Abstract
In the present paper, a vinyl ester (VE) resin, potentially used as a resin matrix for fiber-reinforced polymer (FRP) composite sucker rods in oil drilling, FRP bridge cables, or FRP marine structures, was investigated on its resistance to water and alkaline solution immersion in terms of water uptake, hydrothermal expansion, and mechanical properties. A two-stage diffusion model was applied to simulate the water uptake processes. Alkaline solution immersion led to a slightly higher mass loss (approx. 0.4%) compared to water immersion (approx. 0.23%) due to the hydrolysis and leaching of uncured small molecules (e.g., styrene). Water immersion caused the expansion of VE plates monitored with Fiber Bragg Grating (FBG). With the same water uptake, the expansion increased with immersion temperatures, which is attributed to the increased relaxation extent of the resin molecular networks. Although an obvious decrease of the glass transition temperatures (Tg) of VE due to water immersion (5.4 to 6.1 °C/1% water uptake), Tg can be recovered almost completely after drying. Tensile test results indicate that a short-term immersion (less than 6 months) enhances both the strength and elongation at break, while the extension of the immersion time degrades both the strength and elongation. The modulus of VE shows insensitive to the immersion even at elevated temperatures.
Highlights
Fiber-reinforced polymer (FRP) composites have been widely accepted as an alternative structural material to steel in oil drilling in recent years [1,2]
The present paper aims to investigate the durability of vinyl ester (VE)
It is worth noting that the constant k can be considered related to both the relaxation of the resin network and the hydrolysis of the resin or leaching of uncured small molecules, i.e., styrene, during immersion [27]
Summary
Fiber-reinforced polymer (FRP) composites have been widely accepted as an alternative structural material to steel in oil drilling in recent years [1,2]. VE resin is not considered to be appropriate for carbon fiber-reinforced FRPs due to a poor adhesion to carbon fibers Both the resin matrix and the fiber–resin bonding are crucial to the mentioned applications. VE is considered to have more and more potentials in various engineering applications (e.g., sucker rods for oil drilling, civil engineering, bridge cables, etc.) exposed to harsh environments, less works have been done on the long-term durability in various conditions compared to the epoxy resin and VE-based FRPs. In view of this, the present paper aims to investigate the durability of VE resin immersed in a water or alkaline solution in terms of the water absorption, mechanical properties, and dynamic thermal mechanical properties. The study will help understand the durability of VE-based FRPs and will benefit the acceptance of VE in various structural applications encountering harsh environments
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