Hydrogenated styrenic block copolymers (HSBCs) consists of styrene based hard blocks and a hydrogenated diene soft block. HSBCs exhibit rubber elasticity since the hard block acts as a crosslinking point below the glass transition temperature of polystyrene and soft block provides elasticity. Hydrogenation provides heat and weather resistance. Major applications of HSBCs are thermoplastic compounds, adhesives and polymer modification. Thermoplastic compounds are used for automotive, consumer products widely replacing vulcanized rubber and PVC as a soft molding material. Hot melt adhesives consisting of HSBCs are used for diaper, sanitary napkin and tape. They are added to polymers as impact modifier or compatibilizer.
The market of advanced TPE is driven by outstanding aesthetics, high durability and processability to improve design flexibility. Based on these three key market trends, Kuraray introduced a new Series of HSBC by the name of Septon Q Series. The product is synthesized by the companies new polymerization and hydrogenation technology. A separate step is the new Alloy Technology. This novel process improves specially the elasticity and high temperature performance.
HSBC for High Durable Films
Overall, characteristics can be summarized as excellent durability (e.g. weatherability and abrasion), outstanding elasticity and polarity to Polyolefins. For the end applications, mechanical performances of Septon Q series include of good stretch and abrasion resistance and high pinhole strength. These characteristics are a result of its high elasticity. The series include of 2 components – soft and hard block – with separate glass transition temperatures. In this case, the hard block glass transition temperature is above, and the soft block glass transition temperature is below this use temperature. The result is the soft-elasticity that comes close to thermo set rubbers.
The compound shows a 15?% lower density compared to TPU. In this composition, lower PMMA contents can further reduce this density. This is one reason that TPU was substituted in highly advanced – low weight – sport shoes. The HSBC shows compatibility with PMMA as fine dispersed alloy. 2?% Haze at 500 µm is lowest value in this study.
In this paper, we defined durable performance as Pinhole Strength, Erichsen Scatch, Abrasion Resistance, and weatherability. Within this characteristics, the Septon Q series shows the best overall performances. Specially the mechanical based Pinhole, Scratch and Abrasion results are close to those values of TPU. On top, the compound shows the best light stability in Xenon Test after 960 h exposure time. As a result, considering of general and durable properties, the new polymer shows almost high competitiveness to other advanced technical TPEs like TPU, TPE-A and TPE-E. At the same time, it shows as good compatibility with Polyolefins. Benefit: highly functional areas -value added areas – can be made from the polymer series , passive, non-function areas can be made from Polyolefins. In other applications than film this benefit is already know and used.
In general HSBCs performs in high elasticity‘s that are close to thermoset rubbers. The new polymer shows excellent elasticity with significant reduced hysteresis set. TPU (58?% Set) shows 60% worse 1st cycle sets than Septon Q series (21% Set). Another benefit is the temperature dependency. HSBC include of Soft-Block with one of the lowest Glass Transition Temperature in the field of Thermoplastic Elastomers. Therefore, the benefit of Softness and Elasticity still maintains in the lower temperatures. And also, at higher temperatures, the product still has high performance. The polymer shows higher mechanical strength (herein mechanical loss factor) compared to TPU. In the result, the new series stays quite constant over a wide temperature range. It shows both, better low temperature performance (no stiffening) and better high temperature performance (no softening).
Processing Conditions and Morphology
Septon Q 1250 (50?%) can be pre mixed and compounded with PMMA (50%) (PARAPET GH1000S). The production of the films requires a defined setup and processing setting . The films of each material, TPU, TPE-A, TPE-E and Septon Q series were produced on a small scale Mono Cast Film Line. The new series should build the matrix with a fine dispersed PMMA phase. This requires a combination of 100-150 micron screen mesh and a static mixer. Temperature profile is increased from 200 (Mixing Zone) to 230?°C (Die Head). A touch roller was used to achieve better line stability and superior surfaces. Temperatures of the cast and touch roller was set at 80?°C to maintain sufficient cooling and solidification. Line pressure is set at 350 N/cm. Higher pressures increases the film transparency. However, touch roller processing does not mean conventional calendaring (homogenization). The purpose of the touch roller is of smoothing the surface.
Different morphologies of the new polymer investigated by Statistical Parametric Mapping (SPM) are shown. The figure illustrates the dependency to the mechanics and transparency. The picture shows the target morphology with a fine dispersed matrix/domain of Septon Q/PMMA. This films shows a high elasticity and clearness. On the other side, the PMMA domain is lose or uneven and inconsistent. This films are rigid and hazy.
High Performance TPE for Technical Film Applications
Greatest advantage of the new polymer based Film is the excellent combination of elastic and durable performance and the compatibility to Polyolefins. Thanks to this, Septon Q series is adding value compared to advanced TPEs. The possibility for material combinations with Polyolefnis opens up new markets opportunities. Intended applications are TPU-Film substitutions, laminated/multi-layer films and foamed films.
Styrol-blockcopolymere für Film-Anwendungen
Septon Q basiert auf einem neuem HSBC (hydriertes Styrol-Blockcopolymer) mit guten Alterungsbeständigkeiten. Diese werden hierbei durch folgende technische Eigenschaften definiert: Druckverformungsrest (DFR), Temperaturbeständigkeit und Witterungs-beständigkeit. Das Produkt – synthetisiert durch eine neue Polymerisationstechnologie – ist verträglich mit Polyolefinen und PMMA. Das Polymer ermöglicht somit komplett neue Polymerkombinationen. Hierdurch wird nicht nur das Eigenschaftsprofil verbessert sondern die Profitabilität über die gesamte Wertschöpfungskette gesteigert. Kuraray produziert SBCs (Styrol-Blockcopolymere) die unter den Markennamen Septon und Hybrar vertrieben werden. Die Anwendungen dieser Elastomere sind vielseitig und unter anderem in den Bereichen Soft-Compounds, Polymer Modifikationen, Klebstoffe, flexibler PVC Ersatz und Vibrationsdämpfungen zu finden.
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