Medicine demands a lot from devices applied in this field: toughness, non-toxic, chemical stable, bio-compatible, and all the quality they should exhibit to be safely and effectively operating with our delicate body with reliability and cost efficiency. For now, products produced with plastics take up a large part of medical device industry, and the growing medical market also pumps up the marketplace for medical devices. However, various types of plastic material, each of them exhibiting unique properties, are sometimes confusing to choose from according to your product’s demand. If this problem has been hanging around for you, this post will be the solution to that.
In this poost, a few types of plastic material used for medical purpose as well as their modification & processing techniques for innovative manufacturing will be introduced, including four major plastic material categories including PVC, PP, PE and Teflon. If you wish to develop into this industry, KingStar is always ready to help, from suggestions to services. Here at KingStar, the best molding factory in China, we provide high quality customization service with our professional technicians and developers, ready to fulfill all your demand for high quality plastic products. For direct one-to-one help with practical expertise in this field, please contact us at sales@kingstarmold.com for more information about plastic molding services.
Properties & Application:
PVC material have an excellent performance in electrical & mechanic properties as well as chemical resistance. However, limitations in light resistance and thermal stability still exist. PVC plastic, processed for modification, has been introduced widely for the manufacturing of critical medical products. These include blood collection bags, transfusion bags, blood conduits, artificial peritoneal membranes, urethral catheters, bag-type oxygenators (artificial lungs), cardiac catheters, and artificial heart components.
Processing Details & Suggestions
Processing and molding are difficult for PVC, given its high glass transition temperature (Tg) and significant material rigidity. Consequently, plasticizers and other additives are routinely compounded into PVC resin.
The predominant primary plasticizer used in processing is still Di(2-ethylhexyl) phthalate (DOP). However, DOP is prone to migration and leaching, due to its low molecular weight. To ensure the hygienic safety of medical PVC plastics, new plasticizers are being developed, exhibiting significantly lower toxicity and superior resistance to leaching compared to DOP. This includes citric acid ester with a hygienic safety level, polyesters with high molecular weight, and other polymeric plasticizers.
Regarding PVC stabilizers, lead-based compounds, poisonous to blood, could led to severe anemia, while cadmium-based variants pose even greater risks. In contrast, tin-based stabilizers and epoxidized soybean oil prove to be superior in hygienic safety.
Organotin stabilizers with minimal leaching are generally recommended. Di-n-octyltin di(2-ethylhexyl thioglycolate) is a non-toxic organotin stabilizer offering exceptional thermal stability and transparency, though its lubricity is suboptimal. For compensation, you can introduce calcium stearate (CaSt) and zinc stearate (ZnSt), which are both non-toxic transparent stabilizers, providing effective lubrication.
For medical PVC products, it’s advisable to add N,N′-Ethylene bis(stearamide) (EBS) and silicone oil, both delivering balanced internal & external lubrication. Additional Acrylic Processing Modifiers (ACR) are also recommended as processing aids, enhancing surface quality of finished PVC products.
2. High Density Polyethylene (HDPE)
Properties & Application:
With the highest service temperature set at 100°C, HDPE could withstands boiling sterilization. Also, HDPE exhibits superior toughness, whose mechanical strength exceeds LDPE. These properties drive its adoption in critical medical devices including artificial lungs, tracheal implants, laryngeal prostheses, renal dialysis components, urethral stents, orthopedic bone substitutes and disposal surgical instruments.
Processing Details & Suggestions
In some cases, at the aim of enhancing toughness, LLDPE material with better toughness is introduced as carrier resin, after filling it with HDPE, the mixed compound shows better viscosity but worse liquidity. Oleic amide, which is a FDA certificated lubrication, can be introduced for significant improvement in liquidity.
3. Ultra High Molecular Weight Polyethylene (UHMWPE)
Properties & Application:
Aside from common properties of PE material, UHMWPE shows a variety of advantages, including strong wearability, low friction properties & creep deformation level, decent resistance against chemical, water and impact, good self-lubrication and stability against chemical supplies. What’s more, it’s non-toxic & non-odor, physiologically & biologically inert, whose resistance against chemical supplies could match that of Teflon. Given these, it makes a excellent material for artificial lungs, elbows or knuckle prostheses.
However, a wearing problem emerges for UHMWPE after a long time usage. Two primary wear modes were revealed, one generates lamellar debris (>50μm) and granular fragments capable of initiating foreign body reactions. While another mode produces smooth-wave fibrils and microfibrils with increased bioactivity. Also, clinical evidence from retrieval studies indicate that periprosthetic tissues consistently contain high-density UHMWPE debris. After isolation from implant interfaces, Spherical and elongated particles in micron sizes. These micron UHMWPE particles are the pathological consequences to a range of biological responses, which could lead to osteolysis or joints laxity.
Processing Details & Suggestions:
There’re two types of molding for UHMWPE, including extrusion molding or compression molding. However, in the research of the micro structure of UHMWPE, no particles or fragment were found in extracted material. Some consider that a directly compression molding with sterilization under anaerobic conditions could improve its performance.
Cross-linking process could increase UHMWPE’s mole weight further to reduce particles, Through wearing experiments for UHMWPE cross linking radiation or peroxide, researchers find out that crosslinking density remains a significant factor for wearing.
As a material implanted for human bodies, UHMWPE material must be sterilized before proceeding further. However, it will oxidized either sterilized by gamma rays radiation or by ethylene oxide. When sterilized by radiation, free radicals gonna emerge inside the material, which causes oxygen dioxide, decreasing your mole weight as well as mechanical performance. This oxygen dioxide could even adds to its wearing due to ageing.
4. Polypropylene(PP)
Properties & Application:
Medical devices demand highest among all products. As for polypropylene (PP) material., medical-grade PP must exhibit a variety of attributes, including high purity, non-toxic, non- irritant, chemically stable without degradation(available for ethylene oxide (EtO) sterilization). Its essential attributes also include comprehensive biocompatibility — specifically non-inflammatory, non-allergenic, non-carcinogenic, non-hemolytic, and non-thrombogenic properties.
Processing Details & Suggestions:
Conventional PP fails to meet these requirements, due to suboptimal transparency and aesthetics. Furthermore, due to problems like uneven dispersion of PP pellets and additives, or incompatible additive, material could suffer from a variety of defects, leads to compromised processability and aging resistance, yellowing tendencies, difficulties in balancing rigidity with toughness, as well as pronounced sensitivity to high-energy radiation sterilization. Consequently, modification technologies become necessities to improve these performances, including rapid quenching of PP films to suppress crystallinity; minimization of molecular orientation in cast films, and strict avoidance of nucleating agents in PP film formulations. Utilizing random copolymer polypropylene (RCP) technique, we can blend metallocene-catalyzed ethylene plastomers with propene, exhibiting enhanced non-embrittle ability after radiation, which is linked to the amount of plastomer inside. Additional performance metrics of PP films improve as the plastomer grow. enabling deployment in medical device packaging.
While biaxially oriented PP (BOPP) films demonstrate chemical stability and non-toxicity, their microporous structure permits biofluid permeation and lacks in biocompatibility, . Surface modification of PP microporous films with collagen shows a promise for clinical adoption. Alternatively, collagen/PP composite membranes achieve equivalent biocompatibility targets. Researchers validated that PP films grafted with N-isopropylacrylamide (NIPAAm) copolymers exhibit excellent cytocompatibility in vitro.
at 46% grafting density, or ternary NIPAAm/acrylic acid/RDGS systems at 65-143% grafting universally.
5. Fluor Plastics(Teflon)
Properties & Application:
PTFE (Teflon) offers strong advantages for medical uses – not only its high heat resistance, chemical stability (stands up to strong acids/bases and solvents), and a reduced friction level, but also the critical biocompatibility demanded in healthcare. Clinical studies show it is capable to work safely inside the body without bad reactions, handle sterilization in high temperature, performs well with blood contact. That’s why it’s widely applied for medical devices and implants. Among similar fluoroplastic variation, F40 (ethylene/tetrafluoroethylene copolymer) and F46 (FEP) are the top choices for medical devices.
Even though it doesn’t naturally prevent blood clots, PTFE (Teflon) has a unique ability to become antithrombotic. When contacted with blood, its surface quickly forms a stable coating that stops clots from forming. This coating guides the body’s own cells to cover the material smoothly, turning a synthetic plastic into something your bloodstream accepts naturally.
Processing Details & Suggestions:
When making medical ePTFE products through stretching, both high molecule weight(>106g/mol) and high crystallinity(>98%), as well as a non-toxic additive with high wettability are all demanded. The stretched ePTFE creates a flexible web of tiny fibers full of microscopic. Additives must soak in evenly, like a super-fine sponge. This porous structure makes implants soft, strong, and easy for surgeons to cut cleanly without fraying. This structure could even allow your body’s cells to grow through it, together they securely locked the implant into surrounding tissue.
Since we are in control of the pore size during manufacturing, no blood-leaking would happen for these implants, freeing you of any pre-clotting step. Earlier version of ePTFE blood vessels may bulged or ruptured sometimes, due to a lack of reinforcement, but it has been fixed in latest reinforced versions. Stretching PTFE is also capable to create a microporous material with 40-97% air pockets. This “expanded PTFE” combines a slick non-stick surface with toughness and crush resistance. That’s why it’s widely used in artificial hearts, lungs, voice boxes, and other critical implants
6. Conclusion
This post brings out details of four major medical-purpose plastics (PVC, PE, PP, and PTFE/Teflon), highlighting their properties, clinical applications, and critical processing insights.
PVC excels in electrical/chemical resistance, but requires non-toxic plasticizers (e.g., citric acid esters) and stabilizers (e.g., organotin) for biocompatibility.
PE variants (HDPE, UHMWPE) are capable to serve roles ranging from disposal instruments to implants, while UHMWPE demanding specialized techniques to mitigate wear debris.
PP material is demanded for a variety of standards including its specialized biocompatibility, while modifications like random copolymer (RCP) techniques are required to enhance performance.
Fluoroplastics (PTFE/FEP) excel in biocompatibility, introducing unique antithrombogenic surfaces, while ePTFE’s controlled porosity enables tissue integration.
For more detailed and tailored medical plastic solutions, KingStar is always willing to help. We’re dedicated to provide practical experiences and insights from our professional team, as well as efficient and decent customized plastic molding service.
