ORIGINAL PAPER Effect of SBA-15 on the energy absorption characteristics of epoxy resin for blast mitigation applications P. K. Roy • A. V. Ullas • S. Chaudhary • V. Mangla • P. Sharma • D. Kumar • C. Rajagopal Received: 18 January 2013 / Accepted: 1 June 2013 / Published online: 4 July 2013 Ó Iran Polymer and Petrochemical Institute 2013 Abstract The energy absorption characteristics of silica- filled epoxy composites, for potential application as a blast mitigating retrofitting polymer coating has been explored. Mesoporous silica (SBA-15) with controlled pore size of 5.4 nm was synthesized by the hydrolysis of tetraethyl orthosilicate in the presence of amphiphilic copolymer (PEO-PPO-PEO) which was characterized by nitrogen physisorption studies at 77 K. The porous siliceous rods were homogeneously dispersed in the epoxy resin by ultrasonication (0.5–7 wt%) and subsequently cured using triethylene tetra-amine hardener to prepare silica reinforced composites. Structural, thermal and mechanical properties of the composites were evaluated under dynamic as well as quasi-static conditions which revealed that introduction of SBA-15 at low loadings (1 wt%) led to an increase in the toughness of the base resin but macroporous silica led to deterioration in the properties. The results clearly revealed that the mesoporous nature of silica plays a major role towards improving the dispersion of the filler which in turn resulted in improved properties. Neat epoxy samples fractured in a brittle fashion, but in the presence of SBA- 15, the sample exhibited ductile failure, which was explained on the basis of a crack pinning mechanism. High strain rate studies (*10 3 s -1 ) of selected compositions were performed on a Split Hopkinson pressure bar and the effect of addition of mesoporous silica on the energy absorption characteristics were established. Finite element analysis was used to predict the behavior of concrete slabs on exposure to dynamic loadings resulting from TNT explosions, both in the presence and absence of the epoxy layer, which revealed the role of the retrofit as a fragment arrestor. Keywords Epoxy  Mesoporous silica  Toughness  High strain rate testing Introduction In the wake of terrorist attacks, enormous attention has been directed towards development of materials which can be used for mitigation of primary and secondary blast effects. Such incidents usually take the form of small bombings and results in damage to the nearby structural elements leading to the generation of high energy frag- ments which are the real cause of injuries and fatalities. To prevent the same, suitable multifunctional polymers, which can be added as a retrofit layer on existing buildings, are the need of the hour. These retrofitting polymers should possess enough resilience and strength to deflect and hold back fragments in place, thereby providing requisite response time for the inhabitants to take suitable protective measures. Although steel panels are capable of providing the requisite level of protection, but in most cases, the existing structures are not designed to support the P. K. Roy (&)  S. Chaudhary  P. Sharma  C. Rajagopal Centre for Fire, Explosive and Environment Safety, DRDO, Delhi 110054, India e-mail: pk_roy2000@yahoo.com A. V. Ullas  S. Chaudhary  D. Kumar Department of Applied Chemistry and Polymer Technology, DTU, Delhi 110042, India V. Mangla Terminal Ballistics Research Laboratory, DRDO, Chandigarh 160030, India Iran Polymer and Petrochemical Institute 123 Iran Polym J (2013) 22:709–719 DOI 10.1007/s13726-013-0169-8