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TPE  

The right property for any application

Thermoplastic elastomers (TPE) are gaining ground, particularly in markets and for applications demanding compliance with a variety of regulations and specifications, but also when it comes to realizing efficient and feasible solutions. And TPE are also increasingly asserting themselves as substitute materials for rubber, silicone or PVC, not only on account of their property profile, but also by continually optimizing their mechanical, haptic, migration or even performance characteristics – as indicated by the following examples:

A low degree of migration is a key property for all materials and items coming into contact with food as they must not lead to a health hazard or an unacceptable change in the composition of food or a negative impact on its organoleptic properties. Unlike PVC-based materials containing phthalates or other plasticizers which can be released by fat or liquids, Actega DS offers innovative TPE materials certified for contact with food which do no not contain PVC or phthalates or any other plasticizers classified as questionable or insufficiently tested, and from which nothing migrates.

Testing is done with simulants (e.g. ethanol, olive oil, acetic acid). The PIM regulation defines which simulants are to be used for testing, depending on how and for what purpose the material from which substances could migrate will be used and/or on the food with which it probably will come into contact. For instance, the simulants ethanol 10 volume percent, ethanol 20 volume percent and acetic acid 3 weight percent are classified as foods with hydrophilic properties (e.g. milk, fresh or conserved fish, shellfish, meat and meat products etc). The simulants ethanol 50 volume percent and vegetable oil are classified as foods with lipophilic properties (alcoholic beverages with an alcohol content in excess of 20 volume percent, vegetables preserved in alcoholic media, fats, oils etc). For reusable items, the rule is that the migration test must be carried out three times on the same sample using a different portion of the food simulant each time. These tests apply for both packaging and a wide variety of products provided there is an exact definition of the food the product comes into contact with. This is not, however, entirely clear for some items, e.g. chopping boards, which come into contact with lots of types of food. This is covered by a regulation in accordance with EU 10/2011: “Materials intended to come into contact with all types of food are tested with food simulants A, B and D2”.

Solvent bondability is required for a range of technical medical applications in particular, e.g. for tubes, drip chambers or tracheal cannulas. Micro-tubes of tracheal cannulas are often inserted through the neck flange, e.g. in the case of transporting air to the cuff (inflatable sleeve at the lower end of the endotracheal tube or a tracheostomy tube for sealing the space between the tube and the tracheal wall) or for optional secretion removal, whereby the micro-tubes need to be bonded to the outer tubes. In the case of drip chambers, the aim is to achieve an optimal connection with the tube. This entails the use of conventional solvents such as tetrahydrofuran (THF), methyl ethylketone (MEK), and even cyclohexanone and other solvents. An extensive series of tests with these solvents underlines the outstanding solvent bondability of the specially-developed PROVAMED® formulations. These TPE are also distinguished by a balanced degree of flexibility and rigidity. They can be sterilized between the drip chamber and tube without impairing their material properties or the effectiveness of adhesives, and display perfect adhesion, particularly to polystyrene, ABS and PVC.

A high degree of transparency can be of decisive significance, especially in the medical sector. In the case of drip chambers, for example, the aim is to regulate the dripping process and to be able to adjust the fluid level both swiftly and easily. But transparency is also required in medical tube systems to ensure that liquid contents remain visible and to permit optical flow control. Whether dosing tubes for inhalers, non-buckling tubes for IV sets or coextruded breathing tubes – the more manifold the types of tubes available, the more extensive the areas of application, and the more detailed the requirements. Therefore, the material bond applied needs to be finely developed and of maximum quality. Single-lumen tubes and mono-layers are suitable e.g. for transporting liquids and medication, they are used for infusions, enteral and parenteral feeding, in urology and endoscopy. Multi-lumen or multi-chamber tubes are are used in acute dialysis, as central-venous catheters, in urology and as liquor drainage. The areas of application of multi-layer tubes here include infusion lines and filling tubes for bag systems, pressure lines for angiography, administration of medication in oncology and highly-flexible working channels with low sliding friction coefficients in endoscopy. And then there are tubes which are reinforced for use as respiration tubes. As a general rule, the following requirements need to be fulfilled: Interactions between tube material and pharmaceutical substances or those produced naturally by the body must be prevented. There must be no interaction with the plastic, medication absorption must be avoided, the material must be entirely resistant to media. An important aspect is represented by material bio-compatibility ISO 10993, sterilizability with the usual procedures and buckling resistance.

Transparency is not only a key feature in many technical medical applications – it is also an important requirement for pacifiers, drinking cups and drink nozzles, to name but a few. For one thing, this is due to the possibility of control ensuring easy detection of any contamination or dirt. On the other hand, many parents want transparent TPE to look like silicone. It would appear that this criterion is very important for this customer base.

Why continually optimized and customized TPE are suitable for all these applications.