Effect of Chain Length of Polyethylene Glycol and Crosslink Density (NCO/OH) on Properties of Castor Oil Based Polyurethane Elastomers

2006 ◽  
Vol 43 (4-5) ◽  
pp. 797-811 ◽  
Author(s):  
Keyur P. Somani ◽  
Natvar K. Patel ◽  
Sujata S. Kansara ◽  
Animesh K. Rakshit
Keyword(s):  
Polyethylene Glycol ◽  
Chain Length ◽  
Castor Oil ◽  
Crosslink Density ◽  
Polyurethane Elastomers

Effect and Detection of Loose Chain Ends in Crosslinked Polyurethane Elastomers

1971 ◽  
Vol 44 (1) ◽  
pp. 152-165 ◽  
Author(s):  
A. E. Oberth
Keyword(s):  
Crosslink Density ◽  
Volume Fraction ◽  
Present Theory ◽  
Swelling Ratio ◽  
Polyurethane Elastomers ◽  
Equilibrium Volume ◽  
Equilibrium Swelling ◽  
Volume Swelling

Abstract The effect of loose chain ends on tensile properties and equilibrium swelling of crosslinked polyurethane rubbers is studied. As in plasticized elastomers, tensile strength and elastic modulus are reduced approximately by a factor (1−νE,P)2, where νE,P is the volume fraction of loose chain ends, plasticizer, or both. This effect is much larger than predicted by present theory. Also the equilibrium volume swelling ratio, V0/V, of rubbers having terminal chains or an equal volume of plasticizer is the same, provided they do not differ in crosslink density. However, the volume fraction of “network rubber” in the equilibrium swollen specimen, ν2, differs owing to the non-extractability of terminal chains. On this basis a method is proposed which allows experimental determination of the volume fraction of loose ends. Elastomers abounding in loose chain ends show markedly less long term stress relaxation. This effect is not clearly understood but is useful to detect the presence of non load-bearing network.

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 The effect of the polyethylene glycol chain length of a lipopolymer (DSPE-PEGn) on the properties of DPPC monolayers and bilayers

2021 ◽  
pp. 116529
Author(s):  
Magdalena Kowalska ◽  
Marcin Broniatowski ◽  
Marzena Mach ◽  
Łukasz Płachta ◽  
Paweł Wydro
Keyword(s):  
Polyethylene Glycol ◽  
Chain Length

Impact of the chain length on the biodistribution profiles of PEGylated iron oxide nanoparticles: a multimodal imaging study

2021 ◽  
Author(s):  
Dimitri Stanicki ◽  
Lionel Larbanoix ◽  
Sébastien Boutry ◽  
Thomas Vangijzegem ◽  
Indiana Ternad ◽  
...  
Keyword(s):  
Polyethylene Glycol ◽  
Iron Oxide ◽  
Chain Length ◽  
Iron Oxide Nanoparticles ◽  
Multimodal Imaging ◽  
Imaging Study ◽  
Superparamagnetic Iron Oxide ◽  
Superparamagnetic Iron Oxide Nanoparticles ◽  
Oxide Nanoparticles ◽  
Chain Lengths

Bimodal sub-5 nm superparamagnetic iron oxide nanoparticles (SPIO-5) coated with polyethylene glycol of different chain lengths (i.e. PEG-800, -2000 and -5000) have been prepared and characterized.

Mechanical Chain-Scission in Rubber Vulcanizate at Low Temperatures

1979 ◽  
Vol 52 (4) ◽  
pp. 773-780 ◽  
Author(s):  
T. Kusano ◽  
K. Kobayashl ◽  
K. Murakami
Keyword(s):  
Free Radicals ◽  
Chain Length ◽  
Low Temperatures ◽  
Crosslink Density ◽  
Glassy State ◽  
Chain Scission ◽  
Molecular Chain ◽  
Yield Strain ◽  
Air Stream ◽  
Intermolecular Reaction

Abstract When vulcanized natural rubbers are forced to extend in the glassy state, free radicals are produced by the scission of the primary chain. The amount of the free radicals increases with the strain. The tensile yield strain decreases with the decrease of the molecular chain length between crosslinks. This behavior is explainable on the basis of the limited chain extensibility. The extended chains are broken with further increases of the strain. The mechanically produced free radicals are quite stable below about −40°C. The crosslink density of the chain-ruptured material increases about 2∼3×10−5 mol/cm3. This fact shows that the free radicals are consumed not only by recombination but by the intermolecular reaction. In both sulfur and DCP vulcanizates, the network chains rather than the crosslinks are broken by stretching. In an air stream, some free radicals react with oxygen and others form crosslinks.

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