Incorporation into polyurethanes

This phosphoms-rich oligomer can also be incorporated into polyurethanes. Combinations with Eyrol 6 permit the OH number to be adjusted to typical values used in flexible foam, urethane coating, or reaction injection mol ding (RIM) appHcations (115,116). 

When a polymer system is intended to extract polar compounds, however, we deviate from conventional polyurethane research and focus on the chemistry of the material. In this area, standard texts on polyurethanes are of little value. The chemistry is extensive enough to require the rest of this book to describe. In keeping with the structure of this book, however, our discussion of achieving a desired chemistry will occupy only a few pages. Our intent is to show how chemically active aspects of a polyurethane are incorporated into a polymer. For the most part, these chemistries are hydrophilic. This reflects the work in our lab more than predetermined restrictions of the technology. We will illustrate why the tools discussed in this chapter are valuable. We will also discuss three categories of chemical modifications and how they are incorporated into polyurethane foam. The modifications are ... 

In protective clothing, a layer of polyurethane, foam-entrapped, activated charcoal is embedded between several layers of polyester fabric. Polyurethanes are effective substrates for OP adsorption, and reports have documented that polyurethane foam particles can be used as adsorbent materials for pesticide vapors in farming fields. If proteins could be incorporated into polyurethanes, some interesting materials might emerge. 

Flame retardants (qv) are incorporated into the formulations in amounts necessary to satisfy existing requirements. Reactive-type diols, such as A/ A/-bis(2-hydroxyethyl)aminomethylphosphonate (Fyrol 6), are preferred, but nonreactive phosphates (Fyrol CEF, Fyrol PCF) are also used. Often, the necessary results are achieved using mineral fillers, such as alumina trihydrate or melamine. Melamine melts away from the flame and forms both a nonflammable gaseous environment and a molten barrier that helps to isolate the combustible polyurethane foam from the flame. Alumina trihydrate releases water of hydration to cool the flame, forming a noncombustible inorganic protective char at the flame front. Flame-resistant upholstery fabric or liners are also used (27). 

To achieve low stress embedding material, low modulus material such as siUcones (elastomers or gels) and polyurethanes are usually used. Soft-domain elastomeric particles are usually incorporated into the hard (high modulus) materials such as epoxies and polyimides to reduce the stress of embedding materials. With the addition of the perfect particle size, distribution, and loading of soft domain particles, low stress epoxy mol ding compounds have been developed as excellent embedding materials for electronic appHcations. 

The minimum service temperature is determined primarily by the Tg of the soft phase component. Thus the SBS materials ctm be used down towards the Tg of the polybutadiene phase, approaching -100°C. Where polyethers have been used as the soft phase in polyurethane, polyamide or polyester, the soft phase Tg is about -60°C, whilst the polyester polyurethanes will typically be limited to a minimum temperature of about 0°C. The thermoplastic polyolefin rubbers, using ethylene-propylene materials for the soft phase, have similar minimum temperatures to the polyether-based polymers. Such minimum temperatures can also be affected by the presence of plasticisers, including mineral oils, and by resins if these become incorporated into the soft phase. It should, perhaps, be added that if the polymer component of the soft phase was crystallisable, then the higher would also affect the minimum service temperature, this depending on the level of crystallinity. 

Condensation polymers, which are also known as step growth polymers, are historically the oldest class of common synthetic polymers. Although superseded in terms of gross output by addition polymers, condensation polymers are still commonly used in a wide variety of applications examples include polyamides (nylons), polycarbonates, polyurethanes, and epoxy adhesives. Figure 1.9 outlines the basic reaction scheme for condensation polymerization. One or more different monomers can be incorporated into a condensation polymer. 

Another widespread use of polyurethane elastic fibers is in disposable diapers and adult incontinence garments. Elastic strands are incorporated into waistbands and side panels made of non-woven fabrics where they improve fit and reduce leakage. 

Much work has been done on the incorporation of castor oil into polyurethane formulations, including flexible foams [64], rigid foams [65], and elastomers [66]. Castor oil derivatives have also been investigated, by the isolation of methyl ricinoleate from castor oil, in a fashion similar to that used for the preparation of biodiesel. The methyl ricinoleate is then transesterified to a synthetic triol, and the chain simultaneously extended by homo-polymerization to provide polyols of 1,000, 000 molecular weight. Polyurethane elastomers were then prepared by reaction with MDl. It was determined that lower hardness and tensile/elongation properties could be related to the formation of cyclization products that are common to polyester polyols, or could be due to monomer dehydration, which is a known side reaction of ricinoleic acid [67]. Both side reactions limit the growth of polyol molecular weight. 

In this regard, polyurethane technology offers a product designer a particular advantage. An aqueous solution or dispersion can be emulsified conveniently with a hydrophilic prepolymer and thus incorporated into the polyurethane matrix. The incorporation is accomplished by covalently bonding within the polyurethane backbone and by entrapping it within the matrix. Both methods are evident in foams produced by this technique. 

Interest in the photoconductive properties of the carbazole nucleus has also prompted studies concerned with its incorporation into condensation polymers. Examples of polymers prepared include polyamides (34), polyesters (35) and polyurethanes (36) (80MI11105). Thorough studies on the CT interactions of these polymers with the monomeric acceptor 2,4,7-trinitrofluorenone have been done. In all cases, the formation constant for the CT complex was higher with polymers than for monomeric models. At least two polymer... 

Some polymers show discoloration as well as reduction of the mechanical properties (e.g. aromatic polyesters, aromatic polyamides, polycarbonate, polyurethanes, poly (phenylene oxide, polysulphone), others show only a deterioration of the mechanical properties (polypropylene, cotton) or mainly yellowing (wool, poly(vinyl chloride)). This degradation may be less pronounced when an ultraviolet absorber is incorporated into the polymer. The role of the UV-absorbers (usually o-hydroxybenzophenones or o-hydroxyphenylbenzotriazoles) is to absorb the radiation in the 300-400 nm region and dissipate the energy in a manner harmless to the material to be protected. UV-protection of polymers can be well achieved by the use of additives (e.g. nickel chelates) that, by a transfer of excitation energy, are capable of quenching electronically excited states of impurities (e.g. carbonyl groups) present in the polymer (e.g. polypropylene). 

In manufacturing explosive charges which are required to have a certain mechanical strength or rubber-elastic toughness, Cyclonite is incorporated into curable plastic materials such as polyurethanes, polybutadiene or polysulfide and is poured into molds (-> Plastic Explosives). 

Brominated flame retardants (BFRs) are an interesting and important group of chemicals that are widely incorporated into plastics, foams, electrical items and furnishings to reduce the risk of Are. Indeed, it is likely that the polyurethane foam used in an upholstered chair in which you maybe sitting, will have been treated with a BFR in order to conform to fire-safety standards. However, their widespread use, release... 

S. S. Kelley, Incorporation of lignin copolymers into polyurethane materials, Ph.D. thesis, Virginia Polytech. Inst. State Univ., 1987, Univ. Microfilms Int., DA8814587. 

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