What kind
of rubbers can I use for Mould-making?
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This manual
will review five of the most widely used mould making materials: latex,
alginates, polyurethanes, vinyl hot melts and silicones. Each has
advantages and disadvantages. No one material will do everything. Latex is possibly the
most widely used material, mainly because of its comparatively low cost
and elasticity. It is capable of making a strong, thin walled mould,
ideally suited for one piece “skin” or “glove” moulds Because as many
as 10 to 20 coats must be brushed on to give the mould a workable
thickness, with time allowed between each coat to enable the latex to
cure or “dry”, making the mould is very slow and time consuming. In addition
latex must be brushed on, dipped or sprayed, it cannot be poured to
make a mould. The thin walled nature of the finished latex mould makes
a back-up mould a necessity to support the latex and help it to retain
its shape when casting. As shrinkage is
also a problem, latex cannot be used to make moulds where dimensional
accuracy is a requirement. Aldax Moulds
sell their latex in three grades, #70 which is a thin brush or spray on
latex which is used for the first 3 or 4 coats to retain detail, #72
which is a thickened latex used for building up coat thickness and #74
which is a filled latex for use on vertical surfaces. Our latex can
we purchased from our online ebay store by clicking
here. “Hot-melt”
(Polyvinyl chloride) is not cheap
to buy. However vinyl moulds are cost effective in that they can be
re-melted and the material used again. Vinyl is
hazardous and disagreeable to use because of the high temperatures
required to melt the material. The high temperature in turn restricts
the model materials that can be used with vinyl to make moulds and has
fallen from general use. Silicone rubbers make high quality moulds for casting resins and foams, but the material is very expensive. Silicone is the material of choice for polyurethane plastics and low temperature metals. |
It is easy to
use, dimensionally accurate and without the moisture problems of
polyurethane. Aldax Moulds
have a general purpose silicone rubber CraftSil 750 which we have found
has been suitable for over 90% of our customers requirements. View this
item on our ebay store by clicking here. Alginates are mainly used
when time is a critical factor or for body casting, as they are
completely safe for body contact. They set up in minutes to a rubbery
type of gel when mixed with water and give excellent impressions. Due to the fact
that they dry out quite rapidly they must be cast almost immediately
after demoulding. Plaster or wax are mostly used in this type of mould. Click
here to view our Minit Mold Alginate. Polyurethanes are rapidly
becoming the mouldmaking material of choice. They are much cheaper than
silicones while performing much the same functions. They come in 2 part
systems that are easy to weigh and mix due to their fluidity. They can
be used for pouring practically any type of cementicious or plaster
material, casting resins or foams. Along with most
of these materials they have a limited shelf life and are very
“moisture Conscious” however from the point of view of ease of use and
economy they have become the preferred mould making material. The feature of
polyurethanes that attracted us most was the long life of the moulds.
We used polyurethane exclusively for making of plaster ceramic master
case moulds. Unlike latex which under heavy use has a 12 month life,
our polyurethane moulds are still producing perfect moulds after 15
years. While there
have been hundreds of different types of polyurethanes developed for
specific industry usage, tomorrow the chemists tell use there will be
thousands, due to the versatility of polyurethanes from flexible
rubbers through foams to hard plastics.
For purchasing
information, send us an email to aldax@bigpond.com.au |
ã Copyright 2006 Aldax industries
Pty Ltd www.aldax.com.au