The toughness of epoxy-poly(butylene terephthalate) blends

Blends containing 5% poly(butylene terephthalate) (PBT) in an anhydride-cured epoxy with three different PBT morphologies were studied. The three morphologies were a dispersion of spherulites, a structureless gel and a gel with spherulites. The average fracture toughnesses, K Ic , and fracture energies, G Ic , for those morphologies were 0.83, 2.3 and 1.8 MPa m 1/2 and 240, 2000 and 1150 J m −2 , respectively. These values should be compared with the values of 0.72 MPa m 1/2 and 180 J m −2 , respectively, for the cured epoxy without PBT. The elastic moduli and yield strengths in compression for all three blend morphologies remained essentially unchanged from those of the cured epoxy without PBT, namely, 2.9 GPa for the modulus and 115 MPa for the yield strength. The fracture surfaces of the cured spherulitic dispersion blends indicate the absorption of fracture energy by crack bifurcation induced by the spherulites. The fracture surfaces of the cured structureless gel blends indicate that fracture energy was absorbed by matrix and PBT plastic deformation and by spontaneous crack bifurcation. But phase transformation of the PBT and anelastic strain of the matrix below the fracture surfaces may account for most of the large fracture energy of the cured structureless gel blends.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44733/1/10853_2004_Article_BF00366876.pd

SYNTHESIS AND CHARACTERIZATION OF HIGHLY CONDUCTING, ENVIRONMENTALLY STABLE, IODINE COMPLEXES OF A SOLUBLE POLY N-METHYL 3,3' CARBAZOLYL

Le poly N-methyl 3,3' carbazolyl (PC) peut être préparé de la façon suivante : tout d'abord un agent di-Grignard est préparé à partir de 3,3' di-bromo N-méthyl carbazole et de magnésium activé. Cet agent est ajouté à une suspension de tétrahydrofurane contenant une quantité catalytique d'un complexe de nickel. Le PC jaunâtre obtenu par cette réaction, est soluble dans plusieurs solvants "accepteurs" tels que le nitrobenzène. Des films transparents sont obtenus, et le dopage avec I2 et Br2 peut être effectué facilement, rendant les films noirs et résistants. Les semiconducteurs (PC) à dopage complet contenant un tome I par carbazole monomère avaient des conductivités jusqu'à 1 ohm-1cm-1 avec une énergie d'activation de conduction en courant direct de 0,172 eV. Comme le spectre d'absorption des films dopés avec I2 ne présente pas de raies entre 0,3µ et 25µ, ces propriétés électriques suggèrent que le transport des charges dans ces matériaux amorphes se fait par "hopping". Les radicaux-cations du carbazole sont suffisamment stables dans les complexes pour maintenir inchangée cette conductivité électrique, exposés à l'air à 25°C, durant au moins un mois.Poly N-methyl 3',3 carbazoly (PC) can be prepared by forming the di-Grignard reagent of 3',3 dibromo N-methyl carbazole with highly activated magnesium and subsequently adding this reagent to a tetrahydrofuran suspension containing a catalytic amount of nickle complex. The tan yellow PC isolated from this reaction mixture was soluble in a number of "acceptor" type solvents such as nitrobenzene. Thin, clear yellow films could be cast and were easily doped with I2, Br2 to form tough black films. Completely doped PC semiconductors containing one I atom per carbazole monomer unit, exhibited conductivities as high as 1 ohm-1cm-1 with an activation energy for D.C. conduction of 0.172 eV. Together with the featureless absorbance spectrum shown by the I2 doped films from 0.3µ to 25µ these electrical properties suggest hopping as the charge transport mechanism in these amorphous materials. The carbazole radical cations were sufficiently stable in the complexes to maintain this electrical conductivity unchanged in room air at 25°C for at least 1 month

IMECE2002-39367 PHOTOPOLYMERIZABLE LIQUID CRYSTAL MONOMER-OXIDE NANOPARTICLE COMPOSITES

ABSTRACT Methacrylate and acrylate terminated monomers can be rapidly polymerized to polymer glasses useful in biomaterials, photolithography and rapid prototyping, optical coatings and composites. Unfortunately, polymerization shrinkage results in loss of tolerance and the development of internal stresses which can be especially critical in the case of highly crosslinked glasses. Structurally complicated oligomeric mixes of dimethacrylate monomers that exhibit a nematic liquid crystal to isotropic transition above room temperature have been synthesized in a low cost one pot synthesis to surmount the problem of polymerization shrinkage and the propensity of single component monomers to crystallize from the liquid state. Photopolymerization from the ordered liquid crystal state into a less ordered glass minimizes volumetric shrinkages to between 1-2% at greater than 90% polymerization conversion. These polymer glasses exhibited elastic bending moduli of 1.2 GPa to 1.5GPa, fracture strengths of 70-100MPa and fracture toughness o

Comparison of multimodal annotation tools: Workshop report

Rohlfing K, Loehr D, Duncan S, et al. Comparison of multimodal annotation tools: Workshop report. Gesprächsforschung. 2006;7

Structural and mechanical behavior of layered zirconium phosphonate as a distributed phase in polycaprolactone

Mixed-surface octyl/methoxyundecyl Α-zirconium phosphonates (ZrPs) were investigated as distributed nanoscale fillers, in concentrations up to 50% w/w, for the purpose of increasing the elastic modulus and yield strength of polycaprolactone (PCL) without a meaningful reduction of its ductility. The volumetric nanoparticle loadings were estimated to be over 70% higher than those in nanocomposites with comparable weight fractions of nanoclay. The mechanical properties of the ZrP/PCL nanocomposite were evaluated with tensile, flexural, and dynamic mechanical testing methods. Nanocomposites containing 5% w/w ZrP showed significant increases in both the tensile yield stress and elastic modulus without any loss of ductility versus the unfilled polymer. Layer delamination from the ZrP tactoids was minimal. Kinetic barriers and the strong interlayer attraction between the ZrP surfaces limited intercalative penetration of the ZrP tactoids. ZrP loadings of 20% w/w or more resulted in the agglomeration of tactoids, leading to defect structures with a loss of strength and, at the highest loading, ductility. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/63549/1/30501_ftp.pd