| abstract |
Beta nucleation agents are used to impart improved properties in polypropylene materials such as sheets and speciality items, for example, geogrids. A convenient way of incorporating beta-nucleating agents into polypropylene used to fabricate an extruded product is through the use of a concentrate. A concentrate is defined as a highly loaded, pelletized polypropylene resin containing a higher concentration of nucleating agent then is desired in the final extruded sheet (product). The nucleating agent is present in the concentrate in a range of 0.01% to 2.0% (100 to 20,000 ppm), more preferably in a range of 0.02% to 1% (200 to 10,000 ppm). Typical concentrates are blended with non-nucleated polypropylene in the range of 0.5% to 50% of the total polypropylene content of the extruded product. A preferred range is between 1% and 10% of the total polypropylene content of the extruded product. A preferred concentration range of nucleant in the final geogrid product is 0.0001% to 0.1% (1-1000 ppm), most preferably 2-200 ppm. A concentrate can also contain other additives such as stabilizers, pigments, and processing agents. A concentrate containing a beta-nucleating agent cannot contain any additives which nucleate the alpha crystal form of polypropylene. Methods for the manufacture and use, as well as compositions incorporating these concentrates, are described. |