Bakelite is a phenolic resin. PF (phenolic resin) is the earliest industrialized plastic variety, in the United States in 1910 was the first to achieve industrial production.
The raw materials for PF production are mainly phenols and aldehydes, and the most commonly used are phenol and formaldehyde, which can be obtained by polycondensation reaction under the catalysis of acid and alkali catalysts. There are mainly dry and wet methods for industrial production.
Under the action of different catalysts, two kinds of PF can be formed: one is thermoplastic PF, the other is thermosetting PF. The former needs to add a curing agent and under the condition of heating to solidify into a body structure, the latter does not need curing agent, as long as heating can become a body structure.
For either thermoplastic PF or thermosetting PF, only a switching network that is solidified to form a body can be used. The curing process is the continuation of the body polycondensation reaction, and the formation of the final body product process, this process is different from the melting and curing of general thermoplastics, it is irreversible, both physical process and chemical process.
PF can be used and thermoplastic injection molding similar to the method, for injection molding PF requirements have good fluidity, can be molded under low injection pressure, high thermal rigidity and fast hardening speed, plastic surface has good gloss, easy to release, do not contaminate the mold, etc. However, injection molding also has its shortcomings, such as the melt is limited by the type of filler, not suitable for the molding of more embedded plastic parts, a large number of solidified gate, runner can not be recycled, can only be abandoned.
In simple terms, thermoplastic PF can be produced with ordinary injection molding machines, but strict care must be taken to control process conditions. The thermosetting PF must be produced by special PF injection molding machine (the barrel and screw are different from ordinary injection molding machine), and the mold must be specially designed!