Facile exfoliation of rectorite nanoplatelets in soy protein matrix and reinforced bionanocomposites thereof

Abstract

ABSTRACT:The rectorite (REC), a form of layered silicate, was facilely intercalated and even exfoliated in soy protein isolate (SPI) matrix. Furthermore, the reinforced biodegradable nanocomposite sheets were produced, in which the exfoliated REC lamellae plays a key role. After solution-mixing, XRD patterns showed that the REC lamellae were intercalated and even completely exfoliated for 4 wt % REC added, but the expanded gallery gradually became narrower with increasing REC content. FT-IR also verified the molecular-level associations between SPI molecules and REC lamellae by vibration variances of hydrogen bonding. The compression-molding further promoted intercalation and exfoliation, namely the 8 wt % REC can also be almost dispersed as exfoliated lamellae, while the interlayer of RECs also further separated for nanocomposites with higher REC content. TEM images visualized the transfer from exfoliation to intercalation and the decrease of interlayer distance with increasing REC content. The thicker and longer exfoliated REC lamellae resulted in high load and easy-to-yield of material. The maximum strength of nanocomposite sheets occurred at the addition of 12 wt % REC. Thereafter, the SPI chain can move more easily because of weak interaction between free negative-charge rich domain of SPI and REC surface in gallery, which did not favor enhancing mechanical performance.

Effects of layered silicate structure on the mechanical properties and structures of protein‐based bionanocomposites

“…The resultant viscous solution (dark-gray for the REC/PPI blends and light-yellow for the MMT/PPI blends) was freeze-dried for 48 h to obtain the nanocomposites (gray REC/PPI powder or yellow MMT/PPI powder), which preserved the original complex state in solution. According to the REC content in solid powders of 2,4,8,12,16,20, and 24 wt %, the gray nanocomposite powders were coded as RP-2-P, RP-4-P, RP-8-P, RP-12-P, RP-16-P, RP-20-P, and RP-24-P, respectively. Meanwhile, the yellow nanocomposite powders containing 2,4,8,12,16,20, and 24 wt % MMT were coded as MP-2-P, MP-4-P, MP-8-P, MP-12-P, MP-16-P, MP-20-P, and MP-24-P, respectively.…”

“…In addition, the hydroxylpropyl lignin can spontaneously assemble as oblate supramolecular nanoaggregates in soy protein matrix to enhance the strength of materials. 13,14 A considerable attention has been concentrated on exploring the mechanisms of intercalation and exfoliation in academic opinions and developing highperformance and low-cost materials for meeting practical applications, owing to the great improvement of performances over pristine polymer, 15 such as reinforcing function, 16 reducing gas permeability, 17 enhancing thermal stability 18 and self-extinguishing fire-retardance, 19 and other interesting properties. Montmorillonite (MMT) is currently the most popular in the family of layered silicates, 20 and its nylon-based nanocomposite was taken as a representative example for the reinforcing effect.…”

“…In view of the success of reinforcing soy protein plastics by incorporating layered silicates mentioned above, 6,16 another protein source of pea protein isolate (PPI) was filled with MMT and REC by solution intercalation respectively, and then the reinforced PPI-based nanocomposites were produced by hot press. In this case, the facile exfoliation of MMT and REC as well as the resultant high mechanical performances was expected.…”

Barrier properties of corn zein nanocomposite coated polypropylene films for food packaging applications

“…As OMMT dispersion increases, more bonding sites on OMMT gallery will be able to form new hydrogen bonds. C@O containing molecules of protein based biopolymers are able to form hydrogen bonding with the Si-O-Si and -OH containing galleries of OMMT particles resulting in shifting of Amide bands (Chen and Zhang, 2006;Yu et al, 2007). Considering the more explicit XRD diffraction data of CLO10A-7.5% sample together with FTIR data; shift from 1645.57 to 1643.05 cm À1 with increasing OMMT content can be attributed to poorer dispersion of nanoclay platelets within the zein matrix in the sample.…”

“…, that is generally assigned to in-plane Si-O bands (oriented parallel to clay layer) (Chen et al, 2001;Ijdo et al, 2006;Yu et al, 2007). Layered silicates, in their clay agglomerate form, gives a large band in the region 750-1350 cm À1 consisting of several Si-O-Si bands overlapping each other depending on the clay type (montmorillonite, kaolinite etc.)…”