Formaldehyde Cross-linking Research Articles

Tensile and compression properties of hydrophilic composite materials on a simple model of cartilage. II.

AbstractComposite hydrophilic materials (CHM) containing collagen or cellulose as the insoluble fibrous component and potassium salts of proteinpolysaccharide or carboxymethylcellulose as the soluble polyelectrolyte were prepared as simple models of the connective tissue, cartilage. The tensile properties of uncrosslinked and formaldehyde‐crosslinked collagenous CHM were measured and compared to those of bovine nasal cartilage (BNC). The compressive properties of uncrosslinked and formaldehyde‐crosslinked cellulosic CHM were measured and compared to bovine nasal cartilage. Although elongating to approximately the same extent before breaking (20%), the uncrosslinked collagenous CHM had lower tensile strengths than BNC (330 psi). Formaldehyde crosslinking increased the tensile strength of the collagenous CHM to as much as 3 times that of BNC but reduced the elongation at failure to only 7%. The uncrosslinked cellulosic CHM attained a maximum of only ¼ the compressive strength of BNC (940 psi). Formaldehyde crosslinking extended the compressive strength to as high as ⅓ that of BNC. The results indicate that the simple uncrosslinked and crosslinked models can only partially account for the mechanical properties of BNC.

Gel Permeation Properties of Cellulose

Application of gel permeation chromatography, which has been shown to be an effective means of measuring changes produced in the accessibility of decrystallized cotton cellulose by one form of formaldehyde cross-linking [9, 10], has been extended to the study of alterations of the structure of decrystallized cotton produced by intro duction of formaldehyde cross links under various other reaction conditions. These include reaction in aqueous solution (Form W), in the vapor phase (Form V), in acetic acid solution (Form D), each with high and low concentrations of formaldehyde, and in a bake-cure process (Form C). The properties determined by gel permeation chroma tography are the effective internal solvent volume derived from measurements of selective permeability to solutes of decreasing molecular weight and the limit of per meability to solutes of increasing molecular size. Striking differences were revealed in both the nature and magnitude of the alterations of accessibility resulting from differ ent reaction conditions employed for formaldehyde cross-linking. Corresponding changes were observed in gross properties of the cellulose polymer gels, such as the extent of swelling measured by the volumes occupied by the swollen gels per gram of dry solids. Accessibility was increased by reactions in aqueous solution which produced cellulose having larger internal volumes and permeability limits than the unmodified, decrystallized , cellulose. The reaction catalyzed by hydrochloric acid in the acetic acid medium formed products having larger internal volumes, but somewhat lower limits of permeability. Both the internal volume and the permeability limit were decreased by the bake-cure process which produced a polymer having much lower accessibility than the unmodified, decrystallized cellulose.

Formaldehyde and Benzoquinone Cross-links in Keratin—Reply

(1967). Formaldehyde and Benzoquinone Cross-links in Keratin—Reply. The Journal of The Textile Institute: Vol. 58, No. 2, pp. 84-85.

Formaldehyde and Benzoquinone Cross-links in Keratin

(1967). Formaldehyde and Benzoquinone Cross-links in Keratin. The Journal of The Textile Institute: Vol. 58, No. 2, pp. 83-84.

Degrees of heterogeneity of distribution of formaldehyde crosslinks in cotton cellulose

AbstractThe distribution of formaldehyde crosslinks in cotton cellulose has been followed by electron micrographic analyses of fiber cross‐sections and by kinetic analyses of rates of reactions of formaldehyde with cotton. Rapid and slow phases of the crosslinking reactions are indicated to extents which vary with the specific processes of reaction. A wide range in heterogeneity of distribution of crosslinks is found among the compositions investigated, the most heterogeneous distribution appearing in a high concentration of crosslinks in peripheral regions of the fiber. It is evident that additional substantial differences among the formaldehyde‐crosslinked cottons are due to different extents of reaction of agent per accessible hydroxyl group.

Variations in crosslink organization in formaldehyde‐modified cotton celluloses

AbstractRates of decrease in crystallinity, as measured by x‐ray crystallinity index, have been followed throughout periodate oxidations of cotton cellulose and formaldehyde‐treated cotton celluloses. Depending upon the conditions under which the agent was introduced, a low level of formaldehyde crosslinks exerted small or large retardation on the rate of decrease of crystallinity index. The extents of decrystallization per unit of oxidation of cotton and crosslinked cotton celluloses are substantially smaller in the initial phase of oxidation than in the later stage, indicative of preferential oxidative attack in the early stage on chain segments of predominantly noncrystalline regions. Relative to unmodified cotton, crosslinked cotton celluloses are characterized by more extensive decrystallization per unit of oxidation in the early phase of oxidative attack (to approx. 40%). From these data, supplemented by electron micrographs and solubilities in cupriethylenediamine hydroxide, uniformity of distribution of crosslinks is shown to increase in this series of formaldehyde‐modified cotton celluloses (at the same level of agent) in the order: form D cotton (nonaqueous treatment) < form W cotton (aqueous treatment) < form V cotton (vapor treatment). Effectiveness of crosslinking (i. e., composite of number of linkages, ratio of intermolecular to intramolecular bonds, low degree of polymerization in crosslink) is indicated to increase from form W to form D to form V cotton.

Concerted effects of grafting and crosslinking in cotton fabrics

The formaldehyde crosslinking of the methyl, ethyl, or n-butyl acrylate-grafted cotton fabrics was performed in the dry or semi-dry systems. It was found that the reaction rates of crosslinking of the grafted cotton were not much retarded, the dry and wet crease recoveries of the grafted cotton, especially with n-butyl acrylate, were significantly improved with increasing bound formaldehyde, and the hydrophobicity of the butyl acrylate-grafted cotton had a tendency to be dissipated by a slight extent of crosslinking. Although the tensile and tear strength, breaking elongation, and thermosetting property of butyl acrylate-grafted cotton fabrics inevitably decreased with increasing bound formaldehyde, the loss was smaller than that of the ungrafted and formaldehyde-crosslinked cotton. Water imbibition, and moisture regain increased, and water repellency decreased with increasing bound formaldehyde. Crosslinking in the wet system, improved the wet crease recovery, as in the ungrafted cotton. Furthermore, in the butyl acrylate grafting after partial crosslinking with N-methylolacrylamide, the hydrophilic property of crosslinked cotton was almost retained unchanged and the thermosetting property recovered to that of the untreated cotton at about 35% graft-on.

Gamma irradiated crosslinked cellulose

Journal of Polymer Science Part B: Polymer LettersVolume 1, Issue 11 p. 617-620 Article Gamma irradiated crosslinked cellulose G. S. Park, G. S. Park Welsh College of Advanced Technology, Department of Chemistry and Biology, Cathays Park, Cardiff, Wales, U.K.Search for more papers by this author G. S. Park, G. S. Park Welsh College of Advanced Technology, Department of Chemistry and Biology, Cathays Park, Cardiff, Wales, U.K.Search for more papers by this author First published: November 1963 https://doi.org/10.1002/pol.1963.110011110Citations: 4AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume1, Issue11November 1963Pages 617-620 RelatedInformation

Cotton Cross-Linked at Various Degrees of Fiber Swelling

Wet and dry density measurements were made on a wide variety of wash-and-wear cotton fabrics and some interpretations of these values are given. Methylenated cotton was selected for more extensive fundamental study because of the simplicity of the formaldehyde cross link and the fact that formaldehyde can be reacted with cotton under greatly different conditions. Formaldehyde was used to cross link cotton print cloth at various degrees of fiber swelling by reacting in systems ranging from completely aqueous to anhydrous using hydrochloric acid as catalyst. The amount of water in the system at the time of reaction is related to the extent of fiber swotting. The extent of swelling at the time of cross-linking and the extent of cross-linking influence wet density, which may be considered to be a measure of the water swellability of a fiber. Cross-linking tends to fix or stabilize a fiber in a given state of swelling: the stabilization is more effec tive when the cross-linking is done in nearly anhydrous systems. The state of swelling at the time of cross-linking modifies moisture regain, water of imbibition, dyeabitity, and wet and dry wrinkle recovery. There seems to be an optimum water content in the reaction system at the time of cross-linking for maximum dry and wet wrinkle recovery. As the water content in the reaction system is increased beyond the optimum, the amount of dry wrinkle recovery becomes much less than wet wrinkle recovery. This phenomenon leads to vastly different wash-and-wear ratings of fabric. A mechanism is presented diagrammatically to explain wet and dry wrinkle recovery. The mechanism is based upon hydrogen-bond cross links, covalent-bond cross links, and the position of the two types of cross links.

The Reaction of Formaldehyde with Cellulosic Fibers

The effects of an acid-catalyzed formaldehyde treatment on such mechanical proper ties as breaking strength and crease recovery have been determined for three cellulosic fabrics: cotton, Fortisan, and viscose rayon. Samples of these materials, treated under a selected set of conditions, were compared with three "controls": untreated fabric, fabric treated with distilled water under the conditions of the formaldehyde treatment, and fabric treated with the acid solution used in the formaldehyde treatment under the same conditions. The two-dimensional load-elongation behavior of the fabrics was investi gated, and comparisons were made with the results of corresponding one-dimensional tests. The mechanical properties of single fibers and yarns taken from the variously treated fabrics were also measured. In general, cotton fabrics showed a deterioration in mechanical properties due to formaldehyde cross-linking with respect to the acid-treated control, while correspond ingly, Fortisan and viscose rayon were improved by such treatment. In the case of cotton fibers and fabrics, it was found that the formaldehyde treatment had reduced the fiber and fabric elastic moduli with respect to the acid-treated control, although the formaldehyde treatment had also reduced correspondingly the fiber and fabric breaking strains. The deterioration in mechanical properties caused by hydrochloric acid was most marked in the case of Fortisan. It was found that generally the properties of single fibers, yarns, and fabrics are closely related. The improvement in crease recovery caused by the formaldehyde treatment was great est for cotton, less for Fortisan, and least for viscose rayon. These different responses to the cross-linking reaction appear to be related to the different states of internal order of the three cellulosic fibers. Crease-recovery tests carried out on all the variously treated fabrics showed that marked improvements in crease recovery were usually ob tained only with those treated at an initial pad-bath pH of 2.0, which indicates that a high degree of cross-linking of the hydroxyl groups in the amorphous regions of the fibers is necessary to achieve high degrees of crease recovery.