Bakelite Injection Molding Machine Process

Bakelite was one of the first industrialized plastics, having been produced industrially in the United States in 1910. It can be injection molded in a similar way to thermoplastics and requires special Bakelite injection molding machines or strict process conditions. As a top bakelite injection molding machine manufacturer in China, we would like to introduce the bakelite injection molding machine process.

What is Bakelite?

Bakelite is a phenolic resin. It is the earliest industrialized plastic species, and was the first to be industrially produced in the United States in 1910. Phenol and aldehyde in the role of different catalysts, can produce two kinds of PF: - one is a thermoplastic PF, the other is a thermosetting PF, the former to add a curing agent and in the case of heating to cure into a body structure, the latter does not need a curing agent, as long as the heating can become a body structure. The plasticizing temperature of Bakelite powder is 70～90℃, and the best curing temperature is about 160℃. Bakelite is suddenly cured when the temperature reaches 160℃, so the precise control of mold temperature is very crucial for shaping. Bakelite uses: electrical switches, knobs, kitchenware handles, electrical enclosures, this year in the electrical parts, automotive parts, crafts are increasingly widely used.

Whether it is thermoplastic PF or thermosetting PF, it can only be used by curing to form a body exchange network. This process is different from the melting and curing of thermoplastics in general, it is irreversible and has both physical and chemical processes. Therefore, it cannot be recycled after production.

PF can be injection molded in a similar way to thermoplastics. PF for injection molding requires good fluidity, the ability to mold at low injection pressure, high thermal rigidity and fast hardening speed, good gloss on the surface of the molded part, easy release, and no contamination of the mold. However, injection molding also has its shortcomings, such as the melt is limited by the type of filler, not suitable for molding plastic parts with more inserts, a large number of gates and runners after curing can not be recycled, can only be discarded, etc.

Bakelite injection molding machine process

1. Plasticizing conditions: back pressure, screw speed, material temperature
2. Injection molding process because the bakelite curing process is accompanied by water vapor and chemical gas generation, the mold should be opened exhaust grooves, or even increase the mold opening exhaust process.
3. The bakelite powder need not and cannot be dried before pre-molding
4. Because the bakelite powder contains 40% of the filler, injection resistance is very high, so a larger injection pressure should be applied
5. Bakelite powder in the preheated barrel species for the lowest viscosity of the melt state

1. Back pressure size

   Large back pressure, can make the melt fully plasticized, plasticized evenly, but easy to make the melt because the temperature is too high and early curing loss of fluidity, can not be injection; back pressure is small, the melt is not fully plasticized, poor fluidity of the melt, can not fill the shape. Should be based on the actual condition of the raw material and the wear condition of the screw barrel, set the appropriate back pressure.

2. Bcrew speed

   The larger the screw speed, the shorter the plasticizing time, the melt can not be fully plasticized; the smaller the screw speed, the more friction during plasticization, making the melt temperature too high and curing in advance, generating gas, affecting the filling will also cause corrosion of the screw barrel, increased wear.

3. Temperature

   Material temperature is too high, the melt in the screw shear quickly cured, so that the screw barrel wear intensified, more can not be injected, blocking the injection nozzle; material temperature is too low, the melt is not fully plasticized, slow injection, can not fill the cavity, fusion marks are obvious. In general, the material temperature should be controlled between 70 ~ 90 ℃, such as raw materials PF-161J material temperature should be in 72 ~ 78 ℃ is appropriate.

Bakelite injection mold filling conditions

1. Injection speed

   Injection speed is too fast, the greater the frictional heat generated by the melt and the mold, so that the melt is cured prematurely, or even scorched, while the water vapor and gas generated by curing can not be discharged cleanly, resulting in chalky pores or lack of glue; injection speed is too busy, easy to produce flow marks and fusion marks.

2. Injection pressure

   The injection pressure is too large, so that the molten glue is well shaped and has good mechanical properties, but it increases the internal stress of the plastic parts and makes the burrs thicker and larger (the burrs can be penetrated by daylight as appropriate); the injection pressure is too small, the products are easy to lack of glue, and the lack of glue for many times will easily lead to the blackening of the mold sticky material and make the surface of the products lose luster and white.

3. Pressure-holding time

   The longer the holding time, the greater the weight of the plastic part, the more dense the plastic part, but the holding time is too long will cause difficulties in demolding, after the holding time exceeds 25 seconds, the weight of the plastic part will no longer increase; the shorter the holding time, the shrinkage rate increases, when the holding time is too short, the production cycle becomes shorter, premature demolding will cause sticky mold and deformation.

Bakelite injection molding machine curing conditions

1. Mold temperature

   The higher the mold temperature, the shorter the molding cycle, improving production efficiency, but the mold temperature is too high, bakelite powder is easy to scorch, pinholes, but also makes the filling of the rapid curing of the melt material and it is too late to completely discharge the resulting gas and cause trapped gas, burn yellow mold, produce sticky mold, whitening and other defects; mold temperature is too low, the melt front liquidity becomes poor, can not fill the core, but also make the melt material curing combination is not tight, mechanical Poor mechanical strength, poor gloss. If the cooling time remains unchanged, it is easy to stick to the mold or produce bubbles when demoulding.

2. Cooling time

   Mold temperature is high, cooling time can be reduced under the condition of ensuring the size of plastic parts within the tolerance; the larger the wall thickness of plastic parts, the cooling time should be increased accordingly. Annealing treatment after demoulding: natural cooling

Choose the best Bakelite injection molding machine

Kebida is an excellent bakelite injection molding machine manufacturer in China. High quality injection molding machine is the core key of our production. With our high level engineers and technicians, we can provide injection molding machines of various specifications and customization. If you are interested, you can check our bakelite injection molding machine products or contact us directly to get the latest quotation.