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A detailed study has been undertaken of the mechanisms of stress transfer in a nanocomposite consisting of hexagonal boron nitride (hBN) nanotubes (BNNTs) in a poly-(vinyl alcohol) (PVA) matrix based upon the use of non-resonance Raman spectroscopy. The structure of the BNNTs was characterized by using transmission electron microscopy (TEM) where it was shown that the majority of the nanotubes had 2–5 walls with some having over 10 walls. The structure and mechanical properties of nanocomposites containing up to 1 wt % of both pristine and hydroxyl-functionalized nanotubes (OH-BNNTs) in PVA were investigated. The dispersion of the BNNTs in the nanocomposites was characterized by using a combination of transmission electron microscopy and Raman mapping. The mechanical properties of the nanocomposites were evaluated by tensile testing, and it was found that the Young's modulus, yield strength, and fracture stress all increased on the addition of the BNNTs. A further improvement in the mechanical properties was obtained for nanocomposites containing the OH-BNNTs. The variation of the Young's modulus of the nanocomposites with volume fraction of the BNNTs was evaluated by using the rule of mixtures, and it was shown that the effective Young's modulus (Eeff) of the BNNTs approached 825 ± 100 GPa at low volume fractions. The value of Eeff was found to decrease with increasing BNNT volume fraction as the result of nanotube bundling. By use of nondestructive Raman spectroscopy, stress transfer from the PVA matrix to the BNNTs was evaluated from stress-induced shifts of the hBN Raman G band, enabling the analysis of interfacial adhesion in the nanocomposites. Larger band shifts were obtained for the OH-BNNTs indicating a stronger interface between the BNNTs and the PVA matrix and a better dispersion. A value of 1.34 ± 0.72 was determined from the stress-induced Raman band shifts for the Grüneisen parameter of the BNNTs. In consideration of their efficient reinforcement of a polymer at very low additions and unique electrically insulating and thermally conductive properties, BNNTs are shown to have great potential to be used as nanofillers for composites in a number of applications. [ABSTRACT FROM AUTHOR]

Due to abundant disposable insulation materials causing serious environmental problem, degradable poly (butylene adipate-co-terephthalate) (PBAT) foam is a solution. To enhance the degradation rate and improve supercritical foaming for PBAT, poly (butylene succinate) (PBS) was selected in this work to blend with PBAT. PBAT/PBS foam with foam density lower than 0.1 g/cm3 and cell size smaller than 40 µm was successfully obtained, whose thermal conductivity was only 34 mW/m K and specific compressive strength was over 3000 N m/kg with an extremely fast degradation rate (97% material degraded within 10 days). The designation strategy is as follows: PBS's fully aliphatic hydrocarbon structure ensures faster degradation rate than PBAT; PBS's better molecular chain regularity accelerates crystallization for PBAT/PBS blend which ensures larger strength for blend foams; crosslinking structure and micro-phase separation structure in PBAT/PBS blend ensures better cell growth and hence larger expansion ratio, that is better thermal insulation performance. [Display omitted] • Degradation of PBAT/PBS foam is very fast, 97% weight loss within 10 days. • Specific compressive strength of PBAT/PBS foam is very large, 3000 N m/kg. • PBAT/PBS foam has very good thermal insulation performance, thermal conductivity as low as 34 mW/m K. [ABSTRACT FROM AUTHOR]