G Scale Model Train Forum banner

1 - 7 of 7 Posts
G

·
Guest
Joined
·
0 Posts
Discussion Starter #1
Resin is a hydrocarbon secretion of many plants, particularly coniferous trees. It is valued for its chemical constituents

and uses, such as varnishes and adhesives, as an important source of raw materials for organic synthesis, or for incense and

perfume. Fossilized resins are the source of amber. Resins are also a material in nail polish.

The term is also used for synthetic substances of similar properties. Resins have a very long history and are mentioned by

both ancient Greek Theophrastus and ancient Roman Pliny the Elder, especially as the forms known as frankincense and myrrh.

They were highly prized substances used for many purposes, especially perfumery and as incense in religious rites.

The resin produced by most plants is a viscous liquid, composed mainly of volatile fluid terpenes, with lesser components of

dissolved non-volatile solids which make resin thick and sticky. The most common

terpenes in resin are the bicyclic terpenes alpha-pinene, beta-pinene, delta-3 carene and sabinene, the monocyclic terpenes

limonene and terpinolene, and smaller amounts of the tricyclic sesquiterpenes, longifolene, caryophyllene and delta-cadinene.

Some resins also contain a high proportion of resin acids. The individual components of resin can be separated by fractional

distillation

A few plants produce resins with different compositions, most notably Jeffrey Pine and Gray Pine, the volatile components of

which are largely pure n-heptane with little or no terpenes. The exceptional purity of the n-heptane distilled from Jeffrey

Pine resin, unmixed with other isomers of heptane, led to its being used as the defining zero point on the octane rating

scale of petrol quality. Because heptane is highly flammable, distillation of resins containing it is very dangerous. Some

resin distilleries in California exploded because they mistook Jeffrey Pine for the similar but terpene-producing Ponderosa

Pine. At the time the two pines were considered to be the same species of pine; they were only classified as separate species

in 1853.

Some resins when soft are known as 'oleo-resins', and when containing benzoic acid or cinnamic acid they are called balsams.

Other resinous products in their natural condition are a mix with gum or mucilaginous substances and known as gum resins.

Many compound resins have distinct and characteristic odors, from their admixture with essential oils.

Certain resins are obtained in a fossilized condition, amber being the most notable instance of this class; African copal and

the kauri gum of New Zealand are also procured in a semi-fossil condition.
 

·
Premium Member
Joined
·
4,716 Posts
Interesting.

And your point is?
 

·
Premium Member
Joined
·
259 Posts
Thank You, now I know what frankincense and myrrh are. It's great to have someone share information about products we use but don't know how they are made or where they come from or originated. Thanks again.

Cliff
 

·
Registered
Joined
·
1,065 Posts
why don't casting resins stink, but commercial resins have a toxic smell?

Also, I've had a gallon of resin for a couple years; is there a way to tell when or if it is too old to use (I suppose make a sample casting)

also, are there pros or cons to using epoxy vs resin in castings of train parts?
 

·
Premium Member
Joined
·
4,716 Posts
Myrrh does have the most amazing smell. No wonder the ancient's would kill for it.
 

·
Premium Member
Joined
·
428 Posts
The smell depends on what kind of resins you are wondering about. Resins stink from the solvents they contain. Most resins sold to the general public have reduced solvents so that the smell isn't over powering. Polyester Resins contain Styrene Monomer as a solvent and have a very strong smell while most epoxies contain no solvents. Many commercial urethane resins have a strong diesel smell while the one we sell to the public has no smell what so ever.


The gallon of resin that you have...What kind is it? Polyester resins usually start to crystallize in less than a year. Epoxies really don't go bad. I once took a solid can of epoxy resin and put it on a hot plate until it melted and then used it with hardener and it set up fine. That can was about 20 years old. You cannot bake out the crystals in a polyester resin. Urethane resins absorb moisture from the air. This moisture causes the finished part to be full of bubbles.


Epoxy takes longer to cure but it's main advantage is that it doesn't shrink. Polyester resin, because of the solvent flashing off, tends to shrink. It is best to use Urethane Resins to cast train parts that you want to be plastic. Most urethanes set up fairly quickly with minimal shrinkage.


Russ
 

·
Registered
Joined
·
811 Posts
any resin that manages to adsorb moisture will have problems, the resulting casting will foam. Other than that, try a test casting, if it seems to work, go for it.
 
1 - 7 of 7 Posts
Top