chemiluminescence – a tool for determination of degree of oxidation of polymers + residual service...

Chemiluminescence – a tool for determination of degree of oxidation of

polymers

+

Residual service life

Jozef RychlýPolymer Institute

Dúbravská cesta 9, 843 42 Bratislava, Slovak Republic

Polyfriend workshop, september 5. 2013

What chemiluminescence is?


Chemiluminiscencia z disproporcionácie polymérnych peroxylových radikálov


Scheme of the light emission accompanying the oxidation of synthetic and natural polymers

secondary carbon atomsin the polymer chain

carbonyl, hydroxyl,carboxyl groups

oxidation

via hydroperoxides

oxidation

of their positions

terminal groups

of macromolecules

oxidation

via hydroperoxides

weak chemiluminescence from

peroxyl radicals recombination

heavily oxidized

products

bright chemiluminescence from

intermediate dioxetanes or similar

light emission precursors


Chemiluminescence (isothermal, non-isothermal) Chemiluminescence method is one of the supporting methods of investigation of development of oxidation degradation for a large spectrum of polymers (kinetic studies). The predictions of the remaining service life becomes more and more elaborated.The most of polymers studied so far giving a bright light emission when oxidized have in the vicinity of potentially formed hydroperoxidic group carbonyl, carbamido, carboxylic, alcoholic group; isolated hydroperoxides provide only weak light emissionThe chemiluminescence from polymers is pronounced when lower molar mass compounds are either present of being formed during oxidation process.It becomes also very important method in determination degradation progress of polymers where carbonyl groups are inherent part of the chain structure.


FTIR spectra of the polymers investigated


Instrumentation, 1968-2013, new instrument designed at the PISAS in 1968


http://www.lumipol.com/?page=zoom-lumipol3

Polyolefins and polydienes

CH2CH(

CH3

CH2CH

CH3

)n

polypropylene

CH2CH2CH2CH2( )n

polyethylene

CH2C CHCH2

CH3

( )n

poly(1,4-isoprene)

CH2CH CHCH2( )n

poly(1,4-butadiene)


Tertiary carbons + double bonds C=C

>

Double bonds

>

Tertiary carbons

>

Single C-C bonds


1000 10000 1000000

20000

40000

60000

80000

100000

120000

Inte

nsi

ty o

f CL,

cou

nts/

s/3

mg

time, s

Polyethylene

Polypropylene

Polyisoprene120 oC, oxygen

Polybutadiene

Porovnanie priebehov chemiluminiscencie z nasýtených a nenasýtených uhlovodíkových

polymérov (polyetylén a polybutadién) s polymérami majúcimi v hlavnom reťazci

terciárne uhlíky (polypropylén, polyizoprén)


The effect of initial molar mass PP, oxygen, 120 oC

0 10000 20000 300000

40000

80000

12000040 000

80 000

180 000

CL

inte

nsity

, co

unts

/s

time, s


Bábika, ako model prirodzeného starnutia polymérov 13. polyurethane ether foam foot ___________________________________________________________________________

15. PMMA tray

1. polystyrene hat

6. nylon ears and nose

7. PE scarf with carbon black

2.polystyrene head

5.silicone rubber tongue

6. nylon ears and nose

.3.acrylic hair 4.polypropylene sunglasses

10. low density polyethylene arms

8.polyethylene

terephthalate (PET) body

14.polyurethane ester foam foot

9.polycarbonate hands hand

11. nylon belt 12. nylon skirt


Inert atmosphere

By means of chemiluminescence we can detect the levels of hydroperoxides in polymers


Nonisothermal experiments

Polymer is heated according to pre-set programme as in DSC measurements


Polypropylene with fillers

50 100 150 200 250

0

500000

1000000

1500000

2000000

polypropylene(flame retardant)

polypropylene(mica reinforced)

polypropylene(talc reinforced)

polypropylene(calcium carbonatereinforced)

polypropylene(glass filled)

polypropylene(baryum sulfatereinforced)

polypropylene(homopolymer)

CL

inte

nsi

ty, c

ou

nts

/s/1

mg

temperature, oC


Conclusions

1. Chemiluminescence method is one of the most elegant method of investigation of development of oxidation degradation for a large spectrum of polymers (kinetic studies) and still brings to experimentators new surprises.

2. The main emphasis has been put on CL from oxidation of polyolefins and other polymers were somehow neglected.

3. The most of polymers studied so far were not characterized properly from the viewpoint of residual catalysts, defect structures, stabilizers, etc, which may be the source of conflicting data.

4. As we measure the light emission and any filter and/or absorber may modulate the observed light intensity we should be aware of some limitations; the combination with other methods is always necessary.


chemiluminescence – a tool for determination of degree of oxidation of polymers + residual service...

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