Reinforcement using undoped carbon quantum dots (CQDs) with a partially carbonized structure doubles the toughness of PVA membranes.

Nano-carbon-reinforced polymer composites have gained much consideration in functional applications due to their attractive mechanical strength and cost-effectiveness. The surface chemistry and associated mechanical strength of carbon nanotubes (CNTs), graphene, and other carbon derivative-based nanocomposites are well understood. While CQDs are considered emerging carbon derivatives, their surface chemistry, unique physio-chemical properties, and dispersion behavior in polymers are yet to be explored. Therefore, in this work, CQDs with different structures were synthesized from lemon pulp and urea, and their rheology and mechanical strength were studied in the PVA matrix. The surface chemistry and structure of CQDs were controlled using different solvents and reaction temperatures, respectively. CQDs possessed a circular shape, with a size of <10 nm, having a suitable carbon core and functional groups, as confirmed by TEM and FTIR spectroscopy. The dynamic viscosity and particle size of PVA/CQDs films peaked at 4% inclusion due to the maximum crosslinking of U-CQDs with reinforcement at 180 °C. Compared with pure PVA, the optimized composite showed an 80% larger particle size with 67% better tensile strength at 4% U-CQDs concentration. In addition to enhanced mechanical strength, CQDs exhibited antibacterial activity in composites. These CQDs-reinforced PVA composites may be suitable for different functional textile applications (shape memory composites and photo-active textiles).

Correction: Carbon quantum dots (CQDs)-modified polymers: a review of non-optical applications.

Correction for 'Carbon quantum dots (CQDs)-modified polymers: a review of non-optical applications' by Zeeshan Latif et al., Nanoscale, 2024, 16, 2265-2288, https://doi.org/10.1039/D3NR04997C.

Carbon quantum dots (CQDs)-modified polymers: a review of non-optical applications.

Carbon quantum dots (CQDs) are a promising candidate to replace metal-based additives for polymer reinforcement and functionalization. Specifically, vast interest in CQDs for polymer functionalization stems from their cost effectiveness, sustainable organic precursors, and their non-toxicity. Although several reviews of optical devices based on CQDs have been reported, this mini-review covers the non-optical aspects of CQD-polymer composites. Applications of CQD-modified polymers for smart devices, mechanical reinforcement, textile surface-modification methods, membranes, protective coatings, and thermal resistance are summarized. The synthesis method of CQDs, their dispersion in a polymer matrix and the underlying mechanisms related to the enhanced performance of composites are outlined. Unlike nano-reinforcements, CQDs are self-stabilized and offer an extremely high surface area, which significantly alters the polymer properties at a 1-2% concentration. Finally, a comparative analysis of recent advances in CQD-polymer composites, their problems, and future directions are discussed.

Room Temperature Synthesized TiO2 Nanoparticles for Two-Folds Enhanced Mechanical Properties of Unsaturated Polyester.

Using of nano-inclusion to reinforce polymeric materials has emerged as a potential technique to achieve an upper extreme of specific strength. Despite the significant improvement of mechanical properties via nano-reinforcements, the commercial application of such nano-composites is still restricted, due to high cost and unwanted aggregation of nanoparticles in the polymer matrix. To address these issues, here we proposed a scalable and economical synthesis of TiO2 at low temperatures, resulting in self-dispersed nanoparticles, without any surfactant. As lower energy is consumed in the synthesis and processing of such nanoparticles, so their facile gram-scale synthesis is possible. The defect-rich surface of such nanoparticles accommodates excessive dangling bonds, serving as a center for the functional groups on the surface. Functional surface enables high dispersion stability of room temperature synthesized TiO2 particles. With this motivation, we optimized the processing conditions and concentration of as-synthesized nano-particles for better mechanical properties of unsaturated polyester (UP) resin. The composite structure (UP-TiO2) showed nearly two folds higher tensile, flexural, and impact strength, with 4% content of nanoparticles. Characterization tools show that these better mechanical properties are attributed to a strong interface and superior dispersion of nanoparticles, which facilitate better stress distribution in the composite structure. In addition, the crack generation and propagation are restricted at a much smaller scale in nanocomposites, therefore significant improvement in mechanical properties was observed.

Mode I Fatigue of Fibre Reinforced Polymeric Composites: A Review.

Composites are macroscopic combinations of chemically dissimilar materials preferred for new high-tech applications where mechanical performance is an area of interest. Mechanical apprehensions chiefly include tensile, creep, and fatigue loadings; each loading comprises different modes. Fatigue is cyclic loading correlated with stress amplitude and the number of cycles while defining the performance of a material. Composite materials are subject to various modes of fatigue loading during service life. Such loadings cause micro invisible to severe visible damage affecting the material's performance. Mode I fatigue crack propagates via opening lamina governing a visible tear. Recently, there has been an increasing concern about finding new ways to reduce delamination failure, a life-reducing aspect of composites. This review focuses on mode I fatigue behaviours of various preforms and factors determining failures considering different reinforcements with respect to fibres and matrix failures. Numerical modelling methods for life prediction of composites while subjected to fatigue loading are reviewed. Testing techniques used to verify the fatigue performance of composite under mode I load are also given. Approaches for composites' life enhancement against mode I fatigue loading have also been summarized, which could aid in developing a well-rounded understanding of mode I fatigue behaviours of composites and thus help engineers to design composites with higher interlaminar strength.