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Polypropylene (PP), also known as polypropene, is a thermoplastic polymer used in a wide variety of applications. It is produced via chain-growth polymerization from the monomer propylene . Polypropylene belongs to the group of polyolefins and is partially crystalline and non-polar .
The onset of thermal degradation dictates the maximum temperature at which a polymer can be used. It is an important limitation in how the polymer is manufactured and processed. For instance, polymers become less viscous at higher temperatures which makes injection moulding easier and faster, but thermal degradation places a ceiling temperature ...
Polypropylene sheets are used for stationery folders and packaging and clear storage bins. Polypropylene is defined by the recyclable plastic number 5. Although relatively inert, it is vulnerable to ultraviolet radiation and can degrade considerably in direct sunlight. Polypropylene is not as impact-resistant as the polyethylenes (HDPE, LDPE).
The PP and PE components of a blend constitute the "crystalline phase", and the rubber and branched PE chains and PE/PP end groups gives the "amorphous phase". If PP and PE are the dominant component of a TPO blend then the rubber fraction will be dispersed into a continuous matrix of "crystalline" polypropylene.
Polymer degradation is the reduction in the physical properties of a polymer, such as strength, caused by changes in its chemical composition.Polymers and particularly plastics are subject to degradation at all stages of their product life cycle, including during their initial processing, use, disposal into the environment and recycling. [1]
Thermal depolymerization (TDP) is the process of converting a polymer into a monomer or a mixture of monomers, [1] by predominantly thermal means. It may be catalyzed or un-catalyzed and is distinct from other forms of depolymerization which may rely on the use of chemicals or biological action.
The Relative thermal index (RTI) is a characteristic parameter related to the ability of plastic materials to resist thermal degradation. The RTI is part of the longterm thermal aging program (LTTA) described in the UL 746B standard from UL .
These thermal greases have low electrical conductivity and their volume resistivities are 1.5⋅10 15, 1.8⋅10 11, and 9.9⋅10 9 Ω⋅cm for 860, 8616 and 8617 respectively. The thermal grease 860 is a silicone oil with a Zinc Oxide filler and 8616 and 8617 are synthetic oils with various fillers including Aluminum Oxide and Boron Nitride.