Description: 521 synthetic resins or natural rubbers -- part of the class 520 series / 521 synthetic resins or natural rubbers -- part of the class 520 series/() synthetic resins (class 520, subclass 1) (50) cellular products or processes of preparing a cellular product, e.g., foams, pores, channels, etc. (77) preparing a cellular product by decomposition of a solid polymer; or process of forming a composition containing a solid polymer which decomposes so as to subsequently form a cellular polymer, or composition therefrom
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