Seeding procedures

The seeding procedure is described in Fig. 20 by the line abed. Its inspection shows that the concentration of the monomer left at the time when all the initiator is consumed remains the same whether the monomer is added at once or in two portions. Moreover, the total concentration of the added monomer must exceed a critical value to allow for quantitative consumption of the initiator. Thus, the seeding technique does not eliminate the broadening of molecular weight distribution caused by slow initiation of a virtually irreversible polymerization. This conclusion is confirmed experimentally 133). 

Seeding procedures are commonly employed in the pharmaceutical industries to make sure that the desired crystal form is always obtained from a preparative process [60]. It is important to appreciate that seeding often prevents the formation of kinetically favoured products. 

Seed from heel recycling with wet milling to control the mean particle size and PSD one of the most effective seeding procedures when applicable (see Example 10-1)... 

Prior to palladium pladng, the surface of the membrane support is flrst seeded with Pd particles. The seeding procedure involves impregnation of the ceramic support with a chloroform soluAon of palladium acetate, followed by calcination and reduction in flowing hydrogen or aqueous hydrazine solutions [5]. 

Table 17.2 Seeding procedures reported in different papers and patents...

Coverage uniformity problems can happen when tubular supports are used horizontally and without any rotation. In this case, zeoUte seeds will be deposited preferentially in the bottom of the support owing to the effect of the gravitational force. To overcome this problem a new seeding procedure for tubular membranes has been designed combining for the first time ... 

Gu et al studied the effects of the seeding procedures and the conditions of hydrothermal treatment on the FAU membranes quality. For the seeding stage, they used rubbing and dip-coating. They found that dip-coating combined with... 

Seeded procedures are industrially the most important emulsion polymeri/.ation techniques since all uncertainties in connection with particle nucleation can be avoided see also ref. (81). 

Another common way to control particle size, as long as initial supersaturation is regulated, is by the addition of either homoepitaxial or heterogeneous particles to act as seeds for the nucleation of the desired phase. As the seed concentration is increased above a critical concentration, known as the intrinsic nucleation concentration, the addition of seeds can be effective in controlling particle size. The interested reader is referred to an article describing the seeding procedure used for this system (26). 

Literature concerning the chemistry of loline alkaloids was first reviewed in 1972 (20). Robbins et al. (21), using much milder isolation procedures than those of Yates and Tookey (18), also reported the occurrence of AT-acetylloline (6), AT-acetylnorloline (7), and N-formylloline (9) in F. arundinacea seed. Procedures for multiple-gram scale isolation of loline dihydrochloride from F. arundinacea seed, and its conversion in high yield to any of the monomeric... 

Hasegawa, M., Chung, C.M., Muro, N., and Maekawa, Y, Asymmetric synthesis through the topochemical reaction in a chiral crystal of a prochiral diolefin molecule having a cisoid molecular structure and amplification of asymmetry by a seeding procedure, J.Am. Chem. Soc., 112, 5676, 1990. 

Algieri C, Bernardo P, Barbieri G and Drioli E (2009), A novel seeding procedure for preparing tnbnlar NaY zeolite membranes , Micropor Mesopor Mat, 119, 129-136. 

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