April 2018

The Effect of Copper Phthalocyanine Blue Pigment on Stress Cracking of HDPE

Historically copper phthalocyanine blue and green shades of pigment are known to nucleate polyolefin molded parts and cause stress cracking. A classic example of stress cracking is shown in this molded HDPE blue bucket sold at known hardware stores. The bottom is a thinner wall than the sides of the bucket and on standing stress cracked down the middle of the bucket. Examination of the area showed the resin was nucleated.

In order to avoid the adverse effect on nucleation and stress cracking and loss of impact properties the development of a new blue pigment for polyolefin resins called OMPF (organo-mineral pigment filler) from Endex International and Stabilization Technologies LLC was introduced that provides comparable red and green shade blue to the resin without nucleation and increases impact and flexural strength of the molded part. See examples below.

Zeodex OMPF Colorants for Plastics

Masstone and Tint at 200 ppm final in HDPE with two different shades of blue

Masstone and Tint at 200 ppm colorant final in HDPE with two different shades of blue

The colorants are supported with Alterin 110 another product from Endex International that allows excellent dispersion and transparent colors to the HDPE as shown above.

Molded Large Parts HDPE: