Comparative Study of Durability Behaviors of Thermoplastic Polypropylene and Thermosetting Epoxy Exposed to Elevated Temperature, Water Immersion and Sustained Bending Loading

Abstract

The long-term degradation of epoxy as the matrix and adhesive serviced in harsh environments plays a key role in engineering applications. Understanding how to improve the toughness and durability of epoxy through reasonable material replacement and design is significant to prolong the service life of engineering structures. In the present paper, thermoplastic polypropylene and thermosetting epoxy were exposed in a coupling environment of elevated temperature, water immersion and sustained bending loading. The evolutions of mechanical and thermal properties were further analyzed and compared. Long-term life prediction was conducted to evaluate the corrosive resistances of polypropylene and epoxy. It can be found that polypropylene has better hydrophobic behavior compared to epoxy. At 80 °C, the ratios of the diffusion coefficient and saturated water uptake between the two matrices were 114.4 and 2.94. At the longest immersion time of 90 days, the degradation percentages of tensile strength were 4.7% (40 °C), 7.5% (60 °C) and 8.8% (80 °C), respectively, which had the higher strength retention (>90%). The maximum strength increase in the multiples of polypropylene/epoxy and polypropylene/polyurethane was 1.95 and 1.75, respectively. The bending loading led to a maximum increase in tensile strength (~1.47%) owing to the oxygen isolation effect. The degradation mechanism was attributed to the active functional groups from the production process reacting with oxygen, resulting in the fracture of the local chain segment. By comparison, water molecules reacted with the hydroxyl groups or interrupted the intermolecular Van der Waals force/hydrogen bond of the epoxy, resulting in irreversible hydrolysis and property degradation. Through the comparison, it can be found that polypropylene and its composites have outstanding properties compared to epoxy, which can make them achieve great application prospects in engineering applications when considering a complex service environment.

Online characterization of moisture transport in a high-performance carbon fiber-reinforced thermoplastic composite at high temperatures: Identification of diffusion kinetics

“…In equation (10), D 1 and M ∞,1 are interdependent. This interdependence is also valid for D 2 and M ∞,2 .…”

“…[5,6,7]. Although high-performance TPCs generally uptake less water than high-performance thermoset matrix composites [8,9,10], the effect of moisture is not negligible. To avoid this detrimental effect of moisture, understanding of the moisture (de)sorption mechanisms, especially the moisture diffusion kinetics in the material is required.…”

Potential Applications of Different Forms of Recycled Plastics as Construction Materials—A Review

“…Thermoplastics can be reformed in to any shape after heating and are referred to as recyclable due to their reversable nature [10]. However, thermosetting plastics undergo chemical changes upon heating that result in a hardened rigid material, a process referred to as polymerization [11]. This irreversible behavior leads to their finalized form, which cannot be softened or reshaped without significant degradation [12].…”

Numerical Modeling of Damage Caused by Seawater Exposure on Mechanical Strength in Fiber-Reinforced Polymer Composites

“…Extensive research has been conducted to evaluate the effects of hostile environments on composite materials [ 14 , 15 , 16 , 17 , 18 , 19 , 20 ]. The absorption of water is detrimental to the mechanical properties of FRP composites, since it affects the resin matrix by plasticization and also deteriorates the matrix–fiber interface [ 21 , 22 , 23 , 24 ].…”