Thermal properties and crystallization behavior of ultrafine fully-vulcanized powdered rubber particle toughened polypropylene

Thermal properties and crystallization-behavior of ultrafine fully-vulcanized powdered rubber (UFPR) toughened poly propylene (PP) were studied by Differential scanning calorimetry (DSC) and Wide angle X-ray diffraction (WAXD) measurements. It was found that the fraction of beta-form in the PP crystal increased at first, then sharply deceased up to zero with increasing UFPR content

Blends of Polypropylene and Syndiotactic 1,2-Polybutadiene: Morphology, Crystallization Behaviors and Mechanical Properties

Morphologies, crystallization behavior and mechanical properties of polypropylene(PP)/syndiotactic 1,2-polybutadiene(s-1,2 PB) blends were investigated. Morphology observation shows the well dispersed domains of s-1,2 PB in PP matrix with the rather small domain sizes from 0.1 to 0.5 mu m when the s-1,2 PB content increases from 5% to 20% (mass fraction) in the blends, and the phase structure tends to become co-continuous as s-1,2 PB content further increases.

Sulfonated poly(arylene-co-imide)s as water stable proton exchange membrane materials for fuel cells

A novel sulfonated poly(arylene-co-imide)s were synthesized by Ni(0) catalytic copolymerization of sodium 3-(2,5-dichlorobenzoyl)benzenesulfonate and naphthalimide dichloride monomer. The synthesized copolymers with the - SO3H group on the side-chain of polymers possessed high molecular weights revealed by their high viscosity and the formation of tough and flexible membranes. Because of the introduction of electron donating phenoxy groups into naphthalimide moieties, the hydrolysis of the imide rings was depressed. The resulting copolymers exhibited excellent water stability. The copolymer membranes display no apparently change in appearance, flexibility, and toughness after a soaking treatment in pressurized water at 140 degrees C for 250 h.

Nanostructured bulk novel hard material with "rounded" grains obtained by nanocrystalline "rounded" (W0.5Al0.5)C powders

A novel nano-scaled bulk hard material (W0.5Al0.5)C-Co with "rounded" grains was prepared by nanocrystalline "rounded" (W0.5Al0.5)C powders with "rounded" particle shape in this study. The nano-scaled "rounded" particles do not contain sharp edges, which form local tensile stress concentrations on loading of the composite, thus leading to improved toughness and reduced sensitivity to crack. Nanocrystalline (W0.5Al0.5)C powders with "rounded" particle shape were used as starting materials. X-ray diffraction, scanning electron microscopy, and transmission electron microscopy were used to characterize the samples.

Lanthanum zirconate ceramic toughened by BaTiO3 secondary phase

La2Zr2O7 (LZ) is a promising thermal barrier coating material for the high-temperature applications, which could be significantly toughened by the BaTiO3 piezoelectric phase incorporated into the matrix. The composites of xBaTiO(3)/(l-x)LZ (x=5, 10, 15, 20 vol%, LZ-x-BaTiO3) were densified by means of high-pressure sintering (HPS) under a pressure of 4.5 GPa at 1450 degrees C for 10 min, by which a high relative density above 93% could be obtained.

Convenient preparation of tunably loaded chemically converted graphene oxide/epoxy resin nanocomposites from graphene oxide sheets through two-phase extraction

We report a facile method to create the chemically converted graphene oxide/epoxy resin nanocomposites from graphene oxide sheets through two-phase extraction. Great improvements in mechanical properties such as compressive failure strength and toughness have been achieved for the chemically converted graphene oxide/epoxy resin for a 0.0375 wt% loading of chemically converted graphene oxide sheets in epoxy resin by 48.3% and 1185.2%, respectively. In addition, the loading of graphene is also conveniently tunable even to 0.15 wt% just by increasing the volume of the graphene oxide dispersion.

Covalent functionalization of chemically converted graphene sheets via silane and its reinforcement

Polydisperse, functionalized, chemically converted graphene (f-CCG) nanosheets, which can be homogeneously distributed into water, ethanol, DMF, DMSO and 3-aminopropyltriethoxysilane (APTS), were obtained via facile covalent functionalization with APTS. The resulting f-CCG nanosheets were characterized by FTIR, XPS, TGA, EDX, AFM, SEM, and TEM. Furthermore, the f-CCG nanosheets as reinforcing components were extended into silica monoliths. Compressive tests revealed that the compressive failure strength and the toughness of f-CCG-reinforced APTS monoliths at 0.1 wt% functionalized, chemically converted graphene sheets compared with the neat APTS monolith were greatly improved by 19.9% and 92%, respectively.

Influence of Annealing on Microstructure and Mechanical Properties of Isotactic Polypropylene with beta-Phase Nucleating Agent

The microstructure and mechanical properties of beta-nucleated iPP before and after being annealed at different temperatures (90-160 degrees C) have been analyzed, Annealing induced different degrees of variation in fracture toughness of beta-nucleated iPP samples. namely, slight enhancement at relatively low annealing temperatures (< 110 degrees C) and great improvement at moderate temperatures (120-130 degrees C), whereas dramatic deterioration at relatively high temperatures ( > 140 degrees C) has been observed. The variation of fracture toughness of beta-nucleated iPP is observed to be dependent on the content of beta-NA. Experiments, including scanning electronic microscope (SEM), wide-angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC), small-angle X-ray scattering (SAXS), and dynamic mechanical analysis (DMA), are performed to study the variations of microstructures as well as the toughening mechanism of the beta-nucleated iPP after being annealed.

Toughening effects of poly(butylene terephthalate) with blocked isocyanate-functionalized poly(ethylene octene)

BACKGROUND: Blocked isocyanate-functionalized polyolefins have great potential for use in semicrystalline polymer blends to obtain toughened polymers. In this study, poly(butylene terephthalate) (PBT) was blended with allyl N-[2-methyl-4-(2-oxohexahydroazepine-1 -carboxamido)phenyl] carbamate-functionalized poly(ethylene octene) (POE-g-AMPC).RESULTS: New peaks at 2272 and 1720 cm(-1), corresponding to the stretching vibrations of NCO and the carbonyl of NH-CO-N, respectively, in AMPC, appeared in the infrared spectrum of POE-g-AMPC. Both rheological and X-ray photoelectron spectroscopy results indicated a new copolymer was formed in the reactive blends. Compared to uncompatibilized PBT/POE blends, smaller dispersed particle sizes with narrower distribution were found in the compatibilized PBT/POE-g-AMPC blends. There was a marked increase in impact strength by about 10-fold over that of PBT/POE blends with the same rubber content and almost 30-fold higher than that of pure PBT when the POE-g-AMPC content was 25 wt%.

Evolution of phase morphology of high impact polypropylene particles upon thermal treatment

Solvent fractionation and differential scanning calorimetry (DSC) results show that high impact polypropylene (hiPP) produced by a multistage polymerization process consists of PP homopolymer, amorphous ethylene-propylene random copolymer (EPR), and semicrystalline ethylene-propylene copolymer. For the original hiPP particles obtained right after polymerization, direct transmission electron microscopy (TEM) observation reveals a fairly homogeneous morphology of the ethylene-propylene copolymer (EP) phase regions inside, while the polyethylene-rich interfacial layer observed between the EP region and the iPP matrix supports that EP copolymers form on the subglobule surface of the original iPP particles. Compared with that in original hiPP particles, the dispersed EP domains in pellets have much smaller average size and relatively uniform size distribution, indicating homogenization of the EP domains in the hiPP by melt-compounding. Upon heat-treatment, phase reorganization occurs in hiPP, and the dispersed EP domains can form a multiple-layered core-shell structure, comprising a polyethylene-rich core, an EPR intermediate layer and an outer shell formed by EP block copolymer, which accounts to some extent for the good toughness-rigidity balance of the material.

Effect of the addition of YAG(Y3Al5O12) nanopowder on the mechanical properties of lanthanum zirconate

La2Zr2O7 (LZ) is a promising thermal barrier coating material for the high-temperature applications, which could be significantly toughened by the YAG nanopowder incorporated into the matrix. The composites of xYAG/(1-x)LZ (Y=10, 15, 20 vol. %, LZ-x-YAG) were densified by means of high-pressure sintering (HPS) under a pressure of 4.5 GPa at 1650 degrees C for 5 min, by which a high-relative density above 93% could be obtained. The morphologies of the fractured surfaces were investigated by the scanning electron microscope, and the fracture toughness and Vicker's-hardness of the composites were evaluated by the microindentation. The grain size of the LZ matrix drops significantly with the addition of YAG nanoparticles and the fracture type changes from the intergranular to a mixture type of the transgranular and intergranular in the nanocomposites. The LZ-20-YAG nanocomposite has a fracture toughness of 1.93 MPa m(1/2), which is obviously higher than that of the pure LZ (1.57 MPa m(1/2)), and the toughening mechanism is discussed in this paper.

Application of rare earths in thermal barrier coating materials

Rare earths are a series of minerals with special properties that make them essential for applications including miniaturized electronics, computer hard disks, display panels, missile guidance, pollution controlling catalysts, H-2-storage and other advanced materials. The use of thermal barrier coatings (TBCs) has the potential to extend the working temperature and the life of a gas turbine by providing a layer of thermal insulation between the metallic substrate and the hot gas. Yttria (Y2O3), as one of the most important rare earth oxides, has already been used in the typical TBC material YSZ (yttria stabilized zirconia). In the development of the TBC materials, especially in the latest ten years, rare earths have been found to be more and more important. All the new candidates of TBC materials contain a large quantity of rare earths, such as R2Zr2O7 (R=La, Ce, Nd, Gd), CeO2-YSZ, RMeAl11O19 (R=La, Nd; Me=Mg, Ca, Sr) and LaPO4. The concept of double-ceramic-layer coatings based on the rare earth materials and YSZ is effective for the improvement of the thermal shock life of TBCs at high temperature.

Study of hydrogen-bonded blend of polylactide with biodegradable hyperbranched poly(ester amide)

Polylactide (PLA) was melt blended with a biodegradable hyperbranched poly(ester amide) (HBP) to enhance its flexibility and toughness without sacrificing comprehensive performance. The advantage of using HBP was due to its unique spherical shape, low melt viscosity, and abundant functional end groups together with its easy access. Rheological measurement showed that blending PLA with as little as 2.5% HBP resulted in a 40% reduction of melt viscosity. The glass transition temperature (T-g) of PLA in the blends decreased slightly with the increase of HBP content, indicating partial miscibility which resulted from intermolecular interactions via H-bonding. The H-bonding involving CO of PLA with OH and NH of HBP was evidenced by FTIR analysis for the first time. The HBP component, as a heterogeneous nucleating agent, accelerated the crystallization rate of PLA. Remarkably, with the increase of HBP content, the elongation at break of PLA blends dramatically increased without severe loss in tensile strength, even the tensile strength increased within 10% content of HBP. The stress-strain curves and the SEM photos of impact-fractured surface showed the material changed from brittle to ductile failure with the addition of HBP. Reasonable interfacial adhesion via H-bonding and finely dispersed particulate structure of HBP in PLA were proposed to be responsible for the improved mechanical properties.

Surface-grafted silica linked with L-lactic acid oligomer: A novel nanofiller to improve the performance of biodegradable poly(L-lactide)

A new surface modification method by grafting L-lactic acid oligomer onto the surface silanol groups of silica nanoparticles has been developed. The surface-grafting reaction is confirmed by IR and Si-29 MAS NMR analyses. TEM and SEM results show that grafted SiO2 (g-SiO2) nanoparticles can be comparatively uniformly dispersed in chloroform or PLLA matrix, while the unmodified SiO2 nanoparticles tend to aggregate. The loading of g-SiO2 nanoparticles in poly(L-lactide) (PLLA) matrix greatly improves the toughness and tensile strength of this material. In contrast, the incorporation of un-grafted SiO2 nanoparticles into PLLA leads to the deterioration of its mechanical properties. DSC analysis shows that g-SiO2 nanoparticles can serve as a nucleating agent for the crystallization of PLLA in the composites. SEM characterization shows the tough characteristics and great interfacial combination strength for g-SiO2 (5wt%)/PLLA nanocomposites.

The mechanical and thermal behaviors of glass bead filled polypropylene

Notch Izod impact strength of poly(propylene) (PP)/glass bead blends was studied as a function of temperature. The results indicated that the toughness for various blends could undergo a brittle-ductile transition (BDT) with increasing temperature. The BDT temperature (T-BD) decreased with increasing glass bead content. Introducing the interparticle distance (ID) concept into the study, it was found that the critical interparticle distance (IDc) reduced with increasing test temperature correspondingly. The static tensile tests showed that the Young's modulus of the blends decreased slightly first and thereafter increased with increasing glass bead content. However, the yield stress decreased considerably with the increase in glass bead content. Dynamic mechanical analysis (DMA) measurements revealed that the heat-deflection temperature of the PP could be much improved by the incorporation of glass beads. Moreover, the glass transition temperature (T-g) increased obviously with increasing glass beads content. Differential scanning calorimetry (DSC) results implied that the addition of glass beads could change the crystallinity as well as the melting temperature of the PP slightly.