Impregnated yams

Impregnated yams are considered as composites with unidirectional reinforcement (twist of the yarns used in composite reinforcement is normally negligible) with the given fibre volume fraction Vj this value is determined by the dimensions of the cross-section of the yam (which can differ from point to point in the unit cell, but most often assumed to be constant) and the amount of fibres inside the yam, given by the fibre count or yam linear density ... 

First, elastic properties of each impregnated yam segment are calculated using homogenisation formulae (e.g. the aforementioned Chamis formulae) for the unidirectional array of fibres, using local fibre volume fraction at the segment, properties of the fibres and elastic properties of the matrix. The result is the stiffuess matrix C], expressed in the local 123 coordinate system. Then each yarn segment is represented by an ellipsoidal inclusion with axis... 

Impregnated Fabric n A fabric in which the interstices between the yams are completely filled, as compared to sized or coated material where the interstices are not completely filled. Not included in the definition is a woven fabric constmcted from impregnated yams, rather than one impregnated after weaving. 

Note 2 Impregnation is usually carried out on a woven fabric or a yam. 

The major utility of PTFE dispersions is that they allow processing of PTFE resin, which cannot be processed as ordinary polymeric melt, because of its extraordinarily high melt viscosity, or as solution, because it is insoluble. Thus, PTFE dispersions can be used to coat fabrics and yams, impregnate fibers, nonwoven fabrics, and other porous structures to produce antistick and low-friction coatings on metals and other substrates and to produce cast films. 

When making very dehcate materials it may be necessary to use a yam which is so fine that it would break down under the stresses imposed on it during manufacture. The strength, however, is sufficient once the fabric is made because of the mutual support of adjacent threads. In such cases it is customary to impart temporary strength to the yam by a process known as sizing. This consists of impregnating the thread with some easily removed substance such as starch or dextrine and, in the case of the more modern man-made fibres, with a synthetic product such as polyvinyl alcohol or polyacrylic acid. The size is usually removed before the article is dyed or bleached. Yarns are frequently referred to as warp or weft yarns. In a... 

Impregnated flax, polyaramides and PTFE yam or yam constmctions (asbestos in the past) Packings, seals, and gaskets... 

Equipment for impregnating asbestos is conceptually similar to those used for glass cloth coating. Asbestos readily picks up PTFE dispersions and the amount of uptake depends on the concentration of PTFE in the dip tank. The dispersion may be diluted moderately with deionized water or substantially using a dilute aqueous solution of a nonionic surfactant such as Triton X-100. The speed of the asbestos yam movement through the dip tank has little effect on the amount of uptake. The length and capacity of the oven determines the maximum throughput of the process. 

Squibs are cotton yams or other fibres impregnated with black powder and which bum with an external flame to ignite pyrotechnics, although the term may apply to small pyrotechnic or explosive devices. Safety squibs are those squibs which do not bum with an external flame. Electric squibs are essentially synonymous with the matchheads (bridgewire-low explosive combinations) used in electric detonators as well as a type of jet thmst igniter. 

Fuse, Instantaneous, Non-Detonating (Quickmatch) Article consisting of cotton yams impregnated with fine black powder (Quickmatch). It bums with an external flame and is used in ignition trains for fireworks, etc. UN App. B, ICAO A2... 

The solution dip and solution spray impregnation techniques work with a matrix resin dissolved in a volatile carrier. The low viscosity of the resin solution allows good penetration of the reinforcing fiber bundles with resin. In solution dipping, the fiber, in yam or fabric form, is passed through the resin solution and picks up an amount of solids dependent upon the speed of through-put and the solids level. With solution spraying, on the other hand, the required amount of resin formulation is metered directly... 

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