Effect of Anhydride Addition to Alkyl Cyanoacrylate on its Adhesive Bond Durability

 IOLOGY VHS will be evaluated zen submitted to any pers. It is the ployer and all papers ,single~sided on ginning with the title and address(es) of and address of the words and 4-8 rate sheet. When a the above style must lethods, Results, )n should be placed iternational System iations should be of the page. Special tactly as they should icated by under avavy underline). In in displayed 5 in text discussion 0) and o (the letter); 5 an element of’; etc. in arabic numerals. gures and chemical ie text as original per. Lettering on iure legibility after top ofthe figure by ronsecutively in the iumbers should be in section in the ime(s) of author(s), unsored by the )rs), volume number :numbers, year of 984) hould be listed id.), vol. 2, 1 York (1983). y statingthe name 18 to the original are not accepted its may be ordered ofs. J. Adhesion Sci. Technol. Vol.6, No. 7,pp. 781-789 (1992) © VSP 1992. Effect of anhydride addition to alk _ yl cyanoacrylate on its adhesive bond durability Organic Coatings and Poly Hyderabad 500 007, India Revised version received 10 March 1992 Keywords: Bond durability; effect of anhydride; propyl cyanoacrylate. 1. INTRODUCTION responses to environmental effects. Cyanoacrylate—based adhesives have a reputation of poor durability, especially when bonding metal substrates [1]. However, on many plastic and rubber surfaces, the durability of these adhesives equals or surpasses that of the substrate [2]. erating temperature restrictions have prompted e these limitations by adding either crosslinking __________ *To whom correspondence should be addressed. 782 I/. Vi/ayalakshmi et al. Therefore, we report here quantitative data on the heat ageing and moisture resistance properties of the adhesive bonds formed using cyanoacrylates containing different anhydrides, between various metals and other substrates. 2. EXPERIMENTAL All the raw materials used in this investigation were at least 98% pure. 2.]. Synthesis of n—pr0pyl cyanoacrylate (PIC/1) n—Propyl cyanoacetate was synthesized by reacting n—propyl alcohol (1.0 mol) with cyanoacetic acid (1.2 mol) in the presence of p—toluene sulphonic acid and benzene in an amount equal to the total weight of the reactants.‘The contents were heated to reflux and the course of the reaction was followed by the amount of water removed azeotropically and collected in a Dean-Stark trap. The reaction took 6-8 h for completion and during this period, 1 mol of water was collected in the Dean-Stark trap. The reaction product was washed to remove catalyst and unreacted ‘cyanoacetic acid, and then dried over anhydrous sodium sulphate. Benzene was stripped off and the product was distilled under reduced pressure (b.p. 106—108°C at 10 mmHg, yield 70-75%). Purity 98% as determined by gas liquid chromatography (GLC); 11%” 1.4040; dfi" 1.0117. n—Propyl cyanoacrylate was then prepared by condensation of the n—propy1 cyanoacetate with paraformaldehyde in the presence of piperidine and potassium hydroxide (0.1% each, based on reactants) dual catalysts and using benzene in an amount equal to the reactants for azeotropic removal of water. The mole ratio of cyanoacetate to paraformaldehyde was maintained at 1.30. The reaction product, an oligomer, was then treated with polyphosphoric acid to neutralize the catalyst and decanted to remove the solid phosphates. The oligomer was then subjected to depolymerization at 150—240°C at 0.1-2.0 mmHg pressure. The crude monomer thus obtained was again redistilled for purification at 60-62°C (1-2 mmHg) and stabilized with 80-100 ppm sulphur dioxide and 100-150 ppm hydroquinone (yield 88%; purity 99.5% as determined by GLC; Hf)” 1.4314; dfi“ 1.0050. It was also characterized by ‘H—NMR (80 MHz Varian FT—80A NMR), ‘3C—NMR (Bruker AM 300 MHZ), and mass spectrometry (70 eV Micromass VG 7070, UK) methods. The ‘H- and “C-NMR spectra are illustrated in Figs 1 and 2, respectively. The mass spectral diagnostic fragments are shown below: CN 0 43 J 1 J 1 52 80 110