Relation of Modulus of Urethan Rubber to Molecular Weight of Polyester

1966 ◽  
Vol 39 (4) ◽  
pp. 1089-1093
Author(s):  
Julian R. Little ◽  
Robert A. Gregg
Keyword(s):  
Molecular Weight ◽  
Toluene Diisocyanate ◽  
Chain Extension ◽  
Cross Linking ◽  
Diphenylmethane Diisocyanate ◽  
Ethylene Propylene ◽  
Poly Ethylene

Abstract The modulus of polyurethan rubber prepared from poly(ethylene propylene) (70–30) adipate and diphenylmethane diisocyanate by chain extension and cross-linking with water is proportional to the reciprocal molecular weight of the polyester diisocyanate. The modulus at a given molecular weight is lowered by chain extension of the polyester with diisocyanate. The modulus is increased 40 per cent by change of the diisocyanate to 1,5-naphthalene diisocyanate and reduced 60 per cent by change to 2,4-toluene diisocyanate.

Preparation and Properties of a Hydrolytically Stable Cyclooctyne-Containing Polymer

Synlett ◽  
2018 ◽  
Vol 29 (19) ◽  
pp. 2535-2541
Author(s):  
Alex Adronov ◽  
Kelvin Li ◽  
Stuart McNelles
Keyword(s):  
Molecular Weight ◽  
Ethylene Glycol ◽  
Monomethyl Ether ◽  
Phenylene Vinylene ◽  
Cross Linking ◽  
Poly Ethylene Glycol ◽  
Ethylene Glycol Monomethyl Ether ◽  
Glycol Monomethyl Ether ◽  
Poly Ethylene

A poly[(phenylene vinylene)-co-dibenzocyclooctyne] polymer prepared by Wittig polymerization chemistry between dibenzocyclooctyne bisaldehyde [DIBO-(CHO)2] and bis(triethyleneglycol)phenylbis(tributylphosphonium) dibromide is reported. The resulting polymer exhibits moderate molecular weight (Mn: 10.5 kDa, Mw: 21.3 kDa, Ð: 2.02) and is fluorescent. It could be readily functionalized by strain-promoted alkyne-azide cycloadditon with different azides, and fluorescence of the polymer was preserved after functionalization. Grafting azide-terminated 5 kDa poly(ethylene glycol) monomethyl ether chains drastically affected the solubility of the polymer. Cross-linking the polymer with poly(ethylene glycol) that was terminated at both ends with azide groups gave access to a fluorescent organogel that could be dried and reswollen with water to form a hydrogel.

Enhancement of Mechanical Properties Upon Hydration in Copolymers of PEG and Iodinated Tyrosine-derived Poycarbonates

2008 ◽  
Vol 1132 ◽  
Author(s):  
F. Bedoui ◽  
L. K. Widjaja ◽  
A. Luk ◽  
D. Bolikal ◽  
N. S. Murthy ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Molecular Weight ◽  
Ethylene Glycol ◽  
Ethyl Ester ◽  
Opposite Effect ◽  
Polymeric Materials ◽  
Cross Linking ◽  
Poly Ethylene Glycol ◽  
Reinforcing Effect ◽  
Poly Ethylene

ABSTRACTIncrease in modulus upon hydration in copolymers of desaminotyrosyl-tyrosine ethyl ester (DTE) and poly(ethylene glycol) (PEG) with iodinated tyrosines, poly(I2DTE-co-PEG carbonate)s, was investigated by varying the fraction and the molecular weight of the hydrophilic PEG component. Water, as expected, acts as plasticizer in polymer with PEG content < 15 wt% and > 30 wt%. But, water has the opposite effect in iodinated polymers with moderate PEG contents, between 15 to 20 wt%: it enhances the Young's modulus. The strength and modulus of hydrated poly(I2DTE-co-15%PEG2K carbonate)s increased by as much as fifteen fold upon hydration. While the decrease in the mechanical properties in most polymeric materials with diluents such water is due to the solvent-induced swelling, the increase in strength and modulus that is observed is most likely due to the reinforcing effect of the increased cross-linking efficiency of the hydrated PEG domains in the iodinated polymer.

scholarly journals Synergistic effects in cross-linked blends of ion-conducting PEO-/PPO-based unsaturated polyesters

Ionics ◽  
2021 ◽  
Author(s):  
Pia B. Sassmann ◽  
Oliver Weichold
Keyword(s):  
Molecular Weight ◽  
Synergistic Effects ◽  
Molar Ratio ◽  
Proton Relaxation ◽  
Cross Linking ◽  
Unsaturated Polyesters ◽  
Redox Initiator ◽  
Ion Conducting ◽  
Poly Ethylene ◽  
Opposing Effects

AbstractIon-conductive unsaturated polyesters (UP) were synthesised from poly(ethylene oxide) (Xn = 9, 13, 22, 90) or poly(propylene oxide) (Xn = 7, 13, 20, 34, 68) and maleic anhydride. Subsequently, the polyesters were doped with LiClO4 and cross-linked with styrene using a redox initiator. For PEO-based polyesters, the minimum resistivity is found at an O/Li+ molar ratio of 50/1. In contrast, more lithium is required to reach the minimum when using PPO (O/Li+ = 10/1). Unlike the PEO-based polyesters, cross-linking of the PPO types gives rise to decreasing resistivities at increasing molecular weight. This correlates well with the transverse proton relaxation time determined by single-sided NMR, which is an indicator of the chain mobility. The cross-linking reaction of these UP with styrene exactly follows the predictions based on the copolymerisation parameters and is, therefore, not dependent on the ratio of styrene to UP double bonds as previously reported. Due to the opposing effects of the molecular weight on the ion conductivity of PEO- and PPO-based UP, 1:1 blends of short-chain PPO and long-chain PEO polyesters were cross-linked with styrene. The resulting networks showed a resistivity of 4 kΩ m (σ = 2.5∙10−4 S∙m−1), which is 5 times lower than the pure PEO and 3 times lower than the pure PPO materials.

Polyurethane one-component foam formulation optimization for low free isocianate monomer content

2016 ◽  
Vol 53 (2) ◽  
pp. 167-179 ◽  
Author(s):  
Ana C Marques ◽  
Helena Dias ◽  
Sandro Matos ◽  
Bruno Sargaço ◽  
Ricardo Simoes ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Flame Retardant ◽  
High Molecular Weight ◽  
Polyurethane Foams ◽  
Toluene Diisocyanate ◽  
Chain Extension ◽  
Methylene Diphenyl Diisocyanate ◽  
Monomer Content ◽  
Aerosol Cans ◽  
One Year

Recent changes in legislation have forced one-component foam producers to drop the amount of free monomeric isocyanate in their polyurethane systems. Also, it is required that commercial polyurethane aerosol cans exhibit at least one year of shelf life and polyurethane foams must be classified as B2 on the fire testing following DIN 4102. This paper reports on a systematic optimization study of polyurethane formulations dedicated to address these current industry requirements. A one-component foam system exhibiting simultaneously all of these parameters was achieved by reacting conventional diols, a relatively low-molecular weight monol (2-ethylhexanol), a flame retardant high-molecular weight monol (tris(bromoneopentyl)alcohol), a methylene diphenyl diisocyanate-based prepolymer (GreenAdduct 13), and a small amount of 2,4′-toluene diisocyanate. The use of monols allows producing prepolymers with low free methylene diphenyl diisocyanate by preventing chain extension and, therefore, avoiding extreme viscosity build-up. Toluene diisocyanate also promotes a lower viscosity inside the aerosol can, which enables the use of high enough quantities of high-molecular weight flame retardant monol to achieve a B2 fire test classification.

Non-toxic polyester urethanes based on poly(lactic acid), poly(ethylene glycol) and lysine diisocyanate

2016 ◽  
Vol 32 (3) ◽  
pp. 225-241 ◽  
Author(s):  
Alena Pavelková ◽  
Pavel Kucharczyk ◽  
Zdenka Kuceková ◽  
Jiří Zedník ◽  
Vladimír Sedlařík
Keyword(s):  
Molecular Weight ◽  
Lactic Acid ◽  
Ethylene Glycol ◽  
Biomedical Applications ◽  
Hydrolytic Degradation ◽  
Chain Extension ◽  
Poly Lactic Acid ◽  
Side Reactions ◽  
Poly Ethylene Glycol ◽  
Poly Ethylene

Poly(lactic acid)-based polymers are highly suitable for temporary biomedical applications, such as tissue support or drug delivery systems. Copolymers of different molecular weight based on poly(lactic acid) and poly(ethylene glycol) were prepared by polycondensation, catalysed by hydrochloric acid. A chain-extension reaction with l-lysine ethyl ester diisocyanate was employed afterwards to obtain polyester urethanes with enhanced properties. The GPC results showed that the molecular weights of the products reached about 50,000 g·mol−1 and the hydrolytic progress was rapid in the first 2 weeks; the drop in Mn equalled approximately 70%. Additionally, elemental analysis of the buffer medium proved that hydrolytic degradation was more rapid in the first stage. Tensile-strength testing revealed that ductility increased alongside reduced molecular weight of poly(ethylene glycol), also suggesting that polymer branching occurred due to side reactions of isocyanate. Based on the envisaged biomedical applications for these polymers, cytotoxicity tests were carried out and the cytotoxic effect was only moderate in the case of 100% polymer extract prepared according to ISO standard 10993-12. In their research, the authors focused on preparing metal-free, catalysed synthesis of polyester urethanes, which could prove useful to numerous biomedical applications.

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