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. 2016 Jul 29;9(8):640.
doi: 10.3390/ma9080640.

Mechanical Properties and Morphologies of Carboxyl-Terminated Butadiene Acrylonitrile Liquid Rubber/Epoxy Blends Compatibilized by Pre-Crosslinking

Shiai Xu  1   2 , Xiaoxue Song  3 , Yangben Cai  4
Affiliations

Mechanical Properties and Morphologies of Carboxyl-Terminated Butadiene Acrylonitrile Liquid Rubber/Epoxy Blends Compatibilized by Pre-Crosslinking

Shiai Xu et al. Materials (Basel). .

Abstract

In order to enhance the compatibilization and interfacial adhesion between epoxy and liquid carboxyl-terminated butadiene acrylonitrile (CTBN) rubber, an initiator was introduced into the mixture and heated to initiate the cross-linking reaction of CTBN. After the addition of curing agents, the CTBN/epoxy blends with a localized interpenetrating network structure were prepared. The mechanical properties and morphologies of pre-crosslinked and non-crosslinked CTBN/epoxy blends were investigated. The results show that the tensile strength, elongation at break and impact strength of pre-crosslinked CTBN/epoxy blends are significantly higher than those of non-crosslinked CTBN/epoxy blends, which is primarily due to the enhanced interfacial strength caused by the chemical bond between the two phases and the localized interpenetrating network structure. Both pre-crosslinked and non-crosslinked CTBN/epoxy blends show a bimodal distribution of micron- and nano-sized rubber particles. However, pre-crosslinked CTBN/epoxy blends have smaller micron-sized rubber particles and larger nano-sized rubber particles than non-crosslinked CTBN/epoxy blends. The dynamic mechanical analysis shows that the storage modulus of pre-crosslinked CTBN/epoxy blends is higher than that of non-crosslinked CTBN/epoxy blends. The glass transition temperature of the CTBN phase in pre-crosslinked CTBN/epoxy blends increases slightly compared with the CTBN/epoxy system. The pre-crosslinking of rubber is a promising method for compatibilization and controlling the morphology of rubber-modified epoxy materials.

Keywords: compatibilization; epoxy; liquid rubber; mechanical properties; rubber-toughened epoxy.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
FTIR spectra of pre-crosslinked and non-crosslinked CTBN/epoxy blends: (a) full-scale spectra; (b) amplified spectra of nitrile groups; and (c) amplified spectra of double carbon bonds.
Figure 2
Figure 2
SEM micrograph of the tensile fractured surfaces of neat epoxy.
Figure 3
Figure 3
SEM micrographs of the tensile fractured surfaces: (A1) 5 phr CTBN/epoxy blends; (A2) 5 phr pre-crosslinked CTBN/epoxy blends; (B1) 10 phr CTBN/epoxy blends; (B2) 10 phr pre-crosslinked CTBN/epoxy blends; (C1) 15 phr CTBN/epoxy blends; and (C2) 15 phr pre-crosslinked CTBN/epoxy blends at a low magnification.
Figure 4
Figure 4
SEM micrographs of cryofractured surfaces etched by toluene: (a1) 5 phr CTBN/epoxy blends; (a2) 5 phr pre-crosslinked CTBN/epoxy blends; (b1) 10 phr CTBN/epoxy blends; (b2) 10 phr pre-crosslinked CTBN/epoxy blends; (c1) 15 phr CTBN/epoxy blends; and (c2) 15 phr pre-crosslinked CTBN/epoxy blends at a high magnification.
Figure 5
Figure 5
Variations of (a) storage modulus and (b) tan δ with temperature for different CTBN/epoxy blends.
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