At designing and manufacture of medical products of JSC MEDSIL uses various polymeric materials: the silicon rubber, a polyurethane, polythene, polyvinyl chlorid, polyamide, etc. The greatest value and application is found with the silicon rubber and a polyurethane.
Brief data on silicone rubber in terms of medical application
Silicone caoutchouc and, accordingly, silicone rubbers (SR) on its basis are referred to the group of silico-organic polymers (also called silicones, polyorganosiloxanes).
The simplified view of a silicone rubber macromolecule represents the chains of alternating atoms of oxygen and silicone framed by various radicals.
In the 40-s of the XX-th century silicone polymers including liquids, rubbers, caoutchouc, resins, plastics became widely applicable. These polymers were commonly used in different fields of technology, including manufacturing of various medical products. In this sphere silicone rubber is nearly unparalleled and has no equal among polymeric materials due to the complex of unique properties.
Bioinertness and biostability
These properties are decisive for use in medical devices. Long-term experience (SR was applied as an implant for the first time in 1948) has shown that well manufactured SR products almost do not experience toxic effect, do not cause irritation of tissue and body’s environment, they do not provoke allergic reactions nor while external contact and during short-term introduction into the body, for example, into the lumen of digestive tract, neither during long-term (including lifelong) implantation.
These characteristics are also important, but hardly achievable at the required level for medical polymeric products. However, unique surface properties (water repellency, anti-adhesiability, including, in relation to surrounding tissue, bad compatibility with other substances) allow to use SR successfully in cardiosurgery (heart surgery) for contact with blood, in neurosurgery, urology, etc.
Resistance to sterilization impact
Due to a wide range of usage temperatures (from – 60°C to + 150 – 200 °C) and high hydrolytic resistibility SR products can endure the air method of sterilization (at 180°C), sterilization by means of live steam in an autoclave at 120-1300C as well as sustained boiling in water.
SR are quite inert chemically; they are resistant to ethylic spirit, acetone, hydric dioxide, weak acids and alkalis, solutions of salts, ammonia. However, SR swell up notably under the influence of gasoline, aromatic solvents and chlorinated hydrocarbons (swelling is convertible).
The above mentioned properties of SR have determined its application in medicine. it is safe to say that products made from SR are used almost in all spheres of surgery and are inserted in all the areas of the human body for different periods of time. Products from SR are used in the general surgery, cardiovascular surgery, chest surgery, neurosurgery, maxillofacial surgery, otolaryngology, ophthalmology, orthopedy, urology, stomatology, gynecology, and anesthesiology.
On the basis of both domestic and foreign experience our researchers and technicians have developed various compositions of SR with essential improved medico-technical properties. It should be stated that for more than twenty years the advanced method of catalitic (“platinum”) SR vulcanization (instead of an older peroxide method) has been used while manufacturing medical products. This method is used worldwide for the production of key medical products from SR (implants, endoprostheses, etc.)
A wide range of medical products from SR for different purposes have been designed and applied in batch production by MEDSIL’s staff:
- the first Russian implanted wires – electrodes for electrostimulators of heart activity
- the model of artificial heart finished with a stage of experiments on animals
- the first domestic tubes, probes and drainages from silicone rubber
- implanted systems for treatment of hydrocephaly
- silicone implants for eye surgery for scleroplastics of retinal detachment
- laryngeal masks from silicone rubber, etc.
Brief data on polyurethanes
Polyurethanes (PU) represent rather new class of polymeric materials formed as a result of polymerization of two-nuclear spirits (glycols) and diisocyanates (polyethers) of different chemical composition.
In general, PU possess good mechanical properties, high thermal form stability, strong resistance to mineral oils and hydraulic liquids, the increased stability to hydrolysis, frost resistance, resistance to microorganisms’ activity.
Basically thermoplastic PU on the basis of simple polyethers are used for production within JSC MEDSIL.
The major advantage of these materials, comparing to other medical plastics (polythene, polyamide and even PVC) is the presence of some properties indigenous to rubbers. These properties, for instance, significantly reduce the rigidity of tubular medical products (catheters, probes).
PU are resistant to diluted acids and alkalis at room temperature, but collapse by the action of concentrated acids and alkalis in the same circumstances. PU swell (this process is convertible) while contact with sated hydrocarbons (diesel fuel, kerosene, etc.), lose mechanical properties under the influence of aromatic hydrocarbons (benzene, toluene), alyphatic spirits (methanol, ethanol, isopropanol).
PU on the basis of simple polyethers resist microorganisms’ activity, hydrolitic decomposition (in water); they are UV- and ozone-resistant.
The upper bound of the usage temperature for thermoplastic PU is approximately 80° C. That limits the application of hot methods of sterilization to the PU products.
We have an opportunity of colored products manufacturing from all the above-mentioned materials of different transparency degree.
Individual selection of product color is possible.
We can also mark the products with radiopaque labels. JSC MEDSIL produces roentgenopaque tubes or tubes with a roentgenopaque strip.