Plastic tool box - what type of PP is appropriate


I am designing plastic tool box, and I am almost finished with this.

I must select material for it, and I know PP fits the best, however I miss what min. Flexural Modulus, MFR and Impact Resistance appropriate type of PP should have?

I was given a lot of suggestions from PP suppliers. Problem is that Flexural Modulus varies form 900 to 1600 MPa

Impact Resistance form 3 - to 40 kJ/m^2. If I say I am little confused I won`t be 100 % accurate.


  1. type of PP for top[560 x 260 x 100 mm] and bottom [560 x 260 x 200 mm] part of tool box(wall thickness 2 mm).
  • especially I am interested in min. MFR, Flexural modulus, and Izod Impact Strength (notched) at 23 C[ISO 180]
  1. type of material for transparent but smoked covers [260 x 104 x 15] - wall thickness 1.6 mm
  • PC vs PP vs PET with the regards to “smoked” effect

  • min. MFR, Flexural modulus, and Izod Impact Strength (notched) at 23 C[ISO 180]

thank you in advance

Get sample parts made from 2-3 resins.

Test the parts.

Determine which is best for your application.

I remember having a discussion with a high-level executive from a very large tool brand. He was describing to me how fillers are being added to PP injection molded products. I believe the ‘smoked’ effect you’ve indicated is from one of these fillers, more precisely, talc. You get the added benefit of a less costly material, lighter weight product, no loss of strength/integrity and also the visual effect.

thanks for feedback guys

there is no injection mold ready to make any testing at this moment possible

I miss min. MFR, FM(flexural modulus) and durability(Impact Resistance) values to start selection of materials.

Hi proe-warsztat

If you you know PP is OK,before you make a injection mold ,you need’t know the accuracy .Because the pp shrink rate is same,after you have a mold ,you can provide different material to inject,then you can test these sample to decide which kind of pp to use .

For a tool box, I wouldn’t worry too much about flexural modulus, unless you have molded-in snaps. If you do have molded-in snaps, then that solves your problem, as the flexural modulus will be a design variable, along with wall thickness in your snaps. Check a PP design guide for these formulas.

You also shouldn’t need to worry about flow rate. If the PP you’ve picked is provided in pellets, it’s suitable for injection molding. Your toolmaker will handle the exact flow design.

Pick the highest impact resistance you can afford. I’d invest in this though, it’ll affect your overall quality drastically and will cost you more in the long run if you cheap out on your plastic.

What Mirk said. I’d just add to keep fillers to a minimum, especially if you’re planning on “living” hinges and/or snaps. Fillers will in some cases will lead to premature failure(s).

there are no snaps in components made of PP.

there are transparent flaps made of PC with molded-in snaps.

Preliminary in selected PP Impact Copo with following spec:

  • FM: 1300 MPa

  • MFR: 10g /10 min

  • Charpy Notched Impact Strength IS 179/eA: 8 kJ/Mpa (23C)