Ethylene-acrylate copolymers cyanoacrylates

The homopolymers, which are formed from alkyl cyanoacrylate monomers, are inherently brittle. For applications which require a toughened adhesive, rubbers or elastomers can be added to improve toughness, without a substantial loss of adhesion. The rubbers and elastomers which have been used for toughening, include ethylene/acrylate copolymers, acrylonitrile/butadiene/styrene (ABS) copolymers, and methacrylate/butadiene/styrene (MBS) copolymers. In general, the toughening agents are incorporated into the adhesive at 5-20 wt.% of the monomer. 

An example of this improvement in toughness can be demonstrated by the addition of Vamac B-124, an ethylene/methyl acrylate copolymer from DuPont, to ethyl cyanoacrylate [24-26]. Three model instant adhesive formulations, a control without any polymeric additive (A), a formulation with poly(methyl methacrylate) (PMMA) (B), and a formulation with Vamac B-124 (C), are shown in Table 4. The formulation with PMMA, a thermoplastic which is added to modify viscosity, was included to determine if the addition of any polymer, not only rubbers, could improve the toughness properties of an alkyl cyanoacrylate instant adhesive. To demonstrate an improvement in toughness, the three formulations were tested for impact strength, 180° peel strength, and lapshear adhesive strength on steel specimens, before and after thermal exposure at 121°C. 

Toughened cyanoacrylate adhesives containing random copolymeric elastomers have been patented. The only elastomer whose performance has been quantified is an ethylene-methyl acrylate copolymer sold by Du Pont under the name Vamac B-124. Several other elastomers are said to be useful tougheners, but no details have been given beyond solubility data. 

Acrylic structural adhesives have been modified by elastomers in order to obtain a phase-separated, toughened system. A significant contribution in this technology has been made in which acrylic adhesives were modified by the addition of chlorosulfonated polyethylene to obtain a phase-separated structural adhesive (11). Such adhesives also contain methyl methacrylate, glacial methacrylic acid, and cross-linkers such as ethylene glycol dimethacrylate [97-90-5]. The polymerization initiation system, which includes cumene hydroperoxide, IV,AT - dimethyl-p- toluidine, and saccharin, can be applied to the adherend surface as a primer, or it can be formulated as the second part of a two-part adhesive. Modification of cyanoacrylates using elastomers has also been attempted copolymers of acrylonitrile, butadiene, and styrene ethylene copolymers with methylacrylate or copolymers of methacrylates with butadiene and styrene have been used. However, because of the extreme reactivity of the monomer, modification of cyanoacrylate adhesives is very difficult and material purity is essential in order to be able to modify the cyanoacrylate without causing premature reaction. 

In the last ten years, a number of improvements in cyanoacrylate adhesive technology have been published. Some of these modifications have been translated into new products. For instance, a series of adhesives is being sold with improved performance in the following areas contaminated surface bonding, hard-to-bond plastics, operating temperatures, moisture durability, impact strength, and chlorosis. A toughened cyanoacrylate based on a methyl acrylate-ethylene copolymer has been marked recently. An allyl cyanoacrylate-based adhesive with improved heat durability has also been introduced. A survey of recently patented modifications and improvements for cyanoacrylate adhesives is outlined in Table XIX. 

Although overall adhesive volume increased by 50% in the 1975-87 period, there were seven adhesive materials that experienced growth of at least 100%. These high performers are acrylics, cyanoacrylates, anaerobics, polyvinyl acetate, ethylene-vinyl acetate, styrenic block copolymers, and polyurethanes (Tables 7 and 8). 

Recently, elastomeric fillers have been incorporated into cyanoacrylates to improve the flexibility and toughness of the basically brittle polymers. Copolymers of (a) acrylonitrile, butadiene, and styrene (b) methacrylates, butadiene, and styrene and (c) ethylene with methyl acrylate or vinyl acetate have been reported. See the section on Recent Advances. 

For the purposes of this chapter, acrylic polymers are defined as polymers based on acrylic acid and its homologues and their derivatives. The principal commercial polymers in this class are based on acrylic acid itself (I) and methacrylic acid (II) esters of acrylic acid (III) and of methacrylic acid (IV) acrylonitrile (V) acrylamide (VI) cyanoacrylates (VII) and copolymers of these compounds. Acrylic-ethylene copolymers are described in Chapter 2. The important styrene-acrylonitrile and acrylonitrile-butadiene-styrene copolymers are discussed in Chapter 3 whilst acrylonitrile-butadiene copolymers are dealt with in Chapter 20. 

Toughened acrylics Ethylene-vinyl acetate copolymers Polychloroprene Toughened acrylics when applied to oily surfaces Cyanoacrylate... 

The poly alkyl acrylates and poly cyano acrylates generally resist biodegradation. In soil-burial tests, weight loss has been reported for copolymers of ethylene and propylene with acrylic acid, acrylonitrile, and acrylamide. The rapidly polymerizable systems such as poly(alkyl-2-cyanoacrylate)s adhered to moist surfaces have been examined in biomedical applications. Poly(methyl-2-cyanoacrylate) is the most degradable among the alkyl esters, and its degradability decreases as alkyl size increases (Holland etal., 1990). 

Products obtained by pyrolysis of other polymers is reviewed in Table 4.5. Some specific applications of the chromatography-MS technique to various types of polymers include the following PE [34,35], poly(l-octene) [29], poly(l-decene) [29], poly(l-dodecene) [29], CPE [36], polyolefins [37, 38], acrylic acid-methacrylic acid copolymers [39, 40], polyacrylate [41], nitrile rubber [42], natural rubbers [43, 44], chlorinated natural rubber [45, 46], polychloroprene [47], PVC [48-50], polysilicones [51, 52, 53], polycarbonates [54], styrene-isoprene copolymers [55], substituted olystyrene [56], PP carbonate [57], ethylene-vinyl acetate [58], Nylon 66 [59], polyisopropenyl cyclohexane-a-methyl styrene copolymers [60], cresol-novolac epoxy resins [61], polymeric flame retardants [62], poly(4-N-alkyl styrenes) [63], polyvinyl pyrrolidone [64], polybutyl-cyanoacrylate [65], polysulfides [66], poly(diethyl-2-methacryl-oxy) ethyl phosphate [67, 68], polyetherimide [69], bisphenol-A [70], polybutadiene [71], polyacenaphthalene [72], poly(l-lactide) [73], polyesterimide [74], polyphenylene triazine [75], poly-4-N-vinyl pyridine [76], diglycidylether-bisphenol-A epoxy resins [77], polyvinylidene chloride [78] and poly-p-chloromethyl styrene [79]. 

---