Hydroxy-terminated phases

Composite proplnts, which are used almost entirely in rocket propulsion, normally contain a solid phase oxidizer combined with a polymeric fuel binder with a -CH2—CH2— structure. Practically speaking AP is the only oxidizer which has achieved high volume production, although ammonium nitrate (AN) has limited special uses such as in gas generators. Other oxidizers which have been studied more or less as curiosities include hydrazinium nitrate, nitronium perchlorate, lithium perchlorate, lithium nitrate, potassium perchlorate and others. Among binders, the most used are polyurethanes, polybutadiene/acrylonitrile/acrylic acid terpolymers and hydroxy-terminated polybutadienes... 

Composite rocket propellants are two-phase mixtures comprising a crystalline oxidizer in a polymeric fuel/binder matrix. The oxidizer is a finely-dispersed powder of ammonium perchlorate which is suspended in a fuel. The fuel is a plasticized polymeric material which may have rubbery properties (i.e. hydroxy-terminated polybutadiene crosslinked with a diisocyanate) or plastic properties (i.e. polycaprolactone). Composite rocket propellants can be either extruded or cast depending on the type of fuel employed. For composite propellants which are plastic in nature, the technique of extrusion is employed, whereas for composite propellants which are rubbery, cast or extruded techniques are used. 

Composite rocket propeiiants. This type of propellant contains two-phase mixtures with a aystalhne oxidizer in a polymeric fuel or binder matrix. The finely dispersed powder of ammonium perchlorate suspended in a fuel is the oxidizer. The fuel is a plasticized polymeric material such as hydroxy-terminated polybutadiene cross-linked with a diisocyanate (rubber ts e) or carboxy-terminated polybutadiene (plastic type) [4]. 

Recently, interest in polymer-coated silica phases has been renewed, with investigators (Chen and Lee [2]) exploring the use of more efficient deactivation techniques and more polar polymers to coat silica particles for neat CO2 chromatography. Polyethyl-eneimine-coated silica and amino-terminated polyethylene oxide-coated silica appear promising for pSFC of moderately polar basic compounds. Similarly, hydroxy-terminated polyethylene-oxide-coated silica has been used successfully for pSFC of alcohols and acids. Optimization and commercial production of these stationary phases could significantly extend the polarity range of compounds that can be chromatographed with neat supercritical CO2. 

Fig. 6. Separation of hydroxy-terminated poly(butylene glycol terephthalate) as a function of the mobile phase composition stationary phase silica gel mobile phase THF-heptane peaks 1.2 solvent, peaks 3-7 nonfunctional homologues (n = 0-4), peaks 8-12 monofunctional homologues (n = 0-4), peaks 13-17 bifunctional homologues (n = 04). (From [2] with permission)...

Two-dimensional GC was employed for the analysis of chiral PCBs in foods such as milk, cheese, and salmon. A new (3-CD derivative (permethylated-(3-CD/hydroxy-termination silicone oil) was employed for the efficient extraction of polybrominated diphenyl ethers in soil. CDs have also been used for the analysis of toxaphene congeners. It was established that permethylated and rert-butyldimethylsilylated-(3-CDs separate different congeners and can be applied for the smdy of the degradation of toxaphens. Another smdy applied two-dimensional GC for the successful separation of toxaphene enantiomers. It was found that the separation efficacy of (3-CD containing columns showed marked differences, depending on the composition of the stationary phase. Capillary columns coated with heptakis-(2,3,6-D-tert-butyldimethylsilyl)-(3-CD or octakis-(quest 2,3,6-tri-D-ethyl)-7-CD were employed for the enantiomer-selective decomposition of toxaphene congeners in rats after intravenous administration. The... 

Fig. 28 Topographical (left, z range 150 nm) and frictional force (right, z range 0.2 V) images of a PS/PMMA blend using unfunctionalized (a) and hydroxy-terminated (b) tips. The continuous phase consists of PMMA. (Reprinted with permission from [188]. Copyright 2000 American Chemical Society)...

Poly(ester-co-ether)s have been prepared by using polyether with hydroxy-terminal as eo-initiator in the ring opening polymerizations of cyclic esters. Among these lactide received the most attention [34—41]. Typically lactide, poly(ethylene glycol) and stannous 2-ethyl hexanoate were heated under nitrogen at 120-150 °C for up to 24 hr. The poly(ester-ether)s thus obtained typically show only one, indicating only one amorphous phase. Only crystalline phase for PLLA is observed with low Mw PEG and both crystalline phases for PEG and PLLA are observed when PEG block size approaches 4000 [41]. 

High molar mass block copolymers were synthesized by the reaction of mixtures of hydroxy-terminated poly(oxytetra-methylene) and poly(s-caprolactone) with the same bisoxazolinones. Differential scanning calorimetry (DSC) study of the block copolymers revealed phase separation between the two blocks when the starting polymers have Mn of 1000 Da or higher. Lower molar masses of the starting polymers yielded amorphous products. 

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