Effect of biological degradation by termites on the flexural properties of pinewood residue/recycled high‐density polyethylene composites

Abstract

Wood-plastic composites (WPCs) are considered to be highly durable materials and immune to any type of biological attack. However, when one of these composites is exposed to accelerated weathering, its surface is affected by the appearance of cracks, which constitute an ideal access route for biotic agents. Although the destruction of wood caused by termites is recognized worldwide, information on their effects on WPC-based products is scarce. Thus, in this study, we aimed to examine the effects of termite attacks on weathered and nonweathered pinewood residue/recycled high-density polyethylene composites. In this study, WPCs with 40 wt % wood were prepared. Test samples obtained by compression molding and profile extrusion were subjected to weathering cycles for 1000 and 2000 h with a UV-type accelerated tester equipped with UVA-340 fluorescent lamps. Afterward, specimens were exposed to the attack of higher termites (Nasutitermes nigriceps) native to the Yucatan Peninsula. Subsequently, flexural mechanical essays, Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), and scanning electron microscopy (SEM) analyses were performed. FTIR spectroscopy and DSC showed that the surfaces of the compression-molded specimens were degraded to a higher extent because of the accelerated weathering. The microscopy results revealed that severe damage was caused by the termites on the surface of the compression-molded samples. Statistical analysis of the mechanical test results showed that biotic attack produced significant changes in the samples previously exposed to accelerated weathering. The results show that the processing method directly affected the sample performance because of differences in the surface composition. The profile-extruded composites seemed to better resist termite attack.

On the Use of Gallic Acid as a Potential Natural Antioxidant and Ultraviolet Light Stabilizer in Cast-Extruded Bio-Based High-Density Polyethylene Films

“…Figure 2 shows the dynamical DSC curves of the cast-extruded bio-HDPE films, whereas Table 3 summarizes the main thermal parameters obtained from the curves. One can observe that, in all cases, the polyolefin melted sharply in a single peak at approximately 132 • C. A similar melting profile has been observed previously for this polyolefin, regardless of the origin and the methodology followed to prepare the articles [37,44]. It can also be seen that the ∆H m values of bio-HDPE slightly reduced as the GA content in the green polyolefin increased.…”

Effect of natural ageing on the properties of recycled polypropylene/ethylene vinyl acetate/wood flour composites

“…Finally, after 12 months of exposure was possible to distinguish three small endotherms peaks before melting the PP, that could be related to the secondary recrystallization of short polymer segments produced by chain-breaking reactions on polypolypropylene after natural ageing. This behavior was also observed by López-Naranjo et al [25], who observed that because of accelerated weathering new thermal energy absorption peaks (shoulders at about 110 ºC) appeared on their material. In Figure 7 are shown comparative TGA curves of the composites before and after natural ageing and Table 3 shows the TGA numeric results.…”

Interfacial Shear Strength Evaluation of Pinewood Residue/High-Density Polyethylene Composites Exposed to UV Radiation and Moisture Absorption-Desorption Cycles

“…On the other hand, the compounds formed by the photo-oxidation of lignin were solubilized by water and lixiviated. These results are in good agreement with what is reported in the literature (Stark and Matuana 2004;Stark 2006;Fabiyi et al 2008;Fabiyi and McDonald 2010;López-Naranjo et al 2013). Regarding the carboxylate anion index shown in Table 4, it is generally observed that it was similar for the materials with 0% coupling agent (UV-irradiated or not), subjected to 0 and 4 MADCs.…”

“…The peak intensities were normalized using the peak at 2917 cm -1 , corresponding to the alkane C-H stretching vibrations of methylene groups. This peak was chosen as a reference because it changed the least with weathering (Stark and Matuana 2004;López-Naranjo et al 2013). The amount of lignin and the possibility of hydrolysis in the samples were respectively quantified by means of the lignin and carboxylate anion indexes (the carboxylate anion is a hydrolysis product).…”