Scale nucleating agents

For evaluating the efficiency of the nanostructured interface for cell nucleation, the particle density of PPE, as a measure for the number of nucleating sites available for nucleation, is plotted versus the nucleation density observed for the foam (Fig. 21). For comparison, the previously found values of the uncompatibilized PPE/SAN blend are added. For PPE/SAN, even the relatively high number of PPE particles of around 5 x 10ncm-3 only leads to nucleation of approximately 2.5 x 1010 cells cm-3, i.e., only 1/20 of the potentially available PPE particles act as cell nucleating agents. Via compatibilization, however, not only the particle density of PPE and the nucleation density can be increased, but also the efficiency is strongly enhanced. While the number of cells directly scales with particle density, more than two foam cells are nucleated by one PPE particle. 

Among the three known crystalline structures (a, j3, y) of isotactic polypropylene (PP), the -modification is certainly the most fascinating one. While the stable a-structure develops under standard process conditions, the occurrence of the /J-form has to be forced (i) by directional crystallization in a temperature gradient field [1-3] (ii) by shear-induced crystallization [4-12] or (iii) by the addition of specific nucleating agents [13-31]. This latter technique is preferred at the industrial scale. 

This difFeience has imphcation on impact resistance and haze. Impact resistance increases by 100% with addition of 0.15 wt% of the nano-scaled styrene butadiene rubber (nucleating agent used in this study). Haze increases from 63.4% for iPP to 100% for iPP containing 0.3 wt% of nucleating agents. The increased impact strength is caused by the presence of larger number of small spherulites. The haze increase is caused by the increase in overal crystallinity of iPP. ... 

Methods of scale control are sequestration or chelation, film formation, or nucleation. A particular scale inhibitor may act as both a sequestration and a nucleation agent. 

Scale control chemicals that act as nucleating agents frequently are the only chemicals that can be economically justified for use in oil wells producing large volumes of water and heavy scale deposits. 

A scale has been proposed by which the effectiveness of a nucleation catalyst can be assessed. In addition to comparing the crystallization temperature on cooling the nucleated polymer with that of the pure polymer, the crystallization temperature of the self-seeded polymer is also taken into account.(268,269) The self-seeded polymer (270) is taken to represent the ideal nucleated system. The efficiency of a nucleating agent, E, expressed as a percentage, is given as (268,269)... 

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