Nitrogen Dioxide Catalyzed Aerobic Oxidative Cleavage of C(OH)–C Bonds of Secondary Alcohols to Produce Acids

Article abstract of DOI:10.1002/anie.201908788

Stable organic nitroxyl radicals are an important class of catalysts for oxidation reactions, but their wide applications are hindered by their steric hinderance, high cost, complex operation, and separation procedures. Herein, NO₂ in DMSO is shown to effectively catalyze the aerobic oxidative cleavage of C(OH)?C bonds to form a carboxylic group, and NO₂ was generated in situ by decomposition of nitrates. A diverse range of secondary alcohols were selectively converted into acids in excellent yields in this transition-metal-free system without any additives. Preliminary results also indicate its applicability to depolymerize recalcitrant macromolecular lignin. Detail studies revealed that NO₂ from nitrates promoted the reaction, and NO₂ served as hydrogen acceptor and radical initiator for the tandem oxidative reaction.

Full text of DOI:10.1002/anie.201908788

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Interface Bonding Properties and Mechanism of Poplar Board-
Veneered Wood Fiber/Polypropylene Composites with Chlorinated
Polypropylene Films as an Intermediate Layer
Yinan Liu,†,‡ Yanan Sun,† Jianxiu Hao,† Weihong Wang,*,† Yongming Song,† and Zhifang Zhou‡
†Key Laboratory of Bio-Based Material Science and Technology (Chinese Ministry of Education), Northeast Forestry University,
Harbin 150040, China
‡Heilongjiang Institute of Wood Science, Harbin 150040, China
ABSTRACT: It is difficult to decorate wood plastic
composites with wood veneer because their surface energy is
low and there are no pores on the surface. In the present
study, we developed an environmentally friendly and
convenient method to decorate the wood fiber/polypropylene
(WF/PP) composite board. We used chlorinated polypropy-
lene (CPP) as an intermediate film to laminate wood veneer
to WF/PP composite boards by hot-pressing at 110 °C and
then cooling down. The interface bonding mechanism
between the wood veneer, CPP layer, and WF/PP composite
was analyzed using scanning electron microscopy (SEM),
energy dispersive X-ray analysis (EDS), surface roughness test,
and attenuated total reflection−Fourier transform infrared
spectroscopy (ATR−FTIR). The results indicated that CPP
penetrated the wood pores and formed a firm anchor structure. SEM images showed small cracks at the interface between CPP
and PP when WF/PP contained less WF. The results of SEM−EDS and ATR−FTIR showed that WF/PP composites with a
higher WF content would have more fibers exposed at the surface, thus making the surface rough and providing more specific
surface area. The veneered WF/PP composite with 80% WF content had the highest surface bond strength and water resistance.
the enhancement effect of materials.9 On the basis of alkali
1. INTRODUCTION
treatment, Ma (2017) treated hemp with 3-aminopropyltrie-
The connection between the dwelling environment and human
thoxysilane and achieved an even better result.10 As well as
health has been a focus of governments worldwide in recent
chemical treatment, the addition of compatibilizers is also an
years.1−3 Commonly used materials for indoor decoration
effective method. Karmarkar (2007) grafted m-isopropenyl-α,
(e.g., shaving board, fiberboard, and aldehyde adhesive)
α-dimethylbenzyl-isocyanate onto PP to enhance the interface
contain volatile organic matter.4,5 Many research institutions
have attempted to find a substitute material for traditional
wood-based boards. The biofiber-reinforced polyolefin compo-
site is a suitable material that does not contain volatile matter.
The processing residue of wood products and nondegradable
high-density polyethylene polypropylene (PP) can be recycled
bond between the WF and PP matrix.11 Both the tensile
strength and flex properties of the resultant composite were
significantly improved. These treatments may be efficient in
modifying the surface of biofiber-reinforced PP composites,
but they require high temperatures or a cumbersome process
to react. As a physical method, plasma treatment of the surface
as a raw material. Biofiber-reinforced polyolefin composites
of polyolefin materials was investigated,12,13 which temporarily
have good mechanical properties6 and possess dimensional
increased the ion activity on the material surface. Gupta
stability and water resistance. Furthermore, the addition of
(2007) and Laborie (2007) used flame and plasma to treat the
biofiber could improve impact strength and elasticity.
surface of biofiber-reinforced PP by increasing oxygen-
However, the nonporosity and nonpolar surface characteristics
of polyolefin-based composites result in difficult coverage with
common adhesives compared to the traditional artificial wood
containing groups.14,15 However, these treatments have
limitations, including the effect not being maintained for a
long period of time. Chemical modification on the surface
boards. This limits the application of the polyolefin matrix
maybe a better way to enhance the adhesion properties,16,17
composite in the interior environment region.
but the high cost and pollution produced during treatment
PP is a commonly used matrix material for manufacturing
biofiber-reinforced polyolefin composites.7 Several studies have
investigated the enhancement and interfacial modification of
biofiber-reinforced PP composites over recent years.8,9 Beg
(2016) used NaOH to pretreat wood fiber (WF) and obtained
Received: July 19, 2019
Revised: September 22, 2019
Published: October 1, 2019
© XXXX American Chemical Society
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Nanjing, China) and cut into small granules with a pulverizer. These
particles were extruded into WF/PP composite boards (4 mm thick,
100 mm wide) through a single-screw extruder (SJ45, Nanjing Rubber
and Plastics Machinery Factory, China). Three ratios of WF to PP
were synthesized, as shown in Table 1.
2.3. Preparation of CPP Films. The CPP film preparation
process is shown in Figure 1. The CPP particles were evenly spread in
a square mold with an inside length of 160 mm and a thickness of 0.1
mm. The mold was hot-pressed at a temperature of 110 °C for 3 min,
under a pressure of 2 MPa. It was then cold-pressed at a temperature
of 20 °C for 5 min to shape the film.
2.4. Preparation of the Veneered WF/PP Composite Board.
The surface of the WF/PP composite board was covered with the
CPP film, onto which the poplar veneer was then placed, as shown in
Figure 1. The sandwich structure was pressed under a pressure of 5
MPa for 5 min at a temperature of 110 °C and then cold-pressed at a
temperature of 20 °C for 5 min.
As a control, the WF/PP composite board containing 60% WF was
covered with wood veneer by pressing at 180 °C without an
intermediate film or adhesive. PP accumulated on the surface of the
WF/PP composite acting as a “glue”.
impeded its application for industries. Guo et al. (2018) used
the MAPE and HDPE film as an intermediate layer,18 which
solved the problems of pollution and bonding strength, but the
high temperature required would melt the base biofiber-
reinforced board as well as degrade the surface decorating
materials.
In this study we explored a new technology for decorating
the WF/PP composite board by using an intermediate film as
an adhesive at a lower hot-pressing temperature. Chlorinated
polypropylene (CPP) was used to bond the wood veneer and
WF/PP composite base board. CPP is often used as a
modifying agent in coatings and adhesives. Hu et al. (2018)
synthesized a CPP emulsion by grafting methyl methacrylate,19
butyl acrylate, and acrylic acid onto it. The printability of the
PP film was improved after coating with the modified CPP
emulsion. Tomasetti et al. (2000) found that CPP solution
could diffuse into the PP/PE copolymer.20 On the other hand,
the grafting of chlorine (Cl) in the molecular chain increased
the polarity of CPP, thus improving its adhesion to the wooden
surface. CPP could, therefore, be used as an advanced
intermediate adhesive for the lamination of the PP board
with other materials.
The veneered WF/PP boards were then conditioned at a
temperature of 20 °C and 65% relative humidity for 1 week before
they were tested.
2.5. Preparation of CPP/PP Compound Films. In order to
detect the bonding mechanism between the CPP and PP accumulated
on the surface of the WF/PP composite, a CPP/PP compound film
was prepared. CPP and PP particles were hot-pressed into films at a
temperature of 110 and 180 °C, respectively, and then cold-pressed at
a temperature of 20 °C. The two films were then laminated together
at a temperature of 110 °C (same as the preparation of the veneered
WF/PP composite board, in Section 2.4). The CPP/PP compound
film had two surfaces, that is, one side was CPP and the other was PP.
The process for preparing and analyzing the CPP/PP compound film
is shown in Figure 2. The three surfaces of the compound film were
scanned with scanning electron microscopy (SEM) is shown in Figure
2.
2.6. Measuring the Penetration Depth of CPP and PP into
the Wood Veneer. To illustrate the bonding mechanism between
PP, CPP, and the wood veneer, we designed an experiment to
simulate the bonding between CPP, PP, and the wood board. The
CPP film was prepared and spread on the poplar wood veneer, then
pressed together at 110 °C and 2 MPa for 2 min. The board was
cooled to room temperature and cut into slices with a microtome.
The PP film-covered veneer was prepared in the same way but
pressed at a temperature of 180 °C. The cross-section of
microsections was scanned with scanning electron microscopy
(SEM).
2.7. Surface Bonding Strength Test. The surface bonding
strength between the veneer and WF/PP board was evaluated based
on the vertical drawing test as shown in Figure 3. The size of the
sample was 50 × 50 × 6 mm3, with a middle circle of 1000 mm2 area
curved on the surface. There were 12 specimens in each group. The
loading rate was 2 mm/s.
2.8. Water Resistance Test. The water resistance of the adhesive
layer and its interfaces between the wood veneer and WF/PP
composite board was evaluated. Samples (veneered WF/PP
composites, 75 × 75 × 6 mm3) were immersed in water at 63 °C
for 3 h and then dried in an oven at 63 °C for 3 h. The delaminated
length at four edges of the dried samples was measured. Six samples
were tested in each series.
The lamination process was conducted at a relatively low
temperature (90−110 °C), therefore avoiding the deformation
of the WF/PP base board (PP melting point was 168 °C in this
study) and degradation of the wood veneer surface. The
bonding strength and water resistance of the adhesive layer
were investigated. The bonding mechanism between the wood
veneer, CPP, and WF/PP was built based on analyzing the
penetration of CPP into wood conduits, surface roughness, and
chemical characteristics of the composite surface. A simulation
experiment of CPP and PP bonding was implemented to reveal
the real form of their interface. The proposed method is simple
and environmentally friendly.
2. EXPERIMENTAL SECTION
2.1. Materials. The rotary-cut Poplar wood (Populus tomentosa
̀
Carriere) veneers (thickness of 1.5 0.1 mm) were purchased from
Jinan Yuanfang Wood Trading Company. The moisture content of
these veneers was 28%. Some of the veneers were ground (40−80
mesh) to WFs for preparing the WF/PP composite. WFs and veneers
were dried at a temperature of 103 °C until the moisture content was
<3.0%. PP (T300, melting point 168 °C, density 0.91 g/cm3, melting
flow rate (MFR) = 2.5−3.5 g/10 min at 180 °C) was purchased from
Sinopec Daqing Petrochemical Company, Daqing, China. Maleic
anhydride grafted polypropylene (MAPP) (grafting percentage 1−
1.2%) was obtained from Shanghai Sunny New Technology
Development Co, Shanghai, China. CPP was supplied as pellets by
Shenzhen Jitian Chemical Products Limited Company, Shenzhen,
China, with a chlorination ratio of 32%, MFR = 16.6−20.1 g/10 min
at 110 °C, melting point 90 °C, and density 0.93 g/cm3.
2.2. Preparation of WF/PP Composites. PP, WF, and MAPP
were blended at different mass fraction ratios (Table 1) with a high-
speed mixer (SHR-10A, Zhangjiagang Tonghe Plastic Machinery Co,
Zhangjiagang, China). The mixtures were prilled using a corotating
twin-screw extruder (JSH30, Nanjing Rubber & Plastic Machinery,
2.9. Surface Roughness Test. The surface roughness of the WF/
PP base board was measured using a contact-type surface roughness
measuring instrument (SJ-210, Mitutoyo Japan Corporation,
Kawasaki, Japan). The maximum height of the profile (Rz), contour
arithmetic means deviation (Ra), surface profile height root mean
square (Rq), and the surface contour curve were measured and
calculated according to “ISO 4287:1997 geometrical product
specifications, surface texture: profile method, terms, definitions,
and surface texture parameters.” The testing length was 5 mm. The
Table 1. Component Mass Parts for Each WF/PP
Composite (Mass Part)
composite
WF
PP
MAPP
60 WF/40 PP
70 WF/30 PP
80 WF/20 PP
60
70
80
40
30
20
2
1.5
1
B
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Figure 1. Process for the preparation of a veneered WF/PP board with CPP intermediate films.
Figure 2. Process for lamination of CPP and PP and analysis of the bonding mechanism.
Figure 3. Schematic diagram showing the sample and apparatus used
to test the surface bonding strength.
probe was made of adamas, with a movement speed of 0.5 mm/s and
a pressure of 4 mN. A GAUSS filter was used and 8000 data points
were collected.
Figure 4. Surface bonding strength of wood veneered WF/PP
composites.
2.10. Scanning Electron Microscopy. The bonding interface
between the WF/PP composite board and the poplar veneer was first
observed under a scanning electron microscope (JSM7500F, JEOL
DATUM Shanghai Co., Ltd. Shanghai, China). The section slices
were prepared by microtomy (described above). The samples were
coated with gold and then examined with an accelerating voltage of 5
kV. Two sides and the cross-section of the CPP/PP compound film
were scanned by SEM and energy dispersive X-ray analysis (EDS) to
confirm the Cl distribution. WF/PP boards were scanned in the same
way to detect oxygen.
2.11. ATR−FTIR Spectroscopy. The chemical group on the
surface of the WF/PP composite was analyzed with attenuated total
reflection−Fourier transform infrared spectroscopy (ATR−FTIR)
spectroscopy (Nicolet 6700, Nicolet Company, Madison, Wisconsin,
USA). Scans were recorded from 4000 to 400 cm−1 at a resolution of
4 cm−1. Six spectra curves were recorded for each sample.
contact, on the one side, with the polar wood surface and the
surface of the WF/PP composite on the other side. These two
interfaces had very different combination modes and bonding
strengths, which determined the bonding strength between the
WF/PP base board and the wood veneer surface.
3.1. Bonding Strength of the Veneered WF/PP
Composite. As shown in Figure 4, the bonding strength
significantly increased with an increasing WF content of the
WF/PP composite. The control group showed the lowest
bonding strength and the layers separated between the wood
veneer and base board (Figure 5a). The WF content in the
WF/PP composite was the main factor influencing the bond
strength for the sample with the CPP film. The failure region
with fewer wood fragments stick on it (Figure 5b) for the base
board with 60 mass part WF content. than that samples with
higher WF content. With the increasing of the WF content in
the base board, the surface failure position moved further
inside the wood veneer (Figure 5c,d). No failure occurred on
3. RESULTS AND DISCUSSION
In this study, CPP was the key intermediate layer between the
wood veneer and WF/PP composite board. The layer was in
C
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Figure 5. Failure morphology of the adhesive layer in (a) control; (b) 60 WF/40 PP base board; (c) 70 WF/30 PP base board; and (d) 80 WF/20
PP base board.
Table 2. Length of Delamination between Veneer and WF/PP Composites after Water Soaking−Drying Treatment
WF/PP base board
control 60 WF/40 PP
48.7
60 WF/40 PP
5.5
70 WF/30 PP
0.4
80 WF/20 PP
0
delamination length (mm)
Figure 6. Cross-section of the interface between the wood veneer, CPP, and WF/PP for (a) 60 WF/40 PP; (b) 70 WF/30 PP; and (c) 80 WF/20
PP base board composites.
Figure 8. The molecular structures of PP (top) and CPP (bottom).
Figure 7. Penetration depth of CPP and PP into the poplar wood
veneer. (a) PP penetration depth; and (b) CPP penetration depth.
3.2. Water Resistance of the Glue Line. The
the bond line of the sample with 80 mass part WF content, that
is, all the failure occurred within the poplar wood veneer
(Figure 5d). These results indicated that CPP provided a
greater bonding strength to the veneered WF/PP composite
with a higher WF content.
delamination length of the four veneered WF/PP composites
is shown in Table 2. The control group presented with the
longest delamination. This was because hot water immersion
and drying treatment caused expansion and shrinking of the
wood veneer and rough surface of the WF/PP base board. The
D
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Table 3. Ratio of Cl in the CPP/PP Compound Film (%)
element
CPP/PP
CPP side
PP side
cross-section
C
Cl
C
Cl
C
Cl
atomic mass
atomic number
75.37
89.91
24.63
10.09
99.8
99.93
0.2
0.07
92.83
97.43
7.17
2.57
Figure 10. Distribution of oxygen on the WF/PP surface for the (a)
60 WF/40 PP; (b) 70 WF/30 PP; and (c) 80 WF/20 PP composites.
Table 4. Ratio of Oxygen on the WF/PP Surfaces
element
WF/PP composite 60 WF/40 PP
70 WF/30 PP
80 WF/20 PP
C
O
C
O
C
O
atomic mass
atomic number
93.72
95.21
6.28
4.79
91.25
93.29
8.75
6.71
85.23
88.49
14.77
11.51
Figure 9. Distribution of Cl in the CPP/PP compound film. (a,b)
Cross-section of the compound film; (c,d) CPP surface; and (e,f) PP
surface.
60 WF/40 PP veneered composite sample had a delamination
length of 5.5 mm, and the delamination lengths of the 70 WF/
30 PP and 80 WF/20 PP composites were 0.4 and 0 mm,
respectively. Thus, the delamination length shortened with an
increasing WF content in the WF/PP material. The results
indicated that the bond between the WF/PP composite-CPP-
poplar wood board would withstand water intrusion and the
strain of wood deformation. The bond strength was analyzed
using SEM−EDS and ATR−FTIR.
3.3. Poplar Wood and CPP Interface. Figure 6 shows the
glue line of the CPP film in the veneered WF/PP composites.
There was no crevice between the CPP layer and the wood
veneer, which indicated a firm bond. The CPP melted at 110
°C and penetrated into the wood conduits under pressure.
After the cooling press, the CPP hardened and adhered to the
wooden conduit wall. The glue line of the control laminate
composite (laminate veneer and WF/PP without a CPP film)
could not be observed because it could not withstand the
impact force from sample preparation and separated at the
bond line. Without the CPP intermediate layer, the bond
strength between the veneer and WF/PP board was weak.
Figure 7 shows section views of the slices prepared (Section
2.5). The depth of penetration of CPP into the poplar wood
veneer was 0.5−0.6 mm (Figure 7b). This deep penetration
Figure 11. Surface chemical groups of the WF/PP base board.
provided a stable anchoring structure between CPP and the
wood board. For the wood veneer/PP lamination without the
intermediate CPP layer (Figure 7a), the PP penetrated only
0.3−0.4 mm into the wood veneer, that is, shallower than CPP.
This created an obvious crevice between PP and the pore wall
because nonpolar PP could not adhere to the polar surface of
the wood.
CPP is more polar than pure PP because of the Cl grafting
on the molecular chains. This allows it to bond more closely
with the wood conduit wall. CPP also has a higher MFR than
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Figure 12. Surface contours of WF/PP composites. (a) 60 WF/40 PP; (b) 70 WF/30 PP; and (c) 80 WF/20 PP.
Table 5. Surface Roughness of the WF/PP Base Board
Composites
PP molecule chains, thus forming an absorption structure. To
illustrate this, the CPP film and PP film were laminated at a
temperature of 110 °C. Both sides of the compound film were
scanned, and the number and Cl atomic mass of the scanned
surface are shown in Table 3. On the CPP side, the atomic
mass and Cl content was much greater than on the PP side.
Figure 9a,b shows a cross-section of the PP/CPP compound
film in which Cl is distributed in a limited region. This
indicated that the PP and CPP molecular chains were not
remarkably diffused and mixed. Figure 9c,d shows the CPP
surface of the compound film where high Cl content was
detected. On the PP side of the compound film (Figure 9e,f),
the Cl content was low, showing that the CPP molecular
chains could not diffuse to this side.
As shown in Figure 6c, there was no crevice between the
CPP layer and WF/PP composite for the sample that
contained 80 mass part WF, however, small gaps were
observed (Figure 6a,b) for the composite with 60 and 70
mass part WF. The WF content in the composite therefore
influenced the interface bonding between CPP and WF/PP.
The roughness and specific area of the WF/PP base board was
affected by the exposed WFs. High WF content provided the
base board with more exposed WFs, as explained below
(Sections 3.5 and 3.6).
WF/PP composite
Ra (μm)
Rz (μm)
Rq (μm)
60 WF/40 PP
70 WF/30 PP
80 WF/20 PP
1.583
2.080
3.206
9.069
12.501
19.090
2.048
2.680
4.098
PP and therefore could penetrate deeper into the porous wood.
These factors greatly improved the bonding strength between
the wood veneer and WF/PP composite base board.
3.4. WF/PP and CPP Interface. The bonding condition
between the CPP and WF/PP composite was a very important
factor to the surface bonding strength of the veneered
composite. The WF/PP composite surface assembled a PP
layer during the extrusion molding process. This PP layer
would combine with the molten CPP during the hot-press.
Because CPP has a similar molecular structure to PP (Figure
8), it is potentially easy for CPP to adhere to the PP surface.
Wood veneer was laminated with the WF/PP composite at
110 °C, which was lower than the melting point of PP (168
°C). The PP molecular chains deformed and displaced in a
very limited range rather than move freely. However, CPP
melted at 110 °C and moved freely into the interspace of the
Figure 13. Interface bonding mechanism of the veneered WF/PP composite board.
F
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3.5. Elements on the WF/PP Composite Surface.
Figure 10 shows the distribution of oxygen on the surface of
the WF/PP composite. Oxygen is mainly contained in the
hydroxy and carbonyl forms in WF. The carbonyl content of
MAPP can be ignored as it is negligible. Therefore, we
considered the content and distribution of oxygen as the
exposed WF on the surface of the WF/PP composite.
Compared to the 70 and 80 mass part WF composites, the
60 mass part WF composite (Figure 10a) showed the least
oxygen distribution. Combining the atomic mass and atomic
numbers listed in Table 4, it was obvious that the amount of
oxygen increased with the increasing WF content in the WF/
PP composite. This indicated that more WF would extrude out
and increase the polarity of the surface after processing.
This phenomenon was in line with the results of the ATR−
FTIR test shown in Figure 11. The strength of the “−OH”
characteristic peak between 3150 and 3500 cm−1 represents
the WF and intensified with the increasing WF content in the
WF/PP composites. Meanwhile, the characteristic peak of the
WF at 1744 cm−1 (stretching vibration of CO of acetyl and
carboxyl groups in hemicelluloses and carbonyl aldehyde in
lignin and extractives) was also enhanced. These changes in
peak strength indicated the WF content. On the other hand,
increased fiber would increase the polarity of the base board
surface, thus affecting its surface bonding affinity with other
materials.
3.6. WF/PP Composite Surface Roughness. Surface
roughness is an important factor affecting bond strength.21,22
As shown in Figure 12, the surface contour height range
increased with an increasing WF content in the WF/PP
composite. Those rough surfaces could provide more specific
surface area and embedded groove for molten CPP. Surface
roughness parameters were calculated based on ISO
4287:1997 and are listed in Table 5. Ra and Rq represented
the surface roughness, the higher value, respectively, which
indicated greater roughness. Rz represented the maximum
height from the lowest point to the highest. The Ra, Rq, and Rz
parameters of WF/PP composites all increased with the
increasing WF content. As stated above, this surface roughness
was because of the exposed WFs, which did not form a smooth
surface like PP. This roughness was a benefit for binding with
CPP.
surface decoration. SEM−EDS and ATR−FTIR showed the
amount of exposed WF on the surface of the WF/PP
composite. The WF content of the WF/PP positively
correlated with the surface bonding strength. The exposed
WF on the WF/PP composite increased the surface roughness
and polarity, promoting the formation of a strong surface bond.
Thus, the bonding strength increased with an increasing WF
content in the WF/PP base material.
AUTHOR INFORMATION
Corresponding Author
*E-mail: weihongwang2001@nefu.edu.
■
ORCID
Yinan Liu: 0000-0002-8785-4011
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
This work was supported by the National Natural Science
Foundation of China (31670573), Provincial Natural Science
Foundation of Heilongjiang (ZD2016002), and the 2017
Special Project of Sustainable Development for Central
University Innovation Team of the Ministry Educatio-
n(2572017ET05). We thank International Science Editing
(http://www. Internationalscienceediting.com) for editing this
manuscript.
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Based on the above investigation of the combined interfaces
between the wood veneer, CPP layer, and WF/PP composite,
the bonding model between polar wood veneer and nonpolar
WF/PP board was proposed as shown in Figure 13. At a
temperature of 110 °C CPP can melt and infiltrate into the
porous wood veneer forming a firm anchoring structure.
Though CPP and PP do not diffuse and mix at this
temperature, they have similar molecular structures and form
strong van der Waals forces between.
4. CONCLUSIONS
WF/PP is manufactured with recycled material and without
the emission of volatile organic compounds. If its surface was
more aesthetically pleasing, it could be used for interior
decoration and furniture preparation. In this study we
investigated CPP as an intermediate layer to bond poplar
wood veneer to the WF/PP composite. The result was
satisfactory.
All the veneered composite samples with a CPP bonding
layer had good water resistance. The surface bonding strength
could reach 1.2 MPa and much higher than the requirement of
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DOI: 10.1021/acs.langmuir.9b02241
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DOI: 10.1021/acs.langmuir.9b02241
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