Download New biocomposites based on bioplastic flax fibres and

Supplementary Material
'
PLA
''
1184
Dielectric function
Absorption coefficient
1755
1091
IR reflectance spectra of PLA composites reinforced with flax fibres in the ranges 1100 –
3000 and 500 - 900 cm-1 are similar to that of pure PLA blends. Some bands show a small
shift in their wavenumbers, but it does not exceeded 2 cm-1. Both measured parameters,
absorption coefficient and dielectric functions vs. wavenumbers (Fig. 1 supp) exhibit similar
patterns of lines in their shape and energy position for all studied samples. However, clear
changes are seen when the relative intensity of absorption coefficient is compared. The
intensity ratio of bands at 1755 cm-1 which correspond to the stretching (C=O) vibrations of
the carbonyl group of lactic unit and 1091 cm-1 or 1184 cm-1, both assigned to two (C-O-C)
vibrations of the –C(=O)-O-CH2- system for PLA, PLA+wt and PLA+M50 samples are 1.00,
0.95, 0.92, or 1.00, 0.91 and 0.95, respectively. The decrease in the intensity of the
stretching (C=O) vibrations of the carbonyl group in composite might suggests hydrogen
bond formation of this group with cellulose polymer from fibres. In summary the reflectance
IR spectra of PLA and two studied composites (Fig. 1 supp) does not provide clear evidence
for the hydrogen bond interactions between composite components but the decrease in
relative band intensity of the (C=O) vibrations at 1755 cm-1 in relation to other bands of this
region might suggest on it.
PLA
PLA+wt
'
PLA+wt
''
'
PLA+M50
''
PLA+M50
2000
1800
1600
1400
1200
1000
-1
Wavenumber / cm
800
600
2000
1500
1000
Wavenumber / cm
1
500
-1
Fig. 1 supp. Absorption coefficients and dielectric functions derived from the reflectance
FTIR spectra of PLA, PLA+wt, PLA+M50.
The suggestion is partially supported by changes of the spectral contours seen in the Raman
spectra of the free PLA and its composites (Fig. 2 supp). New broad contours, not seen in the
spectra of PLA, appeared at about 1850, 1600 and 750 cm-1 that could be proposed as the
evidence for the hydrogen bond interaction between cellulose polymers and PLA matrix.
Raman intensity
PLA+M50
PLA+wt
PLA
3500
3000
2500
2000
1500
1000
500
-1
Wavenumber / cm
Fig. 2 supp. Raman spectra of composites PLA+wt, PLA+M50. Sheets of pure PLA were taken
as a reference. The measurements were conducted as described in the Materials and
Methods section.
The same analysis was conducted for the IR and Raman spectra of the PCL, PCL+wt and
PCL+M50 samples. The analysis of reflectance (Fig. 3 supp) IR spectra allows one to conclude
that the PCL blend differs from PLA in its influence on the reinforced cellulose admixture.
2
1190
'
PCL
Dielectric function
1047
Absorption coefficient
1725
''
PCL
PCL+wt
PCL+wt
'
PCL+M50
'
''
''
PCL+M50
2000
1800
1600
1400
1200
Wavenumber / cm
1000
-1
800
600
2000
1500
1000
Wavenumber / cm
Fig. 3 supp. Absorption coefficients and dielectric functions derived from the reflectance
FTIR spectra of PCL, PCL+wt, PCL+M50.
For the absorption coefficient the intensity ratios of bands at 1725 ((C=O) vibrations) and
1190 cm-1 ((C-O-C) vibrations of the –C(=O)-O-CH2- system) for PCL, PCL+wt and PCL+M50
samples are 1.00, 2.08 and 1.55, respectively. The respective intensity ratio of bands at 1725
and 1047 cm-1 ((C-O-C) vibrations of the –C(=O)-O-CH2- system) are 1.00, 2.33 and 1.60,
respectively. Comparing the intensity of the bands at 1725 cm -1 for these samples we obtain
the ratio 1 : 1.36 : 1.33, i.e. the intensity of the band corresponding to the (C=O) vibration
increases for the composites in relation to the pure PCL. The result might suggest disruption
of intramolecular hydrogen bonds in PCL matrix upon addition of cellulose polymers.
3
500
-1
Raman intensity
PCL+M50
PCL+wt
PCL
3500
3000
2500
2000
1500
1000
500
-1
Wavenumber / cm
Fig. 4 supp. Raman spectra of composites PCL+wt, PCL+M50. Sheets of pure PCL were taken
as a reference. The measurements were conducted as described in the Materials and
Methods section.
On the other hand the Raman spectra (Fig. 4 supp) of the free PCL and its composite are
quite similar to those obtained for PLA and its composite suggesting hydrogen bond
interaction between cellulose polymers and PCL matrix. This is however not confirmed by
detailed analysis of absorption spectra recorded for PCL and its composites. Since there was
no shift in bands wavenumber and their intensity in absorption spectra the lack of strong
molecular interactions between the PCL and cellulose is concluded.
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