Polyamide 6 (PA6)/multi‐walled carbon nanotubes (MWCNT) nanocomposites were produced by diluting a masterbach containing 20 wt % nanotubes using melt mixing. The influence of the addition of well dispersed MWCNT (as indicated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM)) on the thermal transitions, and crystallization behavior of the PA6 matrix is investigated. Differential scanning calorimetry (DSC) results show a reduction in heat capacity jump at the glass transition which is interpreted by an immobilized interfacial layer near the nanotubes. Furthermore, both DSC and X‐ray diffraction (XRD) measurements indicate that nanotubes favor the formation of the α crystalline form of PA6. These findings are correlated with the observed improvement of the storage modulus as revealed by dynamic mechanical thermal analysis (DMTA). Additionally, a new crystallization peak appears when MWCNT are added, and is attributed to the formation of a different morphology of the same type crystallite around the nanotubes walls (trans‐crystallinity). Finally, water sorption measurements show an increase of water content, normalized to the amorphous polymer fraction, in the nanocomposites. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 764–774, 2009

A series of seven fast-biodegrading aliphatic polyesters were prepared from 1,3-propanediol and aliphatic diacids with increasing number of methylene units (x). Melting points decreased from PPSu to PPAd and then increased again to PPAz and PPSeb. Crystallization rates and thermal stability increased steadily with increasing x. Glass transition temperatures decreased steadily to PPPim and subsequently increased. Enzymatic degradation of the polymers in the presence of a mixture of Rhizopus delemar and Pseudomonas cepacia lipases was much faster than that of poly(epsilon-caprolactone). All the polyester specimens were almost disintegrated within 36 h. PPSub exhibited the fastest enzymatic hydrolysis rates, PPAd and PPSuc the slowest.

No abstract

Abstract. Nanocomposites were fabricated based on diglycidyl ether of bisphenol A (DGEBA), cured with triethylenetetramine (TETA) and filled with: a) high conductivity carbon black (CB) and b) amino-functionalized multiwalled carbon nanotubes (MWCNTs). The full dynamic mechanical analysis (DMA) spectra, obtained for the thermomechanical characterization of the partially cured DGEBA/TETA/CB and water saturated DGEBA/TETA/MWCNT composites, reveal a complex behaviour as the !-relaxation appears to consist of more than one individual peaks. By employing some basic calculations along with an optimization procedure, which utilizes the pseudo-Voigt profile function, the experimental data have been successfully analyzed. In fact, additional values of sub-glass transition temperature (T i ) corresponding to subrelaxation mechanisms were introduced besides the dominant process. Thus, the physical sense of multiple networks in the composites is investigated and the glass transition temperature T g is more precisely determined, as the DMA !-relaxation peaks can be reconstructed by the accumulation of individual peaks. Additionally, a novel term, the index of the network homogeneity (IH), is proposed to effectively characterize the degree of statistical perfection of the network.

No abstract