Liquid rubber is named for its liquid state. The earliest liquid rubber in history appeared in 1923, which was obtained by the degumming of natural rubber. This practice consumes a lot of energy and is not practical. By 1943, there was a real, synthetically prepared liquid rubber, namely polysulfide rubber. Soon after, liquid polyurethane (PU) liquid silicone rubber, liquid butadiene rubber, liquid neoprene, etc., as well as non-functional liquid polybutadiene and reactive groups (such as alkenyl groups) at both ends were introduced. Telechelic diolefin liquid rubbers having a molecular weight of only a few thousand. The larger the molecular weight, the greater the viscosity.
(1) Synthesis method
The synthesis method of the liquid rubber includes a radical polymerization method, an ion polymerization method, and the like.
1 free radical polymerization
It is suitable for the preparation of telechelic liquid polymer, and it is necessary to select a compound having a functional group or a functional group as an initiator or a chain transfer agent to initiate polymerization of a diene monomer. When the coupling is terminated, the telechelic polymer is obtained.
2 ionic polymerization method early
This method is used for the telechelic diene liquid rubber, and the initiator used is an alkali metal naphthalene sodium complex or an organolithium compound.
3 other methods
Using conventional catalytic polymerization, liquid polybutadiene having a 1,4 structure greater than 70% can be obtained. The catalytic system used was a trialkyllithium.
Different properties can be introduced by the reaction of the monomeric double bonds. For example, by addition of hydrogen, aging resistance and heat resistance can be improved. For example, by chlorination, flame retardancy and adhesion can be improved.
Refers to the process of conversion from liquid to solid. For example, the telechelic liquid rubber is cured by a functional group of a curing agent. Carboxy
The curing agent of the liquid rubber is epoxy resin, tertiary amine, etc. • The curing agent of the liquid rubber containing the diameter is polyisocyanate, such as TDI, MDIPAPl and the like.
The processing equipment is relatively simple, low in energy consumption, easy to mechanize and continuous, and can be solidified on site. The processing step comprises three steps: the first step, mixing, that is, the first mixing of the liquid rubber together with the auxiliary agent (filler, chain extender), followed by defoaming, and then adding the additive; the second step, performing the second mixing, Adding a curing agent, and then performing a second defoaming; in the third step, molding is performed by any of different methods (injection molding, RIM molding, extrusion molding, compression molding, and rotational molding). Vulcanization processing.
(5) Application of liquid rubber
1 As a rocket solid fuel propellant, adhesive.
Generally, the telechelic liquid rubber and the diisofluoride are first reacted to obtain a prepolymer which is then cured with a low molecular weight diol. Can be used in the manufacture of cast tires.
3 Adhesives and coatings can be used as solvent-free adhesives due to their excellent adhesion. Their strength can reach 17~24MPao. If used for NR/EPDM, the peel strength can reach 22.2kg∕25mmo.
2 Preparation of multi-component blends
For example, telechelic liquid rubber can be made into an interpenetrating network polymer (IPN).