A new family or acrylic block copolymers is said to be easily mixed into nanoscale dispersions with various thermoplastics, thermosets, and elastomers - and to be miscible with those matrix polymers. As a result, these nano-additives reportedly provide combinations of properties not achievable with traditional additives, including impact strength plus high rigidity and transparency. They are targeted for use as toughening agents as well as compatibilizers.
Developed by Arkema in France Nanostrength block copolymers currently are available in two versions, each made up of three blocks. One is an SBM copolymer of polystyrene, 1.4-polybutadiene, and syndiotactic PMMA. The other is a symmetric MAM copolymer of side blocks of PMMA surrounding a center block of poly (butyl acrylate).
The SBMs are polymerized with a new patented Arkema anionic technology that yields a highly syndiotactic structure for the PMMA block. Compared with regular PMMA, sPMMA reportedly has both a higher thermal stability and higher glass-transition temperature. The polar MMA and nanpolar styrene blocks are compatible with polymers such as epoxies, styrenics, PC, PPE, PVC, and PVDF.
Because of the repulsive interactions between the three dissimilar blocks, when SBMs are blended with a polymer compatible with one block, they "self-organize" into very small domains forming a nanostructure in certain thermoplastics, epoxies, and elastomers. Their polar nonpolar composition also suits them to act as interfacial agents for many incompatible polymers in new types of polymer blends, composites, and elastomers.
There are five available Nanostrength SBM grades. Use levels are 3% to 10%. Grades E20 and E40 are designed mainly for toughening epoxy thermosets used in composites, adhesives, and coatings. Grade A123 is best suited for impact modifying thermoplastics, including engineering resins like PPE, PC, and blends. A250 is said to be an excellent compatibilizer, while A012 is targeted for modification of elastomers.
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