Poly(lactide acid) composites reinforced with fibers obtained from different tissue types of Picea sitchensis

Abstract

Wood fibers vary in their properties across species, across trees of the same species, and within single trees. This work takes advantage of wood fibers reinforcing poly(lactic acid) composites that originate from different tissue types of the species Sitka spruce (Picea sitchensis). Fibers were prepared with high temperature thermo-mechanical processing (TMP) from juvenile, mature, and compression wood tissues of Sitka spruce. Composites were made by solution casting with subsequent hot-pressing. Thermal as well as mechanical properties were determined using differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and tensile testing. The obtained results showed that the chemical and physical properties of different tissue-type Sitka spruce fibers have significant effects on the thermal and mechanical properties of the Polylactic acid (PLA)/ Sitka fiber composites. To increase interfacial compatibility between the hydrophilic fibers and the hydrophobic polymer matrix, the fibers were treated with vinyltrimethoxysilane (VTMO), while PLA was modified with 4,4-methylene diphenyl diisocyanate (MDI). It was found that PLA/Sitka composites treated with VTMO and MDI exhibited improved thermal and mechanical properties, compared to the unmodified control. The work also demonstrates that there is potential to improve biobased composites by utilizing the natural variability of wood fibers.

Mechanical and thermal properties of coconut shell powder filled polylactic acid biocomposites: effects of the filler content and silane coupling agent

“…However, treating the CSP with 3-APE led to an increase in the tensile strength of the PLA/CSP biocomposite, as the long alkyl chain of 3-APE covalently and hydrogen bonded to the surface of CSP via silane, which increased the hydrophobicity of CSP and thus enhanced the interfacial adhesion between the CSP and the PLA matrix. Some researchers have also found that 3-APE enhances the properties of PP/chitosan [16] and PP/wood [19] composites in a similar manner. The elongation at break of the PLA/CSP biocomposites decreased dramatically with filler content, as shown in Fig.…”

“…The T g values of the 3-APE-treated PLA/ CSP biocomposites were shifted to higher temperatures than those of the untreated biocomposites because the polymer chain mobility was reduced in the treated biocomposites by the increased physical entanglement between filler and matrix. Gregorova et al [19] reported that the T g values of PLA/sitka spruce fiber biocomposites also increased after treatment with silane coupling agent. The values of X c increased after treatment with 3-APE, as the nucleating effect of 3-APE enhances the filler-matrix interaction, as also noted by other researchers [16,19].…”

“…Gregorova et al [19] reported that the T g values of PLA/sitka spruce fiber biocomposites also increased after treatment with silane coupling agent. The values of X c increased after treatment with 3-APE, as the nucleating effect of 3-APE enhances the filler-matrix interaction, as also noted by other researchers [16,19]. On the other hand, the T c and T m values of the PLA/CSP biocomposites were not significantly affected by 3-APE treatment.…”

Thermal Properties of Poly(lactic Acid)

“…In addition, the incorporation of fiber can also cause changes to the thermal transition of PLA. One of the studies conducted by Gregorova et al (2009) found that the addition of 20 wt% of untreated natural fiber harvested from the plant species Picea sitchensis (which is also known as the Sitka spruce and grows in North America) causes a rise in T g to 52À54 C and the degree of crystallinity to 25.0À28.7%, with unchanged T m compared to the pure PLA. The PLA used possessed a T g of 46 C, a T m of 150 C and a degree of cystallinility of 18.2%.…”

Preparation and Characterization of Maleic Anhydride Compatibilized Poly(lactic acid)/Bamboo Particles Biocomposites

“…It is hydrolysable aliphatic semicrystalline polyester produced through direct condensation of its monomer, lactic acid, followed by a ring opening polymerization of the cyclic lactide dimmer. Lactic acid can be obtained from renewable resources such as polysaccharides [7]. However, PLA presents some drawbacks like high cost and relatively low heat resistance, which limit its broader applications [8].…”