Mechanical Properties Of Polymer Essay

Mechanical Properties of Polymers

Properties:

Definition:

“Properties are the Characteristics of the materials to classify them on the basis of their behavior.”

Polymers:

Definition:

“Polymer is a combination of two words “Poly” means “Many” “Mer” means “Unit”. So the polymer term means combination of small units to form a larger molecule/compound.”

Mechanical Properties:

Definition:

“The properties which are mostly related to the physical behavior of the materials.”

Mechanical properties Include:

 Stress-Strain Behavior

 Impact

 Fatigue

 Viscoelasticity

Explanation:

These types of properties are the way to find out the explicit situation to find out their conduct. These properties contain all the mechanical properties that are act on

This behavior is similar for the Polymers as for the Metals. The Material behaves plastically within the Elastic Region. First, it goes on deformation within the elastic limit and then it goes on plastically deformation by applying more and more stress till it breaks.

 Rubber Like Behavior:

The Curve-C shows the rubber like behavior of the polymers. The Polymer behaves rubber like when the Stress is applied on it.

 Modulus Of Elasticity:

Modulus of Elasticity in case of Metals is much higher than that of Polymers (ranges between 48-410GPa). We can find the percentage elongation in the same way as for the metals. We can see from Figure1: Curve-B the Yield Point and the Fracture point is the same.

Some important key points for the Polymers in case of modulus of Elasticity:

 Maximum Tensile Strengths for polymers ranges from 100MPa (1500 psi).

 Maximum Tensile Strength for metals is 4100MPa (600000 psi).

 Metals rarely elongates plastically to more than 100%.

 Some elastic polymers can extend more than 1000%.

 Polymers are susceptible towards heat

Viscoelastic relaxation modulus:

Viscoelasticity behavior of a polymer depends on the following factor

 Time

 Temperature

Relaxation modulus is given by

Er (t) =σ/ eo

In this modus operandi originally the stress is useful hastily in tension to a set and relatively low strain level. Strain is precise as a task of time while temperature is seized constant. In this test the stress is found to be diminishing with time due to molecular relaxation which takes place in polymer.

Its key features are

1) Magnitude of Er (t) decrease with time.

2) Curves are displaced to lower Er(t) level with increasing temperature.

9: Viscoelasticity creep:

At constant stress level many polymers are disposed to time dependent deformation; such condition is called Viscoelasticity creep.

This stipulation is noteworthy at room temperature under the stresses which are less the yield strength of the material.

Creep consequences are representing as time needy creep modulus Ec (t) defined as

Ec (t) =σ/e(t) σ = constant applied stress e(t) =time dependent strain

• The creep modulus is temperature insightful.

• Magnitude increase with time.

• Propensity decrease when degree of crystalline