TECHNICAL
ADVICE
TECHNICAL GLOSSARY
Accelerator
Additive that reduces the thermosetting plastics gelling and polymerisation time, such as gel coats and polyester resins. Also called promoter or activator.
Acetone
In the production of GRP parts, this solvent is mainly used to remove unhardened resin stains from equipment and personnel clothing. HIGHLY FLAMMABLE LIQUID
Aramid
aromatic polyamide fibres, the most widely used of which are Dupont Kevlar fibres.
Armour
Diagram showing the warp and weft yarns interlacing in a woven reinforcement. Several types of reinforcement are distinguished: unidirectional, taffeta weave, satin, twill, etc.
Bidirectional
Refers to a reinforcement in which one half of the fibres are arranged perpendicular to the other half. This scheme allows maximum strength to be obtained in both directions.
BMC / Pemix
Prefab moulding compound, composed by thermosetting resin, reinforcements, catalysts and fillers, for use in hot compression moulding, transfer moulding or injection moulding.
Bubbles
Air pockets enclosed in a laminate during processing. In a good quality part, the amount of bubbles does not usually exceed 1%.
Barcol hardness
Layered material hardness measure obtained by measuring a steel point penetration resitance under a spring action. The Barber-Coleman hardness tester allows a direct reading on a scale graduated from 0 to 100.
Binder
Resin applied to glass fibres in order to hold them in a mat (felt).
Benzoyl peroxide or BPO
Catalyst for use with aniline or hot type accelerators. Peroxides Category of compounds containing an unstable O-O (or O-OH) group: oxygen bonded to oxygen. They are used as initiators in the polymerisation of polyester resins.
Catalyst
In the field of unsaturated polyesters, a substance added to resins or gel coats in controlled amounts to cause gelling and cross-linking. The catalyst reacts with the accelerator, creating free radicals which in turn initiate polymerisation. (This term is often used by professionals to refer to free radical initiators such as PMEC. This usage is scientifically incorrect, as the peroxide is consumed during use. The term “initiator” would be more appropriate).
Centipoise
Hundredth paret of a poise or millipascal per second (mPa.s), a unit of measurement used to designate the fluid dynamic viscosity. Viscosity of water at 21 oC=1 cps (1 mPa.s)
Cobalt
It is used as an accelerator in cold-catalysed polyesters catalysed by methyl ethyl ketone hydroperoxides.
Craters
Small voids appearing on the gel coat surface, usually caused by foreign particles presence, air bubbles or pure catalyst small drops inside or on the gel coat surface and the laminate.
Curing
Polymerisation or irreversible transformation from the liquid to the solid state, with maximum physical properties, including hardness, obtained when the reaction is fully complete.
Curing at room temperature
Cross-linking at room temperature with the catalyst help, but without heat or pressure.
Cure
Transforming a resin into a hard solid by a chemical or physical process.
Cross-linking agent
Catalytic agent or reagent that causes addition by polymerisation when added to a resin. Also called “hardener” or catalyst.
Circular winding
Filament winding technique in which the rovings are placed on the mandrel at an 90° angle to the mandrel axis.
Continuous stratification
Process used to manufacture flat or corrugated panels and plates: cut, matted or felted yarns or glass fabrics are impregnated in a resin bath and placed between two cellophane sheets or similar films
Carbon fibre
Reinforcement fibre known for its low weight, high strength and high stiffness. Obtained by organic origin fibre pyrolysis in an inert atmosphere at temperatures above 980 oC. It can also be graphitised by heat treatment.
Cut thread
Uniform length fibres, usually between 0,75 mm and 50 mm, cut as continuous yarn or roving strands. Chopped strands not exceeding 3 mm lengths are called chopped strands.
Compression mould
Mould where the material to be moulded is placed when it is open and which allows it to be shaped by applying pressure and raising the temperature after it has been closed.
Contact moulding
Open mould layering process obtained manually or by simultaneous glass and resin spraying. Also known as low-pressure layering.
Core
Sandwich construction central part consisting of an inner skin and an outer skin. Commonly used materials are foam, honeycomb, paper or wood.
Casting resin
Unreinforced resin composed of polymers, fillers and additives. It is processed by casting.
Crocodile skin
Gel coat surface waviness and cracking with a crocodile skin appearance; usually caused by poor curing resulting from the attack of an insufficiently cross-linked area, by styrene or other solvent, contributed by a layer applied before or after this situation.
Cross-linking
Polyaddition process consisting by bridges formation between two polymer chains and the subsequent liquid transformation into a thermosetting solid.
Curing temperature
Temperature wich a product reaches its final hardening. Also, the temperature which a laminate is subjected to reach its final cure.
Heat-distortion temperature or HDT (Heat-distortion temperature or HDT)
Temperature which a test specimen undergoes a certain deformation under specified temperature and load conditions.
Curing time
Time required by the liquid resin to reach full cure after incorporation of the catalyst.
Download
Unwanted displacement of the gel coat film or resin during layering.
Degassing
Solvents vacuum release, volatiles and gases from composite parts.
Delamination
Separation of one or more laminate layers due to a layer adhesion lack or cohesion in relation to the others. This phenomenon may also occur between the gel coat and the laminate, or between a skin and the panel core
Dielectric
Non electricity conductor. The product ability to oppose the passage of an electric power.
Diethylaniline
Accelerator used with a BPO (benzoyl peroxide) catalyst or as a cobalt/PMEC co-promoter systems.
Diluent
In polyesters field, this term refers to the monomer dilution (usually the styrene monomer) which is fully involved in the polymerisation reactions. Caution: not to be confused with diluents which are used to reduce the polymer viscosity.
Dimethylaniline
Accelerator used with a BPO (benzoyl peroxide) catalyst. More active than diethylaniline. Dispersion Homogeneous mixture of solid particles suspended in a liquid medium.
Dispersion
Homogeneous solid particles mixture suspended in a liquid medium.
Distortion
Gel coat surface wavy reflection often observed in conjunction with fibre marking and usually caused by a layering system problem.
Draping
The fabric (or prepreg) ability to take the shape of a given surface.
Elastomer
Material wich has qualities that allow it to quickly recover its original shape and size, at room temperature, after having been subjected to a deforming force.
Effort
Internal resistance to size or shape variation. It is expressed in terms of force per unit area.
Elastic limit
Maximum stress that a material is able to withstand without permanent deformation remaining after stress removal and the material recovery.
EQF (MEK)
Methyl ethyl ketone abbreviatio. Flammable, colourless liquid, commonly used to clean guns. Not to be confused with PMEC (see PMEC).
Exothermic peak
Maximum temperature reached by the resin during the curing process.
ECCP
Methyl ethyl ketone peroxide abbreviation. A free radical source commonly used as an initiator (catalyst) for the polymerisation of unsaturated polyesters.
Fibreglass
fibres similar to wool or cotton fibres, but made from glass. Glass fibres comes in several options like: woven fabrics, yarns, felts, chopped fibres, chopped strands, rovings, woven rovings, etc.
Felt
fibrous product composed by interwoven fibres by mechanical or chemical action, pressure or heat. Felts may be made of cotton, glass or other fibres.
Filament
Basic yarn constituent element used in roving or other glass reinforcements manufacture. Filament thickness is measured in microns and can vary from 5 to 24 microns.
Fillet
A device used in filament winding to hold roving or other reinforcement bobbins in the desired position for unwinding.
Fluence
Part modification dimensions, over time, as a load (modification greater than the instantaneous elastic deformation) application result.
Fibre marking
Glass fibres traces visible through the gel coat film. Mat or Felt reinforcement composed by filaments, staple fibres or core yarns, chopped or continuous and held together by a binder. It is in the form of varying weight, width, thickness and length rolled layers.
Fish eyes
Gel coat film round craters, generally caused by silicone, oil, dust or water contamination, by a mould that has just been waxed or by a low viscosity of the gel coat. When this phenomenon is very intense, it is called gel coat “rejection” on the mould.
Free radicals
Highly reactive fragments of molecules capable of inducing chemical reactions, such as addition polymerisation of unsaturated polyester resins. Resin Natural or synthetic polymer products, solubilised or semi-solid, generally of high molecular weight and without a defined melting point. It is used as a base binder in PRVs to encapsulate and bind fibres.
Finishing coating
Finishing gel coat or surface coating applied to the finished part which polymerises without becoming tacky in contact with air.
Fumed silica
Thickening agent used in polyesters to increase their rheological qualities and sag resistance.
Fabric
textile material obtained by yarns interlacing (single, wired, twisted or roving) in two perpendicular directions or according to a given angle, being made during an operation with a loom or weaving machine.
Gel Coat / Gelled Putty
A coloured or transparent surface coating that enhances the aesthetics of the laminate and reinforces its protection. *In the field of resins, gel is defined as the stage of partial polymerisation in which a viscous liquid product becomes gelatinous and starts to turn into a solid.
Gel Coats
Special polyester products designed for the moulds production *In the resins field, gel is defined as the partial polymerisation state in which a viscous liquid product becomes gelatinous and starts to turn into a solid.
Gelification
Liquid to soft solid state tansition.
Grammage
Fibre reinforcement weight in relation to its unit area (width per length) (g/m2). Measurement used for belts, mats (felts) and fabrics.
Glass content
The amount of reinforcement contained in a composite material, usually expressed as a mass composite percentage by the reinforcement to matrix ratio. The ideal ratio is 40/60, i.e. 40 reinforcement to 60 resin.
Ground fibres
glass or carbon fibres, shredded in 0,75 to 1,5 mm lengths, which are used for fillers or BMC manufacture.
Glass fibre reinforced plastics (GRP)
General term for any composite material or part formed by a resin matrix and glass fibre reinforcement.
Gel time
Time perior during a polyester can be used after catalyst incorporation.
Heat cracking
Certain thermosetting or thermoplastic resins cracking due to excessive temperatures exposure or wide cyclic temperature variations.
Hardener
A substance that reacts with the resin to promote or control polymerisation. Also called catalyst.
Helical winding
A filament winding technique in which the fibre layer is inclined at a certain angle which is controlled by the yarn guide relative movement in relation to the mandrel rotation axis.
Hand contact moulding
Manual layering, as opposed to projection equipment use. Usually requires fabric and felt reinforcements.
Honeycomb
A structure consisting by closed or hexagonal cells, made of metal or reinforced resin, which is used as the core or web in sandwich constructions. The orientation of these structures is defined by the sheet thickness.
Impregnation
Reinforcement saturation by the resin. Generally, the saturation degree is determined visually and measured as a function of elapsed time.
Inclusion by casting
Encapsulation similar process, but taking steps to ensure complete penetration into all the object voids prior to the resin polymerisation. Inclusions are made with a clear resin such as Castro Resins 2195.
Inhibitor
Substance designed to slow down or prevent a chemical reaction; chemical additive that slows down or delays the cross-linking cycle.
Kevlar
Lightweight and strong aramid fibre patented by Dupont. Used as a reinforcement fibre.
Layer-Skin
First layer of the laminate adjacent to the gel coat. In general, its thickness should not exceed 1 mm to allow good impregnation and reduce the exotherm effects.
Loads
Relatively inert (organic or inorganic) solid compounds, which are added to resin or gel coat to obtain specific flow characteristics or to increase the volume and reduce the product cost.
Laminated plastics
Product formed by synthetic materials overlapping layers bonded together, usually by heat and pressure, to form a single piece.
Mandrel
An elongated mould around which resin-impregnated fibres, winding or webbing are wound into structural shapes or tubes.
Model
Initial shape used to make composite moulds.
Mould
Male or female (or both) shaped tool used to make parts per model.
Moulding
A process used to give a part the desired shape. In the case of polyesters, the most common techniques are contact moulding, compression moulding and injection moulding.
Monomer
A relatively simple product polymerising capable with itself or with another monomer. It can also be used to resin dissolve or dilute, e.g. polyesters.
NPG
Neopentylglycol
Ortho
Abbreviation for resins and gel coats based on orthophthalic acid or phthalic anhydride.
PAN
Basic product in the manufacture of certain carbon fibres.
Peel Ply
A fabric layer that is applied by contact at the end of a lamination process and removed from the polymerised laminate before assembly or gluing operations, or in further lamination case, in order to leave a slightly rough surface. With this fabric, laminators avoid sanding operations to ensure adhesion after several downtime days.
Plastics
Material that contains a polymer as a fundamental component and that, in some of its intermediate transformation phases, has fluid characteristics that allow it to be formed. Thermoplastic or thermosetting polymers with high molecular weights that can be processed by moulding, casting, extrusion or layering to produce various parts.
Polycondensation
Condensation reaction between one or more bifunctional products leading to a macromolecular product. Simple by-products (e.g. water) are formed during this reaction.
Polymerisation
A reaction which, from low molecular mass (monomers) molecules, forms high molecular mass (macromolecular) compounds by bonds between them.
Polymer
Large chemical chain consisting of numerous repeating groups, such as polystyrene.
Post-curing
Passing the hardened part through the oven after moulding. This is necessary with certain resins to obtain complete cross-linking and maximum mechanical properties.
Preform
Moulded reinforcement according to the part to be manufactured dimensions, made from staple fibres or by a mat (felt) or an compression-moulded mats (felts) overlay. It is used in hot moulding.
Pre-impreg
Resin-impregnated fabric, mat (felt) or filaments. They are present in sheets format, that can be stored for later use. The resin is often partially cross-linked in a non-sticky state called ‘B-state’. Additives may be added to obtain specific end-use properties and to improve their characteristics during processing, storage and handling.
Premix
Semi-finished product formed by consistent paste-like mixture containing resin, filler, pigment, etc. and catalyst suitable for hot working. Resin(s), pigment(s), filler(s) and catalyst(s) mixture, ready for moulding.
Promoter
See “Accelerator”.
Prototype
Testing part making process, which has not been designed for commercial release, but which establishes the design, composition and new product manufacturing parameters. It may require multiple trials before arriving at the final commercial design.
PRV (FRP)
See “Glass Reinforced Plastics”.
Pultrusion
Continuous manufacturing process for reinforced plastic profiles, whereby high unidirectional tensile strength is obtained by pulling continuous resin-impregnated yarns through a hot spinneret, followed, if necessary, by post-curing in an oven to treat the resin.
Punch
Mould male part.
Pigment exudation
Pigments (colours) surface appearance due to softening of the gel coat inner side after application of a layering resin or another gel coat (in two-colour parts case).
Phenolic resin
Thermosetting resin produced by condensation of an aromatic alcohol with an aldehyde, usually phenol with formaldehyde.
Plot
It is a woven reinforcement, yarns perpendicular to the warp. Antimony Trioxide is an additive used to improve the fire performance of polyester resins.
Quartet (Crocodile skin)
Gel coat surface waviness and cracking with a crocodile skin appearance; usually caused by poor curing resulting from the attack of an insufficiently cross-linked area, by styrene or other solvent, contributed by a layer applied before or after this situation.
Resin exudation
Liquid resin that appears on the surface, mainly during filament winding or RTM (Resin Transfer Molding).
Resin gap
Component gap in a gel coat layer, usually manifested by dark wavy lines presence.
Resin not inhibited by air
Resin whose polymerisation is not inhibited or interrupted by contact with air, generally due to the addition of a surface drying agent which insulates the surface of the resin from air (as opposed to conventional polyester resins, whose surface polymerisation is inhibited by contact with air).
Roving or Winding
Parallel base yarns grouping assembled without twisting. It is usually in the form of hanks, without other support, and may be hollow inside.
Resin transfer moulding
Resin injection moulding. According to this process, the catalysed resin is injected into a matrix mould in which the reinforcement has been pre-arranged. The mould and/or the resin may or may not be heated.
Roving fabric
Heavy fabrics woven from continuous yarn in roving form. They adapt well, impregnate quickly and allow a higher glass content to be achieved.
Sizing
Surface treatment applied to fibres or filaments to improve their cohesion and stiffness, to protect them against abrasion, to eliminate electrostatic charges and to improve the glass-resin bond.
Surface drying agent
A product (often a paraffin wax) that promotes polyester resins surface hardening in contact with air. If layering is to be continued on an already cured part, the presence of this agent may reduce adhesion and require sanding before further layering.
Styrene monomer
Unsaturated aromatic hydrocarbon used in plastics. Reactive diluent used in unsaturated polyesters.
Stratification
Reinforcement and resin placement in successive layers in a mould. It can be done manually or using a projection equipment.
Stratified
Product made by bonding layers together formed by resin-impregnated reinforcements. These layers may be associated with other materials for the sandwich panels manufacture.
Sandwich structure
Layering consisting of two GRP outer layers (glass reinforced polyester) and one or more intermediate layers such as honeycomb material, glass yarn fabrics or other lightweight materials.
Stings
Small air bubbles contained in the gel coat film. They are distinguished from porosity by their number (smaller) and their size (larger).
Skin
Layers corresponding to the outer layers associated with the core in a sandwich structure.
Simultaneous projection
A process in which glass fibres, resin and catalyst are deposited simultaneously in a mould. The roving is guided through a cutter and ejected into a resin stream directed into the mould. The catalyst and accelerated resin can be sprayed from one or two guns. The resin is then impregnated with glass and manually debubbled before cross-linking.
SISAL
white fibre produced from Indian agave or pita plant leaves. It is used as reinforcement, in the form of short staple fibres, and provides moderate shock resistance.
SMC
A ready-to-mould, glass-fibre reinforced, pasty polyester product in sheet form, mainly used in compression moulding.
Shallow veil
It is used to improve the part surface quality and prevent reinforcement fibres shapes apperance or underlying reinforcements (also called “surface mat”).
TBPB
Tertiary butyl perbenzoate abbreviation, which is used in high temperature polyester resin systems moulding.
Thermosetting and thermosetting
Thermosetting, a plastic that, when cured by heat or by other ways, transforms into a substantially infusible and insoluble product. Polymers formed by linkages extending in a three-dimensional network. Under the heat and a catalyst combined action, thermosetting polymers are chemically transformed into finished products that cannot melt or dissolve. This process is irreversible. Examples are unsaturated polyesters, epoxides and phenolics.
Thermoplastics
Capable of being successively softened by heating and hardened by cooling, within a temperature range characteristic of the plastic, and capable of being, in the softened state, repeatedly converted into objects by moulding, extrusion or forming. In contrast to thermosets, the transformation process is reversible. It is possible, by heating and cooling, to change the state and viscosity of thermoplastics. Examples: PET, PVC, nylon, etc.
Thixotropic
A product that is resistant to creep at rest or under reduced stress and that fluidises when agitated (when mixed, pumped or sprayed).
Thermal expansion coefficient
Dimensional variation of a material in response to a given unit temperature change.
Thixotropy Index / Rheological Index
Squeeze-out resistance indication which is calculated by dividing the low shear viscosity by the high shear viscosity.
Unmoulding
Part removal from a mould or an intermediate model.
Unsaturated polyester
Resin formed by the reaction between diacids and diols, one of which (monomers) forms compounds of high molecular mass (macromolecular) by means of bonds between them.
VARTM
Vacuum resin injection moulding. A process similar to RTM in which a vacuum is used to promote the distribution of the resin inside the mould.
Veil
Fibre fabric that fits and wets easily. It is particularly useful for forming a resin-rich barrier to improve corrosion resistance or to prevent fibres from becoming transparent.
Warping / Buckling
Defect usually characterised by fibre deformation rather than breakage. Polyvinyl alcohol (Polyvinyl alcohol-PVA) Water-soluble release agent.
Wax
Release agent or surface drying agent.
Water jet
Water jet used for trimming composite parts.
Wet winding
Filament winding in which the fibre yarns are impregnated with resin just before winding onto the mandrel.
Warp
Threads running lengthwise and perpendicular to the edge in a woven fabric.
Whitewashing
Dry, powdery appearance or deposit on the exposed surface of a gel coat.
Whisker
Short glass fibres formed by perfect crystals which, thanks to its structural perfection, have optimum mechanical characteristics. Due to the complexity of current manufacturing processes, their use is very limited.
Technical guides
In this document you will find the most suitable polyester or vinylester resin for a multitude of applications where chemical resistance is one of the key factors for the application.
We have an extensive range of resins available for applications with resistance to most acids, alkalis, alcohols, hydrocarbons, etc.
This document explains step by step how to make a composite mould with glass fibre reinforcement and low shrinkage polyester and vinylester resins.
This kind of moulds will be used to manufacture composite parts for a multitude of applications. In particular, this is the technique used to manufacture most of the moulds for the construction of sports boats, automotive parts, GRP furniture, etc.
An excellent handbook on composite materials, which serves as an excellent introduction to the composites industry. With this manual, written in English, you will learn the basics of the most commonly used thermosetting resins in the industry, reinforcing materials, as well as part and mould construction techniques.
It is a great tool for acquiring the knowledge that any professional or amateur must have in order to be able to carry out a multitude of works with these materials.
In this document you will find a composite parts manufacturing guide by infusion/vacuum technique using polyester resin and multi-axial glass fibres.
This document includes all Scott Bader products, that we distribute in Spain.
In this technical guide you will understand how to achieve a durable and effective bonding of bulkheads using high performance urethane-acrylate adhesive, Crestomer 1152PA.
This adhesive stands out for its excellent adhesion to all types of substrates: metals, composites, wood, etc., as well as for its excellent elongation in wide temperature ranges.
The main properties of RTV-2 silicone rubbers are described in this document. Its consistency, reactivity, its properties after vulcanisation and its cross-linking system are analyzed in general.
You will find safety and hygiene neccesary requirements for these products use and storage advice. The kind of equipment recommended for working with these silicones, preparation of the components, dosing and mixing, deaeration of the mass, application, processing and vulcanisation times, etc. are discussed.
In this document you will find the latest Scott Bader products success stories in applications for some of our customers.
The success stories of our Crestabond and Crestomer adhesives and Crestapol urethane-acrylic flame retardant resins are particularly noteworthy.
These materials find application in a multitude of sectors, including the automotive, nautical, wind blade manufacture and repair, and capital goods industries.
