Use of Biochar as Filler for Biocomposite Blown Films: Structure-Processing-Properties Relationships

Abstract

In this work, biocomposite blown films based on poly(butylene adipate-co-terephthalate) (PBAT) as biopolymeric matrix and biochar (BC) as filler were successfully fabricated. The materials were subjected to a film-blowing process after being compounded in a twin-screw extruder. The preliminary investigations conducted on melt-mixed PBAT/BC composites allowed PBAT/BC 5% and PBAT/BC 10% to be identified as the most appropriate formulations to be processed via film blowing. The blown films exhibited mechanical performances adequate for possible application as film for packaging, agricultural, and compost bags. The addition of BC led to an improvement of the elastic modulus, still maintaining high values of deformation. Water contact angle measurements revealed an increase in the hydrophobic behavior of the biocomposite films compared to PBAT. Additionally, accelerated degradative tests monitored by tensile tests and spectroscopic analysis revealed that the filler induced a photo-oxidative resistance on PBAT by delaying the degradation phenomena.

Biochar Particles Obtained from Agricultural Carob Waste as a Suitable Filler for Sustainable Biocomposite Formulations

“…A reduction of C=O functional groups is clearly visible, since the decreasing and shifting of the neat peak in 1710 cm −1 , with a creation of a left shoulder, displays the formation of free C=O due to the occurring of chain scission by means of Norrish I scission reaction, according to the literature [ 35 , 45 ]. Moreover, the occurrence of Norrish II reaction can be related to the formation of free OOH and/or peroxide, which lead to the appearance of peaks/sholders at 3410 and 3440 cm −1 due to autocatalytic photo-oxidation reactions.…”

“…The dimensionless elongation at break of neat PBAT already highlights a significant reduction of its ductility behavior after 24 h of photo-irradiation, showing a half time of 14 h. To sum up, the dimensionless elongation at break curves after a complete cycle of photo-oxidation for biocomposites almost does not achieve the half time of elongation at break. Thus, adding BC particles delay aging phenomena, probably through both UV absorption (being carbonaceous particles) and scavenging action as proved by DPPH assay, discussed before, and according to the literature [ 35 ]. This behavior is more pronounced as the filler amount increases.…”

“…Interestingly, radical scavenging activity of this particles can be explained considering that a large amount of carbon atoms presented in these particles have sp 2 hybridization and some of them are able to change their hybridization to sp 3 upon irradiation, achieving scavenger ability. Botta et al [ 35 ] showed that biochar particles are also able to scavenger radical, retarding photo-oxidation phenomena in bio-polyester composites.…”

Blown Composite Films of Low-Density/Linear-Low-Density Polyethylene and Silica Aerogel for Transparent Heat Retention Films and Influence of Silica Aerogel on Biaxial Properties

“…However, when the strain values increased, a strain hardening mechanism developed, which may be a result of an orientated crystalline structure of polymer in both MD ( Figure 5 B) and TD ( Figure 6 B) [ 25 ]. Nanocomposites containing various SA concentrations (0.5–1.5%) showed different strain hardening mechanisms than the pure blend film, as was expected by considering the influence of SA dispersion on the polymer chain orientation along the blow direction during the film-blowing [ 27 ], which was also demonstrated by the yield point at low strain values ( Figure 5 A and Figure 6 A) and that, with an increase in SA content (0.5–1.5%), the yield stress and yield strain of the blown film, as shown in Table 2 and Table 3 , increased from 6.34–7.13%, and 9.92–11.49 MPa, respectively, for MD and by 7.77–8.28%, 6.11–8.25 MPa, respectively, for TD (i.e., the mechanical strength and flexibility increased as the SA content increased). The crystallinity of the blown film ( Table 4 ) was also influenced by the effect of SA on the molecular chain, as the molecular orientation decreased the polymer fractional free volume and molecular flexibility, and induced crystallinity [ 28 ].…”

The Use of Waste Hazelnut Shells as a Reinforcement in the Development of Green Biocomposites

“…[ 13 , 14 ] However, to date, the main disadvantages of most biodegradable polymers are their thermal resistance [ 15 , 16 ] and mechanical properties [ 17 , 18 ], which are inferior to those of conventional polymers. Therefore, recently, a very convenient solution to overcome or at least minimize the low ductility and toughness of biodegradables is biocomposites [ 19 , 20 , 21 , 22 , 23 ].…”