Crystals of fractionated trans‐1,4‐polyisoprene (TPI) were grown from amyl acetate solution at two weight fractions, 5.7 × 10−4 and 0.011; for the lower concentration a precooling followed by heating and then crystallization at temperatures in the 10–32°C range was used, while for the higher concentration this method and direct crystallization at a temperature TC in the 0–32°C range were employed. The precooling method yielded samples crystallized in the α form, while direct crystallization led to formation of β‐TPI at low TC and α at higher TC. The value for the DSC endotherm, characteristic of α‐form melting, increased with increasing TC, with a shift to lower values with increasing concentration for precooled samples. A β to α transformation was found to occur for synthetic unfractionated TPI when swollen with amyl acetate at 35°C for 17h. Swelling in n‐butyl acetate for one day at 25°C or 17 h at 35°C also led to this transformation. From experimental results 74°C is chosen as the temperature at which the α and β forms coexist in the bulk, and this is used to calculate the enthalpy of fusion of β‐TPI, yielding a value of 8.6 kJ mol−1.

trans-1,4-Polyisoprene (TPI) fractions with Mn = 4.7 X 103 to 2.5 X 106 and MW/MD = 2.0-1.3 were crystallized from solutions, mainly at a concentration of 1 g/100 cm3, by cooling directly from 100 °C to an (apparent) Tc of -15 to +32 °C, by precooling to 0 °C, redissolving at 35-45 °C, and crystallizing at Tc, and by cooling to 0 °C and heating to 10,20, or 30 °C. Most of the structures obtained were characterized, while suspended in the crystallization liquid, by interference contrast microscopy and with crossed polaroids; the crystalline fraction from the density and the crystal form from X-ray diffraction and differential scanning calorimetry were determined for the dry products. The morphology obtained by direct crystallization was dependent on molecular weight, crystallization temperature, and solvent, with a-and /3-hedrites (sheaves), a-and /S-spherulites, and /3-aggregates of cup-shaped lamellas being found. The precooling method yielded overgrown lamellas in most cases; however, more complex morphologies developed when the thermal history was changed. The density depended on molecular weight, concentration, and crystallization temperature. The crystallinity was mainly a function of crystal form and molecular weight. The equation of Tseng, Herman, Woodward, and Newman was used to explain the molecular weight dependence of the crystallinity at low Mn and to calculate the average number of monomer units per fold and interlamellar traverse. Epoxidation of some TPI structures suspended in amyl acetate at 0 °C was carried out. At high concentrations of the epoxidizing agent, m-chloroperbenzoic acid, the fraction epoxidized approached or exceeded the noncrystalline fraction as obtained from density measurement.

The curing behavior of the epoxy/dicyandiamide/2-methylimidazole system in the presence of montmorillonite clays intercalated with different compounds are analyzed by Fourier transform infrared spectroscopy (FTIR) and with differential scanning calorimetry (DSC). The properties of intercalated clays were analyzed by X-ray diffraction and thermal gravimetric analysis (TGA) and it was obtained that the d-spacing of different intercalated clays follows the order of the siloxane-clay>org-clay>epoxy resin-clay>pristine clay; this trend is consistent with the amount of intercalated chemicals obtained from TGA. The results of FTIR and DSC indicate that the curing exotherms, curing rates, formed functional groups, and curing mechanisms (reaction order) of the epoxy resin system are affected by the curing temperature and the type of intercalated clay used because of the stoichiometric imbalance of reactive groups resulted from the mutual diffusion of epoxy resin constituents and intercalated chemicals. The curing heats of the epoxy resins with different clays are in the order of the epoxy resin-clay> siloxane-clay>org-clay. It is shown that the Kamal model when applied can correctly describe the curing kinetics of the studied epoxy resin/clay systems at 160 and 170 o C.