company news about Why PVC profiles become brittle

Why do PVC profiles become brittle? The brittleness of PVC profiles mainly refers to the cracking and cold impact cracking of products during cutting. There are many reasons for the brittleness and poor mechanical properties of PVC profiles. PVC profile manufacturers generally need to analyze from the following aspects.
Unreasonable formula and mixing process:
1. Excessive filling:
Some manufacturers add calcium carbonate to 20-50 parts by mass in order to reduce costs, which greatly reduces the physical and mechanical properties of the profiles, resulting in the brittle phenomenon of the profiles mentioned in this chapter.
2. Types and quantities of impact modifiers added:
ACR has an impact strength that is about 30% higher than CPE. Therefore, PVC/ACR blend system should be used as much as possible in the formula, and when modified with CPE and the dosage is lower than the mass fraction, it often causes the profile to become brittle.
3. Too much or too little stabilizer:
Excessive use of stabilizers can delay the plasticization time of the material, resulting in insufficient plasticization when the material is exported from the mold. The molecules in the formula system are not completely dissolved, and the intermolecular structure is not firm, resulting in insufficient plasticization. When the dosage is too low, it can cause the degradation or decomposition of relatively low molecular weight substances in the formula system (also known as over plasticization), which can damage the stability of the intermolecular structure of each component. Therefore, the amount of stabilizer used can also have an impact on the impact strength of the profile, and too much or too little can cause a decrease in the strength of the profile and cause it to become brittle.
4. Excessive amount of external lubricant:
External lubricants can be divided into pre lubrication and post lubrication. Materials with excessive lubrication exhibit poor appearance under various conditions. If the lubricant dosage is not appropriate, it may cause flow marks, low yield, turbidity, poor impact, rough surface, adhesion, and poor plasticization. Especially when the dosage is too high, it can cause poor compactness and plasticization of the profile, leading to poor impact performance and causing the profile to become brittle.
5. The order of hot mixing, temperature setting, and curing time also have decisive factors on the performance of profiles: there are many components in the PVC-U formula, and the selected feeding order should be conducive to exerting the effect of each additive and improving the dispersion speed, while avoiding its adverse synergistic effect. The feeding order of additives should help improve the complementary effect of additives. Failure to strengthen the control of the mixing process will have an impact on the quality of profile products, and in some cases, the profile will become brittle.