How to modify the surface of nano-zinc oxide?
Nano-zinc oxide is a new type of functional fine inorganic chemical material. Due to its small particle size and large specific surface area, it has unique physical and chemical properties in chemical, optical, biological and electrical aspects. It is widely used in antibacterial additives, catalysts, rubber , dyes, inks, coatings, glass, piezoelectric ceramics, optoelectronics and daily chemicals, etc., the development and utilization of broad prospects.
However, due to the large specific surface area and specific surface energy of nano-zinc oxide, the surface polarity is strong, and it is easy to agglomerate; it is not easy to disperse uniformly in organic media, which greatly limits its nano-effect. Therefore, the dispersion and surface modification of nano-zinc oxide powder has become a necessary treatment method before nano-materials are applied in the matrix.
1. Surface coating modification of nano-zinc oxide
This is the main surface modification method of inorganic fillers or pigments at present. Surfactant is used to cover the surface of particles to give new properties to the surface of particles. Commonly used surface modifiers include silane coupling agent, titanate coupling agent, stearic acid, silicone, etc.
2. Mechanochemical modification of nano-zinc oxide
This is a method of using pulverization, friction and other methods to activate the particle surface with mechanical stress to change its surface crystal structure and physicochemical structure. In this method, the molecular lattice is displaced, the internal energy is increased, and the active powder surface reacts and attaches to other substances under the action of external force, so as to achieve the purpose of surface modification.
3. Nano-zinc oxide precipitation reaction modification
The method uses organic or inorganic substances to deposit a layer of coating on the surface of particles to change their surface properties.
At present, some breakthroughs have been made in the preparation technology of nano-zinc oxide, and several industrialized manufacturers have been formed in China. However, the surface modification technology and application technology of nano-zinc oxide have not been paid much attention, and the development of its application field has been greatly restricted. Therefore, it is necessary to strengthen the research on the surface modification and application of nano-zinc oxide products, develop high-performance products, and broaden the application fields of products to meet the demand for nano-zinc oxide products in different fields.
Application of 7 categories of nano-powder materials in liquid silicone rubber
Liquid silicone rubber is mainly composed of basic polymers, reinforcing fillers, cross-linking agents and various auxiliaries in a certain proportion to prepare a base rubber with self-leveling and thixotropy, and then mix it with air at room temperature or under heating conditions. Elastomers formed by contact with moisture in or with cross-linking agents.
Because the physical and mechanical properties of pure liquid silicone rubber are very poor, it generally needs to be reinforced and modified to meet the needs of practical applications. Among them, adding reinforcing fillers is undoubtedly the most concise and convenient method. Commonly used nano-fillers are nano-silica, nano-calcium carbonate, organic montmorillonite, carbon nanotubes and graphene, nano-zinc oxide, nano-titanium dioxide, silicon carbide, aluminum oxide and nano-silver wires.
1. Nano silica
The synthesis methods of nano-silica are mainly based on gas phase method and precipitation method. Nano-silica prepared by gas phase method has few surface hydroxyl groups, uniform particle size and good dispersibility. Zhu Zhimin et al. used fumed silica as a reinforcing filler and found that after adding 10 parts of silica, the physical and mechanical properties of liquid silicone rubber were significantly improved, and the Shore A hardness, tensile strength and shear strength could reach 40, respectively. , 1.6MPa, 1.4MPa; there is no significant change in shear strength after aging.
Due to the higher cost of fumed silica, the lower cost precipitated silica is of interest. The water content of the precipitated silica is higher, and the surface hydroxyl number is much higher than that of the fumed silica, which makes the surface activity of the precipitated silica very high, and it is easy to agglomerate, which is not conducive to dispersion in the rubber matrix. In order to solve this problem, physical or chemical methods are usually used to modify its surface to prevent the occurrence of agglomeration and improve its dispersibility.
2. Nano calcium carbonate
Nano calcium carbonate has the advantages of small particle size, high specific surface area, high surface activity, large filling amount and convenient processing. , Nano calcium carbonate is widely used in liquid silicone rubber as a common reinforcing filler.
3. Organic Montmorillonite (OMMT)
Montmorillonite (MMT) is a typical layered silicate and is a relatively common reinforcing filler in the rubber industry. In order to improve the compatibility of MMT with silicone rubber, it is usually organically modified to obtain OMMT. The study found that OMMT can be well dispersed in the silicone rubber matrix, thereby greatly improving the physical and mechanical properties of the silicone rubber.
4. Carbon Nanotubes (CNTs)
Due to the large aspect ratio, high modulus, extremely high toughness and low density of CNTs, they have always attracted attention, so the research of CNTs in the field of liquid silicone rubber reinforcement has become more and more extensive.
5. Graphene
Graphene is a kind of two-dimensional nanomaterial with hexagonal lattice arrangement formed by sp2 carbon atom hybridization. It has excellent electrical, thermal and physical and mechanical properties, and has stable performance, wide sources and simple preparation. , is a very ideal functional filler.
6. Nano zinc oxide
ZnO is a commonly used vulcanization activator in the rubber industry, and can also be used as a filler to improve the physical and mechanical properties and thermal conductivity of materials.
In theory, reducing the particle size of ZnO and increasing the specific surface area are beneficial to improve the reactivity, so nano-ZnO can be used as a functional reinforcing filler for liquid silicone rubber. In addition, ZnO is also a good UV shielding agent with anti-aging properties. The modified ZnO can also impart new properties to silicone rubber such as self-cleaning properties.
7. Nano titanium dioxide
Nano-titanium dioxide has the characteristics of less surface defects, more unpaired atoms, and large specific surface area. When it is used to strengthen rubber, it is prone to physical or chemical bonding and increases cross-linking sites, which is beneficial to improve the physical and mechanical properties of rubber materials. After being subjected to external force in the stress field, nano-titanium dioxide produces micro-domain deformation in the matrix to absorb energy, and the rubber material exhibits good radiation resistance.
Other functional reinforcing fillers In addition to the above-mentioned functional nano-reinforced fillers, there are many other types of reinforcing fillers, such as silicon carbide, alumina, nano-silver wires, etc. These reinforcing fillers can not only effectively improve the physical properties of liquid silicone rubber. Mechanical properties can also impart some special properties.
Due to the high demand in the high-end field, the status of synthetic mica has been further improved
Pearlescent pigments in the field of new materials belong to a national strategic emerging industry. Synthetic mica is an important substrate for pearlescent materials. With the increase in downstream demand, the increase in the share of synthetic mica-based pearlescent pigments is becoming one of the future trends.
Pearlescent pigment, which is formed by coating a layer of oxide film (coating layer) on a substrate such as mica, is a high-grade pigment that subverts traditional pigments. It has excellent characteristics such as safety and environmental protection, non-fading, and rich colors. Mica is divided into natural mica and synthetic mica. Natural mica-based pearlescent pigments have low cost and are mainly used in low-end manufacturing; synthetic mica-based pearlescent pigments are expensive and are mainly used in high-end manufacturing, automobiles and cosmetics and other high-end fields.
Natural mica is a naturally formed rock-forming mineral, which is a non-renewable resource. With the exhaustion of natural mica resources, the production capacity is greatly restricted; while synthetic mica simulates the composition and structure of natural mica, and is artificially synthesized with minerals, with fewer impurities. It is superior to natural mica in terms of use temperature, insulation, safety and environmental protection, and color. The demand for synthetic mica in high-end fields such as cosmetics and automobiles continues to increase under the upgrading of consumption. Therefore, the market scale of synthetic mica continues to expand and the penetration rate increases. It is gradually replacing natural mica and becoming the main base material for pearlescent pigments.
Because of its excellent characteristics, synthetic mica pearlescent materials are widely used in downstream applications, not only widely used in popular high-end fields such as cosmetics and automobiles, but also favored by consumers. In the industrial field, it is also known as "industrial monosodium glutamate", which can be widely used in coatings, plastics, rubber, papermaking, building materials, metallurgy and other industries. For example, in coatings, synthetic mica powder is used in cars and architectural decoration coatings; in the rubber industry, synthetic mica powder is a good lubricant and mold release agent; in reinforced plastics, synthetic mica powder can be used as raw materials for plastic production. The additives are used to make modern engineering plastics with high strength, good elasticity and light weight; among insulating materials, synthetic mica paper series products are the most widely used electrical insulating materials.
Application and characteristics of talcum powder in food grade grease
Food safety has always been the focus of people's attention. There are many factors affecting food safety. Among them, the pollution caused by the leakage of lubricating materials in food equipment is one of the important reasons. Food-grade grease is widely used in key transmission parts of food processing equipment such as bearings, chains and guide rails, and the lubricating performance of grease mainly depends on the additives used.
In view of the safety of food-grade grease, when selecting additives, non-toxic and harmless are the primary considerations. As a food additive, food-grade talc is often used in food flow aids and mold release; because of its good lubricating properties, it also has certain applications in the field of tribology, such as coating talc on protective clothing. Reduce the skin damage of medical staff during COVID-19; in addition, talc in lubricating oil has excellent anti-friction properties, which can better reduce the wear of cast iron equipment.
The composite aluminum base grease was prepared by white oil and thickener, and the effect of food grade talc mass fraction on the tribological properties of the grease was investigated. The results show that:
(1) Talc powder can improve the thermal stability of composite aluminum-based grease, and the epitaxial decomposition temperature of base grease is significantly lower than that of grease containing talc powder;
(2) Talc powder can improve the tribological properties of composite aluminum-based grease, that is, improve the stability of the friction process, reduce the friction coefficient and wear volume; with the increase of the mass fraction of talc powder, the friction coefficient and wear volume experience a first The change increases after the decrease, and when the mass fraction of talc is 1.0%, the average friction coefficient and wear volume are the smallest; Polishing plays an effective anti-friction and anti-wear effect;
(3) Greases with 1.0% talc added are most likely to be applied to food equipment and other fields.
(4) Talc powder is a layered silicate, which can be adsorbed on the surface of the friction pair during the friction process, which is equivalent to a "sliding bearing" for sliding, so as to reduce friction and reduce wear.
(5) From the point of view of the thermal stability of the grease, when the final degradation temperature is reached, the residual weight of the grease sample containing talc powder is higher than that of the base grease. This is because the main components of talc powder are MgO and SiO2, of which the heat of Good stability, can improve its thermal stability. Since a lot of heat is easily generated during the friction process, SiO2 with better thermal stability tends to stay in the gap of the friction pair. Due to the surface roughness of the steel plate, the real contact area between the steel ball and the steel plate is small, and it is subjected to high contact stress in the early stage of the friction process, which is prone to large friction and ravines on the surface of the wear scar. Therefore, some talcum powder (mainly SiO2) can repair the grooves generated on the surface of the wear scar during the friction process, thereby increasing the contact area between the friction pairs and reducing the contact stress between the friction pairs; at the same time, SiO2 is a commonly used polishing material, so a small amount of SiO2 can A micro-polishing effect is produced on the surface of the friction pair, thereby reducing friction and wear.
Understand the 16 major application fields and characteristics of illite
Illite is a potassium-rich 2:1-type dioctahedral silicate mica-type clay mineral with missing interlayers, high content of potassium and aluminum, low iron, fine, and good corrosion resistance and resistance. It has excellent physical and chemical properties such as abrasiveness, fluidity, absorption and heat resistance, and is widely used in chemical fertilizers, rubber and plastics, cosmetics, environmental protection, soil conditioning, ceramics, molecular sieves, construction, papermaking, medicine, food and other fields.
1. Fertilizer industry
(1) Potash fertilizer
(2) New granular fertilizer
2. Plastics and rubber industry
Currently, plastic fillers have attracted widespread attention because of their low temperature, high thermal stability, flame retardancy, and good mechanical strength.
3. Super absorbent composite material
Illite and acrylamide can be used as raw materials to synthesize hybrid materials with adsorption capacity. This composite material not only has good adsorption performance, but also enhances the compatibility with the environment.
4. Cosmetics
Illite has a large cation exchange capacity and small particle size, so it can be used as a cosmetic filler. Illite in cosmetics can absorb skin waste and toxins. Illite can be anti-bacterial, non-toxic and other properties, can reflect ultraviolet rays, so it can play a role in anti-ultraviolet.
5. Environmental protection
With the development of industry, the pollution of soil and water bodies has become more and more serious, and the discharge of heavy metal pollutants in the nuclear industry, especially the pollution of radioisotopes, has become increasingly significant, posing a serious threat to the survival of human beings.
6. Soil conditioner
Illite can also be used as a component of clay minerals in some acidic soils. Illite reacts with NaF solution with pH=4.7. This reaction can improve these acidic soils and increase crop yields.
7. Ceramics
In ancient times, illite was the main natural raw material for making pottery. In the production process of ceramics, the content of clay minerals will have a significant impact on the quality of ceramics. This is because illite is rich in potassium, so the increase in illite content will reduce the melting point of the product, reduce water absorption, and reduce the glass phase. ratio increased.
8. Molecular sieve
In industry, illite is mainly used as adsorbent, catalyst and ion exchanger, in addition, illite also has some applications in solar energy conversion and photochemistry.
9. Construction industry
Illite ore is rich in aluminum, which increases the toughness of the product; it is also rich in potassium, which reduces the temperature at which it is calcined during the preparation of porcelain materials, thereby reducing energy consumption. Bricks fired with illite have better thermal insulation effect and lower price.
10. Paper industry
Illite has good absorption, moderate covering ability and transparency, so it can enhance the effect of use.
11. Medicine
Protein, DNA, etc. can be adsorbed by illite, so illite can be used as a carrier of genes in clinical treatment. Illite can be combined with proteins to form complexes into the organism, and then the proteins will be released under the appropriate environment, so as to achieve the purpose of treating diseases.
12. Flame retardant materials
Illite has good chemical inertness, electrical insulation, heat insulation and other properties, and can be used in the production of flame retardant rubber cables, flame retardant textiles, and flame retardant power cables.
13. Synthetic diamond
Due to the good heat resistance, corrosion resistance, insulation and expansion of illite, a small amount of illite clay mineral can be added when preparing diamond.
14. Oil decolorization
Illite can discolor oil, and the illite after surface modification treatment has strong discoloration performance.
15. Oil drilling mud
The particles of illite are small so that it has good floating ability, good heat resistance and wear resistance, and can be used in the process of drilling wells.
16. Food field
Because the far-infrared rays emitted by natural illite powder can decompose or remove the odor released by various foods, and at the same time can activate the water molecules in the food to keep fresh and prevent oxidation, so the deterioration of the food can be avoided.
Preparation of spherical calcium carbonate by hypergravity reaction crystallization and carbonization
The common forms of calcium carbonate mainly include irregular shape, spindle shape, spherical shape, flake shape and cube shape, etc. Different forms of calcium carbonate have different application fields and functions. , solubility and large specific surface area, etc., have important applications in the fields of plastics, rubber, food and paper making.
At present, the main preparation methods of spherical calcium carbonate are metathesis method and carbonization method. Although the metathesis method can produce spherical calcium carbonate with regular morphology and good dispersion, the raw materials of this method are expensive and a large amount of impurity ions will be introduced, which is not suitable for industrial production. The carbonization method is the most commonly used method in the industry. The traditional carbonization method is mainly divided into the intermittent carbonization method and the continuous spray carbonization method. Although the carbonization method has low cost and can be produced on a large scale, the traditional carbonization method for preparing spherical calcium carbonate has problems such as uneven particle size distribution and low production efficiency.
The hypergravity reaction crystallization method is a new method of preparing nanomaterials, and its essence is to generate huge centrifugal force through high-speed rotation, simulating the environment of hypergravity field. The high-speed rotating packing rotor in the hypergravity reactor beats the liquid into liquid filaments, droplets or liquid films, and the specific surface area of the liquid increases sharply. 1 to 3 orders of magnitude, the micro-mixing and mass transfer processes are greatly enhanced, so the reaction time is shorter than the traditional carbonization method, and the product has the advantages of small particle size, narrow particle size distribution, high product purity, and more regular morphology. . Hypergravity reactors are widely used in the preparation of nanomaterials due to their good micro-mixing and mass transfer effects.
Spherical calcium carbonate is grown from vaterite in most cases, but vaterite, as a thermodynamically unstable crystal form, is difficult to exist stably in a humid environment and aqueous solution, and requires some special methods to obtain it stably. The research shows that the introduction of NH4+ during the carbonization reaction can not only inhibit the formation of calcite during the crystallization process, and facilitate the transformation of the crystal form of calcium carbonate to vaterite, but also the atmosphere of NH4+ can make the generated vaterite exist stably in the solution.
Different from NH4+, acidic amino acids will dissociate in solution and combine with Ca2+ to form a seed crystal template. Under the influence of the seed crystal template, the resulting calcium carbonate will also appear metastable crystal phase, and suitable amino acid The introduction will generate specific functions and modify the morphology during the crystallization of calcium carbonate.
Using inexpensive glutamic acid and ammonium chloride as additives, the controllable preparation of spherical calcium carbonate in a hypergravity field was studied, and the effects of the two additives in the synthesis of calcium carbonate were investigated. The results showed that:
(1) Using the hypergravity reaction crystallization and carbonization method, the particle size can be obtained under the optimal conditions that L-glutamic acid and ammonium chloride are added at 4% and 20% calcium hydroxide, respectively, and the hypergravity factor is 161.0. Pure vaterite calcium carbonate with high sphericity of about 500nm.
(2) Before the reaction starts, L-glutamic acid and calcium ions in the solution form a template, which affects the nucleation and growth of calcium carbonate, and the abundant NH4+ in the solution during the reaction provides a good environment for the formation of vaterite, The high-speed cutting of the liquid by the hypergravity reactor prevents the possibility of excessive coating of calcium hydroxide raw materials, and realizes the controllable preparation of spherical calcium carbonate.
Effect of ultrafine talc on properties of lightweight coated paper
Talc is a magnesium silicate hydrate with a layered structure, with good chemical stability, strong acid and alkali resistance, high whiteness, fine particle size, good dispersibility, stable oil absorption, strong covering power, and electrical properties. Properties such as insulating properties and heat resistance. Talc is rich in resources and low in price. It is one of the most used ultrafine powder products in the world today. It is a promising white pigment and is widely used in ceramics, coatings, paper, textiles, rubber and plastics.
With the deepening of the research on talc powder, the application of talc powder in the paper industry is more and more extensive. Resin adsorbent for slurry when resin problem occurs in the production process of cultural paper and cardboard, and as a pigment for coating to replace part of kaolin or calcium carbonate, it is used to improve the performance of lightweight coated paper and special coated paper, and it is suitable for printing. performance and related ease of operation. The refractive index of talc is comparable to that of kaolin, and it has a flaky crystal form, a high aspect ratio and low oil absorption. It has low hardness and high whiteness. As a white pigment for paper coating, it can not only replace kaolin, but also have some properties better than china clay, especially suitable for light-weight coated paper coatings for rotary printing.
As a kind of paper with one coating and low coating weight, light-weight coated paper puts forward higher requirements for pigment hiding. The widely used kaolin with high hiding in the existing coating formulations. Flake kaolin is mainly imported from Brazil, and the price is relatively high. If a more cost-effective talc powder with the same covering ability and no need to import is used to replace the flake kaolin, the production cost can be continuously reduced on the premise of ensuring product quality, and the cost can be saved. play a positive role.
The effects of superfine talc replacing kaolin on the properties of lightweight coated paper coatings and paper properties were tested. the result shows:
(1) Brazilian kaolin is a thin sheet of clay, and its diameter and thickness are relatively large. Thin sheet china clay is beneficial to improve the coating coverage of light-coated paper, especially the light-coated paper with low coating weight (less than 8g/m2). American kaolin is usually finer in particle size and smaller in diameter and thickness. The high solid content of GCC of Yingge porcelain is conducive to the preparation of high-solids and low-viscosity coatings, and the brightness of the pigments is relatively high. Both superfine talc and Brazilian kaolin are flake structural pigments. The flake particles give the base paper better coverage, which can make the finished paper have better printing properties, such as uniform ink acceptance and high ink retention. The combination of particles of different shapes can obtain a loose coating, which is beneficial to improve the ink absorption of the coating.
(2) After the superfine talc powder replaces the kaolin in the coating formulation, with the increase of the amount of superfine talc powder, the low shear viscosity of the coating tends to increase, but the increase is limited; the water retention of the coating decreases slightly; The shear viscosity showed a decreasing trend, indicating that the use of talc instead of kaolin will have a favorable impact on the coating performance of the coating, which can further increase the solid content of the coating and obtain a better coating effect.
(3) After replacing the kaolin in the formula with ultra-fine talc, with the increase of the amount of ultra-fine talc, the whiteness, smoothness, opacity, gloss, surface roughness, printing gloss, etc. of the lightweight coated paper The quality and performance indicators remained at a similar level, and the printing surface strength was significantly improved.
Influence of particle size of stearic acid modified calcium carbonate on the properties of PBAT composite films
Polybutylene adipate/terephthalate (PBAT) is a copolymer of butylene adipate and butylene terephthalate, which not only has good toughness and stability, but also has excellent Biodegradability is an ideal green environmental protection film packaging material, and it is also one of the most studied biodegradable plastics.
However, the tensile strength of PBAT itself is low, the degradation rate is slow, and the price is 5 to 6 times that of ordinary polypropylene, so it is limited in application and promotion. The current research focuses on how to obtain biodegradable materials with superior performance and low cost. Most of the research is to prepare green composite materials by blending relatively cheap fillers with PBAT, ensuring its degradable properties at the same time. Control costs and expand its application value in the market.
Due to its low price and certain toughening effect on polymers, calcium carbonate is one of the most widely used polymer fillers. Using calcium carbonate as filling powder to prepare PBAT/calcium carbonate composite material has become a feasible way to reduce the cost of PBAT. By studying the properties of PLA/PBAT/nano-calcium carbonate ternary composites, the thermal and physical properties of the composites are greatly improved after adding nano-calcium carbonate. PBAT was filled with calcium carbonate, and it was found that calcium carbonate significantly reduced the cost while improving the mechanical properties of the composite. Modified PBAT with ultrafine calcium carbonate, when adding 20% calcium carbonate, the composite material still has good physical properties.
The surface modification of three kinds of calcium carbonate with different particle sizes was carried out with stearic acid, and the PBAT/modified calcium carbonate composite film was further prepared by melt blending method. The effects of mechanical properties and water vapor transmission properties show that:
(1) Through particle size analysis, the particle size distribution range of activated calcium carbonate is relatively wide, mainly distributed in 1 ~ 20μm, the volume average particle size is 7.6μm; the particle size of ultrafine calcium carbonate is mainly distributed in 0.2 ~ 5μm, volume average particle size. The diameter is 1.5 μm; the particle size distribution of nano-calcium carbonate is relatively concentrated, mainly distributed in 0.2-0.5 μm, and the volume average particle size is 0.34 μm. Through FTIR analysis, it was confirmed that stearic acid has been successfully coated on the surface of calcium carbonate, and the modified calcium carbonate has been dispersed in the PBAT matrix.
(2) After adding modified calcium carbonate, the crystallization temperature, crystallinity and melting temperature of PBAT are increased. When activated calcium carbonate with a volume average particle size of 7.6 μm was added, the crystallization temperature reached a maximum value of 84.12 °C, which was 13.07 °C higher than that of pure PBAT; the crystallinity also reached a maximum, from 10.4% of pure PBAT to 11.48%. When the modified nano-calcium carbonate was added, the melting temperature reached a maximum value of 124.99 °C.
(3) The mechanical properties of PBAT/modified calcium carbonate composite films were significantly improved, and with the decrease of the particle size of modified calcium carbonate, the mechanical properties gradually increased. When the modified nano-calcium carbonate with a volume average particle size of 0.34 μm is added, the tensile strength of the composite film reaches the maximum value of 19.9 MPa, which is 10.07 MPa higher than that of pure PBAT, and the nominal fracture strain reaches 551.8%, which is higher than that of pure PBAT. It is increased by 54%, and the right-angle tear strength is increased from 72.5kN/m of pure PBAT to 139.3kN/m.
(4) The barrier property of the film to water vapor is enhanced after adding modified calcium carbonate. The water vapor transmission rate of the composite film adding activated calcium carbonate is the lowest, which is 232.3g/(m2·24h), which is 28.06 lower than that of pure PBAT film. %, the corresponding water vapor permeability coefficient decreased by 66.09%.
Application of Nano-Calcium Compound Heavy Calcium in the Preparation of Silicone Rubber
There are many kinds of fillers for silicone sealants, such as silicon dioxide, nano-calcium carbonate, wollastonite powder, heavy calcium carbonate, etc., of which the largest amount is nano-calcium carbonate. In the domestic sealant market, the addition ratio of nano-calcium carbonate in silicone rubber exceeds 60%, and the amount used is very considerable.
More than 70% of the so-called nano calcium carbonate is added with different proportions of heavy calcium carbonate, but it is actually micro-nano composite calcium. Some nano-calcium carbonate synthesis technology is backward, resulting in disordered crystal form (it is difficult to see regular cubes in crystals, mostly small spindles and chain-like mixtures), poor processing performance, and high oil absorption value. Adding heavy calcium carbonate is In order to improve its processing performance, reduce its oil absorption value.
At present, only a few manufacturers can synthesize regular cubic nano-calcium carbonate products, and other irregular nano-calcium carbonate products have poor thixotropy, low tensile strength, low elongation, and poor elastic recovery. , the only benefit is the low price.
These micro-nano composite calcium seem to be cheap, but there are many hidden dangers:
1) poor mechanical properties;
2) The original nano-calcium carbonate has poor crystal form, high surface porosity and high water content, which will lead to poor storage stability or even thickening of the alcohol-based glue;
3) Heavy calcium carbonate is originally a very stable product, and it is mixed with nano calcium carbonate through surface treatment and subsequent drying process, which increases its instability;
4) Nano calcium carbonate is mixed with heavy calcium carbonate, which increases the mixing cost, drying cost and transportation cost of heavy calcium carbonate. It seems to be cheap, but it is actually more expensive.
Compared with the seemingly cheap micro-nano composite calcium, silicone rubber manufacturers use pure nano-calcium carbonate and heavy calcium carbonate in their respective production lines, and the silicone rubber products produced are more stable in performance and lower in cost.
Select pure nano calcium carbonate products with different particle sizes (15nm, 30nm, 40nm, 50nm, 60nm, 70nm) and 1500 mesh inactive heavy calcium carbonate in different proportions to prepare silicone sealants. By comparing the viscosity of the base materials , consistency, extrusion rate and the density, viscosity, consistency, extrusion rate, surface drying time, tensile strength, maximum strength elongation, elastic recovery rate and other indicators of sealant products. The results show that:
(1) More heavy calcium carbonate can be compounded with pure nano-calcium carbonate with finer particle size, and the density and various properties of the obtained sealant meet the standard requirements, and the cost is lower.
(2) Whether it is the production process of directly adding micro-nano composite calcium, or the production process of adding pure nano-calcium carbonate to compound heavy calcium carbonate, it is especially critical to select high-quality (regular crystal morphology) nano-calcium carbonate as a reinforcing material. , which is the main factor determining the mechanical properties of the final silicone rubber product.
(3) Compared with the use of micro-nano composite calcium, the use of high-quality pure nano-calcium carbonate compounded with heavy calcium carbonate to produce silicone rubber not only reduces the production cost of silicone rubber, but also helps to improve its mechanical properties; In terms of management and quality control management, it is also conducive to maintaining long-term stability of product performance.
Influence of Calcium Silicate, Talc, Light Calcium Compound Filler on Properties of Wallpaper Base Paper
As an important interior decoration material, wallpaper is favored by more and more consumers. Generally speaking, paper-based wallpaper requires good bulk and air permeability, and can release the moisture of the wall itself without causing the wallpaper to become moldy.
Compared with a single type of filler, the compound filling of attapulgite and calcium carbonate can significantly improve the strength properties of the paper. One of the main reasons.
Different types of mineral fillers can complement each other and cooperate with each other through compounding and filling, so as to optimize the performance of the filled paper.
(1) The addition of light calcium silicate to the compound filler can significantly increase the bulk of the base paper. At a filling amount of 30%, when calcium silicate: light calcium carbonate = 1:2, the bulk of the filled paper will be increased. The thickness is 15.2% higher than that of talcum powder: light calcium carbonate=1:2 compound filler and paper, and it has little effect on the filler retention rate, paper whiteness and tensile index.
(2) With the increase of the filling amount, compared with talc: calcium silicate: light calcium carbonate = 1:1:1 compound type, calcium silicate: light calcium carbonate = 1:2 compound type The increase of the bulk of the handsheet is more obvious, and the whiteness and opacity of the paper are better under the similar ash content of the finished paper. This is mainly because the whiteness and light scattering properties of light calcium are better, so increasing the proportion of light calcium in the compound filler is beneficial to improve the whiteness and opacity of the finished paper.