Ethylene-methacrylate ionomers

Ethylene monoChloroTriEluoroEthylene Electrical Electronics Ethylene-MethAcrylate ionomers ElectroMagnetic Interference EPoxy... 

Acrylics. Acetone is converted via the intermediate acetone cyanohydrin to the monomer methyl methacrylate (MMA) [80-62-6]. The MMA is polymerized to poly(methyl methacrylate) (PMMA) to make the familiar clear acryUc sheet. PMMA is also used in mol ding and extmsion powders. Hydrolysis of acetone cyanohydrin gives methacrylic acid (MAA), a monomer which goes direcdy into acryUc latexes, carboxylated styrene—butadiene polymers, or ethylene—MAA ionomers. As part of the methacrylic stmcture, acetone is found in the following major end use products acryUc sheet mol ding resins, impact modifiers and processing aids, acryUc film, ABS and polyester resin modifiers, surface coatings, acryUc lacquers, emulsion polymers, petroleum chemicals, and various copolymers (see METHACRYLIC ACID AND DERIVATIVES METHACRYLIC POLYMERS). 

Ionomer resins consisting of ethylene—methacrylic acid copolymers partially neutralized with sodium or zinc were commercially introduced in 1964 by Du Pont under the Sudyn trademark (1). More recently, a similar line of products, sold as Hi-Mdan resins, has been commercialized by Mitsui—Du Pont in Japan. lolon ionomeric resins, based on ethylene—acrylic acid, are produced by Exxon in Belgium. Ionomers containing about 1 mol % of carboxylate groups are offered by BP in Europe as Novex resins. Low molecular weight, waxy Aclyn ionomers are produced and sold by AHiedSignal. 

Figure 4 Secant modulus versus percent conversion for Na and Ca salts of an ethylene/methacrylic acid ionomer.

Ionomer. Ionomer is the generic name for polymers based on sodium or zinc salts of ethylene-methacrylic acid copolymers in which interchain ionic bonding, occurring randomly between the long-chain polymer molecules, produces solid-state properties. 

Ethylene-based ionomers, 14 482 Ethylene-based (C-2) process, for methyl methacrylate production, 16 244, 252-254... 

Ethylene methacrylic acid (1-10%) copolymers are known as ionomers Some of the COOH groups are esterified in the commercial product. 

Table I. duPont Ethylene-Methacrylic Acid Ionomer Resins...

Figure 17 shows the infrared spectra (from 1900 to 1200 cm-1) of the completely ionized calcium ionomer of an ethylene-methacrylic acid copolymer recorded at room temperature (a) and the same film recordered at 40, 70, 130, and 150 °C (b-e, respectively). This recording of the spectra at the elevated temperatures accentuates the sharp doublet at 1515/1548 cm which is characteristic of an interaction or vibrational splitting of the pairs of COO" groups. 

The first commercial ionomers were introduced in the mid-1960s when Dupont produced an ethylene/methacrylic acid copolymer under... 

Acrylic acid [79-10-7] - [AIR POLLUTION] (Vol 1) - [ALDEHYDES] (Vol 1) - [ALLYL ALCOHOL AND MONOALLYL DERIVATIVES] (Vol 2) - [MALEIC ANHYDRIDE, MALEIC ACID AND FUMARIC ACID] (Vol 15) - [POLYESTERS, UNSATURATED] (Vol 19) - [FLOCCULATING AGENTS] (Vol 11) - [CARBOXYLICACIDS - SURVEY] (Vol 5) -from acetylene [ACETYLENE-DERIVED CHEMICALS] (Vol 1) -from acrolein [ACROLEIN AND DERIVATIVES] (Vol 1) -acrylic esters from [ACRYLIC ESTER P OLYMERS - SURVEY] (Vol 1) -from carbon monoxide [CARBON MONOXIDE] (Vol 5) -C-21 dicarboxylic acids from piCARBOXYLIC ACIDS] (Vol 8) -decomposition product [MAT. ETC ANHYDRIDE, MALEIC ACID AND FUMARIC ACID] (Vol 15) -economic data [CARBOXYLIC ACIDS - ECONOMIC ASPECTS] (Vol 5) -ethylene copolymers [IONOMERS] (Vol 14) -in floor polishes [POLISHES] (Vol 19) -in manufacture of ion-exchange resins [ION EXCHANGE] (V ol 14) -in methacrylate copolymers [METHACRYLIC POLYMERS] (Vol 16) -in papermaking [PAPERMAKING ADDITIVES] (Vol 18)... 

Infrared Spectra of Ionomers. Infrared absorption data, first published in 1964 (11), show that partial neutralization of ethylene—methacrylic acid introduced new absorption bands at 1480-1670 cm-1 for the ionized carboxylate group while the 1698 — cm-1 band of the free acid carboxyl diminishes in size (21). In addition to providing information on structural features, the numerous absorption bands are significant in applications technology, providing rapid warmup of film and sheet under infrared radiation. 

Carboxylate ionomers have been characterised with Fourier transform-infrared (FT-IR) in the region of antisymmetric stretching vibration of carboxylate anions. Figure 4.8 shows carboxylate ionomer [89] of ethylene methacrylic (4%) copolymer). 

The ionic aggregates present in an ionomer act as physical crosslinks and drastically change the polymer properties. The blending of two ionomers enhances the compatibility via ion-ion interaction. The compatibilisation of polymer blends by specific ion-dipole and ion-ion interactions has recently received wide attention [93-96]. FT-IR spectroscopy is a powerful technique for investigating such specific interactions [97-99] in an ionic blend made from the acid form of sulfonated polystyrene and poly[(ethyl acrylate - CO (4, vinyl pyridine)]. Datta and co-workers [98] characterised blends of zinc oxide-neutralised maleated EPDM (m-EPDM) and zinc salt of an ethylene-methacrylic acid copolymer (Zn-EMA), wherein Zn-EMA content does not exceed 50% by weight. The blend behaves as an ionic thermoplastic elastomer (ITPE). Blends (Z0, Z5 and Z10) were prepared according to the following formulations [98] ... 

Kutsumizu, S. Nakumura, Y. Yano, S. Pressure-induced coordination-structural change around zinc(II) in zinc(II)-neutralized ethylene-methacrylic acid ionomers. 1. Infrared spectroscopic studies. Macromolecules 2001, 34, 3033. 

Tierney, N.K. Register, R.A. Ion hopping in ethylene-methacrylic acid ionomer melts as probed by rheometry and cation diffusion measurements. Macromolecules 2002, 35, 2358. 

Figure 8. Effect of acid absor-ption by an ethylene-methacrylic acid ionomer (16 wt % methacrylic acid, neutralized 37% with a) on the small angle x-ray scattering peak absorption of (a) methacrylic acid, (b) acetic acid, (ci formic acid. (Reproduced from ref. 42. Copyright 1973 American Chemical Society.)...

Reference 7 reviews a number of electron microscopy studies of ionomer morphology in the period up to 1979. None of these studies makes a convincing case for the direct imaging of ionic clusters. This is because of the small size of the clusters (less than 5 nm based on scattering studies) and difficulties encountered in sample preparation. The entire problem was reexamined in 1980(21). In this study ionomers based on ethylene-methacrylic acid copolymers, sulfonated polypentenamer, sulfonated polystyrene and sulfonated ethylene-propylene-diene rubber (EPDM) were examined. The transfer theory of imaging was used to interpret the results. Solvent casting was found to produce no useful information about ionic clusters, and microtomed sections showed no distinct domain structure even in ionomers neutralized with cesium. Microtomed sections of sulfonated EPDM, however,... 

The effect of temperature on a SAXS scan is shown in Figure 11. Note that the reflection at 4 nm persists above the melting point of the polymer, 265°C. Similar behavior was observed in ethylene/methacrylic acid ionomer (21, 22) and is strong support for the existence of ionic clustering in the dry state of the polymer. Indeed, we will demonstrate shortly that this reflection is observed in dry polymers at room temperature neutralized with heavier metal ions. 

The effect of tensile draw on the "cluster" reflection is shown in Figure 12 and should be compared with Figure 7 for unhydrolyzed polymer. Under moderate strains, 1.75 times, it is seen that the "cluster" reflection is observed mostly in a direction normal to the strain. This is also true in the SAXS scan from fiber where the reflection is principally observed in the equatorial scan. This implies a periodicity which is normal to the fiber axis. Thus, the periodicity associated with this reflection tends to be orthogonal to the periodicity associated with the reflection observed in the meridional SAXS scan of unhydrolyzed fiber. Similar effects of sample orientation have recently been reported for ethylene-methacrylic acid ionomer (23). 

In this section, the metal-cationic salts of copoly(ethylene-methacrylic acid) are called the ethylene ionomers. This ethylene ionomer is one of the well-known commercial ionomers, marketed under the trade name Surlyn by DuPont. Many ethylene ionomers have crystalline and amorphous phases of ethylene chain units as well as polyethylene. Therefore, there is a three-phase structure, with crystalline, amorphous, and ionic aggregate phases this is a unique characteristic of ethylene ionomers compared with other ionomers. Although the ionic aggregate structure of the ethylene ionomer has not been fully established, its structural model is represented5 as shown in Fig. 1. In ethylene ionomers, therefore, it is necessary that some physical properties should be considered by correlating to not only the ionic aggregates but also the crystalline phases. 

Fig. 2. DSC thermograms of the zinc salt of ethylene ionomers after ageing at room temperature for a long time (heating rate lO°C/min). These ethylene ionomers are copoly(ethylene-methacrylic acid) with an acid content of 0.054 and various degrees of neutralization (E-0.054MAA-xZn) x = 0, 0.20, 0.60, and 0.90.

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