Nucleating Agents for Polyethylene

Dotson, Darin L.

doi:10.1002/9781119159797.ch36

Cited by 5 publications

(8 citation statements)

References 43 publications

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“…3 °C. This is a rather significant result, since specific nucleating agents of HDPE produce enhancement of its crystallization temperature of 1–3 °C at most, due to the intrinsically high number of active heterogeneities present in this polymer. − …”

Section: Resultsmentioning

confidence: 99%

Surface Nucleation of Dispersed Polyethylene Droplets in Immiscible Blends Revealed by Polypropylene Matrix Self-Nucleation

et al. 2021

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Usually, the nature of surface-induced nucleation in polymer blends is not easily disclosed. A novel approach for studying surface-induced crystallization in blends of semicrystalline polymers is proposed here. It consists of detecting variations in the crystallization kinetics of the dispersed phase with changing the crystalline state of the matrix through self-nucleation. It can be used only when the dispersed phase has a lower melting temperature than the matrix phase. As a case study, the crystallization behavior of dispersed polyethylene droplets in a polypropylene matrix was investigated. An enhancement of crystallization kinetics of polyethylene was achieved when the lamellar thickness of polypropylene increased, and it was proved by the formation of a transcrystalline layer of polyethylene at the interface, as observed by scanning electron microscopy. Compared to the self-nucleated neat polyethylene, the efficiency of the nucleating effect of polypropylene toward polyethylene was estimated around 140%. This result together with a very low value for the interfacial free energy difference as obtained from isothermal crystallization measurements is evidence that such surface-induced nucleation occurs through epitaxial growth. Moreover, a mechanism of polyethylene nuclei formation through epitaxy, which was proposed in the literature, was proved to be valid for blends of the two polymers through small- and wide-angle X-ray scattering structural analysis. While epitaxy between polyethylene and polypropylene was previously shown only for ideal systems such as thin-layered films, it is hereby reported for common melt mixed blends of the two polyolefins.

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Section: Resultsmentioning

confidence: 99%

Surface Nucleation of Dispersed Polyethylene Droplets in Immiscible Blends Revealed by Polypropylene Matrix Self-Nucleation

et al. 2021

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“…With the addition of this NA, the crystalline peak temperature ( T c ) could increase by 1–5 °C with the cooling rate of 20 °C/min, depending on the type of PE . It was reported that Ca-HHPA could epitaxially interact with the (100) plane of PE and thus to induce the orientation of PE crystalline lamellae . In the previous studies, − the epitaxial crystallization of PCL on PE substrate had already been reported and it was ascribed to their quite similar crystal structure.…”

Section: Introductionmentioning

confidence: 88%

“…The calcium hexahydrophthalic acid (Ca-HHPA. It has a chemical structure as shown in Figure S1) is the main ingredient of special commercially available NA for PE developed by Milliken & Company . With the addition of this NA, the crystalline peak temperature ( T c ) could increase by 1–5 °C with the cooling rate of 20 °C/min, depending on the type of PE .…”

Section: Introductionmentioning

confidence: 99%

“…It has a chemical structure as shown in Figure S1) is the main ingredient of special commercially available NA for PE developed by Milliken & Company . With the addition of this NA, the crystalline peak temperature ( T c ) could increase by 1–5 °C with the cooling rate of 20 °C/min, depending on the type of PE . It was reported that Ca-HHPA could epitaxially interact with the (100) plane of PE and thus to induce the orientation of PE crystalline lamellae .…”

Section: Introductionmentioning

confidence: 99%

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Nucleation Efficiencies of Calcium Hexahydrophthalic Acid for Poly(ε-caprolactone) Crystallization

Sun

Feng

2021

ACS Appl. Polym. Mater.

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Poly(ε-caprolactone) (PCL) has received widespread attention due to its biocompatibility and biodegradability. Introduction of the nucleating agent (NA) is an effective method to control the crystallization behavior of semicrystalline polymer and regulate their properties. Unfortunately, only a few NAs for PCL have been reported up to now. In this work, considering the structure similarity between PCL and polyethylene (PE), we tried to synthesize the calcium hexahydrophthalic acid (Ca-HHPA), the main ingredient of a special NA for PE, by neutralization reaction in deionized water and investigated its possible nucleating effect for PCL. It was interesting to find that the as-synthesized product undergoing different thermal treatments exhibited obviously different nucleation effects. The Ca-HHPA80, obtained by drying at 80 °C for 24 h, only slightly increased the crystallization peak temperature (T c) of PCL by no more than 1.7 °C with the loadings investigated, while Ca-HHPA80-200, obtained by further annealing Ca-HHPA80 at 200 °C for 5 min, could notably increase the T c by 5.2 °C in similar dosages. The results of structural characterization indicated that the Ca-HHPA80 and Ca-HHPA80-200 were crystalline monohydrated and dehydrated carboxylate, respectively. The investigation of structural evolution behavior during the heating process revealed that the monohydrated carboxylate lost its crystal water and gradually transformed to dehydrated one at 140–190 °C accompanied with the conformational transformation of the methylene from gauche to trans conformation, which led to a great variation of their alkyl chain packing in crystal lattice. Based on the epitaxial crystallization theory, the possible reasons for the obviously improved nucleating efficiency of Ca-HHPA80-200 were discussed. The alkyl chain packing of Ca-HHPA80-200 leading to the lower mismatching with the PCL crystals may be accountable for its relatively higher nucleation efficiency.

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“…Controlling the crystallization of polyolefins in order to facilitate or even enable processing at economical speed is a constant challenge in the polymer industry. The application of nucleating agents [ 1 , 2 , 3 , 4 , 5 , 6 ], but also of minor blend components [ 7 , 8 ], has been studied in the past more for isotactic polypropylene (iPP) than for polyethylene (PE), simply because the latter normally crystallizes much faster. This is quite different for PE plastomers, which are essentially single-site catalyst-based homogeneous linear low-density PEs (LLDPEs) combining low crystallinity, softness, and elasticity [ 9 , 10 ].…”

Section: Introductionmentioning

confidence: 99%

Gelation and Crystallization Phenomena in Polyethylene Plastomers Modified with Waxes

et al. 2021

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Polyethylene (PE) plastomers, single-site catalyst-based homogeneous linear low-density PEs (LLDPEs), combine low crystallinity, softness, and elasticity, making them ideal candidates for numerous applications such as hot-melt adhesives (HMA). As plastomers crystallize rather slowly, a number of possible low molecular weight polyolefin components were tested to accelerate solidification. An ideal modifier should accelerate solidification while maintaining transparency and softness of the base polymer. A Queo plastomer type was modified with different PE and PP waxes at concentrations of 5 to 25 wt.-%. Next to conventional calorimetry, a rheological technique was applied to study solidification. The resulting morphology was studied by atomic force microscopy, and the final compositions were investigated regarding their mechanical and optical performance. Accelerated solidification was observed in all cases, but a quite different course of structure formation could be concluded. PE waxes dissolve in the melt state, forming a lamellar network during cooling, whereas PP waxes form a heterogeneous blend in the melt for which the wax droplets solidify before the matrix. The particulate-type modification by the PP wax also affects stiffness less while retaining transparency better.

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Nucleating Agents for Polyethylene

Cited by 5 publications

References 43 publications

Surface Nucleation of Dispersed Polyethylene Droplets in Immiscible Blends Revealed by Polypropylene Matrix Self-Nucleation

Surface Nucleation of Dispersed Polyethylene Droplets in Immiscible Blends Revealed by Polypropylene Matrix Self-Nucleation

Nucleation Efficiencies of Calcium Hexahydrophthalic Acid for Poly(ε-caprolactone) Crystallization

Gelation and Crystallization Phenomena in Polyethylene Plastomers Modified with Waxes

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