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In one copolymer, the monomers can be almost perfectly alternating. [1] but (random) copolymerisation with less than 50% maleic anhydride content is also possible. [2] The polymer is formed by a radical polymerization, using an organic peroxide as the initiator. The main characteristics of SMA copolymer are its transparent appearance, high heat ...
SAN is similar in use to polystyrene.Like polystyrene itself, it is transparent and brittle. The copolymer has a glass transition temperature greater than 100 °C owing to the acrylonitrile units in the chain, thus making the material resistant to boiling water.
The ability of the system to be readily deformed above its glass transition temperature allows polystyrene (and thermoplastic polymers in general) to be readily softened and molded upon heating. Extruded polystyrene is about as strong as an unalloyed aluminium but much more flexible and much less dense (1.05 g/cm 3 for polystyrene vs. 2.70 g/cm ...
Copolymerization is particularly useful in tuning the glass transition temperature, which is important in the operating conditions of polymers; it is assumed that each monomer occupies the same amount of free volume whether it is in a copolymer or homopolymer, so the glass transition temperature (T g) falls between the values for each ...
Diverse methods are employed to manipulate the initiation, propagation, and termination rates during chain polymerization. A related issue is temperature control, also called heat management, during these reactions, which are often highly exothermic. For example, for the polymerization of ethylene, 93.6 kJ of energy are released per mole of ...
As a liquid or a gas, pure styrene will polymerise spontaneously to polystyrene, without the need of external initiators. [29] This is known as autopolymerisation. At 100 °C it will autopolymerise at a rate of ~2% per hour, and more rapidly than this at higher temperatures. [22]
The lower critical solution temperature (LCST) or lower consolute temperature is the critical temperature below which the components of a mixture are miscible in all proportions. [ 1 ] [ 2 ] The word lower indicates that the LCST is a lower bound to a temperature interval of partial miscibility, or miscibility for certain compositions only.
For the copolymerization of a given pair of monomers, the two experimental reactivity ratios r 1 and r 2 permit the evaluation of (Q 1 /Q 2) and (e 1 – e 2). Values for each monomer can then be assigned relative to a reference monomer, usually chosen as styrene with the arbitrary values Q = 1.0 and e = –0.8. [28]