Henry A. Rutherford

A VAPOR-PHASE TECHNIQUE FOR RADIATION-INDUCED GRAFTING OF VINYL MONOMERS TO FIBERS

A technique for the radiation grafting of volatile vinyl monomers to fiber substrates is described. The monomer is applied from the vapor phase while the samples are exposed to gamma radiation from Cobalt-60. The fibrous materials that are relatively unstable toward radiation are the ones that add the vinyl compounds the most readily. These are the cellulosics (cotton and rayon), cellulose esters (acetate), polyamides (nylon 66), and polypropylene fibers. The polyesters and the acrylics show little tendency to undergo graft polymerization. The monomers that have been studied are methyl acrylate, ethyl acrylate, acrylonitrile, butadiene, vinyl acetate, methyl methacrylate, vinyl chloride, styrene, ethylene, propylene, and divinyl sulfone. The most successful experiments have been conducted with the first five of these monomers, and acetate and polypropylene fibers take part in the grafting process most readily. The rate of grafting of the monomers to many of the substrates can be materially increased by the addition of a third material to the system. Water, methanol, and acetic acid vapors accelerate the rate of grafting to cotton, rayon, and nylon. The modification of cotton by the radiation addition of acrylonitrile results in a fiber almost completely resistant to microorganisms. This effect can be achieved by the deposition of only 3.5% of the monomer (as polymer), and the fiber retains the appearance and feel of untreated cotton. The product is superior in these respects to that made by the addition of acrylonitrile from the iron-peroxide catalyst system.

Delayed Cure With Ionizing Radiation1

The use of ionizing radiation as the delayed step in a durable-press process has been investigated. Methylol acryl article is reacted monofunctionally with cotton by a pad- dry-cure procedure, using acid catalysis. The fabric is washed free of all unreacted chemicals, made into garments, and cross-linked at room temperature with β rays 2 from a machine irradiator. The machine used in the experiments is capable of finishing up to 8,000 pairs of slacks in an 8-hr shift.

The Effect of Nuclear Radiation on Fibrous Materials Part III: Relative Order of Stability of Cellulosic Fibers

Cotton, rayon, and acetate yarns were exposed for different periods of time to thermal neutrons and to gamma rays. The results have shown that total dose is the deciding factor in the extent of change in physical properties of the materials and that gamma rays (Co60) alone have essentially the same effect as thermal neutrons when the energies from the two are equated. The decreasing order of stability of the materials was acetate, rayon, and cotton. The data suggest that there are linkages in the native cellulose molecule susceptible to radiation that are not present in the regenerated materials.

The Effect of Nuclear Radiation on Fibrous Materials Part I: Dacron Polyester Fiber' 1

Dacron polyester filaments of different draw ratios were prepared and were exposed to high-energy radiation from two sources. Exposure both in a reactor and to a Cobalt-60 source resulted in an increase in the moduli of elasticity of the filaments. This indicated that cross-linking reactions took place and predominated over chain scission, particularly during the early stages of irradiation. Draw ratio, i.e., the degree of orien tation of the filament, had an influence on the behavior. The materials of lower draw ratio tended to show more cross-linking than those of high draw ratio, the optimum being between 2.5:1 and 3.0:1. The degree of cross-linking in Dacron under the conditions of these experiments was, however, of a low order of magnitude. The solubility of the filaments was decreased only slightly, and the melting point remained unchanged. The degree of crystallinity of the filament did not influence the behavior of the filaments. Although the work has not yet been extended to many other polymers, it is believed that materials which show a marked tendency to cross-link during exposure to high- energy radiation would show an effect similar to Dacron. For example, polyethylenes of different degrees of orientation or of different pretreatments might well behave quite differently with respect to changes in properties brought about by a given level of radi ation. This has been partially substantiated by some preliminary results obtained with polyethylenes of unknown history, but at the same time known to be different in character prior to irradiation.

The Effect of the Glass-Transition Temperature of Conventional and Radiation-Deposited Polymeric Additives on Mechanical Properties of Cotton Fabric

The change in properties of cotton fabric produced by polymeric additives with varying degrees of stiffness or softness has been investigated by measuring these properties at different temperatures. It was concluded that changes in crease-recovery angle produced by these polymers were not due to lubrication but were related to the elastic-recovery properties of the added polymer. Changes in tear strength and abrasion resistance were shown to be a function of interyarn mobility by measuring yarn withdrawal forces of the fabrics. Radiation-induced deposition of polymers produced changes that were qualitatively similar to those made by conventional polymer applications, but the changes were not as pronounced. This was attributed to the lower degree of surface deposition and the lack of cross-linking of the radiation deposited polymers.

The Effect of Nuclear Radiation on Fibrous Materials: Part II: Dyeing Characteristics of Irradiated Cotton and Rayon

The dye adsorption characteristics of a series of cotton and rayon samples exposed for different periods of time to gamma rays and to thermal neutrons have been deter mined. For this work substantive dyes of known behavior toward degraded celluloses were used. The effect produced in the case of neutrons was twofold. At the early stages and again during the later stages of irradiation, the dye adsorption of the samples was increased: at intermediate exposures the adsorption was decreased. Because hy drolyzed cellulose behaves in the former manner and the acidic type of oxidized cellulose in the latter, the data suggest that neutrons have an effect similar to both hydrolysis and oxidation. Gamma rays (CO60). however, gave only the effect of oxidation.

Radiation-Induced Addition of Flame Retardants to the Double Bond in Acrylamidomethyl Cellulose

Cotton and rayon fabrics were condensed with N-methylol acrylamide to give products with various degrees of un saturation. Radiation-induced free-radical addition to the double bonds in these fabrics was accomplished with carbon tetrachloride, bromoform, chloroform, bromotetrachloromethane, polyethylene oxide, chloral and bromal hydrate, and sodium hypophosphite. Stannous and stannic chloride were also reacted by what seems to be a different mechanism. Bromination of these fabrics is also described. Significant flame retardancy was obtained without alteration of hand, because the reactions are limited to the inside of the cellulose fiber.

Concerning the Existence of Fractions of the Sericin in Raw Silk

Raw silk fibres consist of at least two proteins, silk fibroin and silk sericin. The latter forms a coating over the fibroin and constitutes 15 to 30% of the total weight of the raw fibre. In practical silk processing, the sericin is generally allowed to remain on the fibre until the fabric is ready to be dyed. In this way, it acts as a protective coating for the silk in the weaving or knitting operations. Removal of the sericin is usually accomplished with hot soap solutions. The results of numerous studies of this process led earlier investigators to a variety of con cepts concerning the state and properties of the sericin in the raw silk fibre. Some stated that the sericin is a single protein substance, whereas others claimed it to be a mix ture of proteins which they designated as sericins A, B, etc. The latter concept formed the basis for further claims concerning the desirability of retaining certain fractions of the sericin to improve some wltimate proper ties of the silk. As many of these claims were based on insufficient experimental evidence, it seemed desirable to make a more extensive investigation of the question of the possible existence of several fractions of the sericin in raw silk. The results of the present investigation show that the relative yields of the so-called sericins A and B, obtained after treatment of silk in an autoclave, were dependent on the duration of the treatment. Practically all of the sericin removed in the early stages of autoclaving was in the form generally designated as sericin B. On continu ing the treatment, this fraction was rapidly converted into the more soluble form, sericin. A. Analyses of the fractions, obtained after autoclaving the silk for differ ent lengths of time, showed that the alleged serieins A and B are not definite chemical entities, but are substances whose chemical compositions vary with the duration of the autoclave treatment. It is concluded from these stud ies that the sericin in raw silk does not exist as a mix ture of fractions, but that the fractions are artifacts which result from the hydrolytic decomposition of the naturally occurring sericin during its removal from the raw fibres.

Electron-Beam-Initiated Grafting of Flame Retardants to Fabrics Containing Cellulose. I. Reaction Rate Studies

Abstract Triallyl phosphate (I), bis(β-chloroethyl) vinyl phosphonate (II), and a multi-functional condensate of n were grafted to cotton and rayon fabrics and the grafted products screened for potential flame retardancy. Grafting was initiated by a 48 × 6 in. electron beam, in air, from a 550 kV, 20 mA accelerator powered by an insulated core transformer, with a dose rate of approximately 1 Mrad/sec. The monomers were either copolymerized in untreated fabric with N-methylol acrylamide as a coreactant or were copolymerized with pendant double bonds in fabric that had been acrylamidomethylated in a prior step.

Activation Analysis in Textile Processing

The use of neutron activation analysis as an analytical tool in textile processing is discussed. Gamma-ray spectra of activated fibers show the presence of many trace elements, but are not distinctive enough individually to allow identification of the fibers by the spectra. It is demonstrated that elements that lend themselves to neutron activa tion may be used as tracers in fiber process studies. Activation analysis may also be used successfully as a method for the analysis of yarns and fabrics for additives, such as sizes and finishes.