NMR relaxation and pulsed-gradient diffusion study of polyethylene nanocomposites

Abstract

We performed pulsed-gradient spin-echo nuclear-magnetic-resonance (NMR) experiments on zinc oxide filled polyethylene. The molecular weights of the polyethylene samples ranged between 808 and 33,000 gmol, and four different zinc oxide samples were used: 27-, 33-, 51-, and 2500-nm-diameter particles. The results of these experiments showed that the diffusion coefficients of the polyethylene chains did not change with nanofiller content, but a drastic change is observed in the NMR relaxation spectrum in spin-spin-relaxation experiments. At fixed zinc oxide content and polyethylene molecular weight (close to entanglement), the system with the smallest zinc oxide showed the most rigid environment. At high polyethylene molecular weights, this effect was still observable but the difference between the three investigated systems was very small, suggesting that the system was dominated by entanglements.

Modeling of Entangled Polymer Diffusion in Melts and Nanocomposites: A Review

“…It was also found that τd∼M3.27 which is not in perfect accordance with the tube model predictions. In addition, in that study [59] the self-diffusion coefficients was measured by pulsed-gradient NMR [51,61] and the power law exponent was consistent with earlier studies [49,62]. Moreover, in bidisperse mixtures of 1,4 poly(butadiene), the diffusion coefficient of longer chains decreases by either increasing the chain length of short chains or reducing the weight fraction of short chains in the mixture [62].…”

“…Melt self-diffusion data for hydrogenated (or deuterated) poly(butadiene) samples (hPB and dPB, respectively) adjusted to 175 °C, as a function of molecular weight and data for six other polymers from the literature, with the global power law fit [39,42,43,45,46,48,49,50,51]. Reprinted from [39] with permission from American Institute of Physics (AIP).…”

Use of Dynamic Mechanical Analysis (DMA) for Characterizing Interfacial Interactions in Filled Polymers

“…It is important to mention that this review is focused on the interfacial interactions between the matrix and the extenders (also referred to as fillers) in filled polymer systems (e.g., coatings, composites etc.). Nuclear magnetic resonance (NMR) spectroscopy has been used to study the effect of different fillers on the chain dynamics of polymers, especially the elastomers used in the rubber industry [19][20][21][22][23][24][25][26]. Raman spectroscopy [27][28][29][30] and the dielectric relaxation spectrum [31][32][33][34][35][36][37] have also been used to characterize the interaction between different fillers and polymeric matrices.…”

Structural changes in the carbon black network in carbon‐black‐filled styrene‐butadiene rubber samples cured with a two‐step process

“…Polymer nanocomposites are unique materials in that their material properties change substantially with the addition of a small volume fraction of nanometer‐sized filler particles 1–6. The changes are observed when the filler size is comparable to that of the polymer chains and to the average wall‐to‐wall distance between fillers.…”