Because wood–plastic composites (WPC) strength relies on fiber-matrix interaction at fiber surface, it is
likely that fiber surface chemistry plays an important role in WPC strength development. The objective
of the present study is to investigate the relationships between fiber surface chemical characteristics and
WPC mechanical properties. Different fibers were selected and characterized for surface chemical characteristics
using X-ray photoelectron spectroscopy (XPS) and infrared spectroscopy (FTIR). WPC samples
were manufactured at 40% fiber content and with six different fibers. High density polyethylene was used
as matrix and maleated polyethylene (MAPE) was used as compatibility agent. WPC samples were tested
for mechanical properties and fiber-matrix interface was observed with scanning electron microscope.
It was found WPC strength decreases as the amount of unoxidized carbon (assigned to lignin and extractives)
measured with XPS on fiber surface increases. In the opposite case, WPC strength increases with
increasing level of oxidized carbon (assigned to carbohydrates) on fiber surface. The same conclusions
were found with FTIR where WPC strength decreases as lignin peaks intensity increases. Esterification
reaction of fibers with MAPE occurs on polar sites of carbohydrates, such as hydroxyls (O H). Thus,
fibers with carbohydrates-rich surface, such as cellulose pulp, produced stronger WPC samples. Other
factors such as mechanical interlocking and fiber morphology interfered with the effects of fiber surface
chemistry
Because wood–plastic composites (WPC) strength relies on fiber-matrix interaction at fiber surface, it islikely that fiber surface chemistry plays an important role in WPC strength development. The objectiveof the present study is to investigate the relationships between fiber surface chemical characteristics andWPC mechanical properties. Different fibers were selected and characterized for surface chemical characteristicsusing X-ray photoelectron spectroscopy (XPS) and infrared spectroscopy (FTIR). WPC sampleswere manufactured at 40% fiber content and with six different fibers. High density polyethylene was usedas matrix and maleated polyethylene (MAPE) was used as compatibility agent. WPC samples were testedfor mechanical properties and fiber-matrix interface was observed with scanning electron microscope.It was found WPC strength decreases as the amount of unoxidized carbon (assigned to lignin and extractives)measured with XPS on fiber surface increases. In the opposite case, WPC strength increases withincreasing level of oxidized carbon (assigned to carbohydrates) on fiber surface. The same conclusionswere found with FTIR where WPC strength decreases as lignin peaks intensity increases. Esterificationreaction of fibers with MAPE occurs on polar sites of carbohydrates, such as hydroxyls (O H). Thus,fibers with carbohydrates-rich surface, such as cellulose pulp, produced stronger WPC samples. Otherfactors such as mechanical interlocking and fiber morphology interfered with the effects of fiber surfacechemistry
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