Polypropylene (PP) plastic

What is polypropylene (PP), and what is it used for?

Polypropylene (PP) is a thermoplastic “additional polymer” made from a combination of propylene monomers. It is used in a wide variety of applications including packaging for consumer products, plastic parts for various industries including the automotive industry, specialty equipment such as living hinges and textiles. lucky.(Polypropylene (PP) plastic)

Polypropylene has a relatively smooth surface, making it an alternative to plastics such as Acetal (POM) in low-friction applications such as gears or as a point of contact for furniture.

Perhaps a negative aspect of this quality is that it can be difficult to bond Polypropylene to other surfaces (i.e. it does not adhere well to some adhesives that work well with other plastics and sometimes requires soldering in the case must form a connection).( see more: PP Blowing Grade)

Although polypropylene is smooth at the molecular level, it has a relatively high coefficient of friction - which is why acetal, nylon or PTFE would be used instead. Polypropylene also has a low density compared to other common plastics, helping to save weight for injection molded Polypropylene parts manufacturers and distributors.

It has exceptional resistance at room temperature to organic solvents such as fats but can oxidize at higher temperatures (a potential problem during injection molding).

One of the main benefits of Polypropylene is that it can be manufactured (via CNC or injection molding, heat forming or bending) into a living hinge. Live hinges are extremely thin pieces of plastic that can be bent without breaking (even over an extremely high range of motion of nearly 360 degrees).( see more: PP Injection Grade)

They are not particularly useful for structural applications such as holding a heavy door but are particularly useful for non-load bearing applications such as the cap of a bottle of ketchup or shampoo. Polypropylene is particularly suitable for live hinges because it does not break when bent repeatedly.

One of the other advantages is that polypropylene can be CNC machined to include a live hinge allowing for faster and less expensive prototype development than other prototyping methods. The innovative mechanism is unique in our ability to machine live hinges from a single piece of polypropylene.

Another advantage of Polypropylene is that it can easily copolymerize (basically combine into a composite plastic) with other polymers such as polyethylene. The copolymerization process dramatically changes the properties of the material, allowing for more robust engineering applications than is possible with pure polypropylene (which is itself a more commodity plastic).

The characteristics mentioned above and below mean that polypropylene is used in many applications: dishes, trays, dishwasher-safe cups, etc., opaque take-away containers and many toys.

What are the characteristics of Polypropylene?

Some of the most important properties of polypropylene are:

Chemical resistance: Bases and dilute acids do not react readily with polypropylene, which makes it a good choice for containers with such liquids, such as detergents, first aid products, etc.

Elasticity and toughness: Polypropylene will behave with elasticity within a certain deflection range (like all materials), but it will also undergo plastic deformation early in the deformation process, because so it is often considered a "hard" material. Toughness is a technical term defined as the ability of a material to deform (plastic, inelastic) without breaking.( see more: PP Film Grade)

Fatigue Resistance: Polypropylene retains its shape after many twists, turns, and/or crimps. This property is especially valuable for living hinges.

Insulation: Polypropylene is very resistant to electricity and is very useful for electronic components.

Transmissibility: Although Polypropylene can be made transparent, it is often manufactured to have a naturally opaque color. Polypropylene can be used for applications where some light transfer is important or where it has aesthetic value. If high transmittance is desired, resins such as Acrylic or Polycarbonate are better choices.

Polypropylene is classified as a “thermoplastic” material (as opposed to a “thermosetting”) material with regard to how the plastic responds to heat. Thermoplastic materials become liquid at their melting point (about 130 degrees Celsius in the case of polypropylene).

A key useful property of thermoplastics is that they can be heated to the melting point, cooled, and reheated without significant deterioration. Instead of burning, thermoplastics like polypropylene will liquefy, allowing them to be easily injection molded and then recycled.( see more: PP Natural Off-grade)

In contrast, thermoset plastics can only be heated once (usually during injection molding). The first heating causes the thermoset material to solidify (similar to 2-part epoxy) resulting in an irreversible chemical change. If you try to heat a thermoset plastic to a high temperature a second time, it will simply burn. This characteristic makes thermoset materials a poor recycling candidate.