Baths, PMMA

In a number of processes the plastics prior to pyrolysis are dissolved into product oil for example, so that the viscosity is quite controllable. Other options, though today somewhat obsolete, are the use of a molten lead, tin or salt bath. Unfortunately, residues accumulate on top of this bath, and periodic shut-down for cleaning is inevitable. The process has been used commercially for PMMA. 

For the depolymerization of PMMA, molten metal bath, dry distillation, extruder processes and fiuidized-bed processes are used [19], The depolymerization reactor of a molten metal bath consists essentially of a gas- or oil-heated metal bath. The metals used are those which have a low melting point such as tin and lead. The PMMA regrind is fed from the storage silos onto the stirred metal bath. Bath temperature and a residence time of some minutes are important for good yield and quality of the MMA. 

In contrast to this, the residence time of the products in a fluidized bed lies between 1 and 5 s [20]. Buekens [21] studied the influence of the residence times in technical fluidized-bed processes. One of the main advantages in using a fluidized bed reactor for depolymerization is that it involves no contamination of organometallic compounds in the products and less environmental problems [1]. Therefore, companies are looking to use fluidized-bed processes especially for filled PMMA. The filler will contaminate the molten metal bath while in a fluidized bed the often expensive fillers can be recovered. 

Figure 4.19 Products obtained in PMMA pyrolysis at different temperatures in fluidized and molten bath systems.90...

Prepare a solution of III-PMMA (0.0128 mmol), SSNa (1.28 mmol), copper (I) bromide (0.026 mmol) and PMDETA (0.026 mmol) in DMF in a dry flask under argon. The reaction mixture is stirred at 110 °C in an oil bath. Recovery of the product is similar to the method above. 

A form of pyrolysis utilized industrially concerns PMMA (Figure 2.5). PMMA waste, which is generally clean and which does not leave the industrial circuits, is collected and thrown into a bath of molten metal. PMMA decomposes itself by restoring 97.2% of monomers, which can be used for the polymerization of new plates of PMMA. The method works less well if the waste is too dirty. 

Consider the thermoforming of a domestic bath from 5 mm thick PMMA sheet. Why is it preferable to preheat the blanks in an oven rather than apply radiant heating to the sheet when it is over the mould What are the stresses in the sheet when it is cylindrical in shape, radius 0.5 m and thickness 4 mm, when the pressure difference across it is 0.5 bar (50kPa)P What is a typical draw ratio ... 

Chao et al. [12] reported an ultrasound-actuated micropump which uses nonporous one-way membranes. The device consists of a PMMA pumping chamber with nanonozzles and diffusers. If the device is submerged in ultrasonic bath, it starts pumping the fluid. A flow rate of 0.603 pL/s against a back pressure of 200 mm H2O was reported. 

Stereocomplexes were prepared by systematically mixing i- and s-PMMA solutions of equal concentration at room temperature. They were kept in a thermostatically controlled bath at 25°C before the measurements were done. 

The first two of these, PI and SBR, are elastomers. SBR is one of the components used in car tyre treads. The last two are solids at ordinary temperatures. In expanded form, PS is used for thermal insulation panels and food containers, whereas in solid form, it is used for transparent cups and yoghurt pots. PMMA, better known by its commercial name Plexiglas, is used for windows, but also for wash basins, baths and street lights. 

I MM [17]. (a) On a plate a thermostat inset, eight PMMA version of a multicomponent caterpillar fed pumps and four supply vessels are fixed. The micromixer of I MM allowing mixing of up to shown part will be seton/in a thermostat bath, eight different components. Source Institutfur Parts of the feed vessels and also the pump Mikrotechnik Mainz GmbH, heads are inside the thermostated bath, allowing... 

In order to demonstrate the effect of reaction temperature on PMMA pol3nner tacticity, MMA was polymerized at -103 C in an ether-liquid bath. The polymer was 80% syndiotactic however, the polydlspersity was very large as determined by visual inspection of the GPC chromatogram. 

PMMA sheets with an added elastomer component offer optical clarity and are resistant to crazing impacts, ageing and weathering. Acrylic sheets are the top surface layer of baths and other bathroom wares. 

In the preparation of dental base material, poly(methyl methacrylate) (PMMA) is the most commonly used acrylic resin. It is well-mixed with the second component, liquid methyl methacrylate (MMA), prior to use [48]. The prepared in such a way polymer dough is placed in a mould and polymerized in a water bath. The initiator (e.g., benzoyl peroxide) that is usually added to the PMMA powder by a manufacturer decomposed at an elevated temperature and started polymerization and crosslinking. 

The influence of microwave irradiation on the polymerization process of silicone rubber denture soft lining material to PMMA, and its properties were studied by Wright et al. [65]. Three groups of specimens were polymerized under micro-wave irradiation at 650 W for 3, 5, and 10 min in a household microwave oven. The fourth group of specimens was polymerized using conventional thermal methods, i.e., by boiling in a water bath for 2 h. The study demonstrated that mi-... 

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