Figures 1a and b illustrate the nail and screw withdrawal strength, respec- tively, of the composites made with various cellulosic ?ber types. WPCs made with poplar particles exhibit the highest nail and screw withdrawal strength, whereas samples ?lled with rice straw show the lowest properties. Average nail withdrawal strength ranges from 40.4 to 58.5 N/mm for poplar ?our WPCs, while maximum screw withdrawal strength is approximately 306 N/mm. The determined withdrawal strength values were the lowest for rice straw material. indoor plastic lumber Shade landscapeThe reasons for these may be the lower density of composites ?lled with rice straw. The mechanical properties of WPCs depend on the properties of constitu- ents and the interface interaction. However, when consid- ering the withdrawal strength, homogeneity of the overall composite needs to be taken into account .

At certain amount of ?ber content, the different withdrawal strengths among the manufactured panels can be attributed to the role of ?ber size. The effect of particle size on the mechanical properties investigated in this study is highly signi?cant . In general, increasing ?ber size improves both nail and screw withdrawal strength proper- ties. As it can be seen from Figs. 1a and b, composites ?lled with the 20–40 mesh ?ber improved the fastener strengths much more than the 40–60 mesh. This result is consistent with previous reports on wood-particle thermo- plastic composites .Fungistatic super foam insulation Various parameters in?uence the withdrawal strength of WPCs including the ?ber aspect ratio, ?ber-matrix adhesion, stress transfer at the interface and mixing temperatures. Results also showed that different size of poplar and rice straw had signi?cant effect on density . The highest values were observed in samples containing 20–40 mesh of cellulosic ?bers.

With decreasing size of poplar ?our (40–60 mesh), the density values were sig- ni?cantly decreased. A similar trend can also be seen in the values of composite made with rice straw.The composites made with extrusion method and ?lled with 75 wt% cellulosic ?bers showed the highest values for density amongst the composites evaluated, white ceiling boards tongue and groovewhereas com- posites with 75 wt% ?ber and fabricated with hot-pressing method exhibited the lowest densities. In hot-pressing method, the volumes of the panels are almost ?xed, hence, with increasing the ?ber content from 45 to 75 wt% the densities decreased.