The grafting copolymerization of natural rubber and o-aminophenol was carried out by using tworoll mill machine. The prepared grafted antioxidant, NRgraft-o-AP, analyzed by using Infrared and 1 H-NMR Spectroscopy techniques. The thermal stability, mechanical properties, and ultrasonic attenuation coefficient were evaluated for NBR vulcanizates containing the commercial antioxidant, PBN, and the prepared grafted antioxidant, NR-graft-o-AP, and the control vulcanizate. Results of the thermal stability indicate that the prepared NR-graft-o-AP can protect NBR vulcanizate against thermal treatment much better than the commercial antioxidant, PBN, and control mix, respectively. The prepared grafted antioxidant improves the mechanical properties of NBR vulcanizate.
The grafting of ADPEA onto natural rubber was executed with UV radiation. Benzoyl peroxide was used to initiate the free-radical grafting copolymerization. Natural rubber-graft-N-(4-aminodiphenylether) acrylamide (NR-g-ADPEA) was characterized with an IR technique. The ultrasonic velocities of both longitudinal and shear waves were measured in thermoplastic discs of NBR vulcanizates as a function of aging time. Ultrasonic velocity measurements were taken at 2 MHz ultrasonic frequency using the pulse echo method. We studied the effect of aging on the mechanical properties and the swelling and extraction phenomena for acrylonitrile-butadiene copolymer (NBR) vulcanizates, which contained the prepared NR-g-ADPEA and a commercial antioxidant, N-isopropyl-N 0 -phenyl-p-phenylenediamine. The prepared antioxidant enhanced both the mechanical properties of the NBR vulcanizates and the permanence of the ingredients in these vulcanizates.
Detecting defects in various industrial products remains a challenging task in the industry. Researchers are constantly working to improve detection techniques and tools for various defects, particularly cracks. Many industrial structures suffer from cracks. The selection of a suitable technique and/or tool is based upon the tested structures and the accuracy of the technique and/or tool. The work's novelty is the development of a fully accurate, simple, and safe ultrasonic tool for precisely scanning cracks. A pen-shaped cone was added to the ultrasonic transducers to improve their performance. Different crosshead speeds and annealing techniques were used to cause cracks on medium density polyethylene (MDPE) and poly-methyl-methacrylate (PMMA) polymer plates with specific dimensions. Cone reduced the front diameter of the transducers from 12 to 2 mm (cone tip diameter). It improved the transducers by giving them new properties such as a small near field, a collimated beam, high sensitivity, and high wave reflection. The modified transducers tracked the cracks at discrete sequential sites, where the ultrasonic velocity was measured to determine the crack speed, critical crack speed, dynamic stress intensity factor, and crack branching phenomenon. Additionally, ultrasonic attenuation was measured in order to accurately determine crack growth behavior, the crack's neck zone, and the crack growth dependency on both plate thickness and annealing. Scanning electron microscope (SEM) images revealed crack propagation in polymer plates. The results of ultrasonic testing and SEM evaluations were consistent. This guaranteed that the modified transducers could scan cracks accurately.
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