Thermal degradation of EVA and EBA—A comparison. II. Changes in unsaturation and side group structure

Abstract

SYNOPSISThis is the second in a series of papers in which the thermal degradation of ethylene-vinyl acetate (EVA) and ethylene-butyl acrylate ( E B A ) copolymers are compared. The EBA samples contain 0.8, 1.6, and 5.4 mol % butyl acrylate ( B A ) , respectively, and the EVA samples 1.2 and 6.7 mol % vinyl acetate ( V A ) . The samples were heated in nitrogen in a tubular oven at 285, 333, 350, 370 and 390°C for 6-120 min. The samples were analyzed with IR, NMR, gravimetry, and titration of carboxylic groups. The EVA samples were rapidly degraded by deacetylation, which was complete after about 30 min a t 333°C. A linear relation between the loss of acetate groups and the formation of trans double bonds was found. A small amount of keto groups and traces of lactones were also observed. The data confirm the previously proposed mechanisms for deacetylation and the formation of acetaldehyde. A mechanism for lactone formation is suggested. The deacetylation rate is increasing with the VA content, presumably because of an increased amount of block sequences and a n enhanced acid catalytic effect. The acrylate sidegroups are much more stable than the acetate groups, and are similar in stability to the main hydrocarbon chain. The BA decomposition results in carboxylic and anhydride groups. Decarboxylation also occur and increases with the thermal treatment. In LDPE and EBA the increase in unsaturation is small and mainly due to vinyl end groups formed via P-cleavage or disproportionation. In EVA the formation of vinyl end groups is suppressed.

Linking the flame‐retardant mechanisms of an ethylene‐acrylate copolymer, chalk and silicone elastomer system with its intumescent behaviour

“…(This temperature interval corresponds to the first minor mass loss seen in curve 3a in Figure 3.) Further, curve 3b in Figure 3 shows a minor indication of an endothermic reaction (2508C) which is directly followed by an exothermic reaction (2808C). The endothermic reaction can most likely be associated with the ester pyrolysis of EBA, which is known to start in this temperature range [7,8]. It can be noted that the exothermic peak is not seen when using N 2 atmosphere, see the light dotted line in Figure 4.…”

“…the butyl acrylate groups are transformed into acidic groups, and butene evaporates as a gas [7,8]. Ionomers are then formed between the carboxylates originating from the acidic groups and calcium ions originating from the chalk (CaCO 3 ) [9].…”

TG/FTIR study of the thermal pyrolysis of EVA copolymers

“…According to McGrattan [11] and Sultan and Sörvik [12][13][14], EVA copolymers undergo a two-step decomposition: an acetate pyrolysis of the copolymer leaving a polyunsaturated linear www hydrocarbon and evolving mainly acetic acid, followed by the breakdown of the hydrocarbon backbone to produce a large number of straight-chain hydrocarbon products. It is interesting to note that the above-mentioned work of McGrattan [11] was carried out using a combination of TG/ FTIR.…”

“…Ethylene-vinyl acetate (EVA) copolymers represent the largest-volume segment of the ethylene copolymer market [9], and several authors have studied the thermal cracking of EVA copolymers with different purposes [10][11][12][13][14][15][16][17][18][19]. According to McGrattan [11] and Sultan and Sörvik [12][13][14], EVA copolymers undergo a two-step decomposition: an acetate pyrolysis of the copolymer leaving a polyunsaturated linear www hydrocarbon and evolving mainly acetic acid, followed by the breakdown of the hydrocarbon backbone to produce a large number of straight-chain hydrocarbon products.…”

Development of new thermoplastic elastomers from blends of polyethylene and ethylene-vinyl acetate copolymer by electron-beam technology

“…At higher radiation levels, an increased movement of chain branches takes place, possibly due to the elimination of the VA group. 34 The dynamic storage modulus initially increases with the radiation levels, reaches its maximum value at a radiation dose of 50 kGy, and then decreases with increase in the radiation levels. An initial increase in the storage modulus is probably due to the crosslinking and improvement in interfacial adhesion.…”