The thermo-oxidative durability of polyethylene reinforced with wood-based fibres

Enhancing Insight into Photochemical Weathering of Flax and Miscanthus: Exploring Diverse Chemical Compositions and Composite Materials

The accelerated weathering of flax and miscanthus fibers possessing distinct chemical compositions was investigated. The chosen fibers included raw, extractive-free (EF) and delignified samples (x3), alone and used as fillers in a stabilized polypropylene blue matrix (PP). Modifications in both color and the chemical composition of the fibers throughout the weathering process under ultraviolet (UV) light were meticulously tracked and analyzed by spectrophotometry and attenuated total reflectance with Fourier-transform infrared spectroscopy (ATR-FTIR). The inherent nature and composition of the selected fibers led to varied color-change tendencies. Raw and EF flax fibers exhibited lightening effects, while raw and EF miscanthus fibers demonstrated darkening effects. Extractives exhibited negligible influence on the color alteration of both flax and miscanthus fibers. This disparity between the fibers correlates with their respective lignin content and type, and the significant formation of carbonyl (C=O) groups in miscanthus. Better stability was noted for delignified flax fibers. A comparative study was achieved by weathering the PP matrix containing these various fibers. Contrary to the weathering observations on individual fibers, it was noted that composites containing raw and EF flax fibers exhibited significant color degradation. The other fiber-containing formulations showed enhanced color stability when compared to the pure PP matrix. The study highlights that the UV stability of composites depends on their thermal history. As confirmed by thermogravimetric analysis (TGA), fiber degradation during extrusion may affect UV stability, a factor that is not apparent when fibers alone are subjected to UV aging.

In situ degradation of low-density polyethylene film in irrigation maize field: Thickness-dependent effect

Thickness of low-density polyethylene (LDPE) film might determine its mechanical strength, clean production and soil health. Yet, this issue is little understood. In situ aging effects were evaluated in LDPE films with the thickness of 0.006 mm, 0.008 mm, 0.010 mm and 0.015 mm in maize field. The data showed that maximum tensile force (TFmax), maximum tensile strength (TSmax) and elongation at break (EAB) were massively lowered with increasing thickness after aging. The greatest and lowest reduction magnitude of EAB was 27.6 % and 11.2 % in 0.006 mm and 0.015 mm films respectively. Also, the melting point (Tm) and crystallinity (Xc) under Differential Scanning Calorimeter (DSC) tended to decline with the increasing thickness. Moreover, the peak intensity of crystalline regions tended to transfer and concentrate on the amorphous regions, and such tendency became more pronounced in the thin films. Interestingly, there existed a pronounced distinct thickness-dependent effects on soil bulk density (SBD) and soil water-stable aggregate proportion. Thick plastic film mulching increased SBD but reduced the proportion of macroaggregates (mainly referred to 0.015 mm and 0.010 mm). In addition, thick film mulching slightly reduced the levels of soil organic carbon (SOC) and total nitrogen (TN), but significantly promoted the contents of soil labile C and N. Particularly, it significantly promoted above- & under-ground biomass of maize across two growing seasons (p < 0.05). To sum up, thickening LDPE film may act as a promising solution to improve LDPE film residue recycling, while benefiting for higher productivity. However, thick film mulching may cause a certain adverse impact on soil structure, and further investigations would be needed in the future.

The Role of Inorganic-Organic Bio-Fillers Containing Kraft Lignin in Improvement in Functional Properties of Polyethylene

In this study, MgO-lignin (MgO-L) dual phase fillers with varying amounts of lignin as well as pristine lignin and magnesium oxide were used as effective bio-fillers to increase the ultraviolet light protection and enhance the barrier performance of low density polyethylene (LDPE) thin sheet films. Differential scanning calorimetry (DSC) was used to check the crystalline structure of the studied samples, and scanning electron microscopy (SEM) was applied to determine morphological characteristics. The results of optical spectrometry in the range of UV light indicated that LDPE/MgO-L (1:5 wt/wt) composition exhibited the best protection factor, whereas LDPE did not absorb ultraviolet waves. Moreover, the addition of hybrid filler decreased the oxygen permeability factor and water vapor transmission compared with neat LDPE and its composites with pristine additives, such as lignin and magnesium oxide. The strong influence of the microstructure on thin sheet films was observed in the DSC results, as double melting peaks were detected only for LDPE compounded with inorganic-organic bio-fillers: LDPE/MgO-L.