Mechanical Properties of Epoxy Adhesive Under Thermal Aging and Their Chemical Degradation Behavior

2021 ◽  
Vol 21 (8) ◽  
pp. 4444-4449
Author(s):  
Bongjin Chung ◽  
Shin Sungchul ◽  
Jaeho Shim ◽  
Seongwoo Ryu
Keyword(s):  
Mechanical Properties ◽  
Thermal Aging ◽  
Photoelectron Spectroscopy ◽  
Thermal Exposure ◽  
Chain Scission ◽  
Epoxy Adhesive ◽  
Chemical Degradation ◽  
Adhesive Properties ◽  
Noticeable Reduction

Epoxy adhesive was analyzed under long term thermal aging and mechanical properties and chemical degradation were observed by X-ray photoelectron spectroscopy (XPS). Long term thermal exposure of epoxy causes a noticeable reduction in adhesive properties. We developed a predictive model of temperature and time dependent aging. The temperature dependent aging behavior of epoxy adhesive shows good agreement with conventional Arrhenius equations. Using XPS analysis, we also discovered a correlation between chemical degradation and the adhesive properties. Decay of C–C bonding ratio induced chain-scission of epoxy adhesive; increase of total numbers of C–O and C═O induced oxidation of epoxy adhesive during thermal exposure.

scholarly journals Scission, Cross-Linking, and Physical Relaxation during Thermal Degradation of Elastomers

Polymers ◽  
2019 ◽  
Vol 11 (8) ◽  
pp. 1280 ◽  
Author(s):  
Zaghdoudi ◽  
Kömmling ◽  
Jaunich ◽  
Wolff
Keyword(s):  
Operating Time ◽  
Thermal Exposure ◽  
Chain Scission ◽  
Cross Linking ◽  
Butadiene Rubber ◽  
Compression Set ◽  
Model Compression ◽  
Relaxation Measurements ◽  
Thermally Driven

Elastomers are susceptible to chemical ageing, i.e., scission and cross-linking, at high temperatures. This thermally driven ageing process affects their mechanical properties and leads to limited operating time. Continuous and intermittent stress relaxation measurements were conducted on ethylene propylene diene rubber (EPDM) and hydrogenated nitrile butadiene rubber (HNBR) samples for different ageing times and an ageing temperature of 125 °C. The contributions of chain scission and cross-linking were analysed for both materials at different ageing states, elucidating the respective ageing mechanisms. Furthermore, compression set experiments were performed under various test conditions. Adopting the two-network model, compression set values were calculated and compared to the measured data. The additional effect of physical processes to scission and cross-linking during a long-term thermal exposure is quantified through the compression set analysis. The characteristic times relative to the degradation processes are also determined.

scholarly journals Long-Term Biostability of Pet Vascular Prostheses

2012 ◽  
Vol 2012 ◽  
pp. 1-14 ◽  
Author(s):  
Florence Dieval ◽  
Foued Khoffi ◽  
Riaz Mir ◽  
Walid Chaouch ◽  
Didier Le Nouen ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Manufacturing Process ◽  
Vascular Prosthesis ◽  
Chemical Degradation ◽  
Medical Complications ◽  
Human Metabolism ◽  
Vascular Prostheses ◽  
In Vivo Degradation

PET Vascular prostheses are susceptible to physical modification and chemical degradation leading sometimes to global deterioration and rupture of the product. To understand the mechanisms of degradation, we studied 6 vascular prostheses that were explanted due to medical complications. We characterized their level of degradation by comparing them with a virgin prosthesis and carried out physicochemical and mechanical analyses. Results showed an important reduction of the fabric’s mechanical properties in specific areas. Moreover, PET taken from these areas exhibited structural anomalies and was highly degraded even in virgin prostheses. These results suggest that vascular prostheses have weak areas prior to implantation and that these areas are much more prone to in vivo degradation by human metabolism. Manufacturing process could be responsible for these weaknesses as well as designing of the compound. Therefore, we suggest that a more controlled manufacturing process could lead to a vascular prosthesis with enhanced lifespan.

EVOLUTIONS OF MICROSTRUCTURES AND MECHANICAL PROPERTIES OF TWO CAST Ni--BASED SUPERALLOYS DURING LONG--TERM THERMAL EXPOSURE

2010 ◽  
Vol 2010 (2) ◽  
pp. 213-220 ◽  
Author(s):  
Xuezhi QIN ◽  
Jianting GUO ◽  
Chao YUAN ◽  
Jieshan HOU ◽  
Lanzhang ZHOU ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Thermal Exposure ◽  
Microstructures And Mechanical Properties

Influence of Fe Content on Microstructure and Mechanical Properties of GH984 Alloy

2015 ◽  
Vol 816 ◽  
pp. 540-545
Author(s):  
Chang Shuai Wang ◽  
Ting Ting Wang ◽  
Mei Lin Tan ◽  
Yong An Guo ◽  
Jian Ting Guo ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Structural Stability ◽  
Rupture Life ◽  
Thermal Exposure ◽  
Major Constituent ◽  
Microstructure And Mechanical Properties ◽  
Fe Content ◽  
Tcp Phase ◽  
The Cost

GH984 is an economic alloy due to the elimination of Co and its containing more than 20% Fe. As a major constituent of GH984 alloy, the Fe reduces the cost, but promotes the precipitation of TCP phase. In order to get an optimum alloy with desired balance among structural stability, mechanical properties and cost, the influence of Fe content on microstructure and mechanical properties of GH984 alloy was investigated in this paper. The results showed that the Fe content had no obvious influence on the major precipitates which were spherical γ′, blocky MC and discrete M23C6 at grain boundary after standard heat treatment, except the γ/γ ́ misfit. However, during long-term thermal exposure at 750°C, the decrease of the Fe content retarded the precipitation of η phase and enhanced the structural stability. The Fe content had no obvious influence on the tensile strength and ductility. At condition of 700°C/400MPa, the rupture life had not evident change, but the elongation decreased, the fractural model exhibited mix-fracture model and the characteristics of intergranular fracture became obvious with increasing the Fe content. It can be concluded that the decrease of Fe content can improve the structural stability and ductility.

Prediction Method of Tensile Properties and Fracture Toughness of Thermal Aged Cast Duplex Stainless Steel Piping

2005 ◽  
Author(s):  
Seiichi Kawaguchi ◽  
Takeharu Nagasaki ◽  
Koji Koyama
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Stainless Steels ◽  
Thermal Aging ◽  
Power Plants ◽  
True Strain ◽  
Prediction Method ◽  
Strain Curve ◽  
Duplex Stainless Steels

Cast duplex stainless steels of CF8M and CF8 are used in major components because of their superior characteristics, such as corrosion resistance, weldability, and so on. However, these stainless steels are known to have tendency of thermal aging embrittlement after long term service. Therefore, the mechanical properties have been investigated using tensile test specimens and fracture toughness specimens aged at 300 to 450°C for up to 40,000 hours. From the results, the effects of thermal aging on the mechanical properties of these cast duplex stainless steels were identified. The true stress-true strain curve prediction method (TSS model) and fracture toughness prediction method (H3T model) after long term service were established. These prediction methods are used for the evaluation on the plant life management of nuclear power plants in Japan.

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