Rotomolding is a thermal process of unstable state. The bubble is a part of the essence of rolling.Powder, granule and liquid system
It's going to happen.In powders and granules, when dissolved together, the air is trapped between the powder and the particles.In the liquid system,
Bubbles can be formed by mixing and flowing turbulence.In the case of the foaming cross section, the bubble would be a favorable point;But for the most part
Products, bubbles can cause fatal defects in physical properties, so many efforts are being made to reduce the bubble phenomenon as much as possible.
Phase 1: in the early stage of the forming cycle, the powder particles dissolve together in the inner surface of the mold and trap the air inside.small The powder particles tend to stick to the die first
It has a surface that traps smaller bubbles.On the die surface.When the powder particles are carried out.The continuity of the mantle is also truncated.A bubble of continuity.
Phase 2:2: when the polymer melts, it is trapped.The air between the particles will be in the cross section of the product.The surface is formed of ungage air bags.
Phase 3:3: Continuous heating reduces the clustering.The viscosity of the compound due to the surface tension to compress the airspace into a minimum area,and let the irregular air bags become balls.More than 150 ℃ (PE), in accordance with the material,the solution property, the bubble will start pretty fast the disappearance.
Stage 4: at this stage, the gas inside the bubble will disappear into the surrounding polymer.If oxygen is going to react with the polymer, at the same time
Other gases will dissolve or move.Finally, all the bubbles will disappear into the polymer and leave the area without the bubble
Depending on the rheological properties of the material and the length of the heating cycle.
The surface porosity is the natural characteristic of rolling products.When airspace is formed on the surface of the product, buoyancy, capillary phenomena or fluid
The force exerted on the bubble does not overcome the surface tension (in the PE material, the buoyant buoyancy of the bubbles is not enough to make the bubbles
Free float to the surface.Instead, when the surface of the metal is applied to the surface of the polymer, it helps to remove the bubbles.in
In some materials, the pores can't be removed, while the air space still exists in the same way
The surface of the wet metal mold is determined by the surface energy.The surface tension value of polyolefin is the range of
20~50 dynes/cm, the metal is higher than the surface tension of the melting material, so the polymer will adhere to and moisten its surface.if
The surface of the mold is less energy than the liquid polymer, so the material will not wet its surface.
The mold release agent can significantly reduce the surface energy of the mold, thus reducing the force that attracts the material to the mold.If you don't use
Remove the touch agent, the surface porosity will decrease;Removing material from the surface, however, will be more difficult.The use of a remover can produce high density
The stomata of the surface.Naked metal (i.e., no ejection agent) is reduced on the surface of the surface, which is not as predicted by the theory, because
The oxide layer forms on the metal surface and reduces the surface energy/tension.Test all kinds of generic deformable agents to show all types
A similar surface porosity is produced.