Novel nucleating agents for polypropylene and modifier of its physical-mechanical properties

Effects of nucleating agent content on the microstructure and macroscopic performances of polypropylene analyzed by non‐isothermal crystallization behaviors and isothermal crystallization morphologies

“…Cooling rate ( C min À1 ) reached 25 from 10 C min À1 , the values of nucleated PPs were greatly higher than neat PP with the stable ΔH m of 50.4 J g À1 . Similarly, Balkaev et al 23 reported the improvements of ΔH m from 93 to 101 J g À1 caused by introducing the novel nucleating agent with the content of 2.5 phr. In comparison, the enthalpy values in this work were relatively higher, ascribed to the great crystallization ability of the PP used.…”

“…Then the melting behaviors were conducted by the program that the rate of 10 C min À1 was used to heat samples to 200 C. Based on the obtained melting curves, the melting enthalpies of samples were measured and the crystal ratios (X c ) were estimated by Equation (1). 23,29,32 T A B L E 1 Nomenclature of samples compositions.…”

“…1,20,21 According to the above factors, PP can complete crystallization in the form of α, β, γ, δ and a mesophase and the first two phases possessing the higher economic utility are commonly investigated. 1,[22][23][24] Generally, the α phase with a monoclinic structure is the most stable in thermodynamics and easiest to form in processing naturally, contributing to the higher stiffness, while the β phase with a hexagonal structure is not thermodynamically stable and obtained at certain conditions or specific nucleating agent (NA) which can improve the impact strength and heat distortion temperature. 6,22,24 Besides, the polymer crystallization process consists of the formation of primary nuclei and the growth of crystalline grains.…”

“…26 Nevertheless, too long crystallization period decreases the production efficiency and causes severe warpage, which also influences the macroscopic performances by existing residual crystals and varies the composition of crystalline phases, especially as the temperature and force field display instabilities. 22,23 To weaken the effects of external factors on microstructure and guarantee the stable phase composition corresponding to the desirable properties, introducing a suitable nucleating agent is one commonly practical and efficient approach. 22,26 Balkaev et al 23 found that one dicalcium salt with a unique core-shell structure as a novel nucleating agent obtained by the environmentally friendly method with low cost highly improved the efficiency in forming α-nucleation and increased the crystallinity and flexural modulus to a certain degree.…”

“…22,23 To weaken the effects of external factors on microstructure and guarantee the stable phase composition corresponding to the desirable properties, introducing a suitable nucleating agent is one commonly practical and efficient approach. 22,26 Balkaev et al 23 found that one dicalcium salt with a unique core-shell structure as a novel nucleating agent obtained by the environmentally friendly method with low cost highly improved the efficiency in forming α-nucleation and increased the crystallinity and flexural modulus to a certain degree. Generally, the nucleation mode is transformed from homogeneous to heterogeneous nucleation as a nucleating agent provides plentiful nuclei for chain segments to settle and arrange which shortens the crystallization period drastically.…”