MIT-World Peace University (MIT-WPU) is a top educational institute located in Pune, India. It is recognized within&nbsp;UGC under Government of Maharashtra Act No. XXXV 2017.&nbsp;

It is part of the MIT group of institutions (established in 1983) which covers 10+ campuses across India and has more than 50,000+ students enrolled across various disciplines at a given point of time. The institute houses 15 schools ranging from Engineering &amp; Technology, Design, Pharmacy, Commerce, Governance among others. It offers undergraduate, postgraduate and PhD programs among different disciplines.&nbsp;

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MIT World Peace University

Unsaturated polyesters resins (UPRs) comprise an important class of thermoset polymers. They are used extensively due to their low cost, easy processability, good corrosion resistance, and availability in a variety of grades. During their curing process they do not emit any volatile by-products; this feature makes them more attractive. They are classified into five different types based on structure. The properties of UPRs can be tailored by varying the type and ratio of monomers and curing agents used. Generally, aromatic groups improve hardness and stiffness while aliphatic chain components increase flexibility. However, as they contain polyester linkages, they are susceptible to water, have high glass transition temperatures (Tg), and have poor fire resistance. Although they have stable structures and good mechanical and thermal properties compared to other thermosets, they are not suitable for advanced applications. Hence, they have been modified as blends, interpenetrating polymer network (IPNs), composites, nanocomposites, and others. The blending of polymers results in the formation of new materials which combine the useful properties of each constituent polymer. UPRs have been blended with elastomers (e.g., nitrile butadiene rubber, maleated nitrile rubber, carboxyl-terminated butadiene acrylonitrile rubber, etc.,) to improve their impact strength and other mechanical properties. Usually, fire properties are enhanced by blending with phenol formaldehyde resins. UPR blends with epoxy resin show improved toughness and impact properties. In some blends, superior thermal and damping properties are observed. IPNs are blends of two or more polymers in a network form, with one of the polymers synthesized and/or cross-linked in the immediate presence of the other(s). Although they are not bonded covalently with each other, they have partial or total physical interlocking between them. Semi-IPNs and full IPNs of UPR with other polymers such as polyurethanes, epoxy, nylons, phenol formaldehyde resin, and polyacrylates are discussed. Composites are made by combining two dissimilar materials at a macroscopic level in such a way that the resultant material is conferred with properties superior to those of any of its components. Of the two, one is the continuous phase, known as the matrix, and the other is the reinforcement. These components neither take part in any chemical reaction nor do they dissolve or completely merge into each other, yet they still remain strongly bonded and maintain an interphase between them. The reinforcement and matrix are complimentary to each other. They make use of each other’s properties in such a way that the composite exhibits enhanced properties. The reinforcing material may be in the form of fibers, particles, or flakes, and the polymer constitutes the matrix. Glass-reinforced composites are most popular, but apart from these, natural fibers such as sugar palm fibers, coconut fibers, henequen fibers, cotton fibers, hemp fibers, kenaf fibers, etc., have been used. Composites with metals, metal oxides, carbon fibers, and graphite have also been investigated. They have superior mechanical, chemical, thermal, and electrical properties. Nanocomposites consist of nanofillers dispersed in a polymer matrix with the reinforcement having a nanoscale structure (at least one dimension less than 100 nm) with a high aspect ratio (surface to volume ratio). A smaller size of filler leads to an exceptionally large interfacial area between the matrix and reinforcement compared to conventional composites. Polymer nanocomposites show significantly enhanced properties at much lower filler loading rates, which ultimately results in lower component weight and can simplify processing. In general, nanofillers are broadly classified on the basis of their geometries as particles, layered, or fibrous materials. Examples of particle-type nanofillers are carbon black, metal oxides (ZnO, Al2O3, and TiO2), silica nanoparticles, and polyhedral oligomeric silsesquioxanes. Carbon nanotubes (CNTs) and cellulose nanofibrils are examples of fibrous materials, while nanoclays and montmorillonite are layered materials. UPR nanocomposites show improved thermal, mechanical, electrical, water absorption, solvent resistance, flame retardancy, and volume shrinkage properties. Modification or functionalization of polymers and/or fillers leads to further enhancements in the properties of these materials. They are widely used in several industrial applications such as the automotive, construction, marine, and electrical fields, as well as in coatings, among others. Major challenges faced by the composite industry include reducing dependency on petroleum sources for the synthesis of UPRs by recycling polymer waste and making use of sustainable sources, the elimination of halogens in order to achieve fire retardancy, and the replacement of styrene to overcome environmental and health hazards. © 2019 Elsevier Inc. All rights reserved.

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School of Chemistry

Unsaturated Polyester Resins

Unsaturated polyester resins, blends, interpenetrating polymer networks, composites and nanocomposites: State of the art and new challenges

Epoxy resin nanocomposites containing graphite nanosheets (GNS) and unsaturated polyester resin (UPR) were prepared by incorporating GNS in semi interpenetrating network (semi-IPN) of epoxy resin and unsaturated polyester resin (E-UPR). GNS are prepared by thermal shock treatment of sulphuric acid-graphite intercalation compound (GIC) followed by ultra-sonication. The E-UPR-GNS semi-IPNs were further modified with aromatic amines such as benzidine (Bz) and diphenyl amine (DPA). All the samples were prepared by mixing Triethylenetetramine (TETA) as the curing agent at two different temperatures viz. room temperature (RT) and low temperature (LT; 5 °C). A transition is observed in the conducting properties of the samples: from an electrical insulator to an electrical semiconductor in case of nanocomposites especially on addition of GNS to E-UPR semi-IPNs. A sharp improvement is observed in conductivity after modification with diphenyl amine (DPA) cured at LT. The nanocomposites obtained at LT exhibit homogeneity with minimum anisotropy in conductivity. The morphology, mechanical, thermal and electrical properties were evaluated using various analytical techniques. Positron annihilation spectroscopy was carried out to correlate the measured properties with the free volume and free volume hole size distribution. The results are consistent with the reported studies. © 2016 Elsevier Ltd

Polymer

Electrically conductive epoxy-polyester-graphite nanocomposites modified with aromatic amines

Epoxy-conducting polymer/metal composites as sensors for humidity and chemical vapour. Pune

Semi-interpenetrating polymer networks (Semi-IPNs) based on epoxy and unsaturated polyester resin (UPR; added in 5.9 and 11.1 wt %) have been prepared by chemical route. Room temperature curing was attempted using triethylene tetramine as a hardener. Blend with 11.1% UPR is found to exhibit best mechanical properties. Further, blends were also prepared by adding aromatic amines such as diphenylamine (DPA, secondary amine) and benzidine (Bz, primary amine). Structural elucidation of the samples through identification of functional groups was carried out with the help of Fourier transform infra red spectroscopy. Absence of peak at 915 cm -1 (characteristic of epoxy ring) confirmed complete curing in all the blends. The mechanical properties such as hardness, izod impact and tensile strength of blends were compared. The co-cured blends show decrease in shore hardness (≈ 1-6%), while, the izod impact exhibits an opposite trend. Blends with 10% DPA and Bz show an increase in izod impact by 268.6% and 38.8% respectively. Further, the tensile strength is observed to be enhanced by 45% in case of DPA while addition of Bz reduces it by 32.8%. Thermal properties were studied by thermogravimetric (TGA) and differential scanning calorimetric (DSC) analysis. TGA shows no significant change in onset and decomposition temperature but temperature at which it melts is lowered almost by 100-150°C together with the onset temperature (by ≈ 200°C) observed in DSC. Scanning electron micrographs reveal granular nature of the samples. The homogeneity of blends appears to be good. The blends co-cured with DPA are relatively crystalline compared with others. Copyright © 2011 Wiley Periodicals, Inc.