scholarly journals A Review of Methods Used to Reduce the Effects of High Temperature Associated with Polyamide 12 and Polypropylene Laser Sintering

2020 ◽  
Vol 2020 ◽  
pp. 1-11 ◽  
Author(s):  
Fredrick M. Mwania ◽  
Maina Maringa ◽  
Kobus van der Walt
Keyword(s):  
High Temperature ◽  
High Temperatures ◽  
Chemical Properties ◽  
Polymeric Materials ◽  
Laser Sintering ◽  
Percentage Elongation ◽  
Elongation At Break ◽  
Polyamide 12 ◽  
Materials Used ◽  
And Chemical Properties

The polymer laser sintering (PLS) process is one of the most promising additive manufacturing (AM) technologies for polymeric materials. However, the technique has challenges because the physical, mechanical, and chemical properties of the polymeric powder deteriorate due to the high temperatures prevailing in the build chamber during manufacture. These high temperatures cause agglomeration of powder, which leads to a decrease in the flowability of powder. There is also a related drop in the coalescence of the powder granules during PLS, which results in porosity that undermines the mechanical integrity of printed parts. Moreover, the viscosity of the melt increases due to cross-linking of molecular chains. This, in turn, increases the tensile strength of the printed components at the expense of the percentage elongation at break. Thus, high prolonged processing temperatures decrease the reusability of polymeric materials used in PLS. In this paper, a review of the studies conducted to investigate ways of reducing the effects of high temperature on polymeric powders is presented.

Influence of Regeneration Condition on Physical and Chemical Properties of High Temperature Coal Gas Desulfurization Sorbent

2014 ◽  
Vol 521 ◽  
pp. 658-661
Author(s):  
Lei Yang ◽  
Shang Guan Ju ◽  
Yu Kun Gao ◽  
Yan Hui Hu
Keyword(s):  
High Temperature ◽  
Circulatory System ◽  
Chemical Properties ◽  
Space Velocity ◽  
Physical And Chemical Properties ◽  
Coal Gas ◽  
Regeneration Condition ◽  
Atmosphere Temperature ◽  
Physical And Chemical ◽  
And Chemical Properties

Physical and chemical properties are closely related to desulfurization, regeneration performance and cycle stability for high temperature coal gas desulfurizer. This review focuses on influence rules of changes in regeneration atmosphere, temperature and space velocity on physical and chemical properties. A large number of experimental researches have shown that regeneration atmosphere, regeneration temperature, space velocity have an important influence on mechanical strength, active component and texture change for high temperature coal gas desulfurizer. The different regeneration atmosphere obviously results in different active ingredients for desulfurization sorbent after regeneration, and regeneration at a higher regeneration temperature will easily cause desulfurizer sintering, as well as small regeneration space velocity can lead to the formation of sulfates. In order to make the circulatory system of sulfidation-regeneration-sulfidation need to the requirements in industrial application, the further research of influence rules of regeneration condition on physical and chemical properties will be crucial.

Dielectric Characterisation of Plastics for Microwave Oven Applications

2005 ◽  
Vol 480-481 ◽  
pp. 161-164 ◽  
Author(s):  
Luís Cadillon Costa ◽  
A. Correia ◽  
A. Viegas ◽  
João Bessa Sousa ◽  
François Henry
Keyword(s):  
Low Cost ◽  
Chemical Properties ◽  
Microwave Frequency ◽  
Microwave Oven ◽  
Complex Dielectric Constant ◽  
First Order ◽  
Constant E ◽  
Materials Used ◽  
Resonant Method ◽  
And Chemical Properties

The materials used in microwave oven cavities must have specific dielectric properties in order to maintain the efficiency of the food heating. Plastics, by their mechanical and chemical properties and low cost, are one of those potential materials. In this study, we present the results of the measurements of complex dielectric constant, ´´ ´ * e e e í − = , in the microwave frequency region, on different plastics: polyoxymethylene (POM), polypropylene (PP) and polybutylene terephtalate (PBT), using the cavity resonant method. We measure the shift in the resonant frequency of the cavity, Df, caused by the insertion of the sample, which can be related to the real part of the complex permitivitty, e´, while the change in the inverse of the quality factor of the cavity, D(1/Q), gives the imaginary part, e´´. The relations are simple when we consider only the first order perturbation in the electric field caused by the sample.

Sintering of Alumina-AIN System for Heat Sink

2013 ◽  
Vol 465-466 ◽  
pp. 76-80
Author(s):  
Nor Hafiez Mohamad Nor ◽  
Ismail Muhammad Hussain ◽  
Nur Atikah Abu Kasim ◽  
Wan Dung Teng ◽  
M.K. Idham
Keyword(s):  
Thermal Conductivity ◽  
High Temperature ◽  
Heat Sink ◽  
Sintering Temperature ◽  
Chemical Properties ◽  
Modulus Of Rupture ◽  
Acceptable Result ◽  
Mixed Powder ◽  
Value Analysis ◽  
And Chemical Properties

Aluminium alloys is widely applied in heat sink but its application of heat absorption is still unsatisfied. While, Aluminum Nitride (AIN) was discovered as another option for heat sink application because of its great thermal conductivity and it also has high electrical conductivity at high temperature. Thus, the mechanical and chemical properties of a sintered mixed powder of Alumina and AIN are investigated experimentally. There are five different compositions of mixed powder of Alumina-AIN and sintered at three different sintering temperatures which are 1400°C, 1500°C and 1600°C. As applying a high sintering temperature on samples inducted great flexural strength and increase it modulus of rupture. High sintering temperature (1600°C) also affected the materials microstructure as the particle was arranged closely between each other and reduces the amount of porosity. The application of high temperature in the mixture of AIN with Alumina reduces the occurrence of flaws like cracking and accordingly improves the strength. These combination of Alumina-AIN brought acceptable result in thermal conductivity value analysis and as well enhancing the thermal conductivity.

scholarly journals State-of-the-Art Modification of Plastic Aggregates Using Gamma Irradiation and Its Optimization for Application to Cementitious Composites

2021 ◽  
Vol 11 (21) ◽  
pp. 10340
Author(s):  
Heonseok Lee ◽  
Hyeonwook Cheon ◽  
Yonghak Kang ◽  
Seungjun Roh ◽  
Woosuk Kim
Keyword(s):  
Compressive Strength ◽  
Gamma Irradiation ◽  
Performance Improvement ◽  
Mechanical Performance ◽  
State Of The Art ◽  
Chemical Properties ◽  
Polymeric Materials ◽  
Cementitious Composites ◽  
Gamma Irradiated ◽  
And Chemical Properties

In the past few decades, there have been numerous attempts to add plastic aggregates composed of polymeric materials to cementitious composites, either as an alternative to using natural aggregates or as fillers and fibers. However, the addition of plastic aggregates often results in cementitious composites with lower mechanical performance. In this paper, we attempt to address this issue by applying gamma irradiation technology to restore the mechanical performance. We aimed to determine the optimal gamma irradiation and mixing combinations by comparing the experimental results with information summarizing the recent literature related to the use of gamma-irradiated plastic aggregates within cementitious composites. To this end, the effects of changes in the physical and chemical properties of plastics due to irradiation with gamma irradiation on the strength of cementitious composites were evaluated using irradiation doses of 25, 50, 75, and 100 kGy and various plastic materials as key parameters. In the compressive strength test, it was found that adding gamma-irradiated plastic increased the compressive strength of the cementitious composites compared to the nonirradiated plastic. This suggests that the irradiation of plastic aggregates with gamma rays is an effective method to recover some of the strength lost when plastic aggregates are added to cementitious composites. In addition, modifications in the microstructure and chemical properties of the gamma-irradiated plastic were analyzed through SEM and FT-IR analysis, which allowed the determination of the strength enhancement mechanism. The results of this study show the possibility of the state-of-the-art performance improvement method for using plastic aggregate as a substitute for natural aggregate, going further from the plastic performance improvement technology for limited materials and radiation dose presented in previous studies.

ZGS 10% RHODIUM-PLATINUM

Alloy Digest ◽  
1979 ◽  
Vol 28 (3) ◽  
Keyword(s):  
Corrosion Resistance ◽  
High Temperature ◽  
Physical Properties ◽  
Tensile Properties ◽  
Zirconium Oxide ◽  
Base Alloy ◽  
Chemical Properties ◽  
Heat Treating ◽  
Highly Dispersed ◽  
And Chemical Properties

Abstract ZGS 10% Rhodium-Platinum is a grain stabilized platinum-base alloy containing a small amount of highly dispersed zirconium oxide. Its production and general characteristics are closely related to those of ZGS Platinum which also is strenghtened by highly dispersed zirconium oxide (Alloy Digest Pt-2, May 1975). ZGS 10% Rhodium-Platinum is significantly stronger at high temperatures and more creep resistant than the conventional high-temperature rhodium-platinum alloys, while retaining their useful electrical and chemical properties. This datasheet provides information on composition, physical properties, microstructure, hardness, elasticity, and tensile properties as well as creep. It also includes information on corrosion resistance as well as forming, heat treating, machining, and joining. Filing Code: Pt-3. Producer or source: Matthey Bishop Inc..

Vulcanization and Vulcanizate Properties of a Fluoroelastomer Containing Epoxy Groups as Cure Sites

1981 ◽  
Vol 54 (4) ◽  
pp. 779-796 ◽  
Author(s):  
G. Kojima ◽  
H. Kojima ◽  
M. Morozumi ◽  
H. Wachi ◽  
M. Hlsasue
Keyword(s):  
High Temperature ◽  
Vinyl Ether ◽  
Room Temperature ◽  
Chemical Properties ◽  
Complex Shapes ◽  
Different Types ◽  
Hostile Environments ◽  
Epoxy Groups ◽  
And Chemical Properties ◽  
Glycidyl Vinyl Ether

Abstract The vulcanization behavior and vulcanizate properties of tetrafluoroethylene-propylene elastomer containing a small amount of glycidyl vinyl ether as cure site was investigated both at room temperature and at high temperature with different types of the vulcanizing agents. The conclusions are: 1. Glycidyl vinyl ether incorporates into the tetrafluoroethylene-propylene copolymerization system without disturbing the alternating microstructure and works as an efficient cure site. 2. The room-temperature vulcanization of the terpolymer proceeds at an adequate rate when tris(dimethylaminomethyl)phenol is used as the curative together with phenol as the accelerating agent. 3. Coatings of the terpolymer make a tough finish on many substrates such as steel and hydrocarbon rubbers and protect the substrates from hostile environments. 4. The vulcanization behavior of the terpolymer at high temperature is much influenced by the kind of curative. The carboxylate of hexamethylenediamine [e.g., hexamethylenediamine-N,N′-bis(p-isopropylbenzoate)] provides balanced vulcanization behavior and mechanical properties suitable for molding articles of complex shapes. 5. The mechanical and chemical properties of the high-temperature vulcanizate thus obtained are similar to those of the tetrafluoroethylene-propylene binary system vulcanized by peroxide.

scholarly journals Behaviour of high-performance concrete at high temperatures: some highlights

2017 ◽  
Vol 2 ◽  
pp. 45-52 ◽  
Author(s):  
Pierre Pimienta ◽  
Maria Cruz Alonso ◽  
Robert Jansson McNamee ◽  
Jean-Christophe Mindeguia
Keyword(s):  
High Temperature ◽  
High Temperatures ◽  
High Performance ◽  
High Performance Concrete ◽  
State Of The Art ◽  
Technical Committee ◽  
Rilem Technical Committee ◽  
Civil Structures ◽  
Physicochemical Changes ◽  
Materials Used

High-performance concrete (HPC) is one of the most recent types of concrete among the materials used routinely in building and civil structures. Their development in structures applications and the growing need for the justification of their fire resistance has led several laboratories to carry out research on their properties at high temperature. This letter presents some main aspects related to their physicochemical changes, thermal properties and mechanical properties at high temperature. It introduces a State of The Art prepared by the RILEM Technical Committee 227-HPB (Physical properties and behaviour of High-Performance Concrete at high temperature) and untitled “Behaviour of High-Performance Concrete at high temperatures”. This State of the Art will be publish in a next future.

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