SAMPE Journal - July/August 2019 - 28

FEATURE / HYBRID PHENOLIC RESINS
FIGURE 27. Schematic outlines for preparation of nanoporous carbonaceous materials.

PMMA are compatible before curing. Induced
phase separation occurs during curing process,
and nanostructure-scale phase separation structure exists in the cured products.
Figure 29 illustrates the micrographs of PMMA/
PF carbonized products. The amount of pores increased with the addition of the PMMA content. A
classical co-continuous structure was shown in the
PF1-PMMA-25%-700 [Figures 29(e) and 29(f )].
The relationship between the nano-porous
structure of carbon monoliths and compressive
strength was revealed (Figure 30). Co-continuous

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pores provided escape channels for those volatile
gases produced in the carbonization process to escape, reducing inner stress of the carbon materials.
During compressive loading, co-continuous pores
could also help to scatter and absorb the stress and
energy. Porous carbon monoliths with a compressive strength of 34 MPa were obtained, and the
compressive strength increased by 580% compared
with that of carbon monoliths obtained from pure
PF.
Nano-porous phenolic materials from phenolic
resin/solvent solution
Ethanol, isopropanol, acetone and other solvents
have good compatibility with phenolic resin.
During the curing process of phenolic resin, with
the increase of molecular weight of phenolic resin, phase separation also occurs. Further with the
curing reaction, the solvent evaporates and leaves,
forming a porous structure in phenolic resin. In
this process, it is very important to control the stability of the two-phase structure in the curing process of phenolic resin, so as to avoid the collapse
and shrinkage of the porous structure.
The addition of acid curing agent in phenolic
resin can greatly accelerate the gelation rate of phenolic resin, thereby affecting the phase separation
process of phenolic resin solution. Figure 31 shows
the microstructure of cured phenolic solution with
different curing agents (sulphuric acid) content. It
can be found that when the content of curing agent
is high, the curing induced phase separation occurs
rapidly, forming a micron-scale porous structure.
As the content of curing agent decreases, the size of
porous decreases gradually, forming a nano-scale
porous microstructure. However, when the content
of curing agent is too low, the skeleton structure
of phenolic resin gel is unstable, therefore, as the
solvent evaporates, the pore structure collapses to
form a dense solidified substance.
Further, we studied the microstructure of porous phenolic resin obtained from different solvent
contents. From Figure 32 we can see that different

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SAMPE Journal - July/August 2019

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