What causes brittle plastic profiles?

Plastic profiles are subject to physical constraints. The brittleness of plastic materials occurs in the production process. One of the main reasons is that the brittleness of plastic materials is caused by unreasonable plastic formulation and mixing process. There are five reasons for the unreasonable formulation and mixing process.

Thermal mixing feeding sequence, temperature setting value and ripening time: There are many components in PVC-U formula. The feeding sequence of additives should help to improve the complementary effect of additives, overcome the effect of mutual elimination, and make the additives dispersed in PVC resin fully enter the interior of PVC resin.

Generally, when the heat mixing temperature is around 120 degrees, when the temperature is too low, the material can not reach the gelation and even mixing. When the temperature is too high, some materials may decompose and volatilize, and the dry mixed powder is yellow.

Too many or too few stabilizers: The role of stabilizers is to inhibit degradation, or react with released hydrogen chloride, and to prevent the discoloration of polyvinyl chloride during processing. The excessive amount of stabilizer will delay the plasticizing time of the material, so that the material is still under-plasticized when it is exported to the die, and the molecules in the formulation system do not fully dissolve.

When the dosage is too small, the relatively low molecular weight substances in the formulation system will be degraded or decomposed, which will destroy the stability of the intermolecular structure of each component. Therefore, too much or too little stabilizer will result in the reduction of profile strength and brittle profile.

Too many fillers: With the development of technology, most of them use ultra-fine light activated calcium carbonate, even nano-sized calcium carbonate, which not only increases rigidity and filling, but also has the effect of modification, but its filling amount is not unlimited, and its proportion should be controlled.

At present, some manufacturers add calcium carbonate to 20-50 parts in order to reduce costs, which greatly reduces the physical and mechanical properties of profiles, resulting in the brittle phenomenon of profiles mentioned in this chapter.

Quantity of impact modifier: impact modifier is a kind of macromolecule polymer which can increase the total energy of rupture of polyvinyl chloride under stress. At present, the main varieties of impact modifiers for rigid polyvinyl chloride are CPE, ABS and so on. When they are blended with PVC, the impact resistance, processability, weatherability and fillet strength of rigid polyvinyl chloride can be effectively improved.

Excessive amount of external lubricant: the low compatibility between external lubricant and resin can promote the sliding of resin particles, thereby reducing friction heat and delaying melting process. This effect of lubricant is the greatest in the early processing. If the amount of lubricant is not appropriate, it may cause flow marks, low output, turbidity, poor impact, rough surface, adhesion, poor plasticization and so on, resulting in brittle profile.

Therefore, the preparatory work for the production of plastic profiles must be done well in the early stage, the proportion and use of materials should be paid attention to, and the technological process should be produced strictly in accordance with the requirements of the regulations, so as to ensure the production of qualified plastic profiles.