect of Pigments over Time on the Mechanical and Thermal Properties of Propylene-Ethylene Block Copolymer
Injection moulded propylene-ethylene block copolymer samples containing 0-8% fluorescent organic pigment were prepared. Mechanical and thermal analysis were performed within one week after processing and then again after 8 weeks. The results show that after natural ageing of the samples there were significant improvements in mechanical performance and a modification in the structure of the samples.
Prediction of Long-Term Creep Behavior of Epoxy Adhesives for Aluminum Substrates
Epoxy-based adhesives for bonding aluminum substrates have gathered significant interest in recent years. Yet, more work is needed to learn how epoxy adhesives withstand creep and exposure to various environmental conditions. In this study, both experimental and modeling work (using Ngai's Coupling) has been conducted to predict creep behavior of epoxy adhesives under moisture exposure.
Effects of Aspect Ratio and Clay Particle Orientation on the Mechanical Properties of Nylon-6/Clay Nanocomposites
Nylon-6/clay nanocomposites with varying clay aspect ratios and particle orientations were prepared by a large-scale simple shear process, which alters the morphology within the nanocomposite. Tensile tests indicate that the modulus and strength of the nanocomposites decrease as both the clay aspect ratio and orientation are reduced. In nylon-6, however, the reduction of the clay aspect ratio and orientation leads to an increase in toughness and ductility.
Structure and Mechanical Properties of Glass Fiber Reinforced PC/ABS Fabricated by Ultra High Speed Injection Molding
The morphology and mechanical properties of glass fiber reinforced PC/ABS injection moldings were investigated. The effects of injection speed on them and the correlation between them were discussed. The morphology was drastically changed by ultra-high speed injection. The orientation of glass fibers was also changed and it results in lower decrease of tensile properties than injection moldings at common injection speed.
Stagnating Flows at the Screw Tip during Extrusion
Stagnation of polymer materials at the screw tip is a common problem for many extrusion processes with thermoset or thermal sensitive materials. Cured or burnt materials are often found at the screw tip and cause quality problems. Another example is a frequent color change. It may take a long time to purge the old color completely and creates a large amount of scrap.A mathematic model has been developed to simulate the polymer flow at the screw tip. Streamlines and residence time distributions have been obtained to understand the stagnating flow. The screw tip designs have been evaluated with the model. Also evaluated are the gaps between the screw tip and screen pack. The potential solutions to the stagnating flow are discussed.
Single Screw Solids Conveying - Different Polymers and a General Purpose Screw
In this paper we will discuss the differing solids conveying rates of several polymers using a “general purpose square pitch screw.” It is often desired to change polymer in an extruder as the products that are sold in a company change a the time or capital needed to pull the screw an replace it are not available. Often the results are confounding because the rates one obtains are dramatically different for the new polymer. In this paper we will present data for six polymers which demonstrate that the output of a typical solids conveying screw changes substantially as back pressure is increased on the solid bed being conveyed.
Temperature Measurement in Single Screw Extrusion: Late Melting and Thermal Instabilities
Various temperature measurement techniques have been used to investigate thermal profiles in the die of a 60mm single screw extruder, including invasive and wall mounted thermocouples, thermocouple meshes, ultrasound, and infrared. For a general-purpose polyolefin screw, large temperature differences of the order of 20°C were observed over short time periods of less than 1 second, in the exit melt temperature. These instabilities were evident during measurement of bulk melt temperature and are believed to be a result of melting instabilities. Predictive temperature plots obtained from CFD simulations using a commercial software package show qualitative agreement with the empirical results.
Effect of Screw Geometry on Melt Temperature Profile
Thermocouple meshes have been used to measure the temperature profile of polyethylene melt at the exit of a 60mm single screw extruder. Measurements have been made across a 38mm cross-section using a mesh with seven junctions. The meshes are located across the melt and provide temperatures at discrete positions across the flow, from which a thermal map can be constructed. The effect of screw geometry is investigated, with comparisons made between a general purpose polyolefin screw with gradual melting zone, a rapid transition screw, and a barrier flighted screw with a Maddock mixer. Significant differences in melting and temperature profiles were observed between the three extruder screws.
Air vs. Water Cooled Single Screw Extruders
Processors need to know if an air cooled extruder is adequate to their requirements or if they need the higher capacity of water cooling. This decision is often made based on experience, tempered with a fear of guessing wrong. If water cooling was used in the past, many processors are reluctant to try air cooling on a new machine. This paper compares the experimental data of various temperature settings and other operating conditions on a 90mm extruder, precisely repeated with an air and water cooled barrel heater on the same machine with the same screw. The data is then compared and quantified to establish useful guidelines for the application of water vs. air cooling.
A Novel Method of Measuring Viscosity and Tracing the Morphology Evolution Using Single Screw Extruder: The Screw Rheometer
A novel method of using single screw extruder as measuring viscosity and analyzing morphology evolution of polymer blend was elucidated. Combination of a batch wise operation of single screw extruder (the closed discharge condition) and using the modernized high-speed data acquisition system was a key technology of the method. The viscosity measured by “Screw Rheometer” was well matched with that by conventional capillary rheometer. Also the viscosities of rubber like polymers and low viscous materials such as polyamide were also successfully measured. The device also used to observe evolution of morphology for the immiscible polymer blend in controlled shearing state.
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