Styrene, sampling

Another example of multi-column analysis has been demonstrated for the determination of impurities in styrene. The marked compounds in the styrene sample (Figure 12.15(a)) were solvent flushed via a splitline, with the analysis being carried out with a cryotrapping separation (CTS) (see Figure 12.15(b)). The first column, was an Ultra-2 (25 m X 0.32 mm i.d., d( = 0.25 p.m) precolumn, while the main column was a DB-WAX (30 m X 0.32 mm, d = 0.25 p.m) with an FID being employed as the detection system. 

Chlorinated poly(styrene) samples were prepared by chlorination of PS with CI2 in trifluoroacetic acid(9) or by free radical chlorination using f-butyl hypochlorite(lO) or by chloromethylation using chloromethyl actyl ether and SnCU(ll). 

Run the poly(styrene) sample on the instrument according to a linear programmed temperature ramp (usually 5, 10, or 20°C/min) to a final temperature greater than 600°C (see Fig. 15.6). 

Fig. 8.14 PS-styrene sample extruded at 180°C into atmospheric pressure. The micrograph shows the smooth lateral surface and part of the cross section there is no evidence of huhhles. [Reprinted by permission from R. J. Albalak, Z. Tadmor, and Y. Talmon, Scanning Electron Microscopy Studies of Polymer Melt Devolatilization, AIChE J., 33, 808-818 (1987).]...

NMR Measurements. In all cases, ten percent solutions of thepoly-styrene samples dissolved in a 9 1 1,2,4-trichlorobenzenetnitro-benzene-ds mixture were used for the NMR studies. 75 MHz 13C-NMR 1H-decoupled spectra of the epimerized polystyrene samples were recorded at 150-160° using a Bruker WH-300 NMR Spectrometer. A 70° pulse width, an acquisition time of 0.82 seconds with a 16K data size, and a pulse delay of 0.1 second were employed. The number of transients collected varied from 3000 to 10,000 and the data were processed with a line broadening of 0.8-1.0 Hz. A Tx study done on the aromatic C-l and aliphatic carbon resonances of polystyrene at 200°C, using a Varian XL-400 NMR Spectrometer, revealed that within experimental error the individual components of these resonance patterns had the same relaxation time(35). This indicates that the conditions described above are appropriate for obtaining resonance patterns that could be analyzed quantitatively. 

Fig. 5.7. The osmotic pressure H of a poly(a-methyl)styrene sample in toluene at 25 C as a function of ps. Here g is the gravity intensity. The measured values are represented by small circles. The curve is obtained in the interval 0-15 g/e by interpolation (polynomial of degree 3).

Fig. IS. Infra-red (IR) spectra of (A), beaded copoly AOTcp-styrene) (sample 8f in Table 6) B), 8f after partial aminolysis by iV-(6-aminohexyl)tert.-butyi carbamate (see entry 1 in Table 7) (C), after complete aminolysis of above by dimethylamine and (O), after removal of the tert-butylcarbonyl group...

Cyclohexane solutions of a poly(a-methyl styrene) sample prepared by anionic polymerization were examined by light scattering in the temperature range 300 to 320 K(Cowieetal., 1967). Scattered intensity measured at 6 = 90° are listed in the following table as a function of concentration and temperature. 

Poly(styrene) samples were exposed to a constant flow of ozone (ozone generator BMT 802N operated at 100% power) at room temperature for 15 min. Thereafter, the samples were annealed for 24h at 60 °C in air. 

Raeder et al. analyzed the MALDl-TOF mass spectrum of a sulfonated styrene sample containing units of styrene (A) and styrene-sulfonic acid (B). They measured the intensity of the MS peaks, inserted the intensity values in Eq. 2.20 and foxmd that Ca = 0.06, which implies that the average degree of sulfonation is 94%. 

Molecular weight distributions (SEC curves) of poiy-styrene samples with identicai peak moiecuiar weights generated via CDB-mediated styrene buik polymerization at 70 °C at 1 and 2000 bar, respect-iveiy, with aii other parameters being kept constant. ... 

Fig. 4.4. Reduced viscosity as a function of the concentration c for poly(styrene) samples of a broad range of molar masses in toluene at 7=25 C and in tetrahydrofuran (THF) at 7=30 C.The intrinsic viscosities range from [/j]=5-2300 ml g for the toluene solution and from [ri]=23-40S ml g" for the THF solution. Data for PS in THF as a courtesy from PSS Polymer Standards Service, Mainz, Germany, PS in toluene from [88]...

In a first set of measurements poly(styrene) samples differing in chain length were mixed with their brominated derivatives and the authors determined the maximum tolerable bromine content. A, for a 50/50 (w/w) blend to remain homogeneous, i.e., transparent. A was found to increase with decreasing chain length of the original poly (styrene). A second set concerned 50/50 mixtures of substituted Dolvfstvrenes) of different bromine content. Kambour et al. found that the maximum... 

The validity of this concept is dannonstrated by the opticcd. photomicrographs (fig.4) of films casted fran 8( VC/2C >St solution mixtures containing respectively 0, 5 and 10 % of a 56/50 poly-(caprolactone-b-styrene) sample (B3). 

Experimental variables (sampling volume, desorption time, desorption temperature and headspace pressure) were mathematically modelled and quantitatively assessed with a view to optimisation. Van Eldik et al. [985] applied solid polymer PT analysis for the screening of the outgassing behaviour of 61 styrenic samples (ABS, HIPS, PPO/PS), containing a variety of BFRs (such as DBBP, DBDPO, OBB, TBBP-A, TBPE, etc.), taken from used TV sets, computer housings and printers, and 13 polyamides (PA6, PA6.6) for electrotechnical applications in relation to health and safety for the user. The analytes were collected on a Tenax tube, cryofocused and analysed by means of TD-GC-MS. 

Using the conditions given in Table 7.14 chromatograph 5 micro litres of the styrene sample at a range of x 10 and an attenuation appropriate to the concentration of impurities present. Prepare an accurate 1% w/w solution of n-undecane internal standard in the styrene sample. Chromatograph 5 microlitres of this solution attenuating the peaks as necessary. Measure the peak areas of die internal standard and of the components to be determined. 

Into a 100 cm stoppered volumetric flask, weigh 10 ml of styrene sample and exactly 1 ml of a 0.5% v/v solution of n-hexadecane internal standard in jM opylene oxide. Chromatograph 2 ul of this solution on a Carbowax Celite column at a range of x 10 and suitable attenuations using the conditions indicated in Table 7.14 with the exception that the injection and column temperatures are set at 150 C and 140°C respectively. 

Fig. 16. Experimental b (x) curves for a mixture of two narrow-distribution poly styrene samples. Initial concentration 1% by wdgbt solvent C3rdohmcan...

In the case of composites, such as that of P(ANi) with poly (styrene), increase of pressure on a 40% poly(styrene) sample from ambient to 10 kbar causes a conductivity increase from 10 S/cm to 1 S/cm. 

The crystallization of an isotactic poly(styrene) sample that was originally freeze dried from a 0.01 wt percent benzene solution vividly demonstrates the influence of chain entanglements on the kinetics.(50d) Such a sample has a minimal amount of entanglements since it essentially comes from a dilute solution. Consequently it was found that freeze dried samples crystallized, in terms of half-times, approximately nine times faster than the untreated polymer. Both samples crystallized from the pure melt in the conventional manner. This result is consistent with the Rory-Yoon calculations that the chains cannot disentangle each other from the melt during the time scale of the crystallization.(50e,50f) This calculation is consistent with the... 

Further evidence for the influence of chain entanglement in the crystallization process is found in the crystallization of an isotactic poly(styrene) sample that was prepared from a freeze-dried dilute benzene solution.(38a) Entanglements in such a sample will be miiumal. The overall crystallization rate in such samples, in terms of ii/2, is enhanced by a factor of seven to eight relative to conventional crystallization from the pure melt.(38a) Experiments with isotactic poly(propylene), freeze-dried from n-octane, showed a similar enhancement in the crystallization rate.(38b) This type of experiment complements the overall crystallization rate of polymers from dilute solution. 

Figure 16 shows, with the extensive data of Noda et al. for poly(a-methyl styrene) samples in toluene at 25 °C, that liMjcRT is scaled by cjc (see eqn [39] for the overlap concentration c ). The indicated straight line has a slope of 1.3. Essentially, the same scaling behavior of OM/cRT was found by Schafer with earlier data for other polymers and also by Noda et alF for PS, all in good solvents. 

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