Abstract
The purpose of this study is to compare the characteristics of wood–plastic composites (WPCs) made of polypropylene (PP) and wood fibers (WFs) from discarded stems, branches, and roots of pomelo trees. The results show that the WPCs made of 30–60 mesh WFs from stems have better physical, flexural, and tensile properties than other WPCs. However, the flexural strengths of all WPCs are not only comparable to those of commercial wood–PP composites but also meet the strength requirements of the Chinese National Standard for exterior WPCs. In addition, the color change of WPCs that contained branch WFs was lower than that of WPCs that contained stem or root WFs during the initial stage of the accelerated weathering test, but the surface color parameters of all WPCs were very similar after 500 h of xenon arc accelerated weathering. Scanning electron microscope (SEM) micrographs showed many cracks on the surfaces of WPCs after accelerated weathering for 500 h, but their flexural modulus of rupture (MOR) and modulus of elasticity (MOE) values did not differ significantly during weathering. Thus, all the discarded parts of pomelo trees can be used to manufacture WPCs, and there were no significant differences in their weathering properties during 500 h of xenon arc accelerated weathering.
Highlights
As one of the most important families of fruits in the world, the large citrus family includes sweet oranges (Citrus sinensis), mandarins or tangerine oranges (C. reticulata), sour/bitter oranges (C. aurantium), lemons (C. limon), limes (C. aurantifolia), and grapefruit (C. paradisi), with global production numbering over 120 million tons per year [1,2]
The sample codes of various wood–plastic composites (WPCs) were described as WPCXYY, where X represents the wood fibers (WFs) from the discarded parts of pomelo trees (B: branch; R: root; S: stem), and YY is the maximum size of WFs used in the given composite
Juvenile wood has a lower density and higher hemicellulose content compared to mature wood [42], which results in greater hygroscopicity for the WPCs made of branch WFs than the WPCs made of WFs from roots and stems
Summary
As one of the most important families of fruits in the world, the large citrus family includes sweet oranges (Citrus sinensis), mandarins or tangerine oranges (C. reticulata), sour/bitter oranges (C. aurantium), lemons (C. limon), limes (C. aurantifolia), and grapefruit (C. paradisi), with global production numbering over 120 million tons per year [1,2]. Pruning produces many useless twigs, branches, and stems that become agricultural waste, approximately 2250–13,500 tons per year. If this woody waste can be recycled and reused, it will increase the commercial value of local crops. The objective of the present study was to compare the physico-mechanical characteristics of WPCs made of PP and various sizes of wood fibers (WFs) from different discarded parts of pomelo trees. To the best of our knowledge, this is the first comparative study concerning the weathering characteristics of WPCs containing WFs from different discarded parts of fruit trees.
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