All About Polypropylene (PP) Plastics

Polypropylene (PP) is a thermoplastic "addition polymer" composed of propylene monomers. It is used in a variety of applications including packaging of consumer goods, plastic parts in various industries including the automotive industry, living hinges such as special equipment, and textiles. Polypropylene also has a lower density compared to other common plastics. It is exceptionally resistant to organic solvents such as fats at room temperature, but is susceptible to oxidation at higher temperatures (which can be problematic at high temperatures).

Another advantage of polypropylene is that it can easily be copolymerized with other polymers (essentially combined into a composite plastic) polyethylene. Copolymerization significantly alters the properties of PP materials, allowing for stronger engineering applications than pure polypropylene.

Polypropylene is used in a variety of applications: PP plastic sheets are often used in thermoformed food packaging boxes, trays, cups, etc. PP also makes opaque to-go containers, as well as many toys.

Polypropylene is a colorless, odorless, non-toxic, translucent solid substance. Polypropylene is a thermoplastic synthetic resin with excellent properties, which is a colorless and translucent thermoplastic lightweight general-purpose plastic. It has chemical resistance, heat resistance, electrical insulation, high-strength mechanical properties and good high wear-resistant processing properties, etc., which makes polypropylene rapidly used in machinery, automobiles, electronic appliances, construction, textiles, packaging since its inception. It has been widely developed and applied in many fields such as agriculture, forestry, fishery and food industry.
 

Some of the most important properties of polypropylene

Chemical Resistance: Diluted alkalis and acids do not easily react with polypropylene, which makes it a good choice for containers of such liquids, such as cleaning agents, first aid products, etc.

Elasticity and Toughness: Polypropylene acts elastically (like all materials) within a certain range of deflection and also undergoes plastic deformation early in the deformation process, so PP is generally considered a "tough" material.

Fatigue Strength: Polypropylene retains its shape after extensive twisting, bending and/or bending. These properties are particularly valuable for the manufacture of living hinges.

Insulation material: Polypropylene has a high electrical resistance and is very useful for electronic components.

Transmittance: Although polypropylene can be made transparent, it is usually a natural opaque color. Polypropylene can be used in some applications where transmission of light is important or aesthetically valuable. If high light transmission is desired, then acrylic or polycarbonate plastics are better choices.

Polypropylene is classified as a "thermoplastic" (as opposed to "thermoset") material, which has to do with how the plastic responds to heat. Thermoplastic materials become liquid at their melting point (the temperature of polypropylene is about 130 degrees Celsius). The main useful property about thermoplastics is that they can be heated to their melting point, cooled, and reheated without appreciable degradation. Instead of burning, thermoplastics like polypropylene liquefy, which makes them easy to liquefy injection mold and then recycle. In contrast, thermosets can only be heated once (usually during the injection molding process). The first heat sets the thermoset (similar to a two-part epoxy), resulting in irreversible chemical changes. If you try to eat thermoset to high heat, it will burn the second time. This property makes thermoset materials difficult to recycle.
 

What are the advantages of polypropylene?

¡ñ Polypropylene is readily available and relatively inexpensive.
¡ñ Polypropylene has high flexural strength due to its semi-crystalline nature.
¡ñ The surface of polypropylene is relatively smooth.
¡ñ Polypropylene is very resistant to moisture absorption.
¡ñ Polypropylene has good chemical resistance to various bases and acids.
¡ñ Polypropylene has good fatigue resistance.
¡ñ Polypropylene has good impact strength.
¡ñ Polypropylene is a good insulator.
 

What are the disadvantages of polypropylene?

¡ñ Polypropylene has a high coefficient of thermal expansion, which limits its use at high temperatures.
¡ñ Polypropylene is susceptible to UV degradation.
¡ñ Polypropylene is less resistant to chlorinated solvents and aromatic hydrocarbons.
¡ñ Polypropylene is difficult to paint due to its poor adhesion properties.
¡ñ Polypropylene is highly flammable.
¡ñ Polypropylene is easily oxidized.