How to improve the heat and cold resistance of rubber?

How to improve the heat and cold resistance of rubber, that is, expand the range of its use temperature: when the temperature is higher than a certain temperature, the rubber loses its elasticity due to aging; At temperatures below a certain temperature, rubber loses its elasticity due to vitrification.
1、 Improve high-temperature aging resistance and heat resistance
1. Changing the main chain structure of rubber
(1) The main chain does not contain double bonds.
(2) Butyl rubber (isobutylene and isoprene) with less double bonds in the main chain.
(3) Polysulfide rubber containing S atoms in the main chain.
(4) Polyether rubber containing O atoms in the main chain.
(5) Dimethyl silicone rubber with non carbon atoms on the main chain.
2. Changing the substituent structure
(1) Rubber with electronic substituents is prone to oxidation: natural rubber, styrene butadiene rubber.
(2) Rubber with electron absorbing substituents is not easily oxidized: neoprene, fluororubber.
3. Changing the structure of cross-linked chains: Principle: cross-linked chains with less sulfur have larger bond energy and good heat resistance. If the cross-linked bond is C-C or C-O, the bond energy is larger and the heat resistance is better. (The vulcanization crosslinking bond of ZnO for chloroprene rubber is - C-O-C -, and the crosslinking bond of natural rubber is - C-C - using peroxide or radiation crosslinking.).
2、 Reduce glass transition temperature and improve cold resistance
Any measure to increase the activity of molecular chains and weaken intermolecular interactions will reduce the glass transition temperature. Any measure to reduce the crystallization ability and speed of polymers will increase the elasticity of polymers and improve cold resistance (because crystallization is the regular arrangement of polymer chains or segments, it will greatly increase intermolecular interactions, resulting in increased strength and decreased elasticity of polymers).
1. Adding plasticizers: weakening intermolecular forces
For example, chloroprene rubber Tg-45 ℃, adding dibutyl succinate Tg (- 80 ℃) can make its Tg-62 ℃;
For example, using trimethylphenol phosphate (- 64 ℃) can make it Tg-57 ℃.
It can be seen that the plasticizer effect is not only related to the structure of the plasticizer, but also to its own Tg. The lower the plasticizer, the lower the plasticizer of the polymer.
2. Copolymerization: Polystyrene has a large side group, so it is difficult to rotate in the main chain and is relatively rigid, with Tg higher than room temperature. However, the copolymerized styrene-butadiene rubber is - 53 ℃, and polyacrylonitrile has a polarity, so it is difficult to rotate in the main chain and is relatively rigid, with Tg higher than room temperature. The copolymerized styrene-butadiene rubber with acrylonitrile is - 42 ℃.
3. Reducing the crystallinity of polymers: Linear polyethylene has a very flexible molecular chain with low Tg, but due to its high degree of regularity, it is difficult to crystallize polyethylene as a rubber. A small volume of nonpolar substituents methyl are introduced to disrupt the regularity of its polyethylene molecular chain, thereby damaging its crystallinity. This is ethylene propylene copolymer rubber Tg=- 60 ℃. By disrupting the regularity of the chain, the crystallization ability of the polymer is reduced, improving elasticity but having a side effect that is detrimental to strength.