Tampa BSides - Chef's Tour of Microsoft Security Adoption Framework (SAF)
Ultraviolet protection finishes
1.
2.
3. Longterm exposure to UV light can result in
Acceleration of skin ageing,
Photodermatosis (acne),
Phototoxic reactions to drugs,
Erythema (skin reddening),
sunburn,
increased risk of melanoma (skin cancer),
Eye damage (opacification of the cornea)
DNA damage.
4. Solar radiation striking the earth’s surface is composed of light
waves with
wavelengths ranging from the infrared to the UV
5. Although the intensity of UV radiation is much
less than
visible or infrared radiation,
the energy per photon is significantly higher.
The very high energy of the UV-C photons is
mostly absorbed by
ozone in the higher regions of the atmosphere
decreasing their relative intensity on the earth surface to
almost zero.
But the energies of UV-A and UV-B photons that
reach the earth surface exceed the
carbon–carbon single bond energy of 335 kJ mol–1,
which is why UV radiation can be used to initiate chemical
reactions.
6. The actual damage to human skin from UV
radiation is
a function of the wavelength of the incident radiation,
with the most damage done by radiation less than 300
nm.
If this erythemal effect is multiplied
by the intensity of the incident solar light, as a function
of wavelength,
The wavelengths of maximum danger to skin are 305–
310 nm.
Therefore, to be useful in protecting the
wearer from solar UV radiation,
textiles must demonstrate effectiveness in the 300–320 nm
range.
7. The SPF is the ratio of the potential erythemal
effect (skin reddening),
to the actual erythemal effect transmitted through the fabric
by the radiation
and can be calculated from spectroscopic measurements.
The larger the SPF,
the more protective the fabric is to UV radiation
In Europe and Australia, the SPF is referred
to as the ultraviolet protection factor (UPF).
The SPF is also used with so-called ‘sun blocking’
skin creams,
giving a relative measure of how much longer a person can be
exposed to sunlight before skin damage occurs
8. Typically, a fabric with an SPF of > 40 is
considered to provide
excellent protection against UV radiation
(according to AS/NZS 4399: Sun protective clothing –
Evaluation and classification, Standards Australia, Sydney).
It is possible to realise about 80 % of the
theoretical maximum of SPF 200.
Industrial fabrics designed for
awnings,
canopies,
tents and
blinds may also benefit from a UV-protective treatment.
9. Since the most probable time for long-term
solar exposure is in the summer, the most
likely candidates for UV protective finishes
are
◦ lightweight woven and knitted fabrics intended for
producing
shirts,
blouses,
T-shirts,
swimwear,
beachwear,
sportswear, and the like.
10. When radiation
strikes a fibre
surface, it can be
reflected,
absorbed,
transmitted
through the fibre or
pass between fibres
11. The relative amounts of radiation reflected,
absorbed or transmitted depend on many
factors, including the
1) fibre type,
2) the fibre surface smoothness,
3) the fabric cover factor (the fraction of the
4) surface area of the fabric covered by yarns) and
5) the presence or absence of fibre delustrants,
6) dyes and UV absorbers.
The effect of fibre type on the SPF of undyed
fabrics of similar construction is
demonstrated
12. Cotton and silk fibres offer
little protection to UV radiation since the radiation can
pass through without being markedly absorbed.
Wool and polyester, on the other hand, have
significant higher SPFs since these fibres will absorb
UV radiation.
Nylon falls in between these extremes. One
factor influencing nylon and polyester
absorbance is
the presence of the delustrant TiO2,
a material that strongly absorbs UV radiation
13. If the fibres absorb all
of the incident
radiation,
then the only source
of transmitted rays is
from the spacing
between the yarns.
By definition, the
theoretical maximum
SPF is the reciprocal of
1 minus the cover
factor.
Using a SPF value of 50
as the goal,
a fabric with a cover
factor of 0.98
And composed of
fibres that absorb all of
the non-reflected UV
radiation
will provide its wearer
with excellent
protection against
solar UV radiation.
14.
15. Of course, tight micro-fibre fabrics provide a
better UV protection than fabrics made from
normal sized fibres
with the same specific weight
and type of construction.
Many dyes absorb UV radiation as well as
visible light. A cotton fabric dyed
to a deep shade can achieve SPF values of 50 or higher just
from the presence of the dye
16. Since fashion and comfort often dictate the
use of
lightly coloured fabrics for summer apparel,
the need arose for UV absorbing materials
that could be applied to fibres to provide the
desired SPF values in light shades.
Dyestuff and auxiliary manufacturers have
responded by developing
a variety of materials suitable for use as UV protection
finishes.
17.
18.
19. The requirements for a material to be
effective as a UV protection finish include
efficient absorption of UV radiation at 300–320 nm,
quick transformation of the high UV energy into the
vibration energy in the absorber molecules
and then
into heat energy in the surroundings without photo
degradation.
Further requirements are
convenient application to textile fibres
and lack of added colour for the treated fibre.
20.
21. The reversible chemical reaction, induced by
UV absorption
of hydroxy-phenyl structures of UV absorbers,
22. By careful choice of substituents, molecules
can be formed that have
the required absorbance of UV radiation,
lack of added colour
and the necessary affinity to fibres
and fastness.
In most cases, the UV absorber is applied
with
the dyes during the dyeing process.
Several possible application methods are
described by
Haerri
and Haenzi.
23.
24. Several organisations around the world have
developed or have proposed performance
standards for UV protection fabrics. These
organisations and their standards are
summarised in Table
25. Although there are multiple standards
for UV protective fabrics,
there are significant differences between
the various organizations.
The particular standard for the intended market area should
be consulted during
fabric development.
Before the development of instrumental methods, SPF values
of fabrics were determined by
irradiating human subjects
and measuring the critical amount of radiation necessary to cause skin
reddening at a particular wavelength with
And without wearing the fabrics.
Fortunately, several methods are now available that do not
result in a sunburned participant. These methods all
determine
the transmittance of UV radiation through fabrics
and calculate the SPF value using standard charts for the solar spectrum
and the erythemal effect.
UV Standard 801 considers in addition the effects of usage of
the finished textiles that normally reduce the UV protection
26. UV absorbers have the same need for wash fastness and light fastness as dyestuffs.
Laundering trials should be carried out with all new formulations to confirm that the claimed
UV protection is actually active during the life of the garment.
One concern is specific to the use of UV absorbers in combination with optical brightening
agents (OBA).
These brightening agents function by absorbing UV radiation and re-emitting visible light.
If a UV absorber is also present in the fibre, the brightening effect from the OBA can be greatly
diminished or even absent.
Proper choice of an appropriate OBA can minimise this problem.
In most other cases combination with other finishes does not reduce the UV protection.
A two-step application is necessary if the pH values of the UV protection finish bath and that
of the other finishes are very different.
The UV protection finish should be applied first. Problems may arise from limited bath uptake
after a repellent finish or after calendering
