What You Need to Know About the ''Crystal Point'' Problem of the Membrane Keyboard Industry

1. What is a membrane keyboard crystal point?

The crystal point of the membrane keyboard is actually "excessive polymer", that is, the molecular weight of the polymer at the "crystal point" site is higher than that of the surrounding same polymer. Due to the high molecular weight, the crystal point site polymer has a higher melting point. When melted, the melt has a relatively high viscosity. The polymer at the crystal point of the membrane keyboard cannot be uniformly dispersed and mixed with the surrounding polymer of the same kind during film blowing or casting, and after the melt is blown or cast into a film, it solidifies before the surrounding same polymer. Therefore, the formation of "arrow-shaped" or "spherical" superpolymer solids, which are customarily called "crystal points".

2. The reason for the crystal point of the membrane keyboard

Material reason:

(1) There is residual catalyst in the polymer.

(2) The polymer melt sticks to the metal surface of production equipment (including polymerization equipment and film blowing equipment), and remains at high temperature.

(3) The catalyst continues to catalyze the polymerization of the polymer, thus forming an excessive polymer.

The oxygen contained in the polymer will also cause the polymer melt to produce crystal points of the membrane keyboard (adding a certain amount of antioxidants can prevent the effect of oxygen on the crystal points).

Process reasons:

(1) Crystal points caused by the polymerization process. Different polymerization equipment and processes have different effects on the formation of crystal points. For example: some famous factory raw materials, due to the high production technology, the residual catalyst content in the polymer is low, and the equipment structure is good, so the raw materials themselves contain few crystal points. However, some raw materials with poor quality, due to production technology and equipment problems, cause the raw materials themselves to contain many crystal points.

(2) The crystal point caused by the process. For example: the film prepared by good molding equipment has few crystal points. The film made by poor equipment has many crystal points.

3. The method of reducing or basically eliminating the crystal point of membrane keyboard

In summary, there are two main ways to eliminate crystal points in the film blowing process:

(1) Improve the fineness of the filter screen of the processing equipment (for example: change the filter screen to 120 mesh, or even 150 mesh - for ultra-thin film).

(2) Add surface lubricants in the production process so that the polymer melt being processed cannot stick to the surface of the film blowing equipment.

In terms of production process, although the use of a finer filter screen can filter out most of the primary crystal points in the polymer, at the same time, it can also filter out the crystal points caused by the polymer sticking to the surface of the screw and the barrel of the equipment, but the problem is that the back pressure of the equipment is therefore increased, which is difficult for some old molding equipment. Therefore, by changing the filter frequently, it can also help to control the crystal point of the membrane keyboard.