Fabrication curing

The ease of hydrolysis of a DMEU-treated fabric has been used to produce bicolored cotton fabrics. This was accompHshed by applying a thickened DMEU solution in a print configuration to the pile of fabric, curing the resin, and dyeing the fabric. The DMEU-treated areas resisted dyeing because of the cross-links. Subsequendy, the DMEU-crosslinks were removed via an acid hydrolysis and the entire fabric was overdyed to achieve the desired bicolored effect (69). 

Other most successful durable treatment is based on tetrakis (hydroxymethyl) phosphonium derivatives. Very well-known brand marketed as Proban CC (Rhodia, previously Albright Wilson) involves padding of tetrakis (hydroxymethyl) phosphonium chloride (THPC) urea solution onto the cotton fabric, curing with ammonia in a specially designed reactor to generate a highly cross-linked three-dimensional polymer network. The fabric is then treated with hydrogen peroxide, which converts P3+ to the P5+ state. The reactions are shown in Scheme 24.2. Other similar commercial product is Thor s Aflammit P. In literature many combinations of tetrakis (hydroxymethyl) phosphonium derivatives with other salts have been reported,50 but the most successful so far has been the THPC-urea-NH3 system discussed earlier. 

In the area of liquid state rheology there is also considerable research in progress on the development of mathematical models that predict material behavior during composite fabrication cure processes. For example, the viscosity of a thermosetting matrix can be predicted for any cure cycle by using a mathematical model developed from kinetic and rheological data (26). 

Calorimetric standard used in preserving food, dyeing fabric, curing tobacco... 

Hsieh, S.H., Huang, Z.K., Huang, Z.Z. and Tseng, Z.S. (2004) Antimicrobial and physictil properties of woollen fabrics cured with citric acid and chitostm. Journal of Applied Polymer Science, 94,1999-2007. 

The FDA will allow manufacturers to change sources of silicone elastomers (and others) if they can show that the replacement material is not substantially different from materials described in existing approved applications. The device manufacturer is still required to certify that the processes of fabrication, cure and sterilization it uses in the manufacture of its device are appropriate for the new material and that the device will perform as intended. Premarket notification submission under section 510(k) of the Federal Food, Drug, and Cosmetic Act (21 USC 360(k) and 21 CFR 807.81(a)(3)(i), or a supplemental premarket approval application under 21 USC 360(k) section 515 and 21 CFR 814.39 is necessary when change could significantly affect the safety or effectiveness of the device. These submissions are required to be submitted and approved before the device may be marketed with the change. 

P(l) The selection of polymer resins for use in structural composites will be determined by a number of factors and should not be made without full consultation with materials suppliers and fabricators. Properties required are usually dominated by strength, stiffness, toughness and durability. Account should be taken of the application, service temperature and environment, method of fabrication, cure conditions and level of properties required. A knowledge of service temperature is required to select an appropriate stable resin system as with all polymers loss of stiffness and significant creep will occur if the service temperature is close to the resin second order glass transition temperature. The latter is related to the heat distortion temperature (HDT). 

These adhesives are available as pastes, solvent solutions, and B-staged film supported on glass fabric. Cure generally requires 350°F for 1 hr under moderate pressure. Epoxy-phenolic adhesives were developed primarily for bonding metal joints in high-temperature applications. 

All mixtures that contained different fiber volume fractions percentages and silica fume, rice husk ash and glass as partial replacement of cement were fabricated and tested in order to assess fresh and hardened properties of FRSFEC. Materials, specimen fabrication, curing... 

The polymers of the 2-cyanoacryhc esters, more commonly known as the alkyl 2-cyaiioacrylates, are hard glassy resins that exhibit excellent adhesion to a wide variety of materials. The polymers are spontaneously formed when their Hquid precursors or monomers are placed between two closely fitting surfaces. The spontaneous polymerisation of these very reactive Hquids and the excellent adhesion properties of the cured resins combine to make these compounds a unique class of single-component, ambient-temperature-curing adhesives of great versatiUty. The materials that can be bonded mn the gamut from metals, plastics, most elastomers, fabrics, and woods to many ceramics. 

These are water-soluble crystalline compounds sold as concentrated aqueous solutions. The methylol groups are highly reactive (118—122) and capable of being cured on the fabric by reaction with ammonia or amino compounds to form durable cross-linked finishes, probably having phosphine oxide stmctures after post-oxidizing. This finishing process, as developed by Albright Wilson, is known as the Proban process. 

CeUulose phosphate esters are also produced by treatment with sodium hexametaphosphate [14550-21-1] by the pad-dry-cure technique. These treated fabrics have high retention of breakiag and tearing strength (61). The reaction products contain more than 1.6% phosphoms and are iasoluble ia cupriethylenediamine [15243-01 -3] iadicating that some ceUulose cross-linking occurs. However, siace durable-press (DP) levels and wrinkle recovery values are low, it seems reasonable that only limited cross-linking takes place. 

Phosphonomethylated Ethers. A phosphoms-containing ether of ceUulose can be prepared by the reaction of cotton ceUulose with chioromethylphosphonic acid [2565-58-4] ia the presence of sodium hydroxide [1310-73-2] by the pad-dry-cure technique (62). Phosphoms contents of between 0.2 and 4.0% are obtained. This finish is durable but has high ion-exchange properties and is flame resistant only as the ammonium salt. DurabUity on medium weight fabrics is obtained with chi oromethylph osph onic diamide. This finish has never penetrated the flame retardant market (63). 

Dialkylphosphonopropionamides. CeUulosic derivatives that closely resemble those based on the dialkylphosphonopropionamides have been prepared (71). The fabric was treated with AJ-hydrox raethylhaloacetamides (chloro, bromo, or iodo) in DME solution by a pad-dry-cure technique with a 2inc nitrate [10196-18-6] catalyst. It was then allowed to react in solution with trimethyl phosphite [121 -45-9] at about 140—150°C the reaction rates decreased in the order iodo > bromo > chloro. With phosphoms contents above 1.5%, good flame resistance, durable to laundering, was obtained without noticeable loss in fabric strength. 

In this case, the components are mixed, the pH adjusted to about 6.0 with sodium hydroxide, and the solution appHed to the textile via a pad-dry-cure treatment. The combination of urea and formaldehyde given off from the THPC further strengthens the polymer and causes a limited amount of cross-linking to the fabric. The Na2HP04 not only acts as a catalyst, but also as an additional buffer for the system. Other weak bases also have been found to be effective. The presence of urea in any flame-retardant finish tends to reduce the amount of formaldehyde released during finishing. 

Another modification of this process was reported in 1988 (84). In this process, a precondensate of THPC and urea, plus excess urea, are neutralized to a pH of about 5.7, and the buffer salt is added. The fabric is then given a standard pad-dry-cure process followed by oxidation and laundering. The principal advantage of this modification is a reduction in both formaldehyde vapors and phosphine-like odors released during processing (84). 

Ammonia—Gas-Cured Flame Retardants. The first flame-retardant process based on curing with ammonia gas, ie, THPC—amide—NH, consisted of padding cotton with a solution containing THPC, TMM, and urea. The fabric was dried and then cured with either gaseous ammonia or ammonium hydroxide (96). There was Httle or no reaction with cellulose. A very stable polymer was deposited in situ in the cellulose matrix. Because the fire-retardant finish did not actually react with the cellulose matrix, there was generally Httle loss in fabric strength. However, the finish was very effective and quite durable to laundering. 

THPC—Amide—PoIy(vinyI bromide) Finish. A flame retardant based on THPC—amide plus poly(vinyl bromide) [25951-54-6] (143) has been reported suitable for use on 35/65, and perhaps on 50/50, polyester—cotton blends. It is appUed by the pad-dry-cure process, with curing at 150°C for about 3 min. A typical formulation contains 20% THPC, 3% disodium hydrogen phosphate, 6% urea, 3% trimethylolglycouril [496-46-8] and 12% poly(vinyl bromide) soUds. Approximately 20% add-on is required to impart flame retardancy to a 168 g/m 35/65 polyester—cotton fabric. Treated fabrics passed the FF 3-71 test. However, as far as can be determined, poly(vinyl bromide) is no longer commercially available. 

Phosphonium Salt—Urea Precondensate. A combination approach for producing flame-retardant cotton-synthetic blends has been developed based on the use of a phosphonium salt—urea precondensate (145). The precondensate is appUed to the blend fabric from aqueous solution. The fabric is dried, cured with ammonia gas, and then oxidized. This forms a flame-resistant polymer on and in the cotton fibers of the component. The synthetic component is then treated with either a cycUc phosphonate ester such as Antiblaze 19/ 19T, or hexabromocyclododecane. The result is a blended textile with good flame resistance. Another patent has appeared in which various modifications of the original process have been claimed (146). Although a few finishers have begun to use this process on blended textiles, it is too early to judge its impact on the industry. 

Finishing and Fabrication. Since laminates are normally pressure cured in flat-bed presses and pHes overextend the plates, laminates have rough or uneven edges when removed from the press. These edges are sawed off and the back of the laminate is often sanded to improve the strength of subsequent bonding to various substrates. 

Textiles. Microwave drying of textiles is under investigation, in addition to the possible uses for curing of impregnated and dyed fabrics (182). A microwave clothes dryer for consumer or commercial apphcation is also under discussion (183). Considerable developmental work and media pubhcity have occurred. Problems remain, however, particularly relating to arcing and resonant heating of metal objects that may be present in a load of clothes. These problems may be alleviated by operation at 915 rather than 2450 MHz (184). 

Nonstabilized foams are referred to as froths froth-bonded fabrics are similar in properties to some saturation-bonded nonwovens. Typical foams used as nonwoven binder solutions have a consistency similar to shaving cream. AppHcation methods include knife-edge layering onto a horizontal web surface followed by vacuum penetration, and saturation and penetration of a vertical web surface using a horizontal-nip pad. Drying and curing is carried out in ovens, dmm dryers, or steam cans. 

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