Polyurethanes

Reghunadhan, Arunima; Thomas, Sabu

doi:10.1016/b978-0-12-804039-3.00001-4

Cited by 34 publications

(21 citation statements)

References 29 publications

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“…Further work could apply direct volume correlation following in‐situ tensile tests using micro CT scans of “heat‐set” samples to inspect whether touching ribs are stuck together or able to separate. Aspects of thermo‐mechanical conversions not included in this work were annealing or cooling rate and relaxation of residual stresses by hand stretching . Samples fabricated at 160 °C for 180 min only exhibit compressive NPR after unconstrained re‐heating (≈0 then ≈−0.2, before [Figure a] and after [Figure c] re‐heating, respectively), possibly be due to thermal relaxation.…”

Section: Discussionmentioning

confidence: 99%

“…Thermoplastic PU consists of hard (ordered) and soft (amorphous) segments . Copolymers and cross‐linkers can affect PU characteristics .…”

Section: Introductionmentioning

confidence: 99%

“…Thermoplastic PU consists of hard (ordered) and soft (amorphous) segments . Copolymers and cross‐linkers can affect PU characteristics . Softening temperature (or point) has been used to describe a temperature range whereby auxetic foam can be formed following heating then cooling under compression.…”

Section: Introductionmentioning

confidence: 99%

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Effects of Heat Exposure and Volumetric Compression on Poisson's Ratios, Young's Moduli, and Polymeric Composition During Thermo‐Mechanical Conversion of Auxetic Open Cell Polyurethane Foam

Duncan

Clegg

Essa

et al. 2018

Physica Status Solidi (b)

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The effects of thermo-mechanical auxetic foam conversion parameters on the Young's modulus and Poisson's ratio of open-cell polyurethane foam are related to changes in chemical bonding and cell structure. Applied volumetric compression, conversion temperature, and duration are reported on foam Young's modulus, Poisson's ratio, and structural stability. Fourier transform infrared spectral analysis on samples converted at and above 160 C strongly indicates a hydrogen bond interaction increase in urea groups (C¼O---H-N) and an increase in hydrogen bonding population. Spectral changes inferred soft segment degradation following extensive heat exposure (200 C, 180 min), specifically a shift and intensity change in CH 2 and C-O-C polyol bands and a broad baseline increase between 3600 and 2400 cm À1 . These changes are linked to (i) resistance to dimensional recovery over time and during re-heating; (ii) Poisson's ratio becoming negative, then zero in tension or marginally positive in compression; (iii) Young's Modulus reducing then increasing; (iv) mass loss, evidenced by thermogravimetric analysis increasing from 150 C. The minimum mean values of Poisson's ratio of %À0.2 (to 10% compression/tension) are comparable to other studies. All samples that retain their imposed compression over time are isotropic, with near constant Young's moduli and Poisson's ratio (to 10% compression/tension).

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Section: Discussionmentioning

confidence: 99%

“…Thermoplastic PU consists of hard (ordered) and soft (amorphous) segments . Copolymers and cross‐linkers can affect PU characteristics .…”

Section: Introductionmentioning

confidence: 99%

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Effects of Heat Exposure and Volumetric Compression on Poisson's Ratios, Young's Moduli, and Polymeric Composition During Thermo‐Mechanical Conversion of Auxetic Open Cell Polyurethane Foam

Duncan

Clegg

Essa

et al. 2018

Physica Status Solidi (b)

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“…PUr results from the reaction between hydroxyl (-OH) groups and isocyanate groups (-NCO) while PU is obtained from a reaction of amine (-NH 2 ) and NCO groups. [10][11][12][13][14][15][16] Both PU and PUr possess hard and soft domains. Their elastomers are currently used as protective materials for different applications owing to their chemical resistance and toughness.…”

Section: Introductionmentioning

confidence: 99%

Preparation, characterization, and influence of polyurea coatings on their layered composite materials based on flexible rebonded polyurethane

Temizkan¹,

Eroğlu²,

Ergün

et al. 2021

Polymer Engineering & Sci

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Preparation and characterization of a series of polyurea (PU) coatings and their influences on layered composite materials based on rebonded polyurethane (PUr) for floor application are described in terms of the raw materials, formulation, and application performance. While PU coatings show almost the same FTIR peaks, thermogravimetric analyses results reveal that thermal stabilities of the PU coatings are slightly enhanced with the use of trifunctional polyamine compound and one step degradation takes place beyond 300 C. All PU coatings have very dense, smooth, and bubble-free surfaces whereas the cross-sectional SEM images exhibit pores of different sizes. Contact angle values of all PU coatings are bigger than 90 indicating that the surfaces are hydrophobic. Using propylene carbonate in the preparation of methylene diphenyl diisocyanate (MDI) prepolymer and the chain extender in the PU coating formulation impacts the mechanical and electrical properties of the PU coatings as well as layered PU/PUr composite materials. In conclusion, not only the controllable physicochemical and mechanical properties of layered PUr/PU composites but also the usage potential of recycled PU scraps in these layered composites are very promising for better floor applications.

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“…Polyurethanes (PUs) are polymeric materials consisting of several interconnected urethane groups forming a larger polymer of numerous commercial applications among which the most remarkable is their use as flame-retardant material, 1 surface coating, 2 and adhesives. 3 Conventionally, PU materials are synthesized using petroleum-based polyols that outrageously contributing to the global greenhouse effect.…”

Section: Introductionmentioning

confidence: 99%

Morphological studies on renewable castor oil-based nanocomposites with modified clay and MWCNTs as fillers

Mogha

Kaushik

2020

Polymers and Polymer Composites

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This research presents an analysis of castor oil-based polymer nanocomposites that can be used for numerous commercial applications. Due to the versatile chemical structure of castor oil, it can replace the petrochemical products and hence can be optimized as nontoxic bioresource for the production of nanocomposites with the incorporation of nanofillers in small quantities. It can be directly used as polyol resource without any chemical alteration for synthesis of polyurethane (PU) nanocomposites. The prepared PU nanocomposites were characterized by scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, wide angle X-ray diffraction, transmission electron microscopy (TEM), and mechanical properties. The compositional and structural studies indicate the formation of PU linkages and well dispersion of clay and multiwalled carbon nanotubes between the polymer–nanofiller phase, as shown by the morphological analysis using TEM. Also, there is an increase in the tensile strength and Young’s modulus values with the increase in the filler content.

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Polyurethanes

Cited by 34 publications

References 29 publications

Effects of Heat Exposure and Volumetric Compression on Poisson's Ratios, Young's Moduli, and Polymeric Composition During Thermo‐Mechanical Conversion of Auxetic Open Cell Polyurethane Foam

Effects of Heat Exposure and Volumetric Compression on Poisson's Ratios, Young's Moduli, and Polymeric Composition During Thermo‐Mechanical Conversion of Auxetic Open Cell Polyurethane Foam

Preparation, characterization, and influence of polyurea coatings on their layered composite materials based on flexible rebonded polyurethane

Morphological studies on renewable castor oil-based nanocomposites with modified clay and MWCNTs as fillers

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