The physical properties of paraffin wax

Paraffin, also known as crystalline wax, is usually a white, odorless wax like solid that melts at 47 ° C-64 ° C, with a density of about 0.9g/cm3. It is soluble in non-polar solvents such as gasoline, carbon disulfide, xylene, ether, benzene, chloroform, carbon tetrachloride, and naphtha, but insoluble in polar solvents such as water and methanol. Pure paraffin is a good insulator, with a resistivity of 1013-1017 ohms per meter, which is higher than most materials except for certain plastics (especially PTFE). Paraffin is also a good heat storage material, with a specific heat capacity of 2.14-2.9J · g-1 · K-1 and a melting heat of 200-220J · g-1. The main performance indicators of paraffin are melting point, oil content, and stability. [2]

Melting point

Paraffin is a mixture of hydrocarbons, so it does not have a strict melting point like pure compounds. The so-called melting point of paraffin refers to the temperature at which a stagnant period first appears on the cooling curve of a paraffin sample that has been cooled and melted under specified conditions. All kinds of wax products require good temperature resistance of paraffin, that is, it does not melt or soften at a specific temperature. According to the differences in usage conditions, regions and seasons, as well as usage environments, it is required that commercial paraffin wax has a series of different melting points.

The main factor affecting the melting point of paraffin is the weight of the selected raw material fraction, and the paraffin extracted from the heavier fraction has a higher melting point. In addition, the oil content also has a significant impact on the melting point of paraffin. The more oil in paraffin, the lower its melting point.

Oil content

Oil content refers to the amount of low melting point hydrocarbons contained in paraffin. Excessive oil content can affect the chromaticity and storage stability of paraffin, as well as reduce its hardness. Therefore, the oil containing wax extracted from the vacuum distillation still needs to be deoiled using sweating or solvent methods to reduce its oil content. But most paraffin products require a small amount of oil, which is beneficial for improving the gloss and demolding performance of the products.

Stability

During the shaping or coating process, paraffin products are in a hot melt state for a long time and come into contact with air. If their stability is poor, they are prone to oxidation, deterioration, darkening of color, and even emitting a foul odor. In addition, paraffin will also turn yellow when used under light conditions. Therefore, it is required that paraffin has good thermal stability, oxidation stability, and light stability.

The main factors affecting the stability of paraffin are the trace amounts of non hydrocarbon compounds and polycyclic aromatic hydrocarbons it contains. To improve the stability of paraffin, it is necessary to deeply refine it to remove these impurities.

Thermophysical properties

Paraffin wax has high latent heat of phase change, almost no undercooling phenomenon, low vapor pressure during melting, is not prone to chemical reactions and has good chemical stability. After multiple heat absorption and release, the temperature and latent heat of phase change change are very small, self nucleation occurs, and there is no phase separation or corrosiveness.