Polyurethane can be classified as a polar polymer, which can form a self-assembled structure due to their strong interaction. Investigation of the degree of microphase separation of polyurethane blends using Fourier transform infrared spectroscopy, molecular design of reactive compatibilizer and blend system with polylactic acid were reviewed.

Various modifiers, such as elastomers, thermoplastic resins, inorganic fillers, etc., have been blended with epoxy resins in order to improve several functional properties. Even if the modifier type and addition amount were the same, the toughening effect depended on the combination with the epoxy and curing agent as the counter parts. In this review, the toughening technologies of the epoxy networked polymer blends were classified and discussed based on the toughening mechanisms. Toughening using elastomer blend highly depended on the plastic deformation capacity of the epoxy matrix. On the other hand, toughening using thermoplastic polymer blend depended on the physical properties of the polymeric modifiers, and on the phase structures. In the case of block copolymer blends, the toughening mechanism was close to elastomer blends. Several shapes of nanostructures of elastomeric phases in several tens of nanometer size were reported. The toughening effect depended on the types of nanostructures.

Thermosetting resins with benzoxazine rings in backbone forms network structure under heating more than 200 ℃ by itself. These were reported as a higher performance resin with various superior properties. However, the practical use was restrictive for reasons of high hardening temperature, generation of pyrolysis gas under thermal hardening condition and inferior flexibility. Recently, the reaction process was elucidated in detail, and several catalysts promoting hardening under moderate condition were developed. In this article, outline of benzoxazine-based polymer alloy for improvement of flexibility, mechanical property and heat resistance were summarized.

In this review, I will introduce recent researches on “in situ polymerization method” in which cured thermosetting resins are toughened by polymerizing modifier monomers dissolved in the resins in parallel with curing reaction of the thermosetting resins. The addition of the modifiers in the monomer state instead of the corresponding polymers reduces viscosity of the resins before curing to improve processability of the resin compositions. Compatibility between the uncured resins and modifier monomers is higher than that between the resins and polymers, and this higher compatibility is expected to fix the phase separations between the cured resins and in situ generated modifier polymers with finer structures, which leads to improved toughness of the cured resins. Various thermosetting resins including phenol-, anhydride- and amine-cured epoxy resins, cationically polymerized alicyclic epoxy resin, cyanate ester and benzoxazine resins are found to be effectively toughened by in situ generated modifier polymers such as poly(N-phenylmaleimide-co-styrene) with high glass transition temperature.

Polymer blend is defined as a compound of polymers with different function and charafenristics according to the dictionary of rubber technology. The combination of more than two kinds of polymer demonstrates the novel function and charafenristics. Polymer blend is classified into the crosslinking and the non-croosslinking system. This review is concerned with the polymer blend based on closslinking elastomers. (1) Purpose of the polymer blend, (2) Example of polymer blend developed previously, (3) Marketed polymer blend product with crosslinking system, (4) Actually used example of the polymer blend.