High-performance water-borne fluorescent acrylic-based adhesive: synthesis and application

Abstract

Water-borne adhesives have immense importance in cellulose-based materials, where their durability, handling, and strength remain to be a major concern. The present work demonstrates the development of three water-borne adhesives, namely, poly(1-vinyl-2-pyrrolidone-co-acrylic acid), poly(acrylonitrile-co-acrylic acid), and poly(1-vinyl-2-pyrrolidone-co-acrylonitrile-co-acrylic acid) applicable for cellulose-based materials. These acrylic-acid based adhesives were characterized by Fourier-transform infra-red spectroscopy, thermogravimetric analysis, X-ray diffraction, gel permeation chromatography, and universal testing machine. The synthesized polymer adhesives can be stored in the powder form for a longer period, thus utilizing less space. In order to use as adhesives, suitable formulations can be prepared in water. The adhesives show thermal stability up to 300 °C. Our studies show that poly(1-vinyl-2-pyrrolidone-co-acrylonitrile-co-acrylic acid) showed higher lap shear strength (ASTM D-906) than commercially available adhesives. In addition, these adhesives, being fluorescent in nature, can be detected under UV light and thus are applicable for the detection of fractured joints of any specimen. This property also helps in anti-counterfeiting applications, thus adding further to their utility.

Fig. 1. (A) Dimensions of a paper specimen prepared for the adhesive tests as per ASTM-D1876; (B) dimensions of the wood specimen prepared for the adhesive tests as per ASTM D-906.

Scheme 1. Schematic representation for the synthesis of the copolymer P(VP-Acr).

Scheme 2. Schematic representation for the synthesis of the copolymer P(Acn-Acr).

Scheme 3. Schematic representation for the synthesis of the copolymer P(VP-Acn-Acr).

Fig. 2. Series of steps depicting the formation and storage of the adhesive powder.

Fig. 3. Photographic images of (A) P(VP-Acr), (B) P(Acn-Acr), and (C) P(VP-Acn-Acr) under normal light, UV light (254 nm), and UV light (365 nm), respectively.

Fig. 4. FT-IR spectra of Acr, P(VP-Acr), P(Acn-Acr), and P(VP-Acn-Acr).

Fig. 5. The probable H-bonding in P(VP-Acn-Acr).

Fig. 6. TGA spectra of the copolymers.

Fig. 7. XRD analysis of the copolymers.

Fig. 8. (A) Dispersion of the polymer powder P(VP-Acn-Acr), in various solvents; (B) dispersion of the polymers P(VP-Acr), P(Acn-Acr), and P(VP-Acn-Acr), respectively, in water as ready-to-use adhesive gels.

Fig. 9. (A) The picture depicting the bonding of a broken specimen design (left) by P(VP-Acn-Acr) and the visibility of the broken joint under normal light (middle) and long-wavelength UV light (right); (B) the figure depicting the visibility of the words written by the adhesive under UV light (365 nm), which are invisible under normal light.