Materials
POLYESTER RESIN
General purpose resin can be used for normal laminating and a special casting resin is available for pouring solid objects. There are many different resins but the variations are mostly to do with gel time and cure times. Obviously for some jobs a long gel time is needed to allow you the time to lay in the glass fibre and roll the air from the laminate. In casting resins, occasionally a very fast cure is needed for turn around of very small objects such as chess men. In most cases a very long, slow cure is required so that there is no distortion or cracking of the casting. When attempting other than general purpose laminating seek advice from your supplier.
CATALYST or MEKP
Catalyst is normally a liquid and must be handled with extreme care. Un-catalysed resin simply will not harden. The measurement of catalyst in the resin is critical and it cannot be stressed enough that all safety precautions must be followed. MEKP (Methyl Ethyl Ketone Peroxide) is very dangerous to the eyes and can self ignite when mixed with other products. It is normally used in a ratio of 1-2% by weight of the total polyester resin. A rule of thumb, 20mls of catalyst is usually needed for 1kg of resin. Accurate measurement is important because a small increase or decrease of the amount of catalyst can have a large effect on the gel time or working time of the polyester resin.
GELCOAT
Gelcoat is a pigmented resin which forms the smooth outer surface of the finished laminate and is therefore applied first to the mould. Usually 450-600gms of gelcoat is needed for each square metre of mould surface. It is not normally used for castings. Gelcoat is available in virtually any colour including clear.
GLASSFIBRES
There is a large variety of glassfibre materials which are available for various needs. The most common one is chopped strand mat and probably 90% of all home handyman jobs are done using chopped strand mat. This is a mat comprising of small fibres held together with a binder to allow them to be laid into the mould. Another common product is woven roving where the glass strands are woven into a mat to give extra strength. It is usual in boat building for instance to use a combination of chopped strand mat and woven roving to get bulk plus strength.
Chopped Strand Mat and Woven Roving
RELEASE AGENTS
Release agents are applied to the mould prior to laminating to prevent the laminate from sticking to the mould surface. They are not normally required for casting where RTV rubber flexible moulds are normally used, They come in many shapes and types for various products and it is best to seek advice as to the best type for the project that you are currently engaged in.
FILLERS
Inert fillers can be added to resin to produce a general purpose body filler stopper paste, or to make a slurry for resin casting. They are not usually needed for many laminating projects but it is very common to use fillers for casting projects. Two common fillers are calcium carbonate and Q-Cels. However Q-Cels are normally used in conjunction with epoxy resin to make a coving filler in right angle corners and for ease of sanding.
COLOUR PIGMENTS
Although laminates and castings can be painted, it is often simpler to colour the resin before laminating. By adding pigment paste to the resin in a small amount you can tint the resin into a suitable colour. It is wise to seek advice from your supplier before doing this.
BARRIER & CLEANSING CREAMS
In some cases the skin can be irritated by polyester resin and it is wise to wear a barrier cream in conjunction with gloves when handling resins and glass fibre. Low cost disposable gloves are available and the cost is largely offset by the reduction in using cleaning liquids, such as acetone, which are not recommended for cleaning resin from skin.
SPECIALIST RESINS
Apart from the normal laminating resins there is a large variety of other resins available for specialist uses, such as making chemical resistant tanks or fire retardant laminates, clear encapsulating castings, adhesion to acrylic panels, etc.
SPECIALIST REINFORCEMENTS
Reinforcements other than glass fibre are sometimes used in high performance laminates. A typical example is Kevlar, a synthetic aramid material which is even stronger than glass fibre, and has excellent impact resistance (it is used to make bullet-proof vests) and carbon fibre which gives greatly increased rigidity to the laminate. It is used for applications requiring a strong but lightweight laminate e.g. race car bodies. It is advisable to seek advice before using these specialist materials as they are more difficult to use than the standard glassfibre and their characteristics while strong in some areas, can be weak in others.
Carbon fibre and carbon kevlar cloth
STYRENE
Styrene can be used to thin resins in certain cases but not normally recommended, again advice should be sought before adding to resin.
WAX SOLUTIONS
Wax is often added to resin or gelcoat to reduce the tackiness that is often left on the surface of the resin. The addition of wax to resins or gelcoats makes it easier to sand that surface without clogging the sand paper. This is especially useful when doing small gelcoat repairs. However, for large jobs it is advisable to use fully formulated flocotes or top coats.
CORE MATERIALS
Core materials come in a variety of types and are used to increase the stiffness of particularly flat panels. Coremat, divinycel, klegecel, and balsa to name just a few. Again advice should be sought before using these materials.
Foam and balsa
General purpose resin can be used for normal laminating and a special casting resin is available for pouring solid objects. There are many different resins but the variations are mostly to do with gel time and cure times. Obviously for some jobs a long gel time is needed to allow you the time to lay in the glass fibre and roll the air from the laminate. In casting resins, occasionally a very fast cure is needed for turn around of very small objects such as chess men. In most cases a very long, slow cure is required so that there is no distortion or cracking of the casting. When attempting other than general purpose laminating seek advice from your supplier.
CATALYST or MEKP
Catalyst is normally a liquid and must be handled with extreme care. Un-catalysed resin simply will not harden. The measurement of catalyst in the resin is critical and it cannot be stressed enough that all safety precautions must be followed. MEKP (Methyl Ethyl Ketone Peroxide) is very dangerous to the eyes and can self ignite when mixed with other products. It is normally used in a ratio of 1-2% by weight of the total polyester resin. A rule of thumb, 20mls of catalyst is usually needed for 1kg of resin. Accurate measurement is important because a small increase or decrease of the amount of catalyst can have a large effect on the gel time or working time of the polyester resin.
GELCOAT
Gelcoat is a pigmented resin which forms the smooth outer surface of the finished laminate and is therefore applied first to the mould. Usually 450-600gms of gelcoat is needed for each square metre of mould surface. It is not normally used for castings. Gelcoat is available in virtually any colour including clear.
GLASSFIBRES
There is a large variety of glassfibre materials which are available for various needs. The most common one is chopped strand mat and probably 90% of all home handyman jobs are done using chopped strand mat. This is a mat comprising of small fibres held together with a binder to allow them to be laid into the mould. Another common product is woven roving where the glass strands are woven into a mat to give extra strength. It is usual in boat building for instance to use a combination of chopped strand mat and woven roving to get bulk plus strength.
Chopped Strand Mat and Woven Roving
RELEASE AGENTS
Release agents are applied to the mould prior to laminating to prevent the laminate from sticking to the mould surface. They are not normally required for casting where RTV rubber flexible moulds are normally used, They come in many shapes and types for various products and it is best to seek advice as to the best type for the project that you are currently engaged in.
FILLERS
Inert fillers can be added to resin to produce a general purpose body filler stopper paste, or to make a slurry for resin casting. They are not usually needed for many laminating projects but it is very common to use fillers for casting projects. Two common fillers are calcium carbonate and Q-Cels. However Q-Cels are normally used in conjunction with epoxy resin to make a coving filler in right angle corners and for ease of sanding.
COLOUR PIGMENTS
Although laminates and castings can be painted, it is often simpler to colour the resin before laminating. By adding pigment paste to the resin in a small amount you can tint the resin into a suitable colour. It is wise to seek advice from your supplier before doing this.
BARRIER & CLEANSING CREAMS
In some cases the skin can be irritated by polyester resin and it is wise to wear a barrier cream in conjunction with gloves when handling resins and glass fibre. Low cost disposable gloves are available and the cost is largely offset by the reduction in using cleaning liquids, such as acetone, which are not recommended for cleaning resin from skin.
SPECIALIST RESINS
Apart from the normal laminating resins there is a large variety of other resins available for specialist uses, such as making chemical resistant tanks or fire retardant laminates, clear encapsulating castings, adhesion to acrylic panels, etc.
SPECIALIST REINFORCEMENTS
Reinforcements other than glass fibre are sometimes used in high performance laminates. A typical example is Kevlar, a synthetic aramid material which is even stronger than glass fibre, and has excellent impact resistance (it is used to make bullet-proof vests) and carbon fibre which gives greatly increased rigidity to the laminate. It is used for applications requiring a strong but lightweight laminate e.g. race car bodies. It is advisable to seek advice before using these specialist materials as they are more difficult to use than the standard glassfibre and their characteristics while strong in some areas, can be weak in others.
Carbon fibre and carbon kevlar cloth
STYRENE
Styrene can be used to thin resins in certain cases but not normally recommended, again advice should be sought before adding to resin.
WAX SOLUTIONS
Wax is often added to resin or gelcoat to reduce the tackiness that is often left on the surface of the resin. The addition of wax to resins or gelcoats makes it easier to sand that surface without clogging the sand paper. This is especially useful when doing small gelcoat repairs. However, for large jobs it is advisable to use fully formulated flocotes or top coats.
CORE MATERIALS
Core materials come in a variety of types and are used to increase the stiffness of particularly flat panels. Coremat, divinycel, klegecel, and balsa to name just a few. Again advice should be sought before using these materials.
Foam and balsa
For further information on the materials used in producing composites, please visit www.nuplex.com