Heat examples

In practice, synthetic polymers are sometimes divided into two classes, thermosetting and thermo-plMtic. Those polymers which in their original condition will fiow and can be moulded by heat and pressime, but which in their finished or cured state cannot be re softened or moulded are known as thermo setting (examples phenol formaldehyde or urea formaldehyde polymer). Thermoplastic polymers can be resoftened and remoulded by heat (examples ethylene polymers and polymers of acrylic esters). 

Calculate the change in internal energy when an ideal gas is heated (Example 6.6). 

When the phosphazene produced by the decomposition of an azide contains an A -phosphoryl group with an alkoxy-substituent, isomerization may occur on heating. Examples of such phosphazenes were produced... 

Many other mechanisms lead to energy dissipation, although they may be less universal than those related to boundary lubricant-induced geometric frustration. Chemical changes in lubricant molecules, reversible or irreversible, produce heat. Examples are configurational changes in hydrogen-terminated... 

Use a heat carrier to remove heat (example excess inert). 

Analytical instmments have been developed recently to dry ash samples using thermal and microwave heating examples are the APION A dry mode mineralizer (Tessek, Czech Republic), MLS-1200 PYRO microwave ashing furnace (Milestone, USA), and MAS 7000 microwave ashing system (CEM, USA). 

Some ionic solids dissolve with the release of heat. Examples are anhydrous sodium sulfate, Na2S04 calcium acetate, Ca(CH3COO)2 calcium chloride, CaCl2 and lithium sulfate hydrate, Li2S04 H20. 

Use a direct heat carrier to supply heat (example steam). 

Microwave processing of zeolites and their application in the catalysis of synthetic organic reactions has recently been excellently reviewed by Cundy [25] and other authors [26], The microwave synthesis of zeolites and mesoporous materials was surveyed, with emphasis on those aspects which differ from conventional thermal methods. The observed rate enhancement of microwave-mediated organic synthesis achieved by use of these catalysts was caused by a variety of thermal effects, including very high rates of temperature increase, bulk superheating, and differential heating. Examples of microwave activation of chemical reactions catalyzed by zeolites will be presented in Section 13.3. 

Alkenes from ic,ds-diols. This conversion can be effected in a two-step, one-pot process. The diol is converted into the l-dimethylamino(methylene) acetal by reaction with DMF dimethyl acetal. The product is converted into a trimethylalkylammonium salt, which is converted into an alkene when heated. Examples ... 

Most thermosets are molded with the compression or transfer molding process (tires, dinnerware, electrical components, etc.). Some products, usually iimdler ones, can be made using the injection molding process in specially 1 or modified injection molding machines. Some thermosets are used as Is, applied to sheets or mats of glass and other fibers, and then cured under low) pressure and heat. (Examples are plywood, particle board, structures, etc.)... 

In contrast to thermoplastics, the polymerisation process for thermosets leads to the creation of a single giant three-dimensionally crosslinked molecule. The crosslinking process is generally irreversible and the resulting material will thus not melt upon subsequent heating. Examples of thermosets are unsaturated polyesters (UP), epoxies and polyurethanes (PUR). 

UV absorbers transform high-energy UV radiation into comparatively harmless heat. Examples of UV absorbers include hydroxybenzophenones, hydroxybenzo-triazoles, and cinnamic acid ester. 

Figure 4-15. Distillation with direct steam heating. Example 4-4...

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