Described herein are methods and processes of manufacturing irradiation crosslinked polypropylene foam. In some embodiments, this includes extrusion of all material components, including a liquid crosslinking agent, to manufacture extruded structures for production of irradiation crosslinked polypropylene foam.

Foamable polymeric compositions comprising a peroxide-modified linear low-density polyethylene, which comprises the reaction product of a peroxide and a linear low-density polyethylene, and a blowing agent. The peroxide-modified linear low-density polyethylene is thermoplastic. Also disclosed are foamed polymeric compositions prepared from such foamable polymeric compositions and methods for making such foamed polymeric compositions. The foamed polymeric compositions described herein are suitable for use in a variety of articles of manufacture, particularly in the wire and cable industry.

A method is disclosed for manufacturing a structured polymeric material. In the method, a body is provided comprising a substantially homogenous precursor polymeric material. An interference pattern of electromagnetic radiation is set up within the body to form a partially cross-linked polymeric material, the interference pattern comprising maxima and minima of intensity of the electromagnetic radiation, the interference pattern thereby causing spatially differential cross linking of the precursor polymeric material to form crosslinked regions having relatively high cross linking density and non-crosslinked regions having relatively low cross linking density, the crosslinked regions and non-crosslinked regions corresponding to the maxima and minima of intensity of the electromagnetic radiation, respectively. The partially cross-linked polymeric material is then contacted with a solvent to cause expansion and crazing of at least some of the non-crosslinked regions to form a structured polymeric material containing pores.

The invention relates to the field of physical foaming. The method includes the following steps: crosslink the foaming matrix to obtain a plurality of crosslinked prefabricated products, add the crosslinked prefabricated products into a reaction reactor filled with polar liquid, add nitrogen for foaming, relieve pressure, and heat for foaming to obtain the foaming materials. In the polar liquid system, the inventor finds that the ratio of the distance between the adjacent crosslinked prefabricated products to the thickness of the prefabricated products as well as the difference between the melting temperature of the polymer and the temperature of the polar liquid need to be controlled to promote the adjacent prefabricated products in full contact with the polar liquid, and prefoaming can be carried out under the condition of low temperature difference, namely, at the low temperature of the polar liquid.