Premixed cellulose nanocrystal reinforcement of polyamide 6 for melt processing

Abstract

This work presents a method of industrially viable processing of nanocellulose-reinforced polyamide 6 (PA 6). Cellulose nanocrystal (CNC)reinforced PA 6 is gaining attention as a promising material for use in the automotive industry due to its highly crystalline, low density, and environmentally friendly nature. However, the low-thermal degradation temperature of CNCs presents problems when melt processing at high temperatures, making it difficult to produce the nanocomposite on a large scale. This article presents a methodology of master batching (MB) using planetary ball milling to embed the CNCs in PA 6. The process of MB CNCs with PA 6 to thermally buffer them was compared to direct milling and hand mixing, prior to melt processing with compression molding. The milled composites had final CNC compositions of either 5 or 10 wt%. Through thermal analysis, it was seen that although both milling methods thermally buffered the CNCs, the presence of the low-molecular weight PA 6 in the MB samples resulted in higher thermal stability. In addition to this, the mechanical analysis showed that the MB samples with 5 wt% CNCs had optimum Young's moduli, ultimate tensile strength, and elongation % at break. Overall, the use of milling for MB to coat the CNCs in polymer is a promising alternative to traditional processes and has potential as a method of industrially manufacturing cellulose reinforced polymer composites.

Current international research into cellulose as a functional nanomaterial for advanced applications

“…High shear forces have been used in different ways, in wet and dry feeding processes, to improve dispersion, break cellulose agglomerates, and fibrillate cellulose [316][317][318][319][320]. Suzuki et al [316] fabricated nanocomposites with high cellulose concentrations using a solid-state high-shear process.…”

Influence of Dispersion and Orientation on Polyamide-6 Cellulose Nanocomposites Manufactured through Liquid-Assisted Extrusion

“…The addition of MMT (4.7 wt.%) resulted in an increase in the tensile strength of these composites from 69 to 97 MPa and in their tensile modulus from 1.1 to 1.9 GPa. The use of cellulose nanocrystals (CNCs) [ 8 , 9 , 10 , 11 , 12 ] and cellulose nanofibers (CNFs) [ 8 , 13 , 14 , 15 ] as reinforcements for polymer composites have also been studied in PA6.…”

“…The main challenge in their processing is associated with an effective dispersion and distribution of the cellulose nanomaterials in the polymer matrix, owing to their tendency to agglomerate and their thermal instability at temperatures above 200 °C [ 16 ]. To overcome these challenges, high-energy processes [ 11 , 13 ], and chemical modifications [ 12 , 15 , 16 ] have been used. For example, ball-milling and cryo-milling [ 11 ] were used to produce the polymer and cellulose in powder form to facilitate the mixing and dispersion of cellulose with PA6.…”

“…To overcome these challenges, high-energy processes [ 11 , 13 ], and chemical modifications [ 12 , 15 , 16 ] have been used. For example, ball-milling and cryo-milling [ 11 ] were used to produce the polymer and cellulose in powder form to facilitate the mixing and dispersion of cellulose with PA6. However, these processes are time- and energy-intensive, rendering the large-scale production difficult.…”

“…This type of process is useful on a laboratory scale but is not environmentally friendly or scalable. Most of the reported studies have used dried NC in PA6 [ 8 , 11 , 13 , 14 , 15 , 16 , 17 ], at rather high concentrations [ 13 , 14 ]. However, even if NC is well distributed in the polymer phase, it is not dispersed at the nanoscale.…”