Cellulose Ethers and Test Methods

Cellulose Ethers Used in the Construction Sector and Test Methods Cellulose is an environment-friendly natural polymer derived from trees and plants, and is generally obtained from wood, cotton or fibrous plants. Trees and plants from which cellulose and its derivatives are obtained worldwide are decreasing with each passing day. To prevent this situation, studies on obtaining cellulose from cotton waste and renewable plants have recently been among the priorities of scientists. (1) Cellulose, which finds application in various fields such as cleaning materials, pharmaceuticals and cosmetics, is synthesized in different forms such as methyl cellulose (MC), hydroxyethyl cellulose (HEC), hydroxyethyl methyl cellulose (HEMC), and hydroxypropyl methyl cellulose (HPMC) through etherification, and plays a very important role in the construction and paints and coatings sector. Cellulose ethers used in the paints and coatings industry are used to improve viscosity stability and paint solubility, while in the construction and building industry they are used to increase binding, water retention and working time. Additionally, they are effective materials in textiles as binders, in adhesives for thickening and water retention properties, and in ceramics. For selecting the appropriate cellulose ether for the system, viscosity, moisture content, ash content, working time (open time), shear, tensile and spread parameters are evaluated. In this study, with the support of Reaksiyon Kimya R&D laboratory, some of these methods were examined based on the products of MIZUDA, which is a representative of cellulose derivative manufacturers serving the construction sector.

Viscosity Value

Measurement is performed using a viscometer according to the Brookfield method at 20°C and by preparing a 2% solution of the product. The value obtained as a result of the measurement conducted in accordance with ASTM D2364 (3) standard is determined in mPa.s. Viscosity is one of the most important parameters that determines the application areas and quality of cellulose product groups. Cellulose ethers retain mixing water with increasing viscosity and impart water retention properties to the mortar, preventing the underlying layer from absorbing the mixing water. Without water loss, hydration continues and the mortar does not experience strength loss. (4)

Moisture Content

The moisture content in the cellulose ether to be tested is measured according to ASTM D2364-15 (2021) (3) standard by placing 1 g in a moisture analyzer set at 105°C. The percentage moisture content is determined by the calculation %Moisture = 100 – moisture analyzer value. An increase in moisture value causes a decrease in the water retention property of the cellulose ether in the system.

Ash Content

The ash content in the cellulose ether to be tested is measured according to ASTM D3516-89(2019)e1 (3) standard by burning at high temperatures in a crucible to measure inorganic matter content. M2: Final weighing M1: Crucible tare % Ash content = ((M2-M1) / sample amount)*100 is used to determine the % ash content. High ash content reduces the performance of cellulose ether in the system.

Spread Test

According to TS EN 13395-1 standard (4); the spread table is placed on a flat and fixed surface. Contact blocks, table and mold are cleaned and wiped with a damp cloth immediately before the test to remove excess free water. The mold is placed at the center of the upper plate and held in place by pressing on the foot parts to prevent material leakage from the bottom during filling. Fresh concrete is filled into the mold in two equal layers using a scoop; during filling, each layer is lightly tapped 10 times with a compacting rod to be compacted. Excess concrete overflowing from the top level of the mold is scraped off and the remaining part of the table along the edges of the conical mold base is cleaned by wiping. 30 seconds after scraping the upper surface, the mold is slowly lifted vertically within 3-6 seconds by holding the handles. The spread table is fixed by pressing on the end plate located on the front of the table, and the upper plate is slowly lifted to the stop piece. The plate is freely dropped onto the lower stops, and this operation is repeated for a total of 15 drops. Each lifting and dropping operation should be completed between 2-5 seconds. After the dropping operations are completed, the largest dimensions of the concrete layer spread on the upper plate are measured in two directions parallel to the plate edges as d1 and d2 using calipers. The measurement results obtained in both directions are recorded by rounding to the nearest 1 mm, and the average of the two test results conducted in the same time is taken. The consistency value equals this average result value. If the deviation of the values obtained from two samples from the average spread value exceeds 10%, two more samples should be taken and the test repeated.

Shear Test

After powder products (sand + cement + cellulose ether) are mixed, water is added and mixed in a concrete mixer at 280 rpm for 1 minute. A flat tape is attached to the top of the EN 1323 standard concrete tile to clearly measure the shear distance. The tile is wetted with a damp cloth and the homogeneously mixed mortar from the mixer is poured onto the tile and the tape is slowly pulled. The tile is slowly placed in line with it being flat, and a 2 kg weight is held on this tile for 30 seconds. The empty space remaining at the top (mortar-free area) is measured with calipers and recorded as the initial measurement. The standard tile is slowly lifted and kept in a vertical position for 15 minutes, and at the end of the 15th minute it is laid down and the section from the beginning of the concrete tile to the ceramic tile is measured again with calipers; this value is recorded as the second measurement. Shear distance is determined as the difference between the final measurement and the initial measurement. Here, the shear distance of the ceramic tile on the mortar in vertical position was measured as 0.17 mm. Zero or minimal shear distance is the preference for both manufacturers and applicators. For this reason, high shear resistance is expected.

Open Time Test

After powder products (sand + cement + cellulose ether) are mixed, water is added and mixed in a concrete mixer at 280 rpm for 1 minute. The EN 1323 standard concrete tile is wetted with a damp cloth, the mixture taken from the mixer is poured onto this tile and smoothed with a trowel. The mortar applied to the tile is left for 20 minutes. At the 20th minute, 1 ceramic tile is slowly placed on the mortar and a 1 kg weight is placed on it. The weight is held on the tile for 30 seconds. At 5-minute intervals, 6 ceramic tiles are bonded to the mortar using the same method. At the 45th minute, after the 6th ceramic tile is bonded, the first bonded tile is slowly lifted with a spatula. Again, all ceramics are lifted at 5-minute intervals. Surface appearances are examined and the open time test is concluded based on these observations. The last tile was removed at the 65th minute from the time of mortar pouring. Open time, with an extended crusting period, provides the applicator with easy working conditions, and this period is a very important parameter in cellulose ether selection. [caption id="attachment_142705" align="aligncenter"] Figure 7: Tested with cellulose ether MH-EM50LX.

[/caption] [caption id="attachment_142706" align="aligncenter"] Table 1: Open Time measurement results for MH-EM50LX[/caption] Cellulose ethers, used in the production of many products such as ceramic adhesives, plasters, repair mortars, leveling compounds and paints, are easily and homogeneously distributed in the system due to their small particle sizes, while increasing the viscosity of the mortar to prevent the material from sliding or flowing from the applied surface. With their property of retaining water, they delay the drying of the product when the powder mixture is made into mortar, extending the working time. At the same time, with this property, they help the mortar to spread more easily on the applied surface and achieve better adhesion. When all studies are evaluated, it is observed that Reaksiyon Kimya-MIZUDA cellulose group supports the preparation of value-added products for many different applications of standard cellulose ethers in the construction sector. MH series cellulose groups offer valuable solution options to meet sector expectations with pure and modified product variety. You can view technical information about MIZUDA brand HPMC and HEMC products on our website and contact our sales managers. References 1. http://jes.ksu.edu.tr/tr/download/article-file/267726, 2. https://tr.wikipedia.org/wiki/Sel%C3%BCloz,3. https://www.astm.org/catalogsearch/result/?q=cellulose, 4.https://www.cimsa.com.tr/ca/docs/71DDECEE521E470BA4ADA95A091840/75DBD3617E9D4378B8A 17A2A4AE6AB5F.pdf Sevtap Karasu Sales Manager Reaksiyon Kimya