摘要:

Polymer blends containing poly(phenylene sulfide) (PPS) and liquid crystalline polymer (LCP) of varying compositions were injection molded and tested. Three-point bending tests were carried out on annealed and unannealed samples at various temperatures and strain rates. The time–temperature master curves were constructed by shifting the experimental modulus data at each point of the curves. The increase in bending modulus and reduction of bending strength with increasing LCP content were attributed to the skincore morphology. The time-temperature curves revealed that the bending modulus of the blends can be superimposed over a wide range of temperatures and strain rates.

ISSN:0022-2348    

DOI:10.1080/00222349508215528

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Solution blends of a modified polyacrylonitrile (PAN) with polyurethane (PU) obtained from 4, 4′-diphenylmethane diisocyanate (MDI) and two different types of polyols– i.e., ether-linked polytetramethylene ether glycol (PTEG) and ester-linked polytetramethylene adipate glycol (PTAG) – were prepared inN, N-dimethylformamide (DMF). The domains in the PTAG-PU blends were much finer than those in the PTEG-PU blends. Shift of the soft segment transition temperatures (Tgs) of PU toward lower temperature with increasing PAN was more significant for PTAG-PU blends. Miscibility was also examined through Fourier transform infrared spectra. These showed clear carbonyl peak shifts due to the different types of hydrogen bonding. The PTAG-PU/PAN (30/70) blend had the maximum draw ratio at failure, measured in 100°C water; it was over 2.5 times that of pure PAN.

ISSN:0022-2348    

DOI:10.1080/00222349508215529

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Dihydroxy-terminated polystyrene (PS) macromonomers of various molecular weights were prepared by free-radical polymerization of styrene in the presence of a chain transfer agent, 3-mercapto-l, 2-propanediol. These macromonomers were used for the synthesis of poly(butylene terephthalate) (PBT) grafted with PS (PBT-g-PS). The morphology and glass transition behavior showed the compatibilizing effect of PBT-g-PS in PBT-PS blends. The compatibilizing effect was generally increased up to 10 phr of PBT-g-PS, and some adverse effects were observed above 10 phr.

ISSN:0022-2348    

DOI:10.1080/00222349508215530

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Thermal behavior and morphology of blends prepared by solution casting of mixtures of chitosan and poly(ethylene oxide) were studied by means of differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). The preliminary results indicate that both melting point and crystallinity depend on the composition of the blends, and that they exhibit minimum values when the blend contains 50% chitosan. From the prediction of melting point depression analysis, the compatibility of the blends shows a transition at this specific composition. This conclusion was further confirmed by observation of the morphology.

ISSN:0022-2348    

DOI:10.1080/00222349508215531

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Thermodynamic properties and phase change behaviors of polyethylene glycol (PEG) in blends with cellulose (CELL) were found to be completely different than those of pure PEG. When the CELL fraction of the blend was larger than 5 wt%, PEG within the blend did not melt into a liquid state, as was the case with pure PEG, even at a temperature over 50°C above its melting point. Instead of fusion, a solid-solid phase transition was found in these PEG-CELL blends with an enthalpy as large as 100 J/g.

ISSN:0022-2348    

DOI:10.1080/00222349508215532

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Highly unsaturated rubber, styrene-butadiene rubber (SBR), was sulfonated successfully by sulfuric acid and acetic anhydride as sulfonating agent in a mixed solvent of petroleum ether and methyl ethyl ketone at high concentration, and neutralized with metallic acetate to form ionomer. Melt flow and mechanical properties of the ionomers and their blends with other polymers were studied. The results showed that the SBR ionomers can be melt processed easily in the presence of zinc stearate and that they behave like thermoplastic elastomers. Zinc stearate lowered the melt viscosity represented by the torque value of a Brabender mixer, and increased both the flow activation energy and the tensile strength of the ionomer. Sulfonate content of the ionomer enhanced both the melt viscosity and tensile strength. Type of cations used in neutralization significantly affected the properties of the ionomers. Blends of the ionomer with polypropylene or SBS showed synergistic behavior with respect to tensile strength, whereas those with polystyrene orcis-1,4-polybutadiene exhibited antagonistic behavior.

ISSN:0022-2348    

DOI:10.1080/00222349508215533

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Electron-irradiated specimens of linear polyethylenes, aged at ambient conditions for periods between 79 and 112 months, were examined by electron spin resonance spectroscopy (ESR). Free radicals were found in all irradiated specimens, spin concentrations ranging from 0.5 × 1016spins/g to 3.5 × 1016spins/g and being nearly proportional to the original irradiation dose. For a given polyethylene, the radical concentration rises monotonically with crystallinity, suggesting that the free radicals are trapped in the crystalline phase. This would account for their longevity. At a given irradiation dose and crystallinity, the radical concentration is lower in normal molecular weight polymer than in ultrahigh molecular weight material. This difference may be explicable in terms of tie-chain concentration.

ISSN:0022-2348    

DOI:10.1080/00222349508215534

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Amorphous syndiotactic polystyrene (sPS) films were annealed at 110° and 115°C for 24 h. The annealing at the higher temperature produced the mesomorphic form of sPS, characterized by conformational order, as shown both by the presence of the zigzag band in the infrared spectrum and by the presence of characteristic peaks in the x-ray diffractogram. The crystalline form was not formed at the investigated temperatures. Differential scanning calorimetry of the mesomorphic sample shows that the transformation of the mesophase into the crystalline phase occurs during the heating run. The transport properties of dichloromethane show that the mesophase is impermeable to the vapors at low activity and becomes permeable at higher activities. At low activity it is therefore possible to derive the fraction of impermeable phase, which corresponds to the fraction of mesophase. This fraction was about 50%.

ISSN:0022-2348    

DOI:10.1080/00222349508215535

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The dispersion state of carbon black (CB) particles in a polymeric matrix was found to be affected by such factors as interfacial energy of the CB-polymer interface and the melt viscosity of matrix polymers. At a given CB volume fraction, the electrical conductivity of CB-filled poly(methyl methacrylate) (PMMA) was measured as a function of time at a temperature higher than the glass transition temperature (Tg). At a characteristic time, as a result of the aggregation of CB, networks facilitating electrical conduction were formed and a percolation-like transition was observed. We defined this characteristic time as the percolation time (tp) and estimated the dispersion state of particles by thetp. The effects of interfacial energy of the CB-polymer interface and melt viscosity of the matrix were estimated quantitatively by changing the surface energy of CB and the temperature. The experimental values oftpwere compared to the calculated values using a simple model. The percolation time decreased with increase of interfacial energy and CB content, and increased with the matrix viscosity. The model well explains the dependency as long as the volume fraction of CB is not large and matrix viscosity is neither very small nor very large.

ISSN:0022-2348    

DOI:10.1080/00222349508215536

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The structure and drawability of nylon 6-iodine complexes, prepared from selected concentrations of I2/KI aqueous solution, have been investigated. Four steps of complex formation have been deduced on systematically increasing the concentration of I2/KI solutions in contact with films of nylon 6. Inferences from the results of x-ray diffraction and thermal analyses are the following: (1) At the lowest concentration, the initial crystal phase of nylon 6 is maintained, with the chains merely being displaced by I−3ions, probably lying perpendicular to the nylon 6 chain axis. (2) At intermediate concentration, the crystal consists of two different phases; one is the crystal complex with the longer intermolecular distance caused by I−3the other is the original nylon 6 crystal. The complexed crystal phase develops into two subphases. These are surmised to be complexed with the I−3ions and I−5ions lying parallel to the chain axis. (3) At still higher KI3concentration, the crystal may be complexed with the 1−5ions. The ultimate plasticized crystal is of only one structural phase, likely complexed with the I−5ions. The drawability of complexed nylon 6 is affected sensitively by its structure. The drawing was done by solid-state coextrusion with a high-density polyethylene billet at a temperature close to the highest melting point of the complex. Nylon 6 film which had contained the two subphases resulted in a structure with the highest drawability, providing an uniaxial draw ratio of 48.

ISSN:0022-2348    

DOI:10.1080/00222349508215537

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor