Poly , transmission

Poly(vinyl chloride). To be converted into film, poly(viayl chloride) [9002-86-22] (PVC) must be modified with heat stabilizers and plasticizers, which increase costs. Plasticized PVC film is highly transparent and soft, with a very high gas-permeation rate. Water-vapor transmission rate is relatively low. At present, PVC film is produced by blown-film extmsion, although casting and calendering are employed for heavier gauges (see Vinyl POLYAffiRS). 

The specialty class of polyols includes poly(butadiene) and polycarbonate polyols. The poly(butadiene) polyols most commonly used in urethane adhesives have functionalities from 1.8 to 2.3 and contain the three isomers (x, y and z) shown in Table 2. Newer variants of poly(butadiene) polyols include a 90% 1,2 product, as well as hydrogenated versions, which produce a saturated hydrocarbon chain [28]. Poly(butadiene) polyols have an all-hydrocarbon backbone, producing a relatively low surface energy material, outstanding moisture resistance, and low vapor transmission values. Aromatic polycarbonate polyols are solids at room temperature. Aliphatic polycarbonate polyols are viscous liquids and are used to obtain adhesion to polar substrates, yet these polyols have better hydrolysis properties than do most polyesters. 

As an indication of the changes in deformation modes that can be produced in ionomers by increase of ion content, consider poly(styrene-co-sodium methacrylate). In ionomers of low ion content, the only observed deformation mode in strained thin films cast from tetra hydrofuran (THF), a nonpolar solvent, is localized crazing. But for ion contents near to or above the critical value of about 6 mol%, both crazing and shear deformation bands have been observed. This is demonstrated in the transmission electron microscope (TEM) scan of Fig. 3 for an ionomer of 8.2 mol% ion content. Somewhat similar deformation patterns have also been observed in a Na-SPS ionomer having an ion content of 7.5 mol%. Clearly, in both of these ionomers, the presence of a... 

Paine et al. [99] tried different stabilizers [i.e., hydroxy propylcellulose, poly(N-vinylpyrollidone), and poly(acrylic acid)] in the dispersion polymerization of styrene initiated with AIBN in the ethanol medium. The direct observation of the stained thin sections of the particles by transmission electron microscopy showed the existence of stabilizer layer in 10-20 nm thickness on the surface of the polystyrene particles. When the polystyrene latexes were dissolved in dioxane and precipitated with methanol, new latex particles with a similar surface stabilizer morphology were obtained. These results supported the grafting mechanism of stabilization during dispersion polymerization of styrene in polar solvents. 

ABA type poly(hydroxyethyl methacrylate) (HEMA) and PDMS copolymers were synthesized by the coupling reactions of preformed a,co-isocyanate terminated PDMS oligomers and amine-terminated HEMA macromonomers312). Polymerization reactions were conducted in DMF solution at 0 °C. Products were purified by precipitation in diethyl ether to remove unreacted PDMS oligomers. After dissolving in DMF/toluene mixture, copolymers were reprecipitated in methanol/water mixture to remove unreacted HEMA oligomers. Microphase separated structures were observed under transmission electron microscope, using osmium tetroxide stained thin copolymer films. 

FIGURE 2.11 Plot of oxygen transmission rate versus time for brominated poly(isobutylene-co-isoprene) (BIMS) nanocomposite. 

In order to obtain Pt nanoparticles, aqueous solution of 10 M K2PtCl4, which contained 10 M (as monomer unit) of poly-NIPA or poly-NEA, was bubbled with Ar gas and then H2 gas. Then the reaction vessel was sealed tightly and kept in a water bath at a suitable temperature. At given reaction times, the vessels were opened and the samples for transmission electron microscopy (TEM) were prepared by soaking a grid (carbon substrate, Oken) in the colloidal solution and then drying it in the air. The TEM (Hitachi H-8100) was operated at 200 kV. 

Recent developments have allowed atomic force microscopic (AFM) studies to follow the course of spherulite development and the internal lamellar structures as the spherulite evolves [206-209]. The major steps in spherulite formation were followed by AFM for poly(bisphenol) A octane ether [210,211] and more recently, as seen in the example of Figure 12 for a propylene 1-hexene copolymer [212] with 20 mol% comonomer. Accommodation of significant content of 1-hexene in the lattice allows formation and propagation of sheaf-like lamellar structure in this copolymer. The onset of sheave formation is clearly discerned in the micrographs of Figure 12 after crystallization for 10 h. Branching and development of the sheave are shown at later times. The direct observation of sheave and spherulitic formation by AFM supports the major features that have been deduced from transmission electron and optical microscopy. The fibrous internal spherulite structure could be directly observed by AFM. 

Normal transmission IRLD can also be used to characterize polymeric fibers, although scattering can induce sloping baselines. Raman spectroscopy then becomes a convenient alternative. Rutledge et al. have recently probed the orientation in electrospun nanofibers composed of a core of Bombyx mori fibroin and an outer shell of poly (ethylene oxide) [24], The orientation values were low, less than 0.1, as is often the case in electrospun fibers. 

Coleman and Sivy also used an infrared transmission cell to undertake degradation studies under reduced pressure on a series of poly(acrylonitrile) (ACN) copolymers [30-33]. Thin films prepared from a polymer were mounted in the specially designed temperature-controlled cell mounted within the infrared spectrometer. The comparative studies were made on ACN copolymers containing vinyl acetate [30,32], methacrylic acid [30,31] and acrylamide [30,33]. The species monitored was the production of the cyclised pyridone structure. This was characterised in part by loss of C=N stretch (vC = N) intensity at 2,240 cm-1 accompanied by the appearance and increase in intensity of a doublet at 1,610/1,580 cm-1. 

Compression molded (150°C for 3 minutes press chilled with cold water immediately thereafter) samples of poly(trans-l,4-hexadiene) (14) and poly(5-methyl-l,4-hexadiene) were examined with a General Electric (XRD-3) X-ray unit. Transmission Laue X-ray photographs were taken using nickel filtered copper X-radiation. Samples were stretched to four times of their original lengths to obtain oriented fibers. The fiber patterns were obtained in a flat plate film holder with the specimen to film distance standardized at 5 centimeters. X-ray diffraction patterns were similarly obtained for the hydrogenated sample of poly(5-methyl-l,4-hexadiene). 

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