Chemical modifications of hydroxyl terminated polybutadiene (HTPB) with hydrogen bond forming functionalities were used as tactics to improve both tensile strength and elongation of polyurethanes (PUs) simultaneously. PUs were prepared using various diisocyanates with modified HTPB in which dinitrobenzene (DNB) groups are attached to terminal carbon atoms. The spectroscopic studies revealed the presence of an additional hydrogen bonding network between DNB and the urethane backbone which resulted into supramolecular cross-linking and was found to be responsible for significant improvement in mechanical properties of HTPB-DNB-PUs. Also, substantial improvement of elongation at break was observed in the case of HTPB-DNB-PUs. Small angle X-ray scattering (SAXS) and thermodynamical studies indicated a strong segmental mixing between the hard and soft segments of HTPB-DNB-PUs. Growth of partial crystalline character in HTPB-DNB-PUs was believed to be responsible for "fibrous-assembly" morphology. In summary, modification of HTPB induced extra cross-linking through supramolecular hydrogen bonding which in turn concurrently enhanced both strength and elongation of PUs.

A novel halogen-free highly cross-linked supramolecular poly(cyclotriphosphazene- co -4,4′-sulfonyl diphenol) (PZS)-functionalized melamine cyanurate (MCA) (MCA@PZS) hybrid nanosheet fire-retardant (FR) was synthesized and thoroughly characterized using scanning electron microscopy, Fourier-transform infrared (FTIR), X-ray diffraction, and X-ray photoelectron spectroscopy analyses. The polyamide 6 (PA6) composites comprising MCA, PZS, and the MCA@PZS hybrids were prepared via the melt-blending technique. The thermogravimetric analysis combined with FTIR and mass spectroscopy revealed that during thermal degradation, the PA6/MCA@PZS composites released less toxic gases and small organic volatile compounds than the neat PA6 and composites containing MCA or PZS solely. Moreover, compared to neat PA6, the PA6 composite with a 5 wt % MCA@PZS hybrid exhibited enhanced fire retardation properties, with a 29.4 and 32.1% decrease in the peak heat and total heat release rates, respectively. Besides, the PA6 composites with MCA@PZS-5% content achieved a V-0 rating in the UL-94 test. Finally, based on the obtained results from gaseous and condensed phases, the possible mechanism responsible for improved FR properties of the PA6/MCA@PZS composites was proposed.

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This article reports the effects of the characteristics and selective localization of nanofillers on the morphology development and rheological properties of melt-processed polylactide/poly(butylene adipate-co-terephthalate) (PLA/ PBAT) blend composites. Four types of nanofillers (1 wt%) are used: nanoclay (Cloisite30B [C30B]), carbon nanotubes (CNTs), nanosilica, and graphene oxide (GO). Transmission electron microscopy studies reveal that C30B is localized mainly at the PLA/PBAT interface, whereas silica, GO, and CNT are localized in PBAT droplets, although some CNTs also appear toward the interface inside the PBAT. Despite their selective localization inside the PBAT, CNTs are found to be the most effective particles for droplet size reduction, whereas silica nanoparticles are ineffective. The CNT bundles recoil during melt blending, and eventually, their breakage facilitates droplet breakup. The effects of nanofiller localization and annealing under dynamic shear on the blend morphologies are also explored through rheological analysis. The results show an anomalous relationship with the morphologies of the composites. It is also found that both coalescence and thermal degradation are involved in the annealing process of the blends. Interestingly, the CNT-filled composites may have been transformed into co-continuous-like structures during annealing, unlike the other blends studied here.

Preparation of stable, free-standing elastic film with hydrophobic surface from water dispersible polyurethanes (WDPUs) is a challenging task. Here, we have prepared WDPUs from polybutadiene based diols and the resulting PU films are satisfying the requisites. Two types of diols namely hydroxyl terminated polybutadiene (HTPB) and terminal functionalized HTPB with dinitrobenzene (DNB) [HTPB-DNB] were used to make WDPUs and the effects of diol structures were investigated. The synthesized WDPUs displayed particle morphology with size in the range of ~130-270 nm and more than one year storage stability. WDPUs yielded stable and free standing films upon curing and the resulting films showed high thermal and mechanical stabilities. The contact angle of the films is in the range of ~ 80-100° attributing the hydrophobic nature of the surface. Hard segment content of the PU was varied from 30-40 % (by weight) to tune the properties of WDPUs and the resulting films.