The role of hydrogen in ziegler‐natta polymerizations

Comparison of Gas and Liquid Propylene Polymerization Technique – Hydrogen Effect on Thermal, Rheological, and Morphological Properties of PP

“…Figure 3 shows that the measurement points for both GP and LP, fit well by using Equation (4). Contrary to the first results of Natta et al, but in accordance with numerous other investigation using modern ZN catalysts, the MW decreases as the hydrogen amount increases even at very high hydrogen concentration, due to an increase in the chain transfer reaction of hydrogen 13–27…”

“…As mentioned before, the presence of hydrogen increases the initial polymerization rate significantly. It is well known that the hydrogen influences the activity of the catalysts, but the mechanism of the activation process by hydrogen is still discussed controversially 13–27. Although different theories exist, the majority of opinion is that deactivated sides (so called dormant or sleeping sides), caused by irregular 2,1 insertion of the monomer, will be reactivated by hydrogen and with that the total activity of the catalyst increases.…”

“…In the past, many endeavors have been made to achieve a continuous improvement in reactor operability and better control of the polymer properties. In particular, a lot of kinetic and morphological analyses form the basis of these endeavors, which is supported by numerous publications 4–31. Furthermore, there are many articles discussing the final properties of plastic parts influenced by structural changes and processing conditions 32–36.…”

Library synthesis and characterization of 3‐aminopropyl‐terminated poly(dimethylsiloxane)s and poly(ϵ‐caprolactone)‐b‐poly(dimethylsiloxane)s

“…The synthesis of both the tetramethylammonium 3-aminopropyl dimethylsilanolate catalyst and APT-PDMS was done according to the work of Hoffman and Leir. 6 To synthesize the catalyst tetramethylammonium 3-aminopropyl dimethyl silanolate, in a 50-mL, three-necked, round-bottom flask, 3.60 g of tetramethylammonium hydroxide pentahydrate and 2.49 g of BAPTMDS were mixed. The molar ratio of tetramethylammonium hydroxide pentahydrate to BAPTMDS was 2:1.…”

“…[1][2][3] Organofunctional PDMS oligomers can be prepared by the acid-or base-catalyzed ring-opening polymerization of a cyclic tetramer, octamethylcyclotetrasiloxane (D 4 ), in the presence of a disiloxane or low-molecular-weight oligomer having the desired end groups with several different catalysts depending on the desired molecular weight, purity, cost, and ease of application. [4][5][6][7][8][9][10][11] PDMS has a very low surface energy and a very low solubility parameter, which makes it immiscible with most organic polymers. The use of PDMS directly as a surface-modifying additive in an organic polymer is limited by its tendency to migrate to the polymer-air interface and its rejection from the bulk material due to the lack of covalent linkages.…”