Application of 10 Common Medical Plastics
Polymer materials, also known as polymer materials, are mainly composed of polymer compounds as the matrix, supplemented by other additives (additives). It can be divided into rubber, fiber, plastic, polymer adhesive, polymer coating, and polymer based composite materials according to their characteristics.
Among them, the application of plastics is more prominent. Due to its excellent properties such as lightweight, high strength, temperature resistance, and corrosion resistance, plastics are widely used in various fields and promote their development. Plastics are no exception in the medical industry. Especially in recent years, in COVID-19 epidemic prevention, what we see most is that medical protective masks, N95 masks, nucleic acid collection tubes and many other epidemic prevention supplies are made of medical plastic, which has made great contributions to epidemic prevention and control.
Development Overview of Medical Plastics in China
The development of medical plastic products in China started relatively late, and it was not until the 1970s that plastic infusion bags were developed and produced. After the Ministry of Health issued a notice in 1987 on promoting the use of disposable plastic infusion sets, blood transfusions, and syringes, it encouraged and stimulated the development and production of medical plastics in China.
The plastic production of medical consumables mostly began after the 1980s. According to the statistics of the China Medical Consumables Association, there are currently only over 1000 enterprises engaged in the production of disposable medical plastics in China with a certain scale.
Due to the backwardness of China's basic industry, there are incomplete categories of raw materials required for medical plastic products, non-standard quality standards, poor stability and reliability of product quality, and some particularly high demand product raw materials still rely on imports. The main suppliers include BASF and DuPont in the United States; Germany's Covestro, Netherlands' Lyonde Basel, Saudi Arabia's Shabik, South Korea's LG Group, Japan's Dongli, etc.
There is also a significant gap between China and developed countries such as Europe, America, and Japan in the research and development of medical plastics, especially in the research on the chemical properties, physical properties, biological properties, compatibility of plastic color masterbatch, additives, and modifiers of medical plastics. Plastic materials meet the standards for medical and food hygiene standards.
The research on the impact of related plastic materials on human health, the binding force with cells, microorganisms, and bacteria molecules, and the relationship between the degradation and anti-aging of plastic materials are just beginning. The relevant industry standards are relatively scarce, and the industrial level needs to be rapidly improved.
Application of Ten Common Medical Plastics
Since the reform and opening up, China has made new breakthroughs in the research, development, and production of engineering plastics. The usage of plastics has ranked first in the world for several consecutive years, while also expanding new avenues for the application of medical plastics.
At present, commonly used medical plastics include engineering plastics and biodegradable materials, as well as some substances such as silicone. Among them, there are about a dozen types of medical plastics, including polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polyurethane (PU), PEEK (polyether ether ketone), polytetrafluoroethylene (PTFE), polycarbonate (PC), polystyrene (PS), etc. PVC and PE have the highest usage, accounting for 28% and 24% respectively; PS accounts for 18%; PP accounts for 16%; Other engineering plastics account for 14%. Biodegradable plastics include polylactic acid (PLA), polyhydroxybutyrate (PHB), and so on.
Below is an introduction to the current application of medical plastics, combined with application cases.
1 PVC
Polyvinyl chloride (PVC) materials are widely used in the medical device industry, mainly due to their excellent physical properties. PVC is also the material with the largest usage of disposable sterile medical devices. PVC is a low-cost amorphous plastic, and its physical properties make it easier to manufacture PVC materials. This type of material has good compatibility with intravenous (IV) injections and blood.
In the medical field, PVC products commonly used in intravenous blood bags, intravenous injection tubes, artificial kidney connective tissue catheters, bubble oxygenators, as well as enema drainage bags and catheterization drainage tubes, all contain dihexyl phthalate (DEHP) plasticizers. The effect of dihexyl phthalate is to increase the elasticity of PVC products. DEHP, as one of the most cost-effective and widely used plasticizers, its function makes PVC soft and flexible.
The use of plasticized polyvinyl chloride (PVC) in medical products was initially intended to replace the use of natural rubber and glass in medical equipment. The reason for this is that plasticized polyvinyl chloride materials have the characteristics of easy sterilization and transparency, as well as better chemical stability and economy.
Plasticized polyvinyl chloride products are convenient to use, with their own softness and elasticity, which can avoid damage to sensitive tissues of patients and prevent discomfort. PVC products used in medical applications include blood bags, blood dialysis tubing, respiratory masks, oxygen tubes, urine bags, infusion tubes, artificial ears and noses, etc. As shown in the following figure.
Application of 10 Common Medical Plastics
Medical blood dialysis tubes
II PE
Polyethylene (PE) is the largest general-purpose plastic in terms of production. Medical polyethylene is a type of plastic obtained from ethylene polymerization, which has excellent mechanical strength and biocompatibility. It is odorless, non-toxic, easy to color, has good chemical stability, cold resistance, radiation resistance, and good electrical insulation.
Medical PE has the advantages of good processing performance, low cost, non-toxic and odorless, and good biocompatibility when implanted into the body without any adverse effects. It is suitable for making packaging materials for food and medicine, making tableware, medical devices, etc. Ordinary PE is usually used for medicine bottles, needle caps, syringe push rods, flow regulators for infusion sets, packaging bags for infusion sets and syringes, etc. As shown in the following figure.
Application of 10 Common Medical Plastics
Syringe push rod
Among them, ultra-high molecular weight polyethylene (UHMWPE) is a special engineering plastic with high impact resistance, strong wear resistance (the crown of plastics), low friction coefficient, biological inertness, and good energy absorption characteristics. Its chemical resistance is comparable to PTFE, making it an ideal material for artificial buttocks and joints.
It has been successfully used in artificial wrist joints, knee joints, acetabulum, etc., effectively solving the friction and wear problems of artificial joints, prolonging their service life. UHMWPE has good biocompatibility and excellent mechanical strength, and is widely used in biological scaffolds.
Application of 10 Common Medical Plastics
Artificial joint schematic diagram
III PP
Polypropylene (PP) has excellent chemical resistance, fatigue resistance, good heat resistance, and can be disinfected and sterilized at temperatures above 100 ℃. Easy to process, without environmental stress cracking issues. Medical PP has high transparency, good barrier properties, and radiation resistance.
Can be applied to infusion bags, disposable syringes, disposable gloves, drip transparent tapes, connectors, parenteral nutrition packaging, dialysis membranes, etc. Polypropylene fiber materials are widely used in the medical field, and PP non-woven fabric belongs to the category of polypropylene specific fiber materials. PP fiber materials can also be used as blood filters, surgical repair patches, sutures, and so on.
Of course, polypropylene can also be used as hardware products due to its good chemical stability, mechanical properties, and physiological degradation. It is often used as a flat artificial kidney splint and other products. If the surface of polypropylene is treated with an active agent, it can also be used to produce artificial lungs.
In COVID-19 epidemic prevention, the most common PP medical product is the medical mask, which is composed of melt blown cloth and non-woven cloth. The main material of melt blown fabric is specialized polypropylene melt blown special material.
IV PS and K resin
Polystyrene (PS) is second only to PVC and PE in terms of usage in the medical field, with a hard and brittle texture and a high coefficient of thermal expansion, which limits its application in engineering. In recent decades, modified polystyrene and copolymers based on styrene have been developed, which to some extent overcome the shortcomings of polystyrene.
Application of 10 Common Medical Plastics
The above picture shows the COVID-19 antigen self test box, which is assembled by the upper cover and lower shell, and has played an important role in the epidemic.
Currently, it is produced using PS, as well as ABS, and K resin is one of them. Transparent impact resistant resin of butadiene styrene, also known as K-Resin. K-resin is a block copolymer formed by polymerization of styrene and butadiene as monomers. Its main characteristics are high transparency and good impact resistance, low density, strong coloring power, excellent processing performance, and non-toxic.
K resin is mainly used in medical plastic products with high processing technology difficulty, high technical content, and high added value, such as artificial lung oxygenators, arterial vessel outlets, recovery device arterial outlets, cardiac suction heads, aortic catheters, blood filters, transductors, and thermostats. At the same time, K resin meets the VI-50 level requirements of the US Drug Packaging Act.
V ABS
ABS is a ternary copolymer of acrylonitrile (A), butadiene (B), and styrene (S), and is a widely used engineering plastic. Medical ABS has certain rigidity, hardness, impact resistance, chemical resistance, radiation resistance, and resistance to ethylene oxide disinfection. ABS is mainly used in medical applications as surgical tools, roller clips, plastic needles, tool boxes, diagnostic devices, and hearing aid casings, especially for some large medical equipment casings.
As shown in Figure 5. Select the appropriate ABS type and grade according to the structure and strength requirements of medical devices, and process them accordingly. These properties include processing performance, mechanical strength, usage cost, assembly method, reliability, etc.
Transparent ABS has the characteristics of high transparency, high rigidity, chemical resistance, as well as resistance to gamma disinfection and high-temperature disinfection. In the medical field, it can be applied to indwelling needles with high requirements for chemical resistance and gamma virus resistance, components with high transparency and glossiness in atomizers, as well as other hard transparent interfaces, such as interfaces for respiratory accessories, three-way interfaces, Ruhr joints, transparent joints, etc.
Application of 10 Common Medical Plastics
Schematic diagram of using ABS as a casing for medical instruments
VI PC
Polycarbonate (PC) is a thermoplastic resin containing - [O-R-O-CO] - links in the molecular main chain. In practical applications, aromatic polycarbonate is the main type with practical value, and bisphenol A polycarbonate is the most commonly used.
Polycarbonate is a widely used engineering plastic, and the important performance advantages of PC in the medical industry include high strength, good toughness, high rigidity, good transparency, and the ability to withstand strict disinfection conditions.
PC is commonly used in open heart surgery for dialysis filtration membranes, surgical equipment handles, and blood oxygen supply equipment casings, venous connector catheters and plugs, as well as needle free injection system materials, perfusion materials, blood storage materials, etc. PC can also be used for trocar (long tube) and traction devices for endoscopic surgery.
The characteristics of PC include high toughness, strength, and heat resistance for steam disinfection, which make it a preferred choice for blood dialysis filters, surgical tool handles, and oxygen tanks; The application of PC in medicine also includes needle less injection systems, perfusion instruments, blood centrifuge bowls, and pistons.
Application of 10 Common Medical Plastics
Schematic diagram of blood dialysis machine filter
In addition to the application of aromatic polycarbonates, aliphatic polycarbonates have excellent biodegradability, biocompatibility, and functionality, and have rapidly developed in the field of biomedical research in the past decade.
Aliphatic polycarbonates, due to their ability to degrade under physiological conditions, are particularly suitable for implantation in biomedical fields that require temporary presence in the body, such as drug controlled release system carriers, tissue engineering, surgical sutures, etc.
7 PTFE
Polytetrafluoroethylene (PTFE) is a type of fluoroplastic, which is a white opaque waxy powder with a density of 2 14-2 20 g/cm3 is the highest density resin material and is known as the king of plastics. It has the lowest friction coefficient and the best chemical resistance among plastics.
Good biocompatibility and anticoagulation, non decomposing, no adverse reactions and no obvious aging in the implanted body, excellent heat resistance, continuous use temperature of 260 ℃, and can be disinfected at high temperature.
Polytetrafluoroethylene products used in medical applications have three applications: first, they directly enter the human body; 2、 Products for external use; 3、 Functional components and devices in biochemical synthesis equipment.
Tissue cells and blood vessels can grow into their micropores to form tissue connections, just like autologous tissue. This type of tissue healing method, which involves tissue growth, is superior to the traditional fiber wrapped tissue healing method of silicone rubber. Expanded polytetrafluoroethylene has become an important filling material in medicine and is currently an ideal biological tissue substitute.
Application of 10 Common Medical Plastics
At present, it has been used in nasal plastic surgery, heart valves, artificial blood vessels, elimination of residual lung cavities, and various artificial trachea, esophagus, bile duct, urethra, artificial peritoneum, cerebral dura mater, artificial skin, artificial bones, and other aspects.
8 TPU
Thermoplastic polyurethane elastomers (TPU) are mainly used as medical polyurethane elastomers. Thermoplastic polyurethane is a linear block polymer composed of soft chain segments (long chain oligomers) and hard chain segments (diisocyanates and chain extenders).
Due to the strong polarity of hard chain segments, the microphase region of hard chain segments is formed through hydrogen bonding and distributed in the matrix of soft chain segments to form a physical cross-linking point, thereby giving the elastomer the elastic recovery performance of vulcanized rubber.
Due to the different polarity between the soft and hard segments in the molecular structure of polyurethane, this structure makes it biocompatible. Due to its convenient handling and excellent performance, TPU has been widely used in various medical and health products, such as medical materials that can be used for long-term and short-term implantation in the human body.
The application of polyurethane elastomers: Polyurethane was first used as a fracture repair material, and then successfully used as an auxiliary coating for vascular surgical sutures.
In the 1980s, polyurethane elastomers were successfully used for artificial heart transplantation. Artificial heart assistive devices are used as elastomers and encapsulation for artificial heart diaphragms, and require good biological and blood compatibility, as well as excellent mechanical strength, especially bending resistance. If the heartbeat is calculated at 70 beats per minute, the implanted heart will have to withstand 40 million bends per year, and if implanted for 10 years, it will need to withstand 400 million bends.
The artificial heart balloon developed in the 1960s is made of silicone rubber and natural rubber. Although it has good biocompatibility, it cannot meet the requirements of anti flexibility. The polyurethane elastic airbag, successfully developed in the early 1980s, has been tested to withstand over 500 million flexion cycles and has been successfully applied to artificial hearts.
Therefore, all countries in the world tend to use polyurethane materials for the development of artificial hearts and assistive devices. The polyurethane elastomer diaphragm material used for artificial hearts is polyether thermoplastic polyurethane, typically composed of polytetrafuran ether ethylene glycol (PTMEG) - MDI (diphenylmethane diisocyanate) or HDI (hexamethylene diisocyanate) - BD or ethylenediamine, solution cast or injection molded.
In order to utilize the excellent biocompatibility of silicone rubber, polyurethane silane block copolymers were also used. Thermoplastic elastomers (TPU) have excellent low-temperature flexibility, resistance to hydrolysis, anticoagulation, and microbial attack. They can also be used in medical catheters, oxygen masks, drug release equipment, IV connectors, rubber bags for blood pressure monitors, and wound wrap for topical administration.
Application of 10 Common Medical Plastics
9 PLA
Polylactic acid (PLA), also known as polylactide. The polymer obtained by polymerization of lactic acid as raw material is derived from raw materials such as corn and cassava. The production process of lactic acid is pollution-free, and the resulting product can be biodegradable, achieving circulation in nature. It is a typical "green plastic" and has attracted much attention in the development of biodegradable polymer materials.
In addition to the advantages of biodegradation, PLA products also have good biocompatibility and have been well researched and clinically applied in the medical field.
The surgical suture made of PLA is biodegradable and automatically degrades and disappears after wound healing, eliminating the need for secondary surgery. Polylactic acid surgical sutures have strong tensile strength and can effectively control the degradation rate. As the wound heals, the sutures automatically and slowly degrade;
In dentistry, it is used to treat periodontal disease. After surgery, a guided tissue regeneration membrane made of PLA is used to implant into periodontal tissue to repel epithelial cell movement, support periodontal tissue, and slowly grow and regenerate. Another type is a space filling material used for tooth extraction, which can fill cavities to help heal wounds as soon as possible;
Retinal detachment is solved by implanting fillers on the surface of the sclera in surgical treatment. Traditional fillers are made of silicone rubber and silicone rubber sponge, but due to their non biodegradability, they can cause varying degrees of foreign body reactions. The biodegradability and biocompatibility of polylactic acid are used as fillers to solve the problem of foreign body reactions. Polylactic acid has other uses in ophthalmology;
Traditional treatments for fractures and bone defects typically use stainless steel metal materials, such as metal bone plates and screws, as the internal material.
Stainless steel materials have much greater strength and toughness than human bones, and their mechanical properties cannot dynamically change with the bone healing process. After fracture healing, a second surgery is required to remove the stainless steel parts. Both PLA and polyglycolic acid (PGA) have high modulus and tensile strength, and low elongation at break, making them suitable for orthopedic fixation materials. There is no need for a second surgery to remove them, reducing patient pain and simplifying surgical procedures.
Polylactic acid, as a scaffold material for tissue engineering, is used to cultivate tissue cells in the early stages and gradually grow into tissues and organs. At the same time, polylactic acid slowly degrades and is ultimately absorbed by the body; PLA has been used as a carrier for long-acting sustained-release drug formulations. In the past 30 years, polylactic acid and its copolymers have been used as soluble substrates for some drug controlled release formulations with short half-life, poor stability, easy degradation, and significant toxic side effects. This effectively expands the delivery pathway, reduces the number and dosage of administration, improves the bioavailability of drugs, and minimizes the toxic side effects of drugs on the liver and kidneys.
10 PHB
Polyhydroxybutyrate (PHB) is a natural polymer stored in cells by microorganisms under unbalanced growth conditions. It is widely present in many prokaryotes in nature and is a type of thermoplastic biodegradable material manufactured by microbial fermentation agents. It not only has properties similar to those of chemically synthesized polymer materials, but also has properties that are not commonly found in synthetic polymers. Special properties such as biodegradability, biocompatibility, non toxicity, and non immunogenicity.
PHB is used as a drug sustained-release carrier material, and anti-cancer drugs are sustained-release using PHB microspheres. Low molecular weight PHB microspheres have a faster drug release rate, while high molecular weight PHB microspheres have a slower drug release rate but better therapeutic effect;
PHB is applied as a cell scaffold material, which has good biodegradability and biocompatibility, non-toxic, non irritating, non immunogenic, insoluble in blood, beneficial for cell adsorption and maintaining differentiation, and has advantages in price;
PHB porous scaffold, as a carrier material for chondrocytes, has a good effect on repairing damaged cartilage tissue and is used for joint cartilage, ear cartilage, tracheal cartilage, etc;
PHB membrane guides the regeneration of bone tissue around the implant, and PHB serves as a matrix material, bone plate, and bone repair material for repairing bone tissue defects caused by trauma or disease;
PHB is a material used for repairing or reconstructing damaged heart valves, as well as for tissue materials such as blood vessels, skin, and nerves;
PHB has special properties such as biocompatibility and has been successfully applied in the field of medical surgical sutures. Sutures made from PHB have been launched, ending the history of absorbable sutures relying on imports. Of course, there are other materials available for medical biodegradable plastics.
At present, biodegradable materials have broad prospects in the medical field, with advantages such as compatibility, degradability, non toxicity, non irritation, non immunogenicity, and insolubility in the blood. Especially in the internal application of the human body, they have superior advantages.
The integration of 3D printing technology and medicine has formed 3D bioprinting technology, which benefits humans in applications such as bone repair and dentures. Medical plastics play an important role. I believe that with the development of science and technology, the development and utilization of medical plastics will better serve humanity.
