Saturday, June 21, 2008

lyocell tencel

Lyocell is a man-made cellulosic fiber. It is produced by solvent spinning, i.e., regenerating into fiber form out of a cellulose solution in an organic solvent. It is made up of cellulose and derived from plant sources like wood pulp. For the solution spinning of lyocell fiber the wood pulp is first dissolved at 90 to 1200 C in a solvent NMMO (N-methyl morpholine N- oxide) under normal pressure to form viscose solution. The solution thus obtained is then filtered and extruded by means of fine jet into a water bath; here the regeneration of cellulose takes place resulting in the formation of fiber. The cellulose is regenerated after passing through an air gap into spinning bath. Finally, the fiber is drawn off with appropriate stretching followed by washing, drying and winding of the fiber. With the higher spinning speeds it is possible to produce fine deniers.

Properties of lyocell/tencel

It is the strongest of all the cellulosic fibers. It has a reduction of 15% of wet strength and hence gives an edge over the others. Tenacity lies in the range of 38-42 cN/Tex.
The ratio of crystalline to amorphous area is approximately around 9:1.
they are soft and lustrous. They show good drape and fluidity.
they are highly stable at high temperature. It does not melt but starts loosing strength rapidly at 3000 C and finally gets ignited at 4200 C
Tencel is inert to most of the organic solvents.
However, it degrades in the presence of hot dilute or cold concentrated mineral acid.
Alkalies causes swelling at first (max. at 9% NaOH solution, 250C) and then ultimately disintegration

Monday, June 16, 2008

Cotton - basic information

The cotton is a cellulose fibre. The molecules of cellulose is the main substance (97%), and pectin, protein, fats are the other substances present with very less proportion in the cotton fibre. Cotton is chemically resistance. It also withstands the action of water and light for a longer time. Cotton may easily ignite so fire safety rules must be strictly observed.

The properties and structure of cotton fibres are greatly dependent on the degree of maturity of separated fibres. Cotton fibre has the shape of a tube cross-section. The unripe fibre has the shape of thin walled pipe. Unripe fibres are weak and exhibits poor dyeability. The presence of such fibres impairs cotton quality. When the degree of maturity is higher, the pipe has thicker walls, and so fibres become stronger and more flexible. They also become crimpier.

Tuesday, June 10, 2008

Spider silk

Du pont is working on synthetic or spider silk and in 1998 published a report about silk they had spun. they found that the molecular orientation of the synthetic silk is very much similar to that of natural silk, whereas in synthetic silk the crystal regions were larger and apart as compared with natural silk. the fibers contained only one or two main proteins that make up drag line silk. and due to these factors the synthetic fibers had lower strength. the studies of du pont does show that synthetic spider silk is a worthwhile endeavor.

Tuesday, June 3, 2008

Basic dyeing of cellulosics

The dye bath is set with the following recipe and then the dyeing is performed according to the process given below:

The fabric is loaded in the rota dyeing machine and then the fabric is run for 10min at a temperature of 40C, with the dye solution in the m/c. After 10 minutes pre-dissolved salt solution is added in two lots and dye bath was heated simultaneously at 2° C/min. Finally temperature of the dye bath was set at 85– 90° C and dyeing was continued at this temperature for 60min. After the completion of dyeing the exhausted dye bath was drained and dyed material was rinsed with cold water followed by soaping and washing.

Washing off Treatments After dyeing, different washing off treatments can be carried out, time - temperature profile of those after treatments are given below. All the treatments have done in a MLR of 1:20.

CR=Cold Rinse: The dyed sample after neutralization treated with cold water for 5min at a MLR of 1:30.

HR=Hot Rinse: The dyed sample treated with hot water at 70oC for 5min at a MLR of 1:30.
SB=Soap at Boil: The sample is treated with 1gpl Auxipon NP, at boil for 10min at a MLR of 1:30