The reason why plastic profiles are brittle is basically reflected in the physical and mechanical properties of plastic products. The main features are: breakage during blanking, cold punch rupture and so on. There are many reasons for the poor physical and mechanical properties of profile products, mainly including unreasonable formula and mixing process, unreasonable extrusion process, unreasonable mold design, and cracking in the incision.
一: The formula and mixing process are unreasonable
1. Too much filler
In view of the current low profile prices on the market and the rising prices of raw materials, profile manufacturers are making a fuss about reducing costs. Formal profile manufacturers reduce costs without reducing quality by optimizing the combination of formulas. Some manufacturers have lowered the quality of their products while reducing costs.
2. Type and quantity of impact modifier added
Impact modifier is a high molecular polymer that can increase the total energy of PVC rupture under stress. At present, the main varieties of impact modifiers for rigid PVC are CPE, ACR, MBS, ABS, EVA, etc. The molecular structure of CPE, EVA, ACR modifiers does not contain double bonds, and has good weather resistance and suitable As outdoor building materials, they are blended with PVC, which can effectively improve the impact resistance, processability, and weather resistance of rigid PVC, and increase the strength of the solder fillet within a certain range.
3. Too much or too little stabilizer: The role of stabilizer is to inhibit degradation, or react with released hydrogen chloride and prevent discoloration during processing of PVC.
The amount of stabilizer varies according to the type, but in general, too much dosage will delay the plasticization time of the material, so that the material is not plasticized when it is exported to the mold, and the molecules in the formula system are not completely fused. The intermolecular structure is not strong. If the dosage is too small, it will cause degradation or decomposition of the relatively low-molecular substances in the formula system (also can be said to be over-plasticized), which will damage the stability of the intermolecular structure of each component. Therefore, the amount of stabilizer will also affect the impact strength of the profile, too much or too little will cause the profile to decrease in strength and cause the profile to become brittle.
4. Excessive amount of external lubricant
The external lubricant has low compatibility with the resin, which can promote the sliding between the resin particles, thereby reducing the frictional heat and delaying the melting process. Before the resin is completely melted and the resin in the melt loses its identifying characteristics) is large.
External lubricants are divided into pre-lubrication and post-lubrication. Materials that are over-lubricated have poor appearance under various conditions. If the amount of lubricant is not appropriate, it may cause flow marks, low output, turbidity, poor impact, and rough surface. , Adhesion, poor plasticization, etc. Especially when the amount is too much, it will cause poor compactness and poor plasticization of the profile, resulting in poor impact performance and brittleness of the profile.
5. The order of hot mixing, temperature setting and curing time are also decisive factors for the performance of the profile