PTMSP

Notes Cellulose (Whatman) PTMSP, poly(trimethyl silyl propine) PS, polystyrene PP, polypropylene PE, polyethylene PA 66, polyamide 66 PA 6, polyamide 6 PVP, poly(vinyl pyrrolidone) PPO, poly(2,6-dimetyl-l,4-phenylene oxide) PMMA, poly(methyl methacrylate) PETP, polyethylene terephthalate) Irganox 1010 is a Ciba anti-oxidant. 

Figure 2.23 Structure of two high-free-volume substituted polyacetylenes, PTMSP and PMP. The carbon-carbon double bond is completely rigid, and depending on the size of the substituents, rotation around the carbon-carbon single bond can be very restricted also. The result is very stiff-backboned, rigid polymer chains which pack very poorly, leading to unusually high fractional free volumes...

These high-free-volume polymers also have unusual permeability characteristics with mixtures of condensable and noncondensable gases. For example, in the presence of as little as 1200 ppm of a condensable vapor such as the per-fluorocarbon FC-77 (a perfluoro octane-perfluoro decane mixture), the nitrogen permeability of PTMSP is 20 times lower than the pure nitrogen permeability [71], as shown in Figure 2.41. When the condensable vapor is removed from the feed gas the nitrogen permeability rapidly returns to its original value. The best... 

Figure 2.41 The change in nitrogen flux through a PTMSP membrane caused by the presence of a condensable vapor in the feed gas [71]. This behavior is characteristic of extremely finely porous microporous ceramic or ultrahigh-free-volume polymeric membranes such as PTMSP. The condensable vapor adsorbs in the 5- to 15-A-diameter pores of the membrane, blocking the flow of the noncondensable nitrogen gas...

A. Morisato, B.D. Freeman, I. Pinnau and C.G. Casillas, Pure Hydrocarbon Sorption Properties of Poly(l-trimethylsilyl-l-propyne) [PTMSP] and Poly(l-phenyl-l-propyne) [PPP] and PTMSP/PPP Blends, J. Polym. Sci., Polym. Phys. Ed. 34, 1925 (1996). 

Table 1.1 contains typical solubility prediction data for an ultrahigh free-volume polymer (PTMSP) and a polymer with more conventional transport properties (PTMSS). 

Table 1.1 Results of application of the Cusev-Suter method to the solubility of N2 in PTMSP and PTMSS.

In contrast, organophilic PV membranes are used for removal of (volatile) organic compounds from aqueous solutions. They are typically made of rubbery polymers (elastomers). Cross-linked silicone rubber (PDMS) is the state-of-the-art for the selective barrier [1, 43, 44]. Nevertheless, glassy polymers (e.g., substituted polyacetylene or poly(l-(trimethylsilyl)-l-propyne, PTMSP) were also observed to be preferentially permeable for organics from water. Polyether-polyamide block-copolymers, combining permeable hydrophilic and stabilizing hydrophobic domains within one material, are also successfully used as a selective barrier. 

The results given in Table 5-1 show that the agreement between the diffusion coefficients predicted from MD simulations and experimental ones ranges from reasonable to excellent. At temperatures around 300 K this is found both for polymers which are above their glass transition temperature, Tg, (PDMS, PIB, PE and aPP) and for polymers which are below Tg (PET, PS, PTMSP, PI and PAI). As a trend one can notice, and this not only from Tab. 5-1 but also from other works published in the last six or seven years, that the agreement between MD simulations of diffusion and solvation of small penetrants in polymers and experiment steadily improved. These are encouraging developments, showing that modern softwares (some of them available for... 

The diffusion of gases through a polymer matrix is determined by the mobility of gas molecules through the matrix. The diffusion coefficient is therefore, at least partially determined by the free volume size of the polymer. It has been shown, for example, that there is a correlation between the free volume measured by PAL and the diffusivity of carbon dioxide in a seriers of polycarbonates [58], In a study of poly (trimethylsilyl propyne) (PTMSP), which has an extremely high gas permeability and diffusion coefficients, it was found that the lifetime data could be resolved into four components [59]. The longest lifetime component (T4) had a lifetime of... 

The SSF membranes, which are produced by carbonization of PVDC, contain nanopores that allow all of the molecules of a feed gas mixture to enter the pore structure. However, the larger and more polar molecules are selectively adsorbed on the carbon pore walls at the high pressure side, and then th dif se selectively to the low pressure side. The smaller molecules are enriched at the high pressure side. These membranes can be used to enrich H2 from mixtures with C1-C4 hydrocarbons or from mixtures with CO2 and CH4. They can also be used to separate CH4-H2S and H2S-H2 mixtures. Table 5 compares performances of SSF carbon and polymeric PTMSP membranes for H2 enrichment from FCC off gas [15]. Clearly, the SSF membrane is much superior for this application. 

Unfortunately there is an aging problem for PTMSP, resulting in deterioration of its transport properties with time. As shown in Figure 9.16, permeability decreased by one order of magnimde during the first 3 months, whereupon permeability stabilized. Selectivity remained stable during this period. But even the aged PTMSP is still a viable alternative to mbbery polymers for heavy hydrocarbon removal. 

FIGURE 9.16 Aging effects of PTMSP during storage at ambient conditions o butane flux and selectivity (measurements were made at 10 atm, 35°C, for methane/butane mixture with 3% butane composite membrane had the selective layers 3-5 xm). (From Schultz, J. and Peinemann, K.V., J. Membr. Sci., 110, 37, 1996. With permission.)... 

AA acrylic acid LDPE low density polyethylene NBR poly (butadiene-acrylonitrile) PA polyamide PAA poly(acrylic acid) PAN polyacrylonitrile PB polybutadiene PC polycarbonate PDMS polydimetylsiloxane PE polyester PEBA polyetheramide-block-polymer PI polyimide PMA poly(methyl acrylate) POUA poly(oxyethylene urethane acrylate) PP polypropylene PPO poly(phenylene oxide) PTMSP poly(trimethylsilylpropyne) PUR polyurethane PVA poly(vinyl alcohol) PVC poly(vinyl chloride). 

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