Sumit Manohar Yadav

Bio: Sumit Manohar Yadav is an academic researcher from Kyungpook National University. The author has contributed to research in topics: Wood flour & Urea-formaldehyde. The author has an hindex of 5, co-authored 11 publications receiving 57 citations. Previous affiliations of Sumit Manohar Yadav include Universiti Malaysia Pahang.

Recent Developments in Lignin- and Tannin-Based Non-Isocyanate Polyurethane Resins for Wood Adhesives—A Review

Abstract: This review article aims to summarize the potential of using renewable natural resources, such as lignin and tannin, in the preparation of NIPUs for wood adhesives. Polyurethanes (PUs) are extremely versatile polymeric materials, which have been widely used in numerous applications, e.g., packaging, footwear, construction, the automotive industry, the lighting industry, insulation panels, bedding, furniture, metallurgy, sealants, coatings, foams, and wood adhesives. The isocyanate-based PUs exhibit strong adhesion properties, excellent flexibility, and durability, but they lack renewability. Therefore, this study focused on the development of non-isocyanate polyurethane lignin and tannin resins for wood adhesives. PUs are commercially synthesized using polyols and polyisocyanates. Isocyanates are toxic, costly, and not renewable; thus, a search of suitable alternatives in the synthesis of polyurethane resins is needed. The reaction with diamine compounds could result in NIPUs based on lignin and tannin. The research on bio-based components for PU synthesis confirmed that they have good characteristics as an alternative for the petroleum-based adhesives. The advantages of improved strength, low curing temperatures, shorter pressing times, and isocyanate-free properties were demonstrated by lignin- and tannin-based NIPUs. The elimination of isocyanate, associated with environmental and human health hazards, NIPU synthesis, and its properties and applications, including wood adhesives, are reported comprehensively in this paper. The future perspectives of NIPUs’ production and application were also outlined.

Modification of Pristine Nanoclay and its Application in Wood-Plastic Composite

Abstract: The modification of pristine nanoclay and its application in wood plastic composite (WPC) have been investigated in this paper. Pristine nanoclay was modified using transition metal ion (TMI) which was copper (II) chloride to achieve good dispersion and to improve properties of WPC. The morphology, composition, structure, and thermal stability of TMI-modified nanoclay were studied by field emission scanning electron microscopy (FESEM), energy dispersive X-ray analysis (EDX), X-ray diffraction (XRD) and thermogravimetric analysis (TGA) analysis. The pristine (WPC/MMT) and TMI-modified (WPC/MMT Cu) nanoclay based WPC were made from polypropylene (PP), wood flour (WF), and maleic anhydride grafted polypropylene (MAPP) coupling agent. Pristine and modified nanoclay with different concentration (1 wt%, 2.5 wt%, 4 wt% and 5 wt%) were used as a reinforcing filler for WPC. Mechanical, physical, morphological, and thermal properties of the prepared composites were evaluated. Result exhibit that at 1 wt% nanoclay content, the tensile, flexural, and impact strength of WPC/MMT improved by approximately 6%, 4%, and 8%, respectively, compared to WPC without nanoclay. For the WPC/MMT Cu, the improvements in these properties were about 2.6, 2.1 and 3 times higher than the WPC/MMT. The physical and thermal properties also improved by incorporating modified nanoclay in WPC.

Mechanical And Physical Properties of Wood-Plastic Composites Made of Polypropylene, Wood Flour and Nanoclay

Abstract: The focus of this study was to characterize mechanical and physical properties of experimental composition prepared from nanoclays (Cloisite® 20A), wood flour (WF) and polypropylene (PP). Nanoclays with different concentrations were used as reinforcing filler for wood plastic compositions (WPCs). Maleic anhydride grafted polypropylene (MAPP) was added as a coupling agent to increase the interaction between the components of wood-plastic composites. Nanoclay based wood-plastic composites were made by extrusion process and then injection molding. Mechanical and physical properties of the as-prepared composites were evaluated. The results of strength measurements showed that the flexural modulus of the composite was increased by 56.33 % with increasing of nanoclays contents to 5 wt. %, reaching approximately 3.58 GPa compared to WPC containing 0% of nanoclays. Moreover, the flexural and tensile strengths reached their maximum values when the concentrations of nanoclays was 2.5 wt. %. When maintaining the nanoclays at a low concentration, it was well dispersed in the WPC. However, when more nanoclays (4 –5 wt. %) was introduced, the enhancing effect began to diminish because of the agglomeration of nanoclays which caused poor interfacial adhesion. The addition of nanoclays decreased the average water uptake by 13 %, compared to the control sample (without nanoclays). The improvement of physical and mechanical properties confirmed that nanoclays has good reinforcement and the optimum effect of nanoclays was archived at 2.5 wt. %.

Modification of Oxidized Starch Polymer with Nanoclay for Enhanced Adhesion and Free Formaldehyde Emission of Plywood

Abstract: This study is aiming of developing eco-friendly wood adhesive based on oxidized starch (OS) modified by nanoclay to enhance their adhesion and no formaldehyde emission. Two types of nanoclay such as pristine-bentonite (P-BNT) and transition metal ion modified-pristine-bentonite (TMI-P-BNT) at three levels (i.e., 1, 3, and 5%) were used for the modification of OS adhesive. Basic properties, chemical properties and thermal properties of the modified OS adhesives were examined with various analysis techniques to understand the influence of nanoclay modification on OS polymer. As the nanoclay level increased, the modified OS adhesives had greater solids content and viscosity but the gelation time decreased, indicating a faster curing of the modified OS adhesive. X-Ray diffraction of the modified OS adhesives resulted in a decrease in the 2θ value and enlarged d-spacing value, showing that the nanoclay had been intercalated within OS polymer molecules. Two peaks at 526 cm−1 and 461 cm−1 detected by FTIR were assigned to Si–O–Al and Si–O–Si vibrations, respectively, and confirmed the presence of nanoclay in the OS polymer. Thermogravimetric analysis showed that the added nanoclay improved thermal stability of OS adhesives. The modified OS adhesives with 5% TMI-P-BNT enhanced their adhesion strength from 0.9 to 1.25 MPa, and resulted in free formaldehyde emission (near to 0.01 mg/L) from plywood panel. These results indicated that the modification of OS adhesives with 5% TMI-P-BNT could be used as bio-based and environmentally friendly plywood adhesive with zero formaldehyde emission.

Effects of nanoclay modification with transition metal ion on the performance of urea–formaldehyde resin adhesives

Abstract: As a way of reducing the formaldehyde emission and improving the adhesion of urea–formaldehyde (UF) resins, this study investigated the addition effects of pristine nanoclay (PNC) or modified nanoclay (MNC) with transition metal ion (TMI) on the performance of UF resin adhesives. Instead of a conventional simple mixing (SM) of MNC with UF resin (coded as MNC-SM), this study explored adding PNC or MNC into either the alkaline (ALK) or acidic (ACD) reaction during the synthesis of UF resins, which were coded as PNC-ALK, PNC-ACD, MNC-ALK, and MNC-ACD, respectively. For the first time, we report that the MNC-ALK resins result in almost amorphous UF resins with 25% crystallinity, which consequently increases the cross-linking, and improve the adhesion strength and decrease formaldehyde emission of modified UF resins. It is believed that the intercalated or exfoliated MNCs facilitate the formation of more cross-linking in the modified UF resins, leading to a better cohesive strength.

Recent Advances in Nanoclay/Natural Fibers Hybrid Composites

Abstract: The growing demand for continual improvement in the engineering applications of thermoplastic and thermoset polymer materials compared with metals in various applications led to the emergence of hybrid nanocomposites by the addition of different nano fillers, with advanced properties. Nano fillers such as carbon black, pyrogenic silica, nano oxides and metal particles are being used as additives in polymers from decades. However, the increasing stringent environmental legislation and consumer awareness highlights the importance of natural, low cost and abundant clay materials such as nanoclays. The hybridization of natural fiber with nanoclay is interestingly positive due to the tendency of nanoclay to upsurge both flexibility and rigidity of the natural fiber in one step. The most promising nanoclay involved in the modification of polymers and natural fibers reinforced polymer composite are montmorillonite, organoclay, saponite and halloysite nanotubes. Nanoclay/natural fibers hybrid nanocomposites have engrossed great attention since their discovery due to their wide variety of properties in food packaging, biomedical devices, automotive industries and other consumer applications with better thermal, physical, mechanical, optical and barrier properties. Present article designed to be a comprehensive source of recent literature and study on nanoclay fillers, its different classes, modification of polymers by nanoclay and their varied applications. This article also intended to covers the recent advances in natural fiber/nanoclay hybrid polymer nanocomposites research study, including their different commercial applications.