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Chitosan (CS) is often used in hydrogels due to its natural origin, sustainability, non‐toxicity, and biodegradability. However, the physicochemical properties of CS hydrogels generated via physical cross‐linking are relatively poor. CS hydrogels were prepared by cross‐linking with glutaraldehyde (GA) at different ratios ranging from 1% to 10% (w/w), using two different molecular weight CS. The swelling degree of hydrogels was investigated at pH 2.0, 5.6, and 7.4. The structure, morphology, and thermal characteristics of hydrogels were examined using Fourier transform infrared, scanning electron microscopy, differential scanning calorimetry, and thermogravimetric analysis, respectively. Compression tests were conducted using Zwick/Roell universal testing equipment following ASTM D695. In vitro degradation studies were performed in enzyme and enzyme‐free mediums at pH 7.4. The study demonstrated that low molecular weight CS (L‐CS) hydrogels have a lower sol content and higher swelling values than medium molecular weight CS (M‐CS) hydrogels. Both L‐CS and M‐CS hydrogels cross‐linked with 1% GA showed maximum swelling degrees at pH 2.0. Thermal analysis concluded that M‐CS hydrogels have higher thermal stability than L‐CS hydrogels. It was also found that the M‐CS hydrogels have higher compressive moduli. The degradation experiments in both enzyme and enzyme‐free media showed that L‐CS hydrogels have higher degradation rates. Highlights: Chemically cross‐linked hydrogels synthesized using low and medium molecular weight chitosan.The mechanical and physical properties of medium and low molecular weight chitosan hydrogels were compared.Degradation experiments were performed in both enzyme and enzyme‐free media.Swelling values decreased noticeably with the increasing molecular weight.Low molecular weight chitosan improved the biodegradability of hydrogels. [ABSTRACT FROM AUTHOR]

Poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV), member of the polyhydroxyalkanoate family, was generated from waste vegetable oil in a lab‐scale bioreactor and filled with pistachio shell (S) flour to produce fully agro‐industrial waste derived biodegradable low‐cost composites via melt mixing. To improve the interfacial interaction, maleic anhydride (MA) grafted PHBV (PHBV‐MA) was used as a compatibilizer and pretreatment of S (TS) was realized with silanization+alkalization process. The effects of filler percentage, compatibilizer, and S modification on the mechanical, thermal, morphological, water absorption, and biodegradability properties of the composite were studied. The crystallization percentage and temperature of PHBV were found to be higher in the composites, as compared with neat PHBV, due to nucleation effect of S/TS fillers. The increased tensile strength/modulus were achieved with composites including both PHBV‐MA compatibilizer and TS filler. The PHBV/PHBV‐MA/TS composite reinforced with 40% TS filler increased the tensile strength and modulus of the neat PHBV by 62.1% and 45.3%, respectively. Morphological analysis revealed that samples containing PHBV‐MA, or TS, have better surface wetting and interfacial adhesion than those without. The biodegradation of composites was studied over a 180 days of burial in soil. Biodegradation increased in tandem with the increase of the filler ratio in the PHBV composite from 20% to 40%. Biocomposites with 40% S/TS filler lost more than 90% of their weight, while the neat PHBV lost only 23.5%. Water absorption studies confirmed the biodegradability findings, with TS slightly reducing absorption capacity among the 40% filled samples due to the hydrophobicity effect of the silanization pretreatment. [ABSTRACT FROM AUTHOR]