Home  About us  Contact
 

Polyurethane Elastomers (polyurethane + elastomer)

Distribution by Scientific Domains
Polymers and Materials Science70%
Chemistry30%

Selected Abstracts

Structure and properties of cross-linked polyurethane copolymers

ADVANCES IN POLYMER TECHNOLOGY, Issue 3 2009
S. Oprea
Abstract Polyurethane elastomers based on polyester diols and aromatic or aliphatic diisocyanates can be used as vibration dampers and isolation materials. Two series of cross-linked polyurethanes with various hard segment structures and different amounts were prepared and thermomechanical properties of these materials were studied. Cross-linked polyurethane copolymers composed of poly(ethylene adipate)diol as soft segment and 4,4,-methylenebis(phenylisocyanate), 1,6-hexamethylene diisocyanate, and diols glycerin, 1,4-butanediol, and 1,6-hexanediol as hard segments were synthesized by a two-step process. The networks have been prepared by end-linking a mixture of the bifunctional precursor chains with trifunctional cross-linkers at off-stoichiometric ratios. The results show that the cross-link and the polyurethane hard segment interaction play a special role in the interconnected chain density and its magnitude is revealed by the mechanical properties. Of most importance, maximum stress, tensile modulus, and elongation at break increased significantly at the 22 wt % composition of hard segment content. Interchain cross-linking improves thermal stability, which was measured by thermogravimetric analysis and differential scanning calorimetry. Cross-linked polyurethane behaves as an elastomer and is useful for shock, noise, and vibration control. © 2009 Wiley Periodicals, Inc. Adv Polym Techn 28:165,172, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20155 [source]

Structure-property relationship in polyurethane elastomers containing starch as a crosslinker

POLYMER ENGINEERING & SCIENCE, Issue 5 2000
Sonal Desai
Polyurethane elastomers were synthesized using polypropylene glycol (PPG 2000) as the polyol and starch as the multifunctional crosslinker in varying concentrations. Thermal and mechanical properties were measured by DSC, DMA and tensile tests. The morphology was examined by SEM. The swelling behavior of the polyurethanes in various solvents was investigated and the solubility parameter was determined. All these properties were compared with those of polyurethanes containing 1,1,1 -trimethylol propane (TMP) as the crosslinker. Starch-based polyurethanes exhibited better mechanical properties. The effect of varying the starch:TMP ratio on the mechanical strength was also studied. With increasing starch content, the tensile strength and elongation increased. The starch-based PUs exhibited two glass transitions, whereas TMP-based PUs exhibited one Tg. No significant difference in the Tgs of the two PUs was observed. The activation energy of St-PU calculated from DMA was 69 kcal/mol. Soil degradation tests indicated greater biodegradability in polyurethanes containing starch than in those containing TMP. [source]

Fireproofing of polyurethane elastomers by reactive organophosphonates

POLYMER INTERNATIONAL, Issue 1 2003
Wassef El Khatib
Abstract Polyurethane elastomers were prepared with hydroxytelechelic polybutadiene (HTPB) as polyol, modified 4,4,-diphenylmethane diisocyanate (modified MDI) as liquid polyisocyanate, and phosphonate diols as chain extenders and flame retardant compounds. These phosphonate diols were synthesized by radical thiol,ene addition of allyl or vinyl dialkyl phosphonate to 3-mercapto-1,2-propanediol. For various percentages of phosphorus (0 to 3%, w/w), polyurethane elastomers remain stable up to 250,°C. The percentage of residual char at 600,°C increases with increasing phosphorus content. For the soft segments, no variation in the glass transition temperature (Tg) is observed as the percentage of P increases, whereas the Tg of hard segments increases. Above 0.5% phosphorus content, the limiting oxygen index (LOI) becomes higher than the percentage of oxygen in the air. © 2003 Society of Chemical Industry [source]

Novel Segmented Thermoplastic Polyurethanes Elastomers Based on Tetrahydrofuran Ethylene Oxide Copolyethers as High Energetic Propellant Binders

PROPELLANTS, EXPLOSIVES, PYROTECHNICS, Issue 1 2003
Fu-Tai Chen
Abstract Novel thermoplastic polyurethane (TPU) elastomers based on copolyether (tetrahydrofuran ethylene oxide) as soft segments, isophorone diisocyanate and 1,4-butanediol as hard segments were synthesized for the purpose of using as propellant binders. In order to increase the miscibility of thermoplastic polyurethane elastomers with nitrate ester, polyethylene glycol (PEG) is incorporated in the co-polyether (tetrahydrofuran ethylene oxide) as soft segment. When the molecular weight and content of polyethylene glycol are controlled to 4000 and 6% of soft segments, respectively, the properties of thermoplastic polyurethane elastomers are most perfect. If plasticizing ratio of nitrate ester to thermoplastic polyurethane elastomers exceeds 4 no crystallinities are determined at room temperature. The propellant samples were prepared by a conventional absorption-rolling extrusion process and the mechanical and combustion properties evaluated afterwards. The maximum impulse reaches up to 265,270 s which is a little bit higher than that of a HTPB propellant. The measured results reveal a promising TPE propellant candidate which shows good processing temperature (<393,K) and excellent mechanical properties. An attracting feature which can be pointed out is that the burning rate pressure exponent reaches as low as 0.36 without the addition of burning rate catalysts. This enables an easy control of propellant combustion. [source]

Effect of UV and hygrothermal aging on the mechanical performance of polyurethane elastomers

JOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2008
H. Aglan
Abstract In this study, the effects of environmental aging on the mechanical performance of elastomeric polyurethane (PU) were investigated using two accelerated aging techniques, namely, ultraviolet (UV) and hygrothermal (HT). Samples were prepared and subjected to UV and HT exposure for a period of 5 months and removed and mechanically tested at different time intervals. Differential scanning calorimetry (DSC) was performed. A noticeable change in the chemical structure of the PU after 1 month of UV exposure was found, however, that was not the case after 1 month of HT exposure. The stress and strain to failure, tearing energy, and storage modulus were evaluated at different intervals for both aging techniques. It was found that the UV exposure caused severe degradation of the PU in comparison with the HT. A reduction of more than 98% in the tearing energy was observed for the UV-exposed samples after 5 months when compared with only a 35% reduction in the tearing energy for the HT-exposed samples. A similar trend was observed for tear strength and storage modulus. The degradation mechanisms of the PU elastomers have been identified using SEM and correlated with the tearing energy. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source]

Poly(tetramethylene ether) glycol containing acetal linkages: New PTMG-based polyol for chemically recyclable polyurethane thermoplastic elastomer

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 5 2008
Tamotsu Hashimoto
To develop new chemically recyclable polyurethane elastomers, the poly(tetramethylene ether) glycol (PTMG) containing acetal linkages (PTMG-Acetal-OH) was prepared and subjected to the polyurethane synthesis with 4,4(-diphenylmethane diisocyanate (MDI) and 1,4-butanediol (BD; chain-extender). The obtained polyurethane (PTMG-Acetal-PU) shows very similar mechanical and thermal properties to those of the conventional PTMG-based thermoplastic polyurethane elastomers (PTMG-PU). The acid treatment of PTMG-Acetal-PU at room temperature caused hydrolysis reaction of their acetal units to regenerate PTMG as a degradation product. [source]

Structure-property relationship in polyurethane elastomers containing starch as a crosslinker

POLYMER ENGINEERING & SCIENCE, Issue 5 2000
Sonal Desai
Polyurethane elastomers were synthesized using polypropylene glycol (PPG 2000) as the polyol and starch as the multifunctional crosslinker in varying concentrations. Thermal and mechanical properties were measured by DSC, DMA and tensile tests. The morphology was examined by SEM. The swelling behavior of the polyurethanes in various solvents was investigated and the solubility parameter was determined. All these properties were compared with those of polyurethanes containing 1,1,1 -trimethylol propane (TMP) as the crosslinker. Starch-based polyurethanes exhibited better mechanical properties. The effect of varying the starch:TMP ratio on the mechanical strength was also studied. With increasing starch content, the tensile strength and elongation increased. The starch-based PUs exhibited two glass transitions, whereas TMP-based PUs exhibited one Tg. No significant difference in the Tgs of the two PUs was observed. The activation energy of St-PU calculated from DMA was 69 kcal/mol. Soil degradation tests indicated greater biodegradability in polyurethanes containing starch than in those containing TMP. [source]

Fireproofing of polyurethane elastomers by reactive organophosphonates

POLYMER INTERNATIONAL, Issue 1 2003
Wassef El Khatib
Abstract Polyurethane elastomers were prepared with hydroxytelechelic polybutadiene (HTPB) as polyol, modified 4,4,-diphenylmethane diisocyanate (modified MDI) as liquid polyisocyanate, and phosphonate diols as chain extenders and flame retardant compounds. These phosphonate diols were synthesized by radical thiol,ene addition of allyl or vinyl dialkyl phosphonate to 3-mercapto-1,2-propanediol. For various percentages of phosphorus (0 to 3%, w/w), polyurethane elastomers remain stable up to 250,°C. The percentage of residual char at 600,°C increases with increasing phosphorus content. For the soft segments, no variation in the glass transition temperature (Tg) is observed as the percentage of P increases, whereas the Tg of hard segments increases. Above 0.5% phosphorus content, the limiting oxygen index (LOI) becomes higher than the percentage of oxygen in the air. © 2003 Society of Chemical Industry [source]

Novel Segmented Thermoplastic Polyurethanes Elastomers Based on Tetrahydrofuran Ethylene Oxide Copolyethers as High Energetic Propellant Binders

PROPELLANTS, EXPLOSIVES, PYROTECHNICS, Issue 1 2003
Fu-Tai Chen
Abstract Novel thermoplastic polyurethane (TPU) elastomers based on copolyether (tetrahydrofuran ethylene oxide) as soft segments, isophorone diisocyanate and 1,4-butanediol as hard segments were synthesized for the purpose of using as propellant binders. In order to increase the miscibility of thermoplastic polyurethane elastomers with nitrate ester, polyethylene glycol (PEG) is incorporated in the co-polyether (tetrahydrofuran ethylene oxide) as soft segment. When the molecular weight and content of polyethylene glycol are controlled to 4000 and 6% of soft segments, respectively, the properties of thermoplastic polyurethane elastomers are most perfect. If plasticizing ratio of nitrate ester to thermoplastic polyurethane elastomers exceeds 4 no crystallinities are determined at room temperature. The propellant samples were prepared by a conventional absorption-rolling extrusion process and the mechanical and combustion properties evaluated afterwards. The maximum impulse reaches up to 265,270 s which is a little bit higher than that of a HTPB propellant. The measured results reveal a promising TPE propellant candidate which shows good processing temperature (<393,K) and excellent mechanical properties. An attracting feature which can be pointed out is that the burning rate pressure exponent reaches as low as 0.36 without the addition of burning rate catalysts. This enables an easy control of propellant combustion. [source]