FIELD

The present disclosure relates generally to polyamide compositions having improved impact resistance/absorption performance, which are particularly useful for injection molded applications.

BACKGROUND

Many varieties of natural and artificial polyamides have found use in various applications due to their high durability and strength. Some polyamide compositions can be formulated to have high melting points, high recrystallization temperatures, fast injection molding cycle times, high flow, toughness, elasticity, chemical resistance, inherent flame retardancy, and/or abrasion resistance. These desirable chemical and mechanical properties can make polyamide compositions suitable for use in constructing such diverse products as cable ties, sports equipment and sportswear, gun stocks, window thermal breaks, aerosol valves, food film packaging, automotive/vehicle parts, textiles, industrial fibers, carpeting, and electrical/electronic parts.

As one example, in the automotive industry there is an environmental need to reduce emissions and to increase the efficiency of fuel consumption. One approach towards achieving these goals is to reduce overall vehicle weight by substituting metal components with thermoplastic ones. And often times, polyamide compositions have been employed to provide such weight reduction in the engine compartment. Some of these polyamide compositions have also been found to be particularly well suited for automotive use due to their aforementioned heat resistance, mechanical strength, and overall appearance. Exemplary applications can include radiator tanks, charge air coolers, fans and shrouds, and push/pull cables.

In addition to the providing of mechanical strength, automotive applications also commonly require impact resistance, e.g., minimization of cabin noise, vibration, and harshness optionally via deformation. These performance characteristics, however, are often associated with conventional polyamide compositions, which have not been designed for imparting increased strength. In view of the existing art, the need therefore remains for improved polyamide compositions that effectively deliver both strength and impact resistance, e.g., toughness, as may be quantified by notched Izod and Charpy impact energy losses.

SUMMARY

In one embodiment, the disclosure is to an impact-modified polyamide composition including (from 5 wt % to 85 wt %) of one or more polyamide polymers, (10 wt % to 60 wt %) of glass fiber, (from 3 wt % to 30 wt %) of an impact modifier, e.g., a modified olefin, for example a maleic anhydride-modified olefin, acrylate, or acrylic, or combinations thereof, (less than 5 wt. %) of a melt stabilizer, e.g., a saturate fatty acid, for example stearic acid, and an optional (less than 5 wt. %) of heat stabilizer. The weight ratio of the impact modifier to the melt stabilizer may range from 1.0:1 to 100:1. The polyamide composition may demonstrate an un-notched Charpy impact energy loss at 23° C. that is greater than 80 kJ/m2and/or a tensile strength greater than 135 MPa. In certain embodiments, the one or more polyamide polymers includes a PA66 polymer and/or a PA6 polymer and/or has a number average molecular weight less than 100,000. In certain embodiments, the impact modifier includes an ethylene-octene copolymer. In certain aspects, the polyamide composition includes nigrosine at a concentration less than 5 wt %. In certain embodiments, the polyamide composition includes carbon black at a concentration less than 5 wt %. In some cases, the polyamide composition demonstrates a 60° tan delta greater than 0.04; and/or a 90° tan delta greater than 0.1. The impact modifier may have a glass transition temperature less than 0° C. In some cases, the weight ratio of the polyamide polymer to the glass fiber may range from 0.1 to 10; and/or the weight ratio of the polyamide polymer to the impact modifier may range from 0.2 to 30; and/or the weight ratio of the impact modifier to the melt stabilizer ranges from 1:1 to 40:1; and/or the weight ratio of the glass fiber to the impact modifier ranges from 0.3 to 20; and/or the weight ratio of the impact modifier to the heat stabilizer ranges from 0.5 to 300. In some embodiments, the polyolefin comprises from 13 wt % to 68 wt % PA66 polyamide polymer; from 25 wt % to 40 wt % glass fiber; impact modifier; from 1 wt % to 2 wt % nigrosine; from 0.1 wt % to 1 wt % heat stabilizer; less than 20 wt % PA6 polyamide polymer; less than 3 wt % carbon black; and less than 1 wt % melt stabilizer. In some cases, the impact modifier comprises a maleic anhydride-modified olefin, acrylate, or acrylic, or combinations thereof; and the weight ratio of the impact modifier to the melt stabilizer ranges from 5 to 50; and the melt stabilizer comprises a saturated fatty acid wherein the polyamide composition; and wherein the polyamide composition demonstrates a tensile elongation greater than 2.5%; and an un-notched Charpy impact energy loss at −40° C. that is greater than 65 kJ/m2. In some cases, the polyamide composition comprises from 13 wt % to 68 wt % of a PA66 polyamide polymer; from 25 wt % to 40 wt % glass fiber; and the polyamide composition has a notched Charpy impact energy loss at 23° C. greater than 11 kJ/m2.

In another embodiment the disclosure relates to a method of preparing a polyamide composition. The method includes providing one or more polyamide polymers, glass fiber, an impact modifier, and an optional heat stabilizer. The method further includes combining the one or more polyamide polymers, the glass fiber, the impact modifier, and the heat stabilizer to produce the polyamide composition. In certain aspects, the method further includes providing nigrosine, and adding the nigrosine to the polyamide composition. In certain embodiments, the method further includes providing carbon black, and adding the carbon black to the polyamide composition. In some aspects, the method further includes providing a melt stabilizer, and adding the melt stabilizer to the polyamide composition.

In another embodiment, the disclosure is to an injection molded article. The article includes any of the provided polyamide compositions.

