Wax is a class of substances with physical properties similar to beeswax, enumerated below:
Waxes may be natural secretions of plants or animals, artificially produced by purification from natural
petroleum or completely synthetic. In addition to
beeswax,
carnauba (a plant
epicuticular wax) and
paraffin (a petroleum wax) are commonly encountered waxes which occur naturally.
Earwax is an oily substance found in the human
ear. Some artificial materials such as
silicone wax that exhibit similar properties are also described as wax or waxy.
Chemically, a natural biological wax is a type of
lipid that may contain a wide variety of long-chain
alkanes,
esters,
polyesters and hydroxy esters of long-chain
primary alcohols and
fatty acids. They are usually distinguished from
fats by the lack of
triglyceride esters of
glycerin (propan-1,2,3-triol) and three fatty acids. In addition to the esters that contribute to the high melting point and hardness of carnauba wax, the
epicuticular waxes of plants are mixtures of substituted long-chain
aliphatic hydrocarbons, containing
alkanes, fatty acids, primary and
secondary alcohols,
diols,
ketones,
aldehydes.
[1] Paraffin waxes, refined waxes obtained from crude oils or coals, are
hydrocarbons, mixtures of
alkanes usually in a
homologous series of chain lengths.
Natural waxes do not have as much chemical energy as refined waxes because they are partially oxidized. Dependig on the origin, the energy content is similar to sugars to alcohols. Refined paraffin waxes are simply long chain hydrocarbons so they have the same energy content as kerosene, and make a more efficient hybrid propellant as evidenced by a higher Isp.
Waxes used in hybrid fuel grains should have a relatively high melting point so that the grain shape doesn't change on a hot day, but should be relatively soft, like rubber and not brittle, so that the wax will not crack due to the pyroshock when the motor is ignited.
Reference: First three paragraphs abstracted from
https://en.wikipedia.org/wiki/Wax and corrected for technical errors.
Bob
