PE-RT: A New Class of Polyethylene for Industrial Pipes

2006 ◽  
Author(s):  
Detlef Schramm
Keyword(s):  
Molecular Structure ◽  
High Temperature ◽  
High Temperatures ◽  
Power Plants ◽  
Cold Water ◽  
Industrial Applications ◽  
Pipe Production ◽  
Term Strength ◽  
Temperature Resistance

The development of a new family of PE materials with significantly improved processability and long term strength at high temperatures is discussed. These polymers form the basis for a new ISO class of polyethylene materials: PE-RT (Polyethylene of Raised Temperature resistance) for hot and cold water as well as industrial pipe applications. These materials have a unique molecular structure and crystalline microstructure, which provides excellent Long Term Hydrostatic Strength at high temperature without crosslinking the material. PE-RT type materials are successfully used in domestic hot and cold water piping systems for most applications. The easy processing and outstanding material properties made these resins also attractive for use in many industrial applications, where larger dimensions are required and regular Polyethylene cannot be used or has temperature limitations. They also compete against high end engineering plastics, offering significant cost savings. These materials provide significant process advantages to the converters, allowing high line speed pipe production and providing excellent flexibility and ease of installation for the application. A recently developed PE-RT type material offers still higher long-term strength at high temperature and further improved processability. This combination makes this resin particularly suitable for high temperature applications. An example of the latter is in larger diameter cooling water pipes in power plants. Pipes based on these materials can be connected via heat welding or by the use of mechanical fittings. Furthermore this material can be used in industrial applications, were traditional Polyethylene is limited by the temperature resistance and metallic materials suffer from corrosion. The excellent weldability of these materials provides various opportunities to connect also larger dimensions in industrial applications. Another example of this is the use in multi-layer structured oil pipelines on-shore and off-shore. This paper presents the material science and product design concepts that govern the high long-term hydrostatic strength at high temperatures. By controlling the molecular structure, the melt rheology and solid state properties can be influenced. This results in a unique balance of processability and hydrostatic strength. Further discussed are the product features and benefits of PE-RT materials. The paper shows examples of the application range for this type of products, using applications in the domestic pipes market as a reference study.

scholarly journals Insights into the Maturation of Pernisine, a Subtilisin-Like Protease from the Hyperthermophilic Archaeon Aeropyrum pernix

2020 ◽  
Vol 86 (17) ◽  
Author(s):  
Miha Bahun ◽  
Marko Šnajder ◽  
Dušan Turk ◽  
Nataša Poklar Ulrih
Keyword(s):  
High Temperature ◽  
High Temperatures ◽  
Catalytic Domain ◽  
Industrial Applications ◽  
Binding Motif ◽  
Content Type ◽  
Hyperthermophilic Archaeon ◽  
Aeropyrum Pernix ◽  
Autocatalytic Process ◽  
Exceptional Stability

ABSTRACT Pernisine is a subtilisin-like protease that was originally identified in the hyperthermophilic archaeon Aeropyrum pernix, which lives in extreme marine environments. Pernisine shows exceptional stability and activity due to the high-temperature conditions experienced by A. pernix. Pernisine is of interest for industrial purposes, as it is one of the few proteases that has demonstrated prion-degrading activity. Like other extracellular subtilisins, pernisine is synthesized in its inactive pro-form (pro-pernisine), which needs to undergo maturation to become proteolytically active. The maturation processes of mesophilic subtilisins have been investigated in detail; however, less is known about the maturation of their thermophilic homologs, such as pernisine. Here, we show that the structure of pro-pernisine is disordered in the absence of Ca2+ ions. In contrast to the mesophilic subtilisins, pro-pernisine requires Ca2+ ions to adopt the conformation suitable for its subsequent maturation. In addition to several Ca2+-binding sites that have been conserved from the thermostable Tk-subtilisin, pernisine has an additional insertion sequence with a Ca2+-binding motif. We demonstrate the importance of this insertion for efficient folding and stabilization of pernisine during its maturation. Moreover, analysis of the pernisine propeptide explains the high-temperature requirement for pro-pernisine maturation. Of note, the propeptide inhibits the pernisine catalytic domain more potently at high temperatures. After dissociation, the propeptide is destabilized at high temperatures only, which leads to its degradation and finally to pernisine activation. Our data provide new insights into and understanding of the thermostable subtilisin autoactivation mechanism. IMPORTANCE Enzymes from thermophilic organisms are of particular importance for use in industrial applications, due to their exceptional stability and activity. Pernisine, from the hyperthermophilic archaeon Aeropyrum pernix, is a proteolytic enzyme that can degrade infective prion proteins and thus has a potential use for disinfection of prion-contaminated surfaces. Like other subtilisin-like proteases, pernisine needs to mature through an autocatalytic process to become an active protease. In the present study, we address the maturation of pernisine and show that the process is regulated specifically at high temperatures by the propeptide. Furthermore, we demonstrate the importance of a unique Ca2+-binding insertion for stabilization of mature pernisine. Our results provide a novel understanding of thermostable subtilisin autoactivation, which might advance the development of these enzymes for commercial use.

scholarly journals Long-Term Strength of a Composition of Complex Refractory Coating and Single-Crystal Rhenium-Alloyed Nickel Alloy after High-Temperature Holds

2013 ◽  
Vol 55 (7-8) ◽  
pp. 403-408
Author(s):  
V. P. Kuznetsov ◽  
V. P. Lesnikov ◽  
E. V. Moroz ◽  
M. S. Khadyev ◽  
I. P. Konakova
Keyword(s):  
High Temperature ◽  
Single Crystal ◽  
Nickel Alloy ◽  
Term Strength ◽  
Refractory Coating ◽  
Alloyed Nickel

Prediction of High-Temperature Long-Term Strength of Materials

2013 ◽  
Vol 45 (5) ◽  
pp. 517-522 ◽  
Author(s):  
N. K. Kucher ◽  
R. P. Prikhod’ko
Keyword(s):  
High Temperature ◽  
Term Strength ◽  
Strength Of Materials

scholarly journals Improving the Thermal Stability of Hydrophobic Associative Polymer Aqueous Solution Using a “Triple-Protection” Strategy

Polymers ◽  
2019 ◽  
Vol 11 (6) ◽  
pp. 949 ◽  
Author(s):  
Bo Yang ◽  
Jincheng Mao ◽  
Jinzhou Zhao ◽  
Yang Shao ◽  
Yang Zhang ◽  
...  
Keyword(s):  
High Temperature ◽  
High Temperatures ◽  
Elevated Temperatures ◽  
Polymer Network ◽  
Crosslinking Agent ◽  
Water Soluble ◽  
Fluid Viscosity ◽  
Fracturing Fluid ◽  
Temperature Resistance ◽  
Protection Strategy

Because of their high viscoelasticity, Hydrophobic Associative Water-Soluble Polymers (HAWSPs) have been widely used in many industrial fields, especially in oilfield flooding and fracturing. However, one major problem which limits the wide applications of HAWSPs is their weak resistance to high temperatures. Once the temperature increases over 100 °C, the viscosity of the fracturing fluid decreases rapidly, because high temperatures reduce fluid viscosity by oxidizing the polyacrylamide chains and weakening the association of hydrophobic groups. To improve the high temperature resistance of one HAWSP, a triple-protection strategy was developed. First, rigid N-vinyl-2-pyrrolidone moiety was introduced into the polymer chains. Second, an environmentally-friendly deoxidizer, carbohydrazide, was selected to prevent polymer oxidization by scavenging dissolved oxygen. Results showed that both the rigid groups and the deoxidizer improved the temperature resistance of the polymer and helped it maintain high viscosity under high temperature and shear rate. Using these two protection strategies, the resistant temperature of the polymer could reach 160 °C. However, the polymer network still got severely damaged at further elevated temperatures. Therefore, as the third protection strategy, the pre-added high temperature responsive crosslinking agent was applied to form new networks at elevated temperatures. The results have shown that the optimized polymer solution as a kind of fracturing fluid showed good temperature resistance up to 200 °C.

Long-Term Strength and Design of Polyethylene Compounds for Pressure Pipe Applications

2009 ◽  
Author(s):  
Stephen J. Boros
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
Elevated Temperatures ◽  
Hydrostatic Stress ◽  
Stress Rupture ◽  
Term Strength ◽  
Viscoelastic Creep ◽  
Pressure Pipe ◽  
Code Language

The interest in using polyethylene pipe in Class 3 safety water systems in nuclear power plants has grown tremendously in the last few years. PE pipe brings a host of benefits to the application in the form of long-term performance and reliability due to not being prone to corrosion and tuberculation. As the work continues through various ASME committees to develop the appropriate code language for the design and use of PE pipe, it is clear that plastics are not evaluated the same way metallic components would be in similar applications. However, the nature of the failure (i.e. ductile or brittle) is important for both. This paper will give an overview of the methodology used to establish the long-term hydrostatic strength of polyethylene compounds, and how that strength is used for engineering design in a safe a reliable manner. The strength of a polyethylene compound, being a thermoplastic, cannot be determined from a short-term tensile strength test, as with most metals. As such, testing and evaluation methodologies have been developed which take into account the viscoelastic creep response of thermoplastics, as well as potential changes in failure mode, in order to forecast the long-term hydrostatic strength of these materials so they can be safely used in a pressure pipe application. Since PE was first used in a piping application in the late 1950s, PE has continued to evolve as have the methodologies used to evaluate its strength against stresses induced by hydrostatic pressure. The common method for evaluation relies on putting specimens under multiple continuous, steady-state stress levels until failure. These data points are then used in a log-log linear regression evaluation. This regression equation is then extrapolated to a point sufficiently further out in time to where a long-term strength can be established. It has been clearly established that over a temperature range that the stress rupture behavior of PE follows an Arrhenius, or rate process, relationship between temperature and strength. By testing at elevated temperatures it can be “validated” that the extrapolation remains linear and ductile beyond the actual test data. This and other criteria established by ASTM D 2837 and the Plastics Pipe Institute’s Hydrostatic Stress Board allow for establishing an appropriate maximum working stress that will assure a very long design life.

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