Cyclo-rubbers

Chlorinated rubbers, synthetic Chlorophene type rubbers Chlorosulfonated polyethylenes Cyclo rubbers, synthetic EPDM polymers... 

Cyclo rubbers, natural Diaphragms, rubber separate and in kits... 

The original compound, maleimide (2,5-dioxo-A -pyrroline), is synthesized by the cyclo-condensation of ammonia and maleic acid. Similarly, primary amine is added to maleic anhydride, followed by cyclocondensation, to form N-substituted maleimide (Fig. 2). This reaction is applied to the preparation of bis-maleimides (BMl) [1]. At first, BMI was used as a crosslinking agent for natural rubber (NR). An o-dichlorobenzene solution of NR was crosslinked by BMI at I08-150°C in the presence of peroxides. The radicals generated from peroxides react with the double bonds of both BMI and NR [ 1 ]. 

Continuous porous polymer rods have been prepared by an in situ polymerization within the confines of a chromatographic column. The column is filled with glycidyl methacrylate and ethylene dimethacrylate monomer mixtures, cyclo-hexanol and dodecanol diluents, and AIBN initiator. They are then purged with nitrogen, stopped, and closed with a silicon rubber septum. The polymerization is allowed to proceed for 6 hr at 70°C with the column acting as a mold (47). 

A 25-ml Schlenk tube was charged with the step 2 product mixture (1.76 or 2.00 g) dissolved in 2 or 9 ml of either THF or toluene. All samples were free radically initiated using either 2,2 -azobis(isobutyrylnitrile) (Vazo 64) or l,l -azobis(cyclo-hexanecarbonitrile) (Vazo 88). Each tube was then sealed with a rubber septum and then degassed by three cycles of freeze-thaw pumping and then heated to 60°C for selected times. After cooling to ambient temperature, the mixture was precipitated in 20 ml petroleum ether and then isolated and washed with cold petroleum ether and the product isolated. 

Cystamine or Cystogen Trade name for hexamethylenetetramine (qv) used in medicine as an antiseptic for the urinary tract, and in the manuf of plastics and as ah accelerator for the vulcanization of rubber. Hexamethylenetetramine can also be nitrated to form th e expl called RDX or Cyclo-nite (See this Volume)... 

An EPDM rubber is produced by the terpolymerisation of ethylene and propylene with a small amount (typically of the order of 5%) of an unconjugated di-olefin. The di-olefins used, include dicyclopentadiene, 1,4-hexadiene, 5-methylene-2-norbornene, 5-ethylidene-2-norbornene and methyl tetrahydroindene, 1,5 cyclo octadiene. A number of other dienes [74,75] have been tried. Infrared spectroscopy [35] is used to find out the ter monomer content. The characteristic peaks for the ter monomer are shown in Table 3.4. In view of the relatively low concentrations, it is probable that ter monomer base units are present largely as isolated units in EPDM but the distribution of propylene and methylene sequences is of considerable interest. 

In concluding the discussion of rubber it may be well to give without further comment a suggested constitution for caoutchouc itself as a polymerized isoprene. The formula suggested by Harries is i-S-di-methyl cyclo octa di-ene. 

The yellow orthorhombic modification of sulfur is the thermodynamically most stable one. The crown-like structure of a-cyclo-Sg was discovered in 1935. fi-Cyclo-Sf, is monoclinic and is formed slowly above 95 °C, the transition temperature of orthorhombic sulfur. The third crystalline modification is y-cyc/o-Sg, which melts at 106.8 C on rapid heating and can be prepared as discussed above. There is a large number of well-studied cyclic oligomers of sulfur here we refer the reader to a standard textbook. When sulfur heated to about 400°C is subjected to quenching the product is polycatenasulfur, which exhibits rubber-like properties. 

Durax . [R.T. Vanderbilt] N-Cyclo-hexyl-2-benzothiazole sulfenamide rubber accelerator. 

BR rubbers or high styrene ESBR rubber. Usually, these rubbers are not compatible [9]. Figure 1.5 shows, for example, the DSC thermograms of SSBR/BR (75/25) samples mechanically blended in an internal mixer at 50°C and solution (cyclo-hexane) blended. The Tg-value of the BR phase (-110°C) is unaffected however, the glass-rubber transition of the SSBR phase is influenced on the low temperature side. The two transition effects clearly present are an indication for the non-compatibility of these two polymers. 

---