P. Prabunathan

High dielectric multiwalled carbon nanotube-polybenzoxazine nanocomposites for printed circuit board applications

The present work describes the development of polybenzoxazine (PBZ) nanocomposite with high dielectric constant using varying weight percentages of (0.5, 1.0, and 1.5 wt. %) benzoxazine functionalized MWCNT (CNT-BS) and benzoxazine through thermal ring opening polymerization. The dielectric constants are increased with increasing weight percentages of incorporation of CNT-BS, whereas dielectric losses are in the reverse trend. Data from Cyclic Voltammogram and impedance studies confirm the conducting behavior of CNT-BS/PBZ nanocomposites. The increase in the weight ratio of CNT-BS enhances the values of Tg and thermal stability. The uniform distribution of functionalized CNT-BS was ascertained from transmission electron microscope.

Development of bio-based F-SBA-15 reinforced epoxy nanocomposites for low-k dielectric applications

The present work focuses on the utilization of renewable biomaterial as reinforcement for the development of nanocomposites for high-performance low-k microelectronic applications. In the present work, rice husk ash (RHA) was chemically treated and processed to obtain two-dimensional mesoporous silica (SBA-15), which was functionalized using 3-glycidoxypropyl trimethoxy silane through sonication process. The surface functionalized SBA-15 (F-SBA-15) with varying weight percentages (1, 3, and 5 wt%) was incorporated into the epoxy resin. The resulting F-SBA-15-reinforced epoxy composites were characterized by Fourier transform infrared spectroscopy, x-ray diffraction, differential scanning calorimetry, thermogravimetric analysis, and impedance analyzer. Among the composite samples with varying loadings, the dielectric behavior of 5 wt% F-SBA-15-loaded composite sample possesses the lowest value of dielectric constant, that is, 2.14 at 1 MHz frequency when compared with that of other samples. Further, the thermal stability was also enhanced to an appreciable extent, when compared with that of the samples with lower F-SBA-15 loadings.

Synthesis of soluble polyimides based on ether-linked cyclohexyldiamine and their ultraviolet shielding behavior

A series of polyimides (PIs) based on ether-linked cyclohexyldiamine were prepared using pyromellitic dianhydride (PI-1), benzophenone dianhydride (PI-2), naphthalene dianhydride (PI-3), and perylene dianhydride (PI-4) in 1-methyl-2-pyrrolidone (NMP) medium to obtain respective polyamic acids and are subsequently converted into PIs through thermal imidization. The resulting PIs were characterized by Fourier transform infrared, X-ray diffraction, thermogravimetric analysis, differential scanning calorimetry, and impedance analyses. In addition, the ultraviolet (UV) shielding ability of PIs was also studied and discussed. The vibrational analysis confirms the imidization, and the XRD profile indicates the amorphous nature of the resulting PIs. The PIs synthesized in the present work exhibit good solubility in organic solvents such as NMP, dimethylformamide (DMF), and dimethyl sulfoxide (DMSO). The PI-4-based imide possesses very good solubility with the highest glass transition temperature value of 256°C, highest char yield of 50.16%, highest dielectric constant of 3.9 and higher UV shielding performance of 89% than those of other PIs. Further, the good solubility also makes them useful for coating applications in aerospace and liquid crystal displays.

Low dielectric and low surface free energy flexible linear aliphatic alkoxy core bridged bisphenol cyanate ester based POSS nanocomposites

The aim of the present work is to develop a new type of flexible linear aliphatic alkoxy core bridged bisphenol cyanate ester (AECE) based POSS nanocomposites for low k applications. The POSS-AECE nanocomposites were developed by incorporating varying weight percentages (0, 5, and 10 wt %) of octakis (dimethylsiloxypropylglycidylether) silsesquioxane (OG-POSS) into cyanate esters. Data from thermal and dielectric studies imply that the POSS reinforced nanocomposite exhibits higher thermal stability and low dielectric value of k = 2.4 (10 wt% POSS-AECE4) compared than those of neat AECE. From the contact angle measurement, it is inferred that, the increase in the percentage incorporation of POSS in to AECE, the values of water contact angle was enhanced. Further, the value of surface free energy was lower when compared to that of neat AECE. The molecular level dispersion of POSS into AECE was ascertained from SEM and TEM analyses.

Bio-based silica-reinforced caprolactam-toughened epoxy nanocomposites

In this work, industrially valuable and versatile nylon 6 precursor material caprolactam has been used as a toughener for diglycidyl ether of bisphenol A epoxy resin (caprolactam epoxy (CPE)) along with glycidyl-functionalized bio silica (GRS) derived from rice husk, which was used as a reinforcement to obtain hybrid nanocomposites with improved properties. Caprolactam (20 wt%) and epoxy (80 wt%) have been reinforced with varying weight percentages (0.5, 1.0 and 1.5 wt%) of GRS cured with diaminodiphenylmethane and characterized using different analytical techniques. Data obtained from mechanical studies indicate that the value of tensile strength, flexural strength and impact strength of 1.5 wt% GRS-reinforced caprolactam-toughened epoxy blend composites were enhanced to 135, 77 and 162%, respectively, compared with those of neat epoxy matrix. Similarly, the values of glass transition temperature and char yield were enhanced to 21 and 22%, respectively, whilst retaining inherent surface and insulating behaviour. Data from morphological studies infer the homogenous and uniform distribution of GRS in the CPE hybrid nanocomposites. From the data obtained from different studies, it is suggested that the hybrid composite materials developed in this work have potential use as coatings, adhesives, sealants, matrices and composites for different industrial and engineering applications in the place of conventional epoxy composites for improved performance and enhanced longevity.

Design of low dielectric constant polybenzoxazine nanocomposite using mesoporous mullite

In this present work, porous mullites (PM0–5) were synthesized through a template-assisted method using various weight percentages of pluronic (P-123). PM5 obtained using 10 wt% of P-123 was found to show maximum porosity (3.8 Å) and low dielectric constant value (2.4). PM5 was functionalized using glycidyl-terminated silane and denoted as FPM and various weight percentages of FPM were reinforced with polybenzoxazine (PBZ) matrix in order to develop FPM/PBZ nanocomposites. The thermal studies indicate that 1.5 wt% of FPM/PBZ nanocomposite showed improved thermal stability with 34% char yield at 800°C and 162°C as glass transition temperature. It also exhibits low dielectric constant (2.6) than that of the neat PBZ matrix and other FPM/PBZ nanocomposites. The microscopic analysis confirms the homogenous dispersion of FPM into the PBZ polymer that has a porous morphology. The results suggest that the as-synthesized mesoporous mullite with low dielectric constant (k), synthesized via template-assisted method can be used as a reinforcement to decrease the dielectric constant of polymeric material, which is of industrial significance.

Studies on graphene oxide–reinforced polybenzoxazine nanocomposites

In the present work, different weight percentages (1, 3, and 5 wt%) of benzoxazine-functionalized graphene oxide (FGO) were reinforced with polybenzoxazine (PBZ) matrix by means of ring-opening polymerization. The resulting nanocomposites were characterized for their thermal, mechanical, dielectric, and optical properties using different analytical techniques. From the results of these studies, it was observed that the 5 wt% FGO-reinforced PBZ composite shows an improved glass transition temperature, thermal stability, and dielectric constant to the extent of 18%, 39%, and 197%, respectively, when compared with those of neat PBZ matrix. Furthermore, 5 wt% FGO-reinforced PBZ composite also exhibits an enhanced ultraviolet shielding efficiency (88%), with improved tensile strength (52%) compared with those of neat PBZ matrix. The enhanced properties may be due to homogeneous and uniform distribution of FGO into the PBZ matrix, which was confirmed from scanning electron microscopic and high-resolution transmission electron microscopic images. Data obtained from these studies indicate that the developed nanocomposites with high dielectric constant can be used in the form of coatings, sealants, and encapsulates for high-performance dielectric as well as antistatic applications.

Exploring Ag-Doped Mullite as High Dielectric and Antimicrobial Reinforcement with Polybenzoxazine Matrix

ABSTRACT The present work describes the development of high k dielectric aluminosilicate and its application as reinforcement with polybenzoxazine matrix to achieve high dielectric and antimicrobial nanocomposite. Initially, dielectric constant value of mullite was found to increase with respect to the percentage of Ag in mullite lattices and reached a maximum of 14.9, when doped with 5 mol%. Data from antimicrobial assay also suggest that, the zone of inhibition expands with respect to embedding silver, and thus 10 mol% of Ag-doped mullite exhibiting the highest antimicrobial property. Since, 3 mol% Ag-doped mullite hold better dielectric, various weight percentages of the same (MA3) were embedded with polybenzoxazine matrices after its surface modification. Among the resulted nanocomposite, 1.5% of glycidyl-functionalized MA3/polybenzoxazine not only showed remarkable enhancement in their thermal, dielectric, electrical conductivity but also exhibited a zone of inhibition of 11 and 12 mm against Escherichia coli and Pseudomonas aeruginosa, respectively. The enhanced thermal, dielectric, and antimicrobial properties will make this material as a suitable candidate in printed circuit board application in particularly for cold weather climatic conditions. GRAPHICAL ABSTRACT

Mullite-reinforced caprolactam-toughened DGEBA epoxy nanocomposites: Preparation and characterization

This work describes the development of different weight percentages of glycidyl functionalized mullite-reinforced caprolactam-toughened epoxy (MCEP) nanocomposites. The functionalization of mullite and MCEP are confirmed by Fourier transform infrared spectroscopic analysis. Further, the morphological, surface behaviour and thermal properties are studied using scanning electron microscopy, transmission electron microscopy, X-ray diffraction, atomic force microscopy, goniometer, thermogravimetric analysis and differential scanning calorimetry analysis. Surface studies show that the values of contact angle increased with increase in weight percentage of mullite and thus 1.5 wt% MCEP nanocomposites show values of higher contact angle (89.6°) and lower water absorption (0.107%) behaviour than those of the composites reinforced with lower wt% of mullite. Moreover, 1.5 wt% MCEP nanocomposites possess better impact behaviour (266.4 J m−2) than that of neat epoxy matrix. Thus the hybrid composite materials developed in this work are expected to find applications in different industrial and engineering sectors with improved performance and longevity.

Studies on Polybenzoxazine/Capron PK4/octakis(dimethylsiloxypropylglycidylether) Silsesquioxane Nanocomposites for Radiation Resistant Applications

Polymeric materials can erode when exposed to the radiation environment that includes atomic oxygen (AO), ultraviolet (UV) ionizing radiation, and ultrahigh vacuum (UHV). Many studies have been devoted to develop polymeric materials that can withstand decades of exposure on radiation. In this connection an attempt has been made to develop polyhedral oligomeric silsesquioxane (POSS) reinforced capron PK4 (CPL) modified polybenzoxazine nanocomposites in the present work and to assess their ability to resist radiation for a prolonged period. Varying weight percentages of (0, 1, 3, and 5 wt%) POSS were reinforced in to 1:1 (w/w) PBZ/CPL copolymerization through chemical ring opening polymerization. The POSS reinforced PBZ/CPL nanocomposites have been studied their tensile strength and morphological behavior before and after exposure of UV irradiation. Data resulted from the studies indicated that the neat PBZ-CPL has significantly eroded after UV exposure, whereas POSS reinforced PBZ/CPL composites have eroded only an insignificant extent and the value of tensile properties are reduced to a small extent. The POSS reinforced nanocomposites during exposure under UV radiation undergo changes on the surface and lead to the formation of silica (Si-O-Si) passivation layer. The formation of silica layer protects (act as inert layer) from further erosion of the composites and was ascertained from SEM images. Data obtained from thermal and dielectric studies indicate that thermal stability and dielectric behavior of composites were appreciably improved when compared with those of neat PBZ/CPL matrix.