Friday, December 23, 2011

Testing of common salt

Testing of common salt (for dyeing purpose)
Salt in textile dyeing is mainly for exhaustion of dyes from the dye liquor to the substrate. It is also used in the water softening process to regenerate the zeolite .The salt used must be good quality , with low water hardness causing salts, minimum insoluble material and free from metal salt impurities.

Following common tests are done to ensure the good salt quality,

1.Moisture content
2.Dust or insoluble impurities
3. Water hardness caused by water when used in dyeing.
4.% purity of salt.

Moisture content :-
is tested by using a moisture meter or by drying and pre weighed sample in hot air oven .
Dust or insoluble impurities :-
By taking about 100 gms of dried salt sample and dissolve it 250 ml distilled water , allow the insoluble to settle down and then filter it with whatman filter paper no.40. dry and weigh the residue to find out the percentage .

Water hardness :-
Since salt is used in large quantities in reactive dyeing , therefore water hardness caused by salt affect the overall dyeing quality , therefore salt must be tested for water hardness .
Make a solution of 100 gpl salt and test it for water hardness , by using standard EDTA solution.
Purity :-
Take about 6 gms of sample accurately weighed and dissolved in distilled water , made upto 1 ltr. Take 50 ml aliquot and titrate it with 0.1 N silver nitrate solution using 5 % potassium chromate solution as indicator till a reddish orange tinge is obtained.

1 ml of 0.1 N silver nitrate = 0.005845 gm of NaCl

Quality parameter of Salt for Dyeing
pH of aq. Solution                    = neutral
Calcium                                    = maximum 100 mg /kg
Magnesium                               = maximum  50 mg/ kg
Iron                                          = maximum 0.01 mg/kg
Copper                                    = not detectable
Hardness of 80 gpl solution       = maximum 50 ppm
Moisture content                       = maximum 0.25 %
Insoluble dust                           = maximum 0.25%

Thursday, December 22, 2011

Hair Colors

Why coloring hair
Because it is the one thing that can dramatically change our appearance If we don't like the way we look! Also, it is quite fun to change it. I do agree that most of the time we look the best with our natural color. There are few reasons that why we want to dye hair,
(1) We want to lighten  our hair more than three shades,
 (2) We have dark hair and want to dye to make them light or ,
(3) We have natural light  brown or blonde hair and want to dye it,
(4) We are re trying to fix a problem,
(5) We have light hair and want to make it darker.
(6). Many people think that gray is the first sign of aging and the end of his youth, so they go for hair coloring.

Natural hair dyes
Hair dye is one of the oldest known beauty preparations, and was used by ancient cultures in many parts of the world. Records of ancient Egyptians, Greeks, Hebrews, Persians, Chinese, and early Hindu peoples all mention the use of hair colorings. Early hair dyes were made from plants, metallic compounds, or a mixture of the two. Rock alum, quicklime, and wood ash were used for bleaching hair in Roman times, and herbal preparations included mullein, birch bark, saffron, myrrh, and turmeric. Henna was known in many parts of the world; it produces a reddish dye.
Many different plant extracts were used for hair dye in Europe and Asia before the advent of modern dyes. Indigo, known primarily as a fabric dye, could be combined with henna to make light brown to black shades of hair dye. An extract of the flowers of the chamomile plant was long used to lighten hair, and this is still used in many modern hair preparations. The bark, leaves, or nutshells of many trees were used for hair dyes. Wood from the brazilwood tree yielded brown hair dyes, and another hair dye known in antiquity as fustic was derived from a tree similar to the mulberry. Other dyes were produced from walnut leaves or nut husks, and from the galls, a species of oak trees. Some of these plant-derived dyes were mixed with metals such as copper and iron, to produce more lasting or richer shades.
Synthetic hair colors or dyes
In general, hair dyes include
The dye chemicals are usually amino compounds, and show up on hair dye ingredient lists with such names as 4-amino-2-hydroxytoluene and m-Aminophenol. Metal oxides, such as titanium dioxide and iron oxide, are often used as pigments as well.
Modifiers stabilize the dye pigments or otherwise act to modify the shade. The modifiers may bring out color tones, such as green or purple, which complement the dye pigment. One commonly used modifier is resorcinol, though there are many others.
Antioxidants protect the dye from oxidizing with air. Most commonly used is sodium sulfite.

Alkalizers are added to change the pH of the dye formula, because the dyes work best in a highly alkaline composition. Ammonium hydroxide is a common alkalizer.
5.soaps, .ammonia, wetting agents, fragrance, and a variety of other chemicals used in small amounts that impart special qualities to hair (such as softening the texture) or give a desired action to the dye (such as making it more or less permanent).
The developer is most often based on hydrogen peroxide, with the addition of small amounts of other chemicals depending on the manufacturer.

Temporary Hair Dye
Temporary or semi-permanent haircolors may deposit acidic dyes onto the outside of the hair shaft or may consist of small pigment molecules that can slip inside the hair shaft, using a small amount of peroxide or none at all. In some cases, a collection of several colorant molecules enter the hair to form a larger complex inside the hair shaft. Shampooing will eventually dislodge temporary hair color. These products don't contain ammonia, meaning the hair shaft isn't opened up during processing and the hair's natural color is retained once the product washes out.

Semi-Permanent Hair Dye
This product adds color without changing natural color dramatically. The hair color contains tiny color molecules that enter the hair's cuticle, or outer layer, and go into your hair's cortex. They don't interact with your natural pigments. And since the molecules are small, they eventually exit the hair shaft after several shampoos, leaving the hair as it was before treatment.
Permanent Hair Dye
 Permanent Hair Dye  molecules enter all the way into the cortex, where they react and expand to a size that cannot be washed out. These dyes acts to lighten the hair's natural pigment to form a new base and then to add a new permanent color.

Structure of Human hair

Hair is made of strong elastic strands of protein called keratin and in chemical terms is composed of oxygen, iron, nitrogen, hydrogen, sulphur, carbon and phosphorus.   

Each hair is constructed in three different layers: the cuticle, the cortex and the medulla.
The cuticle is the outermost layer of the hair which provides protection to the inner cortex layer.  Improper care and frequent use of harsh chemicals on hair damage the cuticle.

The cortex is the second layer.  . The cortex is composed of fibres twisted together like a rope. It is the cortex which gives the hair its colour. The presence of the four natural pigments black, brown, yellow and red are logged in the cortex in varying proportions, and the air spaces in the cortex determine the colour and shade of hair.  
Lastly, the medulla is the unimportant innermost layer which is composed of soft keratin..  

How hair colors work

The outer layer of the hair shaft,(cuticle) must be opened before permanent color can be deposited into the hair. Once the cuticle is open, the dye reacts with the inner portion of the hair, the cortex, to deposit or remove the color.
Most permanent hair colors use a two-step process (usually occurring simultaneously)
  1. First removes the original color of the hair
  2. Second deposits a new color.
 Ammonia is the alkaline chemical that opens the cuticle and allows the hair color to penetrate the cortex of the hair. It also acts as a catalyst when the permanent hair color comes together with the peroxide.
The developer( peroxide) removes pre-existing color. Peroxide breaks chemical bonds in hair, releasing sulfur, which accounts for the characteristic odor of hair color. As the melanin is decolorized, a new permanent color is bonded to the hair cortex. Various types of alcohols and conditioners may also be present in hair color. The conditioners close the cuticle after coloring to seal in and protect the new color.

Health risk and hair colors

Use of hair dye has been linked to allergic reactions, respiratory disorders and even cancer. Harmful ingredients used in hair color and hair dyes ,Hair dyes contain heavy metals that can be harmful. Ingredients in hair dyes are toxic and cause irritation to the eyes, skin and mucous membranes to hypersensitive people.  

  • Para-phenylenediamine and tetrahydro-6-nitroquinoxaline, both have shown to damage genetic material and cause cancer in animals. Allergic reactions from PPD are known to cause facial and neck swelling. Inhalation is likely to bring about coughing, sneezing and shortness of breath, and respiratory problems in extreme cases. Skin contact with PPD may cause rashes and eye contact irritation, redness and pain.
  • Coal tar, a known carcinogen is used in hair colors and dyes as it creates brighter and more lasting colors than other organic vegetable dyes.
  • Formaldehyde is a preservative linked to cancer, developmental and reproductive toxicity and more.
  • DMDM Hydantoin, another preservative is a known immune system toxin (and has been restricted for use in cosmetics in Japan).
  • Eugenol is a fragrance ingredient that’s associated with cancer, immuno toxicity, neuro toxicity and allergies
  • Ammonia exposure to high levels of ammonia can cause irritation and allergy, hair loss problems and scalp dermatitis.
  • Hydrogen peroxide Hydrogen peroxide bleaches your hair and thus damages it. But the extent of the damage will depend on its level of concentration..
Further readings

Dyes and color index( CI) numbers

The color index is produced jointly by SDC (Society of Dyers and Colourists) in the UK, and the AATCC (American Association of Textile Chemists and Colorists) in the USA. The index is split into two parts: one part gives the commercial names for the individual dyes; the other part of the index gives the color index number, and lists the commercial names for the dyes using that number. 

Color index number

Every dye is given a color index number based on its chemical type. The same number is given to the dyes with the same chemical structure. For example, Resolin Red FB and Dispersol Red B2B, both have the color index number “CI Disperse Red 60." The index number is divided into four sections: 
1) CI stand for color index and is displayed in every color index number 2) The next section is the dye type, e.g., Disperse, Acid, etc. 
3) The third section is the color, according to a defined list of color names, e.g., Red Yellow, Orange 
4) The last number is increased every time a new dye is added to the index; in the example above, “CI Disperse Red 60" is the 60th red disperse dye to be added to the index. 

As an extensive international compilation of the structure and properties of dyes and pigments, as well as a system of numbering these materials, the Colour Index is a potentially valuable tool for all users of colorants.

CAS numbers for chemicals and chemical compounds
CAS Registry Numbers are an important tool for substance searching. These are unique identifiers assigned by the Chemical Abstracts Service (CAS) to specific substances identified by them in the chemical literature.
Registry Numbers save you from having to think of all the different synonyms, trade names, or possible systematic names when you are doing a compound search by linking them all into a single search term.
For example, there are over 20 synonyms for formaldehyde, e.g., methanal, formalin, methyl aldehyde. The CAS Registry Number for it, 50-00-0, is specific to all those names for the same compound.
"The foam retracts above the legible symphony."

Thursday, December 1, 2011

Textile Jobs