What is the difference between the performance of methyl cellulose ether and lignin fiber
Answer: The performance comparison between methyl cellulose ether and lignin fiber is shown in the table
Performance comparison between methyl cellulose ether and lignin fiber
|
performance |
methyl cellulose ether |
lignin fiber |
|
water soluble |
yes |
No |
|
Adhesiveness |
yes |
No |
|
water retention |
continuity |
short time |
|
viscosity increase |
yes |
Yes, but less than methyl cellulose ether |
What should be paid attention to when using methyl cellulose and carboxymethyl cellulose?
Answer: (1) When using hot water to dissolve cellulose, it must be fully cooled before use. The temperature required for complete dissolution and the ideal transparency depend on the type of cellulose.
(2)Temperature required to obtain sufficient viscosity
Carboxymethylcellulose≤25℃, methylcellulose≤20℃
(3)Slowly and evenly sieve the cellulose into the water, and stir until all the particles are soaked, and then stir until all the cellulose solution is completely transparent and clear. Do not pour water directly into the cellulose, and do not directly add a large amount of cellulose that has been dampened and formed into lumps or balls into the container.
(4)Before the cellulose powder is wetted with water, do not add alkaline substances to the mixture, but after dispersion and soaking, a small amount of alkaline aqueous solution (pH8~10) can be added to accelerate the dissolution. Those that can be used are: sodium hydroxide aqueous solution, sodium carbonate aqueous solution, sodium bicarbonate aqueous solution, lime water, ammonia water and organic ammonia, etc.
(5)The surface-treated cellulose ether has better dispersibility in cold water. If it is directly added to the alkaline solution, the surface treatment will fail and cause condensation, so more care should be taken.
What are the properties of methylcellulose?
Answer: (1) When heated above 200°C, it melts and decomposes. The ash content is about 0.5% when burned, and it is neutral when it is made into slurry with water. As for its viscosity, it depends on the degree of polymerization.
(2) Solubility in water is inversely proportional to temperature, high temperature has low solubility, low temperature has high solubility.
(3) It can be dissolved in the mixture of water and organic solvents, such as methanol, ethanol, ethylene glycol, glycerin and acetone.
(4) When there are metal salts or organic electrolytes in its aqueous solution, the solution can still remain stable. When the electrolyte is added in a large amount, gel or precipitation will occur.
(5)Has surface activity. Due to the presence of hydrophilic and hydrophobic groups in its molecules, it has the functions of emulsification, protective colloid and phase stability.
(6)Hot gelling. When the aqueous solution rises to a certain temperature (above the gel temperature), it will become turbid until it gels or precipitates, causing the solution to lose its viscosity, but it can return to the original state after cooling. The temperature at which gelation and precipitation occur depends on the type of product, the concentration of the solution, and the rate of heating.
(7)The pH is stable. The viscosity of aqueous solution is not easily affected by acid and alkali. After adding a considerable amount of alkali, regardless of high temperature or low temperature, it will not cause decomposition or chain splitting.
(8)After the solution dries on the surface, it can form a transparent, tough and elastic film, which is resistant to organic solvents, fats and various oils. It does not turn yellow or fluffy when exposed to light, and can be re-dissolved in water. If formaldehyde is added to the solution or post-treated with formaldehyde, the film is insoluble in water, but can still partially expand.
(9)Thickening. It can thicken water and non-aqueous systems, and has good anti-sag performance.
(10)Viscosity. Its aqueous solution has strong cohesiveness, which can improve the cohesiveness of cement, gypsum, paint, pigment, wallpaper, etc.
(11)Suspension. It can be used to control the coagulation and precipitation of solid particles.
(12)Protect the colloid and improve the stability of the colloid. It can prevent the accumulation and coagulation of droplets and pigments, and effectively prevent precipitation.
(13)water retention. The aqueous solution has a high viscosity. When added to the mortar, it can maintain a high water content, which effectively prevents excessive absorption of water by the substrate (such as bricks, concrete, etc.) and reduces the evaporation rate of water.
(14)Like other colloidal solutions, it is solidified by tannins, protein precipitants, silicates, carbonates, etc.
(15)It can be mixed with carboxymethyl cellulose in any proportion to obtain special effects.
(16)The storage performance of the solution is good. If it can be kept clean during preparation and storage, it can be stored for several weeks without decomposition.
NOTE: Methylcellulose is not a growth medium for microorganisms, but if it becomes contaminated with microorganisms, it will not prevent them from multiplying.If the solution is heated for too long, especially in the presence of acid, the chain molecules may also split, and the viscosity will decrease at this time. It can also cause splitting in oxidizing agents, especially in alkaline solutions.
What is the main effect of carboxymethyl cellulose (CMC) on gypsum?
Answer: Carboxymethyl cellulose (CMC) mainly plays the role of thickening and adhesive, and the water retention effect is not obvious. If it is used in combination with water retention agent, it can thicken and thicken the gypsum slurry and improve the construction performance, but carboxymethyl cellulose The base cellulose will retard the setting of the gypsum, or even not solidify, and the strength will drop significantly, so the usage amount should be strictly controlled.