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Block Copolymer-Based Hot-Melt Pressure-Sensitive Adhesives
| Content Provider | Scilit |
|---|---|
| Author | Hu, Yuhong Paul, Charles W. |
| Copyright Year | 2008 |
| Description | Book Name: Technology of Pressure-Sensitive Adhesives and Products |
| Abstract | Pressure-sensitive adhesives (PSAs) based on block copolymers have comprised an area of fast growth over the past 20 years (see also Chapter 8). The unique properties of this class of adhesives rely on the structure and morphology of block copolymers. Typical block copolymers have an A–B–A triblock structure, where A is a hard end-block that has a high glass transition temperature (T$ _{g}$), well above room temperature, and B is a soft, elastomeric mid-block with a T$ _{g}$ much lower than room temperature. The most common block copolymer type is styrenic block copolymers (SBC), such as styrene–isoprene–styrene (SIS) and styrene–butadiene-styrene (SBS). More recently, acrylic block copolymers (ABC) became commercially available. ABC expand the block copolymer technology to a wide range of PSA applications. For both styrenic and acrylic block copolymers, the hard A block and the soft B block have sufficiently different solubility parameters such that they are not thermodynamically compatible with each other. As a result, block copolymer-based adhesives have a unique microphase-separated morphology, where A blocks form a hard phase embedded in a soft, continuous phase composed of B blocks. The B mid-block phase provides viscoelastic properties and the A end-block phase serves as physical cross-linking domains to render cohesive strength at room temperature. The physical cross-linking mechanism is thermo-reversible. At temperatures 3-2that are high above the T$ _{g}$ of the end-block polymer, ordered structure disappears and the polymer turns into a viscous melt. Owing to the overall lower molecular weight, the melt viscosity is significantly lower than that of traditional rubbery polymers, such as natural rubber (NR), butyl rubber (BR), and nitrile rubber. The low melt viscosity makes it possible to process block copolymer-based adhesives in a solvent-free, hot-melt form. Besides block copolymers, tackifier resins, plasticizers, and antioxidants are also key ingredients in hot-melt PSAs (HMPSAs; see also Chapter 8). To achieve the best PSA performance, tackifier resins and plasticizers are preferably compatible with the mid-block phase, as schematically depicted in Figure 3.1. Figure 3.1 Schematic drawing of a microphase-separated block copolymer-based PSA. |
| Related Links | https://content.taylorfrancis.com/books/download?dac=C2007-0-01662-6&isbn=9780429145032&doi=10.1201/9781420059410-3&format=pdf |
| DOI | 10.1201/9781420059410-3 |
| Language | English |
| Publisher | Informa UK Limited |
| Publisher Date | 2008-11-10 |
| Access Restriction | Open |
| Subject Keyword | Book Name: Technology of Pressure-Sensitive Adhesives and Products Applied Chemistry See Also Chapter Block Copolymers Based Adhesives |
| Content Type | Text |
| Resource Type | Chapter |
