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Polyurethane

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Nguyễn Gia Hào

Academic year: 2023

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Inquiries regarding the use of the book should be directed to INTECH's Rights and Permissions Department (permissions@intechopen.com). The publisher assumes no responsibility for injury or damage to persons or property arising from the use of materials, instructions, methods or ideas contained in the book.

Polyurethane: An Introduction

  • Introduction
    • History of polyurethane
  • Raw materials
    • Isocyanates
    • Polyols
    • Additives
  • Chemistry of PU
  • Mechanism
    • Reaction in the absence of a catalyst
    • Reaction in the presence of a catalyst
  • Hazards
  • Conclusion

In diisocyanates, the presence of the electron withdrawing second isocyanate increases the reactivity of the first. In some of the reactions, CO2 is released which helps in the formation of PU foams.

Figure 1. Common isocyanates
Figure 1. Common isocyanates

Author details

Although PUs are chemically inert in their fully reacted form, the risk of asthmatic symptoms occurs at human exposure even at lower concentrations due to the volatility associated with isocyanates, the risk of asthmatic symptoms occurs at human exposure, even at lower concentrations. Therefore, persons working with isocyanates must be equipped with appropriate protective devices such as gloves, masks, respirators, goggles, and more as a safety measure.

Acknowledgement

The catalytic activity of amines roughly parallels the basic strength of amines except where steric hindrance becomes pronounced. They are also grateful to the Head of the Department of Chemistry, Jamia Millia Islamia (A Central University), for support in carrying out the work.

New Liquid Crystalline Polyurethane Elastomers Containing Thiazolo [5,4d]

Thiazole Moiety: Synthesis and Properties

Experimental 1. Materials

  • Synthesis of monomers and polymers
  • Measurements

Thermal stability of LCPUE was determined by thermogravimetric analyzer (Perkin Elmer Pyris series 6) under nitrogen purging and with 10oC/min heating rate and the heating was done up to 800oC. Various mesomorphic behaviors are exhibited with different types of mesogenic units in preparation of LCPUE.

Results and discussion 1. Preparation of chain extender

  • Polymer synthesis
  • Structural elucidation
  • Thermal and liquid crystalline behavior of polymers
  • Tensile properties

The fact that differentiates LCPUE VI and LCPUE VII was the presence of the methoxy group and this was proven in the FTIR spectrum of LCPUE VIIa, where a peak displayed at the region of 1024.27 cm-1 corresponds to the methoxy group. Due to the higher range between Tm and Ti of LCPUE VIa, the thermal properties of this polymer are higher and more stable compared to LCPUE VIIa.

Figure 1. FTIR spectrum of LCPUE VIIa
Figure 1. FTIR spectrum of LCPUE VIIa

Studies on thermotropic liquid crystalline polyurethanes. III. Synthesis and properties of polyurethane elastomers using different Synthesis and Properties of Thermotropic Liquid Crystalline Polyurethane Elastomers (II): Effect of Chain Extender Structure Containing an Imid Unit.

The Modification of Polyurethanes by Highly Ordered Coordination

  • Coordination compounds based on the aromatic isocyanates and copper (II) chloride for the synthesis of polyurethanes
  • Reactions of aromatic isocyanates and urethane prepolymers with coordination compounds of iron (III)
  • Modification of urethane prepolymer by coordination compounds of copper (I, II)
  • CH 2 NOH
  • NCO ,
    • Modification of polyurethanes by heteronuclear complexes based on molybdenum (V) and copper (II) chlorides
    • Catalytic properties of coordination compounds of copper in the reaction with isocyanate and urethane groups
    • The use of highly ordered coordination compounds of copper for receiving the rigid polyurethane foam
    • Conclusion
    • References

Some of the Cu(II) ions interacting with DEHA reduce the oxidation level and change into Cu(I) (see Fig. 5). We measured the dependence of the volume resistivity (ρv) of polyurethanes on the concentration of metal complex modifier (Fig. 11).

Figure 1.  Formation of polynuclear complexes of azoaromatic compounds.
Figure 1. Formation of polynuclear complexes of azoaromatic compounds.

Bottom-Up Nanostructured Segmented Polyurethanes with Immobilized in situ

Compounds – Polymer Topology – Structure and Properties Relationship

Materials, methods and instrumentations

This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. This is a paper distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Heterogeneity of metal containing polyurethanes 1. Structural heterogeneity of PU according to X-ray data

  • Dynamic heterogeneity of PU according to EPR data
  • Thermodynamic heterogeneity of PU according to DSC data
  • The formation of ordered micro regions in metal containing PUs

In addition, the influence of the metal chelate compound on the dynamics of PU also depends on the topology of the polymer. One of them was formed at the "polymer-support" interface (PU surface molded on a Teflon support), and the other was formed at the "polymer-air" interface (PU surface molded in air).

Figure 1 represents the WAXS and Figure 2 presents SAXS intensity profiles of metal-free PU  and PU modified with metal   -diketonate
Figure 1 represents the WAXS and Figure 2 presents SAXS intensity profiles of metal-free PU and PU modified with metal  -diketonate

Influence of metal chelate modifiers on surface properties of polyurethanes

Whereas, formed on the surface at the "polymer-air" boundary (Fig. 8, b), the size and amount of crystals are significantly smaller. Therefore, the surface properties of europium with LPU and CPU were compared for surfaces formed at the boundary of "polymer-air" and "polymer-support" using contact wetting angle measurement.

The influence of polymer topology and modifier content on the luminescent properties of segmented polyurethanes

According to (Lobko et al., 2010), the PU matrix can enhance the photoluminescence of europium chelate compounds introduced into the polymer in situ. As can be seen, the luminescence of the Eu (3+) chelate compounds introduced into the PU matrix (only 1% wt.) is more intense than the luminescence of the isolated metal chelate compounds (100% wt.).

Table 5.  The contact wetting angle (θ) and surface tension (  ) of PU films. The standard liquid is  ethylene glycol (EG) γ ЕG-air  = 48,36 mN/m
Table 5. The contact wetting angle (θ) and surface tension (  ) of PU films. The standard liquid is ethylene glycol (EG) γ ЕG-air = 48,36 mN/m

Dielectric relaxation and conductivity

  • The complexing of the metal chelate compound with PU matrix according to the electron spectroscopy
  • Complex formation in the “polymer-modifier” system according to EPR data The EPR data confirm the complexing between the metal chelate compound and PU
  • Low molecular probes dynamic and formation of additional network of the coordination bonds in metal containing polyurethanes

Thermal dependence of relaxation time (τmax) for CPE with different content of Eu (3+) chelating compound. Complexation of metal chelate compound with PU matrix according to electron spectroscopy electron spectroscopy.

Figure 10.  The luminescence spectra (λ ex.  = 365 nm) of the europium (3+) chelate compounds (a) and of  CPU films with 1%wt
Figure 10. The luminescence spectra (λ ex. = 365 nm) of the europium (3+) chelate compounds (a) and of CPU films with 1%wt

Conclusion

The sharp decrease of the overall component and a particle of the diffusion coefficient for the metal containing PU compared to the metal-free PU indicates the occurrence of spatial barriers to the dynamics of the liquid molecule.

The effect is caused by complex formation between metal chelate compound and functional groups of the forming polymer. Effect of metal compounds on the surface properties of the solid polyurethanes formed in their presence.

Thermal Analysis of Polyurethane Dispersions Based on Different Polyols

Water-based polyurethane dispersions

Due to incompatibility between the two segments of the polymer chain, the hard segment separates and aggregates into domains that act as reinforcing fillers for the soft segment. The critical step where the different synthetic routes differ is the dispersion of the prepolymer in water and the molecular weight build-up.

Ingredients for water–based PUD

  • Various methods for preparing water–based PUD

The degree of phase separation as well as the concentration of the hard segments are contributing factors to the good properties of PUD. Such ionomeric groups are absolutely necessary for the formation of dispersions, because they act as internal surfactants, and are not incorporated into the chain of the solvent-based PU.

Thermal analysis of PU

PUD is now one of the fastest developing and most active branches of PU chemistry. The ionic group content, solids content, segmented structure, molecular weight of the macroglycol, the type of chain extender and the hard/soft segments ratio determine the properties of PUD.

Water-based PUD based on poly(propylene glycol) and selective catalyst

  • Experimental
  • Results and discussion

The thermal stability of PU has been extensively studied due to its great importance. The degradation profiles of PU cast films obtained from water-based dispersions were influenced by the type of chain extender, the length of the hard segment and the type of catalysts.

Figure 1.  TG curves of PUD without catalyst with EG (1) and PG (2) as chain extender
Figure 1. TG curves of PUD without catalyst with EG (1) and PG (2) as chain extender

Water-based PUD based on glycolized products obtained from recycled poly (ethylene terephthalate)

  • Experimental
  • Synthesis of PUD based on glycolyzed products with molar ratio PET/glycol, 1:2
  • Synthesis of PUD based on glycolyzed products with molar ratio PET/glycol, 1:10

Anionic PUD based on glycolized products with a PET/glycol molar ratio of 1:2 was prepared using a modified acetone procedure. It was verified that the thermal stability is affected by the type of glycol and the different molar ratio of PET repeating unit to glycol in the glycolysis reaction.

Figure 4. TG curves (a) and DTG curves (b) of PUD synthesized from glycolized oligoester PET/PG with  molar ratio 1:2 (1) and 1:10 (2)
Figure 4. TG curves (a) and DTG curves (b) of PUD synthesized from glycolized oligoester PET/PG with molar ratio 1:2 (1) and 1:10 (2)

Waterborne PUD based on polycarbonate diols (PCD)

  • Experimental

However, the degradation mechanism was very complex due to the different stabilities of the hard and soft segments. The decomposition temperature of the soft segments is produced at 329-338 oC and the weight loss is increased by reducing the DMPA content 20.9 and 23.5 to 6.2 wt% in PU ionomers.

Conclusions

The degradation profile of the dispersions depended on the molar ratios of PET to glycol in glycolyzed products. 2010) Effect of the chain extender and selective catalyst on the thermo-oxidative stability of aqueous polyurethane dispersions.

Figure 5.  TGA curves (a)  and DTA curves (b) of cured films of PUD based on PCD with 4.5% DMPA  (1), 7.5% DMPA (2), 10% DMPA (3)
Figure 5. TGA curves (a) and DTA curves (b) of cured films of PUD based on PCD with 4.5% DMPA (1), 7.5% DMPA (2), 10% DMPA (3)

Polyurethane Flexible Foam Fire Behavior

  • Polyurethane foam morphology
  • Polyurethane flexible foam fire retardants 1. Halogenated phosphorous flame retardants
    • Halogen-free flame retardants
  • Properties of the polyurethane flexible foam with different types of fire retardants
    • Foaming process
    • Reactivity
    • Fire properties
    • Physical properties
  • Statistical method
    • Cone calorimeter–FMVSS 302
    • Properties–FMVSS 302
  • References

Expansion factor, which is related to the free rise density (FRD), is reduced with the addition of EG and melamine in the foam. The porosity index of the foam is highly correlated with the SnOct range used in the foam manufacture.

Figure 1. Condensation reaction of isocyanate to make Carbodiimide
Figure 1. Condensation reaction of isocyanate to make Carbodiimide

Applications

Gharehbaghi, Journal of Cellular Plastics 30 December 2009, An investigation of reactivity, mechanical and fire properties of Pu flexible foam [2] Jerome Lefebvre and Michel Le Bras, Benoit Bastin and Rakesh Paleja, Rene Delobel. Ahmadi, Polyurethane Flexible Foam Fire Resistant by Melamine and Expandable Graphite: Industrial Approach, Journal of Cellular Plastics, published online September 19, 2011.

Polyurethane in Urological Practice

Application

  • Experimental part: Patients, stents and characterization methods
  • Clinical results
  • Characterization results on starting stents surfaces
  • Characterization results on the indwelled stents
  • Results summary

FESEM (JEOL JSM 6500F) for morphological characterization of the stent surface and the encrustations formed;. The spectrum of the heparin-coated PU surface (in red) shows some novel features with respect to the reference PU stent (in black).

Table 1. Stents types and indwelling periods of the PU, heparin-coated and diamond-like carbon  coated PU stents
Table 1. Stents types and indwelling periods of the PU, heparin-coated and diamond-like carbon coated PU stents

Conclusion

From EDS analysis, no particular inorganic compounds were identified on the surface of the DLC-coated stent (data not shown). We attributed reduction of the biofilm to the presence of surface treatments (heparin or DLC coatings) on the polyurethane surface.

Polyurethane as Carriers of Antituberculosis Drugs

Polymeric microparticles for tuberculosis treatment

Concentration of the crosslinker up to 7.5% caused an increase in the entrapment efficiency and the extent of drug release. Chemotherapeutic potential of ALG nanoparticle-encapsulated econazole and antituberculosis drugs was studied against murine tuberculosis (Ahmad et al., 2007).

Polyurethane microparticles as carriers of drug

Drug release from the microspheres was studied in simulated gastric and intestinal fluids. Microencapsulation of the water-soluble pesticide monocrotophos (MCR) using PU as a carrier polymer was developed using two types of polymethyllauryl acrylate (PLMA) steric stabilizers, macrodiol and PLMA-g-PEO graft copolymer (Shukla et al., 2002).

Polyurethane microparticle as carrier of antituberculosis drug

The structural and thermal properties of the resultant microcapsules and the release profile of OVA from the wall membranes were studied. And drug encapsulation is possible during the process of polymer wall formation (Batyrbekov et al., 2009; Iskakov et al., 2004).

OCN NCO

  • Polyurethane foams as carriers of antituberculosis drugs

The use of PU carrier ensures a stable bacteriostatic concentration of the chemotherapeutic agents for 5-7 days. This research was financially supported by a grant from the Ministry of Education and Science of the Republic of Kazakhstan. The authors thank Dr.

Figure 1.  Scheme of reaction between PEG and TDI with polyurethane formation.
Figure 1. Scheme of reaction between PEG and TDI with polyurethane formation.

Use of Polyurethane Foam in Orthopaedic

Biomechanical Experimentation and Simulation

Basic material properties of rigid polyurethane foam

Due to such similarities, polyurethane (PU) foams have become popular surrogates for human cancellous bone testing, and many researchers have quantitatively characterized the material properties of polyurethane foam to investigate the suitability and utility of PU foam as a bone analog. In the second part, a review of the literature focusing on the use of polyurethane foam in biomechanical experiments will be presented.

Figure 1.  Microstructures of cancellous bone and polyurethane foam.
Figure 1. Microstructures of cancellous bone and polyurethane foam.

The use of PU foams in orthopaedic implant testing

Farshad et al., 2011) used PU foam blocks to test bone tunnels drilled during anterior cruciate ligament reconstruction. Another interesting development in the use of PU foam in orthopedic biomechanics is the development of so-called composite bones.

Figure 3. Compressive stress-strain curves for several relative densities (ρ * /ρ s )of wet cancellous bone  (modified from Figure 11-5 in Gibson and Ashyby, 1997)
Figure 3. Compressive stress-strain curves for several relative densities (ρ * /ρ s )of wet cancellous bone (modified from Figure 11-5 in Gibson and Ashyby, 1997)

Use of PU-foams in device and implant testing for bone grafting and acetabular fractures

  • Identification of optimal design parameters in bone grafting tools with PU- foams
  • Development and validation of finite element fracture predictions with PU- foam based synthetic bones
  • Development and validation of finite element predictions of the stability of fracture fixation with PU-foam based synthetic bones

Despite great advances in the treatment of this fracture over the past several decades, one medical textbook states that “acetabulum fractures remain a puzzle to the orthopedic surgeon (Tile et al., 2003).” The main reason for this problem is the complexity of acetabulum fractures. In addition, acetabulum fractures depend on many variables, such as the type of force that caused the fracture, the direction of movement, the damage to the articular surface, as well as the anatomical type of fracture (ie, the shape of the fragments).

Figure 6.  Bone graft harvester and its major parameters
Figure 6. Bone graft harvester and its major parameters

Hình ảnh

Figure 5. Polarized optical images of (a) LCPUE VIa (181 o C), (b) LCPUE VIb (162  o C) and (c) LCPUE  VIc (133  o C)
Figure 6.  Polarized optical images of (a) LCPUE VIIa (170  o C), (b) LCPUE VIIb (148  o C) and (c) LCPUE  VIIc (129  o C)
Figure 5. Polarized optical images of (a) LCPUE VIa (181 o C), (b) LCPUE VIb (162  o C) and (c) LCPUE  VIc (133  o C)
Figure 4.  The Mössbauer spectrum of metal complex system based on FeCl 3  and EA.
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