Melt polymerization study

Thermoplastic Polyurethane Elastomer Melt Polymerization Study... 

The first example of homogeneous transition metal catalysis in an ionic liquid was the platinum-catalyzed hydroformylation of ethene in tetraethylammonium trichlorostannate (mp. 78 °C), described by Parshall in 1972 (Scheme 5.2-1, a)) [1]. In 1987, Knifton reported the ruthenium- and cobalt-catalyzed hydroformylation of internal and terminal alkenes in molten [Bu4P]Br, a salt that falls under the now accepted definition for an ionic liquid (see Scheme 5.2-1, b)) [2]. The first applications of room-temperature ionic liquids in homogeneous transition metal catalysis were described in 1990 by Chauvin et al. and by Wilkes et ak. Wilkes et al. used weekly acidic chloroaluminate melts and studied ethylene polymerization in them with Ziegler-Natta catalysts (Scheme 5.2-1, c)) [3]. Chauvin s group dissolved nickel catalysts in weakly acidic chloroaluminate melts and investigated the resulting ionic catalyst solutions for the dimerization of propene (Scheme 5.2-1, d)) [4]. 

The conventional route to prepare I generally involves a high temperature melt polymerization of hexachlorocyclotriphosphazene, or trimer (IV). Recent studies have demonstrated the effectiveness of various acids and organometalllcs as catalysts for the polymerization of IV (8). Alternate routes for the preparation of chloro-polymer which do not involve the ring opening polymerization of trimer have been reported in the patent literature (9. 10). These routes involve a condensation polymerization process and may prove to be of technological importance for the preparation of low to moderate molecular weight polyphosphazenes. 

Figure 2. GPC studies of melt polymerized poly(dichlorophosphazene). Cumulative C(M) and differential F(log M) MWD of II obtained at 60 and 100 h. Ref. 20.

Brassylic acid for polymerization was recrystallized twice from 50/50 v/v ethanol/water this material had two melting points in the range 111-113.5 C by DSC at a heating rate of 1 C/min. Brassylic acid for melting point studies (see below) was recrystallized twice from toluene (91% overall recovery) or twice from from ethyl acetate (84% overall recovery). 

The HBA/HNA system provides a more suitable system for study, since it is prepared by melt polymerization of the two monomers and is far more stable at elevated temperatures compared to the PHBA/PET. The HBA/HNA copolymers are soluble in pentafluorophenol permitting use of NMR techniques to characterize diad sequences. In Fig. 13b,c the 13CNMR spectrum of the carboxyl carbon region of the HBA/HNA copolyesters of the 73/27 and 48/52 systems is shown [34]. Also shown in Fig. 13a,d are the spectra of 13C enriched HBA and HNA containing copolymers permitting unique identification of the diad sequences. As a result of this technique it was possible to determine the reactivity ratios of the two monomers by analyzing the 50/50 copolymer after polymerization to a molar mass value of 2000 [35]. Examination of the copolymer by 13C NMR showed the same ratio of monomers as in the starting... 

Emulsion systems, while widely used in the polymerization of unsaturated monomers, are used rarely for polycondensation. The emulsion system is one in which two (or more) liquid phases are present, md in which polymerization occurs entirely in the bulk of one of the phases and is almost exclusively kinetically controlled. It thus represents a transition from solution polymerization to interfacial polymerizations. In the case of polycondensation reactions, emulsion polymerization has not been studied in detail. Results thus far indicate that molecular weight and molecular weight distribution are subject to the same statistical considerations as apply to solution and melt polymerizations. 

Three larger lOOg batches of polymers with the composition PHQ, TA, 4,4 -0 = 0.5/0.35/0.15 were prepared for fiber and melt flow studies. The polymerization procedure for these was as follows Temp(°C)/time(min)/pressure (mmHg) = 290/60/760 ... 

To study the effect of TBT on polymerization kinetics, the melt-polymerization of BHQ/MHQ/DPT/DPC (50/50/57.5/42.5) was carried out with TBT in the amount of 1000, 300, 100 and 30 ppm s respectively. Attempts were made to carry these polymerizations under the same reaction conditions, particularly the same distillation time under the same vacuum and the same reaction temperature. However some variations in reaction conditions were still possible due to the equipment limitations. Table IV summarized some representative data in this study. As can be seen, the molecular weight of the product achieved was about the same (2.07 vs 1.81) when the amount of TBT used was 1000 ppm or 300 ppm. However, when the amount of TBT was dropped down to 100 ppm or 30 ppm, the molecular weight of the product (reduced viscosity was 1.11 and 0.87 respectively) achieved was only half of those obtained with a high amount of TBT. 

Poly(ethylene terephthalate) (PET) which is manufactured by a stagewise melt polymerization process consisting of transesterification, prepolymerization and finishing polymerization steps, is one of the fastest growing thermoplastic polyesters used extensively for fibers, films, bottles, injection molded parts and other products [1], Considerable scientific effort has been made to elucidate its properties. Important aspects can be studied using solid-state NMR spectroscopy to determine morphology, orientation and mobility in the bulk material. 

Transesterification reactions between poly(ethylene terephthalate) PET, and acetoxybenzoic acid (ABA) were conducted using the melt polymerization technique to understand the transesterification kinetics of a phase segregated system. The transesterification kinetics of two compositions PET 20 / 80 (ABA) and PETIO / 90 (ABA) have been studied at 260, 275, 290 and 305°C using dibutyl tinoxide (0.1 mole percent) as a catalyst. Homopolymerization of acetoxy benzoic acid was also studied at similar temperatures and catalyst concentration. 

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