The basic requirements for medical plastics are chemical stability and biological safety, because they will come into contact with drugs or the human body. The components in the plastic material cannot be precipitated into the liquid medicine or the human body, will not cause toxicity and damage to tissues and organs, and are non-toxic and harmless to the human body. In order to ensure the biological safety of medical plastics, the medical plastics that are usually sold on the market have passed the certification and testing of medical authorities, and users are clearly informed which brands are medical grade.
Commonly used medical plastic materials are polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polyamide (PA), polytetrafluoroethylene (PTFE), polycarbonate (PC), polystyrene (PS), polyetheretherketone (PEEK), etc., PVC and PE account for the largest amount, accounting for 28% and 24% respectively; PS accounts for 18%; PP accounts for 16%; engineering plastics account for 14%.
The following introduces the plastics commonly used in medical treatment.
1. Polyethylene (PE, Polyethylene)
Features: High chemical stability, good biocompatibility, but not easy to bond.
PE is the general-purpose plastic with the largest output. It has the advantages of good processing performance, low cost, non-toxic and tasteless, and good biocompatibility.
PE mainly includes low-density polyethylene (LDPE), high-density polyethylene (HDPE) and ultra-high molecular weight polyethylene (UHMWPE) and other varieties. UHMWPE (ultra-high molecular weight polyethylene) is a special engineering plastic with high impact resistance, strong wear resistance (the crown of plastics), small friction coefficient, biological inertness and good energy absorption characteristics. Its chemical resistance can be compared with Comparable to PTFE.
General properties include high mechanical strength, ductility and melting point. Density polyethylene has a melting point of 1200°C to 1800°C, while low density polyethylene has a melting point of 1200°C to 1800°C. Polyethylene is a top medical-grade plastic because of its cost-effectiveness, impact resistance, corrosion resistance, and strong structural integrity through frequent sterilization cycles. Due to being biologically inert and non-degradable in the body
Low Density Polyethylene (LDPE) Uses: Medical packaging and IV containers.
High-density polyethylene (HDPE) uses: artificial urethra, artificial lung, artificial trachea, artificial larynx, artificial kidney, artificial bone, orthopedic repair materials.
Ultra-high molecular weight polyethylene (UHMWPE) Uses: artificial lungs, artificial joints, etc.
2. Polyvinyl chloride (PVC, Polyvinyl chloride)
Features: low cost, wide application range, easy processing, good chemical resistance, but poor thermal stability.
PVC resin powder is white or light yellow powder, pure PVC is atactic, hard and brittle, rarely used. According to different purposes, different additives can be added to make PVC plastic parts exhibit different physical and mechanical properties. Adding an appropriate amount of plasticizer to PVC resin can make a variety of hard, soft and transparent products.
The two general forms of PVC used in the manufacture of medical plastics are flexible PVC and rigid PVC. Rigid PVC does not contain or contain a small amount of plasticizer, has good tensile, bending, compressive and impact resistance properties, and can be used as a structural material alone. Soft PVC contains more plasticizers, its softness, elongation at break, and cold resistance increase, but its brittleness, hardness, and tensile strength decrease. The density of pure PVC is 1.4g/cm3, and the density of PVC plastic parts with plasticizers and fillers is generally in the range of 1.15~2.00g/cm3.
According to incomplete estimates, about 25% of medical plastic products are PVC. Mainly due to the low cost of the resin, wide range of applications, and easy processing. PVC products for medical applications include: hemodialysis tubing, breathing masks, oxygen tubes, cardiac catheters, prosthetic materials, blood bags, artificial peritoneum, etc.
3. Polypropylene (PP, polypropylene)
Features: non-toxic, tasteless, good mechanical properties, chemical stability and heat resistance. Good insulation, low water absorption, good solvent resistance, oil resistance, weak acid resistance, weak alkali resistance, good molding, no environmental stress cracking problem. PP is a thermoplastic with excellent performance. It has the advantages of small specific gravity (0.9g/cm3), easy processing, impact resistance, flex resistance, and high melting point (about 1710C). It has a wide range of applications in daily life, pp molding shrinkage rate is large, and the manufacture of thicker products is prone to defects. The surface is inert and difficult to print and bond. Can be extruded, injection molded, welded, foamed, thermoformed, machined.
Medical PP has high transparency, good barrier and radiation resistance, making it widely used in medical equipment and packaging industries. The Non-PVC material with PP as the main body is a substitute for the widely used PVC material at present.
Uses: Disposable syringes, connectors, transparent plastic covers, straws, parenteral nutrition packaging, dialysis films.
Other industries include woven bags, films, turnover boxes, wire shielding materials, toys, car bumpers, fibers, washing machines, etc.
4. Polystyrene (PS, Polystyrene) and Kresin
Features: low cost, low density, transparent, dimensional stability, radiation resistance (sterilization).
PS is a plastic variety second only to polyvinyl chloride and polyethylene. It is usually processed and applied as a single-component plastic. Its main features are light weight, transparency, easy dyeing, and good molding performance. Electrical parts, optical instruments and cultural and educational supplies. The texture is hard and brittle, and has a high coefficient of thermal expansion, thus limiting its application in engineering. In recent decades, modified polystyrene and styrene-based copolymers have been developed to overcome the shortcomings of polystyrene to a certain extent. K resin is one of them.
Kresin is formed by copolymerization of styrene and butadiene. It is an amorphous polymer, transparent, odorless, non-toxic, with a density of about 1.01g/cm3 (lower than PS and AS), and higher impact resistance than PS. , transparency (80-90%) is good, the heat distortion temperature is 77 ℃, how much butadiene is contained in the K material, and its hardness is also different, because the K material has good fluidity and a wide processing temperature range, so its Good processing performance.
Crystalline Polystyrene Uses: Laboratoryware, petri and tissue culture dishes, respiratory equipment and suction jars.
High Impact Polystyrene Uses: Catheter trays, cardiac pumps, dural trays, respiratory equipment, and suction cups.
The main uses in daily life include cups, lids, bottles, cosmetic packaging, hangers, toys, PVC substitute products, food packaging and medical packaging supplies, etc.
5. Acrylonitrile-butadiene-styrene copolymers (ABS, Acrylonitrile Butadiene Styrene copolymers)
Features: Hard, with strong impact resistance, scratch resistance, dimensional stability, etc., moisture-proof, corrosion-resistant, easy to process, and good light transmission. The medical application of ABS is mainly used as surgical tools, roller clips, plastic needles, tool boxes, diagnostic devices and hearing aid housings, especially the housings of some large medical equipment.
6. Polycarbonate (PC, Polycarbonate)
Features: Good toughness, strength, rigidity and heat-resistant steam sterilization, high transparency. Suitable for injection molding, welding and other molding processes, prone to stress cracking.
These characteristics make PC preferred as hemodialysis filters, surgical tool handles and oxygen tanks (when in surgical heart surgery, this instrument can remove carbon dioxide in the blood and increase oxygen);
Medical applications of PCs also include needle-free injection systems, perfusion instruments, various housings, connectors, surgical tool handles, oxygen tanks, blood centrifuge bowls, and pistons. Taking advantage of its high transparency, the usual myopia glasses are made of PC.
7. Polytetrafluoroethylene (PTFE, Polytetrafluoroethylene)
Features: high crystallinity, good heat resistance, high chemical stability, strong acid and alkali and various organic solvents are not affected by it. It has good biocompatibility and blood adaptability, no damage to human physiology, no adverse reaction when implanted in the body, can be sterilized at high temperature, and is suitable for use in the medical field.
PTFE resin is a white powder with a waxy appearance, smooth and non-sticky, and is the most important plastic. PTFE has excellent performance, which is unmatched by ordinary thermoplastics, so it is known as the "King of Plastics". Because its coefficient of friction is the lowest among plastics and has good biocompatibility, it can be made into artificial blood vessels and other devices that are directly implanted into the human body.
Uses: All kinds of artificial trachea, esophagus, bile duct, urethra, artificial peritoneum, brain dura mater, artificial skin, artificial bone, etc.
8. Polyether ether ketone (PEEK, Poly ether ether ketones)
Features: heat resistance, wear resistance, fatigue resistance, radiation resistance, corrosion resistance, hydrolysis resistance, light weight, good self-lubrication, and good processing performance. Can withstand repeated autoclaving.
Uses: It can replace metals in surgical and dental instruments, and replace titanium alloys in the manufacture of artificial bones.
(Metal instruments may cause image artifacts or affect the doctor's surgical field of view during minimally invasive surgery clinical operations. PEEK is as tough as stainless steel, but it will not produce artifacts.)
9. Polyamide (PA Polyamide) commonly known as nylon, (Nylon)
Features: It has flexibility, bending resistance, high toughness and is not easy to break, chemical tablet resistance and abrasion resistance. Does not release any harmful substances and therefore does not cause skin or tissue inflammation.
Uses: Hoses, Connectors, Adapters, Pistons.
10. Thermoplastic Polyurethane (TPU)
Features: It has good transparency, high strength and tear performance, chemical resistance and abrasion resistance; wide range of hardness, smooth surface, anti-fungal and microorganism, and high water resistance.
Uses: medical catheters, oxygen masks, artificial hearts, drug release equipment, IV connectors, rubber pouches for blood pressure monitors, wound dressings for extracutaneous administration.
Post time: Dec-09-2023