Penetration Test
The penetration test is the measures of the depth to which a needle with a definite top load penetrates the wax sample. Where the conditions of test are not specifically mentioned, the load, time, and temperature are understood to be 100 g, 5 sec, 25° respectively, and the units of penetration to indicate tenths of a millimeter. The penetration test is particularly well adapted for microcrystalline waxes, and is more reliable than the durometer test in determining hardness [1]. This test provides an estimate of the consistency of waxes and their molecular characteristics.
Methods
It has been reported that the needle penetration on paraffin waxes increases with the increase of iso- and cyclo-paraffin[2]. A hard wax has a low penetration, whereas a soft wax has a high penetration.
The needle penetration method is used for waxes with a penetration less than 250dmm, as in the case of some paraffin and microcrystalline waxes, while the cone penetration method is used to perform the measurement in "soft waxes" like slacks waxes.
Needle Penetration
This test method (ASTM D 1231) covers the empirical estimation of the consistency of waxes derived from petroleum by measurement of the excent of penetration of a standard needle. This test method is applicable to waxes having a penetration of not greater than 250.[3].
The wax sample is melted to approximately 17°C above its congealing point. The melted wax is then poured into a cylinder container with a base to lie on a flat surface and once it has cool at in the room at 25°C, the container with the solidified wax is placed in a water bath at 25°C for 1 hour.
Verify that the penetrometer has the needle penetration placed and check that the indicator needle is placed at “zero” on the scale. Place the container cylinder so that the sample surface is level with the needle. This is done by rising or lowering the base with a screw located in the back of the penetrometer. Press the needle shaft and at the same time start the count of 5 seconds using a stopwatch or clock. And once the 5 seconds elapsed release the shaft of the penetrometer. Without moving the needle or the penetrometer´s base, press the handle located on the top of the penetrometer, until it touches the top of the needle holder. Finale take the reading which indicates the needle on the scale, the reading is given in tenths of a millimeter.
Cone Penetration (ASTM D 937)
This test method covers measuring with a penetrometer the penetration of petrolatum as an empirical measure of consistency.[3].
Pour the liquid wax in the container and let cool to room temperature, place it in a water bath at 25°C for 2 hours. Remove the sample from the water bath and place it on the penetrometer making sure the penetrometer´s scale reads zero. Lift the penetrometer´s base until the needle touches the sample and press the penetrometer insurance and start the count (5 seconds). Within the 5 seconds release the insurance and press the handle on the top. Finale take the reading which indicates the needle on the scale, the reading is given in tenths of a millimeter.
References
- ↑ Warth, A. H.; The Chemistry and Technology of Waxes. Reinhold Publishing Corporation. Second Edition, p. 612 – 614
- ↑ Zaky, M.T. (2005) A Study on the Dependence of Penetration on the Physical and Molecular Characteristics of Paraffin Waxes. Petroleum Science and Technology, Vol. 23, p 1381–1392
- ↑ 3.0 3.1 Annual Book of ASTM-Standards (American Society for Testing and Materials), Petroleum Products, Lubrications. (1999). West Conshohocken, Sect. 5