Year1
- 含量：
- 99
- 外观：
- 白色
- 包装：
- 25公斤
Designed an experimental point.
The preparation method of the paraffin-stearic acid mixed melt system sample is: weigh the paraffin according to a certain proportion, put it into a beaker, and heat it until the paraffin just melts
Weigh the stearic acid according to a certain proportion, and add Add it to the melted paraffin
() Control the temperature of the paraffin below ℃. After the stearic acid is fully melted, stir continuously with a glass rod to make the two fully mixed
Cool naturally. That is, the experimental sample is obtained. Use a digital melting point meter to measure the melting point of the sample.
The specific method is: crush the cooled waxy material, and fill the capillary tube with each sample at one time. The linear heating rate of the melting point instrument is uniformly set at ℃, and the starting temperature is ~℃ lower than the melting point.
Effect of stearic acid on the melting point and mechanical properties of paraffin
Measure its compressive strength. The specific method is: prepare the wax material into a cylinder, and the diameter of the bottom surface of the cylinder is ., high. Use sandpaper to polish the upper and lower surfaces of the cylinder smooth and parallel, and place it on the testing machine to measure the strength. An infrared absorption spectrum analyzer was used to conduct infrared absorption spectrum analysis on the above samples. Since the sample has good transparency after melting, the sample preparation method uses the solution method. The specific method is: heat the sample to melt it, and put the melted sample into the sample pool for infrared absorption spectrum analysis.
., while the strength of pure stearic acid is ., higher than that of paraffin wax. The strength of the paraffin-stearic acid mixed melt system sample gradually increases in a step-like manner with the increase of the stearic acid mass fraction. According to its change law, it can be divided into segments: when the stearic acid mass fraction is ~, it is characterized by paraffin wax The strength increases rapidly. When the stearic acid mass fraction is ~, the strength of paraffin wax is., which is higher than the strength of pure paraffin. The strength growth rate is up to. When the stearic acid mass fraction is ~, the strength of the paraffin-stearic acid system rises slowly. High, when stearic acid
Experimental results
. Effect of stearic acid on the melting point of paraffin
When the mass fraction is, the system strength is., Compared with the system strength when the stearic acid mass fraction is Only increased., its strength growth rate was only. () When the stearic acid mass fraction was ~, the strength of the paraffin-stearic acid system increased rapidly, from. to., the strength increased., its strength increased. The rate is. When the crystal is heated to a certain temperature, it immediately changes from solid to liquid. The temperature at this time can be regarded as the melting point of the substance. The melting point is divided into two types: initial melting and final melting: as the heating temperature increases, when the solid shrinks and the sample begins to collapse and a liquid phase appears, it is the initial melting. The temperature at this time is called the initial melting temperature. When the solid disappears completely, the melting point is divided into two types: initial melting and final melting. When it turns into a transparent liquid, it is the final melting. The temperature at this time is called the final melting temperature. The final melting temperature and the initial melting temperature
The picture shows the variation pattern of the initial melting temperature and the final melting temperature of the paraffin-stearic acid mixed melt system sample. curve. It can be seen from the figure that the melting distance of the sample of this system is small, generally less than .℃. The overall shape and characteristics of the two melting point curves of the initial melting temperature and the final melting temperature are consistent, and they are both an asymmetrical font curve. The changing trend of its final melting temperature can be divided into two sections: taking the stearic acid mass fraction as the boundary, when the stearic acid mass fraction is ~, the final melting temperature decreases with the increase of the stearic acid mass fraction, that is, by .℃ When the stearic acid mass fraction drops to .℃, the final melting temperature gradually increases, from .℃ to .℃. Figure is the compressive strength change characteristic curve of the paraffin-stearic acid mixed melt system sample
. Infrared analysis
The figure is the sample when the mass fractions of pure paraffin, pure stearic acid and paraffin and stearic acid are all Infrared absorption spectrum curve.
According to previous research results, the absorption band values and their assignments of each sample in the figure are listed in the table. The picture is the infrared absorption spectrum curve of pure paraffin, which shows that paraffin mainly has an absorption peak. There are three absorption peaks (,,) with wave numbers between ~, which are caused by the stretching vibration of carbon-hydrogen bonds in 3 and
The picture is the infrared absorption spectrum curve of pure stearic acid. In addition to the absorption peaks in pure paraffin (picture), the figure
also contains some absorption bands that are different from paraffin. The absorption peak with a wave number at
- is caused by the stretching vibration of
WhatsApp
