Surface-Treated Mica Minerals for Polyamide 6

Muscovite and phlogopite micas are commonly used in polyamide 6 because of their equilibrated mechanical behavior but even more due to their ability to reduce isotropically the shrinkage of the compound as well as increasing the HDT - both resulting in extremely low warping materials (Zilles 2006). This is one of the prerequisites for using PA6 compounds as functional parts in environments being subjected to high temperature changes. HDT As typically are in the region of 120-140 °C at 20% filler load (65 °C on the unfilled PA6). Tables 4 and 5 summarize the behavior of a series of surface-treated Aspanger mica and TREFIL™ phlogopite mica products in polyamide 6 at 20% filler load. All results were obtained on the “dry” injection mold parts.

Advantages of using phlogopite mica of the TREFIL™ type at 20% filler load compared to the unfilled polymer are:

An increase of up to 4% in tensile strength

• • An increase of up to 92% in elastic modulus
• • Increase in notched IZOD strength
• • A typical increase of 90% in HDT A
• • Reduction of the absolute shrinkage up to 35% in all dimensions
• • Better isotropic behavior (reduction of warpage)

Advantages of using Aspanger muscovite mica at 20% filler load compared in polyamide to the unfilled polymer are:

• • An increase of up to 8% in tensile strength
• • An increase of up to 83% in elastic modulus
• • Increase in notched IZOD strength
• • Reduction of the absolute shrinkage up to 32% in all dimensions
• • The same isotropic behavior (reduction of warpage)

Muscovite and phlogopite show clear increase of mechanical and thermal properties of polypropylene copolymers and polyamide 6. Whenever equilibrated mechanical behavior (stiffness/brittleness ratio) and isotropic behavior resulting in low warpage are a concern, they show clear advantages in comparison to, e.g., talc or to some extent even glass fibers. Especially in car industry, these mica types will make polymer compounds of PA and PBT available being used in thermal shock environment and high temperature ranges. Whenever scratch resistance and low warpage are a concern, mica shows clear advantages over talc or non-isotropic fillers in polypropylene.

Table 4 Properties of phlogopite mica products at 20% filler load in PA6

Table 5 Properties of surface-treated Aspanger mica products at 20% filler load in PA6