Mixing and blending method internal

Within these limitations, the internal-standard method has enjoyed wide application in mineral and ore processing. It is essential that the reference element be intimately mixed with the sample on a micrometer scale. Various procedures have been used to achieve this blending, such as grinding the sample and reference with an abrasive such as silicon carbide, or by fusion using borax, carbonate, or pyrosulfate as a flux. 

A serious limitation of polystyrene in many applieations is its brittleness and a number of attempts have been made to improve the polymer in this respect. The most successful approach to this problem has been the addition of rubbery materials (usually 5-15%) to the polymer and rubber-modified polystyrene (commonly referred to as impact polystyrene) is an important commercial material. In fact, production of impact polystyrene currently exceeds that of crystal polystyrene. Several rubbers have been tried for the preparation of impact polystyrene but cis-l,4-polybutadiene is the most commonly used. The method of mixing the polystyrene and rubber has a profound effect on the properties of the product. Simple blending of the two polymers in, for example, an internal mixer or two-roll mill gives a product... 

---