Application and Quality Control of Adhesives on Composite Films (3)

The reaction consumes the curing agent, which reduces the amount of curing agent involved in the reaction with the glue, and at the same time releases CO2, so that the glue layer contains bubbles, which is extremely unfavorable to dry compounding, and often results in surface quality problems affecting the adhesive strength. Similarly, the active hydrogen of isocyanate groups and alcohols, polyols, and other hydroxyl-containing compounds that react to form carbamates and react with organic acids (hydroxyl groups) to form acylate wrists will affect the normal use of the glue. Therefore, dilution must be performed during compounding. Agent for testing.

There must be a clarification here. Some composite manufacturers believe that adding more diluent can reduce the cost, and this view is wrong. Diluent in the compounding process only plays a role in uniform coating and facilitates infiltration. The real adhesive effect is glue and curing agent. , And the diluent has evaporated, as long as a certain amount of dry glue is applied, less diluent is more economical.

5. Influence of other artificial and mechanical factors on composite quality

(1) Human factors: Human factors refer to the composite quality problems caused by human factors in the compounding process, such as errors in rubber compounding, improper control of pressure and temperature, and so on. The following are separately explained.

1 With rubber: The correct operation of the glue is to add the appropriate amount of diluent to the main agent, and stir evenly, and then add the curing agent and stir evenly. Instead of mixing the main agent and curing agent together, add a thinner. This is determined by the nature of the chemical reaction. The speed of the chemical reaction depends on the effective collision between the molecules. At the same temperature and pressure (such as at room temperature and pressure), the effective collision between molecules is related to its concentration. The higher the concentration, the effective collision. The greater the chance, the faster the reaction.

The main agent and curing agent in the absence of diluent conditions, high concentration, fast reaction, rapid melons generate larger molecules and condense into clumps. After adding the diluent, the speed becomes slower. In this way, in the compounding process, the glue coated on the film has extremely uneven molecular weight, which easily causes surface quality problems and also affects the adhesive strength of the adhesive.

2 Inappropriate control: For different composite materials, different adhesives, the required pressure temperature and other requirements are not the same, so you must change the pressure and temperature conditions according to the actual production. For example, the higher the solid content of the glue, the smaller the molecular weight and the relatively lower initial tack force. In order to achieve a higher initial tack, the temperature and pressure should be increased. Another example is that one-component adhesives are mostly self-adhesive. Increasing the temperature and pressure will greatly increase their adhesive strength. For some films, too high a temperature will cause it to curl, deform, and naturally not be too high.

(2) Mechanical factors: Mechanical factors refer to the composite quality problems caused by mechanical reasons in the compounding process. In general, when the compound film shows regular traces, it is mostly caused by the cause of the printing machine or the compound machine. These regular traces can be eliminated by mechanical inspection and replacement of parts. The factors that affect composite quality are mainly the above five factors. Attention must be paid to these aspects in the production process to avoid problems. (Finish)