5
in a ratio of 5%:3%, the mechanical property of the foam is
satisfactorily enhanced, and the flame retardancy and ther-
mal stability reach the optimum values. In (Zhu &Wang,
2016),effects of nanometallic oxides on the mechanical
strengths and friability of the phenolic foams are investi-
gated. Results show that, PF foams with enhanced mechan-
ical strength and pulverization resistance were prepared
using nano-Al₂O₃ and nano-ZrO₂, while aiming to main-
tain excellent flame-retardant properties. The mechanical
test results showed that with 5 phr loading of nano-Al₂O₃,
the flexural, compressive, and impact strengths of the PF
foams increased by 33%, 46%, and 51%, respectively, while
the same properties increased by 31%, 30%, and 49% with
5 phr loading of nano-ZrO₂.
In (Wang et al., 2024), effect of boric acid and
organosiloxane additives on physical properties of phenolic
foams are investigated. Results indicate that, those materi-
als can improve the compressive strength are density of the
phenolic foams. In (N. Zhang et al., 2020), effect of whis-
ker silicon as an additive material is investigated and results
indicating that this material can also be used for increas-
ing the compressive strength of the phenolic foams. Results
indicate that increasing the amount of whisker silicon leads
to a significant increase in UCS, with a 47% increase at
0.2% and an impressive 81.10% increase at 0.6%. This
indicates that whisker silicon is an effective additive for
enhancing the mechanical strength of phenolic foams.
Synthesis and Characterization of Phenol-Urea-
Formaldehyde (PUF) Foaming Resin is investigated in (X.
Hu et al., 2014). The optimized reaction conditions for
the synthesis of PUF resin are as follows: phenol amount,
1 mol urea amount, 0.5 mol paraformaldehyde, 3 mol
catalyst amount, 0.05 mol reaction time, 3 h reaction
temperature, 75C. This study also compares the proper-
ties of polyurethane foam (PUF) and phenolic foam (PF),
highlighting differences in expansion ratio, compressive
strength, shrinkage, and oxygen index. The phenolic foam
exhibits a slightly higher compressive strength (0.12 MPa)
compared to polyurethane foam (0.10 MPa), while both
types of foam have similar oxygen indices (33% for PUF
and 32% for PF). This suggests that phenolic foams may
offer better mechanical performance while maintaining
comparable fire resistance properties, therefore, is very suit-
able for normal-temperature foaming in underground coal
mines.
The effects of curing agent on the mechanical and
thermal properties of phenolic foams are also investigated
in (Y. Zhang et al., 2015). The results indicate that differ-
ent curing agents significantly affect the tensile strength of
the composites, with the highest tensile strength recorded
for the sample cured with HMTA (109 ± 4 MPa). This
highlights the importance of selecting appropriate curing
agents to optimize the mechanical properties of phenolic
resin composites, which can be crucial for their applica-
tion in various industries. In (Y. Zhang et al., 2021), effect
of aluminum hydroxide, nitrile rubber, and propylene
oxide on the mechanical properties of phenolic foams are
investigated and results show that the optimized phenolic
resin-based composite material achieved an oxygen index
of 34.9%, a compressive strength of 47 kPa, and a foaming
and curing temperature of 91.7°C. The ideal formulation
was determined to be 8% aluminum hydroxide, 5% sili-
cone oil, and 3% methylene chloride.
Findings in Table 1. show that additive choice and for-
mulation adjustments substantially impact phenolic foam
performance. Bio-based fillers like lignin and tannin con-
tribute eco-friendly benefits but may reduce mechanical
strength unless modified forms, such as lignin nanoparti-
cles, are used. Nano-additives, including nano-Al₂O₃ and
nano-ZrO₂, demonstrate strong effectiveness, improving
both compressive strength and thermal stability, with nano-
Al₂O₃ increasing flexural and impact strengths by up to
51%. Short fiber reinforcement, especially with aramid and
glass fibers, effectively enhances toughness and dimensional
stability, with aramid fibers excelling in peel strength and
abrasion resistance. Increasing density also proved effective
in boosting compressive strength, though it raises thermal
conductivity, affecting insulation. Overall, targeted addi-
tives and optimized formulations enhance phenolic foam
durability, thermal performance, and safety, making them
highly effective for applications like fire prevention in min-
ing environments.
TEST STANDARDS USED TO DESIGNATE
MECHANICAL AND PHYSICAL
PROPERTIES OF PHENOLIC FOAMS
The effects of additive materials on the produced foams
must be designated and in order to produce a comparable
database, same standards must be used on the testing pro-
cedure. In this chapter different test used for designating
properties of phenolic foams and standards applied while
conducting these tests are given.
Physical Properties
Density Measurement
Purpose: Evaluating the homogeneity and quality of foam.
The applied standards while measuring the density of pro-
duced foams are BS EN 131662010, GB/T 6343–2009,
ISO 845, ASTM D1622, ASTM D792 (Table 1).
in a ratio of 5%:3%, the mechanical property of the foam is
satisfactorily enhanced, and the flame retardancy and ther-
mal stability reach the optimum values. In (Zhu &Wang,
2016),effects of nanometallic oxides on the mechanical
strengths and friability of the phenolic foams are investi-
gated. Results show that, PF foams with enhanced mechan-
ical strength and pulverization resistance were prepared
using nano-Al₂O₃ and nano-ZrO₂, while aiming to main-
tain excellent flame-retardant properties. The mechanical
test results showed that with 5 phr loading of nano-Al₂O₃,
the flexural, compressive, and impact strengths of the PF
foams increased by 33%, 46%, and 51%, respectively, while
the same properties increased by 31%, 30%, and 49% with
5 phr loading of nano-ZrO₂.
In (Wang et al., 2024), effect of boric acid and
organosiloxane additives on physical properties of phenolic
foams are investigated. Results indicate that, those materi-
als can improve the compressive strength are density of the
phenolic foams. In (N. Zhang et al., 2020), effect of whis-
ker silicon as an additive material is investigated and results
indicating that this material can also be used for increas-
ing the compressive strength of the phenolic foams. Results
indicate that increasing the amount of whisker silicon leads
to a significant increase in UCS, with a 47% increase at
0.2% and an impressive 81.10% increase at 0.6%. This
indicates that whisker silicon is an effective additive for
enhancing the mechanical strength of phenolic foams.
Synthesis and Characterization of Phenol-Urea-
Formaldehyde (PUF) Foaming Resin is investigated in (X.
Hu et al., 2014). The optimized reaction conditions for
the synthesis of PUF resin are as follows: phenol amount,
1 mol urea amount, 0.5 mol paraformaldehyde, 3 mol
catalyst amount, 0.05 mol reaction time, 3 h reaction
temperature, 75C. This study also compares the proper-
ties of polyurethane foam (PUF) and phenolic foam (PF),
highlighting differences in expansion ratio, compressive
strength, shrinkage, and oxygen index. The phenolic foam
exhibits a slightly higher compressive strength (0.12 MPa)
compared to polyurethane foam (0.10 MPa), while both
types of foam have similar oxygen indices (33% for PUF
and 32% for PF). This suggests that phenolic foams may
offer better mechanical performance while maintaining
comparable fire resistance properties, therefore, is very suit-
able for normal-temperature foaming in underground coal
mines.
The effects of curing agent on the mechanical and
thermal properties of phenolic foams are also investigated
in (Y. Zhang et al., 2015). The results indicate that differ-
ent curing agents significantly affect the tensile strength of
the composites, with the highest tensile strength recorded
for the sample cured with HMTA (109 ± 4 MPa). This
highlights the importance of selecting appropriate curing
agents to optimize the mechanical properties of phenolic
resin composites, which can be crucial for their applica-
tion in various industries. In (Y. Zhang et al., 2021), effect
of aluminum hydroxide, nitrile rubber, and propylene
oxide on the mechanical properties of phenolic foams are
investigated and results show that the optimized phenolic
resin-based composite material achieved an oxygen index
of 34.9%, a compressive strength of 47 kPa, and a foaming
and curing temperature of 91.7°C. The ideal formulation
was determined to be 8% aluminum hydroxide, 5% sili-
cone oil, and 3% methylene chloride.
Findings in Table 1. show that additive choice and for-
mulation adjustments substantially impact phenolic foam
performance. Bio-based fillers like lignin and tannin con-
tribute eco-friendly benefits but may reduce mechanical
strength unless modified forms, such as lignin nanoparti-
cles, are used. Nano-additives, including nano-Al₂O₃ and
nano-ZrO₂, demonstrate strong effectiveness, improving
both compressive strength and thermal stability, with nano-
Al₂O₃ increasing flexural and impact strengths by up to
51%. Short fiber reinforcement, especially with aramid and
glass fibers, effectively enhances toughness and dimensional
stability, with aramid fibers excelling in peel strength and
abrasion resistance. Increasing density also proved effective
in boosting compressive strength, though it raises thermal
conductivity, affecting insulation. Overall, targeted addi-
tives and optimized formulations enhance phenolic foam
durability, thermal performance, and safety, making them
highly effective for applications like fire prevention in min-
ing environments.
TEST STANDARDS USED TO DESIGNATE
MECHANICAL AND PHYSICAL
PROPERTIES OF PHENOLIC FOAMS
The effects of additive materials on the produced foams
must be designated and in order to produce a comparable
database, same standards must be used on the testing pro-
cedure. In this chapter different test used for designating
properties of phenolic foams and standards applied while
conducting these tests are given.
Physical Properties
Density Measurement
Purpose: Evaluating the homogeneity and quality of foam.
The applied standards while measuring the density of pro-
duced foams are BS EN 131662010, GB/T 6343–2009,
ISO 845, ASTM D1622, ASTM D792 (Table 1).