Hyperbranched polyurethane

Hyperbranched polyurethanes are constmcted using phenol-blocked trifunctional monomers in combination with 4-methylbenzyl alcohol for end capping (11). Polyurethane interpenetrating polymer networks (IPNs) are mixtures of two cross-linked polymer networks, prepared by latex blending, sequential polymerization, or simultaneous polymerization. IPNs have improved mechanical properties, as weU as thermal stabiHties, compared to the single cross-linked polymers. In pseudo-IPNs, only one of the involved polymers is cross-linked. Numerous polymers are involved in the formation of polyurethane-derived IPNs (12). 

Hyperbranched polyurethanes, 25 461 Hypercarotenosis, 25 791 hypercloso designation, for boron hydrides, 4 174... 

Kumar and Ramakrishnan synthesized hyperbranched polyurethanes via the in-situ generation of 3,5-dihydroxyphenyl isocyanate from the corresponding carbonyl azide [98]. The degree of branching was determined as being close to 0.6 using NMR spectroscopy. The hyperbranched polyurethane was completely soluble in common organic solvents while the linear counterpart was completely insoluble. 

Maji et al. [136] have examined the effect of 30B loading on the mechanical properties of hyperbranched polyurethane (PU) nanocomposites. The extent of clay loading was varied from 2 to 16 phr. The nanocomposite containing 8 wt% 30B clay shows a 100% increase in the tensile strength as compared to unmodi-fied-clay-filled samples. Above 8 wt% clay loading, the mechanical properties decrease. The efficiency and good dispersion of 30B in the hyperbranched PU40... 

Spindler and Frechet1391 prepared hyperbranched polyurethanes by step-growth polymerization (Scheme 6.8) of protected, or blocked , isocyanate AB2 monomers. The method is dependent on the thermal dissociation of a carbamate unit into the corresponding isocyanate and alcohol moieties.140,411 Decomposition temperatures range from ca. 250°C for alkyl carbamates to ca. 120°C for aryl carbamates.1401... 

Kumar, A., and Ramakrishnan, S. J. 1996. Hyperbranched polyurethanes with varying spacer segments between the branching points. J. Polym. Sci. Polym. Chem., 34, 839-848. 

Besides covalent functionalization of carbon nanotubes, non-covalent interaction between CNTs and polyurethane can also help fabricate uniform CNT dispersion nanocomposites. A dominant improvement in the dispersion of MWNTs in hyperbranched polyurethane (HBPU) matrix was found, and good solubility of... 

Phenol blocked isocyanates also have been used to prepare hyperbranched polyurethanes by a step-growth polycondensation mechanism, using DBTDL as a catalyst. 4... 

Hyperbranched polyurethanes have also been synthesized by step-growth polymerization reactions such as the reaction between 3,5-diaminobenzoic acid and... 

Zhu, S. and Shi, W. Flame retardant mechanism of hyperbranched polyurethane acrylates used for UV curable flame retardant coatings. Polymer Degradation and Stability, 75, 543-547 (2001). 

Some hyperbranched polyurethanes with different compositions based on Mesua ferrea L. seed oil, sunflower oil, and so on, have been prepared by using monoglyceride and glycerol or monoglyceride with hyperbranched polyol. Hyperbranched polyurethanes have been prepared from soybean oil-modified hyperbranched polyol obtained via epoxidation and hydrofor-mylation. Castor oil-based hyperbranched polyurethanes have been synthesised using castor oil as the B3 monomer in an A2 -1- B3 approach. The A2 monomer, -NCO terminated pre-polymer was obtained by reacting MDI with PCL. The urethane reaction was carried out at ca. 110°C in the... 

Preparation of a hyperbranched polyurethane using a hyperbranched polyol core. 

Table 9.1 Mechanical properties of different vegetable oil-based hyperbranched polyurethanes with a long chain segment...

It has been found that Mesua ferrea L. seed oil-based thermoplastic hyperbranched polyurethane (HBPU) of the monoglyceride of the oil, PCL (M = 3000 g moT ), 2,4/2,6-toluene diisocyanate and glycerol with 30% hard segment (NCO/OH = 0.96), exhibit thermoresponsive shape memory properties. The shape recovery (88,91 and 95%) and shape retention (70, 75 and 80%) are also found to be different at different temperatures (50, 60 and 70°C respectively). Bisphenol-A-based epoxy resin modified... 

Thermoresponsive shape recovery of epoxy resin-modified vegetable oil-based thermosetting hyperbranched polyurethane. 

Vegetable oil-based hyperbranched polymers have considerable potential in biomedical applications. This is due to their unique structural characteristics along with their biodegradability and biocompatibiUty. Preliminary studies show that vegetable oil-based hyperbranched polyurethanes have the potential to be used as biomaterials in biomedical applications such as drug delivery systems, biomedical smart materials and catheters. ... 

H. Deka and N. Karak, Shape-memory property and characterization of epoxy resin modified Mesua ferrea L. seed oii based hyperbranched polyurethane , J Appl Polym Sci, 2010,116,106-15. 

H. Deka and N. Karak, Bio-based hyperbranched polyurethanes for surface coating applications , Prog Org Coat, 2009, 66,192-8. 

Abstract This chapter describes vegetable oil-based polymer nanocomposites. It deals with the importance, comparison with conventional composites, classification, materials and methods, characterisation, properties and applications of vegetable oil-based polymer nanocomposites. The chapter also includes a short review of polymer nanocomposites of polyester, polyurethanes and epoxies based on different vegetable oils and nanomaterials. The chapter shows that the formation of suitable vegetable oil-based polymer nanocomposite can be considered to be a means of enhancing many of the desirable properties of such polymers or of obtaining materials with an intrinsically new set of properties which will extend their utility in a variety of advanced applications. Vegetable oil-based shape memory hyperbranched polyurethane nanocomposites can be sited as an exampie of such advanced products. 

Information about surface morphology is also obtained from SEM studies. In general, the intercalated clay layers show an intense peak in the range of 1.5° ° (29 value), whereas exfoliated systems have no distinct peak in that range for their loss of structural integrity shown in the XRD pattern of the nanocomposites. XRD studies indicate that there is no infiu-ence of nanomaterial on poly(e-caprolactone)diol PCL crystallinity in sunflower oil-based hyperbranched polyurethane/silver nanocomposite, but that crystallinity is enhanced in castor oil or Mesua ferrea oil-based hyperbranched polyurethane/MWCNT nanocomposites. ... 

Bisphenol-A-based epoxy with a poly(amido amine) hardener system cured Mesuaferrea L. seed oil-based hyperbranched polyurethane (HBPU)/ clay nanocomposites obtained by an ex situ solution technique, was also reported. The partially exfoliated nanocomposites showed a two-fold improvement in adhesive strength and scratch hardness, 10 MPa increments in tensile strength and thermostability at 112°C with little effect on impact resistance, bending and elongation at break compared to a pristine epoxy-modified HBPU system. However, similar epoxy-cured Mesua ferrea L. seed oil-based HBPU/clay nanocomposites exhibited a two-fold increase in tensile strength, a 6°C increase in melting point and thermostability at 111°C after nanocomposite formation using an in situ technique. An excellent shape recovery of about 96-99% was observed for the nanocomposites. The above observations confirm that the performance characteristics of nanocomposites are influenced by their preparation technique. 

Acid modified multi-walled carbon nanotubes and Mesua ferrea L. seed oil-based hyperbranched polyurethane-based nanocomposites have also been reported, exhibiting 300% improvement in tensile strength, enhancement of thermal stability up to 275°C, excellent shape recovery up to 98% (Fig. 11.7), enhanced biodegradabUity and cytocompatibility, confirmed by the inhibition of a RBC haemolysis test at a very low loading of CNT. ... 

Images of different states of shape memory MWNT/ hyperbranched polyurethane nanocomposites. 

N. Karak, R. Konwarh and B. Voit, Catalytically active vegetable-oil based thermoplastic hyperbranched polyurethane/silver nanocomposites , Macromol Mater Eng, 2009, 295,159-69. 

H. Deka and N. Karak, Influence of highly branched poly(amido amine) on the properties of hyperbranched polyurethane/clay nanocomposites . Mater Chem Phys, 2010,124,120-28. 

H. Deka, N. Karak, R. D. Kahta and A. K. Buragohain, Biocompatible hyperbranched polyurethane/multi-waUed carbon nanotube composites as shape memory materials . Carbon, 2010,48, 2013-22. 

H. Deka and N. Karak, Rheological study of vegetable oil based hyperbranched polyurethane/multi-walled carbon nanotube nanocomposites , Polym-Plastics Technol Eng, 2011,50,797-803. 

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