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Cyclic olefin copolymer (COC) is a unique member of the polyolefin family, which also includes high-volume materials such as polyethylene (PE) and polypropylene (PP). It was introduced decades ago and has now become a widely used material in medical and packaging applications. The extremely high purity and unique properties of COC make it the main material in advanced diagnostics and microfluidic applications. The use of this material in primary drug packaging—in the form of prefilled syringes, vials, blisters, sachets, and light-weight wearable devices—is becoming more and more common, as new drug molecules and formulations tend to be less pure. Plastic and glass are more chemically sensitive. PE and PP films use COC as a performance enhancer to simplify the film and compete with more complex, less recyclable structures.
Part of the appeal of COC is its glass-like transparency, which matches or surpasses traditional glass alternatives such as polycarbonate (PC) and polymethyl methacrylate (PMMA). Importantly, for medical use, COC can be sterilized by all standard methods, including steam, EtO, gamma, and hydrogen peroxide. It has the best UV transmittance of any polymer, which is essential for many diagnostic analyses. It can provide heat resistance up to 170°C and can easily withstand polymerase chain reaction (PCR) and steam sterilization conditions. Another powerful advantage of COC is its resistance to corrosive polar chemicals. It is highly resistant to acids, alkalis, alcohols, etc. The resin also provides one of the best moisture barriers for any plastic.
The advantages of COC in medical design are compelling. The resin is capable of reproducing incredibly fine details through injection molding, even at the sub-micron level. It also has excellent dimensional stability and low shrinkage, and can achieve volume accuracy that most competitive resins cannot match.
Perhaps the main attraction of COC is its extremely high purity and inertness. Its low extractables and extractables make it ideal for direct contact with drugs, while few ions can maintain the potency of sensitive formulations. It is widely used in the most challenging drug delivery and packaging applications, where even medical glass cannot be used. In diagnostics and microfluidics applications, the same characteristics can ensure that the material being analyzed or processed is not contaminated, thereby maximizing analysis accuracy and product purity. As one might expect, compliance is a major advantage of COC, meeting USP level VI and ISO 10993 compliance, including biocompatibility, USP 661.1, and FDA drug and device master files.
The COVID-19 pandemic has sparked interest in COCs for diagnostic disposables as well as vaccine and therapeutic packaging. COC has long been a material solution for medical syringes and vials and disposable diagnostic containers. These markets have been dominated by borosilicate glass.
COC is being used in COVID-19 testing applications, and its use in new vaccines and therapies is being developed. Considering a series of new tests and treatments, the company is developing with the purest and most inert products. As the pharmaceutical industry is increasingly concerned about the shortage of COVID-19 vaccine glass bottles, interest in COC has further increased.
COC can be used to alleviate a potential shortage of borosilicate glass used to make vaccine vials. Although cheap borosilicate glass meets today's industry needs, there are still some emerging drugs and therapies that are incompatible with glass. In particular, with the emergence of more biotechnology-derived active ingredients, COC can play an important role.
The material's extremely low leachables and extractables, as well as its non-polar, low-reactive surface, and extensive global regulatory compliance make it an ideal choice for diagnostic disposables and packaging for vaccines and therapeutics. COC is currently commercialized in many medical applications of the world's leading healthcare companies. The material has ultra-high purity and its inert nature prevents interference with reactions and analysis. Other key features include excellent optical properties (91% transparency) as well as excellent UV transparency and low birefringence.
As the advantages of COC become more and more widely known, and as the supply continues to increase, the market for COC in the medical field is growing strongly. The pre-filled syringe is a remarkable success story, based on the excellent purity provided by the COC syringe and the resulting drug stability. Another booming application is wearable insulin delivery devices, where the purity and dimensional stability of COC can achieve high efficiency and precise drug control.
Various devices use COC to improve chemical resistance. Among them, bone cement mixer is a specialty, and the number of medical devices that use COC to improve the performance of PE and PP through blending so as to replace more expensive polymers has surged. In terms of diagnosis, COC disposable products for disease testing are becoming more and more popular. When more precise analysis is required, it largely replaces PP and polystyrene (PS).
Over the years, microfluidic applications have developed and benefited from a number of innovations. The use of the new design has expanded from simple microanalysis performed in the laboratory to the rapidly growing field of point-of-care (POC) diagnostics. With these advances, the choice of materials used to make biochips, ink cartridges, and other microfluidic components is also evolving. Glass and polymers (such as silica gel) have been mainstream for many years. Recently, cyclic olefin copolymer has become a very useful and attractive microfluidic material with high optical and ultraviolet transparency, low water absorption, excellent moisture resistance and excellent chemical resistance, including the main materials used in chemical analysis Organic solvents.
The unique properties of COC make it an excellent material for the design and manufacture of microfluidic components used in analytical systems, research and biomedical equipment. COC can be used to replicate functions including microchannels, such as hot embossing for low and medium production volumes, and injection molding to produce large numbers of detailed parts faster.
It has been found that cyclic olefin copolymers have increased utility as performance enhancers in polyolefin-based film packaging. In polyolefin blends, COC provides a major performance upgrade, providing higher modulus, greater heat resistance, and higher barrier properties for thermoformed products such as trays, bags, and pouches. These blends are easily processed on traditional casting and blown film processing equipment in accordance with the standard operating parameters of polyolefins.
COC is based on the use of metallocene catalysts to polymerize ethylene and norbornene. The glass transition temperature (Tg) of this material ranges from 65o to 180o C, as a function of the comonomer ratio. As an amorphous polymer, COC does not have a crystalline melting point, but starts to soften above Tg and becomes more and more fluid as the temperature rises. This colorless, crystal clear material has a high modulus and is highly compatible with traditional polyethylene grades. It has the best compatibility with linear polyethylene products such as LLDPE and HDPE, and is acceptable for LDPE. For many years, processors have reprocessed COC/PE scraps and scraps directly back into production. Recognizing the increasing importance of recyclability, recent tests have shown that COC is compatible with PE and PP post-consumer recycling streams in Europe and container PE in the United States. More tests are underway, including the latest US PE film agreement.
As a blending component, COC is most commonly used to increase the modulus and reduce the thickness of single-layer films. The modulus is in the range of 300,000 psi, and the addition of as low as 10% COC to LLDPE will double or triple its modulus while maintaining low haze levels. In simple single-layer films or as part of co-extruded films, LLDPE/COC blends generally allow thinner films to provide the same performance at a lower area cost, thereby providing important sustainability advantages.
When a higher Tg grade COC is used, these modulus improvements remain constant at temperatures close to the Tg of the COC, thereby improving hot filling performance and increasing temperature capability. Another important point is that adding COC to LLDPE can significantly reduce the Elmendorf tear value, especially in the longitudinal direction, even if it improves the puncture resistance of the film. COC is used commercially as a controlled linear tear additive. In addition, many olefin/COC films are commercially used for thermoforming applications, where the amorphous nature of COC improves the uniformity of the molding process, thereby improving the thickness control of deep drawn (>10 cm) sections and corners.
Cyclic olefin copolymers can also achieve higher performance in multilayer polyolefin packaging films and are suitable for many applications. On the basis of comparable costs, COC/LLDPE multilayer films have higher moldability, optical properties, toughness and puncture resistance than similar EVA/ionomer co-extruded films. The engineered COC/LLDPE multilayer film is also comparable to many nylon-based structures without the need for an adhesive tie layer. Due to the compatibility between COC and polyethylene, removing the tie layer and non-olefin resins can simplify production logistics and allow the use of recycled waste film.
COC is also increasingly used to produce high-transparency barrier films for packaging. COC has moisture resistance and is four to five times better than LDPE. Blends composed of more than 70% COC usually provide up to 90% of the barrier properties of pure COC, and are different from HDPE—maintain low haze. Although COC as a blending component can enhance barrier performance, when COC is used in discrete layers, the best barrier improvement is achieved. COC also generally provides aroma and aroma barrier properties that are 5 to 10 times higher than that of LLDPE. Although COC does not provide high gas barrier properties, its performance is still significantly better than polyethylene, and can be used to customize permeation to meet the specific oxygen, nitrogen, and carbon dioxide barrier properties required by packaging.
COC applications are often located in areas where traditional materials cannot meet one or more performance requirements. Although PC is widely used in medical applications and provides better impact performance and ductility than COC, it sometimes fails to meet the purity or thermal requirements of medical applications. On the other hand, the impact performance of PMMA is similar to COC, but the heat resistance of acrylic is obviously inferior to COC. In the field of polyolefins, COC seldom competes with cheap PE and PP, but it is usually combined with these materials (through blending or multilayering) to enhance such materials as heat resistance and chemical resistance, dimensional stability, barrier properties, and heat resistance. Moldability and other characteristics. One area where COC is restricted is contact with fats, oils and fuels. These non-polar materials may penetrate the COC and damage the surface.
Unlike other polyolefins, COC is an amorphous polymer. This gives it processing characteristics similar to widely used medical resins such as PC and PMMA. It can be injection molded and can also be used to extrude medical film products such as blister packs and barrier bags. Many leading medical injection molders have sufficient experience with COC, as do many top film manufacturers.
COC is another chemical cousin of amorphous polyolefin, called COP (Cyclic Olefin Polymer). This resin has many high-performance properties with COC and is used in many of the same applications, each with smaller advantages in certain performance categories. However, COP is manufactured through a more complex process than COC, which usually makes COC a more cost-effective option.
COC is an important supplement to the medical and packaging materials library. It can achieve better drug stability and unparalleled disease diagnosis capabilities, while improving the performance and recyclability of the plastic film. Strong growth is expected to continue as this material meets complex performance requirements and supports many growth trends in the medical industry, including drug complexity, instant testing and wearable devices. The demand for efficient and sustainable packaging will continue to drive the growth of the packaging market.
Timothy Kneale is the president of TOPAS Americas. Kneale is trained as a chemical engineer and has held a variety of product development and technical leadership positions in the plastics industry. Since 2008, he has been leading the TOPAS COC business in the Americas. Polyplastics Co., Ltd., through its subsidiary TOPAS Advanced Polymers GmbH, is the leading manufacturer of COC and is sold under the TOPAS brand. For more information, please visit topas.com or contact Kneale via [Email Protection]
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