PMMA-containing blends

Since, at the critical point of a certain polymer, this polymer is always eluted at the same retention time (corresponding to = IX fiU different types of polymer blends containing this polymer as one component may be separated. This is demonstrated in Fig. 26 for PMMA- containing blends. Even chemically very similar blend components, such as poly(cyclohexyl methacrylate) (CHMA) and PMMA were separated. In addition, not only blends of homopolymers, but also blends of copolymers and PMMA may be investigated. Like the homopolymers, poly(styrene-co-acrylonitrile) and poly(styrene-co-methyl methacrylate) (CoStMMA) were eluted in the SEC mode. 

Schultz and Young [1980] prepared homogeneous blends of immiscible PMMA/PS blends by freezing and sublimation. The solutions containing 5 wt% of polymer or polymer mixture were dissolved in naphthalene at 100°C with a magnetic stirrer, under blanket. The hot solu-... 

Mishra et al. [1994] and Bajpai et al. [1994] determined the microhardness of PMMA/PVDF and PMMA/PCTFE blends (Table 11.9) made by solution casting from dimethyl formamide solutions. The solutions containing the two polymers were heated at 110°C for 3 h and were poured into an optically plain glass mold to prepare pellets of the blends. The poured material was annealed at 75°C for 3 h. The samples were cut from the slowly cooled (24 h) pellets for this work. 

Bromine is an effective flame retardant and bromine-containing blends poly(di-bromo-propyl acrylate) with PMMA and PMA) have been studied with this in mind [Grassie et al., 1987 Diab, 1986]. Though the degradation products are those expected from the individual components it has recently been found that high temperature pyrolysis of blends (600°C) containing bromine flame retardants can generate detectable (ppm) amounts of para-dioxins [Luijk and Go vers, 1992]. 

Blends of PMMA and poly(styrene-staf-acrylonitrile), SAN, have been studied by several authors (Naito et al. 1978 Mijovic et al. 1989 Mijovic et al. 1990 Cowie et al. 1991 Cowie et al. 1998 Robertson and Wilkes 2001). Mijovic et al. have investigated blends of PMMA with a commercial SAN sample containing 25 wt% AN, using enthalpy (Mijovic et al. 1989) and stress-relaxation (Mijovic et al. 1990) measurements. Data are shown in Tables 13.5 and 13.6. The authors observed, in common with all other workers, that aging is faster at higher temperatures. No comparison was made with the component polymers, but it was observed that blends rich in SAN relaxed faster than PMMA- rich blends. The aging times used in that work were no more than 150 min. 

Pohjakallio et al. brought new insights for the preparation of bicomponent Langmuir-Schaefer (LS) films, espedaUy those containing blends of immiscible polymers such as PS and PMMA 10 1 and 5 1 (mass ratio) PMMA/PS blend films deposited on silica substrates have been investigated by AFM (topography and phase... 

Pillai and co-workers demonstrated an effective way of using a compatibiliser to improve the PMMA and styrene-butadiene rubber (SBR) system. They created thin films of polymers of poor solubility using silane compatibiliser additives [40] in that work organosilanes containing Cg, Cio, Q2 and Cig aliphatic chains were used in the PMMA/SBR blends. It was found that the compatibiliser effect of organosilane was largely dependent upon the number of carbon atoms in the aliphatic chain. The reasons for that phenomenon was primarily due to the steric effect, as silane-type compounds with different aliphatic chain lengths develop interfacial layers of different thicknesses [40]. 

Figure 1. Ratio Im/Ia of the emission intensity of the naphthyl donor at 336 nm and the anrhryl acceptor at 408 nm from blends containing equal weights of methyl methacrylate copolymers containing 1.2 weights 1-(2-naphthyl) ethyl methacrylate and PMMA containing 1.4 weight of 1-(2-anthryl) ethyl methacrylate. Excitation was at 276 nm, where the naphthalene label absorbs 80% of the incident light. The characteristic distance Ro at which 50% of the absorbed excitation energy is transferred from the naphthyl to the anthryl group is 2.3 nm.

The same authors also studied PMMA/SAN blends where the SAN copolymer contained 25 mol.% AN [35]. The dependence of the volume relaxation rate on blend composition appeared to be consistent with the enthalpic measurements of Mijovic et al. [34] on the same system. In fact, volume relaxation rates were found to be intermediate for the blends compared to the pure components and were composition dependent, except for T — 50 °C. 

Yamamoto and Minamizaki [159] disclose the use of a curable silicone based release agent blended with resin particles which swell or are soluble in organic solvent. Coatings made with such blends can be written on with solvent based inks. For example, an addition cure silicone network containing 20 wt% 0.1 p,m diameter PMMA particles exhibited both good writeability (no ink dewetting and smear free) and a low release force of 10 g/cm for a PSA tape. 

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