Vapor-phase plasticizers

The analysis of plasticizers in indoor air is most fiequently done using either adsorbent tubes (without a front filter) or sample trains. Sample trains corrsist of a filter followed by an adsorbent. They are interrded to separate particles botmd fiom gaseotrs plasticizers. Filters are made either of qirartz or glass fiber. Adsorberrts to trap the vapor phase plasticizers may be XAD CIS extraction disks, polyrrrethane foarrr, - or charcoal." " ... 

One of the most important properties of a plasticizer in the natural environment is its solubility in water. The greater the compound s aqueous solubility, the more likely that a plasticizer will dissolve into water, and become part of the hydrologic cycle. Water solubility can affect the extent of leaching of plastic products, and the movement and chemical fate of dissolved plasticizers in rivers, lakes, and groundwater, and in drinking water supplies. Aqueous solubility also determines the potential for removing vapor-phase plasticizers from the atmosphere through precipitation. 

Alkyl diphenyl phosphate plasticizers can exert flame-retardant action in vinyl plastics by a condensed-phase mechanism, which is probably some sort of phosphoms acid coating on the char. Triaryl phosphates appear to have a vapor-phase action (29). 

Xylenes. The main appHcation of xylene isomers, primarily p- and 0-xylenes, is in the manufacture of plasticizers and polyester fibers and resins. Demands for xylene isomers and other aromatics such as benzene have steadily been increasing over the last two decades. The major source of xylenes is the catalytic reforming of naphtha and the pyrolysis of naphtha and gas oils. A significant amount of toluene and Cg aromatics, which have lower petrochemical value, is also produced by these processes. More valuable p- or 0-xylene isomers can be manufactured from these low value aromatics in a process complex consisting of transalkylation, eg, the Tatoray process and Mobil s toluene disproportionation (M lDP) and selective toluene disproportionation (MSTDP) processes isomerization, eg, the UOP Isomar process (88) and Mobil s high temperature isomerization (MHTI), low pressure isomerization (MLPI), and vapor-phase isomerization (MVPI) processes (89) and xylene isomer separation, eg, the UOP Parex process (90). 

Ethyl Vinyl Ether. The addition of ethanol to acetylene gives ethyl vinyl ether [104-92-2] (351—355). The vapor-phase reaction is generally mn at 1.38—2.07 MPa (13.6—20.4 atm) and temperatures of 160—180°C with alkaline catalysts such as potassium hydroxide and potassium ethoxide. High molecular weight polymers of ethyl vinyl ether are used for pressure-sensitive adhesives, viscosity-index improvers, coatings and films lower molecular weight polymers are plasticizers and resin modifiers. 

Sublimation (diffusion) printing is a textile process in which color patterns in dry die crystals are transferred from a release film to the fabric under high heat and pressure. The process has been adapted to plastics. The equipment used is very similar to that used for hot stamping. Under heat and pressure, the dye crystals sublime (go directly to the vapor phase from the solid phase without melting) and the vapor penetrates the plastic product. As a result, the decoration is very durable and wear resistant. It is also cost competitive against other processes such as two-step injection molding or silk screening. 

Figure 7. Vapor-Uquid-soUds (plastic crystal 2, plastic crystal 2, crystal 3) phase diagram of diamantane. This diagram is based on the data of Table II. The shaded area between vapor and plastic crystal 2 and crystal 3 phase transitions is indicative of the error range of the available data.

As suggested by such experiments on model flames, it appears possible that vapor phase flame retardants better by one or two orders of magnitude than the best present systems may be found for use in plastics. 

Aniline is an aromatic amine used in the manufacture of dyes, dye intermediates, rubber accelerators, and antioxidants. It has also been used as a solvent, in printing inks, and as an intermediate in the manufacture of pharmaceuticals, photographic developers, plastics, isocyanates, hydroquinones, herbicides, fungicides, and ion-exchange resins. It is produced commercially by catalytic vapor phase hydrogenation of nitrobenzene (Benya and Cornish 1994 HSDB 1996). Production of aniline oil was listed at approximately 1 billion pounds in 1993 (U.S. ITC 1994). Chemical and physical properties are listed in Table 1-2. 

Store the tissue on the chuck if sections are to be cut in the immediate future if not, wrap the tissue in aluminum foil, and place it in a small sealable plastic bag. Store at -70°C or in the vapor phase of a liquid nitrogen freezer (see Note 6). 

Collection. Procedures commonly used to collect vapor-phase organic compounds include whole-air, cryogenic, adsorption, absorption, and de-rivatization methods. Whole-air sampling involves the capture of an air parcel in a container. Stainless steel canisters or plastic bags constructed from an inert material, such as Teflon or Tedlar, are most commonly used. Each of... 

Diffusion of Heat. In dynamic equilibrium, a transfer of vapor from liquid through a vapor phase to a second liquid (the two liquids being thermally connected only across the thin gap) will require reverse transfer of the heat of vaporization. This will accompany a temperature difference determined by the ratio of heat flow to the thermal conductance of the two heat paths. These two are the diffusion vapor gap and the series of salt water and plastic films. For the diffusion gap the c.g.s. air value 5.7 x 1(H is chosen for the thermal conductivity (neglecting the separating powder), while for the series polyethylene (50 X 10-4 cm. thick), wet cellophane (50 X 10"4 cm. thick), and water (200 X 10-4 cm. thick) the respective thermal conductivities are 3.5 X 10"4, 4 X 10-4, and 14 X 10 4. 

As has been previously reported, when pyrene is adsorbed on silica gel there is evidence for ground state association which is not present In solution or the vapor phase.9-13 but which has been described as being present when pyrene is dissolved in a plastic medium. This is also a manifestation of surface inhomogeneity -some sites enhance the tendency to form a ground state bimolecular complex, whereas other sites contain isolated pyrene molecules. The interaction differences are sufficient to yield significant spectral shifts in absorption and the ground state complex emits with the characteristic pyrene excimer fluorescence. Fig. 5 shows a typical set of spectra Illustrating this association and Fig. 6 presents evidence that this observation Is not due to microcrystal formation. 

For vapor phase measurement of dry oil oxidation, the plate assembly shown in Figure 5 is used. The lower glass or terephtha-late plastic plate holds a disk of polyamide (1.2 x 0.1 cm) on which 1 pi of a suitable oil (linoleic acid, methyl linoleate, cottonseed oil) is deposited from a micropipette. A Buna "0" ring of 1.5-mm thickness is placed surrounding the spot and a similar plate with a polyamide disk is inverted over the ring forming a tight seal when clamped with "C" clamps. The plate assembly is placed in a 65°C draft oven with the receiver plate bottommost. 

Langwell Vapor Phase Deacidification Process. Langwell s VPD process is a very simple process. Cyclohexylamine carbonate is inserted between book pages to achieve partial deacidification. However, this process does not create an alkaline reserve in treated products to prevent future acid attack. Cyclohexylamine carbonate will react with some plastic covers, inks and colors. Preselection of books is required. The odor and the carcinogenic nature of the vapor are also critical factors that limit the use of VPD process as a mass deacidification process (46-54). 

Bulk Vapor-Phase Samples. Flexible plastic sample bags are generally limited to... 

Flame-retardant styrenic polymers find utility in applications such as building insulation (expanded polystyrene foam) and electronic enclosures (flame-retardant HIPS, ABS and styrenic blends). The most effective flame retardants are halogen-(particularly bromine)-containing compounds these flame retardants act by inhibiting the radical combustion reactions occurring in the vapor phase. Flame-retardant plastics are in a state of flux, due to influences of... 

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