化学保护的副作用及其对策的探索性研究:(Ⅰ)多层化学保护

化学防护和化学加固是目前保护土、石、砖等材质的不可移动文物的常用方法.所用化学材料主要是有机硅等憎水性有机化合物.这些材料能起到一定的防水和加固作用,但也存在不少问题,有的导致了更严重的破坏.其中,憎水性保护层的起壳剥落是最常见的破坏现象,特别当环境干湿循环频繁,文物本体或地下可溶性盐含量较高的情况下,憎水性化学保护层很容易从文物本体上起壳剥落,造成文物的加速腐蚀破坏.为了减小此类破坏的危害程度,本工作探讨了化学保护剂在混合使用和多层配合使用条件下的防护和加固效果.结果发现,以憎水性较弱的化学材料做基底渗透,以憎水性较强的化学材料做表而保护,由此构成的多层保护措施可以降低化学保护层起壳剥落的危害.其主要原因是,多层保护形成的憎水梯度分散了吸湿膨胀形成的界面拉应力,也缓解了盐结晶析出产生的膨胀应力.

The multilayer chemical protection on the surface of historic relic

Chemical protection is one of the common used methods that protect and reinforce the historic relic being in severe danger,especially for the site composed of soil,stone and brick,etc in open environment.At present,the primary chemistry materials that have been tried for site protection are organic silicon compound and fluorine containing polymers,etc.These organic materials can play a certain role in the protection,but there are various defects.The soil,stone and brick are hydrophilic,and organic protecting materials are hydropholic. The frequent stress change on the interface of hydrophilic hydropholic makes protection layer desquamation.In this work,a multilayer chemical protection method that structured by hydrophilic external layer and hydropholic fundus layer was proposed and tested.Alkoxysilanes and fluoro rubber solution were selected as the external layer material,and polyacrylate and polyethylene glycol as the fundus layer material.From the experiments of decaying cycles that destructive factors such as moisture cycles,salt crystal,frost and fusion were included.It was found that the multilayer protection method obviously reduced the danger of interface breakage.Because there is a transition layer between hydropholic external layer and hydropholic relic materials that dispersed the stress of hydroscopic expantion strain and salt crystallize dilatant near interface.