β-Nucleation of isotactic polypropylene: Chain structure effects on the effectiveness of two different nucleating agents

Abstract

Of all crystal modifications of isotactic polypropylene (iPP), the β-phase has received particular attention in both academia and industry because of the toughness increase resulting from its formation. Several novel nucleating agents have been presented and studied in recent years, most prominently the 'lanthanum complex' WBG. The majority of these studies are based only on one type of iPP, mostly an iPP homopolymer, despite the fact that chain irregularities are known to affect β-phase formation negatively. In the present study, several different iPP homo-and copolymers based on Ziegler-Natta and single-site catalysts differing mostly in chain defect concentration were used to evaluate the sensitivity of a 'reference' nucleating agent, quinacridonequinone, as well as WBG to chain structure effects. The results in terms of crystal structure, as well as mechanics, indicate a much greater sensitivity of WBG, resulting in a massively reduced β-phase formation for SSC-iPP hompolymers and ZN-iPP random copolymers with ethylene. An increase of γ-phase content in nucleation of the polymers with least regular chain structure hints at some duality for WBG as also observed for other β-nucleating agents before.

Organogelators with dual β- and α-nucleating ability in isotactic polypropylene

“…Unfortunately, the formation of β-modification in random copolymers was not observed, because this polymer grade has the lowest chain regularity, and the selectivity of the nucleating agent is not shifted to the β-form enough to form considerable amount of β-modification during the crystallization process. We may note that the distribution of C2 units in random copolymers influences the polymorphic composition and occasionally it can suppress the formation of β-modification [46][47][48][49]. In addition most random copolymer samples crystallize below 100 °C, which is the lower temperature limit of the formation of β-form [39].…”

Preparation and balanced mechanical properties of solid and foamed isotactic polypropylene/SEBS composites

“…As indicated in the literatures, β nucleating agent is reported to be one of the mostly used additives to improve the impact strength of PP by increasing the ratio of β form crystals in the matrix 35–37 . Effect of the combination of two nucleating agents on the crystallization behavior of PP was also reported 35,38 . Adding a second phase into the polymer matrix is another widely used way to toughen PP, 39–45 in which nanofillers were often used to be the second phase 46–50 .…”

In situ synthesis of calcium pimelate as a highly dispersed β‐nucleating agent for improving the crystallization behavior and mechanical properties of isotactic polypropylene

“…Due to its superior mechanical qualities, non‐toxicity, low relative density, heat resistance, chemical resistance, and ease of manufacture, isotactic polypropylene (iPP) is utilized extensively 1–5 . Nonetheless, the high brittleness temperature, low impact resistance, and insufficient transparency of iPP are some of its drawbacks 2,6,7 . Hence, modification of iPP is indispensable before application.…”

“…[1][2][3][4][5] Nonetheless, the high brittleness temperature, low impact resistance, and insufficient transparency of iPP are some of its drawbacks. 2,6,7 Hence, modification of iPP is indispensable before application. Modification of iPP can be divided into two methods, namely, physical modification and chemical modification, of which the addition of nucleating agents as a physical modification method is one of the most active and commonly used effective methods.…”