Volkswagen ID.4: Distinction of types of plastic

Plastics are classified into thermoplastics, thermosets and elastomers based on their chemical structure and behaviour when heated.

Thermoplastics and thermosets are often used in the automotive industry.

Elastomers are currently used to a limited extent in the automotive industry.

In addition, composite materials are used in the automotive industry.

Identification

Most plastic attachments are marked with a standard code -5-.

The standard code -5- indicates the composition and is located on the inside of the plastic attachment.

Important

• To view the standard code -5-, it may be necessary to remove the plastic attachment.

The standard code -5- indicates the type of plastic, additives or strengtheners. The standard code -5- consists of the symbol ">", an abbreviation for the type of plastic and ends with the symbol "<". The abbreviations stand for:

• Base polymer
• Special characteristics
• Type, properties and strengthener content

Base polymer

Designates the polymer or polymer blend from which the plastic attachment was manufactured.

For polymer blends, the individual polymers are separated by the symbol "+" and are indicated in descending order by their mass fraction.

Example >PP+EPDM<: A blend consisting of polypropylene (PP) and ethylene propylene diene rubber (EPDM). The main component is polypropylene.

All vehicles (continued)

Special characteristics

Special characteristics of a base polymer, such as foamed, chlorinated, high strength or low density, are indicated after the base polymer separated by a hyphen ("-").

Example: >PE-HD<: A high-density (HD) polyethylene. Abbreviations of the special characteristics can also be indicated after the actual polymer, e.g. >HDPE<.

All vehicles (continued)

Type, properties and strengthener content

Strengthener additives are indicated with 1 or 2 letters after the polymer. The letters are separated from the base polymer by a hyphen "-". The first letter refers to the type of additive and the second letter refers to the properties of the additive.

Abbreviations of additives, strengtheners and properties:

Plastic reinforced with glass fibres is marked with the letters "GF" and the mass fraction of the additive.

Example >UPGF30<: Unsaturated polyester (UP) containing 30 % of glass fibres as a strengthener.

All vehicles (continued) Talcum is another additive. Talcum is marked with the letter "T" or "TD", talcum in powder form.

Example >PP-T10<: Polypropylene (PP) containing 10 % of talcum as a strengthener.

All vehicles (continued)

Thermoplastic

Thermoplastics are a brittle or viscoplastic plastics at normal temperature that can soften and be deformed when heated.

After cooling, thermoplastics solidify and regain their original properties.

When thermoplastics come into contact with solvents, they can dissolve or swell.

Important

• When thermoplastics are welded, the material must be determined to identify the appropriate welding rod material and the welding temperature.

When welding, a higher mechanical strength can be achieved compared to bonding. It is recommended to weld fractures and cracks in thermoplastics.

Properties and areas of application:

Designation/ Abbreviation:

Polyethylene/ PE

Properties:

• excellent electrical properties
• high resistance to water and humidity
•  low temperature resistance

Areas of application:

Fuel tank, wheel housing trims, bumper cover, air ducts

Designation/ Abbreviation:

Polypropylene/ PP

Properties:

• high chemical resistance
• good mechanical and electrical properties
• higher thermal stability compared to polyethylene

Areas of application:

Bumper cover, headlight housing, wheel housing liners, battery housing, housing of heater and air conditioning unit

Designation/ Abbreviation:

Acrylonitrilebutadiene styrene/ ABS

Properties:

• high stiffness, surface hardness and toughness
• addition of metal coating and glass fibres possible

Areas of application:

Air ducts, wheel trims, sun visors, exterior mirror housing

Designation/ Abbreviation:

Polyamide/ PA

Properties:

• high resistance against material fatigue
• high impact and abrasion resistance
• good mechanical characteristics
• reinforcement with glass fibres possible

Areas of application:

Air ducts, wheel trims, exterior mirror housing

Designation/ Abbreviation

Polycarbonate / PC

Properties:

• high stiffness, toughness and impact resistance
• transparent in its original state

Areas of application:

Bumper cover, spoiler, air ducts, headlight

Designation Abbreviation:

PP and PE copolymer/ P/E

Properties:

• by adding ethyl, polypropylene achieves a significantly higher impact resistance

Areas of application:

Bumper cover

Designation / Abbreviation

Acrylic-styrene- acrylonitrile/ ASA

Properties:

• high strength and surface hardness

Important

• acrylic-styrene- acrylonitrile must not be welded

Areas of application:

Air ducts, exterior mirror housing

Thermosetting plastics

Thermosetting plastics are brittle and viscoplastic plastics that do not soften or melt when heated. After exceeding the decomposition temperature, thermosetting plastics decompose and carbonise without changing shape.

When thermosetting plastics are subjected to a sufficiently high external force, their higher stiffness results in immediate material fracture without prior deformation.

Thermosetting plastics have a high resistance to chemicals, so they hardly swell and do not dissolve in solvents.

Important

• Due to their properties, thermosetting plastics may only be bonded for repairs.

Properties and areas of application:

Designation /Abbreviation:

Epoxy resin / EP

Properties:

• excellent adhesion to plastics
• addition of strengtheners possible

Areas of application:

Adhesives for plastic repairs

Designation /Abbreviation:

Unsaturated polyester2)/ UP

Properties:

• excellent mechanical characteristics
• high resistance to chemicals
• often reinforced with glass fibres

Areas of application:

Bumper cover, grille, flaps, exterior attachments of commercial vehicles

Elastomers

Elastomers are characterised by a high elasticity over a wide temperature range.

Elastomers deform when pressure is applied from the outside.

Without pressure, elastomers return to their original shape.

When elastomers are heated, they become soft but do not melt.

When the decomposition temperature of elastomers is exceeded, they decompose or carbonise.

Important

• Due to their properties, elastomers may only be bonded for repairs

Polyurethane and ethylene propylene diene rubber are the elastomers most commonly used in the automotive industry.

Polyurethane

Polyurethane (PUR or PU) can have different chain structures depending on the manufacturing process and can be a thermoplastic, thermosetting plastic or elastomer.

Elastomers can be produced as a foam and are suitable as a reinforcement in bumper covers, dash panels or steering wheels.

Ethylene propylene diene rubber:

Ethylene propylene diene rubber s(EPDM) is often used in the production of bumper covers in combination with polypropylene or polypropylene copolymer and polyethylene to achieve a higher elasticity and impact resistance.

1. Not assigned
2. Unsaturated polyester, generally reinforced with glass fibres, is rarely used in the automotive industry.