| 摘要 |
Surfaces such as newly laid concrete, bitumen, or farmland containing growing or fully grown crops are protected against adverse weather conditions by the application of two layers of flexible sheeting with a layer of foamed thermoset resin therebetween, especially urea-formaldehyde resin, this foamed resin being positioned in discrete areas such that the sheets are held apart but the void between them is incompletely filled. The foam may be formed in a series of separate deposits or in continuous or discontinuous lines. Usually, a maximum of 50% of the area of the sheets contacts the foam, a maximum of 30% being preferred. An apparatus for applying the insulating means comprises a frame (21) upon which are mounted two rolls (27, 28) of the sheeting and, between these rolls, an outlet (32) for the foamed or foaming thermosetting resin. |
