Wax layer

Paraffin wax additives are effective in overcoming surface inhibition by forming a monomolecular wax layer at the curing surface. Although effective in excluding oxygen, this waxy layer must be removed for subsequent lamination or bonding processes (see Waxes). 

The surface of the green coffee contains a cuticular wax layer (0.2—0.3% db) for both varieties. The wax contains insoluble hydroxytryptamides derived from 5-hydroxytryptamine [61 7-2] and saturated C18—C22 fatty acids. 

When diene rubbers are exposed to ozone under stressed conditions cracks develop which are perpendicular to the direction of stress. Whilst ozone must react with unstressed rubber no cracking occurs in such circumstances nor when such rubber is subsequently stressed after removal of the ozone environment. For many years such rubbers were protected by waxes which bloomed on to the surface of the rubber to form an impermeable film. This was satisfactory for static applications but where the rubber was operating under dynamic conditions the wax layer became broken and hence less effective. 

Polycyclic aromatic hydrocarbons (PAHs) are hydrophobic compounds which are absorbed by the cuticular wax layer, which acts as a trap for these pollutants. Plants experiencing PAEI exposure (for example, on the verges of roads carrying heavy traffic) often show an increased level of wax... 

Wax dropout or settling from fuel during long-term storage. The result is accumulation of a wax layer at the bottom of a storage tank. This accumulated wax can cause line and filter plugging when pumped from the tank bottom and into vehicles. 

Someone in Orchem research management had conceived an idea for a better product. The weakness of spirit duplication systems was that the wax sheets inevitably leaked color onto the hands of the people who handled them. Secretaries hated them, as the intense colors in the wax matrix transferred to clothing, causing severe staining. Why not have a leucodye, i.e., a colorless precursor of a dye present in the wax layer, and moisten the receiver sheet with an alcoholic solution of an oxidant For a variety of reasons, the preferred oxidant was chlor-anil (tetrachlorobenzophenone), an inexpensive, colorless, and effective material (Scheme 4.6). Unfortunately, this compound also gave rise to hydrochloric acid... 

The bulb of a new glass electrode is sometimes coated with a wax layer for protection. This should be removed by dipping the electrode into an organic solvent (specified in the instruction leaflet), and then soaking the electrode in dilute hydrochloric acid for a few days. When not in use, the electrode should be kept in distilled water or in dilute hydrochloric acid. 

Beneath the epicuticular wax layer is the cuticle which bounds the epidermal cells and lines the sub-stomatal cavities. Structurally, it is noncellular and often multi-layered, comprising an inner region which merges with cellulose fibrils of the epidermal cell wall (cuticular layer, fibrillar in organization) (2). The chemical component of the cuticle proper is an... 

It is important to understand the structure of insect cuticle before we study the cuticu-lar penetration of insecticides. Figure 6.1 shows the structure of insect integument. The integument is the outer layer of the insect, comprising the epidermis and the cuticle. The epicuticle is generally about 1 micron in thickness. It can be composed of as many as four sublayers the cement layer (outermost), the wax layer, the polyphenol layer, and the cuticu-lin layer. The epicuticle, which makes up about 5% of the total thickness of the cuticle, contains lipids, lipoprotein, and protein and, therefore, it is lipophilic. Beneath the epicuticle lies the procuticle, which comprises the exocuticle and the endocuticle. This is essentially a hydrophilic chitin-protein complex containing considerable quantities of water. The endocuticle is soft and is the major constituent of larvae and soft-bodied insects. It is composed of microfibers of chitin and protein, which may impart elasticity to the cuticle. Above this section, the exocuticle is predominant in hard-bodied insects and forms most of the cuticle in adult beetles. It is present only as a thin layer in many larvae and in the hard parts of... 

Singh, G.J.P. and Thornhill, R.A., Pharmacokinetics of dieldrin with special reference to its metabolism in the epicuticular wax layer in Calliphorn erythrocephahi, Gen. Pharmacol., 11, 283,1980. 

Coniferous needles were separated due to different age class and dried for 48 h at room temperature. For the analyses of the compounds in the surface wax layer, the needles were extracted twice for 0.5 min with dichloromethane by ultrasonic treatment [49,50]. The dichloromethane was evaporated and the residue dissolved in hexane. After extraction with dichloromethane the needles were dried and crushed. The crushed needles were extracted twice with hexane by ultrasonic treatment for 1 h. The hexane extracts were evaporated and the analysis continued as above. 

It stabilizes the lyotropic liquid crystalline state of biological assemblies relative to the crystalline state, due to the so-called chiral bilayer effect, which will be discussed in more detail in Section 4.2. For example, 10-nonacosanol, extruded from the lipophilic wax layer of pine needles, forms fluid lipid tubules rather than crystals. Although it is difficult to establish the enantiopurity of the natural product, the fact that synthetic pure enantiomers produce tubules while the racemate gives platelets suggests that the biologically relevant morphology is attained because of the enantiopurity of the biomolecule. °... 

Air pollutants act partly by direct fashion, and partly by indirect fashion. Hence, SO2 can act either directly on spruce needles (wax layer, stomata openings, nutrient content, buffer capacity), or in the form of sulfuric acid in the soil via H- and Al-ions on plant roots. Gaseous pollutants act aboveground, whereas total deposition acts below-ground. 

The effect of higher Reynolds number in lowering the thermal resistance due to the presence of the wax layer is shown. The reduction is in keeping with a reduced wax layer thickness due to the higher shear at a higher Reynolds number. 

---