Recyclable polyurethane/nanoclay films

Abstract

A series of polyurethane (PU)/clay nanocomposite films was prepared by adding natural bentonite Cloisite ® Na + powders to waterborne polyurethane dispersions (PUDs) followed by a slow water evaporation; the nanoclay content in the films varied from 0 to 5 wt%. The functional properties of materials with low nanoclay loading (up to 1 wt%) resemble features of films prepared without any nanoclay. Compared to unfilled PU, the films with 3 and 5 wt% nanoclay concentrations exhibited slightly deteriorated properties. This phenomenon can be caused by the fact that the polymer-filler interactions are negligible. Gas transport properties are the exception: nanoclay was found to be an efficient barrier component for the permeability of industrially important gases (O 2 , N 2 , H 2 , CO 2 , and CH 4 ). All films feature thermoplastic characteristics and thermal stabilities up to at least 200 C. Because PUDs are solely composed of linear chains, the possibility of preparing recyclable materials was tested. While PU can be re-used after dissolving in acetone and re-dispersing in water, the re-use of nanoclay is not recommended. Preliminary accelerated in vivo tests performed in 20% H 2 O 2 and 0.1M CoCl 2 at 37 C detected substantial susceptibility to biodegradation, especially for films containing 5 wt% nanoclay. POLYM. COMPOS., 40:4079-4092, 2019.

Novel waterborne poly(urethane‐urea)/silica nanocomposites

“…[ 38 ] To distinguish different constitutions of polymer nanoparticles, the products with isocyanate excess higher than 1.05 are designated as poly(urethane‐urea), PUU dispersions. PUDs have been studied recently [ 32–36 ] were prepared at an isocyanate ratio equal to 1.05 and they are constituted from solely linear PU chains.…”

“…The spherulites were recently clearly visible in the PU film and in PU/clay nanocomposites being formed from merely linear PU chains. [ 36 ] In this case, the supramolecular ordering is efficient, even though the high degree of branching/crosslinking in PUU nanoparticles is set (given by 40 mol% excess of isocyanates over hydroxyl groups). On the other hand, no spherulites were detected in the nanocomposites, even at 5 wt% nanosilica.…”

“…Recently, we prepared a series of polycarbonate‐based waterborne PU dispersions composed of solely linear PU chains [ 32,33 ] followed by nanocomposite preparation. [ 34–36 ] These PU films and nanocomposites are fully recyclable, [ 32,36 ] but their mechanical properties are limited. [ 32,34–36 ] Later, a series of PU films made from waterborne dispersions having variable excess of isocyanate in the synthesis protocol was prepared and characterized.…”

“…[ 34–36 ] These PU films and nanocomposites are fully recyclable, [ 32,36 ] but their mechanical properties are limited. [ 32,34–36 ] Later, a series of PU films made from waterborne dispersions having variable excess of isocyanate in the synthesis protocol was prepared and characterized. A simplified preparation compared to the classic acetone method was used.…”

“…[ 37–39 ] Waterborne PU particles consisting of differently branched/crosslinked PU chains were formed. [ 40,41 ] It was found that substantially better mechanical properties can be achieved compared to recyclable films [ 32,36 ] ; the optimal excess of isocyanate over hydroxyls is 30 to 40 mol%. Hence, the preparation protocol [ 41 ] with 40 mol% isocyanate excess was used for the preparation of waterborne PU dispersions in this study.…”