Synthesis of a polyurethane/clay nanocomposite used as coating ...

240 SOLARSKI ET AL.Wide-angle X-ray diffraction (WAXD) at low-angleregionA PU/MMT sample was molded (just after the secondstage of synthesis of PU/MMT) into a plate to give asolid sample (20 20 2 mm thick). These sampleswere used to collect XRD data on a Siemens D500diffractometer (University of Reading, UK), Cu–K radiation ( 1.5406 nm) with a 0.02° 2 step size anda 2-s step time, within the scan range of 1–10°.Figure 3 Curve of titration of the quantity NCO functionsin the IPDI solution.(C 4 H 9 ) 2 NHremaining DBAH hydrochloric acid3 (C 4 H 9 ) 2 NH 2(2)The titration of the remaining DBA was carried out bya pH metric method (pHM210 MeterLab, RadiometerAnalytical, London, UK). The equivalent volume wasgraphically determined according to the classicalmethod of tangents. The pure IPDI and the mixtureIPDI/Cloisite 30B were measured.The second method used was infrared spectroscopy.The measurements were performed with a Nexus 870spectrometer (Nicolet Analytical Instruments, Madison,WI). The samples (mixture IPDI/C30B) wereplaced between two KBr pellets obtained from finelycrushed KBr powder. The sample was then placed inthe spectrophotometer chamber swept by a flow ofdry air. The areas of the different peaks at the initialtime and at the final time were then determined. Theone concerning the NCO peak (2257 cm 1 ) varied, andthis variation was compared with the area of the CH 2peak considered as constant (2600–3030 cm 1 )toobtainthe concentration of IPDI.Thermogravimetric analysis (TGA)TG analyses were performed using a Netzsch STA449C thermobalance (Netzsch-Gerätebau GmbH, Bavaria,Germany) at 10°C/min, from 20 to 1000°C, underflowing air (60 mL/min). Samples ( 10 mg) wereplaced in open platinum pans. The precision on temperaturemeasurements was 0.5°C.RESULTS AND DISCUSSIONAssessment of the IPDI consumed by counterionsof Cloisite 30BBy back titration of NCOThe method by back titration gave an equivalent volumeof 5.3 mL for the pure IPDI (see Fig. 3). Thespecific rate of isocyanate functions was determinedusing the following equation:with%NCO 100 n NCO M NCOm IPDI(3)n NCO p DBA m DBA C a V eM DBA 1000(4)where % NCO is the specific rate of isocyanate functions,that is, the mass percentage of available isocyanatefunctions relative to the mass of analyzed IPDI;Transmission electron microscopy (TEM)TEM images were obtained using a CM 200 microscope(Philips, Eindhoven, The Netherlands) at anaccelerated voltage of 120 kV. Ultrathin sections (80nm) were prepared at 130°C using a UCT ultramicrotomeequipped with an FCS cryochamber (bothfrom Leica Mikrosysteme GmbH, Wetzlar, Germany).Figure 4Reaction between IPDI and a counterion.