Nynas Tests Oils for TPE Applications

Nynas Tests Oils for TPE Thermoplastic elastomers (TPE), which successfully combine the properties of plastics and rubber, are used in everything from car dashboards to toothbrushes and shoe soles. Nynas researchers, in a recent study, demonstrated with evidence the high performance of the company's highly refined oils in TPE materials. Dr. Kamyar Alavi, Senior Specialist at Nynas, explained: "Thermoplastic elastomers possess properties sought in elastomeric materials such as tactile feel, damping and low-temperature characteristics. However, unlike conventional rubber materials that cannot be reshaped once vulcanized into a specific form, TPE materials retain the melt-processing properties of plastics, allowing them to be re-molded. This provides greater flexibility for both processing and recycling." TPE materials, found in numerous applications and in products we use every day, are compounds formulated by combining TPE polymer with other components such as polyolefin, fillers, antioxidant additives and process oils. Oil plays a vital role because it is not uncommon for oil loading to reach levels as high as the TPE base polymer. Kamyar Alavi stated, "Many TPE materials are used in high-end and light-colored applications, so the aging of products and color stability are of particular importance. When combined with high oil quantities, this means that the color stability of the oil is an important parameter for overall performance." Kamyar Alavi and his colleagues Tommie Ibert and Patrik Salomonsson recently conducted a comparative study to evaluate the performance of highly refined oils in TPE materials. The performance of Nynas' NYFLEX® 223 and NYPAR® 330 process oils and their performance-optimized (additivated) versions DP 223 and DP 330 were evaluated alongside commonly used paraffinic TPE process oils. Alavi noted, "Since most final products are exposed to light, one of our most important objectives in the project was to examine the effect of the oil on UV aging of the compound. For this purpose, we monitored changes in the compound's key properties as a function of UV exposure time." The results shown in Figure 1 indicate that aging occurs mostly in the early stages of exposure and reaches nearly the highest level after 168 hours. Compounds containing NYFLEX 223 performed at the same level as SN500 and SN600, the lowest paraffinic Group I oils. The improved naphthenic oil DP 223 showed significant improvement in color at nearly the same level as NYPAR 330 compounds, while DP 330 demonstrated performance nearly identical to paraffinic medical white oil (P-MWO). Figure 1. Color changes observed in TPE materials during UV exposure. Samples were exposed to UV radiation in a purpose-built test chamber and color differences were measured in an external industrial laboratory. • Structurally, TPEs consist of thermoplastic hard blocks connected by elastomeric middle blocks. One of the most important TPE materials is referred to as Styrenic Block Copolymers (SBC or TPS). The thermoplastic block used in these is made of polystyrene connected by elastomeric middle blocks such as butadiene or isoprene rubber. The role of the oil is to provide optimal plasticization of the rubbery phase without insufficient interaction with the hard (styrenic) phase.