scholarly journals Anomalous Terminal Shear Viscosity Behavior of Polycarbonate Nanocomposites Containing Grafted Nanosilica Particles

Nanomaterials ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1839
Author(s):  
Vaidyanath Ramakrishnan ◽  
Johannes G. P. Goossens ◽  
Theodorus L. Hoeks ◽  
Gerrit W. M. Peters
Keyword(s):  
Polymer Melt ◽  
Polymer Processing ◽  
Radius Of Gyration ◽  
Entanglement Density ◽  
Nanoparticle Surface ◽  
Viscosity Behavior ◽  
Shear Processing ◽  
Nanosilica Particles ◽  
Low Shear

Viscosity controls an important issue in polymer processing. This paper reports on the terminal viscosity behavior of a polymer melt containing grafted nanosilica particles. The melt viscosity behavior of the nanocomposites was found to depend on the interaction between the polymer matrix and the nanoparticle surface. In the case of polycarbonate (PC) nanocomposites, the viscosity decreases by approximately 25% at concentrations below 0.7 vol% of nanosilica, followed by an increase at higher concentrations. Chemical analysis shows that the decrease in viscosity can be attributed to in situ grafting of PC on the nanosilica surface, leading to a lower entanglement density around the nanoparticle. The thickness of the graft layer was found to be of the order of the tube diameter, with the disentangled zone being approximately equal to the radius of gyration (Rg) polymer chain. Furthermore, it is shown that the grafting has an effect on the motion of the PC chains at all timescales. Finally, the viscosity behavior in the PC nanocomposites was found to be independent of the molar mass of PC. The PC data are compared with polystyrene nanocomposites, for which the interaction between the polymer and nanoparticles is absent. The results outlined in this paper can be utilized for applications with low shear processing conditions, e.g., rotomolding, 3D printing, and multilayer co-extrusion.

Inverse Rheological Methods for the Determination of Polymer Structures, Diffusion of Small Molecules and Nanofiber Lengths

2020 ◽  
Vol 35 (5) ◽  
pp. 448-457
Author(s):  
P. Cassagnau
Keyword(s):  
Ring Opening ◽  
Average Length ◽  
Polymer Melt ◽  
Reactive Extrusion ◽  
Organic Peroxide ◽  
Polymer Processing ◽  
Multi Scale ◽  
Dilute Suspensions

Abstract This paper presents so-called inverse rheology methods to determine various parameters that are essential to go further in terms of modelling and/or simulation in the field of polymer processing. The following systems from our previous works are presented: i) Determination of the molecular structure of a poly(e-caprolactone) polymerized in-situ by ring-opening; ii) Measurement of the mutual diffusion coefficient: two cases are considered, namely the diffusion of a plasticizer and the diffusion of an organic peroxide in a polymer melt and iii) Determination of the average length of polymer nanofibers in suspension and study of the universal behavior of nanofibers of different natures in dilute and semi-dilute suspensions. The application of these different studies in the field of reactive extrusion, blending and multi-scale structuring are presented and discussed.

scholarly journals Epitaxial Crystallization of Poly(ε-caprolactone) on Reduced Graphene Oxide at a Low Shear Rate by In Situ SAXS/WAXD Methods

ACS Omega ◽  
2020 ◽  
Vol 5 (49) ◽  
pp. 31535-31542
Author(s):  
Weijun Miao ◽  
Feng Wu ◽  
Shiman Zhou ◽  
Guibin Yao ◽  
Yiguo Li ◽  
...  
Keyword(s):  
Graphene Oxide ◽  
Shear Rate ◽  
Reduced Graphene Oxide ◽  
Epitaxial Crystallization ◽  
Reduced Graphene ◽  
Low Shear

The effect of soil-structure interaction on seismometer readings

1978 ◽  
Vol 68 (3) ◽  
pp. 823-843
Author(s):  
G. N. Bycroft
Keyword(s):  
Ground Motion ◽  
Soil Structure ◽  
Free Field ◽  
Soil Structure Interaction ◽  
Rigid Sphere ◽  
Elastic Space ◽  
Structure Interaction ◽  
Frequency Components ◽  
Low Shear

abstract Rocking and vertical and horizontal translations of typical “free-field” seismometer installations lead to magnification of the ground motion record. This magnification can be significant for the higher frequency components if the terrain has a relatively low shear-wave velocity. Seismometers placed on foundations which cover a significant part of a wavelength of a horizontally incident wave, experience an attenuated ground motion. A method of correcting the seismograms for these effects is given. Compliance functions for a rigid sphere in a full elastic space are derived and are used to show that, in practical cases, down-hole seismometer installations are not significantly affected by interaction. These compliance functions should be useful in discussing the soil structure interaction of structures erected on bulbous piles. They may be also used as the basis of a method of determining elastic constants of ground at depth, in situ, and at different frequencies.

scholarly journals Enhanced Foamability with Shrinking Microfibers in Linear Polymer

Polymers ◽  
2019 ◽  
Vol 11 (2) ◽  
pp. 211 ◽  
Author(s):  
Eric Kim ◽  
Heon Park ◽  
Carlos Lopez-Barron ◽  
Patrick Lee
Keyword(s):  
Strain Hardening ◽  
Polymer Processing ◽  
Expansion Ratio ◽  
Low Frequencies ◽  
Extensional Rheometry ◽  
Enhanced Strain ◽  
Linear Viscoelastic ◽  
Cost Efficient ◽  
Strain Hardening Behavior

Strain hardening has important roles in understanding material structures and polymer processing methods, such as foaming, film forming, and fiber extruding. A common method to improve strain hardening behavior is to chemically branch polymer structures, which is costly, thus preventing users from controlling the degree of behavior. A smart microfiber blending technology, however, would allow cost-efficient tuning of the degree of strain hardening. In this study, we investigated the effects of compounding polymers with microfibers for both shear and extensional rheological behaviors and characteristics and thus for the final foam morphologies formed by batch physical foaming with carbon dioxide. Extensional rheometry showed that compounding of in situ shrinking microfibers significantly enhanced strain hardening compared to compounding of nonshrinking microfibers. Shear rheometry with linear viscoelastic data showed a greater increase in both the loss and storage modulus in composites with shrinking microfibers than in those with nonshrinking microfibers at low frequencies. The batch physical foaming results demonstrated a greater increase in the cell population density and expansion ratio with in situ shrinking microfibers than with nonshrinking microfibers. The enhancement due to the shrinkage of compounded microfibers decreasing with temperature implies that the strain hardening can be tailored by changing processing conditions.

Product Strength and Orientation Manipulation via Vibration-Assisted Injection Molding

2002 ◽  
Author(s):  
David C. Angstadt ◽  
John P. Coulter
Keyword(s):  
Thermal Conductivity ◽  
Tensile Strength ◽  
Injection Molding ◽  
Molecular Orientation ◽  
Polymer Melt ◽  
Polymer Processing ◽  
Shear Yielding ◽  
Processing Methods ◽  
Improve Product

This investigation focuses on determining why polystyrene ASTM specimens exhibit an increase in tensile strength when processed by vibration assisted injection molding (VAIM) while polycarbonate parts do not. VAIM is one of several polymer processing methods that attempt to improve product properties via manipulation of the polymer melt. Observation of birefringence patterns in VAIM processed polystyrene samples show a significant impact on molecular orientation. The same studies were conducted on opaque polycarbonate and were unable to determine the degree of molecular orientation via birefringence measurement. It was theorized that VAIM did not produce significant orientation due to its higher thermal conductivity and stiffer backbone. It has been determined by this investigation that VAIM processing does impart significant molecular orientation in polycarbonate specimens but still does not increase its UTS. It is proposed that increased molecular orientation induced by VAIM processing inhibits crazes from growing into cracks. VAIM therefore favors polymers that fail by crazing (e.g., polystyrene) rather than those that fail by shear yielding (e.g., polycarbonate).

Observing the colloidal stability of iron oxide nanoparticlesin situ

Nanoscale ◽  
2019 ◽  
Vol 11 (27) ◽  
pp. 13098-13107 ◽  
Author(s):  
Ryan Hufschmid ◽  
Eric Teeman ◽  
B. Layla Mehdi ◽  
Kannan M. Krishnan ◽  
Nigel D. Browning
Keyword(s):  
Iron Oxide ◽  
Scanning Transmission Electron Microscopy ◽  
Colloidal Stability ◽  
Iron Oxide Nanoparticle ◽  
Nanoparticle Surface ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Liquid Cell ◽  
Oxide Nanoparticle

Iron oxide nanoparticle surface chemistry controls growth and dissolution, which are observed in real-time usingin situliquid cell Scanning Transmission Electron Microscopy (STEM).

scholarly journals In-Situ X-Ray Characterization of Fiber Structure during Melt Spinning

2008 ◽  
Vol 3 (3) ◽  
pp. 155892500800300 ◽  
Author(s):  
Michael S. Ellison ◽  
Paulo E. Lopes ◽  
William T. Pennington
Keyword(s):  
Melt Spinning ◽  
Simultaneous Detection ◽  
Polymer Melt ◽  
Polymer Chains ◽  
Degree Of Crystallinity ◽  
Structure Evolution ◽  
X Ray ◽  
Spinning Process

The properties of a polymer are strongly influenced by its morphology. In the case of fibers from semi-crystalline polymers this consists of the degree of crystallinity, the spacing and alignment of the crystalline regions, and molecular orientation of the polymer chains in the amorphous regions. Information on crystallinity and orientation can be obtained from X-ray analysis. In-situ X-ray characterization of a polymer during the melt spinning process is a major source of information about the effects of material characteristics and processing conditions upon structure evolution along the spinline, and the final structure and properties of the end product. We have recently designed and installed an X-ray system capable of in-situ analysis during polymer melt spinning. To the best of our knowledge this system is unique in its capabilities for the simultaneous detection of wide angle and small angle X-ray scattering (WAXS and SAXS, respectively), its use of a conventional laboratory radiation source, its vertical mobility along the spinline, and its ability to simulate a semi-industrial environment. Setup, operation and demonstration of the capabilities of this system is presented herein as applied to the characterization of the melt spinning of isotactic poly(propylene). Crystallinity and crystalline orientation calculated from WAXS patterns, and lamellar long period calculated from SAXS patterns, were obtained during melt spinning of the polymer along the spinline.

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