Investigation of Degradation of Composites Based on Unsaturated Polyester Resin and Vinyl Ester Resin

Evaluation of filler activation for sustainable FRP composite by studying properties, mechanism, and stability

The aim is to develop new fiber-reinforced polymer (FRP) water pipe by activating fiber glass (FG) by vinyltriethoxysilane (VS) getting vinylsilane-activated FG (AFG) for filling vinylester (VE) via continuous winding to make a novel VE-AFG composite. The novelty of this work is the activation of fiber glass by vinylsilane as a single filler in vinylester and compounding them via a two-dimensional continuous winding process for the first time. The crosslinking occurred in the AFG/VE/curing agent system after activation. The activated composites increased thermal stability; 25% VE-AGF increased the degradation temperatures at 10%, 25%, and 50% weight loss by 73.3%, 10%, and 7.2%. With the activated 20% composite, values of axial strength, hoop strength, and hardness were developed by 6.3%, 2%, and 8.7%, respectively. The decay resistance to different microorganisms was increased with VE-AFG composites as a result of a sharp decrease in biodegradability percentages. The activated composites are stable toward water absorption; the least percentage was recorded by 25% VE-AFG, which minimized the water absorptivity by more than 62%. The reported characterization sentence approves enhancement of thermal, physical, and mechanical stability of sustainable vinylester-fiber glass composites manufactured by continuous winding; this is recommended for application in water pipe systems.

Fracture Performance Study of Carbon-Fiber-Reinforced Resin Matrix Composite Winding Layers under UV Aging Effect

There is limited research on the fracture toughness of carbon-fiber-reinforced polymer (CFRP) materials under accelerated UV aging conditions. In this study, the primary focus was on investigating the influence of varying durations of ultraviolet (UV) irradiation at different temperatures on the Mode I, Mode II, and mixed-mode fracture toughness of CFRP laminates. The results indicate that with increasing UV aging duration, the material's Mode I fracture toughness increases, while Mode II fracture toughness significantly decreases. The mixed-mode fracture toughness exhibits an initial increase followed by a subsequent decrease. Furthermore, as the aging temperature increases, the change in the fracture toughness of the material is more obvious and the rate of change is faster. In addition, the crack expansion of the composite layer of crack-containing Type IV hydrogen storage cylinders was analyzed based on the extended finite element method in conjunction with the performance data after UV aging. The results reveal that cracks in the aged composite material winding layers become more sensitive, with lower initiation loads and longer crack propagation lengths under the same load. UV aging diminishes the overall load-bearing capacity and crack resistance of the hydrogen storage cylinder, posing increased safety risks during its operational service.

A Comparison Study on Toughening Vinyl Ester Resins Using Different Nanocarbon Materials

This study aims to comprehensively compare and evaluate the toughening effects of different nanocarbon materials on vinyl ester resins. Four typical nanocarbon materials, including graphene, graphene oxide (GO), single-walled carbon nanotubes (SWCNTs), and multi-walled carbon nanotubes (MWCNTs), were used as reinforcing fillers for vinyl ester resins. These four nanocarbon materials were dispersed in the vinyl ester resin matrix by the combination of high-speed stirring and probe sonication, and their dispersion states were observed with optical microscopy. The effects of incorporating different nanocarbon materials on the viscosities, thermal properties, tensile properties, and fracture toughness of the resulting modified vinyl ester resins were systematically investigated. The results indicate that the four nanocarbon materials show enhanced toughening effects on the vinyl ester resin in the sequence of SWCNTs, GO, MWCNTs, and graphene. Compared with the control resin, the modified vinyl ester resin containing 0.2 wt% graphene shows 45% and 54% enhancements in the critical stress intensity factor (KIC) and critical strain energy release rate (GIC), respectively. The incorporation of the four nanocarbon materials has almost no effect on the glass transition temperatures of the resulting modified vinyl ester resins. This study provides valuable insights into the selection of nanocarbon additives for enhancing the toughness of vinyl ester resins.

Properties of Eco-Friendly Composites Based on Post-Consumer Recycled Resin Filled with Walnut Shell Powder

Increased demand for environmentally friendly materials resulted in a worldwide interest in manufacturing composite materials from agricultural wastes. Thus, this paper presents the results of research on the synthesis of eco-friendly composites and their properties. For their preparation, unsaturated polyester resin based on post-consumer recycled poly (ethylene terephthalate) was filled with walnut (Júglans régia L.) shell powder. After the filler incorporation, the deterioration of gloss and mechanical properties were observed. The flexural strength and modulus are significantly affected by the filler amount. Distilled water, 1% sodium hydroxide, toluene, and acetone were used as solvents in the chemical resistance test. Changes to the structure and properties of composites after 49 days of immersion in solvents were investigated. The immersion in water has no significant effect on the pure resin, but for its composites, the plasticizing effect of water was observed. The results show that all specimens show resistance toward toluene. In acetone, the resin and its composite shrink and fall into pieces, but the most destructive is an alkaline environment. After the immersion test, a huge increase in mass and a deterioration of gloss and mechanical properties were observed.

Coordination Compound (2,3,5-Triphenyltetrazolium)2[CuBr4] as Catalyst for the Curing Process of Epoxy Vinyl Ester Binders

This article presents a study on the synthesis and catalytic properties of copper complex (TPhTz)₂[CuBr₄] (here TPhTz is 2,3,5-triphenyltetrazolium). The obtained complex was characterized by various spectroscopic methods. The catalytic properties of the complex were evaluated in the curing of an epoxy vinyl ester system and their effectiveness was compared with that of cobalt octoate (its synonyms are known as Co(Oct)₂, cobalt(II) 2-ethylhexanoate, cobalt isocaprylate, etc.). The catalyst was added at an amount of 2 w.%. The results showed that a 8 w.% solution of the complex provides catalytic properties with an activation energy of 54.7 kJ/mol, which is 25.2 kJ/mol higher than a standard curing system with Co(Oct)₂. Thus, the solution of (TPhTz)₂[CuBr₄] in THF/DMSO accelerates the initiator decay process at room temperature, but for a longer time. The authors suggest that the curing mechanism may be accelerated by the appearance of (TPhTz)₂[Cu^IBr₃] and free bromine in the system. A strength test of fiberglass-reinforced plastic revealed that the addition of this complex did not lead to a decrease in flexural strength and hardness. Thus, use of the complex allowed for the production of polymer composite products using vacuum-assisted resin transfer molding where an extended injection time was needed.

Assessment Study on the Solvent Resistance of Low-Density Polyethylene with Pumpkin Seed Hulls

When designing products that are made of composite materials and that contain natural fillers, it is particularly important to consider the long-term exposure of these materials to caustic liquids and substances (concentrated acids, bases), and to ensure that these products meet strict requirements for reliability and operational safety. This study investigated the effects of different solvents on the mass, mechanical, thermal, surface, and structural properties of polymer composites containing natural fillers in the form of pumpkin seed hulls. Experiments were conducted using four different filler contents (5, 10, 15, and 20 wt%) and grain sizes ranging from 0.2 to 0.4 mm and 0.6 to 0.8 mm. Hybrid injection-moulded pieces were immersed in distilled water (H₂O), 1% NaOH solution, acetone (C₃H₆O), and toluene (C₇H₈) for 84 days. After that, their mechanical and thermal properties as well as their structure geometries were analysed statistically. Changes in the properties of the tested composite materials were assessed depending on the solvent type, and the statistical significance of these changes were determined. The results showed that the nature of degradation depended on the applied solvent type. It was observed that the polymer matrix of the toluene-immersed samples absorbed the liquid to a significant extent first and then underwent a gradual degradation with time. In contrast, the samples immersed in water showed a slight increase in their mass. It was found that all tested properties of the composite samples deteriorated irrespective of the solvent type.