Ethylene Vinyl Acetate (EVA)

Ethylene vinyl acetate: (also known as EVA) is the copolymer of ethylene and vinyl acetate. The weight percent vinyl acetate usually varies from 10 to 40%, with the remainder being ethylene. It is a polymer that approaches elastomeric materials in softness and flexibility, yet can be processed like other thermoplastics.

The material has good clarity and gloss, barrier properties, low-temperature toughness, stress-crack resistance, hot-melt adhesive water proof properties, and resistance to UV radiation. EVA has little or no odor and is competitive with rubber and vinyl products in many electrical applications.

These resins are not hygroscopic and may be used as received without need for drying.

At temperatures above 220ºC, EVA resins can evolve toxic fumes.

Injection moulding: Experience has shown screws normally used for injection molding of low density polyethylene to be satisfactory.

Melt temperature : 150-200°C

Mold temperature : 15-40ºC

Extrusion moulding: A three-zone screw with a total L/D ratio of at least 20 is recommended.

Melt temperature is, generally, in the overall range of 95-205ºC .

The melt temperature depends upon the melt index of the resin, the % vinyl acetate and the part configuration.

APPLICATIONS OF EVA

Industrial 

Flexible hoses, tubings, base pads, spirit bottling lines

Mechanical

Used as impact modifier to improve impact strength in plastics, cable sheathing moulded auto parts.

Sports

Inner shoe sole and other shoe components, toys

Packaging

Films for packaging of meat and poultry products, ice cube trays, disposable gloves, vacuum cleaner hoses

Strengths:

1. Highly flexible , even at low temperatures

(-25°C)

2. Highly compatible with a lot of elastomers, TP and other materials (SBr, EPDM, TPE, PE, PVC, asphaltum ...)

3. Better tear resistance than LDPE

4. Excellent resistance to environmental stress

cracking

5. FDA compliant

6. Good UV and ozone resistance

Limitations:

1. Poor heat resistance

2. Reduced barrier properties compared to

LDPE

3..Attacked by polar solvents, hydrocarbons, oxydants and strong acids

4. Reduced creep resistance, compared to

LDPE.

Properties 

1. Flexible and low temperature toughness (-70 C)

2. Chemically inert

3. Good clarity

4. Good stress cracking resistance

5. Excellent impact strength

6. Higher VA content resins possess excellent toughness

7. Better ozone resistance than rubbers

8. High co-efficient of friction

9. Good resistance to oil and grease

10. Non toxic in nature

11. Superior out door stability than LDPE