In the production and development process of plastic board production equipment, due to improper formulas or unreasonable processing structure of plastic products, plastic boards are brittle, which is mainly characterized by: mouth collapse and cold punching fracture during blanking. Reasons for plastic board embrittlement: the formula and process of plastic board production are unreasonable.
1. Too much or too little stabilizer
The dosage of stabilizer varies according to the different types of plastic board products in China, but on the whole, too much dosage will delay the plasticization time of materials, so that the materials are not plasticized when passing through the export mold. There is no complete fusion between the molecular levels in the formula management system, and the inter-molecular structure is not firm. When the dosage is too small, it will easily cause the degradation or decomposition of relatively low molecules in the formulation technology system(also known as superplasticization), which will seriously damage the stability of the intermolecular structure of each group. Therefore, the amount of stabilizer will also have an impact on the development of the impact strength of plastic plates in China. Too much or too little will directly reduce the strength of profiles, resulting in brittle plastic plates.
2. Too much filler
With the decline in the price of plastic plates and the rise in the price of raw materials, many manufacturers have reduced costs and reduced the quality of plastic plate products. Due to the composition of the formula, the direct and effective method is to add fillers and calcium carbonate to the fillers commonly used in the production of PVC-U plastic plates. With the development of technology, most ultra-fine and light-activated calcium carbonate, even nano calcium carbonate, not only play the role of increasing hardness and filling, but also have the role of modification, but the filling amount is not unlimited, and the proportion should be controlled. Now,in order to reduce costs, some manufacturers have reduced the cost of calcium carbonate to 20-50 pieces, which greatly reduces the physical and mechanical properties of profiles, resulting in the brittle phenomenon of plastic plates.
3. Different types and quantities of impact modifiers are added
Impact modifier is a new kind of high molecular organic polymer, which can continuously improve the total energy of PVC cracking under the influence of stress. At present, the main product varieties of impact modifiers used in UPVC include CPE, ACR, MBS, ABS, EVA, etc. Among them, the molecular utilization structure of CPE, EVA, and ACR modifiers does not contain two double bonds and has good weather resistance. They are suitable for building engineering materials for outdoor activities. Their blending with PVC can effectively improve the impact resistance, processability, and weather resistance of UPVC and improve the fillet strength within a certain time range. Experimental research demonstrates that ACR has impact design strength requirements higher than CPE by about 30%. Therefore, in the formula, we try our best to use a PVC/ACR blend system, and when modified with CPE and the dosage is significantly lower than 8 parts by mass, some plastics and plates may be brittle.
4. Excessive amount of external lubricant materials
The solubility of external lubricant and resin is low, which can promote the sliding between resin particles, thus reducing the friction heat and delaying the melting process. External lubrication is divided into pre-lubrication, post-lubrication, and over-lubrication materials, which show poor shape under various conditions. If the amount of lubricant is improper, it may cause flow marks, low output, turbidity, poor impact, rough surface, poor adhesion, and poor plasticization. Especially when the dosage is too large, it will lead to poor density and plasticization of plastic sheets, resulting in poor impact performance and fragile plastic sheets.
