D. M. Wiles

The Photo-Oxidation of Polypropylene Monofilaments3: Part I: Chemical Changes and Mechanical Deterioration

The photo-oxidation of commercial, isotactic polypropylene monofilament, initiated by xenon-arc irradiation in air, leads to the initial accumulation in the fiber surface of both carbonyl species and hydroperoxide groups. These chemical changes are accompanied by a severe drop in the elongation at break. Extended irradiation leads to a substantial accumulation of these oxidation products throughout the fiber and to a loss of tensile strength. Oxidation products were identified and estimated from transmission and internal reflection in spectroscopy [∼C(O)∼ and —OH] and by chemical analysis (—OOH). Marked increases in fiber wettability were also found to accompany photo-oxidation.Distinct differences in product ratios from photo-oxidized polypropylene film and fiber samples were observed. These differences are consistent with the morphological control of the efficiency of initiation after hydroperoxide photocleavage, but are more likely to result from some radical scavenging by the unextractable phenolic ad...

Effect, of Light on the Flammability of Nomex Fabric

Nomex fabrics have been irradiated in a xenon-arc Weather-Ometer, and the resulting changes in combustion char acteristics, tensile properties, and degree of discoloration were measured. The ignition and hurning proprties of ir radiated and unirradiated specimens were determined with the TRI Flammahility Analyzer employing burning con figurations of 45° and the horizontal (12 oclock). Indications are that the limiting oxygen index is reduced and the burning rate increased as irradiation time is increased. Flammability results obtained with DOC FF 3-71 were not conclusive. Nevertheless, the reduction in flame resistance of Nomex as a result of irradiation appears to be less of a potential problem than the concomitant decrease in tenacity.

Bicomponent Composites: Preparation from Incompatible Polymers by Corona Treatment

Corona treatment of various substrates in nitrogen was found to markedly improve the adhesion between the substrate and polymeric coatings which were subsequently applied by in situ polymerization of the appropriate monomers. Sub strates included films, fibers, and fabrics of polymers such as polypropylene, polyethylene, polyelhylene terephthalate, polytetrafluoroethylene, and Saran. Condensation polymers employed as coatings included polyamides, polyesters, poly- sulfonamides, and poiyureas. Other polymer coatings were also applied by anionic and cationic polymerization. Com posites prepared after corona treatment of the substrate were shown to have superior interfacial adhesion and abrasion and solvent resistance, compared with composites which had been prepared without corona treatment. Electron micro copy was used to demonstiate the difference between differently treated samples of films and fabrics. The good interfacial adhesion exhibited by coatings on corona-treated films, even after extensive elongation of the composites, indicated the possibility of preparing bicomponent fibers from coated substrates which fibrillate on drawing.

The Effect of Solvents on Some Properties of Cotton Cellulose 1

Samples of cotton duck were immersed in pyridine, aqueous methylamine solutions, and a variety of other solvents. Pyridine and methylamine caused swelling of the cellulose fibers and an increase in the moisture content of the fabric. Pyridine also increased the fabric breaking strength. This is explained in terms of enhanced plastici zation by pyridine and water molecules which are hydrogen-bonded to cellulose. Treatment by pyridine or aqueous methylamine reduced the rate of photochemical degradation of fabric samples exposed in a Weather-Ometer. An explanation for this is based on the changes these solvents cause in the fiber structure, e.g., less dense packing of cellulose chains in the swollen fibers. It is suggested that swollen fibers absorb less of the incident light from a carbon-arc and dissipate more of the absorbed energy without chain scission.

Infrared Spectra of Monofilaments

Nondestructive methods which may be employed to obtain infrared spectra of textile monofilaments are compared, and modifications are suggested which improve spectral quality and experimental ease. A new method of recording the infrared spectrum of a short length (<2 cm) of a single monofilament is described, and the uses and limitations of this simple technique are discussed.

An Experimental Procedure for Determining the Flammability of Carpets Using the TRI Flammability Analyzer

A test procedure employing the TRI Flammability Analyzer has been developed for measuring the combustion pro pensity of carpets. The method evaluates the Limiting Oxygen Index (LOI), rate of flame propagation, and smoke development characteristics of carpet samples undergoing horizontal-type burning. A variety of mounting arrange ments and ignition sources were initially investigated and a test procedure employing three methenamine-timed burning tablets as the ignition source was established. Test results are reported for 20 carpets combining different pile fibers, construction and backing materials. General conclusions regarding the effects of these parameters are discussed. Possible test criteria based on the values for the LOI, used in conjunction with the burning rates and smoke produced, are suggested for assessing the suitability of a particular carpet for specific uses.

Effect of Noncellulosic Material on the Actinic Degradation of Cotton Fabric Part IV: 5-Bromosalicylaldehyde, N-(n-Butyl)-5-Bromosalicylaldimine, Di-(5-Bromosalicylaldehyde) Ethylenediimine, and Their Copper Complexes

Cotton duck samples were treated with derivatives of salicylaldehyde or with copper complexes of these derivatives, and were exposed in a carbon-arc Weather-Ometer. The effectiveness of the treatments in reducing the rate of photo-induced depolymeriza tion of cotton cellulose has been related to (a) the volatility of the treating compounds and complexes, (b) the ability of the compounds to form intramolecular, six-member chelate rings; and (c) the absorption of the treating materials in the spectral region of most intense emmission from the carbon-arc light source. Comparison with oxine and copper oxinate has been made.