Role of cellulose nanocrystals in epoxy-based nanocomposites: mechanical properties, morphology and thermal behavior

This study evaluated the influence of cellulose nanocrystals (CNC) content on the properties of epoxy nanocomposites. The CNC were obtained from microcrystalline cellulose by acid hydrolysis. 4.0, 5.5 and 7.0% of untreated CNC were incorporated into epoxy resin. Sonication was used to disperse the CNC in the resin. The thermal stability, the glass transition temperature and the degree of conversion were reduced as observed by Thermogravimetry and Differential Scanning Calorimetry, respectively. The tensile and bending modulus showed no significant improvement and the impact resistance showed a slight reduction due to the non-uniform dispersion of the CNCs, as observed by Transmission Electron Microscopy. Analysis of Scanning Electron Microscopy showed a change of the fracture mechanism of the epoxy resin: the CNCs increased the elastic modulus by reinforcement, but accelerated the fracture by acting as defects. The Halpin-Tsai model was applied to predict the elastic modulus of the epoxy/CNC system.

Keywords:
cellulose nanocrystals; nanocomposites; epoxy resin

Authorship

Nayra Reis do Nascimento

Laboratório de Blendas e Compósitos Poliméricos, Departamento de Engenharia de Materiais e Bioprocessos, Universidade Estadual de Campinas - UNICAMP, 13083-852, Campinas, SP, BrasilUniversidade Estadual de CampinasBrasilCampinas, SP, BrasilLaboratório de Blendas e Compósitos Poliméricos, Departamento de Engenharia de Materiais e Bioprocessos, Universidade Estadual de Campinas - UNICAMP, 13083-852, Campinas, SP, Brasil

http://orcid.org/0000-0001-5829-5524

Ivanei Ferreira Pinheiro

http://orcid.org/0000-0003-3445-2745

Guilherme Fioravanti Alves

http://orcid.org/0000-0003-2301-9209

Lucia Helena Innocentini Mei

http://orcid.org/0000-0002-6487-3500

José Costa de Macedo Neto^**morales@unicamp.br; jmacedo@uea.edu.br

Laboratório de Materiais e Processamento, Departamento de Engenharia de Materiais, Universidade do Estado do Amazonas - UEA, 69050-020 Manaus, AM, BrasilUniversidade do Estado do AmazonasBrasilManaus, AM, BrasilLaboratório de Materiais e Processamento, Departamento de Engenharia de Materiais, Universidade do Estado do Amazonas - UEA, 69050-020 Manaus, AM, Brasil

http://orcid.org/0000-0003-1155-0027

Ana Rita Morales ^**morales@unicamp.br; jmacedo@uea.edu.br

http://orcid.org/0000-0002-8765-559X

*morales@unicamp.br; jmacedo@uea.edu.br

SCIMAGO INSTITUTIONS RANKINGS

Figures | Tables | Formulas

Figures (11)
Tables (4)
Formulas (4)

^* * CNC volumetric concentration (%). V CNC (%)	Tg (°C)	$Δ H_{R}$ (mJ/mg)	X (%)
0	67	123	97
4	67	182	96
5.5	63	249	95
7	63	243	95

VCNC (%)****	T_{moisture loss} (°C)	Moisture loss (%)	T_onset* (%)	T_5%** (°C)	T_max*** (°C)
0	58-150	1.9	356	338	390
4	62-205	2.2	354	336	397
5.5	44-126	2.1	344	312	382
7	65-200	2.0	353	319	387

V CNC (%)^* * CNC volumetric concentration (%).	E_T (GPa)	𝛔_T (MPa)	Ԑ_T (%)	E_F (GPa)	𝛔F (MPa)	Ԑ_F (%)	IS (J/m)
0	1.70 ± 0.13	96 ± 23	2.7 ± 0.9	1.60 ± 0.15	73.2 ± 1.8	3.2 ± 0.8	4.8 ± 0.3
4	1.77 ± 0.11	62 ± 12	2.0 ± 0.1	2.30 ± 0.01	61.6 ± 3.1	3.5 ± 0.1	3.9 ± 0.1
5.5	1.94 ± 0.14	57 ± 12	1.5 ± 0.6	1.90 ± 0.17	50.6 ± 10.8	3.1 ± 0.8	3.7 ± 0.6
7	2.15 ± 0.35	51 ± 15	1.3 ± 0.6	2.10 ± 0.13	67.6 ± 8.5	3.3 ± 0.2	4.3 ± 0.3

Vf (4% CNCs)	Vf (5.5% CNCs)		Vf (7% CNCs)
Ec (GPa)
1.77	1.94		2.14
Ec/Em (ξ = 5)
1.11	1.16		1.20
Ec/Em (ξ = 10)
1.07	1.10		1.14
Experimental
1.03	1.13		1.25
E_CNC (GPa)		Em (GPa)
50^[⁵⁵55 Lahiji, R. R., Xu, X., Reifenberger, R., Raman, A., Rudie, A., & Moon, R. J. (2010). Atomic force microscopy characterization of cellulose nanocrystals. Langmuir, 26(6), 4480-4488. http://dx.doi.org/10.1021/la903111j. PMid:20055370. http://dx.doi.org/10.1021/la903111j... ^]		1.70