How to improve the transparency of PP in productio

2022-09-23
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How to improve the transparency of PP in production

transparent PP is prepared by adding nucleating agent. Nucleating agent can make polypropylene recrystallize after melting and plasticization, increase its crystallization temperature, accelerate crystallization, change the size of spherulites, and make large spherulites finer. The arrangement is regular and evenly distributed

nucleating agents include inorganic and organic. Inorganic nucleating agents mainly include talc powder, calcium carbonate, etc. when used as nucleating agents, the particle size is required to be small; Organic nucleating agents mainly include fatty carboxylic acid metal soaps, aromatic carboxylic acid metal soaps, organic phosphates and sorbitan derivatives. The nucleation mechanism of various nucleating agents is the same, but due to some differences in the properties of nucleating agents, they are also different in improving the properties of PP. At the same time, the difference of PP itself also affects the transparency of products

influence of raw materials and production process on product performance

influence of matrix resin

homopolymer PP produced by small bulk homopolymer PP, homopolymer PP produced by haymount's ring tube continuous method and random copolymer PP are used as the matrix resin of medical transparent materials respectively. Under the condition that the proportion and type of other additives remain unchanged, it can be seen that the haze, gloss, impact strength, thermal deformation temperature and other indicators are different. In terms of optics, random copolymerization of PP is the best, and continuous homopolymerization of PP is equivalent to intermittent small bulk homopolymerization of PP; In terms of mechanical properties, random copolymer PP has the best impact strength; In terms of thermal deformation temperature, homopolymer PP is better than random copolymer PP

influence of different nucleating agents

homopolymer PP is used as the base material. Under the same process conditions, different nucleating agents are added for comparison. It is found that the performance of PP is improved to varying degrees after adding nucleating agents. Sorbitan derivatives can be dissolved in molten polypropylene to form a homogeneous solution. When the polymer is cooled, the nucleating agent forms a fibrous complex structure with a great surface area, and the surface of this complex becomes the crystallization nucleation center. The lattice is not only evenly dispersed, but also has a fiber diameter of 7. Refrigerant high pressure protection switch: protect the compactor, prolong the service life of about 10nm, which is equivalent to the thickness of PP lamellae, and is conducive to the crystallization nucleation process, Also, because the fiber diameter is smaller than the visible wavelength and cannot scatter visible light, the nucleating agent can effectively improve the transparency of PP

influence of the amount of nucleating agent

sorbitan derivative nucleating agent with good transparency was selected to investigate the effect of the amount of nucleating agent on the transparency of pharmaceutical PP. It is found that when the amount of nucleating agent exceeds 0.3%, the transparency improvement effect is not obvious, and even decreases; However, when the dosage is less than 0.2%, the amount of nucleation is insufficient and the transparency is not increased enough. Therefore, the best dosage of nucleating agent is 0 Between 3%

effect of extrusion temperature

the transparency of PP was investigated when the plasticizing temperature was 200 ℃, 220 ℃ and 250 ℃, and it was found that the nucleating agent had the best effect on the transparency of PP when the extrusion temperature was at the intermediate temperature. This is mainly due to the decomposition and volatilization of a small amount of low molecular substances in the nucleating agent at higher temperature, which not only brings odor to the product, but also reduces the effective components in the nucleating agent and reduces the improvement effect on transparency; At higher temperature, the original crystal nucleus in PP was destroyed more during melt plasticization, and the heterogeneous nucleation center was reduced, resulting in the reduction of modification effect. At low temperature, the nucleating agent is not dispersed well

effect of toughening agent and its addition amount

the addition of toughening agent is to improve the impact resistance of products, but it will reduce the improvement effect of nucleating agent on transparency. With the increase of the amount of toughening agent, the light transmittance of PP also decreases, because the toughening agent is not miscible with pp. as a discontinuous phase, the toughening agent refracts on the interphase interface due to its different refractive index from PP, which affects the light transmittance of the article. And the higher the content of toughening agent, the larger the area of mutual phase interface, the stronger the refraction of light, and the worse the light transmittance of products

influence of extrusion equipment

compared with single screw extruder, the shear mixing effect of twin screw extruder 50 is significantly better, mainly because the average residence time of materials in twin screw extruder is half of that of single screw extruder, and the distribution range of residence time is only one fifth of that of single screw extruder. Because the residence time distribution of materials is narrow, and the physical and chemical changes of materials in the barrel are roughly the same, the performance of each part in the mixture is also more uniform

influence of product molding processing parameters

transparent PP for medicine can be widely used to prepare medical injection products, drug packaging bottles, boxes, bags, plates, films, etc. For transparent PP for medicine, the different process parameters during molding also have a great impact on the transparency of its products. Therefore, how to get plastic products with good transparency depends not only on the preparation of transparent PP for medicine in the first step, but also on the process control during molding, which is a good way to improve the transparency of PP. For transparency, the main influencing parameters are processing temperature, cooling temperature, injection pressure, etc

effect of molding temperature on transparency

the lower the molding temperature of medical transparent PP, the more original crystal nuclei remain in the melt, which will make the crystal size smaller, thus further improving the transparency

effect of cooling temperature

pp has five different crystal forms, and different crystal forms will affect the transparency of PP. The more hexagonal crystal forms, the better the transparency. Lowering the cooling temperature can increase the pseudo hexagonal crystal form in PP, that is, it will increase the transparency. At the same time, accelerating the cooling rate and the melt passing through the crystallization zone rapidly will reduce the crystallinity. The lower the crystallinity, the better the transparency

influence of injection pressure, time and holding time

injection pressure, injection time and holding time will affect the orientation of products. Too much pressure and too short injection and holding time will increase the orientation during molding, and the increase of orientation will increase the generation of birefringence and reduce transparency

influence of molding process

different processing processes also have a certain impact on the transparency of products. Comparing the products obtained by injection, drawing and blowing processes, it is found that injection and drawing and blowing processes are the most beneficial to increase transparency

influence of mold

the surface finish of the mold will also affect the transparency of the product. The higher the surface finish is, the better the transparency and gloss of the product will be. Generally, transparent products need molds with specular luster

application of products

homopolymer PP is selected as the base resin, sorbitan derivatives are used as nucleating agent in combination with other additives. Under the production condition of maximum temperature of 220 ℃, through Φ 92 twin screw extruder extrusion granulation, you can get medical transparent PP special material

the material was sent to the medical equipment administration of the State Pharmaceutical Administration of China for testing. The results showed that the physical mechanical properties, chemical properties and biological properties of the product met the requirements of the industry standard "polypropylene special materials for medical infusion, blood transfusion and syringe" issued by the State Pharmaceutical Administration

in addition to the production of medical equipment, at present, the application of medical transparent PP in medical packaging is more and more widely used to extend the service life. For example, IMA plans to provide guidance, liquid medicine bottles, medicine bags and so on for designees, architects and construction personnel through a series of UK industry roundtables in 2018. In addition to the influence of the above processing technology and additives on transparent PP, the production environment and hygiene are also one of the main factors affecting the application of transparent PP

reprinted from: plastic industry

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