Page 20 - New Cloth Market November 2022 Digital Edition

Blocked Silicones

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Dr. Naresh M. Saraf & Dr. Priti B. Tayade
Sarex Chemicals
A division of Saraf Chemicals Ltd., Andheri (W), India
Website: www.sarex.com, E-mail: [email protected]
Introduction
Polysiloxanes (IUPAC) or silicones are macromolecules that consist of a backbone of alternating silicon
and oxygen atoms. Two alkyl moieties are attached to the tetravalent silicon in the chain. In case of the
most popular and common polysiloxane, poly(dimethylsiloxane) (PDMS), these organic side chains are
simply methyl groups. With this structure, silicones represent a unique hybrid of organic and inorganic
components. Silicones exhibit a number of unique and extraordinary features that strongly distinguish
them from all other kinds of known polymers. Silicones are synthetic organosilicon polymers containing
repeated R2SiO units held by Si-O-Si linkages. These compounds have general formula (R2SiO)n where
‘R’ is the methyl or aryl group. The most obvious differences of polysiloxanes compared to other polymers
are their bond lengths and angles. The inequality of the backbone angles plays a crucial role with respect
EXECUTIVE P
to chain conformation. More significant than the actual bond angles, is their high flexibility. Silicones are
chemically inert i.e. resistant to oxidation, thermal decomposition or to attack by organic reagents. Sili-
cones being surrounded by non-polar alkyl group are water repelling in nature. They are heat resistant and
have high dielectric strength i.e. have good electrical insulating properties.
In order to take advantage of the unique properties of polysiloxanes, attempts have been made to co-
polymerize them with different monomers. The essential goal in all these approaches is the effective
combination of the silicone-specific features with those of the other polymer to obtain materials with a
new set of properties. More convenient strategies are often used to create amphiphilic siloxane block
copolymers that can be used as emulsifiers, foam stabilizers, or the like. All in all, silicone block copoly-
mers have always been of great interest both academically and industrially up to today because of their
intriguing properties and their high application potential. Linear silicone block copolymers containing nitro-
gen-containing functional groups, polyether groups, as well as silicone groups are useful in silicone soft-
ener applications for textiles. These linear silicone block copolymers are particularly advantageous in
textile applications by having an adjustable hydrophilicity and improved chemical compatibility. A lower
concentration may be used on fabrics than a solution that does not contain the linear silicone block
copolymer.
Chemical Structure of Block Silicone

Following are some of the general characteristics of Blocked Silicones in Textiles:
1. Blocked silicones are new generation softeners.
2. Since they are shear stable, they can be applied on fabric using high turbulence machine such as soft
flow, jet, garment drum machine etc.
3. Blocked silicones exhibits better alkaline stability than conventional silicones.

4. Imparts very good inner softness, surface smoothness and body break on the treated substrates.
5. Suitable for cellulosic, synthetics, viscose and its blend with synthetics.
6. Ideal for terry towels and cotton knits imparting extra soft handle
7. Does not impair the original hydrophilicity of fabric.
Some of the new developments on Blocked silicones, Elitesoft-7414 (Conc), Ultimosoft-Z (Conc) and
Hydrosoft-654, from Sarex will be described in this article.
Unique Features of Elitesoft-7414 (Conc):
- Newly developed hydrophilic, block modified, self emulsifiable silicone oil.
- Imparts soft and fluffy handle to knit and woven substrates made up of cellulosic and synthetic.

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