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Sandwich structures with honeycomb core find specific application in impact resistance and energy absorption applications. However, such studies were limited to cores with metallic honeycomb, which had limited energy absorption abilities apart from extrinsic weight. The current work aims to fabricate hybrid sandwich beams made with PCTPE (Plasticized Co-polyamide Thermoplastic Elastomer) nylon using Fused Filament Fabrication (FFF). The cell size was varied from 10 to36 mm with a variation of longest diagonal. The face sheets were prepared with High-density polyethylene (HDPE) matrix with equal loading of Graphite nanoplatelet and Nano-diamond hybrid filler system. The face sheets were joined to honeycomb core to prepare sandwich panel with tailored made adhesive. It was observed that during out of the plane test, for 10 mm cell the SEA (specific energy absorption) was 1.15 kJ/kg, which decreased upto and 69% for 36 mm respectively. During the in-plane flexural test, the minimum flexural modulus showed by 36 mm longest diagonal cell was 31 MPa, which had increased further by 24, 50, 62, 67 and 76% for 27, 21, 15, 12 and 10 mm respectively, indicating elastic nature and damping ability of sandwich beam. The free vibration analysis was performed on by taking cantilever configuration. The experimentally obtained results were then validated using Ansys-14 simulation. It was concluded that PCTPE nylon core exhibited dual properties of stiffness and compliance for the period of out-plane testing and in-plane respectively, with a threshold limit of 36 mm cell size.

A series of novel low band gap donor-acceptor (D-A) type organic co-polymers (BT-F-TPA, BT-CZ-TPA and BT-SI-TPA) consisting of electron-deficient acceptor blocks both in main chains (M1) and at the pendant (M2) were polymerized with different electron rich donor (M3−M5) blocks, i.e., 9,9-dihexyl-9H-fluorene, N-alkyl-2,7-carbazole, and 2,6-dithinosilole, respectively, via Suzuki method. These polymers exhibited relatively low band gaps (1.65−1.88 eV) and broad absorption ranges (680−740 nm). Bulk heterojunction (BHJ) solar cells incorporating these polymers as electron donors, blended with [6,6]-phenyl-C61-butyric acid methyl ester (PC61BM) or [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) as electron-acceptors in different weight ratios were fabricated and tested under 100 mW/cm2 of AM 1.5 with white-light illumination. The photovoltaic device containing donor BT-SI-TPA and acceptor PC71BM in 1:2 weight ratio showed the best power conversion efficiency (PCE) value of 1.88%, with open circuit voltage (V oc) = 0.75 V, short circuit current density (J sc) = 7.60 mA/cm2, and fill factor (FF) = 33.0%.

A series of well-defined donor–acceptor (D–A) conjugated oligomers incorporating thieno[3,4-c]pyrrole-4,6-dione (TPD) acceptor and two symmetrical thiophene units as donor π-bridge along the axes of triphenyl amine core have been synthesized and explored in bulk heterojunction (BHJ) solar cells. Under illumination with AM 1.5 white light (100 mW/cm2), the performance of BHJ photovoltaic devices with an active layer of an electron-donor oligomeric material (TPATP1, TPATP2 or TPATP3) blended with an electron acceptor {[6,6]-phenyl-C61-butyric acid methyl ester (PC61BM) or [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) at various weight ratios has been investigated. The photovoltaic device containing the donor TPATP1 and the acceptor PC71BM at a 1:3 weight ratio exhibited the best efficiency of 1.87% with an open circuit voltage (Voc) of 0.86 V, short circuit current (Jsc) of 6.59 mA/cm2, and a fill factor (FF) of 33%. These results demonstrate that irrespective of conjugation length, tuning of materials with efficient donor and acceptor materials can enhance the optical, electrochemical and eventually the power conversion efficiency (PCE) values of BHJ solar cells. Furthermore oligomers containing TPD acceptor in different structural form have different unique contribution towards photovoltaic properties.

In this chapter, an attempt has been made to review dielectric spectroscopy (DS) as a technique for the characterization of nanomaterials. DS involves the study of the response of a material to an electric field, which furnishes structural information, i.e., molecular structure, physical arrangement, and behavior of the molecules within the structure. DS is a well-established technique in the fields of physics, polymers, and colloidal science and also in pharmaceutics. It is used to measure the dielectric and electric properties of a medium as a function of frequency. Nanomaterials have been known by the term nanodielectric, mainly because of their gradual evolution as excellent functional materials for dielectric and electrical insulation applications. DS has been validated as a powerful technique for appraising the structural and molecular dynamics of nanomaterials. DS in nanomaterial systems is specifically used to probe structure-property relationships, which helps to optimize composition and synthesis/processing conditions, which is useful in the design of new functional materials with envisioned properties. General perspectives such as the principle of DS, dielectric mechanisms such as polarization and relaxation, and dielectric formalisms such as permittivity, electrical modulus, and impedance are described in this chapter. Scopus

An attempt is made to study the effects of gamma irradiation on multi walled carbon nanotubes (MWCNTs) with a specific focus on surface modification, structural changes and identification of irradiation generated defects on their surface. The as-received MWCNTs were chemically treated in order to attach required functional group on the surface and to remove traces of metallic impurities. The MWCNTs were then gamma irradiated at 25, 50, 75 and 100 kGy doses. Micro Raman analysis was performed on irradiated MWCNTs to estimate the irradiation induced defects on their surface, which revealed that the number of defects increased with dose. XRD analysis was also performed to observe the same and it was revealed that the MWCNTs were subjected to micro-straining. The selective area electron diffraction pattern revealed that traces of amorphous carbon were formed after irradiation. Various defects such as bending, variation of internal and external diameter, wall damages formed on the MWCNTs was verified using TEM. It is concluded that subjecting MWCNTs to irradiation sources has produced structural changes and defects on their surface which can influence the properties of nanocomposites.

Sterilization of implants and other clinical accessories is an integral part of any medical application. Although many materials are used as implants, polyethylene stands unique owing to its versatility. Carbon nanotubes are being used as a filler material to enhance the properties of polyethylene. However, the role of multi walled carbon nanotubes (MWCNTs) as an effective antioxidant and radical scavenger in resisting the deteriorating effects of sterilization is yet to be studied in detail. The present work is aimed to investigate the mechanical properties and oxidation stability of irradiated high density polyethylene (HDPE) reinforced by MWCNTs with various concentrations such as 0.25%, 0.50%, 0.75% and 1.00 wt.%. The composites were exposed to 60Co source in air and irradiated at different dosage level starting from 25 to 100 kGy and then shelf aged for a period of 120 days prior to investigation. The loss in toughness, Young’s modulus and ultimate strength at 100 kGy for 1 wt.% MWCNTs composite were found to be 21.5%, 20.3% and 19.2%, respectively compared to that of unirradiated composite. FTIR and ESR studies confirmed the antioxidant and radical scavenging potentialities of MWCNTs with increased concentration and irradiation dosage. It was found that by the addition of 1 wt.% MWCNTs into virgin HDPE, the oxidation index of the composite at 100 kGy was decreased by 56.2%. It is concluded that the addition of MWCNTs into polyethylene not only limits the loss of mechanical properties but also improves its post irradiation oxidative stability.

Crosslinking by gamma irradiation is a key technique employed in industrial and medical application of polymers to improve their mechanical and thermal properties. The objective of the present work is to investigate the effect of gamma irradiation on thermal properties of high density polyethylene (HDPE) reinforced with multiwalled carbon nanotubes (MWCNTs). The chemically treated MWCNTs were coated on HDPE pellets using nanofluid based deposition technique under continuous stirring, which were processed in an injection moulding machine to obtain nanocomposites having 0.25, 0.50, 0.75 and 1.0 wt% of MWCNTs. The nanocomposites thus obtained were exposed to γ-irradiation in the presence of air at 50 and 100 kGy doses. Thermal characterization of nanocomposites was studied using DSC, TGA and TMA techniques. The results obtained from the DSC studies revealed that the melting point of nanocomposites was not significantly influenced by the presence of MWCNTs, while γ-irradiation resulted a marginal change. The crystallinity of the nanocomposites was increased from 37.4 % for unirradiated HDPE to 55.8 % for 1.0 wt% and 100 kGy irradiated sample, which corresponds to 49 % enhancement. The onset temperature of degradation of nanocomposites was found to be influenced by both MWCNTs and irradiation dosage, which was increased by 16 °C for 100 kGy irradiated 1 wt% nanocomposite compared to unirradiated pure polymer. It is also found that the dimensional stability of the nanocomposites was increased by the reinforcement of MWCNTs. It is concluded from the above studies that thermal properties of nanocomposites are significantly influenced by the irradiation process and the concentration of MWCNTs.

Several techniques are available to characterize the influence of γ -irradiation on structural parameters of polymers; among which thermal characterization is more often used. The present work is aimed to study the influence of multi walled carbon nanotubes (MWCNTs) and γ -irradiation on polymer crystallinity, lamellar thick- ness, coefficient of thermal expansion (CTE) and thermal stability of UHMWPE. The chemically treated MWCNTs were homogenously dispersed in UHMWPE using a ball milling machine and compression moulded to make the nanocomposites with different concentration of MWCNTs. The nanocomposites were then γ -irradiated at a dose rate of 2·5 kGy/h up to 25, 50, 75, 100 kGy irradiation doses. The results obtained from TGA studies revealed that the presence of MWCNTs improved the thermal stability and onset temperature of degradation of nanocomposites. The CTE of nanocomposites was decreased with an increase of MWCNTs concentration and irradiation dose. The reduction of thermal expansion of nanocomposites aids in minimizing the dimensional fluctuation of them. It is con- cluded that irradiation and the presence of MWCNTs in UHMWPE not only improved the thermal stability of the composites but also enhanced their crystallinity and lamellar thickness.