The foam molding

The forming principle of bubble, solid resin foam formation can be divided into two main steps, one is the bubble formation, the second is a bubble fixed. The formation of air bubbles in the process of injection molding processing, heat after reaching a certain temperature, the effect of physical foaming agent vaporization, and decomposition of chemical blowing agent to produce gas. If foaming agent are actually in the resin, gas are uniformly distributed within the resin, resin melt as partition separated from each other and the existence of scattered. Bubble hole fixed on thermosetting resin, as a result of crosslinking curing and foaming at the same time, the system viscosity increasing, produce gas easily fixed and form bubble hole, thus forming foam plastics.

for thermoplastic resin, after the gas formation, the system temperature continues to rise, makes a growing bubble volume, the melt viscosity with temperature rise is a sharp drop in, bubble hole between the bubble hole wall strength are also falling, leading to the formation of dispersed bubble worn out bubble wall assembled into large bubbles with each other, and it is easy to overflow the melt and the foaming failure.

crosslinked foam, foam formulation adding cross-linking agent, bubble formation in the melt, decomposition of crosslinking agent, began to melt crosslinking, thus inhibiting the melt viscosity fell sharply, increase the intensity of the bubble wall, prevent bubble hole wear out melt, bubble hole wall gathered outside or overflow melt with each other.

pressure foaming, adopt the method of pressure can prevent bubble overflow, but to prevent the accumulation of the bubbles so should choose to drink the decomposition temperature and melt viscosity, to adapt to each other, as far as possible to prevent bubbles. Then thermoplastic melt pressure, make the melt in the bubble overflow melt, fixed in the melt and the formation of porosity. Pressure foaming process for specific gases formed in the resin aerosol, uniform compression in the melt, melt cooling after the formation of injection molding products processing, remove the stress, the products of the heating in the steam cylinder, the compression of the aerosol began expanding bubble forming holes. An aerosol can form many bubble hole, and thus its small and uniform bubble hole.

the liquid and gas bubble formation principle of mixed liquid and the gas phase can be bubble content mainly depends on the nature of the liquid. When the liquid and gas bubble, liquid surface area will increase, so that the fluid - Gas system energy increase, make it become the thermodynamic instability system. As far as possible to make the above thermodynamic instability system into stable system, make the gas does not overflow liquid, need adding surface active agent to the system, in order to reduce gas The surface tension of the liquid interface, which make it become the thermodynamic stability system.

structure foam plastic molding principle and structure of the key is in the process of the melt flow of foam plastic foaming agent to decomposition temperature, began to decompose and produce bubbles, but the bubble larger pressure, the pressure is greater than bubble expansion force, while making bubbles to form, but not foaming expansion. At the same time, another key point is the structure of foam plastic molding or qualitative set of surface temperature is lower, make close to melt rapidly cooling mould, make the skin not melt foaming or low foaming and rapid cooling to finalize the design, and injection molding products processing internal foaming.

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