Polyisoprene modifier

Amorphous (most likely atactic) 3,4-polyisoprene of 94—100% 3,4-microstmcture was prepared with a (C2H 3A1—Ti(0—/ -C Hy) catalyst (11). Crystalline 3,4-polyisoprene containing about 70% 3,4-units and about 30% i7j -l,4-microstmcture was prepared using a catalyst derived from iron acetyl acetonate, trialkyl aluminum, and an amine in benzene (37). However, this polyisoprene contained gel and was obtained in poor yield. Essentially gel-free crystallizable 3,4-polyisoprene of 70—85% 3,4-microstmcture with the remainder being cis-1,4 microstmcture was prepared in conversions of greater than 95% with a water-modified tri alkyl aluminum, ferric acetyl acetonate, and 1,10-phenanthroline catalyst (38). The 3,4-polyisoprene is stereoregular and beheved to be syndiotactic or isotactic. 

The glass transition temperatures (Tg) of both modified and unmodified PSs were determined by DSC analysis, and thermomechanic analysis was controlled by TMK. The results are given in Table 8. It is seen from Table 8 that the highest glass transition temperature (410 K) was obtained with chlorohydrinated PS and that of the lowest (370 K) with olefinic PS. The lowest glass transition temperature in the alkenylated PS caused to elasticity properties on polybutadien and polyisopren fragments. 

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. 

A number of other polymers have the characteristics of TPE and some are available commercially, such as (1) 1,2-polybutadiene, (2) tran -polyisoprene (PI), (3) modified polyethylene (PE) (e.g., ethylene vinyl acetate [EVA] and ethylene ethyl acrylate [EEA]), (4) nonhydrocarbon elastomer-based TPEs, (5) metallocene elastomers/TPEs (MEs/TPEs), and (6) graft copolymeric TPEs. 

Microstructure variation in both polybutadiene and polyisoprene polymers has been realized by using alkyllithium initiators in the presence of polar modifiers. 

Figure 13.1 13C spin-lattice relaxation times (nTl) for methylene carbons in bulk polyisoprene at two different field strengths (62.5 (O) and 25.15 ( ) MHz) as a function of inverse temperature. The lines are the best fits of the data to the theory of Dejean de la Batie and co-workers [24] (long dashes) and for the modified relaxation function described in reference [27] (dotted lines)... 

The physical properties of polyisoprenes produced with separated i-Bu3Al solids and their modified versions are listed in Table VI. These systems appear to give polymers with somewhat higher inherent viscosities than observed before with unseparated catalysts. No significant changes in micro-structure of the polymers were noticed between the various systems. 

McFIugh MA, Park IFI, Reisinger JJ, Ren Y, Lodge TP, Hillmyer MA. Solubility of CF2-modified polybutadiene and polyisoprene in supercritical carbon dioxide. 

Esterified polystyrene-co-maleic anhydride Polyethylene-co-propylene Poly(ethylene-co-propylene diene-modified) Poly(ethylene-co-propylene-co-olefin diene-modified) Hydrogenated polystyrene-co-butadiene Hydrogenated polystyrene-co-isoprene Hydrogenated polyisoprene. 

Values for Polymer and Model Compounds. 1,4-Polyisoprene and 1,4-polybutadiene are so sufficiently reactive toward singlet oxygen that we can conveniently obtain / -values by three methods (a) from oxygen-uptake rates by photosensitized oxidation at different polymer concentrations (b) by the initial disappearance rate of rubrene on photooxygenation of solutions with and without polymer (or model olefin) and (c) for 1,4-polyisoprene, by the amount of rubrene consumed upon addition of aliquots of triphenyl phosphite ozonide in the presence and absence of olefin or polymer. The treatment of data from methods (b) and (c) was modified to give /3-values directly from the following equations ... 

Photoactive Additives.—Ferric compounds, in particular, the chloride, continue to attract much interest as photosensitizers for thermoplastics. " From e.s.r. work the mechanism appears to involve a redox reaction resulting in the formation of active hydroxy-radicals. Photodegradable polyethylene film has been developed by doping it with radiation-modified atactic polypropylene and hydroxyethyl-ferrocene. Several workers have studied the dye-sensitized photo-oxidation of polyisoprene and di-n-butyl sulphide embedded in Augustyniak and... 

On the other hand, changes in the recipes of alkali metal polymerizations frequently make appreciable changes in the microstructures of the resultant polymers (2, 10, 12). Thus, sodium polybutadiene, or sodium polyisoprene, has a microstructure different from that of the corresponding potassium-catalyzed polymer. It also has been established that promoters or modifiers like dioxane or dimethoxytetraglycol affect the microstructure in these alkali metal catalyzed systems. One further example is afforded by the Alfin catalyst, which is apparently related to alkali metal catalysts but which gives a polybutadiene or polyisoprene with a microstructure very different from that of the corresponding alkali metal polymers. 

If the above test is positive, the sample may be further subjected to a modified Weber color test for polyisoprenes. For this test, an acetone-extracted polymer (0.05 g) is dissolved or suspended in carbon tetrachloride, treated with a little solution of bromine in carbon tetrachloride and heated in a water bath to remove excess bromine. The residue is then warmed with a little phenol. In the presence of polyisoprenes, the solid or the solution turns violet or purple and gives a purple solution with chloroform. The test is also positive for natural rubber and butyl rubber. 

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