George L. Drake

Some Chemical and Physical Factors Influencing Flame Retardancy

Information is given to explain why or how bromine or nitrogen contributes to phosphorus-containing flame retardants. Amide and amine nitrogen generally increase flame resitance, whereas, nitrile nitrogen can detract. Essentially, all of the phosphorus in a flame retardant is accounted for in the char or solid phase and this is also true when amide or amine nitrogen is present. Nitrile nitrogen can cause a significant reduction in percent phosphorus accounted for in the char. The amount of nitrogen accounted for in the char is dependent upon the type of nitrogen and the atomic ratio of N to P in the flame retardant. When large proportions of amide or amine nitrogen are present they also contribute to flame resistance in the gas or vapor phase. Bromine makes its contribution to flame retardants by acting mainly in the vapor phase, and its action appears independent of phosphorus.

Flame Retardants for Cotton Using APO and APS-THPC Resins

A new group of polymers made by reacting tris(1-aziridinyl)phosphine oxide, referred to as APO, or tris(1-aziridinyl)phosphine sulfide, referred to as APS, with tetrakis- (hydroxymethyl)phosphonium chloride, referred to as THPC, are good permanent-type flame retardants for cotton. All three of the compounds are water-soluble crystalline materials. The application of APO- or APS-THPC resins to textiles consists of padding fabric in an aqueous solution of the compounds, drying the fabric, curing it at about 140° C. for about 5 min. to polymerize the compounds, and then rinsing the fabric to remove any unpolymerized material. About 8% of the resins in 8-oz. cotton twill or sateen is adequate to make the fabric pass the vertical flame test before or after 15 launderings with synthetic detergents, followed by an acid fluoride sour after each laundering. The flame resistance is also very durable to boiling alkaline soap solutions. The properties of fabric treated with these new polymers are, in general, excellent. The hand and strength of the fabric is only slightly different from that of untreated fabric. The flame-resistant fabrics are resistant to rot and mildew.

Conventional Pad-Dry-Cure Process for Durable- Flame and Wrinkle Resistance With Tetrakis (Hydroxymethyl) Phosphonium Hydroxide (THPOH)

A durable-flame retardant based on tetrakis (hydroxymethyl ) phosphonium hydroxide (THPOH), urea, and trimethylolmelamine has been developed and applied to cotton fabric. The process is accomplished by padding fabric through a water solution of the three components to a wet pickup of about 75%, drying at moderate temperature, and curing at an elevated temperature. Solutions of 25-34% total solids containing the three components in a molar ratio of 2 : 4 : 1 (THPOH: urea : methylolmelamine), when applied to cotton fabrics of 8-9-oz weight, imparted flame resistance, and only minimal losses in breaking and tearing strength. The treated fabrics retained 91-95% break strength and 73-80% tear strength. Wrinkle recovery angles (W + F) of treated fabrics ranged from 280° to 306°. Wash- wear and durable-press properties are discussed. Little or no yellowing of treated fab rics was observed when bleached with sodium hypochlorite solution and scorched between heated plates. Resin add-ons of fabrics treated in this manner ranged from 15 to 19%. Flame resistance of fabrics treated by this process is retained after boiling the treated fabrics in a soap-sodium carbonate solution for 3 hr or after 15 laundering cycles.

Imparting Crease Resistance and Crease Retention to Cotton With APO

Cotton fabric (80 × 80) was made crease resistant by processing with APO, tris(1-aziridinyl)phosphine oxide. Application was made by wetting the fabric with an aqueous solution of APO containing catalytic quantities of zinc fluoborate, squeezing out the excess with squeeze rolls, drying for 4 min. at 80-90° C., and curing for 4 min. at 140° C., followed by a good wash. An aftertreatment with a 1% Primenit VS2 solu tion increased the crease recovery angle. Monsanto crease angles of from 250° to more than 300° (warp + fill) have been obtained, depending on the resin add-on. The crease recovery is not changed much by home laundering. A loss of 30% in the Elmen dorf tearing strength was observed with samples with over 300° crease recovery angles. Creases durable to washing were obtained by drying the fabric with a hand iron followed by an oven cure. The resin could not be stripped from the fabric by methods that are effective with other resins. In addition to imparting crease resistance, this resin also imparts some degree of flame resistance.

Effects of Temperature on Oxygen Index Values

The oxygen-index (01) test [1 ] is finding widespread application for determinations of fabric flammabilities [2, 3, 4, 5, 6]. Effects of environmental temperatures on 01 values have not been reported. This is perhaps because of the original assumptions of Fenimore and Martin [2] or because the logical expectation is that conditions are unfavorable for convective heating of the sample during testing. While determining 01 values for textile specimens, we observed that the glass chimney of the apparatus gets quite hot to the touch. We also observed that, when successive tests were made

Insolubility in Cuprammonium Hydroxide as a Means of Detecting Crosslinking in Chemically Modified Cotton

Native cellulose dissolves in cuprammonium hydroxide solution, but, when it is crosslinked, it becomes a space polymer and is insoluble in this reagent. A method of detecting alkali-stable crosslinks in cotton is presented—the sample to be tested is shaken with cuprammonium hy droxide solution for 17 hr. If it dissolves completely, cellulose chains are not crosslinked, but, if it is partially insoluble, crosslinking is indicated. Partially insoluble cellulosic material appears in the cuprammonium hydroxide as granules that are easily detected visually. Cellulose was reacted with compounds which contained one or more groups that are reactive toward cellulose. In all cases the cellulosic derivatives made from cellulose and compounds that could crosslink it were partially insoluble in cuprammonium hydroxide. The compounds that were not capable of crosslinking cellulose produced derivatives soluble in cuprammonium hydroxide. Cotton was made insoluble in cuprammonium hydroxide by reacting it with formaldehyde, glyoxal, chloroethylsulfuric acid, α,γ-glycerol dichlorohydrin, a mixture of α,β- and α,γ-glycerol dichlorohydrin, tetrakis (hydroxymethyl) phosphonium chloride, compounds containing two or more N-methylol groups, 1,4-disulfato-2-butyne, and potassium (disulfatoethyl) amine. Aminized cotton, which is soluble in cuprammonium hydroxide, was made insoluble by cross linking it with either formaldehyde or tetrakis (hydroxymethyl) phosphonium chloride.

Durable Flame-Retardant Treatments for Blends of Cotton, Wool, and Polyester:

Durable flame-retardant treatments based on a vinyl phosphonate oligomer or Thps were applied to cotton, cotton/polyester, cotton/wool, and cotton/polyester/wool medium-weight twill fabrics. The treatments were applied by either a pad, dry, cure process or a two-step procedure consisting of a pad, dry, cure application of DMDHEU followed by a Thps-NH3 cure process. Flammability of the treated fabrics was evaluated by a number of tests, including burning rate, vertical char length, oxygen index, and a flame-extinguishment test. Physical properties were determined by standard tests to measure breaking strength, wrinkle recovery, stiffness, durable- press rating and shrinkage due to laundering. Cotton/wool blend fabrics treated with Thps-urea-TM M had the best flame-retardant properties.

Wet Soiling of Cotton Part IV : Surface Energies of Cotton Finishing Chemicals

The goal of this investigation was to determine the relation between the surface energy of cotton finishes, their tendency to become soiled, and the case with which soil is removed from them. The surface energy of finishing materials was characterized by wetting measurements. The critical surface tension for wetting of finishing agents and of the corresponding finished fabrics was determined. The critical surface tension for wetting by organic liquids of these same materials immersed in water was also determined. Cellulose has a high critical surface tension for wetting in air (high surface energy), but it has an extremely low critical surface tension for wetting in water. Due to this low surface energy in water, cellulose has a high resistance to wet soiling by hydro phobic soils. Similarly, hydrophobic soils are relatively easily removed from cotton. Silicone and fluorocarbon finishes have low surface energy in air but form high-energy surfaces in water. This leads to a strong tendency for these finishes to become con taminated in water by hydrophobic soils and, correspondingly, these soils are difficult to remove by laundering.

Wet Soiling of Cotton Part II: Effect of Finishes on the Removal of Soil from Cotton Fabrics

The retention of various soils during laundering as a function of the type of finishing agent applied to cotton fabries was studied. Soil retention is compared with soil deposi tion. Generally, systems that are readily soiled from a water medium also have a strong tendency to retain soil during laundering. Chemically modified cottons having a large degree of swelling in water are a notable exception ; soil is difficult to remove but does not deposit readily. Silicone, Huorocarbon, and hydrocarbon acrylate finishes have a strong retentiveness for soil corresponding to a large tendency to become soiled in aqueous systems.

Phosphonomethylation of Cotton

A new phosphorus-containing ether of cellulose was prepared by the reaction of cotton with chloromethylphosphonic acid in the presence of sodium hydroxide. Phosphorus contents from 0.2% to 4.0% were obtained. By proper control of the phosphono methylation reaction, derivatives were made which ranged from water soluble to fibrous materials in which the physical properties of the untreated cotton were substantially unaltered. Phosphonomethyl cotton was flame resistant in the ammonium salt form and had a cation exchange capacity equivalent to some of the cation exchange resins.