| 释义 |
preconˈdense, v.
[pre- A. 1.]
trans. To condense (a starting material for a polymer) so as to form a stable, low-molecular-weight intermediate which is convenient to handle and can be fully polymerized at a later stage in a process. Also preˈcondensate [after distillate, filtrate, etc.], an intermediate of this nature. So preconˈdensed ppl. a.
1950R. W. Moncrieff Artificial Fibres xxvii. 261 The formaldehyde and urea are pre-condensed, being allowed to react at room temperature for about five hours until the viscosity is 6 centipoises at 20°C. 1953Jrnl. Soc. Dyers & Colourists LXIX. 44/2 The loss will be further accentuated by differences in molecular size of the precondensate, particularly when highly precondensed resins are used, as in some proprietary products. 1962J. T. Marsh Self-Smoothing Fabrics xi. 159 These pre-condensates are probably methanol ureas which may be formed by condensing urea and formaldehyde either at room temperatures or by refluxing for a short time. 1971S. A. Heap et al.in H. Mark et al. Chem. Aftertreatm. of Textiles vi. 272 There is..a growing tendency for finishers to purchase precondensed ‘resin’ in liquid form. Ibid. 279 The conventional process for the application of urea-formaldehyde precondensates consists of impregnating, drying, curing to bring about resinification, and washing. |