Abstract The demands for dental materials continue to grow, driven by the desire to reach a better performance than currently achieved by the available materials. In the dental restorative ceramic field, the structures evolved from the metal-ceramic systems to highly translucent multilayered zirconia, aiming not only for tailored mechanical properties but also for the aesthetics to mimic natural teeth. Ceramics are widely used in prosthetic dentistry due to their attractive clinical properties, including high strength, biocompatibility, chemical stability, and a good combination of optical properties. Metal-ceramics type has always been the golden standard of dental reconstruction. However, this system lacks aesthetic aspects. For this reason, efforts are made to develop materials that met both the mechanical features necessary for the safe performance of the restoration as well as the aesthetic aspects, aiming for a beautiful smile. In this field, glass and high-strength core ceramics have been highly investigated for applications in dental restoration due to their excellent combination of mechanical properties and translucency. However, since these are recent materials when compared with the metal-ceramic system, many studies are still required to guarantee the quality and longevity of these systems. Therefore, a background on available dental materials properties is a starting point to provoke a discussion on the development of potential alternatives to rehabilitate lost hard and soft tissue structures with ceramic-based tooth and implant-supported reconstructions. This review aims to bring the most recent materials research of the two major categories of ceramic restorations: ceramic-metal system and all-ceramic restorations. The practical aspects are herein presented regarding the evolution and development of materials, technologies applications, strength, color, and aesthetics. A trend was observed to use high-strength core ceramics type due to their ability to be manufactured by CAD/CAM technology. In addition, the impacts of COVID-19 on the market of dental restorative ceramics are presented.

Abstract Prolonged exposure to environmental conditions such as ultraviolet radiation, humidity, and temperature, to which carbon fiber-reinforced thermoplastic polymer components are exposed during their service life, can lead to significant changes in mechanical, physical, and chemicals properties, and can often be irreversible, resulting in premature component failure. This study presents the influence of accelerated weathering exposure times (400 h, 800 h, and 1200 h) on the mechanical, thermal, and structural properties of carbon fiber (CF)/polyamide 6 (PA6) laminates. Analyses of composite surfaces were carried out using microscopy and contact angle measurements, which indicated that the factors of exposure to accelerated only affected the surface of the composites, showing signs of the beginning of degradation. The tensile strength (609 MPa ± 10 MPa) and interlaminar shear strength (27 MPa ± 0.9 MPa) did not present significant changes, showing that the reinforcement, the matrix, and the interface remained stable after exposure to accelerated.

Abstract Polymer compatibilizer agents are crucial for industrial materials development. Compatibilizer agents may be prepared by melt-grafting in the reactive extrusion process which is cheaper and environmentally friendly. Maleic anhydride-grafted acrylonitrile-butadiene-styrene (ABS-g-MA) has emerged as a relevant compatibilizer agent for immiscible blends, like polycarbonate (PC)/ABS. In this work, ABS-g-MA was prepared by a simple reactive extrusion process using ABS, maleic anhydride (MA) and benzoyl peroxide (BPO). The MA:BPO ratios of 1:0.5 and 1:1 varying the content of MA by 1, 2 and 5 wt% were investigated. The grafting reaction was confirmed through Fourier transform infrared spectroscopy (FT-IR), grafted degree (GD%), thermal and rheological analysis. The effectiveness of the compatibilizer agent was evaluated in PC/ABS blends (70/30 and 85/15 blend ratios). The addition of 5 wt% of ABS-g-MA (5 MA:2.5 BPO) in the PC/ABS blends promoted an expressive reduction of ABS domain sizes and better dispersion in the PC matrix.

In this study, chitosan hydrogels were produced with 0, 2, 4 and 6 wt% of cellulose nanocrystals (CNC) using hexahydrate zinc nitrate (Zn(NO3)2.6H2O) as a catalyst for chitosan crosslinking reaction. CNC´s size was estimated by dynamic light scattering (DLS) and surface charge by zeta potential. Hydrogels were characterized by rotational rheometer, swelling test, uniaxial compression test, in vitro degradation, scanning electron microscopy (SEM) and microtomography. Results showed that zinc nitrate and CNC addition did not influence mechanical properties, degradation, and morphology of the hydrogels. However, zinc nitrate decreased 36.54% of the gel time and 41.37% of the swelling degree, and increased the crosslinking degree of the chitosan hydrogels, proving not only its catalytic effect but also its participation in the crosslinking reaction. Porosity was slightly reduced after addition of zinc nitrate and incorporation of CNC. In the mechanism of crosslinking reaction, a competition between CNC and zinc nitrate was observed.

A compatibilizer agent was successfully produced by grafting maleic anhydride (MA) to poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) chains on a reactive processing by mechanical mixing, using a mixture of PHBV, MA and dicumyl peroxide (DCP) as initiator. The resulting PHBV grafted MA (PHBV-g-MA) was characterized by Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and gel permeation chromatography (GPC), and its properties were compared to neat PHBV. FTIR showed an absorption band at 699 cm-1 for PHBV-g-MA, related to CH group of grafted anhydride ring. The initial thermal degradation temperature of the compatibilizer agent was reduced when compared to neat PHBV. DSC analysis showed that after grafting MA onto PHBV the crystallization temperature was about 20ºC higher than neat PHBV, and the degree of crystallinity was increased. GPC analysis showed that MA when grafted onto PHBV led to a reduction of molecular weight and polydispersity.