PMMA/rubber blends

PMMA degradation determines a general decrease of mechanical performances of the material while the other phenomena may have beneficial effects even if rubber cross-linking can produce a decrease in the strain at break. These mechanisms, however they work, determine a decrease in the strain at break and a slight increase of the yield stress upon further irradiation. The different responses of the system varying the rubber nature is clearly attributable to the different effects of ionizing radiation on the rubber, which affect the final structure of PMMA-rubber blend. 

Figure 6 Effect of rubber particles content on the storage modulus of PMMA/Rubber blends.

Figure 7 Micrographs and linear viscoelastic properties of PMMA/Rubber blends for various values of rubber content emulsion model s predictions.

Figure 4.12 Viscosity of a natural rubber (NR)/poly(methyl methacrylate) (PMMA) polymer blend and predictions of Eq. (4.26) through (4.29) at a shear rate of 333 s . Adapted from Z. Oommen, S. Thomas, C. K. Premalatha, and B. Kuriakose, Polymer, 38(22), 5611-5621. Copyright 1997 by Elsevier.

Mina, M. R, Ania, R, Balta Calleja R and Asano, T. 2004. Microhardness studies of PMMA/natural rubber blends. Journal of Applied Polymer Science 91(1) 205-210. 

Spadaro et al. - polymerized methyl methacrylate (MMA) monomers in the presence of acrylonitrile-butadiene rubber by y-irradiation at a temperature of 70°C. For pure MMA, a total dose of 4 kGy is enough to complete polymerization and further irradiation (6.3 kGy) leads to a degradation of PMMA macromolecules. On the contrary, for PMMA/ABN blends, a higher dose... 

Rubber composites made from NR are used in adhesives. This investigation is concerned with the preparation of rubber blends based on NR and PMMA because incorporation of PMMA into the NR phase may lead to materials with improved strength, clarity and weather resistance and could be used in automotive and other applications. Rubber composites from NR and PSf containing cofibre could be expected to find use in artificial wood applications, cups and picture frames, as shown in Figure 13.53. 

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]. 

Other recent studies which involve and illustrate the power of the FTIR technique include surface studies of PVC systems with PMMA [192] and poly(e-caprolactone) (PCL) [193, 194] PVC with styrene/acrylonitrile copolymers [195] polyester/nitrocellulose [196] EVA copolymer with PVC and chlorinated polyethylene (CPE) [197] and interactions in blends involving p-sulphonated polystyrene [198, 199]. FTIR techniques have been used to map the phase diagram of an aromatic polyamide-poly(ethylene oxide) blend [200], while microscopy-FTIR has been used to obtain information on intermolecular interactions and conformational changes in specific domains in functionalised polyolefins with PVC or polystyrene [201]. Segmental motions and microstructure studies from combined DSC and FTIR measurements have been used to interpret solid-state transitions in miscible rubber blends [202]. 

The most strikiiig observatiou iii the present case is the fact that no sharp edges of the two polymers on the contact region are observed. This contrasts with the finding on glassy poly (methyl methacrylate)/natural rubber (PMMA/NR) blend films [60] prepared in the same way as described above for PS/SBS blends. In Figure 13.5b one can also see that the transition zone between the two polymers is rather smooth. This observation is obviously related to the fact that SBS, being a compatibilizer for the blends of PS with natural and... 

One question of interest at this stage is how would the linear viscoelastic properties be affected if the PS dispersed phase is replaced by an elastic component. The same PMMA used before has been blended with rubber particles over a wide range of PMMA/Rubber composition (95/05, 90/10, 85/15, 80/20, 70/30, and 50/50. As mentioned before the rubber particles consist of a core-shell poly(butylacrylate-co-styrene)-PMMA type. 

Experimental data for 10/90 and 90/10 PS/PMMA blends clearty demonstrate that the increase in blend s elasticity and the longer relaxation times observed in the terminal zone are due to the deformability of the suspended droplets. On the other hand, results obtained for PMMA/Rubber and PS/Rubber blends illustrate limitations of the Palierne model. For these blends, the model does not even qualitatively predict the secondary plateau arising at low frequencies for high rubber contents. The model does not account for particle-particle interactions. For volume fraction of rubber larger than 15 %, the particles form a network-type structure. For rubber particles concentration of 15 % and larger the elasticity of the network structure is satisfactorily described by the percolation theory. For PS/Rubber blends, a network is observed at a particles concentration of 10%. This is not predicted by the percolation theory. 

There has also been active interest in blends of PBT with other polymers. These include blends with PMMA and polyether-ester rubbers and blends with a silicone/polycarbonate block copolymer. 

FIGURE 11.29 Effect of grafted natural rubber content on the mechanical properties of STR5L-PMMA blends at ratios of 50 50 ( ) and 70 30 ( ). (From Suriyachi, P., Kiatkamjomwong, S., and Prasassarkich, P., Rubber Chem. Technol., 77, 914, 2004.)... 

Needless to say, the rheological properties of polymer mixtures are complex and nearly impossible to predict. Figure 4.12 shows the viscosity of a natural rubber (NR)/poly(methyl methacrylate) (PMMA) blend (top curve) as a function of percentage NR [2]. For comparison, the predictions of four common equations are shown. The equations are as follows ... 

On the other hand, some mechanically compatible blends as well as some dispersed two-phase systems have made respectable inroads into the commercial scene. Many of these are blends of low-impact resins with high-impact elastomeric polymers examples are polystyrene/rubber, poly (styrene-co-acrylonitrile) /rubber, poly (methyl methacrylate) /rubber, poly (ethylene propylene)/propylene rubber, and bis-A polycarbonate/ ABS as well as blends of polyvinyl chloride with ABS or PMMA or chlorinated polyethylene. 

Poly(epichlorohydrin), CO rubber (Hydrin), was chosen for various reasons. The one reason was that CO has been shown to be miscible with PMMA by Anderson based upon differential scanning calorimetry (DSC) which showed only one glass transition temperature (T ) for the blend (9). Since T is very sensitive to the disruption of the local structure that results when two polymers are mixed, the existence of a single glass transition temperature is a good indicator of miscibility (10). 

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