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What factors affect the flame retardant effect of extruded board?

Views: 0     Author: Site Editor     Publish Time: 2020-09-09      Origin: Site

What factors affect the flame retardant effect of extruded board?

The common problem of most extruded board manufacturers is that the flame retardant effect of the flame retardant is not obvious, the thermal stability of the flame retardant is poor, and the flame retardancy is uneven. On the same board, some places have obvious flame retardancy. , In some places, the flame retardant effect is very poor or even not flame retardant; the same flame retardant, the flame retardant effect of the board produced by one machine is very good, but the flame retardant effect of the other machine is very poor; the same machine, different The flame retardant performance varies greatly among manufacturers. There are three main reasons for these problems:

Human factors: The amount of flame retardant added in the extruded board is very small, generally less than 10%. To make the flame retardant evenly distributed in the material, stirring is the key part, and it is necessary to make every 100 grams of material It evenly contains about 5 grams of flame retardant. It is conceivable that a large amount of manual stirring or a special mixer is required for mixing. Most manufacturers directly sprinkle the flame retardant on the surface of the material and send it to the feeder, although the feeder is self-contained With stirring, it can only form a small area in a short time and it is difficult to uniformly mix, resulting in regional flame retardancy. The unqualified items are mainly reflected in the oxygen index test required by GB 8624.

Production process factors: different equipment manufacturers have different designs for the internal structure of the equipment, resulting in different plasticization, dispersion, and residence time of the materials inside the equipment. Conventional flame retardants are mainly hexabromocyclododecane, which has a low decomposition temperature, which is inconsistent with the processing temperature of ordinary extruded boards. The ordinary heat temperature is sufficient to decompose most flame retardants. Therefore, we usually use the melt temperature as the standard of the flame-retardant board instead of the heating temperature. Actual production proves that the manufacturer can produce the best extruded board quality and resistance by adjusting the maximum melt temperature between 175-190 degrees Celsius depending on the equipment. This process temperature is contrary to the process temperature provided by most equipment manufacturers, mainly because the production process of the equipment refers to the melting temperature of the newly manufactured polystyrene particles. In actual production, most of the extruded panels are It is produced with recycled PS particles, and the melting temperature of the recycled PS particles and the new material differs by 20-30 degrees Celsius. Therefore, the shear heat of the equipment to the material will accumulate higher and higher. If the heating temperature and cooling water in the long-term production process are not adjusted, the flame-retardant components will decompose and fail. The unqualified items are mainly reflected in the monomer test parameters. .

Flame retardant factors: There are three types of flame retardants according to their appearance: powder, granule and masterbatch. The masterbatch is made of flame retardant plus plastic carrier and dispersant after being heated by the extruder to make pellets. The flame retardant component will account for 40%-50%. The masterbatch has good dispersibility and is hygienic and dust-free. The disadvantage is The use cost is high, and flame retardant will inevitably have a little loss after one processing. Powdered flame retardant has the earliest use time and is the most widely used. It has good economy and good flame retardant effect. The disadvantage is that it is different in specific gravity from plastic particles and is easy to delamination. The granular flame retardant is a powdered flame retardant that is extruded into granules by dry method. No impurities are added. There is no material decomposition loss without thermal processing. Its composition is the same as the powder and the amount is the same. The specific gravity of the particle is the same as that of PS. The pellets are close, which solves the problem of uneven dispersion of powdered products, and is now widely used.


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