Adhesive characteristics and bonding performance of phenol formaldehyde modified with phenol-rich fraction of crude bio-oil

Commercial phenol–formaldehyde (PF) adhesive was gradually substituted by increasing amount of the phenol-rich fraction (PRF) of crude bio-oil up to 40 wt%. The effect of substitution level of the PRF on the chemical, curing, morphological scanning electronic microscope (SEM), and bonding characteristics of the PF adhesive was determined. The tensile-shear strength of single lap-joint wood specimens bonded with the modified PF adhesives was investigated under indoor and outdoor exposure conditions. The chemical composition of the PRF was investigated using some chromatographic and spectroscopic techniques. Further structural analysis of PRF-modified PF adhesives was determined using Fourier transform infrared spectroscopy (FTIR). The PRF resol had a similar molecular structure to commercial pure phenol resol adhesive. The PRF could be partially substitute for the petroleum-based phenol in commercial PF adhesives with inexpensive phenols derived from lignocellulosic wastes.     

Effect of 2% chlorhexidine gluconate cavity disinfectant on microtensile bond strength of tooth-coloured restorative materials to sound and caries-affected dentin

This study evaluated the effect of 2% chlorhexidine gluconate-based cavity disinfectant (CHX) on the microtensile bond strength (μTBS) of glass ionomer, resin-modified glass ionomer and packable resin composite to sound and caries-affected dentin. Sound and occlusal caries-affected human third molars (N?=?36, n?=?3 per group) were randomly divided into three experimental groups to receive one of the following restorative materials. (a) Glass ionomer (Ketac Molar, 3 M ESPE; GI), (b) resin-modified glass ionomer (Vitremer, 3 M ESPE; RMGI) and (c) packable resin composite (Surefil, Dentsply; PRC) with a bonding agent (Prime Bond NT, Dentsply De Trey). Caries was removed using a caries-detecting dye (Caries Detector, Kuraray Medical Ltd.) and flat dentin surfaces were achieved by finishing up to 1200-grit silicon carbide abrasive. Half of the teeth in each group received 2% CHX (Consepsis, Ultradent). Dentin surfaces were built-up with the respective materials incrementally and were sectioned with a slow-speed saw into multiple beams. The beams were subjected to μTBS test (0.5 mm/min) in a Universal Testing Machine. The data were analysed using two-way analysis of variance and Tukey’s tests. For each restorative material, μTBS results were not affected by the application of CHX (p?>?0.05) on both sound and caries-affected dentin (p?>?0.05). PRC in combination with the corresponding bonding agent showed significantly higher results (p?<?0.05) than those of GI and RMGI, on sound and caries-affected teeth, respectively. Cohesive failure in dentin was not observed in any of the groups. The use of 2% chlorhexidine-based cavity disinfectant did not impair the adhesion of the restorative materials tested to either sound or caries-affected dentin.     

Synthesis of bis[(4-hydroxyethoxy)phenyl]sulfone containing urethane acrylates and their applications

UV-curing processes are used in industrial applications because of their advantages such as high speed applications and solvent-free formulations at ambient temperature. UV-curable sulfone containing polyurethane acrylates were synthesized from bis[(4-hydroxyethoxy)phenyl]sulfone (BHEPS), polyols, isophorone diisocyanate (IPDI) and 2-hydroxyethyl methacrylate (HEMA). The polyurethane acrylates characterized with ¹H NMR and FT-IR spectroscopies. The UV-cured coatings and films were formulated with polyurethane acrylates, reactive diluents such as dipropyleneglycol diacrylate (DPGDA), 1,6-hexanediol diacrylate (HDDA) and photoinitiator. The water wettability of the UV-cured films was investigated by measuring contact angle. Sulfone containing polyurethane acrylates increase mechanical properties such as pendulum hardness, pencil hardness, tensile strength, and e-modulus values. These mechanical properties and chemical-solvent resistance may have been strongly dependant on the sulfone content and crosslinking density.     

Tomato powder impedes the development of azoxymethane‐induced colorectal cancer in rats through suppression of COX‐2 expression via NF‐κB and regulating Nrf2/HO‐1 pathway

Cancer is one of the leading causes of death worldwide. Since dietary factors have been connected to a reduced risk of a diversity of human cancers, in this study we investigated the effects of tomato powder (TP) on the development of azoxymethane (AOM)‐induced colorectal cancer in Wistar rats, and possible mechanism(s) by which TP shows its chemopreventive activity. Here we show that TP added to feed at 5% rate decreases the rate of aberrant crypt foci (ACF) and reduces the development of adenocarcinoma and growth of AOM‐induced colorectal cancer in rats. In addition, we demonstrate that TP supplementation shows its chemopreventive activities through inhibition of cyclooxygenase‐2 (COX‐2) expression via NF‐κB pathway and promotion of apoptosis, as well as regulating Nrf2/HO‐1 signaling pathway in colorectal tissue of AOM‐treated rats. Our findings identify an intimate connection between dietary supplementation of TP and the decreased risk of colorectal cancer in rats, and suggest that consumption of TP would be a natural candidate for the prevention of colorectal cancer in men.     

Influence of laser parameters in surface texturing of polyphenylene sulfide composites

Creating dimples at the ideal geometries to enhance the tribological properties of the polyphenylene sulfide (PPS) composite surface is the principal purpose of this study. In this manner, the effects of focus position (FP), pulse number (PN), and energy used for the making dimple geometry were investigated. In the ablation process, Nd:YAG laser with 1064 nm wavelength was used. Optimum laser process parameters were intended to obtain the largest ratio of dimple depth to width, circular dimples with a minimum ratio of molten zone diameter to spot size. The most effective parameters for obtaining dimple of desired properties are pulse energy (PE) with 60.64%, pulse duration (PD) with 55.61%, and FP with 55.94% for aspect ratio, circularity, and ratio of the diameter of the dimple to the spot size, respectively. In order to achieve a high aspect ratio or good circularity or minimum molten zone-to-spot size ratio, Taguchi optimization predicted the laser parameters. In the confirmation experiment with the proposed parameters, the highest aspect ratio was obtained as 2.05, the best circularity was obtained as 1.05, and minimum molten zone-to-spot size ratio was obtained as 1.073. Using the Taguchi method, accurate results were found with less experimentation. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47976.     

Corrosion,Wear and Mechanical Properties of Boron Added Cast 304 Stainless Steel

Protection of Metals and Physical Chemistry of Surfaces - The main objective of this research was to examine the effect adding B at 0, 100, 170 ppm had on the mechanical properties, wear and...     

Thermal behavior and shape memory properties of PCL blends film with PVC and PMMA polymers

Iranian Polymer Journal - Shape memory polymers have attracted extensive attention attributable to their characteristics and abundant applications. In this study, shape memory behavior and...     

Synthesis and characterization of boron-acrylate/Santa Barbara Amorphous-15 polymer composite

In the present work, boron-acrylate/Santa Barbara Amorphous (SBA)-15 polymer composite was synthesized using free radical polymerization method. Firstly, SBA-15 was functionalized with 3-(trimethoxysilyl)propyl methacrylate to obtain chemically bonded boron acrylate (BAc) polymer on the SBA-15 surface. The structural analysis was evaluated via Fourier-transform infrared spectroscopy and solid-state nuclear magnetic resonance ¹³C. Samples were also characterized by using scanning electron microscopy, X-ray powder diffraction, N₂ adsorption/desorption and thermogravimetric analysis. In order to examine the BAc polymers in the mesopores, the silica framework was removed via hydrofluoric acid etching process. The results indicated that the synthesis of boron-acrylate/SBA-15 polymer composite was performed successfully. Thermal stabilities of the composites were higher with greater amounts of BAc polymer in mesopores under oxidative conditions.