Addition-type adhesives, processibility

Tannin-containing woods also darken with ammonia, a process which is usefully employed in darkening oak furniture by fuming . Ammonia stains can originate from animal glue, amino-type adhesives and concrete additive sources, particularly where damp conditions exist. 

Like other pyrolysis oil processes. Biocarbons Corporation s reactor produces a large number of oil compounds. For mixed hardwood (maple, birch and beech) pyrolyzed at typical operating conditions, 69 peaks were found by GC/MS analysis. Of these, the 14 peaks present at above 2 mole percent, represented 45 mole percent of the product that came through the GC. The 27 peaks between 1 and 2 mole percent, represented an additional 37 mole percent of the product. These compounds that were identified are listed in Table 1, in order of appearance (time). Several of the 4-position groups could also be occurring at the 3 position. All are reactable to make a phenol-forma Idehvde type adhesive. Pyrolysis oil from pine that was nude at the same operating condition (but has not yet been tested for adhesive use) had essentially the same compounds present at >1 mole percent, but at different relative concentrations. Some lower concentration compounds such as fatty acids are only produced from pine, but these compounds are specific to softwoods and the composition of softwoods. A comparison between the mixed hardwoods and pine products is shown in Table 2. 

The type of process used also indicates the addition of polymer modifiers. Blow-molding requires that the polymer flows easily, while retaining good cohesive strength when molten, to avoid tears and voids. Melt flow modifiers are typically used for this purpose and include fatty acid esters, oleoamides, and adipates. Compounds of this type often also serve to prevent blocking (adhesion of one side of a bag to the other). 

The lubricated wear described above is squarely at odds with the behavior illustrated in Fig. 14-6 and with the wear-reducing action of 22% di-t-octyl disulfide in white oil reported by Dorinson and Broman [10] and shown in Table 11-6 (Chapter 11, Section 11.2.1). If Eqn 14-49 is a correct representation of additive action, it should be valid for both the reduction and the increase of wear by such action. To reduce wear, the first term on the right-hand side of the equation must control the overall rate and one way to do so is for the lump removal factor wear rate. But there is no physical necessity that q remains constant for all conditions of load, pressure, speed or state of lubrication. Since in physical terms the predominant effect of the lubricant is to inhibit the asperity adhesion process, it is not unanticipated that the average size of the transferred and detached particles as well as their number will be decreased by lubrication. It is to this latter type of mechanistic process that we must look for an explanation of why such parameters as contact pressure, rubbing speed and material properties affect the balance between the inhibition or promotion of wear by additive action and the transition from smooth lubricated wear to catastrophically damaging wear behavior such as scuffing. 

Addition-type polyimides, which are thermosetting resins, were developed to improve the processability of polyimides, but their thermal stability is severely degraded by the presence of aliphatic bonds in place of the aromatic nuclei. However, the adhesive strength has been evaluated for the bismaleimide- (Section 4.3.4.1), bisnadimide- (Section 4.3.4.2) and acetylene-terminated (Section 4.3.4.3) imide oligomers. 

Cross-linking, at high temperature, of the two-part formulations is not related in any way to the action of humidity. The basic process is an addition on an unsaturated site, which depends on the presence of catalysts. This leads to formulations that are difficult to use, and there is a tendency to replace these with silicone-acrylate type adhesives (polydimethylsiloxanes a,(io-acrylate), just as effective but easier to use. The problems associated with use do not arise with the humidity cross-linking formulations. But with these formulations, the operating conditions are neither easy to master (too much water can have a very negative effect), nor are they conveniently reproducible. 

Sodium nitrate is also used in formulations of heat-transfer salts for he at-treatment baths for alloys and metals, mbber vulcanization, and petrochemical industries. A mixture of sodium nitrate and potassium nitrate is used to capture solar energy (qv) to transform it into electrical energy. The potential of sodium nitrate in the field of solar salts depends on the commercial development of this process. Other uses of sodium nitrate include water (qv) treatment, ice melting, adhesives (qv), cleaning compounds, pyrotechnics, curing bacons and meats (see Food additives), organics nitration, certain types of pharmaceutical production, refining of some alloys, recovery of lead, and production of uranium. 

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