Stone protection quality indicators and precautions
The protective agent is defined in "Natural Stone Protective Agent for Architectural Decoration" (JC/T973-2005). The main component can be organically combined with natural stone, and there is no obvious change in the appearance of the stone, effectively reducing the water absorption rate of the stone and obviously improving the stone resistance. Stain performance, a solution that is relatively stable under acid-base conditions. According to the above definition, the role of stone protectant is to effectively reduce the water absorption rate of the stone and significantly improve the anti-pollution ability of the stone. It is important to prevent the disease and weathering and reduce the complicated daily maintenance workload. The quality indicators are also fully reflected in the definition: the main components are organically combined with the stone; the effect is relatively stable under acid-base conditions. The significance of these regulations is to emphasize the long-term and stable use of stone protectants.
First, the quality indicators
1. The main body and active ingredients of stone protectant
As a mature technology and product, stone protection and protective agent has been used in stone for a long period of continuous development and improvement. In today's era of new technologies and new materials, almost all the technologies and materials that can be cited are reflected in them. Simply put, the main components of various stone protectants can be divided into two parts, one of which is an active substance, which plays a functional role in the stone protective agent, and its quality only accounts for 5%-l5% of the total mass. The second is a solvent, which functions to dissolve the former and then act as a medium to feed the active agent in the protective agent into the interior of the stone.
There is no doubt that these actives play a key role in stone protectants. It has been proved that silicone polymer is an ideal and relatively perfect stone protection material. It has good water resistance and water repellency, stable performance, good chemical resistance, ideal molecular size and structure, and organic formation with stone. Combine. Most of the current stone protectants on the market are based on organic polymers. If the formulation of these active ingredients is scientifically reasonable, these protective agents should have such characteristics: good water resistance, acid and alkali conditions. The effect is stable, the permeability is good, and it is organically combined with stone. Of course, because the formulation of the protective agent involves many factors such as technology and cost, the performance of each of the various types of protective agents will be different, and these differences are mainly reflected in the intrinsic quality indicators of some products.
The use of silicone polymers as active materials for stone protectants also has its own drawbacks. Its performance in oil resistance is poor. With the gradual maturity of fluorine chemical and fluorine materials technology, organic fluoropolymers are also used in the field of stone protection. Its excellent oil and stain resistance and chemical resistance make the performance of stone protectants relatively perfect. But its waterproof performance is far less than that of silicone polymers. Therefore, the combination of organic fluorine and silicone is often used, so that the stone protectant has both ideal waterproof performance and ideal antifouling performance. Therefore, we can distinguish the protective function of the product by confirming the active ingredients of the stone protectant: the waterproof property of the silicone product is better, the antifouling performance of the organic fluorine product is better, and the waterproofing and antifouling of the organic fluorosilicon product are comprehensive. Good performance. Of course, not all silicone and organofluorine stone protective products have the same performance, and it has a great relationship with the type and performance and content of the specific organic fluorine and silicone polymers.
2. Waterproofing of stone protectant
This is a basic indicator for expressing the performance of stone protectants. It indicates the waterproof ability of stone protectants, indicating the extent to which the stone protectant is applied to the stone to change the water absorption rate of the stone, usually expressed by water resistance. Water resistance = (water absorption rate of stone before protection - water absorption rate of stone after protection) / water absorption rate of stone before protection X l00%. The higher the indicator, the better the waterproof performance of the protective agent. From the existing materials and technology, the water resistance index should be better at 90% to 80%. Of course, since the stone is a gas permeable material, and the structural density of the stone varies greatly, it is unrealistic to achieve water repellency of 100%.
3. The alkali resistance of stone protectants
This is one of the key indicators for expressing the intrinsic quality of stone protectants. It indicates that the protective agent can resist the destruction of alkaline substances after being applied to the stone, that is, the stability of the performance of the stone protectant under alkaline conditions. Usually expressed in alkali resistance. Alkali resistance = (water absorption rate of stone before protection - water absorption rate of stone in alkaline solution after protection) / water absorption rate of stone before protection × 100%. The higher the index, the better the alkali resistance of the protectant. The stability of the active agent in the stone protectant is different when it encounters the destruction of the alkaline substance, and the strong alkalinity exhibited by the cement after the wet storage of the stone is long-term, so this indicator becomes the protection of the ground stone. An important sign of the agent. The smaller the difference between the waterproofness and alkali resistance of the stone, the more stable the performance of the protective agent under alkaline conditions, the better the protective effect, and the longer the effect is maintained.
4. Acid resistance of stone protectants
This is one of the key indicators for expressing the intrinsic quality of stone protectants. It indicates the ability of the protective agent to resist the destruction of acidic substances after being applied to the stone, usually expressed by acid resistance. Acid resistance = (water absorption rate of stone before protection - water absorption rate of stone in acidic solution after protection) / water absorption rate of stone before protection × 100%. The higher the index, the better the acid resistance of the protectant. The stability of the active agent in the stone protectant is different when it encounters the destruction of the acidic substance, and the damage of the acid rain is long-term when the stone is applied to the outer wall surface of the building, and most of the cleaning agents used in the cleaning construction are also It is strongly acidic, so this indicator has become an important symbol for the selection of exterior wall stone protectants. The smaller the difference between the waterproofness and acid resistance of the stone, the more stable the performance of the protective agent under acidic conditions, the better the protective effect, and the longer the effect is maintained.
5. Penetration of stone protectant
This is one of the key indicators for expressing the intrinsic quality of stone protectants. It indicates the ability of the protective agent to be applied to the stone and the active substance is immersed in the surface of the stone. It is very intuitive to test this indicator. It is to apply the protective agent twice on the stone surface to be treated. After 24 hours, the stone is broken and the section is placed in the water. The depth of the surface layer is not the color of the protective agent. Permeability. The higher the index, the better the penetration of the protective agent, and the better the resistance of the protective layer to abrasion and scrubbing, the longer the effect. The higher the content of the active substance in the protective agent, the more the number of coating passes, the stronger the permeability is exhibited. Relatively speaking, the water-soluble protective agent will have poor permeability.
Second, matters needing attention
With the development of stone conservation engineering practice, the maintenance technology is greatly enriched. Conservation theory is also emerging. Various theories are based on the analysis and answering of various problems and phenomena in the practice of conservation, which have their rationality and applicability, as well as their one-sidedness and restriction. In the recent practice of stone conservation, some new problems have emerged, and some new ideas have been formed, which are summarized as follows.
First, the stone protection should be tailored to the material, and the construction of the material in the engineering practice will find that the protective agent has poor protection effect on some varieties of stone. Excluding improper construction and product failure, the most likely cause is that the correct stone chemicals are not used for protection. For example, granite and marble have different formulations of protective agents because of their different mineral composition and chemical composition. Even the same type of stone will increase or decrease the concentration of silicone resin due to differences in density and chemical composition. For example, the concentration of silicone resin in sandstone protectants will be higher, and the concentration of silicone resin in granite or marble protectants with higher hardness and density will be lower. Therefore, in the construction of stone conservation, it must be adapted to the material, and it must be constructed according to the material. Different chemicals and different construction techniques are selected for different stone materials.
Second, not all natural stone needs protection. If it is only waterproof and alkali-proof, some high-hardness and high-density stone in dry hanging construction can not be protected. This also applies to some coarse-grained granite. For example, in the igneous rock, the coarse-grained magmatic rock obtained by slow cooling has a large amount of quartz, and these very dense quartz surface water and other pollutants are infiltrated. The theory was confirmed and recognized by Maurizi0, a conservation expert of the American International Stone Association. Which stone needs to be protected from which stone? The test method is to drip water on the polishing surface of marble or to drop vinegar on the polished surface of granite. If the residue of anhydrous or vinegar remains after 5 minutes, the marble or granite of this variety may not be Do protection. This is basically the case with the “Hua’an Jade†marble from Fujian.
Third, the natural stone floor paving does not need to use smooth stone, after the roughening of the rough surface, and then the artificial maintenance of the current floor pavement is to choose the smooth surface of the smooth pavement, and then find a flat renovation, equal to repeat The polishing process has a high cost. The correct way is to choose the smooth surface of the stone, then buy the matte specification board, and then paving, leveling, refurbishing and curing. This can greatly reduce costs. This method has long been used in engineering practice in foreign countries, and has not yet formed an application in China, mainly because of the disconnection between stone consumers and construction companies, which is inconsistent in concept. The high cost is entirely borne by the consumer.
Although there are many advantages, this method is generally only suitable for granite stones with small color difference and no texture. For many textured marbles, because there is a typographic problem, it should be done by traditional methods. Then proceed with the construction.
Because the interior decoration stone is not affected by sunlight, wind, acid rain, fog and snow, the protective effect lasts longer. The impact on the service life of protective chemicals is relatively small. From the perspective of reducing indoor decoration decoration pollution and reducing the version of Chen, it is possible to use an inexpensive water-based protective agent. Solvent-based protectants are recommended for use in destructive environments such as kitchens and baths.
Fourth, rust spots and vomiting yellow should be separated, can not be simply used rust remover treatment Many times the yellow spots appearing in the stone is mistaken for rust spots. The rust spots contain iron and can be removed with a rust remover. There are two common causes of macular, which are easily confused with rust spots. One is that when the stone is wet-laid and filled, the organic additive in the cement penetrates into the surface through the capillary pores on the bottom surface, and the double bond of the organic component breaks under the condition of water and oxygen, and the color turns yellow. This situation is more common in wet-laid and filled white hemp stone. In another case, in the beige marble, the alkali plaque spreads to the surface to absorb the crystal water to produce a gel layer. After changing the light refraction, the alkali spot color becomes darker, which seems to be "yellower", but actually contains crystal water. The gel layer is at work. Therefore, the yellow spots of these genesis cannot be solved simply by using a rust remover. It is necessary to prescribe the right medicine, otherwise it will probably be worse.
5. Don't blindly believe in imported stone conservation products, and don't prejudice domestically produced products. At present, the maintenance products of foreign brands are generally considered to be a symbol of high quality. However, its high price affects the promotion of foreign brands. The maintenance products of domestic brands are generally not optimistic, but they also have a certain market share because of their low prices.
In fact, these prejudices stem from the lack of understanding of stone conservation knowledge. All protective agents, whether imported or domestically produced, are composed of active ingredients plus diluents and auxiliaries. There is no difference between imported and domestically produced. In recent years, the development and application of domestic stone protectant products have developed rapidly, and it has approached the advanced level in foreign countries in the field of silicone monomer manufacturing and resin synthesis.
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