Softening Point

The softening point is the temperature at which a substance attains a particular degree of softness. Since in technical use waxed surfaces frequently come in contact with liquids under pressure it becomes necessary to recognize the temperature at which the wax will lose its firmness and perhaps its utility as well.

Methods

The softening point of wax is the temperature at which the solid wax begins to soften. Synthetics waxes such polyethylene wax and some blends of hydrocarbon waxes with polymers that have no definite melting point, they are reported with softening point. Waxes used in hot-melt adhesives require high temperature performance, and so the softening point can be an indication of the performance properties of the wax.

Ring-and-Ball

Ring & Ball method was designed in engineering civil to determine the softening point of asphaltic bitumen and fluxed native asphalt, road tar, coal tar pitch and blown type bitumen but it is well used in the determining the softening point in waxes. The principle behind this test is that softening point is the temperature at which the substance attains a particular degree of softening under specified conditions of the test.

The apparatus for the ring and ball method consists in a pouring plate, rings, ring holder, balls, ball-centering guides and a glass vessel, capable of being heated, not less than 85 mm in inside diameter and not less than 120 mm in depth from the bottom of the flare.

The wax sample is melted and stirred until it is completely fluid and free from air bubbles and water. The molten wax is poured into the rings, previously heated to a temperature approximately to that of molten material on a metal plate; the excess material is removed with a slightly heated knife or spatula.

The apparatus is assembling with the specimen rings, ball-centering guides, and thermometer in position, and the bath is filled with freshly boiled distilled water or pure glycerin [For referee purposes, all softening points up to 80°C (176°F) shall be determined in a water bath and all softening points above 80°C (176°F) shall be determined in a glycerin bath], so that the liquid depth will be 105 ± 3 mm with the apparatus in place.

Steel balls are placed from the bottom of the bath in each ball-centering guide and heat is applied to the bath and stir. The softening point is the temperature at which the material softens and allows the balls to pass through the ring.