In order to make the plastic have good weather resistance, an appropriate amount of anti-aging masterbatch or antioxidant is added to the plastic. After testing, the test piece is irradiated by xenon lamp ultraviolet rays for 1000 hours, which is equivalent to one year, and the impact strength and tensile strength are maintained. The rate is 88% and 86% respectively. Xenon lamp ultraviolet radiation is 3000h, which is equivalent to three years. The retention rate of impact strength and tensile strength is 74% and 71% respectively. The excellent aging resistance makes the plastic use cycle. long, reducing the pollution of waste plastics to the environment.
Toughening agent used in PP modification
Polypropylene is one of the five general-purpose plastics, but its shortcomings such as large molding shrinkage and easy warpage limit its application in structural materials and engineering plastics. The system is toughened and modified, and calcium carbonate is added at the same time. While reducing the cost, the composite material can obtain various average mechanical properties, which expands the application space of polypropylene.
1. Activation of calcium carbonate
Toughening agent manufacturers have found that with the rapid development of the composite material industry, calcium carbonate is not only a filler, but also an important modifier. In the polypropylene blending modification system, the addition of calcium carbonate can reduce the molding shrinkage rate and raw material cost of the product, and improve the rigidity and heat resistance of the modified polypropylene product. However, calcium carbonate is an inorganic filler, which is incompatible with polypropylene. It has poor compatibility, so it needs to be activated before use to improve the binding force between calcium carbonate and polymer molecular chains, and improve the mechanical properties of filled polypropylene materials. After drying, put it into a high-speed agitator, then add an appropriate amount of phosphate coupling agent, stir at a high speed for 15-20 minutes, activate the calcium carbonate or directly use the active heavy calcium carbonate above 1000 mesh.
In the blending system, as the content of activated calcium carbonate increases, the impact strength of the system increases rapidly at first, then increases slowly after 30 phr, and decreases after 40 phr. Calcium carbonate activated with a coupling agent can make the material impact. The strength increases, because the physical and chemical structure and properties of the activated calcium carbonate particle surface have changed, and it is easier to disperse in the matrix. When the content of calcium carbonate exceeds a certain level, inorganic particles will aggregate and accumulate. The structure of calcium carbonate builds up internal defects, resulting in the decline of various mechanical properties. Therefore, the amount of calcium carbonate should not exceed 40 parts.
2. The influence of toughening agent on the blending system
Toughening agents are used in PP to give it both excellent toughness and good processability. (2) There are no unsaturated double bonds in the molecular structure of the toughening agent, and it has excellent aging resistance. (3) The toughening agent has a narrow molecular weight distribution, good fluidity and good compatibility with polyolefins. (4) Good fluidity can improve the dispersion effect of fillers, and can also improve the weld line strength of products.
With the increase of toughening agent content, the impact strength and elongation at break of the system are greatly improved. It can be seen that the toughening agent has excellent toughening effect on PP, and has good compatibility with PP and activated calcium carbonate. This is because the molecular weight distribution of the toughening agent is narrow, and the side octyl group in the molecular structure is longer than the side ethyl group, which can form a connection point in the molecular structure, and play a role of connection and buffering between the components, so that the system can act as a shock when it is impacted. The function of dispersing and buffering the impact energy reduces the time for the craze to develop into cracks due to the force, thereby improving the impact strength of the system.
When the system is under tension, since the network structure formed by these connecting points can deform greatly, the elongation at break of the system increases significantly. When the content of the toughening agent increases, the tensile strength of the system increases. , flexural strength and flexural modulus have decreased, which is determined by the performance of the toughening agent itself, so the content of the toughening agent should be controlled below 20%.