INTRODUCTION FIBER PROPERTIES

KynolTM novoloid fibers are cured phenol-aldehyde fibers made by acid-catalyzed cross-linking of melt-spun novolac resin to form a fully cross-linked, three-dimensional, amorphous "network" polymer structure similar to that of thermo-setting phenolic resins. Chemically, the fibers contain approximately 76% carbon, 18% oxygen, and 6% hydrogen.

Because of their basic chemical structure, KynolTM novoloid fibers are infusible (non-melting) and insoluble, and possess physical and chemical properties that clearly distinguish them from all other man-made and natural fibers. The uniqueness of this fiber structure is implicit in the generic term "novoloid," officially recognized by the United States Federal Trade Commission as designating a manufactured fiber containing at least 85% of a crosslinked novolac.

KynolTM fibers are the only commercially available novoloid fibers, and are used in a wide variety of flame- and chemical-resistant textiles and papers, in composites, gaskets, and friction materials, and as precursors for carbon and activated-carbon fibers, textiles, and composites.

 The typical properties of KynolTM novoloid fibers are listed in the adjoining table. These properties vary slightly with the fiber diameter (denier), and may be further adjusted by varying the conditions of production to produce the balance of properties required for specific applications. The individual fibers are generally elliptical in cross-section, with a ratio of diameters of approximately 5:4. Average diameter ranges from 14m (2 denier fiber) to 33m (10 denier). The virgin fiber is light gold in color, and darkens gradually to deeper shades with age and exposure to heat and light; this change in color does not result from or imply any significant change in the other fiber properties.

KynolTM novoloid fibers have a very soft touch or "hand," and the comparatively high moisture regain is an important comfort factor in apparel. The fibers are generally supplied without crimp, although a partial crimp may be imparted by thermo-mechanical means where necessary to ease spinning.
Properties of KynolTM Fibers
color gold
diameter, m 14~33 (2~10 denier)
fiber length, mm 1~100
specific gravity 1.27
tensile strength 1.3~1.8 (12~16 cN/tex)
elongation, % 30~60
modulus, kg/mm2 350~450 (260-350 cN/tex)
loop strength, g/d 2.2~3.1 (19~27 cN/tex)
knot strength, g/d 1.1~1.5 (10~13 cN/tex)
elastic recovery, % 92~96
moisture regain at 20 C, 65%rH, % 6
FLAME RESISTANCE
One measure of the flame resistance of a given material is its "limiting oxygen index" or LOI, which gives in essence the concentration of oxygen required in the local atmosphere for continuous self-supporting combustion. The LOI of KynolTM materials varies with the particular structure (fiber, felt, fabric) under test and the test method and apparatus, but is generally in the range of 30 to 34- that is, higher than any of the natural organic textile fibers and of all but the most exotic man-made organic fibers.

Thermogravimetric analysis (TGA) indicates that upon heating above 250 C in the absence of oxygen KynolTM fibers undergo gradual weight loss until, at about 700 C, they are completely carbonized, with a carbon yield of about 55~60%. This weight loss occurs without melting, and only a fraction of the comparatively small volume of volatiles produced is combustible. The remaining carbon char is amorphous ("glassy") in structure, and is a good radiator of heat.

All of the forgoing factors are believed to contribute to the high flame resistance of KynolTM materials. When actually exposed to flame KynolTM materials do not melt but gradually char until completely carbonized, without losing their original

fiber structure. The limited production of combustible volatiles results in minimal additional contribution to combustion. The stable surface char radiates heat away from the material, presents a minimum reactive surface to the flame, and retards further production of volatiles. The low shrinkage and absence of melting allow the charred material to retain its integrity as a barrier to keep heat and oxygen away from the interior of the fiber structure , and the low thermal conductivity of the uncharred interior material further limits penetration of heat. Finally, the water vapor and CO2 evolved as products of decomposition and combustion serve to carry heat away from the material and provide an ablative type of cooling effect.

Fiber LOI
Kynol 30-34
Aramid 28-31
Polychlal 28
Modacryl 26
Wool 24
Polyester 22
Acryl 20
Cotton 19
HEAT RESISTANCE
As explained above, KynolTM fibers and materials are highly flame resistant; in addition, they are excellent thermal insulators. However, they are not high temperature materials in the usual sense of the term. While 290 g/m2 woven fabric will withstand an oxyacetylene flame at 2500 C for 12 seconds or more without breakthrough, the practical temperature limits for long-term applications are 150 C in air and 200 to 250 C in the absence of oxygen. At higher temperatures the materials will undergo gradual loss of weight and strength over time, as indicated in the TGA data.
SMOKE EMISSION AND TOXICITY
The chemical structure of KynolTM fibers includes only carbon, oxygen, and hydrogen; therefore when KynolTM products are exposed to flame the products of combustion are principally water vapor, carbon dioxide, and carbon char. Moderate amounts of carbon monoxide may be produced if the supply of oxygen is limited; but the HCN, HCl, bromine- and phosphorus-containing compounds, and other toxic by-products of combustion of many other inherently flame-resistant and FR-treated organic fibers are not produced. The toxicity of the combustion products is thus very low or negligible. Moreover, since the fiber chars without melting and produces few volatiles, smoke emission is also minimal, less than that of virtually any other organic fiber.

The attached figures show comparative smoke emission curves, as well as the results of a series of tests in which the products of combustion of various fiber materials were passed through a chamber containing live mice to obtain a comparative indication of acute toxicity of combustion gases.

An evaluation of KynolTM fibers in accordance with regulations under the U. S. Federal Hazardous Substances Act demonstrated that the fiber is not toxic under the oral and skin contact categories, is not an eye or primary skin irritant, and has a low order of acute inhalation toxicity.
CHEMICAL RESISTANCE

KynolTM fibers display excellent resistance to most chemicals and solvents. They are attacked by concentrated or hot sulfuric and nitric acids and strong bases, but are virtually unaffected by non-oxidizing acids, including hydrofluoric and phosphoric acids; dilute bases; and organic solvents.

chemical resistance data
OTHER PROPERTIES

KynolTM materials are excellent thermal insulators. As shown in the attached table, a nonwoven batting with a density of 0.01 g/cc showed a thermal conductivity of 0.034 kcal/m.h C at ordinary temperatures and 0.025 kcal/m.h C at -40 C.

Retention of properties after exposure to extremely low temperatures is excellent. Efficiency of sound absorption is high. Ultraviolet radiation, although leading to darkening of the fiber, has minimal effect on properties, and resistance to g-radiation is also high.

Retention of Properties After Exposure to Very Low Temperature

Treatment conditions Tenacity (g/d) Elongation (%)
None 1.34 34
-44 CX1000h 1.39 47
-139 CX16h 1.30 39
-196 CX6h 1.36 40

Thermal Conductivity*

Material Specific gravity (g/cm3) Temp. (C) Thermal conductivity (kcal/m.h C)
Kynol felt 0.01 -40 0.024
Kynol felt 0.01 20 0.035
Kynol felt 0.01 40 0.039
glass fibers 0.04 20 0.035
glass wool 0.06 20 0.036
rock wool 0.10 20 0.032

*ASTM C-177 method

Sound Absorption

Material Kynol felt (novoloid 100%) Kynol mat (novoloid 60%/cotton 40%) urethane foam glass wool mat
Thickness 16.4mm 10mm 10mm 10mm
Frequency (Hz)
500 15% 9% 1% 1 %
800 31 13 11 11
1,000 39 17 11 11
1,250 54 23 17 15.5
2,000 73 41 35 32
3,000 85 - 33 32
4,000 89 - 33 32
5,000 89 - 44 46
6,000 89 - 52 -
7,000 - - 60 59

(JIS A-1405 Japan Industry Standard)
TEXTILE & PAPER FORMATION CAUTION: PUNKING
KynolTM fibers may be processed by suitably modified conventional textile techniques. The moderate tensile strength (comparable to that of cellulose acetate) and lack of inherent crimp mean that suitable care must be taken, particularly in carding, to prevent excessive fiber breakage. The fiber must be thoroughly opened, and the density of card clothing and carding speed should be lower than for most conventional fibers. A modified woolen or acrylic system is generally best for spinning; for finer counts, blending with up to 30% of other fibers such as aramids improves processing speed and increases yarn strength. Heavier yarns (300 tex) may be quite easily produced; with suitably modified equipment 100% novoloid yarns as fine as 30 tex (20's cc) and blended yarns as fine as 20 tex (30's cc) are routinely produced, to specifications as listed in the catalog section.

KynolTM spun and filament yarns are used in the production of fabrics in weights from 95 to 550 g/m2, as well as in knitted products such as gloves. For certain applications glass or aramid fibers are added to improve strength and abrasion resistance.

KynolTM materials may be dyed with cationic or disperse dyes; however the range and stability of the colors obtainable are limited by the inherently gold color of the fiber and its tendency to darken with age and exposure to heat and light. Dark shades may be obtained with good light stability, but lighter shades are best avoided. For applications where color is an absolute requisite, even at the sacrifice of some flame-resistant performance, we offer fabrics faced with flame-retardant cotton which can be dyed to vivid shades.

Dry-formed webs and felts of KynolTM novoloid fiber are readily produced by conventional needle-punching and other felting techniques. For papers made by wet-laid methods the physical characteristics of the fiber generally require the use of a binder such as PVC, unsaturated polyester, or epoxy, although 100% novoloid papers have been produced by special techniques using uncured or partially cured KynolTM fibers as the binder.

 Like other organic fibers containing methylene structural linkages (-CH2-) KynolTM fibers may, under certain conditions, become subject to a self-sustaining combustive reaction known as "punking." This phenomenon results from the gradual formation of peroxides at the methylene sites, and subsequent exothermic decomposition of these peroxides.

Punking may occur in materials containing methylene bonds subject to peroxide formation provided that a large surface area is available for oxidation and the rate of heat removal is low. These conditions are met by large masses of tightly packed KynolTM fibers, which are excellent heat insulators. Given sufficient oxygen for initial peroxide formation, sufficient bulk for efficient insulation, and a high enough initial temperature for peroxide decomposition to generate more heat than can be removed by ventilation or other means, internal temperatures may rise to 570~580 C, at which point ignition of the fiber may occur. The result is a smoldering, glowing combustion which continues until the fiber mass is consumed.

The keys to this process are tight packing and high initial temperature. Thus punking is easily prevented by appropriate control of conditions of storage and use. KynolTM materials should not be stored in bulk at high temperatures or subjected to lengthy heat treatment over 120 C without adequate ventilation, and should be promptly cooled to below 60 C after heat treatment or high temperature use. Applications involving prolonged exposure to high temperatures with limited opportunity for heat escape, such as steam pipe insulation, should be avoided. Punking does not occur in the absence of oxygen - in an environment other than air or when the fibers are encapsulated in a matrix material.