Francis. It incorporates referee's comments but changes resulting from the publishing process, such as copyediting, structural formatting, may not be reflected in this document.
Sol-gel transformations in HPMC (hydroxypropyl methylcellulose) are being increasingly studied because of their role in bio-related applications. The thermo-reversible behavior of HPMC is particularly affected by its properties and concentration in solvent media, nature of additives, and the thermal environment it is exposed to. This article contains investigations on the effects of salt additives in Hofmeister series on the HPMC gelation. Various findings regarding gelation with salt ions as well as with the ionic and non-ionic surfactants are presented. The gel formation in physiological salt fluids such as simulated gastric and intestine fluids is also examined with the interest in oral drug delivery systems. The processes of swelling, dissolution and dispersion of HPMC tablets in simulated bio-fluids are explored and the release of a drug from the tablet affected by such processes is studied. Explanations are provided based on the chemical structure and the molecular binding/association of HPMC in a media. The test results at the body or near-body temperature conditions helped in understanding the progress of the gelation process within the human body environment. The detailed interpretation of various molecule level interactions unfolded the sol-gel mechanisms and the influence of a few other factors. The obtained test data and the established mathematical models are expected to serve as a guide in customizing applications of HPMC hydrogels.
The inter-ply characteristics of polymeric prepreg composites influence their interlaminar fracture toughness and the overall performance. This article embarks on engineering the inter-ply interfaces of carbon fiber reinforced polymer (CFRP) composites. A novel and practical technique for dispersion of multi-walled carbon nanotubes (MWCNTs) onto woven CFRP prepreg is presented. The interlaminar fracture toughness of these CFRP lay-ups was evaluated experimentally and compared with the regular (without any CNTs) specimen. Double cantilever beam and end notch flexure tests were conducted for interlaminar fracture studies. It was observed that the addition of MWCNTs in between the CFRP prepreg plies helps in strengthening the interface. There existed an optimum percentage in which these nanofillers should be added. The presence of nanotubes increased fiber bridging within the ply interfaces, which in turn controlled the inter-ply crack propagation. The findings and the mechanisms are discussed using the test data, SEM pictures, schematics, and scans of the fractured surfaces.
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