HPMC hydroxypropyl methyl cellulose identification method

HPMC hydroxypropyl methyl cellulose quality is not the determinant of whiteness, some manufacturers in the production process can not be added to determine product quality whitening agent.

1, whiteness:

Of course, the deciding factor of hydroxypropyl methyl cellulose quality is not whiteness, some manufacturers cannot judge product quality by adding whiter in the production process, and the quality of hydroxypropyl methyl fiber whiteness is really good.

2, color:

Hydroxypropyl methyl cellulose HPMC fineness is generally 80 mesh and 100 mesh, and 120 mesh, fineness is fine and uniform, the larger the particle size, the better solubility, good water retention, is high quality cellulose.

3. Transmittance:

Hydroxypropyl methyl cellulose is converted into water, and the viscosity and transparency can be seen after being dissolved in water for a period of time. After the formation of colloid, the higher the light transmission, the lower the transparency, the smaller the internal solubility and the higher the purity.

4. Proportion:

The larger the proportion, the heavier the better, because the proportion of hydroxypropyl methacrylic acid content is higher, high water retention rate.

At present, the quality of domestic hydroxypropyl methyl cellulose is uneven and the price is greatly different, making it difficult for customers to make the right choice. The modified HPMC of tongwai company, is the result of many years of research, adding trace substances can improve the construction performance, improve the operation, of course, will affect some other performance, but in general it is efficient; And domestic manufacturers of HPMC a large number of other ingredients, the only purpose is to reduce the cost of the product, resulting in water retention, adhesion and other performance greatly reduced, resulting in many building quality problems.

The differences between pure HPMC and adulterated HPMC are as follows:

1. The visual state of pure HPMC is fluffy and the packing density is small. The range is 0.3-0.4g/ mL; Adulterated HPMC liquidity is better, feel more heavy, and the appearance of the genuine there are obvious differences.

2. Pure HPMC aqueous solution clarification, high light transmittance, water retention rate ≥97%; Adulterated HPMC aqueous solution is turbid, water retention rate is difficult to reach 80%.

3. Pure HPMC should not smell ammonia, starch and alcohol; Adulterated HPMC can often smell all kinds of taste, even if tasteless, will feel heavy.

4. Pure HPMC powder is fibrous under microscope or magnifying glass; Adulterated HPMC granular solids or crystals can be observed under a microscope or magnifying glass.

200,000 is an impassable height?

Many domestic experts and scholars published papers that HPMC production by domestic equipment sealing, slurry process and low pressure production constraints, ordinary enterprises can not produce more than 200,000 viscosity products. It can't even produce more than 80,000 viscosity products in summer. They believe that the so-called 200,000 products must be fake products.

The expert's argument is not unreasonable, according to the domestic production situation in the past, can indeed draw the above conclusion.

The key to improve the viscosity of HPMC is the high sealing and high pressure reaction of the reactor and high quality raw materials. High sealability to avoid oxygen degradation of cellulose, high pressure reaction conditions to promote the etherifying agent into the cellulose interior and ensure the uniformity of the product.

Basic indexes of hydroxypropyl methyl cellulose:

2% aqueous solution viscosity 200000cps

Product purity ≥98%

Methoxyl content 19-24%

Hydroxypropoxy content: 4-12%

200000CPS hydroxypropyl methyl cellulose characteristics:

1. Excellent water retention and thickening performance to ensure complete hydration of slurry.

2. High bond strength and significant air entrain effect, effectively inhibit shrinkage and cracking.

3. Delay the heat release of cement hydration, delay the setting time, control the operation time of cement mortar.

4. Improve the water consistency of pumping mortar, improve rheology, prevent segregation and bleeding.

5. Special products, aiming at summer high temperature construction environment, to ensure efficient hydration of slurry, no stratification.

As a result of lax market supervision, mortar industry competition is increasingly fierce, some businesses in order to cater to the market, a large number of low cost materials, the production of cheap cellulose ether, here the editor has the obligation to remind the majority of customers, do not blindly pursue low, so as not to be deceived, resulting in engineering accidents, the final gain outweighed the loss.

Common adulteration methods and identification methods:

(1) adding amide cellulose ether, can make the solution viscosity of cellulose ether rapidly increase, resulting in can not be identified by viscometer.

Identification method: due to the characteristics of amide, this kind of cellulose ether solution will often appear the phenomenon of drawing, and good cellulose ether solution will not appear the phenomenon of drawing, the solution as jelly, the so-called sticky and not connected.

(2) add starch cellulose ether. Starch is generally insoluble in water, and solutions are often poorly transmittable.

Identification method: drop cellulose ether solution with iodine, the blue color can be considered as adding starch.

(3) adding polyvinyl alcohol powder. As we all know, polyvinyl alcohol powder such as 2488, 1788 market price is often lower than cellulose ether, mixed with polyvinyl alcohol powder can reduce the cost of cellulose ether.

Identification method: this cellulose ether is often granular, larger density. Dissolve quickly with water, pick the solution with glass rod, there will be more obvious wire drawing phenomenon.

Conclusion: cellulose ether due to its special structure and group, its water retention is irreplaceable by other substances, whether mixed with what kind of filler, as long as it is a large amount of incorporation, its water retention will be greatly reduced. Normal 10W viscosity of HPMC in ordinary mortar mixing amount of 0.15~0.2‰, water retention rate > 88% is no problem, and inferior cellulose ether added to 0.3‰ of the water retention rate may not be able to reach 88%, mortar often bleeding more serious. Therefore, water retention rate is an important indicator of HPMC, is good or bad, as long as the mortar is added, it will be clear at a glance.