Monday, 15 June 2009
Polypropylene Fibres- Manufacturing Process
Propylene is one of the constituents obtained from thermal or catalytic cracking of petroleum. Under suitable polymerising conditions, propylene produces fibres forming polypropylene.
Polymerisation: It is done by dissolving propylene in heptane using TiCl3Al(C2H5)3 catalyst system at about 100 deg C under a pressure of 30 Atm for 8 hours. The polymer has a molecular weight of about 80000.
Spinning : Polypropylene is melt spun. The filaments are extruded at 100 deg C above the melting point, cooled in air chamber and collected on bobbins. The filaments are hot drawn (polyethene- cold drawn) and twisted into yarns.
1. PP fibres are colorless and have a smooth surface, with round cross section.
2. Tenacity- 4.5-6 gpd
Elongation at Break: 17-20 %
Elastic Properties at 2% extenstion: Instantenous
Stretch for 30 Seconds: 91%, delayed - 9%
Moisture Regain: Nil
3. Boiling water shrinks PP by about 15-20% in 20 minutes
4. Specific Gravity: 0.85-0.92
5. Softening point- 150 deg C, Melting Point: 160-170 deg C
6. PP is also attacked by atmospheric oxygen in presence of sunlight
7. It has excellent resistance to common organic solvents
8. It is resistant to insects and microorganisms
9. PP is generally resistant to common chemicals.