Polyisoprene blends

Els and McGill [48] reported the action of maleic anhydride on polypropylene-polyisoprene blends. A graft copolymer was found in situ through the modifier, which later enhanced the overall performance of the blend. Scott and Macosko [49] studied the reactive and nonreactive compatibilization of nylon-ethylene-propylene rubber blends. The nonreactive polyamide-ethylene propylene blends showed poor interfacial adhesion between the phases. The reactive polyamide-ethylene propylene-maleic anhydride modified blends showed excellent adhesion and much smaller dispersed phase domain size. 

Static H 2D NOE spectroscopy was applied in a first experiment showing that the technique can be used to measure inter-chain interactions [44], This work was then continued by applying the technique under MAS to investigate the inter-molecular interactions responsible for the miscibility in polybutadiene/polyisoprene blends above the Tg [45]. It was shown that intermolecular association can be probed by this technique and the results reveal the existence of weak intermolecular interactions between the polyisoprene methyl group and the vinyl side chain of the polybutadiene. 

The substantial work on polystyrene/polybutadiene and polystyrene/ polyisoprene blends and diblock and triblock copolymer systems has lead to a general understanding of the nature of phase separation in regular block copolymer systems (5,6). The additional complexities of multiblocks with variable block length as well as possible hard- and/or soft-phase crystallinity makes the morphological characterization of polyurethane systems a challenge. 

Bhowmick et al. [1986] investigated properties of cis- and trans-polyisoprene blends (cPI/tPI), with a rather cursory look at the effect of gamma irradiation (Table 11.9). The blends consisted of guayule mbber (cPI) and synthetic tPI (Trans-PIP from Polysar). The blends were prepared by mixing the two polymers, along with the typical... 

When the respective component glass transition temperatures are close, the blend Tg is not a useful measure of blend homogeneity. In fact, excess mixing volumes and specific interactions can cause anomalous behavior. The Tg of such a blend can be lower (as seen in polychloroprene/epoxidized polyisoprene blends (McGrath and Roland, 1994)) or higher (as seen in polylepichlorohydrin/polyvinylmethylether blends (Alegria et al., 1995)), than Tg of either neat component. In blends of polymers having nearly equivalent... 

Peng, Z. L., Olson, B. G., Srithawatpong, R., McGervey, J. D., Jamieson, A. M., Ishida, H., Maier, T. M., and Halasa, A. R, Study of free volume in high vinyl-polybutadiene/cis-polyisoprene blends by positron annihilation lifetime spectroscopy, J. Polym. Sci. Polym. Phys., 36, 861-871 (1998). 

RAM Ramachandrarao, V.S., Vogt, B.D., Gupta, R.R., and Watkins, J.J., Effect of carbon dioxide sorption on the phase behavior of weakly interacting polymer mixtures solvent-induced segregation in deuterated polybutadiene/polyisoprene blends, J. Polym. Sci. PartB Polym. Phys., , , U, 2003,... 

Zhang, R. Y., H. Cheng, C. G. Zhang, T. C. Sun, X. Dong, and C. C. Han. 2008. Phase separation mechanism of polybutadiene/polyisoprene blends under oscillatory shear flow. Macromolecules 41 6818-6829. 

In addition to such qualitative interpretation of SALS data, quantitative data could be extracted, i.e. the reduced wave number and the reduced maximum intensity, which allowed to elucidate a nonlinear pathway according to which the initial structures, which had developed in a first-step process, relaxed and transformed toward an equilibrium structure after a second step. " A similar work was reported by Narh " who also worked on polybutadiene/ polyisoprene blends. 

Figure 21.8 Time evolution of the LS profile of a polybutadiene/polyisoprene blend.

Laeuger Joerg, Lay Rainer, Maas Swen, and Gronski Wolfram. Structure development of a polybutadiene/polyisoprene blend during spinodal decomposition. Comparison between light scattering and optical microscopy. Macromolecules. 28 no. 20 (1995) 7010-7015. 

Figure 2.35. DSC curves of polybutadiene-polyisoprene blends recorded at a cooling rate of 15 °C/min. The blends had different polybutadiene (PBD) contents the PBD mass percentages are indicated at each curve. A single glass transition was recorded for every sample, with depending on the compoisition. The single glass transition indicates miscibility. [From Fiale and Bair (1997) reprinted with permission of Elsevier. ...

Hiller et al. demonstrated the separation and microstructural characterization of polyisoprene blends consisting predominantly of 3,4- and... 

Baboo, M., Dixit, M., Sharma, K., and Saxena, N.S. (2010) Activation energy and thermo-mechanical properties of trons-polyisoprene and liquid cis-polyisoprene blends. Thermochim. Acta, 502, 47-50. 

Heffner, S.A. and Mirau, PA. (1994) Identification of intermolecular interactions in 1,2-polybutadiene/polyisoprene blends. Macromolecules, 27 (25),... 

B. G. Soares, F. Gubbels, R. Jerome, and Ph. Teyssie, Electrical Conductivity in Carbon Black-Loaded Polystyrene-Polyisoprene Blends. Selective Localization of Carbon Black at the Interface, Polym. Bull. 35, 223-228 (1995). 

Walker, T.A., Raghavan, S.R., Royer, J.R. et al. (1999) Enhanced miscibility of low-molecular-weight polystyrene polyisoprene blends in supercritical co2. Journal of Physical Chemistry B, 103,5472-5476. 

With less than 3.3 wt% CO2 sorption, the miscible blend of poly(deuterated styrene) and PVME phase separated at 115 °C lower than the control blend [73]. The exposure of the miscible PMMA/PVF2 blend to increasing CO2 pressure showed an increase in xu to zero and the onset of phase separation (at 35 °C) [74]. At high CO2 pressure, PVF2 crystallization occurred within the PMMA-rich matrix. The upper critical solution temperature of poly(dimethyl siloxane)/poly(ethyl methyl siloxane) showed an increase with increasing CO2 pressure [75]. It was noted that high pressure He (with very low solubility) yielded a decrease in the ucst. The sorption of modest levels of CO2 (up to 160 bar) decreased the lower critical solution temperature of deuterated polybutadiene/polyisoprene blends [76]. Each of these examples shows a decrease in miscibility with increasing CO2 pressure. 

Soares BG, Gubbels F, Jer6me R, Teyssie P, Vanlathem E, Deltour R. Electrical conductivity in carbon black loaded polystyrene-polyisoprene blends selective localization of carbon black at the interface. Polym Bull 1995 35 223-228. 

Meijer HEH, Janssen JMH (1994) Mixing of immiscible liquids. In Manas-Zloczower I (ed) Mixing and cmnpounding of polymers. Hanser/Gardner Publications, New York, p 85 Narh KA (1996) The effect of shear flow on phase behavior of polybutadiene/polyisoprene blends. Adv Polym Technol 15 245... 

Dalnoki-Veress K, Forrest JA, Stevens JR, Dutcher JR. Phase separation morphology of thin films of polystyrene/polyisoprene blends. J Polym Sci B 1996 34 3017-24. 

Figure 3.34. Dependence of Ig x (1), AU (2), T., (3) and tg 5, (4) on the dosage of oligomer cdi in cis-polyisoprene blended with trioxyethylene-dimetacrylate at the testing frequency 1 kHz. The vertical arrow corresponds to the phase transition concentration at the preparation temperature of tested samples.

Producers of bottle teats requiring improvement in colour of the finished product with minimal loss of transparency have found a suitable compromise in using compounds based upon synthetic high cis-polyisoprene blended with a smaller amount of pale crepe which has the effect of solubilising any residual catalyst in the synthetic polymer. 

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