Evaluation of fracture toughness of epoxy polymer composite incorporating micro/nano silica, rubber and CNTs

Effect of Adding Silver-Doped Carbon Nanotube Fillers to Heat-Cured Acrylic Denture Base on Impact Strength, Microhardness, and Antimicrobial Activity: A Preliminary Study

Poly (methyl methacrylate) (PMMA), is an acrylic polymer substance that is mostly used for denture base applications. The purpose of this laboratory study was to investigate the effect of adding 0.05 wt.% Ag-doped carbon nanotubes (CNT) to PMMA-based (PMMA and MMA) denture base material on the impact strength, microhardness, and antimicrobial activity. A total of 60 heat-cured acrylic resin specimens were prepared. The specimens were randomly divided into two main groups (n = 30/group), according to the powder used: (a) control group, using heat-cured PMMA; (b) treatment group, using a powder prepared by blending 0.05 wt.% silver-doped CNT nanoparticles with heat-cured PMMA. The impact strength, microhardness and anticandidal activity for each group were assessed via the Charpy, Vickers and agar diffusion tests, respectively (n = 10/test for each subgroup). Data were analyzed using independent-sample t-tests (p ≤ 0.05). The results of the impact strength test revealed that the treated heat-cured PMMA-MMA with Ag-doped CNT (2.2 kJ/mm²) was significantly higher than that of the control heat-cured PMMA (1.6 kJ/mm²). Similarly, the Vickers microhardness of the treatment group (52.7 VHN) was significantly higher than that of the control group (19.4 VHN). Regarding the agar diffusion test, after 24 h of incubation, the treated heat-cured PMMA with the Ag-doped CNT exhibited significantly higher anticandidal activity than that of the control group. Therefore, Ag-doped carbon nanotubes could be considered as promising fillers for the dental heat-cured acrylic resin to improve the resistance of the resultant denture against sudden fractures, scratching, and candida invasion.

Investigation of Curing Mechanism and Mechanical Properties of Polypropylene/Aliphatic Epoxy Composites

Temperature-sensitive cure kinetics based on bisphenol A oligomeric diglycidyl ether and branching diphenylmethane di-isocyanate, polymer aliphatic or lower molecular weight aromatic amines, and polypropylene and epoxy composites were examined. Polypropylene networks are formed initially, followed by amine hardeners interfering with epoxy oxirane rings to frame linear oligomers. Finally, the system is formed by a reaction between amines obtained in the second phase and epoxy oxirane rings during the curing step. This three-stage treatment was illustrated. The activation energy was calculated using the Flynn-Wall-Ozawa and Kissinger-Akahira-Sunose isoconversational approaches to cure degree. The Ea-to- $\alpha$ correlation was determined using these approaches, revealing that the research curing systems exhibited autocatalytic effects. Among the materials studied, compounds with low molecular weight aromatic amines had the strongest and longest-lasting tensile characteristics. There are numerous advantages to slow curing and discrete stages of composite creation, including better mechanical properties.