Abstract
Introducing bio-oil into phenolic foam (PF) can effectively improve the toughness of PF, but its flame retardant performance will be adversely affected and show a decrease. To offset the decrease in flame retardant performance, montmorillonite (MMT) can be added as a promising alternative to enhance the flame resistance of foams. The present work reported the effects of MMT on the chemical structure, morphological property, mechanical performance, flame resistance, and thermal stability of bio-oil phenolic foam (BPF). The Fourier transform infrared spectroscopy (FT-IR) result showed that the –OH group peaks shifted to a lower frequency after adding MMT, indicating strong hydrogen bonding between MMT and bio-oil phenolic resin (BPR) molecular chains. Additionally, when a small content of MMT (2–4 wt %) was added in the foamed composites, the microcellular structures of bio-oil phenolic foam modified by MMT (MBPFs) were more uniform and compact than that of BPF. As a result, the best performance of MBPF was obtained with the addition of 4 wt % MMT, where compressive strength and limited oxygen index (LOI) increased by 31.0% and 33.2%, respectively, and the pulverization ratio decreased by 40.6% in comparison to BPF. These tests proved that MMT can blend well with bio-oil to effectively improve the flame resistance of PF while enhancing toughness.
Highlights
Polymeric foams, such as polyurethane (PUR), polyisocyanurate (PIR), polyvinyl chloride (PVC), and phenolic foams (PFs), have been widely researched and applied in a variety of emerging sectors [1,2,3,4,5].recent development of reinforced polymeric foams, has gained increasing interest driven by increasingly stringent requirements of high-performance foams in current markets
The Fourier transform infrared spectroscopy (FT-IR) spectra of MMT, the bio-oil phenolic foam (BPF) and MBPFs are illustrated in Figure 1, and the functional groups corresponding to the major peaks are identified and listed in Table 2 [21,23,39,40,41]
MBPFs showed remarkably enhanced toughness as well as good flame resistance compared to BPF
Summary
Recent development of reinforced polymeric foams, has gained increasing interest driven by increasingly stringent requirements of high-performance foams in current markets. Research on reinforced foams has focused on improving thermal and mechanical properties, alongside other properties [3,4,5]. PFs, known as the “king of insulation materials”, have received considerable attention, in this regard of reinforced foams, thanks to their low thermal conductivity, good thermal insulation, excellent flame resistance, low smoke density and nontoxicity, and no dripping in combustion [7]. The application of traditional PFs are severely restricted by their high brittleness and pulverization, many efforts have been made to strengthen them through the incorporation of reinforcements [8,9,10,11,12]
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