Physical and thermal properties of thermoplastic poly(azo-urethane)s

New thermoplastic segmented poly(azo-urethane)s (PAUs) have been synthesized by one-step polycondensation from aromatic diazo-diol, ( E)-1-(4-(4-(3-hydroxypyridyl-azo)thiocarbamoylaminobenzyl)-phenyl)-3-(3-hydroxypyridylazo)thiourea, as chain extenders, phenylene diisocyanate and 20–60 mol % polyethylene glycol (PEG) with the molecular weight of 2000 g/mol. The effect of diazo-diol used in the structure and some physicochemical, thermal and mechanical properties of the segmented polyurethanes were studied. The structure was examined by proton nuclear magnetic resonance (1H NMR) and Fourier-transform infrared spectroscopy (FTIR) analyses. Polyazos were the products with good processability and high molar mass in the range 120 × 103–135 × 103 g/mol. Thermal properties, investigated by thermogravimetric analysis and differential scanning calorimetry indicated that PAUs up to 40 mol % polyol were fairly stable above 530°C, having initial weight loss of around 528–539°C, 10% gravimetric loss in the range 553–567°C and own high glass transition temperature 259–264°C. The polymers also demonstrated higher tensile strength (56.53–63.83 MPa) and elongation at break (1.58–1.63). However, compared with typical polyurethanes, PAUs with lower polyol content displayed higher Tgs, heat and mechanical stability owing to warily designed rigid hard segment structure.

An investigation on new high performance Schiff base polyurethanes

Novel poly(urethane-azomethine-thiourea)s (PUATs) were synthesized via one-step polymerization from newly prepared diol chain extender (1,4-phenylene bis((E)-1-(4-hydroxobenzylidene)thiourea) (PBHBT)), containing C=S and –C=N– linkages, along with 1,4-phenylene diisocyanate (PDI) as hard segments and 20, 40 and 60 mol.% polyethylene glycol (PEG) forming soft segments. The prepared chain extender and polymers were characterized via elemental, Fourier transform infrared, 1H- and 13C-NMR analyses, and physical properties such as ηinh, solubility, crystallinity, flame retardancy and thermal stability were studied. According to X-ray diffraction patterns, the Schiff base polymers exhibited amorphous morphologies and their molar masses were in the range of 148 × 103–163 × 103 g mol−1. Thermogravimetric analysis indicated that PUATs with 20 and 40 mol.% PEG were fairly stable above 500°C having T10 of 511–527°C and had high glass transition temperatures about 249–251°C. In comparison with typical polyurethanes, PUATs with lower polyol content exhibited better non-inflammability, Tg values, chemical and thermal stability owing to rigid hard segment structure.

A high strength nanocomposite based on microcrystalline cellulose and polyurethane

A high-strength elastomeric nanocomposite has successfully been prepared by dispersing microcrystalline cellulose in a polyurethane matrix. The resulting nanocomposites show increased strain-to-failure in addition to increased stiffness and strength compared to the unfilled polyurethane. The optimal composite contained 5 wt % cellulose. The average true strength for this composition was 257 MPa, compared with 39 MPa for the neat polyurethane, and showed the highest strain-to-failure. The improvements of stiffness, strength, as well as strain-to-failure are believed to be due to good interaction, by both covalent and hydrogen bonds, between the polyurethane and the cellulose nanofibrils.