Structure–Property Relations in Polyurethanes

Szycher, Michael

doi:10.1201/b12343-4

Cited by 113 publications

(204 citation statements)

References 7 publications

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“…With a complete conversion of epoxide group per triglyceride, a maximum total number of OH groups was estimated around 4–6. However, with these high functionalities, rigid foams are expected [ 29 , 30 , 31 ]. A fine tuning of the reaction conditions in polyols synthesis could provide polyols with relatively high hydroxyl equivalent weight, attractive for the synthesis of flexible PUFs.…”

Section: Resultsmentioning

confidence: 99%

“…The initial viscosity of bio-polyols is one of the most important factors which influence the cellular structure of the resultant foams, affecting the generation and distribution of the cells formed by the blowing agent [ 40 ]. The relatively high viscosity of the bio-polyols ( Table 2 ) with respect to the reference PPG (viscosity equal to 0.63 Pa·s) facilitates the formation of the framework of the urethane group in the stage of the gel reaction between the bio-polyol and isocyanate with a low concentration of gel catalyst, resulting in a dense structure and in the high apparent density of the prepared foams, in particular at low water concentration [ 22 , 29 ] and when the aromatic group is inserted in the vegetable oil backbone (Tolo 10 and 11).…”

Section: Resultsmentioning

confidence: 99%

“…PU intermediates were synthesized in a closed vessel at atmospheric pressure under mechanical stirring. Quasi-prepolymers [ 29 ] were prepared by first reacting a large excess of a isocyanate (free isocyanate content about 30 wt %) with PPG for 40 min in the presence of dibutyltin dilaurate (0.01 wt %) and silicone surfactant (0.5 wt %), then afterwards the isocyanate-terminated intermediate, that was formed in the previous step, was reacted with bio-polyol adding again a small amount of catalyst (0.01 wt %). The ratio between PPG and bio-based polyol is 1:2.…”

Section: Methodsmentioning

confidence: 99%

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Flexible Polyurethane Foams from Epoxidized Vegetable Oils and a Bio-Based Diisocyanate

et al. 2021

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Bio-polyols from epoxidized soybean and linseed oils and caprylic acid or 3-phenyl butyric acid were prepared using an environmentally friendly, solvent-free method evaluating the presence of triethylamine as catalyst. Side reactions, leading to a cross-linking structure with high density, were reduced, introducing the catalyst and properly tuning the reaction conditions. A medium functionality value of around 3 along with a hydroxyl number up to around 90 mg KOH/g, narrow polydispersity index, and relatively low molecular mass up to 2400 g/mol were the experimental targets. From selected bio-polyols and an aliphatic partially bio-based isocyanate, a series of water blown polyurethane (PU) foams was produced, estimating the effect of the chemical nature of substituents in the polyol backbone on the PU properties. The apparent density of the foams was in the range of 79–113 kg/m3, with higher values for foams from the aromatic acid. Flexible polyurethane foams with open cell structure from bio-based polyols were obtained, with higher cavity size and lower pore sizes for foams from caprylic acid. The bio-based flexible PU foams showed comparable Young’s moduli (14–18 kPa) and compression deflection values (4.6–5.5 kPa) and exhibited an almost complete recovery of their initial size.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Flexible Polyurethane Foams from Epoxidized Vegetable Oils and a Bio-Based Diisocyanate

et al. 2021

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“…In contrast, the soft segments consist of a polyester or polyether polyol [ 36 , 37 ]. The main difference between TPU and conventional elastomers is that in conventional elastomers, the cross-linking points generating material strength are formed by covalent bonds, whereas in thermoplastic elastomers such as TPU, they appear in the form of partially crystalline areas [ 38 ].…”

Section: Introductionmentioning

confidence: 99%

Melt Spinning of Highly Stretchable, Electrically Conductive Filament Yarns

et al. 2021

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Electrically conductive fibers are required for various applications in modern textile technology, e.g., the manufacturing of smart textiles and fiber composite systems with textile-based sensor and actuator systems. According to the state of the art, fine copper wires, carbon rovings, or metallized filament yarns, which offer very good electrical conductivity but low mechanical elongation capabilities, are primarily used for this purpose. However, for applications requiring highly flexible textile structures, as, for example, in the case of wearable smart textiles and fiber elastomer composites, the development of electrically conductive, elastic yarns is of great importance. Therefore, highly stretchable thermoplastic polyurethane (TPU) was compounded with electrically conductive carbon nanotubes (CNTs) and subsequently melt spun. The melt spinning technology had to be modified for the processing of highly viscous TPU–CNT compounds with fill levels of up to 6 wt.% CNT. The optimal configuration was achieved at a CNT content of 5 wt.%, providing an electrical resistance of 110 Ωcm and an elongation at break of 400%.

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“…We choose commercially available methylenedi-1,4phenylene)bismaleimide (BMI) as a crosslinker. It is worthwhile to say that a significant advantage of the furan-terminated prepolymer is its longer shelf-life and moisture insensitiveness compared to its regular isocyanate-terminated counterparts [42].…”

Section: Introductionmentioning

confidence: 99%

Thermally Remendable Polyurethane Network Cross-Linked via Reversible Diels–Alder Reaction

et al. 2021

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We prepared a series of thermally remendable and recyclable polyurethanes crosslinked via reversible furan-maleimide Diels–Alder reaction based on TDI end-caped branched Voranol 3138 terminated with difurfurylamine and 4,4′-bis(maleimido)diphenylmethane (BMI). We showed that Young modulus strongly depends on BMI content (from 8 to 250 MPa) that allows us to obtain materials of different elasticity as simple as varying BMI content. The ability of DA and retro-DA reactions between furan and maleimide to reversibly bind material components was investigated by NMR spectroscopy, differential scanning calorimetry, and recycle testing. All polymers obtained demonstrated high strengths and could be recovering without significant loss in mechanical properties for at least five reprocessing cycles.

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Structure–Property Relations in Polyurethanes

Cited by 113 publications

References 7 publications

Flexible Polyurethane Foams from Epoxidized Vegetable Oils and a Bio-Based Diisocyanate

Flexible Polyurethane Foams from Epoxidized Vegetable Oils and a Bio-Based Diisocyanate

Melt Spinning of Highly Stretchable, Electrically Conductive Filament Yarns

Thermally Remendable Polyurethane Network Cross-Linked via Reversible Diels–Alder Reaction

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