Zeon’s styrene-isoprene-styrene (SIS) block copolymer system allows heat-resistant, photo-cured crosslinking, serving to eliminate the tradeoffs between hot-melt SIS systems and solvent-based SIS rubber systems.
The cross-linkable SIS technology, referred to as “x-linked SIS” or “xSIS”, preserves the simple, low energy processibility, low VOC level, adhesive properties and mechanical properties of SIS, while improving heat resistance and durability
Key Features and Benefits
- Peel and tack performance suitable for adhesive applications
- Heat resistant to 120-150° C (depending on level of photocuring), as demonstrated by the shear adhesion failure temperature test; typical SIS materials heat resistant only to 80-100° C
- Can be prepared via low energy, low viscosity hot-melt processing
- Quicker, more efficient processing and production for adhesive applications compared to solvent-based systems
- Low VOC level, particularly compared to solvent-based SIS rubber systems
- Estimated processing cost savings, despite 10-20% higher raw material cost
How xSIS Compares
Cross-linkable SIS shows improved functionality over the typical SIS hot melt material. X-linked SIS exhibits the same holding power at room temperature as SIS, with better holding power than hot melt SIS and hot melt acrylic at high temperatures.
The yellow shaded area of the spider chart above highlights the main differentiating properties of the x-linked SIS technology compared to hot melt SIS and hot melt acrylic materials.
Technology Development Status
Zeon’s cross-linkable SIS materials are currently at the advanced product development stage. Zeon is seeking input from professionals in various markets on application requirements and fit.
About the Company
ZEON CORPORATION is a $3.3B, 3,300-person chemical company focused on specialty elastomers, polymers, and specialty chemicals founded in 1950. The company produces a variety of products including high nitrile rubber that can be used in strong cements and adhesives, acrylonitrile butadiene copolymer latex, resins, and other rubber additives.
The crosslinkable SIS material, “x-linked SIS”, is enabled by a specific star-shaped SIS molecular structure, and adhesive performance can be deliberately modified by varying the styrene content.
Zeon has developed two pre-commercial versions of this x-linked SIS: QTC SL-177 and QTC SL-209. In this document, Zeon’s standard hot melt SIS product, Quintac 3421, and a solvent-processed, high molecular weight (Mw = 106) SIS rubber adhesive compound (“market product”) are used as comparative benchmarks.
Zeon’s x-linked SIS formulation is the same as the formulation for standard hot melt SIS (Quintac 3421), except for the structure of the C5-type resin that is used.
The components of the x-linked SIS formulation used for adhesive testing include: SIS block copolymer, C5 type resin, naphthenic oil, cross-linking accelerator (TMPTA), photoinitiator (Irgacure 651), antioxidant (Irganox 1010/Irgafos 168) [Fig. 1]
Commercially, Zeon would supply the appropriate SIS and C5 resin components and the customer is to perform compounding and processing [Fig. 2].
Loop tack, peel adhesion, and shear adhesion failure temperature (SAFT) testing data, as provided by Zeon, is presented in Figure 3. X-linked SIS ((QTC SL-177 and SL-209) exhibit adhesive properties comparable to the solvent-based high molecular weight SIS rubber adhesive system (“market product”), and out-perform typical hot-melt SIS (QTC 3421) in most conditions.
In addition to improved heat resistance in terms of shear adhesion (SAFT test), storage modulus (G’, representing resistance to stretching/shearing) of x-linked SIS is preserved at high temperatures (120°C +) compared to typical SIS.
The x-linked SIS exhibits much lower viscosity than the solvent-based SIS rubber adhesive system over processing temp. ranges, prior to curing, making processing more efficient in terms of speed and energy requirement [Fig. 4]. Zeon’s x-linked SIS also shows attractive heat stability for hot-melt processing [Fig. 5].