Meet the editorAamir Shahzad has more than seventeen years of experience in university research and teaching both at home and abroad. He received his doctoral and postdoctoral degrees from Xi'an Jiaotong University (XJTU), China, in 2012 and 2015, respectively. His research interests include computational physics, complex fluids/plasmas, plasma oncology, and bio-and energy materials. Currently, Dr.

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The phenomenon of tack has been studied in urethan—urea elastomers prepared from polyether or polyester prepolymers and 4,4′-methylenebis(2-chloroaniline). It is shown that tack at zero elongation is attained only in polymers in which the flexible chains, i.e., polyesters or polyethers, contain 50 chain links or more. This coincides with the requirements for the Gaussian vector function in elastomers. The results suggest that, in the absence of flexible chain ends in these polymers, tack is solely contributed by the flexible segments along the polymer chains, while the rigid blocks in the chains do not participate in the formation of tack.

An homologous series of aliphatic polyureas of the type where the x = 2, 3, 4, 5, 6, 7, 8, 9, and 12, was prepared from hexamethylene diisocyanate and diamines. The polymers were obtained in powder form with the use of acetone as the solvent. The intrinsic viscosities of the phenolic solutions of these polyureas were found to decrease with increasing polymerization temperature. When the melting points of the polymers were plotted against the intrinsic viscosities within each species of polymer, these melting points were found to increase with the intrinsic viscosity. The curves so formed appeared to approach an asymptote.

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