Polypropylene is one of the five general-purpose plastics, but its shortcomings such as large molding shrinkage and easy warpage deformation limit its application in structural materials and engineering plastics. Calcium carbonate is non-toxic, odorless, non-irritating and rich in resources. It is an excellent inorganic filler for polymer materials. It can improve the hardness, elastic modulus and dimensional stability of polypropylene. At the same time, it is toughened by POE. Agent, HDPE synergistic toughening, filling and modifying the system, while reducing the cost, the composite material to obtain a balanced mechanical properties, expanding the application space of polypropylene.
1. Activation of calcium carbonate
With the rapid development of the composites 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 and has poor compatibility with polypropylene. Therefore, it needs to be activated before use to improve the bonding strength between calcium carbonate and polymer molecular chains, and improve the mechanical properties of filled polypropylene materials. The heavy calcium carbonate of 800 mesh or more is used, dried, and then put into a high speed mixer, and then an appropriate amount of a phosphate ester coupling agent is added, and the mixture is stirred at a high speed for 15-20 minutes to activate the calcium carbonate. Or directly use 800 cm or more of active heavy calcium carbonate.
With the increase of activated calcium carbonate content in the blend system, the impact strength of the system increased rapidly first, and the increase was slow after 30 parts, and the impact strength decreased after 40 parts. The calcium carbonate activated by the coupling agent can increase the impact strength of the material because the surface of the activated calcium carbonate particles undergoes a change in physicochemical structure and properties, and is more easily dispersed in the matrix. When the content of calcium carbonate exceeds a certain level, the accumulation and accumulation of inorganic particles may occur, causing internal defects of the structure of the blend system, resulting in a decrease in various mechanical properties. Therefore, the amount of calcium carbonate is preferably not more than 40 parts.
2. Effect of POE on blending system
POE is a thermoplastic elastomer which realizes in-situ polymerization of ethylene and octene using a metallocene catalyst, and is characterized in that: (1) the soft chain-wound structure of octene and the crystalline ethylene chain act as physical crosslinking points, making it excellent. The toughness and good processability. (2) There is no unsaturated double bond in the molecular structure of POE, and it has excellent aging resistance. (3) POE has a narrow molecular weight distribution, good fluidity, and good compatibility with polyolefins. (4) Good fluidity can improve the dispersion effect of the filler and also increase the weld line strength of the product.
As the POE content increases, the impact strength and elongation at break of the system are greatly improved. It can be seen that POE has excellent toughening effect on PP and has good compatibility with PP and activated calcium carbonate. This is because the molecular weight distribution of POE is narrow, and the side octyl group in the molecular structure is longer than the side ethyl group, and a linkage point can be formed in the molecular structure, which acts as a linkage and buffer between the components, so that the system is dispersed when subjected to an impact. The effect of cushioning impact energy reduces the chance that the silver streaks develop into cracks due to the force, thereby increasing the impact strength of the system. When the system is subjected to tension, the network-like structure formed by these joints can undergo large deformation, so the elongation at break of the system increases remarkably. When the content of POE increases, the tensile strength and bending of the system Both the strength and the flexural modulus are reduced, which is determined by the performance of the POE itself, so the POE content should be controlled below 20%.
The relationship between the content of POE and the melt index, after the addition of POE, the melt index of the system increases. POE itself has better fluidity. Its addition also improves the fluidity of the whole system. When the POE content exceeds 15 parts, the melt index of the system is basically unchanged. If the liquidity of the system is to be continuously improved, it cannot be completely Rely on POE.
3. Effect of HDPE on mechanical properties of the system
The addition of an appropriate amount of other polymer throughout the system also improves the mechanical properties of the system while reducing costs. With the addition of proper amount of HDPE, the impact strength is improved to some extent. POE is a copolymer of ethylene and octene. Therefore, HDPE acts as a 'crosslinking agent' between polypropylene and POE, which improves polypropylene better. Compatibility with POE, thereby improving the ability of the system to resist external impact.
When the HDPE is added into the system, the impact strength is increased and the tensile strength is increased little. When the HDPE is 10 parts, the impact strength is rapidly increased, and the increase is slow at 15 parts. Therefore, the amount of HDPE should be about 10.
4, aging performance
In order to make the material have good weather resistance, an appropriate amount of anti-aging masterbatch or antioxidant is added to the system. After testing, the test piece is irradiated with xenon lamp for 1000 hours, which is equivalent to one year, and the impact strength and tensile strength are maintained. The rates are 88% and 86%, respectively. Xenon lamp ultraviolet radiation 3000h, equivalent to three years, the impact strength and tensile strength retention rate are 74% and 71%, respectively, excellent aging resistance, making the material a long life cycle, reducing the environmental impact of waste plastics Pollution.
Disposable Urine Bag,Disposable Catheter Bags,Pediatric Urine Collection Bag,Disposable Incontinence Urine Bag
Henan Diyi Medical Technology Development Co.,Ltd. , https://www.diyimedical.com