Plastics

non-cross-linked polyethylene (PE non cross-linked)

General information

Description

Non-cross-linked PE only exists as foam. It can be produced as block, sheet, or in a mould. Non-cross-linked PE has a somewhat coarse, irregular cell structure with closed cells that sometime look a bit bubbly. It is a rigid foam that is not really compressible (deformations remain when pressed hard). Non-cross-linked PE can feel (somewhat) waxy, unlike cross-linked PE foam is can abrade a little. Being a PE foam it can release a smell of old Tupperware or old plastic bags upon ageing.

History

Non-cross-linked PE foams have been commercially available since World War II.

Production, Application, Appearance

Non-cross-linked PE is less expensive than cross-linked PE. Usually non-cross-linked PE is available in 0.3–10 cm sheets. Several sheets can be adhered together. It has a variety of applications, well-known are the swimming noodles. Also many packaging and insulation materials are made of non-cross-linked PE.

Properties

Material properties

Thermoplastic
Density: foam: ~0.025-0.145 g/cm3
Melting point: 99-138°C
Glass transition temperature: -59 to -133°C

Identification properties

Cell structure (foam): closed - large / closed / irregular cell structure
Smell: old Tupperware or old plastic bags
Touch: waxy
Sound: foam = no characteristic sound
UV-radiation (when clear): not applicable
Polarizing filters (for clear PE): not applicable

Degradation

Process

Photo-oxidation, soiling (electrostatic).

Details

PE non-cross-linked is not considered a problem plastic.

Symptoms

Discolouration, surface turns matte, loss of mechanical properties resulting in tears and fractures, dimensional changes.

Susceptibility

UV-radiation: High
Light: Medium
Oxygen/Ozone: Medium
Temp: Low
RH: Low

Preventive conservation

Recommendations

UV-RADIATION: keep below 10 µW/lm Exclude UV with filters or no-UV light source
LIGHT: 1 just noticeable change in approx. 30 Mlx.h Moderate light dose - control intensity and exposure time
OXYGEN / OZONE: lower temperature slows down oxidation
TEMP: common indoor conditions 10-30°C
RH: common indoor conditions 30-70% RH fluctuations: setpoint ±20%