Plastic formulations physical stability

Stabilizers are included in aU plastics formulations to stop or slow the loss of physical properties, which occurs when polymers react with ultraviolet radiation, heat, oxygen and ozone. Stabilizers are not usually volatile because they are designed to remain in the plastic for its lifetime and are present in small quantities comprising up to 0.5 per cent of the weight of the plastic, so it is necessary to separate them from the rest of the formulation in order to identify them. 

Eoamable compositions in which the pressure within the cells is increased relative to that of the surroundings have generally been called expandable formulations. Both chemical and physical processes are used to stabilize plastic foams from expandable formulations. There is no single name for the group of cellular plastics produced by the decompression processes. The various operations used to make cellular plastics by this principle are extmsion, injection mol ding, and compression molding. Either physical or chemical methods may be used to stabilize products of the decompression process. 

Understanding the condensed-phase properties of HE materials is important for determining stability and performance. Information regarding HE material properties [such as the physical, chemical, and mechanical behaviors of the constituents in plastic-bonded explosive (PBX) formulations] is necessary for efficiently building the next generation of explosives as the quest for more powerful energetic materials (in terms of energy per volume) moves forward.1... 

Differences between the ingredients in a formulation may be essentially of a chemical nature, but also may be physical (such as the ranges of particle sizes)—and quite often both chemical and physical variations are found in practice. In order to match a particular material consistently it is not sufficient merely to know even the precise formulation in terms of polymer, plasticizer, heat stabilizer, filler, anti-static agent, colour, and so forth each of the components in the formulation must be supplied consistently to a tight... 

Because of the importance of controlling the solid-state properties a great deal of interest has been generated around understanding the role of water in the formulation since water can act as a plasticizer that will deteriorate both chemical (i.e.. protein degradation) and physical (i.e., particle fusion, cake collapse, crystallization) stability. How dry this formulation needs to be depends on the glass transition of the formulation relative to the storage conditions and the so called zero temperature (55). 

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