Abstract
With the assistance of different solvents, self-crosslinked acetic acid lignin-containing polyurethane (LPU) membranes were synthesized. Compared with tetrahydrofuran and dioxane, N, N-dimethylacetamide with stronger polarity together with higher boiling point was demonstrated to be beneficial for preparing LPU particles of smaller size and enhanced binding force. It was also found that lignin domain can interpenetrate into polyurethane domain well with 43.3% lignin addition, resulting in enhanced phase mixing and better performance. In addition, relative homogeneous and smooth LPU membrane can be obtained with 2% TMP addition, while stress crack took place when TMP content was greater than 3%.
Highlights
The utilization of renewable biomass resources in polymer has received increased attention due to their potential for substitution of petrochemical derivatives [1] [2]
The following reagents were used without further purification: methylene diphenyl diisocyanate (MDI), polyethylene glycol (PEG), trimethylolpropane (TMP), N, N-dimethylacetamide (DMAc); acetic acid, HCl, dioxane, diethyl ether, all of which were from Aldrich Chemicals; the acetic acid lignin (AL) was prepared in our laboratory
This is because PEG was added into the system, so that the lignin hard segment was well dispersed into the soft segment and formed smaller domains
Summary
The utilization of renewable biomass resources in polymer has received increased attention due to their potential for substitution of petrochemical derivatives [1] [2]. PU films prepared from the ethanol lignin ( known as Alcell lignin) and 4, 4’-diphenyl methane diisocyanate (MDI) by solution casting were very brittle [21], similar results were obtained by others [22] This can be attributed to the aromatic nature of the hard segments of lignin and MDI, and the crosslinked structure. The literature so far has focused on modification and properties of lignin-containing polyurethane, and most of them were carried out on ethanol-(Alcell) lignin, limited publications were available on the acetic acid lignin (AL) [31]-[34]. We introduced AL as a renewable resource to prepare PU and determined the influence of solvent, AL and TMP content on the microstructure, phase behavior, mechanical properties and water resistance of the resulting lignin-containing polyurethane (LPU) membranes. Various complementary analytical techniques, such as Environmental Scanning electron microscope (ESEM), Dynamic mechanical analysis (DMA) and X-ray photoelectron spectroscopy (XPS) were used
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