DEGRADATION OF PLASTICS IN THE ENVIRONMENT - Plastics and Environmental Sustainability - page 232

Table 6.1 Most Damaging Range of Wavelengths in Sunlight for
Common Thermoplastics
Source: Data from Searle et al. (2010).
Plastic
materials

Cut-off
wavelength
(nm) a

Damaging
range (nm) b

Property of
interest

LDPE/
HDPE

<180 260-360 Optical density,

extensibility

PP <180 320-350 Tensile properties

~320 Yellowing

PVC <240 300-320 Yellowing

PS <270 ~280 Chain scission

~330 Yellowing

PC <280 310-340 Yellowing

Pape r c - 334-354 Yellowing

a Wavelength at 5% absolute transmission is commonly used as the cut-on
wavelength.

b The wavelength range as demarcated by activation spectra generated using a
series of cut-on filters and solar simulated radiation.

c Groundwood pulp (newsprint) paper is included for comparison. Paper data from
Andrady and Searle (1995).

6.2.5 Testing Plastics for Photodegradability

Weatherability of plastic materials can be investigated under natural or
accelerated laboratory exposure. Typically, standard ASTM (dog-bone
shaped) test pieces of the plastic of interest are exposed outdoors in natural
weathering exposure sites. Ideally, locations of high insolation (such as
AZ and FL) are selected to ensure fast degradation. The samples exposed
outdoors, usually on South-facing racks, are periodically removed and
tested to determine their extent of degradation.
Tensile extensibility is a particularly sensitive measure of the extent of
weathering. Alternatively, the development of carbonyl functionalities