Hexafluoropropene, oxidized, oligomers, reduced, fluorinated

Stability: thermal, sunlight, metals

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

thermal stability

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

1994

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

data from handbook or collection of data

Remarks:

The data source is a publication which describes perfluoropolyethers (PFPEs) from the point of view of their synthetic chemistry, properties, derivatives, and applications. The data source is considered authoritative altough no many details on test methods are provided.

Reason / purpose for cross-reference:

reference to same study

Principles of method if other than guideline:

not reported

GLP compliance:

no

Test substance thermally stable:

yes

Operating temp.:

> 350 °C

Test substance stable to sunlight:

not determined

Test substance stable to metals / metal ions:

not determined

Conclusions:

GALDEN LMW, as other PFPE fluids, possess high thermooxidative stability.

Executive summary:

The scope of the publication was to analyse and describe perfluoropolyethers (PFPEs) from the point of view of their synthetic chemistry, properties, derivatives, and applications.

The focus of the publication is on PFPEs fluids commercially named FOMBLIN (both with linear and branched chemical structures) and GALDEN (branched structure) and the information gleaned from first-hand experience are reported. FOMBLIN fluids and GALDEN fluids belong to the same class of PFPEs since GALDEN fluids represents the low molecular weight fraction of branched FOMBLIN fluids.

According to the publication the thermooxidative stability of PFPEs is outstanding and perhaps is their hallmark. It is reported that thermogravimetric analysis (TGA) of FOMBLIN fluids shows onset of decomposition at temperature exceeding 350°C and the independent isoteniscope method gives similar values. Both methods indicate little dependence on molecular weight.

TGA in oxygen reveals a modest shift, approximately 10°C to lower temperatures, consonant with the notion that radical abstractions induced by O2 in hydrocarbons have little relevnce in PFPE chemistry.

The presence of metals and oxygen negatively influence decomposition temperature as a function of metal and fluid structure. In the most reactive combiation branched FOMBLIN-titanim/aluminium alloy and linear FOMBLIN-aluminium, the TGA-determined threshold temperatures in oxygen reduce to 325 and 270 °C, respectively. The grater susceptibility of linear PFPEs (FOMBLIN Z fluids) was verified by the microoxidation test, whereby aggressive metal/oxygen combinations reduce operating temperatur to 240°C – 260°C in linear PFPEs (FOMBIN Z and FOMBLIN M) and 315°C in branched PFPE (FOMBLIN Y). Additives show a prophylactic influence on this behaviour. During thermal or methal/oxygen induced decomposition, volatile gases containing perfluoroolefin plus toxic COF2 and CF3COF are evolved, hence in opne systems undecomposed PFPE fluid retains its physical propertiees.

GALDEN LMW belong to the PFPE chemical class discussed in the publication and it represents the low molecular weight fraction of GALDEN fluids. Being the thermal stability little dependent on molecular weight it can be conlcuded that GALDEN LMW, as other PFPE fluids, possess high thermooxidative stability.

Reference 2

Endpoint:

thermal stability

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

weight of evidence

Justification for type of information:

REPORTING FORMAT FOR THE ANALOGUE APPROACH

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
The hypothesis is that, basing on the structural similarity, experimental data on H-GALDEN can be used in order to get information on the biological behaviour of GALDEN LMW and on certain type of physical-chemical properties. Basing on available data, the source is anticipated to be a worst-case.
The hyphotesis is developed further in the attached "The Read-Across Justification Document".

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
Target = GALDEN LMW // Source = H-GALDEN
Information on identity, purity and impurities of target and source chemicals is detailed in the attached "The Read-Across Justification Document".

3. ANALOGUE APPROACH JUSTIFICATION
The approach is justified by the structure similarity between GALDEN LMW and H-GALDEN which are both fluoroethers and characterized by the presence of the C-F bond in their entire carbon chains with the exception of the terminal groups in H-GALDEN.
Both the C-F and ether bonds participate in giving the fluoroethers their typical properties in term of thermal and chemical stability but the C-F bond in particular is recognized to increase the stability of the structure. As the C-F bond constitutes the main backbone of the two structures, GALDEN LMW and H-GALDEN are anticipated to have similar stability in term of ignition and thermal degradation. H-GALDEN may eventually represent a worst case for physicochemical read across due to the presence of the hydrogen atom in the terminal groups of the molecule (the bond C-H is weaker than the bond C-F) which may make H-GALDEN more sensitive to ignition and thermal degradation than GALDEN LMW.

The use of the information available on H-GALDEN for reading across to GALDEN LMW is considered justifiable as the Thermal stability endpoint is not part of the standard REACH requirement but it is considered relevant for the description of GALDEN LMW profile as thermal stability is one of the typical features of perfluoropolyethers. The thermal stability range of GALDEN LMW is estimated basing on a WoE approach which considers both the available experimental data on perfluoropolyethers having the same chemical structure as GALDEN LMW but higher molecular weights and on experimental data available on H-GALDEN. The results are consistent showing that H-GALDEN and the perfluoropolyethers of the same chemical class as GALDEN LMW are stable in the same temperature range. According to literature the degradation temperature of perfluoropolyethers has little dependence on molecular weight. All this information is considered suitable for estimating the thermal stability range of GALDEN LMW.

The analogue approach justification is discussed in the attached "The Read-Across Justification Document".

4. DATA MATRIX
The data matrix is reported in the attached "The Read-Across Justification Document".
----------------

The Read-Across Justification Document is attatched. It is developed according to Read-Across Assessment Framework (RAAF) (ECHA, 2017) and the complementary guidance on considerations on multi-constituent substances and UVCBs (ECHA, 2017)

Reason / purpose for cross-reference:

read-across source

Test substance thermally stable:

yes

Key result

Operating temp.:

> 30 - < 350 °C

Remarks on result:

other: no thermal effects observed

Conclusions:

No thermal effects were observed on H-GALDEN under the experimetal conditions, in the range temperature of 30-350 °C.
Based on Read Across with H-GALDEN, it can be affirmed that GALDEN LMW is stable in temperature range 30 - 350 °C.

Executive summary:

The thermal stability of the analogue substance H GALDEN was assessed by accelerating rating calorimetry (ARC) analysis according to ASTM method No. E 1981.

The ASTM method No. E 1981 covers suggested procedures for the operation of a calorimetric device designed to obtain temperature and pressure data as a function of time for systems undergoing a physicochemical change under nearly adiabatic conditions.

A standard test was performed in the temperature range 30 -350 °C, the standard test included phases of heating (5 °C), waiting (15 minutes) and research of exothermic effects.

No thermal effects were observed under the experimental conditions, H GALDEN is stable in temperature range 30 - 350 °C.

H-GALDEN is a hydrofluoropolyether with similar chain structure and similar molecular weight of GALDEN LMW. The differences between the two substances are the monomer units (the monomer unit in H-GALDEN is (C2F4O) while the monomer unit of GALDEN LMW is (C3F6O) ) and the presence of a single hydrogen atom segregated in the terminal groups of the molecule H-GALDEN.

Basing on the structural similarity, experimental data on H-GALDEN can be used in order to get information on physical-chemical properties and biological behaviour of GALDEN LMW. 

It should be noted that the presence of –OCF2H as terminal groups in H-GALDEN, gives to the product slight more reactivity and more polarity than those observed for GALDEN, characterised by neutral, non functional terminal groups –OCF3.

Because of the presence of –OCF2H as terminal groups in H GALDEN, which gives to the product more reactivity and more polarity than those observed for GALDEN LMW, the reported read across represents a worst case approach.

In conclusion, it can be affirmed that GALDEN LMW is stable in temperature range 30 - 350 °C.

Reference 3

Endpoint:

thermal stability

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

weight of evidence

Justification for type of information:

REPORTING FORMAT FOR THE ANALOGUE APPROACH

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
The hypothesis is that, basing on the structural similarity, experimental data on H-GALDEN can be used in order to get information on the biological behaviour of GALDEN LMW and on certain type of physical-chemical properties. Basing on available data, the source is anticipated to be a worst-case.
The hyphotesis is developed further in the attached "The Read-Across Justification Document".

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
Target = GALDEN LMW // Source = H-GALDEN
Information on identity, purity and impurities of target and source chemicals is detailed in the attached "The Read-Across Justification Document".

3. ANALOGUE APPROACH JUSTIFICATION
The approach is justified by the structure similarity between GALDEN LMW and H-GALDEN which are both fluoroethers and characterized by the presence of the C-F bond in their entire carbon chains with the exception of the terminal groups in H-GALDEN.
Both the C-F and ether bonds participate in giving the fluoroethers their typical properties in term of thermal and chemical stability but the C-F bond in particular is recognized to increase the stability of the structure. As the C-F bond constitutes the main backbone of the two structures, GALDEN LMW and H-GALDEN are anticipated to have similar stability in term of ignition and thermal degradation. H-GALDEN may eventually represent a worst case for physicochemical read across due to the presence of the hydrogen atom in the terminal groups of the molecule (the bond C-H is weaker than the bond C-F) which may make H-GALDEN more sensitive to ignition and thermal degradation than GALDEN LMW.

The use of the information available on H-GALDEN for reading across to GALDEN LMW is considered justifiable as the Thermal stability endpoint is not part of the standard REACH requirement but it is considered relevant for the description of GALDEN LMW profile as thermal stability is one of the typical features of perfluoropolyethers. The thermal stability range of GALDEN LMW is estimated basing on a WoE approach which considers both the available experimental data on perfluoropolyethers having the same chemical structure as GALDEN LMW but higher molecular weights and on experimental data available on H-GALDEN. The results are consistent showing that H-GALDEN and the perfluoropolyethers of the same chemical class as GALDEN LMW are stable in the same temperature range. According to literature the degradation temperature of perfluoropolyethers has little dependence on molecular weight. All this information is considered suitable for estimating the thermal stability range of GALDEN LMW.

The analogue approach justification is discussed in the attached "The Read-Across Justification Document".

4. DATA MATRIX
The data matrix is reported in the attached "The Read-Across Justification Document".
----------------

The Read-Across Justification Document is attatched. It is developed according to Read-Across Assessment Framework (RAAF) (ECHA, 2017) and the complementary guidance on considerations on multi-constituent substances and UVCBs (ECHA, 2017)

Reason / purpose for cross-reference:

read-across source

Qualifier:

according to guideline

Guideline:

other: ASTM E 537-98

Deviations:

no

Test substance thermally stable:

yes

Key result

Operating temp.:

> 30 - < 280 °C

Remarks on result:

other: Atmosphere: Air - No thermal effects observed.

Sublimation:

no

Transformation products:

no

Conclusions:

No thermal effects were observed on the analogue substance H GALDEN under the experimetal conditions, both in presence of air and in presence nitrogen, therefore H GALDEN is stable in temperature range 30 - 280 °C.
Based on Read Across with H-GALDEN, it can be affirm that GALDEN LMW is stable in temperature range 30 - 280 °C.

Executive summary:

The thermal stability of the analogue substance H GALDEN was tested by differential scanning calorimetry (DSC) according to ASTM method No. E 537.

The test method describes the ascertainment of the presence of enthalpic changes in a test specimen, using minimum quantities of material, approximates the temperature at which these enthalpic changes occur and determines their enthalpies (heats) using differential scanning calorimetry or pressure differential scanning calorimetry.

Test was performed both in presence of air (static air remained in the crucible) and in presence of nitrogen, in the temperature range 30 -280 °C.

No thermal effects were observed under the experimetal conditions, both in presence of air and in presence nitrogen: H GALDEN is stable in temperature range 30 - 280 °C.

H-GALDEN is a hydrofluoropolyether with similar chain structure and similar molecular weight of GALDEN LMW. The differences between the two substances are the monomer units (the monomer unit in H-GALDEN is (C2F4O) while the monomer unit of GALDEN LMW is (C3F6O) ) and the presence of a single hydrogen atom segregated in the terminal groups of the molecule H-GALDEN.

Basing on the structural similarity, experimental data on H-GALDEN can be used in order to get information on phisico-chemical properties and biological behaviour of GALDEN LMW. It should be noted that the presence of –OCF2H as terminal groups in H-GALDEN, gives to the product slight more reactivity and more polarity than those observed for GALDEN, characterised by neutral, non functional terminal groups –OCF3.

Because of the presence of –OCF2H as terminal groups in H GALDEN, which gives to the product more reactivity and more polarity than those observed for GALDEN LMW, the reported read across represents a worst case. In conclusion, it can be affirm that GALDEN LMW is stable in temperature range 30 - 280 °C.

Description of key information

Basing on thermal stability test results on the analogue substance H GALDEN and on literature data for the perfluoropolyethers chemical class which GALDEN LMW belongs to, it can be affirm that GALDEN LMW is stable in the temperature range 30-350 °C.

Additional information

H-GALDEN is a hydrofluoropolyether with similar chain structure and similar molecular weight of GALDEN LMW. The differences between the two substances are the monomer units (the monomer unit in H-GALDEN is (C2F4O) while the monomer unit of GALDEN LMW is (C3F6O) ) and the presence of a single hydrogen atom segregated in the terminal groups of the molecule H-GALDEN.

Basing on the structural similarity, experimental data on H-GALDEN can be used in order to get information on physico-chemical properties and the biological behaviour of GALDEN LMW. Moreover the presence of –OCF2H as terminal groups in H-GALDEN gives to the product slight more reactivity and more polarity than those observed for GALDEN, characterised by neutral, non functional terminal groups –OCF3 and therefore the reported read across represents a worst case.

The thermal stability of H-GALDEN was tested both by differential scanning calorimetry (DSC) analysis in presence of air and nitrogen in the temperature range 30 - 280 °C and by accelerating rating calorimetry (ARC) analysis in the temperature range 30 - 350 °C. Both the tests were performed according to recognized international standard methods. No thermal effects were observed under the experimental conditions, H-GALDEN is stable in the tested temperature ranges.

The literature data report the high thermal stability of the perfluoropolyether class which GALDEN LMW belongs. The thermal stability is supported by the results from a thermogravimetric analysis and an isoteniscope analysis performed on some PFPE fluids having the same chemical structure but higher molecular weight of GALDEN LMW.

According to the publication the thermooxidative stability of PFPEs is outstanding and it has little dependence on molecular weight. Some PFPE fluids having the same chemical structure of GALDEN LMW but higher molecular weight were tested showing thermal decomposition at temperatures exceding 350 °C.

Basing on the above , it can be affirm that GALDEN LMW is stable in the temperature range 30-350 °C.

Justification for classification or non-classification

The thermal stability of GALDEN LMW is not critical. No classification required.