A General Model for the Ideal Chain Length Distributions of Polymers Made with Reversible Deactivation

2022 ◽  
Author(s):  
Madison Kearns ◽  
Colleen Morleey ◽  
Kostas Parkatzidis ◽  
Richard Whitfield ◽  
Alvaro Sponza ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Chain Length ◽  
Polymer Material ◽  
General Model ◽  
Polymer System ◽  
Polymer Molecular Weight ◽  
Ideal Chain ◽  
Reversible Deactivation ◽  
And Performance ◽  
The Ideal

Polymer molecular weight, or chain length distributions, are a core characteristic of a polymer system, with the distribution being intimately tied to the properties and performance of the polymer material....

The Effect of Polymers on Ceramic Suspension Rheology and Green Component Properties

1992 ◽  
Vol 289 ◽  
Author(s):  
Jennifer A. Lewis ◽  
Andrea L. Ogden ◽  
David Schroeder ◽  
Kirk J. Duchow
Keyword(s):  
Molecular Weight ◽  
Polymer System ◽  
Polyvinyl Butyral ◽  
Shear Thinning ◽  
Suspension Rheology ◽  
Low Molecular Weight ◽  
Polymer Molecular Weight ◽  
Green Component ◽  
Ceramic Suspensions ◽  
Packing Efficiency

AbstractCeramic suspensions were formulated based on an alumina/plasticized-polymer system. The total polymer volume in suspension was held constant, while the relative amount of high-to-low molecular weight polyvinyl butyral (PVB) in suspension was varied. Experiments were performed to elucidate the effects of polymer molecular weight and distribution on the rheological properties of these casting suspensions as well as on the green microstructure of tape-cast components. The polymer properties affected not only the suspension viscosity at a given shear rate as expected, but also the shear thinning behavior of each suspension. Tapes (thickness ≈ 250 μm) were cast from these suspensions and their properties were evaluated. Pore volume, a measure of the packing efficiency, was found to depend strongly on the polymer molecular weight and distribution. In addition, preliminary lamination studies revealed that dimensional stability and anisotropy were also affected by the relative amount of high-to-low molecular weight PVB. A direct correlation was shown to exist between the shear thinning behavior of these suspensions and the resulting dimensional anisotropy exhibited by the tapes cast from each of them. These results demonstrate that polymeric aids influence not only the suspension rheology, but the green component microstructure as well, and, hence, are an integral aspect of ceramic processing.

Elucidating the impact of molecular weight on morphology, charge transport, photophysics and performance of all-polymer solar cells

2020 ◽  
Vol 8 (40) ◽  
pp. 21070-21083 ◽  
Author(s):  
Duyen K. Tran ◽  
Amélie Robitaille ◽  
I. Jo Hai ◽  
Xiaomei Ding ◽  
Daiki Kuzuhara ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Solar Cells ◽  
Charge Transport ◽  
Polymer Solar Cells ◽  
Polymer Molecular Weight ◽  
Photovoltaic Properties ◽  
Blend Morphology ◽  
And Performance ◽  
The Impact

This work provides a unified understanding on how polymer molecular weight influences the blend photophysics, blend morphology, charge transport, and photovoltaic properties of all-polymer solar cells.

Crystallization of Isotactic Poly(propylene) in Solution as Followed by Slow Calorimetry

1995 ◽  
Vol 60 (11) ◽  
pp. 1905-1924 ◽  
Author(s):  
Hong Phuong-Nguyen ◽  
Geneviève Delmas
Keyword(s):  
Molecular Weight ◽  
Crystal Growth ◽  
High Temperature ◽  
Heat Of Fusion ◽  
Complete Dissolution ◽  
Polymer Molecular Weight ◽  
Solvent Quality ◽  
Temperature Ramp ◽  
Poly Propylene

Dissolution, crystallization and second dissolution traces of isotactic poly(propylene) have been obtained in a slow temperature ramp (3 K h-1) with the C80 Setaram calorimeter. Traces of phase-change, in presence of solvent, are comparable to traces without solvent. The change of enthalpy on heating or cooling, ∆Htotal, over the 40-170 °C temperature range, is the sum of two contributions, ∆HDSC and ∆Hnetwork. The change ∆HDSC is the usual heat obtained in a fast temperature ramp and ∆Hnetwork is associated with a physical network whose disordering is slow and subject to superheating due to strain. When dissolution is complete, ∆Htotal is equal to ∆H0, the heat of fusion of perfect crystals. The values of ∆Htota for nascent and recrystallized samples are compared. Dissolution is the tool to evaluate the quality of the crystals. The repartition of ∆Htotal, into the two endotherms, reflects the quality of crystals. The crystals grown more rapidly have a higher fraction of network crystals which are stable at high T in the solvents. A complete dissolution, i.e. a high temperature (170 °C or more) is necessary to obtain good crystals. The effect of concentration, polymer molecular weight and solvent quality on crystal growth is analyzed.

scholarly journals Impact of Macrodiols on the Morphological Behavior of H12MDI/HDO-Based Polyurethane Elastomer

Polymers ◽  
2021 ◽  
Vol 13 (13) ◽  
pp. 2060
Author(s):  
Shazia Naheed ◽  
Mohammad Zuber ◽  
Mahwish Salman ◽  
Nasir Rasool ◽  
Zumaira Siddique ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Contact Angle ◽  
Chain Length ◽  
Microphase Separation ◽  
Soft Segment ◽  
Group Identification ◽  
Degree Of Crystallinity ◽  
Polyurethane Elastomers ◽  
Hard Segments ◽  
Morphological Behavior

In this study, we evaluated the morphological behavior of polyurethane elastomers (PUEs) by modifying the soft segment chain length. This was achieved by increasing the soft segment molecular weight (Mn = 400–4000 gmol−1). In this regard, polycaprolactone diol (PCL) was selected as the soft segment, and 4,4′-cyclohexamethylene diisocyanate (H12MDI) and 1,6-hexanediol (HDO) were chosen as the hard segments. The films were prepared by curing polymer on Teflon surfaces. Fourier transform infrared spectroscopy (FTIR) was utilized for functional group identification in the prepared elastomers. FTIR peaks indicated the disappearance of −NCO and −OH groups and the formation of urethane (NHCOO) groups. The morphological behavior of the synthesized polymer samples was also elucidated using scanning electron microscopy (SEM) and atomic force microscopy (AFM) techniques. The AFM and SEM results indicated that the extent of microphase separation was enhanced by an increase in the molecular weight of PCL. The phase separation and degree of crystallinity of the soft and hard segments were described using X-ray diffraction (XRD). It was observed that the degree of crystallinity of the synthesized polymers increased with an increase in the soft segment’s chain length. To evaluate hydrophilicity/hydrophobicity, the contact angle was measured. A gradual increase in the contact angle with distilled water and diiodomethane (38.6°–54.9°) test liquids was observed. Moreover, the decrease in surface energy (46.95–24.45 mN/m) was also found to be inconsistent by increasing the molecular weight of polyols.

scholarly journals Evaluation of the Legal Framework for Building Fire Safety Regulations in Spain

Buildings ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 51
Author(s):  
Amaya Osácar ◽  
Juan Bautista Echeverria Trueba ◽  
Brian Meacham
Keyword(s):  
Fire Safety ◽  
Risk Mitigation ◽  
Fire Risk ◽  
Legal Framework ◽  
Regulatory Framework ◽  
Existing Building ◽  
Building Fire ◽  
Safety Regulations ◽  
And Performance ◽  
The Ideal

There is a trend in Europe towards increasing the quality and performance of regulations. At the same time, regulatory failure has been observed in the area of building fire safety regulation in England and elsewhere. As a result, an analysis of the appropriateness of fire safety regulations in Spain is warranted, with the objective being to assess whether a suitable level of fire safety is currently being delivered. Three basic elements must be considered in such analysis: the legal and regulatory framework, the level of fire risk/safety of buildings that is expected and the level which actually results, and a suitable method of analysis. The focus of this paper is creating a legal and regulatory framework, in particular with respect to fire safety in buildings. Components of an ”ideal” building regulatory framework to adequately control fire risk are presented, the existing building regulatory framework is summarized, and an analysis of the gaps between the ideal and the existing systems is presented. It is concluded that the gaps between the ideal and the existing framework are significant, and that the current fire safety regulations are not appropriate for assuring delivery of the intended level of fire risk mitigation.

Sign in / Sign up

Export Citation Format

Share Document