Pressure-Sensitive Adhesives Based on Epoxidized Soybean Oil and Dicarboxylic Acids

Abstract

Existing pressure sensitive adhesives (PSAs) are mainly derived from petrochemicals. This study describes a novel approach for development of biobased PSAs. Epoxidized soybean oil was polymerized and cross-linked with a dicarboxylic acid to generate superior PSAs. The dicarboxylic acids used in this study included dimer acid (DA), sebacic acid, adipic acid, and a difunctional polymeric carboxylic acid that was prepared from polymerization of bisphenol A diglycidyl ether (BPAGE) and an excess of DA. AMC-2, a chromium-(III)-based organometallic compound, was found to be the most effective catalyst for the polymerization/cross-linking. The PSAs had a peel strength of 1.4−5.0 N/cm, a loop tack of 7.1−12.6 N, a shear strength of 34 min to more than 168 h, and a good aging resistance. The adhesive properties of the PSAs can be tailored for specific applications such as PSA tapes and labels through the selection of the dicarboxylic acid and its usage. Incorporation of a small amount of phenylene-containing monomer BPAGE into the PSAs significantly increases the peel and shear strengths of the resulting PSAs. This new class of PSAs can be fully based on renewable materials. The preparation of the PSAs does not use any organic solvent or toxic chemicals, thus being environmentally friendly.

Development and Characterization of Pressure-Sensitive Adhesives from Dimer Acid and Epoxides

“…The 90°peel, shear, and loop tack tests of the PSA samples were performed in accordance with the conditions and methods described in our previous studies (14,15).…”

“…After one or four weeks, the sample tapes were taken out of the incubator and conditioned at 23 ± 1°C and 40 ± 5 % RH for 16 h. PSA specimens were then prepared from the aged sample tapes and measured for their peel strength and loop tack in accordance with the methods described previously (14,15).…”

“…A mixture of DA and each of the epoxides was polymerized and completely cured under the conditions described in Table 1. AMC-2 has been demonstrated to be an efficient catalyst for accelerating the reaction between a -COOH and an epoxy group in studies by our research group (14,15) and others (4), and was used as the catalyst for the polymerization of the DA-epoxide mixtures in this study.…”

“…Polymerizations of the EFA mixture in the presence or absence of a small amount of dicarboxylic acids readily afforded PSAs with superior properties (14). Reactions of dicarboxylic acids with epoxidized soybean oils were also found to generate superior PSAs (15). In this study, we investigated a new approach of developing PSAs from the direct polymerization of DA with various epoxides containing two or three epoxy groups.…”

Quantitative analysis of cyclic dimer fatty acid content in the dimerization product by proton NMR spectroscopy

“…Dimer acids, produced by the dimerization of unsaturated fatty acids from vegetable oil, are highly value-added products and are widely used as adhesives [7][8][9], plastic additives [10,11], and lubricants [12]. Several synthesis methods have been investigated to date to obtain dimer acids.…”