Binder
Definition
The polymer matrix that holds pigments in place and bonds the paint to the substrate. Identifies paint type (alkyd, acrylic, polyurethane, epoxy) and is the primary FTIR target.
- Function
- Holds pigments together and bonds paint to the substrate
- Primary analysis methods
- FTIR spectroscopy and Py-GC-MS
- Common types
- Alkyd, acrylic, epoxy, polyurethane, nitrocellulose, melamine-formaldehyde
Common questions
What does a binder do in paint?+
The binder is the polymeric component that holds pigment particles together and bonds the entire paint film to whatever surface it's applied to. It's what creates the paint's hardness, durability, and adhesion once the paint dries.
Why do forensic examiners care about the binder?+
The binder is the primary target for FTIR spectroscopy and Py-GC-MS analysis because its polymer composition is distinctive. Identifying the binder type can narrow the paint source and help link a sample to a vehicle, building, or product.
What are common paint binder types?+
Alkyd, acrylic, epoxy, polyurethane, nitrocellulose, and melamine-formaldehyde are the most common forensic binder types. Each produces a different chemical fingerprint and mechanical film.
Related terms
- PDQ
- Paint Data Query database (RCMP-maintained). Cross-referenced from glass work when a vehicle is identified through paired glass and paint evidence.
- Pigment
- Insoluble particles that give colour and opacity. Titanium dioxide (white), iron oxides (red/brown), carbon black (black), organic colorants (blues, reds). SEM-EDX reports...
- Alkyd Resin
- A polyester binder modified with fatty-acid chains from drying oils; cures by oxidative crosslinking and is characterised by FTIR ester carbonyl absorption...
- Basecoat
- The colour-bearing layer in automotive OEM paint; thin (10-30 µm), thermoplastic acrylic binder, contains colour and effect pigments.
- Clearcoat
- The transparent outermost layer of automotive OEM paint; thermoset acrylic-melamine, 40-60 µm, provides UV resistance and gloss.
- Cross-Section Mount
- Embedding a paint chip in resin, polishing to a flat face, and viewing under reflected light at 100 to 400 times magnification...
- E-Coat
- Electrocoat primer, the first layer applied to a clean steel/aluminium substrate via cathodic electrodeposition. Usually black, epoxy-based, near-universal on modern automotive bodies.
- Effect Pigment
- Aluminium flake or TiO2-coated mica used in metallic and pearlescent automotive finishes; identified by SEM morphology and EDS elemental composition.
- Electrocoat (E-Coat)
- The first layer in automotive OEM paint, applied by cathodic electrodeposition of an epoxy-amine coating onto the bare steel shell; 15-25 micrometres...
- ENFSI EPG
- Expert Working Group on Paint (European Network of Forensic Science Institutes); produced the European paint-examination protocol and promoted EUCAP development.
- Lacquer
- Clear or pigmented coating that dries purely by solvent evaporation (no chemical cure). Nitrocellulose and acrylic lacquers are the classic examples. Fast...
- Paint
- Pigmented liquid coating that dries to an opaque, coloured solid film. Built from four functional components: binder, pigment, solvent (vehicle), and additives.
Explained in these topics
- Paint Composition, Types and Binder ChemistryThe polymeric film-forming component of a paint formulation; determines mechanical and chemical film properties and provides the primary FTIR and Py-GC-MS fing...
- Paint Evidence: Layers, Coating Structure and Instrumental AnalysisThe polymer matrix that holds pigments in place and bonds the paint to the substrate. Identifies paint type (alkyd, acrylic, polyurethane, epoxy) and is the pr...
- Paint, Lacquer and Varnishes: Nature, Composition and Forensic ExaminationPolymeric component that holds pigment in place and forms the dried film. Common binders: alkyd, acrylic, epoxy, polyurethane, nitrocellulose, melamine-formald...