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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Evaluation of durability and structure of peroxide cross-linked polyethylene pipes with several stabilizers
Cross-linked polyethylene (PEX) pipes used in hot water supply are required for high mechanical strength and high creep resistance at high temperature. Especially PEX-a pipes which are made by peroxide cross-linking have better performance, such as creep resistance and thermal shock resistance than the pipes made by the other cross-linking method. Because the PEX-a pipes indicate the higher degree of cross-linking as compared with the other PEX pipes. In this study, the PEX-a pipes which were mixed with several stabilizers were tested to evaluate the effects on degree of cross-linking and the oxygen induction time. And also they are tested to evaluate the performance of the long-term hydrostatic pressure test and the long-term hydro dynamic pressure test with chlorine test. As a result, it was found that the combination of antioxidants for PEX-a pipes plays an important role to prolong the oxygen induction time without inhibiting the cross-linking. From the results of the 1H pulsed NMR measurement over the melting point of polyethylene, it was found that each peroxide PEX pipe with different antioxidant combinations indicated the different proportion and cross-linking density of cross-linking region, in addition, that these pipes had the effective structure of cross-linking for the hydrostatic and hydrodynamic pressure test with chlorine solution. Therefore, it was considered to be useful results for studies of the stricture of cross-linking of polyethylene.
3D-CFD-Simulation of Polymer Plastification in a Single Screw Extruder under High-speed Conditions
This paper presents an approach for 3D-CFD-simulations of plastification of polymeric materials in highspeed extrusion processes. A new material model enables to differ between solid phase and fluid phase in dependence of temperature in just one set of property descriptions. Hence it becomes possible to simulate melting in a single fluid domain without presupposing any melting mechanism. The main focus is set on the numerical robustness of the model so that it is applicable for simulations of extrusion processes under high-speed conditions. Until now trials for a 35 mm-extruder with screw speeds up to 2000 rpm have been tested successfully.
The Effects of Type and Loading of Radiopaque Fillers on the Properties of Polyether Blick Amide Compounds
Radiopaque compounds used to produce catheters that are inserted into the body for diagnostic or interventional procedures often use a polyether block amid based polymer. A number of radiopaque fillers are compounded into the polyether block amide polymers to render the catheter visible under fluoroscopy or x-ray imaging. Data on the effects of the various radiopaque fillers on the properties of the polyether block amide polymers is not readily available. This paper will demonstrate the effects of type and loading of radiopaque fillers on polyether block amide polymers.
A Numerical and Experimental Investigation of Factors Affecting Weld Line Quality
Improper mold venting can cause defects we usually overlooked. We studied different venting block designs using movable inserts in the mold, e.g. along the flow direct ion cross the flow direct ion. The resulting tensile specimen were injected at different inject ion speeds including 100, 300, and 500 mm/s, and were later subjected to the tensile test for their strength. The venting design effects on melt temperature and pressure were verified by numerical method with same processing conditions. The results showed that the temperature and the pressure increased with the inject ion speed. The product tensile strength also enhanced with increasing injection speeds and when proper venting was conducted.
Uses and Limitations of the 'Rule of Mixtures' in Polyethylene Blends for Rotational Molding
The rotomolding process is distinguished by a strong dependence on polyethylene (PE) as the main material used. In order to provide a range of different properties, PE grades are often blended together. This study examines the use of the well-known “rule of mixtures” for predicting the performance of PE blends from the properties of the individual blend components. Blends of high and low density linear PE’s were tested for composite melt index, density, tensile / flexural properties and impact strength. In addition, differential scanning calorimetry was used to evaluate the crystalline content of each blend and whether the blend components had co-crystallized or had formed separate domains.
Characteristic of High Performance Biomass Plastic (Effect of Compounding Screw Geometry and Wood Particle Size)
Filler reinforced thermoplastics especially for natural filler reinforced plastics have been frequently used to improve the physical and thermal properties of polymer materials in plastic industry due to their low density, low cost and environmental friendliness. At current study, a preliminary investigation on the mechanical properties and morphologies of polypropylene (PP) reinforced by wood powder were carried out. Two different compounding screws with different mixing sections were used to evaluate the effect of compounding screw geometry on the appearance and mechanical properties of cellulose/PP composites since the screw section geometry has an effect on the final mixing condition of filler/matrix, filler damage and scorch. Additionally, the effect of wood particle size on the mechanical properties of wood/PP composites was also evaluated based on the tensile and Izod impact tests. The reflection-type optical microscope and scanning electron microscope (SEM) observation on the specimen surfaces were used to discuss the powder distribution degrees and interface properties.
Halogen Free Polyphenylene Sulfide for Consumer Electronics Applications
The recent push for environmentally friendly halogen?free products has resulted in significant changes in the of polymer materials used in consumer electronics industry. A series of halogen free polyphenylene sulfide (PPS) products were developed to enable consumer electronics original equipment manufacturers and their suppliers to design and make products that will comply with halogen?free industry standards. These halogen free PPS products offer inherent flame retardancy (UL-94 V0), high flow suitable for small connectors, and high dimensional stability for metal over molding parts without loss of superior mechanical properties.
Validation of a highly thermally conductive iron-cobalt-nickel alloy as tool material for injection molds
With injection molding the tool is the basic component of the process. For applications in which a high distribution of heat is required or particular value is placed on good molding accuracy it is necessary to use tool materials with a higher thermal conductivity. Previous materials can be replaced by an iron- cobalt-nickel alloy with increased thermal conductivity, high strength and a thermal expansion behavior the same as steel. The University of Applied Sciences Schmalkalden, Germany, has had the opportunity to investigate and evaluate a new type of iron-cobalt-nickel alloy with regard to its suitability as tool material for injection molds.
A Novel Method for the Evaluation of Particle Tracking Simulations of Mixing Processes
In polymer processing, as well as in many other fields of process engineering, the prediction of mixing processes using numerical methods is still a problem not satisfactorily solved so far. Besides some other methods particle tracking simulations have become state-of-the art. Usually, statistical measures are used to evaluate the particle distribution. Unfortunately, all statistical measures show a numerical limit, which makes it difficult to compare different simulation results. In this study a new method for the evaluation of particle tracking simulations of mixing processes is presented. The enhancement of internal interfaces is calculated using the positions from tracer particles originating from two particle clouds as a measure for the mixing quality. Verification is carried out using a comparison with an analytical solution of a couette flow. Finally, the results from the presented evaluation method are compared with a number of established statistical mixing quality measures.
High speed thermal imaging of complex micromoulding flows
The thermal characteristics of the boundary between the polymer melt and mould tool are important considerations for injection moulding processes but are particularly relevant for microinjection moulding or thin walled processes where the high surface area to volume ratio and small product masses results in internal morphologies and resulting mechanical properties which can be highly influenced by the thermal field. In this paper we describe work to measure thermal fields and characterise the cooling behaviour of a micromoulding process using high speed thermal imaging techniques to better understand the thermal behaviour.
Silicone Elastomers - Clear as Glass Transparent Liquid Silicone Rubbers For Lighting Applications
For many years PC and PMMA were materials of choice for optical applications beside glass. These poly- meric materials have advantages such as weight reduction, increased freedom in design complexity, and better manufacturing economics due to lower energy consumption and less post processing when com- pared to glass. One has to also consider the tradeoffs when making a decision to use thermoplastics due to their less superior thermal, UV and chemical resistance against glass.A new alternative is now available with the "glass-clear" LSR7OOO silicone elastomer family from Mo- mentive Performance Materials. This new material combines the physical property benefits of silicones, ease & high productivity process advantage of liquid silicone rubbers (LSR) and an optical transparency of 95%. Since silicone polymers have an inorganic backbone, it offers better thermal and UV resistance when compared against thermoplastics.LED Lighting demands a combination of extreme material properties. For this application typically re- quires materials to withstand the harsh blue light radiation in combination with a maximum lamp temper- ature of up to 150?C for 100,000 hrs, which is the lifetime of a typical LED System. Due to its inorganic backbone, LSR7OOO offers superior performance in this extreme environment compared to other trans- parent organic plastics. LSR7OOO provides an outstanding thermal, UV, and blue light stability which makes this material an ideal candidate for the production of lenses for high power LEDs in the automotive and consumer lighting markets.Liquid Silicone Rubber Processing also brings various advantages. Due to its elastomeric properties, molded in stress and birefringence on finished parts are minimized. Material waste is reduced to a mini- mum through cold runner technology. Due to its low viscosity and processing conditions, LSRs are able to replicate parts with intricate details.This paper gives an overview of the special material properties of the ultra-transparent LSR7OOO and compares physical data to commercial optical thermoplastics. Application examples highlight present and future use of this innovative material. For many years PC and PMMA were materials of choice for optical applications beside glass. These poly- meric materials have advantages such as weight reduction, increased freedom in design complexity, and better manufacturing economics due to lower energy consumption and less post processing when com- pared to glass. One has to also consider the tradeoffs when making a decision to use thermoplastics due to their less superior thermal, UV and chemical resistance against glass. A new alternative is now available with the glass-clear" LSR7OOO silicone elastomer family from Mo- mentive Performance Materials. This paper gives an overview of the special material properties of the ultra-transparent LSR7OOO and compares physical data to commercial optical thermoplastics. Application examples highlight present and future use of this innovative material molded in stress and birefringence on finished parts are minimized. Material waste is reduced to a mini- mum through cold runner technology. Due to its low viscosity and processing conditions
Investigation of Crosslinking and Crystallization Behaviors of Polyethylene Blends
Crosslinking kinetics and its influence on the subsequent crystallization of polyethylene blends were investigated by rheological measurements and thermal analysis. Results indicate that addition of small amount of polyolefin elastomer (POE) in the HDPE matrix does not accelerate the crosslinking process and the final crosslinking degree of the blends is independent of the molecular weight of each component. Crosslinking can significantly retard the crystallization process and decrease the crystallinity due to the hindrance on chain folding caused by the formation of the network structure.
An Electro-active Actuator Made With Cellulose / Gamma Ferric Oxide / Polypyrrole
This paper reports a Method of fabricating electromechanical actuators for drug delivery. The actuators are fabricated from regenerated cellulose/ magnetic ferric oxide nanoparticles coated with polypyrrole. The actuators undergo a bending deformation when exposed to an electric field. In this paper, the properties of the actuator scaffolds are reported, including the magnitude of the displacements. The actuators can be operated in air at low voltages by consuming low electrical power. The surface and cross-sectional morphologies of the actuators were observed by SEM. The material synthesized in this study may have potential application in the development of electromechanical actuators.
Modification of PVC with bio-based PHA rubber. Part 2.
Blends of biobased polyhydroxyalkanoates (PHAs) with PVC have been developed and demonstrated very unique properties when added between 5 and 30 phr. These blends promise to improve both mechanical and environmental performance of PVC. The breakthrough is based on the miscibility of PHA and PVC resins and similar processing windows. Based on the miscibility and performance requirements, specific compositions of PHA copolymers were created to improve plasticization, impact and processing modification. In impact modification, PHA rubber copolymers outperform the best available MBS core/shell impact modifiers and do not compromise PVC transparency and UV stability. In plasticization, PHA copolymers perform as high molecular weight, readily dispersible plasticizers and enable formulation of compounds with low additive migration, low extractables, volatile loss and staining. As a processing aid, the metal adhering properties of PHA copolyesters promote homogeneous shear melting of PVC particles and prevent overheating and degradation. It will be shown that due to their multifunctional performance, the PHA modifiers could significantly simplify the formulation of PVC compounds and reduce the overall amount of required additives. The PHA rubber copolymers are commercially biosynthesized by fermentation technology from renewable resources. They satisfy requirements on sustainability and biodegradability.
Fabrication of TiO2/PU Superhydrophobic Film by Nanoparticle Assisted Cast Micromolding Process
Lotus-like surfaces have attracted great attentions in recent years for their wide applications in water repellency, anti-fog and self-cleaning. This paper introduced a novel process, nanoparticle assisted cast micromolding, to create polymer film with superhydrophobic surface. Briefly, waterborne polyurethane (WPU) sol and nano TiO2/WPU sol were each cast onto the featured surfaces of the PDMS stamps replicated from fresh lotus leaves. After being dried and peeled off from the stamps, PU and TiO2/WPU replica films were created simultaneously. To the former, only high hydrophobic property was observed with static water contact angle (WCA) at 142.5°. While to the later, superhydrophobic property was obtained with WCA more than 150° and slide angle less than 3°. Scanning electron microscopy (SEM) imaging showed that the PU replica film only had the micro-papillas and the TiO2/PU replica film not only had micro papillas but also had a large number of nano structures distributed on and between the micro-papillas. Such nano and micro hierarchical structures were very similar with those on the natural lotus leaf surface, thus was the main reason for causing superhydrophobic property. Although an elastic PDMS stamp from lotus leaf was used in herein process, hard molds may also be used in theory. This study supplied an alternative technique for large scale production of polymeric films.
Temperature and Specific Mechanical Energy Profiles on a Tri-Kneader
A tri-kneader was tested against a traditional reciprocating kneader (ko-kneader) using a proprietary pre-blend of rigid PVC. The specific mechanical energy (SME) consumed was lower on the tri-kneader than in the traditional kneader (36% decrease). It was concluded that temperature control was the dominant factor affecting SME consumption. A second trial was conducted to compare SME consumption on a tri-kneader against a twin screw extruder (TSE) utilizing a proprietary color master batch with special effects. The tri-kneader showed a decrease in discharge temperature (13°C lower) and SME (45% decrease). It was concluded that the reduction in SME was mainly due to a reduction in process length.
Evaluation of Destruction Mechanism on Quasi-Isotropic GFRP
Fiber-reinforced plastic tubes can be used as permanent formwork and external reinforcement for concrete columns. Failure of such columns is often accompanied by audible noise from cracking of concrete and shifting and settling of aggregates, snapping of the inner layers of the jacket, and ultimately fiber fracture. Since the state of the concrete core is not readily visible from the outside, nondestructive evaluation tools such as acoustic emission (AE) can help assess its structural integrity. In this research, we tried to investigate the applicability of AE technique to the quasi-isotropic GFRP materials, and to correlate the AE parameters to the state of stress in concrete. As a result, it was found that the Felicity ratio depends on the internal structure of GFRP. The effect is discussed on the basis of the results of the tensile test, AE measurement, and Felicity analysis.
PLA Thermoplastic Lignin Blends
In this paper, for the first time the PLA/TPL (Thermoplastic Lignin or Plasticized Lignin) blends were developed and investigated. The PLA/TPL blends were prepared by twin-screw extrusion. The lignin and plasticizers were mixed together in the first half of the extruder to complete the plasticization of lignin. Water was removed by devolatilization at mid-extruder and the PLA matrix was mixed with the water- free TPL in the latter portion of the extruder. The PLA/TPL blends comprised 20% and 33% TPL in the PLA matrix. The TPL phase comprised 36% plasticizers in the form of glycerol and sorbitol mixtures. Very fine dispersion of TPL in the PLA matrix was obtained with the particle size less than 1µm based on SEM observation. It was found that the viscosity of the PLA/TPL blends was dramatically increased by adding a small amount of epoxy-based chain extender (CE). The PLA/TPL blends are of great interest for industrial applications such as film-blowing and foaming.
Effect of Molding Conditions on the Weld Line Property of Injection Molded Jute/PP Composites
Jute fiber is of not only low density and good mechanical property but also natural and degradable property. On the other hand, recyclable Polypropylene (PP) was also good choice for environmental friendly material. Injection molding is one of the most important processes to manufacture plastic composites because it is of high quality products with low cost. However, weld lines are unavoidable when two separate melt fronts rejoin during injection molding. The presence of weld lines not only detracts from the surface quality but also significantly reduces the mechanical strength of injection- molded parts. Although it is not always easy to completely eliminate weld lines, the weld line strength could be improved through suitable adjustment of molding conditions such as melt temperature, mold temperature, hold pressure, injection speed, and so on. Therefore, in this paper the weld line property of injection molded jute/PP dumbbell shape specimen was investigated. Pultrusion technique was adopted to fabricate jute/PP long fiber pellets (LFT) and the re-compound pellets of LFT, i.e. RP was made to improve the fiber distribution. Then LFT, RP were used to mold dumbbell shape specimens with or without weld line. In particular, the influence of back pressure and holding pressure on weld line strength of injection molded jute/PP dumbbell shape specimens was discussed based on tensile test and SEM observation.
New method of characterizing the fatigue behavior of thin films for acoustic applications at high frequencies
In the present work a new method to characterize the fatigue behavior of polymer films, which are used as loudspeaker membranes, with thicknesses down do 5 ?m at application relevant frequencies is presented. Furthermore the anisotropic fatigue behavior of different films was studied. Stress controlled Wöhler tests were performed at a frequency of 100 Hz in uniaxial cyclic tension. The failure mode and crack growth kinetics were described via linear elastic fracture mechanics. An extruded film exhibited significant anisotropy with superior fracture toughness in machine direction. By contrast, a solvent cast film showed only neglectable anisotropy in the fatigue-experiments.
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