The basic requirements of medical plastics are chemical stability and biological safety because of their contact with liquid medicine or human body. Medical devices can be subdivided into in vitro diagnosis, medical consumables, medical equipment and pharmaceutical equipment. Because of its low cost, easy processing, light weight and toughness, plastics have been widely used in medical devices.

The requirements for polymer materials are different according to different use environments of medical devices, but generally they should have the following properties:

1. Good physical and mechanical properties, which can meet the requirements of relevant functions;

2. Good chemical resistance, which can meet the service life in the service environment, and will not affect the relevant performance after disinfection;

3. Good molding processing performance, easy to process into various shapes of products;

4. Non toxic, no "three carcinogenic" (carcinogenic, teratogenic and mutagenic) effects, no heat source reaction, low content of dissolved and soluble substances;

5. Do not destroy adjacent tissues, do not interfere with the immune mechanism of the body, and do not cause material surface calcification;

6. It has good anticoagulation performance. When the material contacts with blood, it will not cause blood cell reduction after hemolysis, protein denaturation in blood, or damage the visible components of blood;

7. The material has enough stability when implanted into the body, and the mechanical properties do not change significantly after long-term use (excluding degradable materials).

There are about a dozen kinds of commonly used medical plastics, including polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polyurethane (PU), polytetrafluoroethylene (PTFE), polycarbonate (PC), polystyrene (PS), etc. PVC and PE are the most used, accounting for 28% and 24% respectively; PS accounts for 18%; PP accounts for 16%; Engineering plastics account for 14%.

01PVC

PVC is a low cost amorphous plastic with excellent chemical resistance and microbial resistance. According to market estimates, PVC accounts for 28% of the medical plastic market. The advantages of PVC resin are low cost, wide application range and easy processing. The disadvantage is that PVC, as a polar material, can adsorb some drugs, and the plasticizer DEHP may be released to harm human health.

PVC products used in medicine include: blood bags, hemodialysis tubes, respiratory masks, oxygen tubes, urine bags, artificial ear and nose, etc.

02PE

PE is a general plastic with the largest output. It has the advantages of good processability, low cost, non-toxic and tasteless, and good biocompatibility. Ordinary PE can usually be used for medicine bottles, needle caps, syringe push rods, flow regulators for infusion sets, packaging bags for infusion sets and syringes, etc.

UHMWPE (Ultra High Molecular Weight Polyethylene) is a special engineering plastic with high impact resistance, strong wear resistance (the best plastic), low friction coefficient, biological inertia and good energy absorption characteristics. Its chemical resistance is comparable to PTFE, and it is an ideal material for artificial hips and artificial joints.

03PP 

PP has excellent chemical resistance, fatigue resistance, heat resistance, and can be sterilized at temperatures above 100 ℃. Easy to process, no environmental stress cracking problem. Medical PP has high transparency, good barrier and radiation resistance.

It can be applied to infusion bags, disposable syringes, connectors, parenteral nutrition packaging, dialysis membranes, etc.

04PS, K resin

The amount of PS used in the medical field is second only to PVC and PE. It is hard and brittle, and has a high coefficient of thermal expansion. Therefore, its application in engineering is limited. 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.

K resin is a block copolymer polymerized from styrene and butadiene. Its main characteristics are high transparency and good impact resistance, low density, strong coloring force, excellent processing performance and non-toxic.

K resin is mainly used in medical plastic products that are difficult to process, high in technology and high in added value, such as artificial lung oxygenator's greenhouse, arterial vessel outlet, recycler's arterial outlet, intracardiac suction head, aortic cannula, blood filter, permeating aspirator, thermostat, etc.

05ABS

ABS plastic is a terpolymer of acrylonitrile (A), butadiene (B) and styrene (S), which has certain rigidity, hardness, impact resistance, chemical resistance, radiation resistance and ethylene oxide disinfection resistance.

The medical applications of ABS are mainly used as surgical tools, roller clips, plastic needles, tool boxes, diagnostic devices and hearing aid housings, especially for some large medical equipment.

06PC

PC is characterized by high toughness, strength and heat resistant steam sterilization, which makes PC preferentially choose to be a blood dialysis filter, surgical tool handle and oxygen tank; The application of PC in medicine also includes needle free injection system, perfusion instrument, blood centrifuge bowl and piston.

07PTFE

PTFE is a kind of fluoroplastics, known as plastic king. It has the lowest friction coefficient and the best chemical resistance among known plastics. It has good biocompatibility and anticoagulation, does not decompose, has no adverse reaction after being implanted into the human body, and has no obvious aging. It has excellent heat resistance. The continuous use temperature is 260 ℃, and high temperature disinfection can be used. In the medical field, it is widely used in various kinds of artificial trachea, esophagus, bile duct, urethra, artificial peritoneum, dura mater, artificial skin, artificial bone, etc.

08TPU

Thermoplastic polyurethane elastomer (TPU) has excellent low-temperature flexibility, hydrolysis resistance, anticoagulation, and microbial resistance. It can be used in medical catheters, artificial hearts, oxygen masks, drug release equipment, IV connectors, rubber bags of blood pressure meters, wound wrapping cloth for external drug administration, etc.

09 Biodegradable plastics

Biodegradable plastics are a kind of ideal medical materials. Inert medical materials (i.e. ordinary medical materials with relatively stable performance) generally have the problems of poor long-term compatibility and the need for secondary surgery, and biodegradable materials avoid these shortcomings. Commonly used medical degradable materials include polylactic acid (PLA), polycaprolactone (PCL), etc.

PCL has good biodegradability, drug permeability, and can stably release drugs for a long time. PCL has good biocompatibility with biological cells. Cells can grow normally on its base frame and degrade into CO2 and H2O. It is used for drug release carriers, cosmetic materials, vascular stents, surgical sutures, cell tissue culture media, etc.

PLA has good mechanical properties and biocompatibility, and can be used for medical suture and implants. In addition, PLA products can form a weak acidic environment on the surface, which has bacteriostatic and antimycotic effects. If other antibacterial agents are used, the antibacterial rate can reach more than 90%, which can be used for antibacterial packaging of products.