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Agar obtained from the red alga Hydropuntia cornea was blended with polyvinyl alcohol (PVOH) in order to produce biodegradable films. In this study, we compare the properties of biopolymeric films formulated with agars extracted from H. cornea collected at different seasons (rainy and dry) in the Gulf of Mexico coast and PVOH as synthetic matrix. The films were prepared at different agar contents (0%, 25%, 50%, 75%, and 100%) and their optical, mechanical, thermal, and morphological properties analyzed. The tensile strength of PVOH-agar films increased when agar content was augmented. The formulation with 50% agar from rainy season (RS) had a significant higher tensile strength when compared to those from dry season (DS; p < 0.05). Tensile modulus also displayed an increasing trend and likewise, for 50% and 75% agar blends from RS showed higher values than those from DS (p < 0.05). In contrast, elongation at break decreased as the agar content increased, independently of the season. Environmental scanning electron microscopy images of PVOH-agar 75% biofilms from RS showed a homogeneous structure with good interfacial adhesion between the two components. The changes evidenced in the FTIR spectrum of this blend suggest that hydrogen bonding is taking place between the agar ether linkages (C-O-C) and the hydroxyl groups (OH) of the PVOH. Based on the above mentioned results, blends of PVOH and 75% agar from H. cornea collected in rainy season showed good properties for applications in the biodegradable packaging industry.

A series of biocomposites were developed by reinforcing agar particles from red marine plant Gelidium robustum into poly(butylene adipate‐co‐terephatalate) (PBAT) using extrusion and injection molding technique. The effect of different content of agar (0, 10, 20, 30, and 40 wt%) on the physico‐mechanical properties of the biocomposite was evaluated. The dynamic mechanical behavior of the composites was studied to determine the storage and loss modulus. The incorporation of agar particles into PBAT enhanced the tensile strength and modulus with a reduced percentage of elongation at break. A reduction in the mechanical loss factor (tan δ) was noticed with the addition of agar particles into PBAT. A reverse trend was noticed for storage and loss modulus. The thermogravimetric analysis revealed that the degradation temperature of PBAT‐agar composites lies in between that of their individual components (agar and PBAT). An increase in melting (Tm) and crystallization (Tc) temperature of the biocomposites were noticed as agar particle content increased. The rheological study carried out by dynamic frequency experiments demonstrated that viscosity is increased with the presence of agar particles. The morphology of the biocomposites was analyzed using scanning electron microscope. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers

The mucilage obtained from cladodes of Opuntia spinulifera has been used in industries and traditional applications. In the present work, the chemical, morphological, thermal and structural features of cladode mucilage from Opuntia spinulifera Salm-Dyck were studied. The 2D 1 H-1 H COSY NMR confirmed ten different residues within the repeating saccharide unit, six with α and four with β configurations. The FTIR showed the presence of galactose and pectins. The XRD detected minerals as calcium salts. The SEM exhibited aggregations and irregular morphology of the particles. The TGA registered the highest mass loss between 246-378°C and the DSC showed the transition state at 55.7°C and at 113.2°C was observed the typical endothermic peak, where it corresponds to the organic compound materials. Mucilago de cladodios de Opuntia spinulifera Salm-Dyck: caracterización química, morfológica, estructural y térmica RESUMEN El mucilago obtenido de cladodios de Opuntia spinulifera ha sido utilizado en varias industrias y en aplicaciones tradicionales. En el presente estudio, se estudiaron las características químicas, morfológicas, térmicas y estructurales del mucilago proveniente de cladodios de Opuntia spinulifera Salm-Dyck. La espectroscopía de correlación-resonancia magnética nuclear (EC-RMN) de 1 H-1 H en 2D confirmó la existencia de 10 residuos diferentes al interior del grupo sacárido que se repite, seis con configuraciones α y cuatro con configuraciones β. El espectrofotómetro de transformada de Fourier (FTIR) constató la presencia de galactosa y pectinas. La difracción de rayos X (DRX) detectó la existencia de minerales en forma de sales de calcio. La microscopía electrónica de barrido (MEB) reveló la presencia de agregaciones, así como la morfología irregular de las partículas. El análisis termogravimétrico (ATG) registró la mayor pérdida de masa entre 246-378°C, mientras que la calorimetría diferencial de barrido (DSC) precisó que se produjo un estado de transición a los 55.7°C, observándose el pico endotérmico típico de los materiales orgánicos compuestos a los 113.2°C.