Rheological properties and crystallization behaviors of long chain branched polyethylene prepared by melt branching reaction

Abstract

<jats:title>Abstract</jats:title> <jats:p>Long chain branched polyethylene (LCBPE) without gel was prepared by melt branching reaction in a Haake torque rheometer in the presence of peroxide and different multi-functional acrylate monomers, and the optimal reaction time was determined according to the transient torque curves. The Fourier transform infrared (FTIR) results indicated that multi-functional monomers had been grafted onto HDPE backbone. Rheometer, <jats:sup>13</jats:sup>C NMR, and high-temperature gel permeation chromatography (HT-GPC) coupled with triple detectors were used to characterize the microstructure of the LCBPE. The results showed the LCB content and the degree of branching increased with the increasing of functionality of the multi-functional monomers. Moreover, the LCBPE samples exhibited higher apparent zero shear rate activation energy and clear strain-hardening behavior compared with pure HDPE. Various rheological plots including viscosity, storage modulus, loss angle, and Cole-Cole plots were used to distinguish LCBPE from linear HDPE. A possible mechanism for melt branching reaction was also discussed in this paper. Differential scanning calorimetry (DSC) and polarized optical microscopy (POM) were used to study the influences of LCB on the crystallization behavior and crystal morphology of all samples. It was found that the melt temperature and crystal morphologies of LCBPE were evidently different from that of pure HDPE due to the introduction of LCB.</jats:p>

Modification of Interfacial Interactions in Ceramic-Polymer Nanocomposites by Grafting: Morphology and Properties for Powder Injection Molding and Additive Manufacturing

“…HDPE00 shows a Newtonian plateau at low angular frequencies, whereas AAHDPE00 exhibits a pseudoplastic behavior in the range of angular frequencies evaluated. The increase in viscosity in the low shear region and the pseudoplastic behavior have been reported for long chain branched polyethylene [64,65] as well as for polyethylene grafted with polar groups such as maleic anhydride, glycidyl methacrylate and acrylic monomers [66,67] or silane [68]. Thus, the differences in the complex viscosity of AAHDPE00 and HDPE might be caused by the branching and partial crosslinking of the poly (acrylic acid) employed in the polymer grafting, which results in a more effective entanglement [67]; the hydrogen bonding between the carboxylic acid in the acrylic acid promotes this behavior [67].…”

“…Thus, the differences in the complex viscosity of AAHDPE00 and HDPE might be caused by the branching and partial crosslinking of the poly (acrylic acid) employed in the polymer grafting, which results in a more effective entanglement [67]; the hydrogen bonding between the carboxylic acid in the acrylic acid promotes this behavior [67]. The branching [65] or partial crosslinking [68] of the grafted polyethylene might also be the cause of the trend in the storage modulus (Figure 6b). At low angular frequencies, the G' of AAHDPE00 is higher than that of HDPE00, whereas the storage modulus of HDPE00 is slightly higher at high angular frequencies.…”

Star Shaped Long Chain Branched Poly (lactic acid) Prepared by Melt Transesterification with Trimethylolpropane Triacrylate and Nano-ZnO

“…As shown, the curves of Sample B2 and B6 get broader and shift to a lower M w region compared with the pristine PLA, indicating that the degradation reaction took place during the melt transesterification process. An evident shoulder can be seen at the high molecular weight region on the curve of B2, which corresponded to the sparsely long branching components [40,41]. However, the shoulder disappears in the curve of B6, whose melt blending time was up to 400 s, indicating that obvious chain degradation occurs owing to the long-time melt transesterification reaction and more and more short chains are generated, which is also reflected in the molecular weight value.…”

Influence of polypropylene topological structure evolution during melt branching reactive processing on its melt performances

“…It is suggested that TMPTA has been grafted onto the PP backbone through the reaction of the macromolecule free radical to the carbon‐carbon double bond of TMPTA. According to the normalized FTIR spectra, the relative grafting degree (RGD) could be calculated as follows: where A 1743 is the absorbance at 1743 cm −1 , characterizing the carbonyl groups of the ester (―COO) in the TMPTA; and A 1169 is the absorbance at 1169 cm −1 , characterizing the methyl groups (―CH 3 ) on the PP backbone. The RGD values are listed in Table .…”