Abstract
Application of nucleating agents is the most versatile and industrially applied way to manipulate the crystalline structure of isotactic polypropylene (iPP). Various materials possess a nucleating effect, but from the viewpoint of dispersibility, the partially soluble ones are the most advantageous. Our objective was to synthesize new N,N′-dicyclohexyldicarboxamide homologues and study their applicability as nucleating agents in iPP. Carbon-13 nuclear magnetic resonance (13C NMR) and infrared spectroscopy were used to prove that the synthesis reactions were successful. Thermal stability of the compounds was investigated with simultaneous thermal analysis. Nucleating efficiency and solubility were characterized by polarized light microscopy and differential scanning calorimetry. Polarized light microscopy was also applied to study the effect of novel additives on the morphology of iPP. The properties, important from the viewpoint of applicability, were also investigated. Tensile tests were performed to characterize the main mechanical properties, and standard haze measurements were performed to characterize optical properties. It can be concluded that the investigated compounds are partially soluble nucleating agents and influence the crystalline structure of iPP. Most of the studied compounds have a moderate nucleating efficiency, but a very interesting dendritic structure develops in their presence. Two of them proved to be non-selective β-nucleating agents, which result in a remarkable improvement of impact resistance and higher opacity.
Highlights
IntroductionIn the case of semicrystalline polymers, the crystalline structure developing in the material is fundamentally important from the viewpoint of the properties
It is well-known how strongly the properties of a material depend on its structure
The main objective of our work was the thorough characterization of a family of N,N′-dicyclohexyldicarboxamides, from the viewpoint of applicability as nucleating agents in Isotactic polypropylene (iPP)
Summary
In the case of semicrystalline polymers, the crystalline structure developing in the material is fundamentally important from the viewpoint of the properties. The thermodynamically stable polymorph is αiPP; the β-modification can develop in significant amounts during processing if favorable conditions are present. This can be advantageous from the viewpoint of applicability, due to the higher impact resistance of β-iPP compared to that of α-iPP.[2] The crystalline structure formed in a product, besides conditions of crystallization (temperature, rate of cooling), depends on the presence of materials apart from the polymer.
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