| 1. |
- Andersson, S. Peter
(författare)
-
Pressure and volume dependence of thermal conductivity and isothermal bulk modulus up to 1 GPa for poly(isobutylene)
- 1998
-
Ingår i: Journal of Polymer Science Part B. - : John Wiley & Sons. - 0887-6266 .- 1099-0488. ; 36:10, s. 1781-1792
-
Tidskriftsartikel (refereegranskat)abstract
- The thermal conductivity λ and heat capacity per unit volume ρcp of poly(isobutylene)s, one 2.8 in weight average molecular weight and one 85 kg mol-1 in viscosity average molecular weight (PIB-2800 and PIB-85000), have been measured in the temperature range 170-450 K at pressures up to 2 GPa using the transient hot-wire method. At 297 K and atmospheric pressure, λ = 0.115 W m-1 K-1 for PIB-2800 and λ = 0.120 W m-1 K-1 for PIB-85000. The bulk modulus BT has been measured in the temperature range 170-297 K up to 1 GPa. At atmospheric pressure, the room temperature bulk moduli BT are 2.0 GPa for PIB-2800 and 2.5 GPa for PIB-85000 with dBT/dp = 10 for both. These data were used to calculate the volume dependence of λ,g = -(∂λ/λ / ∂V/V)T.At room temperature and atmospheric pressure (liquid phase) we find g = 3.4 for PIB-2800 and g = 3.9 for PIB-85000, but g depends strongly on temperature for both molecular weights. The difference in g between the glassy state and liquid phase is small and just outside the inaccuracy of g of about 8%. The best predictions for g are given by the theoretical model of Horrocks and McLaughlin. We have found that PIE exhibits two relaxations, where one is associated with the glass transition. The value for dTg/dp at atmospheric pressure (for the main glass transition) is about 0.21 K MPa-1 for both molecular weights.
|
|
| 2. |
- Andersson, S. Peter, et al.
(författare)
-
Volume dependence of thermal conductivity and bulk modulus for poly(propylene glycol)
- 1998
-
Ingår i: Journal of Polymer Science Part B. - : John Wiley & Sons. - 0887-6266 .- 1099-0488. ; 36:2, s. 345-355
-
Tidskriftsartikel (refereegranskat)abstract
- The thermal conductivity λ and heat capacity per unit volume of poly(propylene glycol) PPG (0.4 and 4.0 kg.mol-1 in number-average molecular weight) have been measured in the temperature range 150-295 K at pressures up to 2 GPa using the transient hot-wire method. At 295 K and atmospheric pressure, λ = 0.147 W m-1K-1 for PPG (0.4 kg.mol-1) and λ = 0.151 W m-1K-1 for PPG (4.0 kg.mol-1). The temperature dependence of λ is less than 4 x 10-4 W m-1K-2 for both molecular weights. The bulk modulus has been measured in the temperature range 215-295 K up to 1.1 GPa. At atmospheric pressure, the room temperature bulk moduli are 1.97 GPa for PPG(0.4 kg.mol-1) and 1.75 GPa for PPG (4.0 kg.mol-1). These data were used to calculate the volume dependence of λ, g = -((∂λ/λ)/(∂V/V))T. At room temperature and atmospheric pressure (liquid phase) we find g = 2.79 for PPG (0.4 kg.mol-1) and g = 2.15 for PPG (4.0 kg.mol-1). The volume dependence of g, (∂g /∂ log V)T varies between -19 to -10 for both molecular weights. Under isochoric conditions, g is nearly independent of temperature. The difference in g between the glassy state and liquid phase is small and just outside the inaccuracy of g of about 8%. The theoretical model for λ by Horrocks and McLaughlin yields an overestimate of g by up to 120%.
|
|
| 3. |
- Andersson, S. Peter, et al.
(författare)
-
Volume dependence of thermal conductivity and isothermal bulk modulus up to 1 GPa for poly(vinyl acetate)
- 1998
-
Ingår i: Journal of Polymer Science Part B. - : John Wiley & Sons. - 0887-6266 .- 1099-0488. ; 36:9, s. 1451-1463
-
Tidskriftsartikel (refereegranskat)abstract
- The thermal conductivity λ and heat capacity per unit volume of poly(vinyl acetate) (260 kg mol-1 in weight average molecular weight) have been measured in the temperature range 150-450 K at pressures up to 1 GPa using the transient hot-wire method, which yielded λ = 0.19 W m-1 K-1 at atmospheric pressure and room temperature. The bulk modulus K has been measured in the temperature range 150-353 K up to 1 GPa. At atmospheric pressure and room temperature, K = 4.0 GPa and (∂K/∂p)T = 8.3. The volume data were used to calculate the volume dependence of λ,g = -((∂λ/λ)/(∂V/V))T.The values for g of the liquid and glassy states were 3.0 and 2.7, respectively, and g of the latter was almost independent of volume and temperature. Theoretical models can predict the value for g of the glassy state to within 25%.
|
|
| 4. |
- Andersson, Mattias, 1985, et al.
(författare)
-
Additive-like amounts of HDPE prevent creep of molten LDPE: Phase-behavior and thermo-mechanical properties of a melt-miscible blend
- 2017
-
Ingår i: Journal of Polymer Science, Part B: Polymer Physics. - : Wiley. - 1099-0488 .- 0887-6266. ; 55:2, s. 146-156
-
Tidskriftsartikel (refereegranskat)abstract
- Low-density polyethylene (LDPE) is the preferred type of polyolefin for many medical and electrical applications because of its superior purity and cleanliness. However, the inferior thermo-mechanical properties as compared to, for example, high-density polyethylene (HDPE), which arise because of the lower melting temperature of LDPE, constitute a significant drawback. Here, we demonstrate that the addition of minute amounts of HDPE to a LDPE resin considerably improves the mechanical integrity above the melting temperature of LDPE. A combination of dynamic mechanical analysis and creep experiments reveals that the addition of as little as 1 to 2 wt% HDPE leads to complete form stability above the melting temperature of LDPE. The investigated LDPE/HDPE blend is found to be miscible in the melt, which facilitates the formation of a solid-state microstructure that features a fine distribution of HDPE-rich lamellae. The absence of creep above the melting temperature of LDPE is rationalized with the presence of tie chains and trapped entanglements that connect the few remaining crystallites.
|
|
| 5. |
- Anselmo, Ana Sofia, 1980-, et al.
(författare)
-
Molecular Orientation and Composition at the Surface of Spin-Coated Polyfluorene:Fullerene Blend Films
- 2013
-
Ingår i: Journal of Polymer Science Part B. - Hoboken, New Jersey : John Wiley & Sons. - 0887-6266 .- 1099-0488. ; 51:3, s. 176-182
-
Tidskriftsartikel (refereegranskat)abstract
- The surface composition in spin-coated films of polyfluorene:fullerene blends was determined quantitatively by near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. By comparing partial and total electron yield spectra, we found vertical compositional differences in the surface region. Furthermore, the orientation of the polymer chains was investigated by variable-angle NEXAFS. Blend films of poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole] with [6,6]-phenyl-C61-butyric acid methyl ester in two different blend ratios were studied. Results showed polymer enrichment of the surfaces for films with a polymer:fullerene weight ratio of 20:80 and of 50:50, spin-coated from both chlorobenzene and chloroform solutions. The angular dependence of the NEXAFS spectra of the pure polymer films showed a preferential plane-on orientation, which was slightly stronger in the subsurface region than at the surface. In blend films, this orientational preference was less pronounced and the difference between surface and subsurface vanished
|
|
| 6. |
- Aziz, Shazed, et al.
(författare)
-
Controlled and scalable torsional actuation of twisted nylon 6 fiber
- 2016
-
Ingår i: Journal of Polymer Science Part B. - : John Wiley & Sons. - 0887-6266 .- 1099-0488. ; 54:13, s. 1278-1286
-
Tidskriftsartikel (refereegranskat)abstract
- Large‐scale torsional actuation occurs in twisted fibers and yarns as a result of volume change induced electrochemically, thermally, photonically, and other means. A quantitative relationship between torsional actuation (stroke and torque) and volume change is here introduced. The analysis is based on experimental investigation of the effects of fiber diameter and inserted twist on the torsional stroke and torque measured when heating and cooling nylon 6 fibers over the temperature range of 26–62 °C. The results show that the torsional stroke depends only on the amount of twist inserted into the fiber and is independent of fiber diameter. The torque generated is larger in fibers with more inserted twist and with larger diameters. These results are successfully modeled using a single‐helix approximation of the twisted fiber structure
|
|
| 7. |
- Backman, Anna, et al.
(författare)
-
Transport properties of uniaxially oriented aliphatic polyketone
- 2004
-
Ingår i: Journal of Polymer Science Part B. - : Wiley. - 0887-6266 .- 1099-0488. ; 42:6, s. 947-955
-
Tidskriftsartikel (refereegranskat)abstract
- The oxygen, carbon dioxide, and water-transport properties of a uniaxially oriented aliphatic polyketone were determined. The polyketone was drawn to 5-10 times its original length. The transport properties were related to changes in crystallinity estimated by differential scanning calorimetry and density measurements and by changes in the molecular and crystal orientation assessed by, respectively, infrared and X-ray spectroscopy. The film structures were characterized by confocal scanning laser microscopy and scanning electron microscopy. Stress-strain tests on the drawn specimens enabled the impacts of orientation on the transport and mechanical properties to be compared. A draw-induced increase in crystallinity and molecular orientation yielded permeabilities at a draw ratio of 10 that were 30-40% of the original value, and the percentage decrease was basically independent of the type of gas/vapor molecule. Also, the diffusivities of oxygen and carbon dioxide decreased by an order of magnitude. The fact that the amorphous permeability was peaking at a draw ratio of about 5 was a consequence of a peak in amorphous solubility, which was very high for oxygen and absent for water. It was suggested that the peak in solubility was mainly caused by the destruction of the polymer hydrogen-bond network during drawing and crystal reorientation. The impact of structural reorganization within the polymer and presence of surface valleys seemed to have less impact on the mechanical properties than on the transport properties. This suggested that transport data are more sensitive than mechanical data in probing material defects and changes in molecular packing and morphology.
|
|
| 8. |
- Berts, Ida, et al.
(författare)
-
Structure of polymer and particle aggregates in hydrogel composites
- 2013
-
Ingår i: Journal of Polymer Science Part B. - : Wiley. - 0887-6266 .- 1099-0488. ; 51:6, s. 421-429
-
Tidskriftsartikel (refereegranskat)abstract
- Knowledge of the structure of a biomaterial is usually vital to control its function. This article provides a structural characterization of a hyaluronan scaffold that has demonstrated good biocompatibility and is used to induce bone regeneration. Hyaluronan hydrogels are appealing materials that can function as a matrix to incorporate both organic and inorganic substances to enhance tissue growth. Because of the intrinsic properties of this swollen matrix, one needs a very sensitive technique that can be applied in situ to determine the organization of the polymers in a gel. Small-angle neutron scattering is used to determine the characteristics of the inhomogeneous structure of the hydrogel both with and without added particles. The results are interpreted using models of structure with two length scales that are beyond the traditional picture of homogeneous gels. The observed structure and the dimensions can explain the previously reported rheological properties of gels containing different amount of polymers. Hydroxyapatite nanoparticles added to the gel are frozen in the gel matrix. We are able to determine the distribution and shape of these particles as they aggregate around the polymer chains. We have also concluded, in this case, that the particle structure is concentration independent. Information about the nanostructure for an applicable biomaterial guides the formulation, preparation, and use that should lead to further understanding of its exploitation.
|
|
| 9. |
- Colombini, Didier, et al.
(författare)
-
Effects of thermal annealing on the viscoelastic properties and morphology of bimodal hard/soft latex blends
- 2005
-
Ingår i: Journal of Polymer Science. Part B, Polymer Physics. - : Wiley. - 0887-6266 .- 1099-0488. ; 43:17, s. 2289-2306
-
Tidskriftsartikel (refereegranskat)abstract
- The effects of thermal annealing on the viscoelastic properties and morphology of films prepared from bimodal latex blends containing equal weight fractions of soft and hard latex particles with controlled sizes were investigated. The thermal and viscoelastic properties of as-dried and annealed samples were investigated with differential scanning calorimetry and dynamic mechanical analysis (DMA). Throughout the thermal annealing, the latex blend morphologies were also followed with atomic force microscopy and transmission electron microscopy (TEM). A particulate morphology, consisting of hard particles evenly dispersed in a continuous soft phase, was observed in the TEM micrographs of the as-dried latex blends and resulted in an enhancement of the mechanical film properties at temperatures between the a relaxations of the soft and hard phases in the DMA thermograms. As soon as the thermal annealing involved temperatures higher than the glass-transition temperature of the hard phase, the hard particles progressively lost their initial spherical shape and formed a more or less continuous phase in the latex blends. This induced coalescence of the hard particles was confirmed by the association of the experimental viscoelastic data with theoretical predictions, based on self-consistent mechanical models, which were performed by the consideration of either a particulate or cocontinuous morphology for the bimodal latex blends. (c) 2005 Wiley Periodicals, Inc.
|
|
| 10. |
- Crispin, Xavier, et al.
(författare)
-
Conductivity, Morphology, Interfacial Chemistry, and Stability of Poly(3,4- ethylene dioxythiophene)–Poly(styrene sulfonate) : A Photoelectron Spectroscopy Study
- 2003
-
Ingår i: Journal of Polymer Science Part B. - : John Wiley & Sons. - 0887-6266 .- 1099-0488. ; 41:21, s. 2561-2583
-
Forskningsöversikt (refereegranskat)abstract
- X-ray photoelectron spectroscopy (XPS) has been used to characterize poly(3,4-ethylene dioxythiophene)-poly(styrene sulfonate) (PEDT/PSS), one of the most common electrically conducting organic polymers. A correlation has been established between the composition, morphology, and polymerization mechanism, on the one hand, and the electric conductivity of PEDT/PSS, on the other hand. XPS has been used to identify interfacial reactions occurring at the polymer-on-ITO and polymer-on-glass interfaces, as well as chemical changes within the polymer blend induced by electrical stress and exposure to ultraviolet light.
|
|
