Self-organization and polyolefin nucleation efficacy of 1,3:2,4-di-p-methylbenzylidene sorbitol

114

ABSTRACT:The nucleation activity of the sorbitol derivatives 1,2,3,4-bis(3,4-dimethylbenzylidene sorbitol) and methyldibenzylidene sorbitol are compared with that of talc, a conventional nucleating agent for the monoclinic crystalline phase of isotactic polypropylene. The thermal parameters associated with the dynamic crystallization process are studied as a function of the cooling rate by differential scanning calorimetry, and the nucleating efficiency is assessed by comparison with self-nucleation, the highest values being observed for 1,2,3,4-bis(3,4-dimethylbenzylidene sorbitol) over the whole concentration range. The nature of the polymer crystals formed in the nucleated polymer was studied by X-ray diffraction, and the data show an increase in a preferred orientation of the polymer crystallites with increasing concentration of nucleating agent.

Section: Resultsmentioning

confidence: 99%

Comparative study of the nucleation activity of third‐generation sorbitol‐based nucleating agents for isotactic polypropylene

Marco

Ellis

Gómez

et al. 2002

114

“…The crystallization of the material plays an important role for the end‐use properties of PP as for other semicrystalline polymers. Different factors have been found to influence the crystallization behavior of isotactic PP: stereoregularity,17, 18 comonomer type and content,19 molecular weight distribution (MWD),20, 21 and heterogeneities like catalyst residues and nucleating agents 22, 23…”

Section: Introductionmentioning

confidence: 99%

Propylene–ethylene random copolymers: Comonomer effects on crystallinity and application properties

Gahleitner

Jääskeläinen²,

Ratajski

et al. 2005

119

110

For understanding the correlation chain from the polymer structure to the final application properties of propylene-ethylene random copolymers, four commercial grades with different ethylene content (0 -8 mol %) but identical molecular weight distributions were investigated. Structural investigations concerning the comonomer distribution, using two different techniques (temperature rising elution fractionation and stepwise isothermal segregation), showed an increase of inhomogeneity with the total comonomer content, which was reflected for temperature rising elution fractionation in a widening of the elution temperature range. Crystallinity and crystallization speed studies confirmed the reduced overall crystallinity and increase of ␥-modification content as reported previously, but they also showed the reason for these effects in the distinctive decrease of the spherulitic growth speed. Good correlations of all these parameters to the mechanical performance of the four materials were obtained.

“…At high concentrations, the decrease in the haze value is limited at the onset of saturation. Shepard et al . explained that the formation of large‐scale microstructures, that is, a coarse fibrillar network and numerous fibril bundles, is induced beyond the saturation level, leading to an increase in light scattering and reduced clarity.…”

Section: Resultsmentioning

confidence: 99%

“…Sorbitol derivatives, such as dibenzylidene sorbitol, 1,3:2,4‐di‐( p ‐methylbenzylidene)sorbitol, and DMDBS, are recognized nucleating agents and clarifiers. Several reports have revealed that the self‐organization mechanism of sorbitol molecules, in which intramolecular hydrogen bonding between hydroxyl groups affects the formation of nanofibrillar networks, leads to physical gels . In modest shear processes, the sorbitol fibrils are aligned in the direction of flow and nucleate polymer chains by epitaxial interaction.…”

Section: Introductionmentioning

confidence: 99%

Enhancement of drawdown force in polypropylene containing nucleating agent

Phulkerd

Nakabayashi

Iwasaki

et al. 2018

The effect of the nucleation efficiency of three commercial nucleating agents, such as 1,3:2,4‐bis(3,4‐dimethylbenzylidene)sorbitol (DMDBS), sodium 2,2′‐methylene‐bis‐(4,6‐di‐tert‐butylphenyl)phosphate (SMBP), and magnesium silicate (talc), on the melt‐stretching performance of isotactic polypropylene (PP) is studied. It is found that the addition of 0.5 wt % of a nucleating agent enhances the crystallization temperature and that effect is pronounced for DMDBS and SMBP. Furthermore, DMDBS is more efficient than the other tested nucleating agents in enhancing the drawdown force, defined as a force required for stretching a molten strand. Nanofibers of DMDBS, which show significant alignment in the flow direction, are responsible for the rapid crystallization of PP in the flow field leading to an increase of drawdown force. The stretched strand shows a highly oriented structure in which the α‐form crystals orient to the flow direction. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47295.