Molecular weights of polyethylene and polypropylene by vapor pressure osmometry at elevated temperatures

1987 ◽  
Vol 34 (7) ◽  
pp. 2619-2622 ◽  
Author(s):  
J. W. Mays ◽  
E. G. Gregory
Keyword(s):  
Vapor Pressure ◽  
Elevated Temperatures ◽  
Vapor Pressure Osmometry ◽  
Molecular Weights

scholarly journals Preparation and Properties of Electrospun Phenylethynyl—Terminated Polyimide Nano-Fibrous Membranes with Potential Applications as Solvent-Free and High-Temperature Resistant Adhesives for Harsh Environments

Nanomaterials ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 1525
Author(s):  
Hao-ran Qi ◽  
Deng-xiong Shen ◽  
Yan-jiang Jia ◽  
Yuan-cheng An ◽  
Hao Wu ◽  
...  
Keyword(s):  
Stainless Steel ◽  
High Temperature ◽  
Elevated Temperatures ◽  
Solvent Free ◽  
High Tech ◽  
Molecular Weights ◽  
Lap Shear ◽  
High Adhesion ◽  
Potential Applications ◽  
Fibrous Membranes

High-temperature-resistant polymeric adhesives with high servicing temperatures and high adhesion strengths are highly desired in aerospace, aviation, microelectronic and other high-tech areas. The currently used high-temperature resistant polymeric adhesives, such as polyamic acid (PAA), are usually made from the high contents of solvents in the composition, which might cause adhesion failure due to the undesirable voids caused by the evaporation of the solvents. In the current work, electrospun preimidized polyimide (PI) nano-fibrous membranes (NFMs) were proposed to be used as solvent-free or solvent-less adhesives for stainless steel adhesion. In order to enhance the adhesion reliability of the PI NFMs, thermally crosslinkable phenylethynyl end-cappers were incorporated into the PIs derived from 3,3’,4,4’-oxydiphthalic anhydride (ODPA) and 3,3-bis[4-(4-aminophenoxy)phenyl]phthalide (BAPPT). The derived phenylethynyl-terminated PETI-10K and PETI-20K with the controlled molecular weights of 10,000 g mol−1 and 20,000 g mol−1, respectively, showed good solubility in polar aprotic solvents, such as N-methyl-2-pyrrolidinone (NMP) and N,N-dimethylacetamide (DMAc). The PI NFMs were successfully fabricated by electrospinning with the PETI/DMAc solutions. The ultrafine PETI NFMs showed the average fiber diameters (dav) of 627 nm for PETI-10K 695 nm for PETI-20K, respectively. The PETI NFMs showed good thermal resistance, which is reflected in the glass transition temperatures (Tgs) above 270 °C. The PETI NFMs exhibited excellent thermoplasticity at elevated temperatures. The stainless steel adherends were successfully adhered using the PETI NFMs as the adhesives. The PI NFMs provided good adhesion to the stainless steels with the single lap shear strengths (LSS) higher than 20.0 MPa either at room temperature (25 °C) or at an elevated temperature (200 °C).

Fast Membrane Osmometer as Alternative to Freezing Point and Vapor Pressure Osmometry

2008 ◽  
Vol 80 (7) ◽  
pp. 2617-2622 ◽  
Author(s):  
Alessandro Grattoni ◽  
Giancarlo Canavese ◽  
Franco Maria Montevecchi ◽  
Mauro Ferrari
Keyword(s):  
Vapor Pressure ◽  
Freezing Point ◽  
Vapor Pressure Osmometry

KINETIC ASPECTS OF THE COPOLYMERIZATION OF TETRAHYDROFURAN WITH PROPYLENE OXIDE. I

1966 ◽  
Vol 44 (22) ◽  
pp. 2679-2689 ◽  
Author(s):  
L. P. Blanchard ◽  
J. Singh ◽  
M. D. Baijal
Keyword(s):  
Vapor Pressure ◽  
Propylene Oxide ◽  
Chemical Reduction ◽  
Group Analysis ◽  
Vapor Pressure Osmometry ◽  
Hydroxyl Groups ◽  
Internal Reference ◽  
Boron Fluoride ◽  
Co Catalysts ◽  
End Group

Tetrahydrofuran and propylene oxide were copolymerized in the presence of the catalyst boron fluoride ethyl ether, and various co-catalysts, such as 1,2-propanediol, 1,3-propanediol, and 1,4-butanediol. Ethylene chloride was used as a solvent and as an internal reference for analytical purposes. Reactions were carried out at 0 °C and at atmospheric pressure. Monomer concentrations were determined by vapor phase chromatography, and copolymer molecular structure analyses were carried out by physical and chemical methods including infrared spectroscopy, vapor pressure osmometry, hydroxyl end-group analysis, and chemical reduction of unsaturated linkages.The homopolymerization of tetrahydrofuran did not take place, whereas that of propylene oxide proceeded at a rapid rate. In the copolymerization of tetrahydrofuran with propylene oxide, the rate of disappearance of tetrahydrofuran was found to be independent of its concentration, but varied directly with the concentration of propylene oxide. Under similar conditions, the rate of disappearance of propylene oxide was found to be (a) proportional to the square of its concentration, and (b) inversely proportional to the concentration of tetrahydrofuran.Reactivity ratios varied between 1.3 and 1.8 for propylene oxide and between 0.1 and 0.6 for tetrahydrofuran. Molecular weights obtained by vapor pressure osmometry ranged between 460 and 740, and those obtained by hydroxyl end-group analysis ranged between 520 and 1 660. Infrared spectra confirmed the presence of hydroxyl groups and ether linkages in the copolymers prepared. Results on terminal unsaturation were negative.

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