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COATINGS & LININGS TABLE 1
Different conditions for reaction Polymer
WPUR
WPUR-1 WPUR-2 WPUR-4
MCC (g) 0
1.48 1.48 1.48
None
Together with DMBA Together with DMBA
Together with polyether polyol
TABLE 2
–NCO content at different stages Polymer
–NCO Content (%) at End of First Stage
WPUR
WPUR-1 WPUR-2 WPUR-3
Polyether Polyol 220†
(9.89) 6.68 (6.78) (9.89) 6.68 (6.78) (9.89) 6.68 (6.78) (6.72) 6.33 (5.83)
was dehydrated in
a vacuum at 105 °C for ~45 min before being used. The size and degree of po- lymerization for MCC is 60 and 230 µm, respectively. Dimethylol butanoic acid (DMBA) was placed in the oven at 105 °C. Triethylamine (TEA) and ethyl- enediamine (EDA) were distilled onto molecular sieves before use. Acetone, toluene, and dibutylamine were all used _Q\PW]\ N]Z\PMZ X]ZQÅKI\QWV
Characterization We determined the isocyano
(–NCO) content by chemical titration19 and measured the zeta potential and the size of WPUR emulsion. The measure- ment range (diameter) was from 10 to 100 nm, so the emulsion should be di- luted by distilled water. The Fourier transform infrared (FTIR) spectra were recorded over the range from 4,000 to 700 cm–1
†Trade name. 36 MATERIALS PERFORMANCE April 2012
–NCO Content (%) at End of Second Stage
(6.33) 2.98 (3.10) (3.07) 2.67 (2.24) (3.07) 2.54 (2.24) (3.07) 2.40 (2.24)
temperature to 100 °C. Three minutes later, the temperature was reduced to –50 °C and then increased to 120 °C at a heating rate of 10 °C/min. The sample mass was from 3 to 10 mg. The me- KPIVQKIT XZWXMZ\a WN \PM ?8=: ÅTU[ was measured by the Universal testing machine CMT4204†
vacuum for ~30 min. The mass (Wo
after drying in a ) was
measured and the sample immersed in distilled water for 24 h. Then the mass was again measured (Wt
). The water
absorption (WU) was calculated: WU (%) = (Wt
– Wo )/Wo × 100% (1)
Preparation of WPUR Films First, the polyether polyol (108 g, UWT _I[ ILLML \W I ÆI[S NWTTW_ML
by DMBA (9 g, 0.061 mol), acetone (30 g, 0.517 mol), and then TEA (4.9 g, 0.049 mol) as a neutralizer. The reaction continued for 30 min. The solution was then diluted in distilled water (200 mL) IVL MU]T[QÅML
Moment of Adding MCC
Hydrophilic
Cross-Linking (h) 2 2 3 2
Results and Discussion
Measuring –NCO Content There are many methods for deter- mining the –NCO content.12
Here we
determined the –NCO content by chem- QKIT \Q\ZI\QWV I\ \PM ÅZ[\ IVL [MKWVL [\IOM of reaction. Table 2 shows the results. Data in parentheses represent the theo- retical value calculations.
Zeta Potential and Size Analysis
As the number of hydrophilic groups
increases, the molecular chain is much more hydrophilic, causing the dispersion of particles more easily. Therefore, with more hydrophilic groups, the size of the particles will become small, which is conducive to the stability of emulsion. In the process of emulsion, the hydrophobic segment forms the core of particles. On the interface of the particles, associative ions split and then form a two-electron [PMTT )VQWV[ IZM Å`ML WV \PM [SMTM\WV WN the WPUR chains while counter ions migrate to the surrounding water, form- ing a charge layer (zeta potential). If the zeta potential value is >30 mV, the emul- sion system is considered stable.20
Figure
1 shows zeta potential values. The WPUR-3 emulsion was the worst in sta- bility, with the minimum zeta potential IVL \PM UI`QU]U XIZ\QKTM [QbM
Chemical Structural Analysis The chemical composition of WPUR
films was identified using FTIR. The FTIR showed no major chemical struc- \]ZIT KPIVOM[ QV \PM UWLQÅML ?8=:
Thermal Characterization of WPUR Films
Thermal stability tests (Figure 2)
showed that MCC had a better thermal [\IJQTQ\a \PIV \PM ?8=: ÅTU[ )LLQVO 5++ QVKZMI[ML \PM \QUM WN KZW[[ TQVSQVO reaction, which was also good for improv-
NACE International, Vol. 51, No. 4
5QKZWKZa[\ITTQVM +MTT]TW[M 5WLQÅML ?I\MZJWZVM 8WTa]ZM\PIVM