Understanding the water uptake in F-161 glass-epoxy composites using the techniques of luminescence spectroscopy and FT-NIR

Sales, Rita; Thim, Gilmar; Brunelli, Deborah

doi:10.1590/0104-1428.05516

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Original Article • Polímeros 27 (02) • Apr-Jun 2017 • https://doi.org/10.1590/0104-1428.05516 copy

Understanding the water uptake in F-161 glass-epoxy composites using the techniques of luminescence spectroscopy and FT-NIR

Authorship SCIMAGO INSTITUTIONS RANKINGS

Abstract

This paper investigates the application of the luminescence spectroscopy technique in steady–state to study the moisture influence in glass fiber/epoxy prepreg and their laminates. The studies were monitored by intrinsic luminescence comparing the results with gravimetric analysis and near infrared with Fourier transform. Samples are cured and submitted to humidity controlled at 60 and 80 °C until 90 days. It is verified that the decrease in the maximum emission of the samples is directly related to the material moisture content. However, for very short periods, there is an increase in the relative intensity and blue shift of the emission band for all samples treated at 60 °C, which is related to an increase of the rigidity of the polymeric matrix. The results in this paper have a great significance because it brings a wide discussion on the interaction of water in epoxy composites materials.

Keywords:
F-161 laminates; FT-NIR; luminescence spectroscopy; water uptake

Samples	λ_max (nm)		Water content (ΔM_rel %)	First moment of fluorescence (cm^-1)	Diffusion coefficient (cm²/min)
pre-84-60-t^a a t = exposure time;	452	488			1.22475x10^-7
		1	0.00	20969
		7	0.55	20926
	15^b b most intense band.		0.54	21556
	30		0.49	21240
		60	0.52	20927
		90	0.57	20975
pre-75-60-t		1	0.08	20775	2.01633x10^-8
	7^b b most intense band.		0.35	21469
	15		0.44	21413
	30		0.49	21383
		60	0.50	20811
		90	0.59	20757
pre-58-60-t		1	0.08	21100	2.0742x10^-8
	7^b b most intense band.		0.18	21957
	15		0.24	21986
	30		0.27	21922
		60	0.38	21005
		90	0.39	21066
pre-84-80-t^a a t = exposure time;		1	0.56	20909	5.1126x10^-8
		7^b	0.28	20816
		15	0.28	21115
		30	0.03	21049
		60	0.40	21023
		90	0.51	21043
		1	0.14	20957	1.61816x10^-9
pre-75-80-t		7	0.22	20900
		15^b	0.24	20946
		30	0.31	21020
		60	0.43	21003
		90	0.65	20913
		1	0.12	21203	1.8963x10^-8
pre-58-80-t		7	0.07	21134
		15	0	21081
		30^b	0.28	21035
		60	0.07	21134
		90	0.26	21089

Samples	λ_max (nm)		Water content (ΔM_rel %)	First moment of fluorescence (cm^-1)	Diffusion coefficient (cm²/min)
lam-84-60-t^a a t = exposure time;	448	478			3.3803.10^-5
	1		0.044	21483
	7^b b most intense band.		0.098	21502
	15		0.087	21443
	30		0.131	21584
lam-75-60-t	1		0.040	21536	2.0220.10^-5
	7		0.234	21644
	15^b b most intense band.		0.192	21582
	30		0.282	21510
lam-58-60-t	1^b b most intense band.		0.000	21486	4.2864.10^-5
	7		0.120	21510
	15		0.135	21566
	30		0.184	21584
lam-84-80-t^a a t = exposure time;	1		0.091	21562	4.9537.10^-7
	7		0.241	21563
	15^b b most intense band.		0.255	21452
	30		0.628	21520
lam-75-80-t	1		0.091	21599	1.2333.10^-5
	7		0.422	21540
	15		0.390	21498
	30^b b most intense band.		0.417	21506
lam-58-80-t	1		0.098	21486	5.8829.10^-6
	7^b b most intense band.		0.325	21510
	15		0.361	21566
	30		0.416	21584

Wavenumber (cm^-1)	Band assignments
6071	First overtone of terminal (methylene)-CH fundamental stretching vibration (epoxy ring).
5961	Overtone of the CH axial deformation of the phenyl group.
5886	First overtones of the fundamental –CH₂ and –CH stretching vibration.
5661	-OH combination band.
5247	-CH, -CH₂ combination band.
4672	Combination band of the aromatic conjugated C=C stretching (=1625 cm^-1) with the aromatic –CH fundamental stretching (=3050 cm^-1).
4625	Combination band of the aromatic conjugated C=C stretching (=1625 cm^-1) with the aromatic –CH fundamental stretching (=3050 cm^-1).
4524	Conjugated epoxy CH₂ deformation band (=1460 cm^-1) with the aromatic –CH fundamental stretch (=3050 cm^-1), -NH₂ absorption band.
4480	-CH, -CH₂ combination band.
4362	-CH₂ combination band.
4216	-CH, -CH₂ combination band.
4155	Aromatic –CH combination band.
4058	Aromatic combination band.

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[1] * rita.sales@fatec.sp.gov.br