Medical accessories are made of thermoplastic elastomer TPE
Time：2019-07-25Hits：2563
In fact, TPE has created many successful cases in its unremitting efforts to replace silica gel, such as handicraft bracelets made of original silica gel, sex toys, rubber bands, etc. In recent years, TPE has announced its success in sharing the market cake with silica gel. However, any material has its advantages and disadvantages. TPE, which is environment-friendly, nontoxic, soft to the touch, and easy to form and process, is not a complete substitute for silica gel-take the road of silica gel, leaving silica gel with no way out!
TPE also has its short board, which also makes it suitable for some industries and fields instead of silica gel. Whether TPE can replace silica gel needs to consider the relevant requirements of material application. Below, technicians from TPE manufacturers in Shenzhen, based on their 8-year experience in TPE industry, will explain to readers the five main aspects that need to be paid attention to when TPE replaces silica gel:
I. Medical Device Industry:
The industry has high requirements for material safety because it is related to human health and safety. Silica gel is chemically inert, acid and alkali resistant and solvent resistant, and is an environmentally friendly material in line with the medical industry. However, for thermoplastic elastomer TPE to replace silica gel and be applied in the medical industry, it needs careful evaluation.
If the medical device is only in contact with the skin on the human body surface or the device is only in contact with gas, it is no problem to replace silica gel with environmentally friendly high-performance TPE. TPE also meets the skin irritation test of ISO10993.GB16886 for biocompatibility test, etc. However, if contact with drugs (especially liquid drugs such as infusion tubes) or in vivo contact is required, colony test and cytotoxicity test are usually required. Generally TPE is difficult to meet the relevant requirements for such medical devices as respirator covers and infusion sets. If special customized high-performance TPE is adopted, it is also possible to pass relevant tests. However, due to the related risks, the vast majority of domestic TPE manufacturers dare not try it easily, so at present this kind of medical devices are still mainly made of silica gel materials. However, it is said that very few imported TPE materials can meet the requirements of human body or liquid medicine contact in the medical industry.
II. Food Contact Materials
Some soft rubber utensils that need to contact or contain food, such as coasters, baby bottle nipples, sealing covers for preservation boxes, folding bowls, etc., usually use silica gel as raw materials. However, the use of TPE as a raw material has become a trend in recent years, and the demand for food-grade TPE materials has not decreased. But in the food contact products industry, TPE instead of silica gel is not going well either. For food contact materials, silica gel and TPE are applicable to corresponding test standards for different countries or regions. For example, the EU region is generally EU1935/2004 (the specific test items are respectively water, 3% acetic acid and 50% ethanol to carry out residue dissolution test on samples) and food utensils exported to Germany, in addition to the items specified in EU1035/2004, olive oil dissolution test (i.e LFGB test) is also required; China's national standard GB4806.1 requires tests on distilled water and n-hexane. The FDA standard of the United States is 21CFR177.2600, and the test content is consistent with the national standard of China.
In general, for food contact materials TPE, silica gel test standards, water contact equipment, distilled water residue test; Containers and appliances that come into contact with beverages should be tested for alcoholic acid such as ethanol or acetic acid, while appliances that come into contact with grease should be tested for dissolution of oily solvents such as olive oil or n-hexane. The test standards of different countries or regions are similar.
Now let's analyze the feasibility of TPE and silica gel dissolution test by water, alcoholic acid and oily solvent.
At present, silica gel can pass the dissolution tests of water, alcoholic acid and oily solvent, i.e. comply with FDA of the United States, GB4806.1 of China, LFGB of Germany and EU standards of the European Union, etc.
For TPE, as TPE is a blended material, specific analysis is required to pass the corresponding tests.
1. Basically all TPE meets the distilled water dissolution test
No matter what base material is TPE blended or polymerized with monomer, it can be said that TPE meets the distilled water dissolution test as long as impurities from unclear sources are not added.
2. Having passed the tests of alcohol and acetic acid, the TPE formula should be emphasized.
But all TPE can pass the alcohol acid test. The author suggests that the formula contains no or little operating oil and no ethylene-vinyl acetate components. TPE still has a good chance of passing the alcohol acid test. There is little problem in passing the EU1935/2004 test accordingly.
3. Tested with olive oil, n-hexane and other oily solvents
This is the weakness of TPE and the problem node where the substitution of food contact material TPE for silica gel is limited. At present, most TPE, such as SBS,SEBS base materials, PP/EPDM base materials, polyurethane base materials, etc., have passed the tests of SGS and other authoritative third-party organizations, and basically cannot pass the tests of olive oil and n-hexane. Some people in the industry revealed that although it is very difficult for TPE to pass the tests of olive oil and n-hexane, the chances of passing olive oil are relatively greater than n-hexane.
At present, it has not been proved that other substrates TPE (such as TPEE,TPAE) cannot pass the tests of olive oil and n-hexane, but considering various requirements, for food utensils that need to contact with grease and need to be tested with oily solvents such as olive oil and n-hexane, the author suggests that silica gel is the best material instead of TPE.
III. Requirements for High Temperature Resistance
For products with high temperature resistance requirements, TPE is used instead of silica gel, and special TPE materials need to be customized.
General TPE based on SEBS and SBS substrates can only reach 75~90℃ in high temperature resistance. The high temperature resistance of silica gel can reach 250℃. Some silica gel products require high temperature resistance (e.g. 120~150℃). If SEBS conventional TPE is used, it is difficult to meet the requirements. At present, the special TSI-HT series TPE elastomer developed by China Plastics King can withstand temperatures above 120 degrees. This provides more choices for users who have higher requirements for temperature tolerance.
IV. Resilience Requirements
For products with strict resilience requirements, if TPE is used, it is necessary to consider whether TPE can meet the product requirements. In terms of molecular chain structure, silica gel has excellent stretch resilience and its rebound rate is 100% due to its cross-linked three-dimensional network structure. The thermoplastic TPE material has a linear two-dimensional structure. Its resilience is inferior to silica gel. The vast majority of TPE, under the continuous action of external force, remain in a stretched state. After removing the external force, it is difficult for TPE to have 100% rebound, with stress relaxation or tensile deformation. The TEA-SP series of high resilience TPE materials of China Plastics has high tensile modulus and strength and excellent tensile resilience, providing a brand-new non-crosslinked material solution for high resilience products to replace silica gel and rubber. At present, TEA-SP series materials have been mature and applied to medical tourniquets, yoga fitness tension belts and other products.
V. tactility requirements
In terms of hardness, TPE and silica gel can adjust different hardness. However, the silicone material has a smooth touch, and the TPE usually does not reach the touch. Some TPE surfaces even have some sticky discomfort. Special TPE materials with silica gel touch can be developed by making customized adjustment to TPE blending system. At present, the TP-EN series of special materials for intelligent bracelets of China Plastic King have a smooth touch like silicone.
In short, TPE is good, but whether it can replace silica gel depends on the requirements of all aspects of the materials.
德创化工 (edit：dechuang)
