In the medical industry, the use of plastic is very common, whether it is medical machinery or medical consumables, a large amount of plastic is used. Because compared with glass and metal materials, plastic has the following characteristics:
①The cost is low, suitable for the production of disposable medical supplies;
②The processing is simple, and its plasticity can be processed into a variety of useful structures, while metal and glass are difficult to manufacture into complex structures;
③Tough, flexible, not as easily broken as glass;
④It has good chemical inertness and biological safety.
However, the medical industry has very strict and special requirements for its plastic materials：
⑴Since most monomers and their oligomeric compounds contain harmful components to the human body, there are quite strict restrictions on the corresponding residues on medical plastics;
⑵It is inevitable that plastics will use reactors, metal catalysts, and other materials containing metal ions in the polymerization process. Therefore, there will be strict regulations on the residual metal ions such as lead, cadmium, copper, zinc, tin, and barium in medical plastics;
⑶Medical plastics require high resin purity and narrow molecular weight distribution;
⑷The additives in the plastic modification process need to use non-toxic additives to prevent and reduce the precipitation of the additives during long-term use, which affects the product performance and therapeutic effect;
⑸Internal medical plastics also have special functional requirements such as surface hydrophilicity, anticoagulant properties, and radiation sterilization resistance;
⑹It is inevitable that medical equipment and appliances come into contact with some liquid medicines during use, so there are certain requirements for the acid and alkali resistance of plastics;
⑺Most medical equipment is adjustable and rotating automation equipment, so there is a need for self-lubricating plastic;
⑻The light usage rate in the working environment of the hospital is relatively high, and the weather resistance is also the rigid requirement of the equipment on the plastic;
⑼X-ray equipment, B-ultrasound equipment, ultrasound equipment, and other special diagnostic equipment require the use of anti-radiation plastic materials.
So what are the commonly used medical plastic materials? There are mainly seven types of PVC, PE, PP, PS, ABS, PC, and PTEE.
1. PVC(Polyvinyl chloride)
PVC is one of the most produced plastic varieties in the world. PVC resin is white or light yellow powder. Pure PVC is hard and brittle and is rarely used.
Therefore, different additives will be added according to different uses to make PVC plastic parts present different physical and mechanical properties. Adding an appropriate amount of plasticizer to PVC resin can make a variety of hard, soft, and transparent products.
Hard PVC does not contain or contains a small amount of plasticizer, has good tensile, flexural, compressive, and impact resistance, and can be used as a structural material alone.
Soft PVC contains more plasticizers, its flexibility, elongation at break, and cold resistance increase, but its brittleness, hardness, and tensile strength decrease.
PVC products for medical applications include hemodialysis tubing, breathing mask, oxygen tube, etc.
Polyethylene plastic is the most produced variety in the plastics industry. It is milky white, tasteless, odorless, and non-toxic glossy waxy particles. It is characterized by low price and good performance. It is widely used in industry, agriculture, packaging, and daily industries, and occupies a pivotal position in the plastics industry.
PE mainly includes low-density polyethylene (LDPE), high-density polyethylene (HDPE) and ultra-high molecular weight polyethylene (UHDPE), etc.
HDPE has fewer branches on the polymer chain, higher relative molecular weight, a high degree of quality and density, higher hardness and strength, poor opacity, and higher melting point. It is often used in injection molded parts.
LDPE has many branches, so the relative molecular weight is small, the crystallinity and density are low, and it has good flexibility, impact resistance, and transparency. It is often used for blown film and is an alternative to the widely used PVC.
UHDPE has high impact strength, low friction, stress crack resistance, and good energy absorption characteristics. It is an ideal material for the production of artificial hip, knee, and shoulder connectors.
Polypropylene is colorless, tasteless, and non-toxic. It looks like polyethylene, but it is more transparent and lighter than polyethylene.
PP is a kind of thermoplastic with excellent performance. It has the advantages of small specific gravity, non-toxicity, easy processing, impact resistance, and flexural resistance. There is also a wide range of applications in daily life, including woven bags, films, wire shielding materials, toys, car bumpers, fibers, washing machines, etc.
Medical PP has a higher transparency, better barrier properties, and radiation resistance, making it widely used in medical equipment and packaging industries. Non-PVC material with PP as the main body is a substitute for the widely used PVC material.
PS is the third-largest plastic species after polyvinyl chloride and polyethylene. It is usually processed and applied as single-component plastics. Its main characteristics are lightweight, transparency, easy dyeing, and good molding and processing properties, so it is widely used in daily Use plastics, electrical parts, optical instruments, and cultural and educational supplies.
In recent decades, the improvement of modified polystyrene and styrene-based copolymers has overcome the shortcomings of polystyrene to a certain extent. K resin is one of them.
K resin is a copolymer of styrene and butadiene. It is an amorphous polymer, transparent, odorless, non-toxic, lower in density than PS and AS, higher in impact resistance than PS, good in transparency, and heat distortion temperature is 77℃. Because the K material has good fluidity and a wide processing temperature range, its processing performance is good.
The main uses in daily life include cups, lids, bottles, cosmetic packaging, hangers, toys, PVC substitute products, food packaging, and medical packaging supplies.
5. ABS(Acrylonitrile Butadiene Styrenecopolymers)
ABS has certain rigidity, hardness, impact resistance and chemical resistance, radiation resistance, and ethylene oxide disinfection resistance.
ABS in medical applications are mainly used as surgical tools, clips, plastic needles, toolboxes, diagnostic devices, and hearing aid housings, as well as the housings of some large medical equipment.
The typical characteristics of PC are toughness, strength, rigidity, and heat-resistant steam sterilization. These characteristics make PC the preferred material for the production of blood dialysis filters, surgical tool handles and oxygen tanks;
PC applications in medicine also include needle-free injection systems, Perfusion instrument, blood centrifuge bowl, and piston. Taking advantage of its high transparency, the usual myopia glasses are made of PC.
7. PTFE(Polytetrafluoro ethylene)
Polytetrafluoro ethylene resin is a white powder, waxy in appearance, smooth and non-sticky, and is the most important plastic.
PTFE has excellent performance, which is not comparable to ordinary thermoplastics, so it is known as the “Plastic King”. 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 directly implanted in the human body.