Rainer Schönfeld

Renewable resource-based epoxy resins derived from multifunctional poly(4-hydroxybenzoates)

Herein we report on the preparation and cure of epoxy resins derived from renewable resources such as 4-hydroxybenzoic acid, glycerol, pentaerythritol, dipentaerythritol, trimethylolpropane, and sorbitol, aiming at substituting bisphenol A-based epoxy resins. Subsequent to the catalytic transesterification of polyols with ethyl-4-hydroxybenzoate, derived from bioethanol and 4-hydroxybenzoic acid, the resulting poly(4-hydroxybenzoate) phenolic resins (PHB-phenol) are glycidized with epichlorohydrin, obtained from glycerol. The epoxy functionality of these liquid ester-functional epoxy resins (PHB-epoxy) varies between 2 and 5. The PHB epoxy viscosities decrease with increasing epoxy functionality. In dicyandiamide-mediated thermal cure, property profiles similar to that of bisphenol A-based epoxy resins are obtained. The monofunctional glycidyl ether of ethyl-4-hydroxybenzoate (EHB-epoxy), formed as a by-product when PHB-phenol is not purified, can remain in the PHB-epoxy resins, serving as a reactive diluent. The incorporation of ester-functional epoxy resins does not impair the water-resistance of epoxy resins. Contrary to the flexible epoxy resins based upon epoxidized plant oils and glycidyl derivatives of glycerol, sugars, and polyfunctional fatty acids, the glycidyl ethers of the corresponding poly(4-hydroxybenzoates) and most especially their blends with conventional bisphenol A-based epoxy resins afford much higher stiffness, strength and glass temperatures, thus meeting the demands for applications as components of structural adhesives.

Benzoxazines for Industrial Applications Comparison with Other Resins, Formulation and Toughening Know-How, and Water-Based Dispersion Technology

Publisher Summary The promising family of benzoxazines is developed by academia and industry as a new type of phenolic resins, which can potentially open up new applications and product opportunities. Due to the molecular design flexibility of benzoxazines, certain desired properties can be tailored. For most customers or end-users the underlying chemical structures or physical principles are only of secondary importance. Due to the advantages of benzoxazines, it is expected that the use of benzoxazines will grow significantly in the future and become an important part in general industry. The synthesis of benzoxazines can be performed with or without solvents. The industrial application of benzoxazine resins, these oligomers often prove to be beneficial in several ways. In this chapter the general properties of benzoxazines with various other thermosetting materials like standard phenolic resins, BMI, and epoxides are compared. All its aspects are described with an emphasis on the methodology of research activities. Special focus is laid on the toughening additives. The chapter explains efforts to extent the area of benzoxazine research to the field of water-based dispersions. Polymerizable nonionic benzoxazine surfactants and two different types of polymerizable benzoxazine based protective colloids are developed that can effectively stabilize different benzoxazine-based formulations as small droplets in water. The described benzoxazine containing surface-active stabilizers have the strong advantage that they can seamlessly copolymerize and become an integral part of a polybenzoxazine network upon curing.