Investigation into morphology, microstructure and properties of SBR/EPDM/ORGANO montmorillonite nanocomposites

Rubber compounds based on styrene-butadiene rubber/ethylene propylene diene monomer blends of different compositions (60/40, 70/30, 80/20, 90/10, 100/0) reinforced with 1 wt%, 3 wt%, 5 wt% and 7 wt% organoclay (Cloisite 20A) were prepared on a two roll mill via a vulcanization process and characterized by several techniques. Results of X-ray diffraction showed expansion of the inter-gallery distance, and transmission electron microscopy (TEM) micrographs confirmed that the prepared nanocomposite samples have intercalated and partially exfoliated structures. Cure characteristics showed that, organoclay not only accelerates the vulcanization reaction, but also gives rise to a marked increase of the torque, indicating crosslink density of the prepared compounds increases at the presence of organoclay. Mechanical properties of samples received markedly increase by clay loading due to the good interaction established between nanoclay particles and polymer matrix as it was evidenced by SEM photomicrographs. At the same time, rheological properties showed that addition of nanoclay could improve storage modulus as well as complex viscosity of SBR/EPDM samples. The results of ozone test revealed that the ozone resistance of samples significantly increases as nanoclay or EPDM content increases.     

Thermal rearrangement of some 3-alkyl-2-aryltetrahydro-1,3-oxazine N-oxides. Synthesis of 2-alkyl-7-aryltetrahydro-1,6,2-dioxazepines

Several 2-alkyl-7-aryltetrahydro-1,6,2-dioxazepines 5a-i have been synthesized by a Meisenheimer-type rearrangement of 3-alkyl-2-aryltetrahydro-1,3-oxazine N-oxides 4a-i . These dioxazepines have not been previously described and for the first time compounds with the tetrahydro-1,6,2-dioxazepine ring-system have been made available. The structure assigned to members of this novel heterocycle is based on elemental analysis, infrared, and ¹H nmr spectral evidence. Further definitive evidence for the structure of these heterocycles is provided by an X-ray crystallographic analysis of 5c .     

Synthesis of symmetrical 2,2′,4,4′-tetrasubstituted[4,4′-bioxazole]-5,5′(4H,4′H)-diones and their reactions with some nucleophiles

Several symmetrical 2,2′,4,4′-tetrasubstituted[4,4′-bioxazole]-5,5′(4H,4′H)-diones 1a-f were obtained by dehydrodimerization of 5(4H)-oxazolones 2a-f . The configurations of four were established; one by X-ray crystallography rac- 1c , and three rac- 1a , meso- 1a and rac- 1b by ¹H nmr spectroscopy of their derivatives. Upon being heated, the bioxazolones isomerized, presumably by breakage of the 4,4′-carbon? carbon bond to form free radicals followed by their recombination. The results of a crossover experiment were consistent with a radical nature for this isomerization reaction. Treatment of three of the bioxazolones rac- 1a , meso- 1a and rac- 1c with methanol and amine nucleophiles led to ester and amide derivatives 7–11 of α,α'-dehydrodimeric amino acids.