New semicrystalline polyimide/oligoimide blends, designated for matrices in carbon fiber-reinforced composites, were developed. A specific advantage of the proposed polyimides is their ability to crystallize from the melt, therein retaining their crystallinity throughout the manufacturing process. The generation of crystallinity after melting, referred to as recrystallization, was investigated here as affected by blending the polyimides with oligoimides of a similar chemical structure. Based on thermal analysis and enthalpy measurements, comparative X-ray diffraction analyses, and polarized light microscopy of hot-stage-controlled crystallization, the recrystallization ability was determined for five different oligoimides. In some cases, the addition of oligoimides, both amorphous and crystalline, resulted in complete recrystallization. The main contribution of the oligoimides is suggested to be through plasticization, allowing segmental chain mobility during crystallization, and not via nucleation. A similar effect was obtained by lowering the molecular weight of the polyimide; this, however, generates mechanical property reduction, rendering the polyimide irrelevant to composite materials. Finally, it was shown that crystallization was also enhanced by carbon fibers, serving as a nucleating agent and generating transcrystallization.

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The current image by Svetlana Viktorovna Kononova, Denis Sapegin, and colleagues represents phase heterogeneity between sulfonated polyimide and poly(amide-imide) polymer phases in the composite film with 7:3 polyimide to poly(amide-imide) weight ratio. Most likely, in this composite, a three-dimensional crystallizing network of polyimide is formed around poly(amide-imide) which is to form an amorphous phase. This assumption was confirmed by the data of the energy-dispersive analysis since it is in the region of the network structure sulfur atoms were detected, which are present in this composite only in the structure of sulfonated polyimide. ARTICLES 48159 Bio-based β-myrcene-modified solution-polymerized styrene-butadiene rubber for improving carbon black dispersion and wet skid resistance

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In this work, the precipitation of a thin layer of a polymer solution was proposed to imitate the process of asymmetric membrane formation by a non-solvent induced phase separation (NIPS) technique. The phase inversion within the thin (<500 μm) and bulk (~2 cm) layer of polyamic-acid (PAA) in N-methyl-2-pyrrolidone (NMP) by using water as non-solvent was considered. It was shown that polymer films formed within the “limited” layer of polymer solution showed a good agreement with the morphology of corresponded asymmetric flat-sheet membranes even in the case of three-component casting solution (PAA/NMP/EtOH). At the same time, the polymer films formed on the interface of two bulk phases (“infinite” regime) did not fully correspond to the membrane structure. It was shown that up to 50% of NMP solvent in PAA solution can be replaced by ethanol, which can have a renewable origin. By changing the ethanol content in the casting solution, the average size of transport pores can be varied in the range of 12–80 nm, and the liquid permeance from 16.6 up to 207 kg/m2∙h∙bar. To summarize, the precipitation of polymer solution within the thin layer can be considered a prompt technique and a powerful tool for fast screening and optimization of the complex composition of casting solutions using its small quantity. Furthermore, the prediction of membrane morphology can be done without casting the membrane, further post-treatment procedures, and scanning electron microscopy (SEM) analysis.

On the basis of pyromellitic dianhydride, p phenylenediamine, and poly(butylene adipate) diol (M n = 1 × 10 3 ) and poly(ethylene adipate) diol (M n = 1 × 10 4 ) taken at a molar ratio of 10 : 1, initial samples of multiblock poly(ester imide) and its composites with nanoparticles of two types-zirconia ZrO 2 surface treated with γ aminopropyltriethoxysilane and zirconia doped with yttria (Y 0.03 Zr 0.97 O 1.985 )-are synthe sized. Nanoparticles are introduced into the polymer matrix at the stage of synthesis of the poly(ester imide) prepolymer. The mechanical properties of films of poly(ester imide) and its nanocomposites are determined under static and dynamic testing conditions, and the permeabilities and separation selectivities of corre sponding solid films for mixtures of aromatic and aliphatic hydrocarbons (toluene-n octane and benzenecyclohexane) of various compositions are measured under pervaporation testing conditions. It is shown that the different mechanical and pervaporation properties of film samples are due to the presence of zirconia based nanoparticles.