Optimization of Alkali Treatment Conditions of Ramie Fabrics Using Box­Behnken Method.

Ramie is a widely used plant fiber for making textiles and reinforcement in biodegradable composites. Pretreating cellulosic fibers with alkali before producing composites is increasingly used to enhance adhesion with polymeric resin. In this work, response surface methodology (RSM) based on the Box-Behnken technique was utilized to investigate the impact of independent variables on ramie fabric characteristics and determine the optimal treatment condition. The impact of alkali concentration, treatment time, and temperature on the breaking load and elongation at break of woven ramie fabrics were evaluated using Design-Expert software, which established the design matrix and analyzed the experimental data employing numerical and graphical optimization methods. Moreover, the impact of alkali treatment conditions on the surface morphology, structural change of ramie fabrics, and thermal properties was investigated. Based on the analysis of variance (ANOVA) results, the suggested quadratic models can adequately predict the breaking load and elongation at break of the ramie woven fabrics within the range of conditions applied in this investigation. The RSM revealed that an alkali concentration of 6.12%, a treatment time of 30 min, and a temperature of 39.13°C resulted in an optimum treatment condition with a breaking load of 518.28 N and elongation at break of 23.36%.

Polyurethane Impregnation for Improving the Mechanical and the Water Resistance of Polypropylene-Based Textiles.

Commercial waterborne polyurethane (PU) dispersions, different in chemistry and selected on the basis of eco-friendly components, have been applied to a common polypropylene (PP)-based woven fabric. Impregnation has been chosen as a textile treatment for improving the features of basic technical textiles in light of potential applicability in luggage and bag production. The effect of drying method, performed under conditions achieved by varying the process temperature and pressure, on the features of the treated textiles, has been verified. The prepared specimens were characterized in terms of mechanical behavior (tensile, tear and abrasion resistance) and water resistance (surface wettability and hydrostatic pressure throughout the treated textiles). The experimental results suggest an incremental improvement of the tensile features for all the investigated specimens. For tear strength, no augmentation compared to that of the neat textile, could be verified as a consequence of polyurethane treatment. Remarkable improvements of abrasion resistance were displayed for all the impregnated PP textiles. Benefits in water resistance could be attributed to the presence of hydrophobic PU in the textile weaving of the PP samples. The ultimate improvement in water resistance was dependent on drying conditions.

In Vitro Analysis of the Fracture Resistance of CAD/CAM Denture Base Resins.

Computer-aided design and computer-aided manufacturing (CAD/CAM) denture base manufacturers claim to produce their resin pucks under high heat and pressure. Therefore, CAD/CAM dentures are assumed to have enhanced mechanical properties and, as a result, are often produced with lower denture base thicknesses than conventional, manually fabricated dentures. The aim of this study was to investigate if commercially available CAD/CAM denture base resins have more favourable mechanical properties than conventionally processed denture base resins. For this purpose, a series of three-point bending tests conforming to ISO specifications were performed on a total of 80 standardised, rectangular CAD/CAM denture base resin specimens from five different manufacturers (AvaDent, Baltic Denture System, Vita VIONIC, Whole You Nexteeth, and Wieland Digital Dentures). A heat-polymerising resin and an autopolymerising resin served as the control groups. The breaking load, fracture toughness, and the elastic modulus were assessed. Additionally, the fracture surface roughness and texture were investigated. Only one CAD/CAM resin showed a significantly increased breaking load. Two CAD/CAM resins had a significantly higher fracture toughness than the control groups, and all CAD/CAM resins had higher elastic moduli than the controls. Our results indicate that CAD/CAM denture base resins do not generally have better mechanical properties than manually processed resins. Therefore, the lower minimum denture base thicknesses should be regarded with some caution.