Rakesh Ingale

 POLYPROPYLENE 

• Polypropylene is produced by polymerization of propylene using a catalyst in solution, mass or gas phase. For the polymer, propylene monomer is polymerised to make polypropylene 
• Raw material is propylene 

Benefits : 

• A cost-effective way to achieve high-strength concrete and other construction materials
• Is compatible with many processing techniques, which means there are many applications of polypropylene
• Offer great chemical resistance to a lot of common solvents
• Thanks to its mechanical properties it can get a good balance between stiffness and impact
• Is resistant to freeze-thaw weathering
• Has low moisture regain, making it a good choice even for humid environments.

Manufacturing process : 

1. Extrusion: L/D=30, compression ratio=1:3.5
2. Metering: one or more spinning gear pumps receives the molten polymer and sends it through the spinning pack to homogenize the product, feed the spinning pack at a constant rate, and prevent fluctuation due to screw extruder.
3. Spinning: the spinning pack consists of three parts-filters, distributor (which distributes the molten polymer over to die surface) and the die. The diameter of the die varies from 0.5 to 1.5mm, depending on the denier required.
4. Quenching: newly extruded filaments are cooled in a good “box” which will distribute 3 m3/min of cool air without damaging the filaments.
5. Finishing: to improve antistatic and reduce abrasion.
6. Hot Stretching: to enhance the physico-mechanical properties.
7. Crimping: to improve the bulk.
8. Thermosetting: it is a treatment in hot air or steam that removes the internal stresses and relaxes fibers. The resultant fibers are heat-set with increased denier.
9. Cutting: fibers are cut into 20 to 120 mm length depending on whether they are intended for cotton or woolen system.

   Steric structure : 

There are three steric structure persent in polypropylene this are isostactic, syndiotactic , atactic. 

   Isostactic 

In this method all sides methyl group occur in the same side and in the same direction to the plane formed by carbon atoms of the linear chain.
Isostactic polypropylene molecules can pack closely either in a monoclinic from or in hexagonal from 

So the chain is crystalline in nature and more suitable for textile purpose.

   Syndiotactic 

In the structure, methyl group are arranged above and below the plane determined by zig - zag linear chain by carbon atoms 

   Atactic 

In this structure, methyl group are arranged randomly in both side of plane of the zig - zag main carbon atoms 

So this polymer is amorphous, rubber like substance and not suitable for textile purpose.

      

     Properties : 

Factors 

Properties 

Density 

0.91 gm/cc

Moisture regain 

0 %

Tensile strength 

3.5 - 5.5 gpd

Melting point 

165 ° C

Softing temperature 

140°C

Elongation % 

40 - 100 %

Abrasion resistance 

Good 

Initial modules 

60 - 70 gpd

Elastic recovery 

97 % At 2 % extension 

Glass transition temperature 

-20°C

LOI ( limiting oxygen index)

19% easily burn 

Application:

1. Polypropylene is often added to the cement matrix to improve the resistance of concrete
2. Roads
3. Tunnels
4. High-performance concrete
5. Industrial pavements
6. Is a simple and rapid solution for reinforcement
7. Polypropylene fibers are often used in food packaging, absorbent pads, and wrapping film because they are water resistant and don't absorb moisture.
8. Polypropylene fibers can be used to create fabrics that absorb heat during the day and control heat loss at night.
9. Polypropylene fibers are also used in a variety of other products because of their chemical resistance, durability, and abrasion resistance
10. These fibre are also used in apperal textile and home textile like hand knitting fancy yarn, knitted fabric and blanket.       

Reference : textile learner. Com