142
and crosslinking agents, catalysts and surfactants, can be added in the formulation
in order to produce cellular network in the foam structure.
Polyols are polymers that contain two or more hydroxyl groups (-OH). Polyols
are one of the main raw materials (isocyanates and polyols) for the synthesis of PU
foam (Li et al. 2017a, b, c). The most commercially significant polyols are: (1)
polyether polyols obtained from the exothermic reaction of 1,2-butylene oxide,
1,2-propylene oxide or ethylene oxide, etc. (Bailosky et al. 2013) and (2) polyester
polyols synthesized by polymerization of diacids (adipic acid, phthalic anhydride,
succinic acid, etc.) and diols (1,4-butane diol, 1,4-cyclohexane dimethanol, ethylene glycol, etc.) (Sonnenschein 2014).
PU foams prepared with polyester polyols are commonly rigid with excellent
mechanical properties and grease resistance, but have little flexibility at low temperature (Septevani et al. 2015), while PU foams prepared using polyether polyols
Table 7.3 Organosolv fractionation processes of different raw materials by using acetic/formic
acid solvents
Raw material Fractionation process
Pulp yield
(crude cellulose,
% of dry biomass)
References
Miscanthus
Acetic acid:water (93:7, v/v),
cooked to boiling point for 147 min
52.6
Ligero et al.
(2005)
Wheat straw
Acetic acid:formic acid:water
(11:6:3, v/v/v), for 180 min. at
105 °C
48
Snelders et al.
(2014)
Acetic acid/water (9:1, v/v), for
180 min. at 105 °C
50
Pan and Sano
(2005)
Acetic acid:formic acid:water
(6:3:1, v/v/v), for 240 min. at 85 °C
47.2
Xu et al.
(2006)
Bamboo
Acetic acid:water (9:1, v/v), for
120 min. at 140 °C
47
Li et al. (2012)
Formic acid/acetic acid/water
(3:5:2, v/v/v), 107 °C, 180 min
39.5
Wen et al.
(2013)
Sugarcane
bagasse
Formic acid:water (39:11, v/v), for
90 min. at 107 °C
48.2
Zhao and Liu
(2012)
Eucalyptus
globulus
Acetic acid/water (9:1, v/v), 180 °C,
60 min
94 (cellulose recovery) Vila et al.
(2014)
Cornstalk
Acetic acid:formic acid:water
(6:3:1, v/v/v), for 180 min. at 90 °C
57
Shui et al.
(2016)
n
n
O
O
O
+ nH
O H
*
HNC
R 1 NH
R 2 O
*
C O
O
O
R 2
–
N
R 1
N
C
C
Fig. 7.1 Synthesis of PU by polyaddition reactions between isocyanates and polyols
H. Li et al.
and crosslinking agents, catalysts and surfactants, can be added in the formulation
in order to produce cellular network in the foam structure.
Polyols are polymers that contain two or more hydroxyl groups (-OH). Polyols
are one of the main raw materials (isocyanates and polyols) for the synthesis of PU
foam (Li et al. 2017a, b, c). The most commercially significant polyols are: (1)
polyether polyols obtained from the exothermic reaction of 1,2-butylene oxide,
1,2-propylene oxide or ethylene oxide, etc. (Bailosky et al. 2013) and (2) polyester
polyols synthesized by polymerization of diacids (adipic acid, phthalic anhydride,
succinic acid, etc.) and diols (1,4-butane diol, 1,4-cyclohexane dimethanol, ethylene glycol, etc.) (Sonnenschein 2014).
PU foams prepared with polyester polyols are commonly rigid with excellent
mechanical properties and grease resistance, but have little flexibility at low temperature (Septevani et al. 2015), while PU foams prepared using polyether polyols
Table 7.3 Organosolv fractionation processes of different raw materials by using acetic/formic
acid solvents
Raw material Fractionation process
Pulp yield
(crude cellulose,
% of dry biomass)
References
Miscanthus
Acetic acid:water (93:7, v/v),
cooked to boiling point for 147 min
52.6
Ligero et al.
(2005)
Wheat straw
Acetic acid:formic acid:water
(11:6:3, v/v/v), for 180 min. at
105 °C
48
Snelders et al.
(2014)
Acetic acid/water (9:1, v/v), for
180 min. at 105 °C
50
Pan and Sano
(2005)
Acetic acid:formic acid:water
(6:3:1, v/v/v), for 240 min. at 85 °C
47.2
Xu et al.
(2006)
Bamboo
Acetic acid:water (9:1, v/v), for
120 min. at 140 °C
47
Li et al. (2012)
Formic acid/acetic acid/water
(3:5:2, v/v/v), 107 °C, 180 min
39.5
Wen et al.
(2013)
Sugarcane
bagasse
Formic acid:water (39:11, v/v), for
90 min. at 107 °C
48.2
Zhao and Liu
(2012)
Eucalyptus
globulus
Acetic acid/water (9:1, v/v), 180 °C,
60 min
94 (cellulose recovery) Vila et al.
(2014)
Cornstalk
Acetic acid:formic acid:water
(6:3:1, v/v/v), for 180 min. at 90 °C
57
Shui et al.
(2016)
n
n
O
O
O
+ nH
O H
*
HNC
R 1 NH
R 2 O
*
C O
O
O
R 2
–
N
R 1
N
C
C
Fig. 7.1 Synthesis of PU by polyaddition reactions between isocyanates and polyols
H. Li et al.