Thermoplastic Elastomers

Thermoplastic Elastomers:

Important Thermoplastic Polyurethane Elastomers

1. POLYURETHANE ELASTOMERS

2. POLYOLEFIN ELASTOMERS

3. POLYESTER ELASTOMERS

4. STYRENE ELASTOMERS

5. POLYAMIDE ELASTOMERS

6. ELASTOMER- THERMOPLASTIC BLENDS

Thermoplastic Elastomers are made by copolymerising  two or more  monomers.

TPE’s contains hard and soft segments.

TPE’s properties can be controlled by varying monomer ratios  and length of the hard soft segments.

TPE’s can be reclaimed and recycled.

Thermoplastic  Polyurethane Elastomers (TPU):

1. Polyurethanes are characterized by the presence of urethane linkages.

 - CO-NH-(R)-NH-CO-O- (R’)-O-

2. Urethanes are reaction product of a diisocyanate and diols.

3. Abrasion resistance of the urethane is outstanding among elastomers.

TPU-Structure and properties:

1. Polyurethane consist of hard and soft segments.

2. The hard segments control the rigidity and strength - Diisocyantes- MDI, HMDI

3. The soft segment controls low temperature properties solvent resistance and weathering - polyesters, polyethers.

TPU-Additives:

1. Mold release agents are the most commonly employed additives

2. Polyester based TPUs are stabilized by aromatic carbodiimides

3. Sterically hindered phenols, amines are used against degradation by light, oxidation

4. Friction can be reduced by the addition of graphite's, silicone oil, fluorinated hydrocarbons

5. Calcium carbonate, organic fibers and glass fibers are used as reinforcing fillers

TPU-Synthesis:

Thermoplastic polyurethanes are made by mixing the isocyantes and alcohols at temperatures above 80 C. for optimum results, the ratio of isocyanate groups and alcohol's ,should be close to one. 

TPU-General characteristics:

1. High tensile strength

2. Excellent tear resistance

3. Excellent flex life

4. Excellent abrasion resistance

5. High scratch resistance

6. Easy printability

7. Good thermal properties

8. Good chemical resistance

9. Low gas permeability

10. Excellent low temperature resistance

11. Good migration resistance 

13. Good ozone resistance.

Processing: Thermoplastic polyurethans are normally supplied as granule in moisture proof contains. They can be processed by usual methods for thermoplastic materials such as injection moulding, extrusion, blow moulding and clendering.

TPU blends:

1. TPU as a minor component with Poly(butylene terephthalate), polyoxymethylene, epoxy resin and unsaturated polyester resin

2. TPU as equal component with polycarbonate and ABS

3. TPU as major component with ABS

TPU Applications:

1. Automotive- exterior body parts, automobile interiors, body side mouldings, fender extensions etc.,

2. Electrical/electronics - wire and cable jacketing, hose jackets, sheets, cable cores & seals etc.,

3. Films and sheets- adhesive film fro garment labels, conveyor belts, gaskets etc.,

4. Tubings - air instrument tubing, blood tubing, dental tubing, fuel hose jackets etc.,