Hamid Shaikh

Developments in Shape Memory Polymeric Materials

Shape memory polymers (SMPs) are the class of self-repairing and intelligent materials that have received significant attention from both industry and academia. SMP materials are attractive substitutes to metals because of their flexibility, bio-compatibility, low cost, easy manufacturing and programming together with wide scope of modifications. SMPs have wide spectrum of possible applications in the fields of high performance textiles, self-repairing plastic components in vehicles, biomedical devices, etc. The present review mainly highlights the recent progress in synthesis, characterization, evaluation, proposed applications and future outlook of SMPs and related composites.

Progress in Carbon Fiber and Its Polypropylene- and Polyethylene-Based Composites

Due to their lightweight and excellent toughness, carbon fiber (CF) and its reinforced thermoplastic composites are suitable for high-performance applications such as aerospace, aviation, automotive and sport equipments. In this study, comprehensive detail is provided on the production of carbon fiber, its various forms and geometry and their corresponding effects on the mechanical properties of CF and its reinforced polypropylene (PP) and polyethylene (PE) composites. Here we discuss extensively various methods reported in literature on improving the interfacial fiber-matrix adhesion and dispersion in order to achieve better mechanical properties for such composites.

Gelatin and amylopectin-based phase-separated hydrogels: An in-depth analysis of the swelling, mechanical, electrical and drug release properties

The current study delineates the development of gelatin–amylopectin-based phase-separated hydrogels for drug delivery applications. Gelatin and amylopectin were used as the representative protein and polysaccharide phases, respectively. The hydrogels were prepared by adding different proportions of amylopectin to gelatin solutions and subsequently cross-linking the mixture using glutaraldehyde. Microscopic analysis showed formation of phase-separated hydrogels. Secondary structure of gelatin was conserved within the hydrogels. The presence of amylopectin drastically reduced the rate of water absorption by the hydrogels. Viscoelastic analysis using stress relaxation study suggested an increase in the viscous component of the hydrogels with the increase in the amylopectin content. After incorporating amylopectin within the gelatin hydrogel, even though the bulk resistance remained unaltered, there was a corresponding variation in the capacitive elements of the equivalent electrical models. The release of the drug from the hydrogels was diffusion mediated. Suitable mathematical models were used for the analysis of the swelling (Peleg’s model), viscoelastic (Weichert model), electrical (RQQ model) and drug release (Korsmeyer–Peppas and Peppas–Sahlin models) properties. The drug retained its antimicrobial activity within the hydrogels. An analysis of the results suggested that the developed hydrogels may be explored as matrices for controlled drug delivery applications.

Phoenix dactylifera mediated green synthesis of Cu2O particles for arsenite uptake from water

Abstract In this study, an environmentally friendly, cost-effective, and single-step procedure is used for the synthesis of polycrystalline Cu2O particles with controlled morphologies. Simple sugars are extracted from date fruit pulp (Phoenix dactylifera) and used as a reducing agent for the formation of Cu2O particles in aqueous medium. The feasibility of this solution is compared with the standard glucose solution. The Cu2O particles are characterized by electron microscopy, X-ray diffraction, optical absorption and Raman scattering techniques. It is concluded that the morphology of the particles is mainly influenced by the solvents. The obtained Cu2O particles are then used as an adsorbent to uptake As(III) ions from water. The maximum adsorption capacity (Qmax) is estimated by Langmuir and Freundlich isotherms and it is found that Qmax = 14.3 mg g–1. Adsorption kinetics study showed that the adsorption equilibrium could be achieved in 1 h and that the purified water meets the standards of World Health Organization (WHO) for acceptable amount of As(III) in drinking water. Adsorption kinetic models showed that the adsorption is chemisorption in nature.

Rational molecular dynamics scheme for predicting optimum concentration loading of nano-additive in phase change materials

The present study deals with the diffusion and phase transition behaviour of paraffin reinforced with carbon nano-additives namely graphene oxide (GO) and surface functionalized single walled carbon nanotubes (SWCNT). Bulk disordered systems of paraffin hydrocarbons impregnated with carbon nano-additives have been generated in realistic equilibrium conformations for potential application as latent heat storage systems. Ab initio molecular dynamics(MD) in conjugation with COMPASS forcefield has been implemented using periodic boundary conditions. The proposed scheme allows determination of optimum nano-additive loading for improving thermo-physical properties through analysis of mass, thermal and transport properties; and assists in determination of composite behaviour and related performance from microscopic point of view. It was observed that nanocomposites containing 7.8 % surface functionalised SWCNT and 55% GO loading corresponds to best latent heat storage system. The propounded methodology could serve as a by-pass route for economically taxing and iterative experimental procedures required to attain the optimum composition for best performance. The results also hint at the large unexplored potential of ab-initio classical MD techniques for predicting performance of new nanocomposites for potential phase change material applications.

Studies on High Density Polyethylene Reinforced with Phosphate Ore Particles: Thermal, Rheological, Mechanical and Morphological Properties

ABSTRACT Calcareous phosphate ore can be utilized as a cost-effective alternate to other inorganic fillers for polymer-based composites. In this study, composites of high-density polyethylene and phosphate rock ore particles were prepared by melt blending and injection-molding techniques. The thermomechanical, rheological, and mechanical properties of these composites were studied to investigate the effect of filler loading on their functionality. The reduction in the crystallinity of phosphate ore/high-density polyethylene composites was observed compared to that of the neat high-density polyethylene. The relative crystallinity of the neat high-density polyethylene decreases from 53 to 30% by the addition of 2.5–15 wt% of ore, respectively. Comparison of the linear dynamic viscoelasticity for the neat high-density polyethylene and the ore-filled composites shows t a monotonic increase in both storage modulus and loss modulus with the increasing frequency. The viscoelastic behavior at high frequencies remains unaffected. However, at lower frequencies, both G′ and G″ exhibit diminished frequency dependence. It was also observed that higher filler content decreased the tensile and impact strength, whereas the Youngs modulus of the composites increased. The morphological analysis shows relatively weak interaction between the fillers and the matrix because of agglomeration which in turn adversely affects the mechanical properties of the composites. GRAPHICAL ABSTRACT