Inert materials refer to materials with very stable chemical properties and are not easy to react with other substances.
For example, bio-inert materials refer to a kind of biomedical materials that can remain stable in the biological environment and do not have or only have weak chemical reactions, mainly inert bioceramics and medical metals and alloys. Because there is no completely inert material in practice, the biological inert material does not react chemically in the body, and its combination with the tissue is mainly a mechanical mosaic formed on the rough surface of the tissue, that is, morphological combination.
Common biologically inert materials and applications are:
polyethylene
Polyethylene is a chain nonpolar molecule, which is extremely stable to chemicals and resistant to acid and alkali. Polyethylene is very tough, flexible and highly insulating. Because of its excellent physical and mechanical properties, polyethylene has good chemical stability, water resistance and biocompatibility, and is odorless, non-toxic and tasteless, and there is no adverse reaction when implanted in the body. Therefore, it is widely used in the field of medical polymers, and it is the most variety of medical polymers. Ultra-high molecular weight polyethylene (UHMWPE) has strong wear resistance, low friction coefficient, small creep deformation, high chemical stability and hydrophobicity, and is an ideal material for making artificial hip, elbow and knuckles. High density polyethylene can also be used as artificial lung, artificial trachea, artificial larynx, artificial kidney, artificial urethra, artificial bone, orthopedic repair materials and disposable medical supplies.
polyvinyl chloride
The polymerization degree of PVC is about 5,906,5438+0,500 (the number average molecular weight of BP is about 36,000-93,000), and it has good chemical stability, chemical resistance and organic solvent resistance, and its action on acids (hydrochloric acid with arbitrary concentration, 90% sulfuric acid, dilute nitric acid and alkali below 20%) and salts is stable at room temperature. Soluble in dimethylformamide, cyclohexanone, tetrahydrofuran and other solvents, it has good mechanical and electrical properties and poor stability to light and heat. Its softening point is 80℃, and it begins to decompose and discolor at 130℃ to precipitate hydrogen chloride. PVC products are divided into soft products and hard products. The properties of PVC can be improved by adding plasticizers, such as dibutyl phthalate, dioctyl phthalate, epoxidized soybean oil and triphenyl phosphate. Plasticizer can increase the stretchability and elasticity of PVC, but it will reduce the tensile strength.
Since 265438+20th century, it has been found that vinyl chloride monomer has carcinogenic toxicity. It is stipulated in many countries that the residual vinyl chloride in PVC products used for medical purposes and food packaging must be less than that in soft PVC products with 1 ppm dissolution less than 0.05ppm plasticizer. For example, the hemolysis and toxicity of plasticizers used in making implants, infusion bags and blood storage bags must be considered, and strict screening must be carried out according to the safety conditions of materials. PVC products have good properties except poor thermal stability and are difficult to heat, boil and disinfect. big
This amount is used for blood storage and transfusion bags, as well as for manufacturing transfusion tubes, blood vessels, extracorporeal circulation devices, artificial peritoneum, artificial urethra, bag-type artificial lung barrier (e-bag) and working heart.
acrylic resin
Acrylic resin is formed by polymerization or * * * polymerization of acrylate, methacrylate or substituted acrylate. Acrylic resin has the characteristics of biological inertia, good histocompatibility, non-toxic (carcinogenic, teratogenic and mutagenic), easy sterilization, good mechanical strength, strong adhesion and room temperature curing. Widely used in biomedical and medical fields. The most commonly used acrylic resin is polymethyl methacrylate (PMMA), commonly known as plexiglass, which has good biocompatibility, aging resistance and high mechanical strength. In medicine, it is used for skull repair materials, artificial bones, artificial joints, chest cavity filling materials, adhesives for artificial joints and bone materials, as well as dentures and dentures. Modified hydrophilic PMMA has been used in ophthalmology, burn dressings, microcapsules and other fields.
polytetrafluoroethylene
Known as the "king of plastics", PTFE is polymerized from tetrafluoroethylene monomer: with inorganic peroxide as initiator, it can be divided into high-pressure method and low-pressure method according to polymerization pressure.
Polytetrafluoroethylene is the best high temperature resistant plastic with a crystallization melting point as high as 327℃. It is almost completely chemically inert, self-lubricating or non-viscous, difficult to be penetrated by interstitial fluid, and has excellent chemical resistance, electrical properties, surface properties and physical and mechanical properties. It is not easy to coagulate, and the tissue reaction is small after implantation. Widely used in artificial organs and tissue repair materials, medical sutures, medical equipment materials and so on. For example, artificial ureter, bile duct, trachea, larynx, ligaments and tendons, esophageal dilator, artificial blood, artificial heart valve, artificial blood vessel and heart valve. & gt
Is there such a thing as inert metal in chemistry?
Inert metal: refers to metals with stable chemical properties, such as gold, silver, platinum and mercury.
Why is silver an inert metal, but it is easily oxidized?
Why do silver ornaments turn black/yellow? Both 925 and foot silver will turn yellow due to oxidation. The oxidation of silver is mainly sulfide. Many sulfur-containing substances in the air will react with silver, so the color of silver can also be used as one of the criteria to judge the surrounding environment. After palladium and rhodium electroplating on 925, the coating has good oxidation resistance and is not easy to yellow. Yellowing of silver ornaments will also be related to the wearer's physique.
But from a chemical point of view, it is generally believed that yellowing is only related to the oxidation of silver. Platinum, palladium and rhodium are inert metals, which are not easily oxidized under normal circumstances, so the yellowing of silver ornaments has nothing to do with it, while copper oxide is black and has nothing to do with it. So it is mainly the oxidation of silver, although the oxide of silver is black.
1, the best way to maintain silver jewelry is to wear it every day, because human oil can produce a natural and moist luster.
2. Don't wear other precious metal jewelry when wearing silver jewelry to avoid collision, deformation or wear.
Keep the silver ornaments dry, don't take them to swim, and don't go near hot springs and seawater. When not in use, you can gently wipe the surface with cotton cloth or paper towel to remove moisture and dirt, and put it in a sealed bag or box to avoid contact with air.
If the silver ornaments show signs of yellowing, the easiest way is to gently wash the surface with toothpaste and water. Or use a small jewelry brush to clean the fine seams of silver ornaments, and then gently wipe the surface with silver cloth, and the original aesthetic feeling can be restored immediately. (If the silver cloth can recover 80% to 90% silvery white, don't use silver lotion and silver washing water again, because they are corrosive, and silver ornaments will become beautiful after using these products.
5. The silverware is seriously yellowed, so it should not be soaked in silver washing water for too long, usually in a few seconds. Rinse with clear water immediately after taking it out, and then dry it with a paper towel.
6. If the silver cloth can restore about 80% silver, there is no need to use silver lotion and silver washing water, because these products are corrosive, and silver ornaments are more likely to turn yellow after using these products. Silver wipes contain silver maintenance ingredients and cannot be washed.
7. If you don't handle and collect the silver jewelry after wearing it, it is likely to make the silver jewelry black. At this time, you should use a small jewelry brush to clean the fine seams of the jewelry, then drop a drop of silver emulsion on the paper towel to wipe off the black oxide on the surface of the jewelry, and then use a silver cloth to restore the original brightness of the jewelry. After that, you should remember to do a good job of daily general maintenance to prevent the silver ornaments from blackening again, because it is difficult to whiten the silver ornaments after many times of blackening.