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Due to the tertiary carbon atom, PP is chemically less resistant than PE (see Markovnikov rule). [11] Most commercial polypropylene is isotactic and has an intermediate level of crystallinity between that of low-density polyethylene (LDPE) and high-density polyethylene (HDPE). Isotactic & atactic polypropylene is soluble in p-xylene at
[1] [2] Simply put, even in the absence of air, polymers will begin to degrade if heated high enough. It is distinct from thermal-oxidation, which can usually take place at less elevated temperatures. [3] The onset of thermal degradation dictates the maximum temperature at which a polymer can be used.
The flow stress now increases significantly following neck propagation. Mechanical anisotropy increases and the elastic modulus varies along different directions, with a high modulus observed in the draw direction. Drawn semi-crystalline polymers are the strongest polymeric materials due to the stress-induced ordering of the molecular chains. [27]
In liquid water at high temperatures, (e.g. that approaching the critical temperature), the solubility of ionic solutes tends to decrease due to the change of properties and structure of liquid water; the lower dielectric constant results in a less polar solvent and in a change of hydration energy affecting the ΔG of the dissolution reaction.
Polyetherimide (PEI), produced by a novel nitro displacement reaction involving bisphenol A, 4, 4’-methylenedianiline and 3-nitrophthalic anhydride, has high heat distortion temperature, tensile strength and modulus. They are generally used in high performance electrical and electronic parts, microwave appliances, and under-the-hood ...
Most solutes remain in the liquid phase and do not enter the gas phase, except at very high temperatures. In terms of vapor pressure, a liquid boils when its vapor pressure equals the surrounding pressure. A nonvolatile solute lowers the solvent’s vapor pressure, meaning a higher temperature is needed for the vapor pressure to equalize the ...
Temperature-responsive polymers or thermoresponsive polymers are polymers that exhibit drastic and discontinuous changes in their physical properties with temperature. [1] The term is commonly used when the property concerned is solubility in a given solvent , but it may also be used when other properties are affected.
Polypropylene carbonate is soluble in polar solvents like lower ketones, ethyl acetate, dichloromethane and chlorinated hydrocarbons and insoluble in solvents like alcohols, water, and aliphatic hydrocarbons. It also forms stable emulsions in water. PPC allows the diffusion of gases like oxygen through it.