A novel renewable based benzoxazine, 3‐(furan‐2‐ylmethyl)−8‐methoxy‐3,4‐dihydro‐2H‐1,3‐benzoxazine‐6‐formyl (Va‐Bz), has been synthesized from a lignin derived chemical “vanillin” without solvents. Poly (Va‐Bz) has high Tg and excellent thermal and adhesive properties. A mechanism of cross‐linking, due to electrophilic substitution at furan and decarboxylation of carboxylic group of benzene ring, is suggested. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 7–11

We have developed novel di-, tri-, and tetrafunctional benzoxazine monomers (BZ2, BZ3, and BZ4), solely containing benzoxazine moieties arranged one after the other on the backbone, to discover the role of additional oxazine moiety on thermal properties. A tandem reaction was adapted, at first a ring-closure and then subsequent Mannich condensation by reacting 2-((4-hydroxy­phenyl)­amino­methyl)­phenol (HPAMP) and aniline/4-amino-2-((phenyl­amino)­methyl)­phenol/4-amino-2-(((4-hydroxy-3-((phenyl­amino)­methyl)­phenyl)­amino)­methyl)­phenol in the presence of paraformaldehyde to obtain BZ2/BZ3/BZ4. Tetrafunctional benzoxazine monomers containing an intermediate group (R-BZ4) were also synthesized by reacting HPAMP and p-phenylene­diamine/4,4′-diamino­diphenylmethane (PDA/DDM) to understand the differences in thermal properties due to the distance created by those between two benzoxazine moieties. The observations (in DSC and TGA analysis) with increase in number of oxazine rings include (i) reduction in curing temperature from 264 °C (BZ1) to 237 °C (BZ4), however an intermediate distance between BZ4 increased curing temperature to 245 °C (DDM); (ii) slower curing rate, a complete curing was achieved only by heating above 200 °C; (iii) decreased weight loss during ring-opening polymerization, BZ1:90% to BZ4:2.4%; (iv) increase in T g up to 315 °C; and (v) similar thermal stability for BZ2 to BZ4. Introduction of an intermediate between two oxazine rings in a tetrafunctional benzoxazine (R-BZ4) was found to be the best strategy to obviate weight loss during curing as well as to enhance the thermal degradation temperature of resulting polybenzoxazine (PDDM: T d10 of 395 °C).

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Extensive experimental and computational studies have been carried out on survivability of buildings, vehicles, combat helmets etc exposed to various high‐velocity projectiles such as explosives, bullets, sharpenal etc. Such explosive attacks have necessitated the development of protective techniques for mitigation of blast. Retrofitting the above mentioned structures with light weight materials such as fibrous composites, coatings or both seems to be of foremost importance. The present review focuses mainly on experimental techniques reported in last 15 years for blast mitigation. The topics covered include introduction, applications and properties of FRP coatings, types of explosives and other details of charge, testing procedures and performance evaluation of protected structures. Proposed mechanism for improvement in blast mitigation of protected structures has also been discussed. POLYM. COMPOS., 39:1389–1402, 2018. © 2016 Society of Plastics Engineers