PP, all grades

Polypropylene PP is a semi-crystalline commodity polymer that comes in three main variations:

  1. PP Homopolymer (PPH): The simplest and most commonly used PP grade. It is slightly stiffer and stronger than copolymer.
  2. PP Copolymer (PPC): A small portion of PE has been compounded to PPH. This makes the material a little softer while increasing impact resistance. Resistance against stress-cracking is improved as well.
  3. PP Random-Copolymer (PP-RC): During the polymerization process, the polymer chains are randomly arranged. This makes the material transparent and improves visual properties.
  4. (High crystalline PP (hcPP))

Let’s start with PPH and then see why you should or should not prefer PPC or PP-RC instead.

PP Homopolymer or PP in general

Why choose it?

  • Inexpensive
  • The utilization of living hinges (e.g. packages.)
  • Low density, floats in water
  • Fairly ductile, especially when impact modified
  • Excellent chemical resistance
  • Common food-grade plastic
  • Easy to process (if the tendency to warp is eliminated with proper design)
  • Common material, easy to find reference cases

Why not choose it?

  • PP-H can not be considered transparent
  • Low strength and modulus compared to most other plastics
  • Low thermal resistance.
  • Poor UV resistance.
  • Turns brittle in sub-zero temperatures (depends on grade)
Typical applications:
  • Plastic tableware
  • Toys
  • Plumming joints


Why choose PPC over PPH?

  • Better impact resistance
  • Due to compounded PE, remains ductile in sub-zero temperatures

Why not choose?

  • Strength and modulus slightly lower

Typical applications:

  • Snow shovels
  • Hose couplings
  • Plastic chairs
  • Kitchenware
  • Bins


Why choose PP-RC over PPH or PPC?

  • Transparent
  • Improved gloss

Why not choose?

  • Even at its best, the transparency is slightly milky. If you need crystal clear clarity, you have to look at amorphous plastics (keeping in mind their weaknesses).

Typical applications:

  • Storage boxes
  • Packages

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