Effect of Immersion in Water or Alkali Solution on the Structures and Properties of Epoxy Resin

Glass fiber-reinforced polymer (GFRP) composites are promising composites often utilized in coastal infrastructure or used as an alternative to steel reinforcement in seawater sea sand concrete due to their excellent corrosion resistance. Understanding the degradation mechanism of GFRP in corrosion environments is significant for improving the long-term performance of GFRP materials. This paper presented the influences of seawater content and temperature on the properties of GFRP composites using the molecular dynamics method. The simulation results were validated by existing experiments on mechanical properties, interlaminar strength, and microstructures of an accelerated aging test of GFRP. The calculation results indicated that when seawater content of the matrix increased from 0% to 9.09% at 298 K, Young’s modulus, shear modulus, and bulk modulus decreased 46.72%, 53.46%, and 41.75%, respectively. The binding energy of GFRP composites with seawater content of 2.15% at 353 K was 26.46% lower than that of unconditioned GFRP at 298 K. It revealed that the higher seawater content and temperature accelerated the degradation of the GFRP composites. The investigation provided a comprehensive understanding of the degradation mechanism of GFRP in seawater environments and provided a basis for the durability design of GFRP composites.

“…The models were validated considering the test data. Wang et al revealed that the plasticization of the resin matrix led to the appearance of micropores and microcracks [ 43 ].…”

Section: Resultsmentioning

confidence: 99%

Effects of Seawater Environment on the Degradation of GFRP Composites by Molecular Dynamics Method

Zhang

Deng

2022

“…For epoxy resin, it has excellent mechanical properties, convenient molding process and better bonding strength with the other medium, which can be used in the resin matrix, interface adhesive and coating for the repairing and reinforcing of engineering structures [ 6 , 7 , 8 ]. However, the three-dimensional network structure of epoxy resin leads to the poor fracture toughness, which is easy to bring about the cracks and concentration under the complex load conditions, resulting in fatigue damage and ultimate failure [ 9 , 10 , 11 ]. At the same time, the hydroxyl groups in the molecular structure are easy to react with water molecules, which leads to the durability degradation, such as the hydrolysis and plasticization [ 12 , 13 , 14 , 15 ].…”

Section: Introductionmentioning

confidence: 99%

Effect of the Addition of Thermoplastic Resin and Composite on Mechanical and Thermal Properties of Epoxy Resin

Hailatihan

et al. 2022

Self Cite

When the thermoplastic composites reach the service limits during the service, the recovery and utilization are the key concerns. Meanwhile, the improvement of strength, toughness and durability of epoxy resin is the effective method to prolong the service life of materials and structures. In the present paper, three kinds of thermoplastic resins (polypropylene-PP, polyamide 6-PA6 and polyether-ether-ketone-PEEK) and composites (carbon fiber-PEEK, glass fiber-PA6 and glass fiber-PP) were adopted as the fillers to reinforce and toughen the epoxy resin (Ts). The mechanical, thermal and microscopic analysis were conducted to reveal the performance improvement mechanism of Ts. It can be found that adding thermoplastic resin and composite fillers at the low mass ratio of 0.5~1.0% brought about the maximum improvement of tensile strength (7~15%), flexural strength (7~15%) and shear strength (20~30%) of Ts resin. The improvement mechanism was because the addition of thermoplastic fillers can prolong the cracking path and delay the failure process through the load bearing of fiber, energy absorption of thermoplastic resin and superior interface bonding. In addition, the thermoplastic composite had better enhancement effect on the mechanical/thermal properties of Ts resin compared to thermoplastic resin. When the mass ratio was increased to 2.0~3.0%, the agglomeration and stress concentration of thermoplastic filler in Ts resin appeared, leading to the decrease of mechanical and thermal properties. The optimal addition ratios of thermoplastic resin were 0.5~1.0% (PEEK), 1.0~2.0% (PA6) and 0.5~1.0% (PP) to obtain the desirable property improvement. In contrast, the optimal mass ratios of three kinds of composite were determined to be 0.5~1.0%. Application prospect analysis indicated adding the thermoplastic resin and composite fillers to Ts resin can promote the recycling and reutilization of thermoplastic composites and improve the performance of Ts resin, which can be used as the resin matrix, interface adhesive and anti-corrosion coating.

“…The above analysis is important to reveal the effect of water types on the performance degradation of epoxy and its composites. Wang et al [ 30 ] found the micropore and free volume space in epoxy gradually increased after the immersion. The tensile strength decreased to the lowest point after the immersion in water and alkali for one month, and the decrease percentages at 20 °C and 60 °C water or 60 °C alkali solution were 24%, 28% and 22%, respectively.…”

Section: Introductionmentioning

confidence: 99%

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

Zhou

Tian

et al. 2022

Self Cite

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.