Products / Development
What is Rayon
Characteristics of Rayon
The following is a description of the properties of rayon to help better understand the fiber.
We hope you find it informative when considering the use of this fiber.
The tenacity of rayon weakens in diluted acids at high temperatures as well as in concentrated acids at cold temperatures, and it would soften. Strong alkalis expands the fiber and also weaken the tenacity.
The pH of rayon is in the 5-6 range which indicates mild acidity.
Fibers in this pH range are considered to be “skin-friendly”.
There are two types of dyes: richly-stained and poorly-stained dyes
A commonly used dye is “direct dye”. The use of this type of dye for rayon results in colors more vivid compared with the results of cotton.
Rayon is known to be “easily dyed” and to be “vividly colored” because of easiness and vivid color in dyeing with direct dye.
●Various Fibers’ Staining Properties Against Dyes
|Direct dyes||Reactive dyes||Acid dyes||Dispersed dyes||Cationic dyes||Vat dyes||Sulpher dyes||Naphthol dyes|
○：Be dyed well , △：Be dyed a little , －：Be not dyed
Rayon is normally dyed with direct dyes and reactive dyes resulting in more richly colored fibers compared to cotton.
Among different types of fibers, rayon is not the strongest and not the weakest.Rayon drapes well, and it has clinging and tight-fitting textures (although it may not sounds nice).
●Physical Property Of Various Fibers
|Official moisture regain
|Wet-and-dry strength ratio||60～65||60～64||84～92||100||80～100||102～110||70||76～96|
●Properties against water
As for hygroscopic property, official moisture regain is the moisture regain which a fiber has in the condition of 20℃65%RH. Rayon has 11% of official moisture regain, which can’t be found in a synthetic fibers, and it can be regarded as moist fiber which has the same percentage of official moisture regain as silk (11%), next to wool (15%) among natural fibers.
Its water-absorbing property is affected by the product type. Rayon has the ability to absorb water in the fabric while storing approximately 80% of its own weight within the fiber.
Its cross-sectional surface is shaped like a chrysanthemum and can take in large amounts of water to the fiber due to capillary action. However, due to this property, the fiber expands when it gets wet, which causes problems such as wrinkles after washing as well as shrink after drying especially in the case of woven cloth.These shortfalls can be solved by applying a morphological stabilization process or a wrinkle-free process.
Conversely, these properties cannot be seen in other fiber so wrinkles and shrinkage may be properties used to develop new products.
Among other fibers, the electric resistance value is low so a certain amount of anti-static efficacy can be expected. Under dry conditions (especially in winter), its moisture regain decreases so rayon produces static electricity easily.
Electrostatic charge of Rayon ranks between wool and cotton.Rayon may seem to interact negatively with fibers like polyester but it is not true because of its antistatic efficacy.
●Ranks of Electrostatic Charge
Rayon has a slight cool touch (contact coldness) when in contact with the skin. When compared with cotton, rayon has a cooler feel because of a high initial thermal conductivity.
You may think that rayon is flammable.However, rayon which has no fusion point shows flame resistance depending on the use of the fiber (Rayon has high flame resistance when a certain amount of fiber is inserted into a certain space). Although it shouldn’t happen, in case of a real fire, the gas and smoke are important factors that should be evaluated in addition to flammability.
Combustion gas has no toxic gas as it is originated from C, H and O.
Not much smoke is emitted in burning.
When the fiber is incinerated, little ash remains.
●Smoke density and limiting oxygen index by combustion conditions
|Smoke density Cs||Oxygen index LOI(%)||Softening point℃||Melting point℃||Kick-off temperature℃||Carbonization remnant℃||Remarks|
|Cotton||0.05||0.03||18.4||340||2.0||Yellow discoloration in 120℃5Hr
Decomposition in 150℃
|Silk||23.6||235||9.0||Ignition in 366℃|
|Wool||6.90*||1.12||23.8||240||12.8||Carbonization in 300℃|
The deodorant effect of rayon is not well known.
●Deodorant effect of sliding-screen paper
The deodorant effect of two types of sliding-screen paper was examined: Sliding-screen paper combined with rayon and the one combined with PET.The results showed that the sliding-screen paper combined with rayon absorbed the odor of ammonia better than the one with PET mixed.
The results also showed that the sliding-screen paper with rayon mixed has slightly higher deodorant effect against formaldehyde odor.
(1) Device under test
The following 2 kids of sliding-screen paper were used for the text.
Both are commercial items.
|Component||Compounding ratio||weights of unit area|
|PSliding-screen paper with PET mixed||PET/Pulp/ vinylon||85/10/5%||62.5g/m2|
|Sliding-screen paper with rayon mixed||PET/Pulp/ Vinylon||55/40/5%||61.1g/m2|
（２）Deodorant effect evaluation test
A. Gas tested ※Figure in ( ) shows the Initial concentration
1. Ammonia (40ppm)
2. Formaldehyde (5ppm)
B. Measured by Japan Synthetic Textile Inspection Institute Foundation
As cellulose reproduced from natural lumber, it will return to the soil if it is left in the soil.In addition, rayon is a very eco-friendly fiber as the dissolution process will take place with the aid of microorganisms.
●Biodegradability evaluation test by burying non-woven cloth of rayon 100% in soil
As this test involves microorganisms, the results might be slightly different depending on soil to be used and seasons.
The use of a disposal unit for household food scraps (composter) is also possible for dissolution.
Production location and weather conditions affects the whiteness, fineness and fiber length of cotton which is also reproduced from a cellulose. In contrast, rayon, a reproduction of cellulose, can provide a fabric consistent in thickness, length, whiteness and so on.