How to Calculate the Density of a Polymer Blend

Polymers can be blended to impart desired properties.
••• Ableimages/Lifesize/Getty Images

A polymer is a unique molecule that is made up of many identical units. Each individual unit is called a monomer (“mono” means one and “mer” means unit). The prefix “poly” means "many" -- a polymer is many units. Often, however, different polymers are blended together to impart unique or desirable chemical or physical properties. Each type of polymer has a certain density (mass per unit volume). The density of a polymer blend is the sum of the mass fractional density of each type of polymer.

    Determine the chemical composition of a polymer blend. For instance, polypropylene could be blended with polyethylene. If the blend has 70% polypropylene and 30% polyethylene, then the mass fractions are 0.70 for polypropylene and 0.30 for polyethylene

    Determine the density of each polymer type using the specific gravity and comparing that to water (specific gravity = 1.0). The "Polymer Technology Dictionary" contains the specific gravities of most common polymers. Polypropylene has a specific gravity of 0.89 and polyethylene has a specific gravity of 0.92. Since the density of water is 62.37 pounds per cubic foot, the specific gravity of other materials is multiplied by this density to determine a density relative to water. For polypropylene, this works out to be 0.89 x 62.37, or 55.51 pounds per cubic foot. For polyethylene, it works out to be 0.92 x 62.37, or 57.38 pounds per cubic foot.

    Determine the density for the polymer blend by adding the mass fraction densities together. This is done with the formula 0.70 x 55.51 (polypropylene) + 0.30 x 57.38 (polyethylene) for an answer of 56.07 pounds per cubic foot for the blend.

    Things You'll Need

    • Pen
    • Paper
    • Calculator

Related Articles

Ace Your Middle School Science Fair with These Science...
What Is HDPE Plastic?
How to Calculate the Degree of Polymerization
What Is Polyethylene Glycol?
What Are the Raw Materials of Plastic Bottles?
Difference Between Density & Mass
Differences Between HDPE Plastic and Polyethylene Plastic
How to Calculate Composite Density
How to Dissolve Polyethylene
Urethane vs. Polyurethane
Neoprene Vs. Natural Rubber
The Properties of Polyethylene
How to Convert Density to a Specific Gravity
What Are the Materials Used for Spur Gears?
Alternative Solvents to Benzene
Conversion of PPM to Micromoles
How to Write an Equivalent Fraction With a Given Denominator
What Are the Monomers of Triglycerides?
How to Convert Milliliters to Grams