Influence of the Degradation Medium on Water Uptake, Morphology, and Chemical Structure of Poly(Lactic Acid)-Sisal Bio-Composites

Abstract

A series of poly(lactic acid) (PLA) and poly(lactic acid)-based bio-composites (sisal PLA) were prepared and studied by spectroscopic and microscopic techniques as such and after immersion at room temperature in different degradation mediums (i.e., distilled and natural sea water and solutions at pH = 2, 6, and 8). In these conditions, some of their macroscopic and microscopic properties were monitored during a period of 30 days. Water absorption increased with the increasing fiber content regardless of the immersion medium. The maximum water absorption was achieved at pH = 8 (~16%), indicating a more severe action of the alkaline mediums on the samples. The diffusivity, D, of PLA decreased with the addition of fibers and acidic mediums showed higher D, indicating higher diffusivity of water through the specimens with respect to those submerged in moderate or alkaline mediums. Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) analysis evidenced a weak interaction between the PLA matrix and the sisal fibers. Very limited degradation phenomena occur in our conditions: Despite some changes in the microstructure, the PLA backbone seems to be largely resistant to hydrolysis, almost regardless of the pH value and even at the highest sisal content.

Viscoelastic Properties of Epoxidized Natural Rubber/Poly(lactic acid) PLA/ENR Blends Containing Glycidyl-POSS and Trisilanolisooctyl-POSS as Functional Additives

“…Poly(lactic acid) is one of the most readily degradable thermoplastic materials. The factors influencing on the mechanism and speed of PLA degradation under various environmental conditions were analyzed by many authors [8][9][10][11][12][13][14][15]. The main mechanism of PLA degradation is hydrolytic degradation or enzymatic degradation.…”

“…The most important factor influencing on PLA degradation carried out under natural and laboratory conditions are: the amount of D-lactide isomer in chain structure [13] and the degree of PLA crystallinity [14]. The rate of PLA hydrolysis is also strongly affected by the degradation conditions such as: temperature, humidity, and pH [9,11,15]. Moliner et al [11] reported for PLA samples after immersion during 30 days at room temperature in various aqueous solutions at different pH the limited hydrolysis of the ester bonds in PLA and the formation of few free alcoholic and carboxylic groups.…”

Dielectric, vibrational and thermal properties of sisal fibers‐reinforced poly (lactic acid)

“…Figure 3 presents all characteristics absorption peaks of neat PLA, PLA10 and PLA20. IR reveals the presence of characteristic band absorptions: (i): 2996-2884 cm −1 , the asymmetric and symmetric stretching vibrations of CH 3 , (ii): 1747 cm −1 , an important characteristic band comes from the C O stretching, [10,35] (iii): 1475-1360 cm −1 , these other bends approximately come from the CH 3 and CH bending, (iv): 1270 cm −1 relative to the COC stretching vibration, (v): 1186-1031 cm −1 , the bands of the C O stretching of the CH(CH 3 ) OH end group of PLA [36,37] and (vi): 870-759 cm −1 , the C C stretching vibration and the C COO stretching band, respectively. [38] According to Figure 3, the incorporation of sisal fibers into PLA matrix produces some modifications in spectral regions.…”

“…[8,9] Additional researches on PLA considered its use for applications in textiles, adhesive, agriculture products and packaging [5] due to its thermoplastic processing capacity and biodegradability properties under particular conditions. [10] However, its fragile character persists as it demonstrates a poor rigidity and low elongation at break, and its degradation rate remains slow. [1,2] Research has been carried out to resolve these defects by copolymerizing with other monomers, biocompatible plasticizers or nucleating agents.…”

Evaluation of the Mechanical and Biocidal Properties of Lapacho from Tabebuia Plant as a Biocomposite Material

“…Therefore, in various industries, such as packaging, automotive, construction, pharmaceutical, biotechnology, or horticulture, there is a growing demand for natural fibers. The rapid growing researches of biocomposites and their growing importance in the industry are reflected by the volume of publications or patents during the recent years [ 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 ].…”