Selective chemical etching of poly(ethylene terephthalate) using primary amines

Several primary amines have been examined as selective degradative etchants for the investigation of poly(ethylene terephthalate) (PET) morphology. The objective is to remove less ordered regions, leaving crystals intact. The amines include 40% and 20% aqueous methylamine, 70%–40% aqueous ethylamine and pure and 40% aqueous n-propylamine. Weight-loss and x-ray diffraction data show that certain concentration of aqueous amine solution simultaneously degrade and crystallize PET. This observation indicates the hazard of using some of these amine reagents to characterize PET morphology since the crystalline structure found after etching is likely to be a result of solvent-induced crystallization during degradation. Data for 40% aqueous methylamine used at room temperature shows that crystallization does not occur during etching, and in light of earlier research indicates the favorable nature of this reagent as a selective degradative medium for PET. Application of this reagent disclosed that in oriented PET fibers chemical stress cracking occurs, causing the degradative reagent to lose its selectivity.     

Anodic oxidation of manganous ion in liquid ammonia

In acidic solutions of liquid ammonia, manganous ions can be oxidised anodically at a vitreous carbon electrode, probably yielding Mn³⁺ species. By means of non-steady state measurements of the re-reduction of the oxidation product, the apparent rate constant and standard potential have been determined. The Mn³⁺ species is unstable in the medium and decomposes by oxidation of the solvent.     

Measurement of franck-condon factors for the υ′= 0 progression in the BX system of PO

Laser fluorescence of PO produced in a microwave discharge through organophosphonate esters has been studied. The flourescence was pumped in the B²Σ⁺-X²Π 3250 Å system. Relative intensities of fluorescence for the υ′= 0 progression were measured. These intensities were used to derive Franck-Condon factors for the υ′= 0 progression.     

Assessment of structural analysis technology for static collapse of elastic cylindrical shells

The prediction of the ultimate load-carrying capability for compressively loaded shell structures is a challenging nonlinear analysis problem. Selected areas of finite element technology research and nonlinear solution technology are assessed. Herein, a finite element analysis procedure is applied to four cylindrical shell collapse problems which have been used by computational structural mechanics researchers in the past. This assessment will focus on a number of different shell element formulations and on different approaches used to account for geometric nonlinearities. The results presented confirm that these aspects of nonlinear shell analysis can have a significant effect on the predicted nonlinear structural response. All analyses were performed using a single software system which allowed a convenient assessment of different element formulations with a consistent approach to solving the discretized nonlinear equations.