Unusual types of gramophone records Hi-Fi was a system of proprietary records and players designed for use in automobiles, utilizing a slower play speed and high stylus pressure. With their origin stretching back to the dawn of recorded sound at the turn of the 20th century, flexible recording media have been made from a variety of materials including foil, paper, and–in the 1950s–thin flexible vinyl known as flexi discs. Thin, flexible paper-based records were briefly popularized in the 1930s by Hit of the Week Records and Durium Records. "Melody Cards" were popular in the late 1950s. They took the form of an oversized rectangular postcard
Polymer-bonded explosive altered, e.g. by Ostwald ripening. Thermochemical decomposition starts to occur at the crystal nonhomogeneities, e.g. intragranular interfaces between crystal growth zones, on damaged parts of the crystals, or on interfaces of different materials (e.g. crystal/binder). Presence of defects in crystals (cracks, voids, solvent inclusions...) may increase the explosive's sensitivity to mechanical shocks. Polymer-bonded explosive A polymer-bonded explosive, also called PBX or plastic-bonded explosive, is an explosive material in which explosive powder is bound together in a matrix using small quantities (typically 5–10% by weight) of a synthetic polymer. PBXs are normally used for explosive materials that are not easily melted