Development of films based on blends of Amaranthus cruentus flour and poly(vinyl alcohol)

The aim of this work was to develop biodegradable films based on blends of Amaranthus cruentus flour and poly(vinyl alcohol). Five different PVA types were tested. Blends with higher hydrolysis (HD) degree PVA were more resistant, showing greater tensile strength (TS) and puncture force (PF). However, the films with PVA with lower HD showed more flexibility, greater elongation at break (ELO) and greater puncture deformation (PD), with the exception of PVA 325. The latter was chosen due to it superior mechanical performance (TS = 10.2 MPa, ELO = 89.8%, PF = 9.4 N and PD = 16.3%). When films based on blends of amaranth flour and PVA 325 (10–50%) were evaluated, all mechanical properties were enhanced with increase in PVA 325 content. The solubility in water of the films made with PVA and amaranth flour decreased with increasing PVA content, reaching 44% of soluble matter for the 50% PVA film. The formation of hydrogen bonds between the blend components was confirmed by the FTIR spectra analysis.     

Improved blood biocompatibility of composite film of chitosan/carbon nanotubes complex

Single-walled carbon nanotubes are novel molecular-scale wires having excellent anti-adhesion properties with regard to platelets. On the other hand, chitosan is a partially de-acetylated derivative of chitin that has a critical role in cell attachment and growth. The aim of this study was to investigate how carbon nanotubes improve the blood biocompatibility of chitosan film. We prepared composite films with various concentrations of chitosan/carbon nanotubes (CS/CNTs) (1.3–6.3 wt%). The sample surfaces were characterized by Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and contact angle measurements. The surface characterization revealed that the surface of the CS/CNTs composite film became more hydrophobic with increasing amounts of CNTs. Cell attachment tests using bovine aortic endothelial cells (BAECs) indicated that CS/CNTs composite films retained their cell adhesion ability. The blood compatibility of the CS/CNTs composite films was evaluated using the blood platelet adhesion and activation tests in vitro. Platelet adhesion results confirmed that platelet adhesion and the formation of a platelet network were inhibited on composite films with higher concentrations of CNTs (5.1 wt%). Our experimental results show that the novel composite film containing CS/CNTs possesses two paradoxical characteristics, namely, good adherence of endothelial cells and minimum adherence and activation of platelets, making this film a promising antithrombogenic material for use in the biomedical field.     

Bionanocomposites based on pea starch and cellulose nanowhiskers hydrolyzed from pea hull fibre: Effect of hydrolysis time

By hydrolyzing pea hull fibres (PHF) for different times (t) with sulfuric acid, a series of pea hull fibre-derived nanowhisker (PHFNW-t) dispersions was prepared. The PHFNW-t dispersions were then blended with pea starch (PS) to fabricate bionanocomposite films (PS/PHFNW-t). The effect of t on the structure and properties of the PHFNW-t nanowhiskers and those of the corresponding PS/PHFNW-t nanocomposite films were investigated. The length (L), diameter (D) and L/D values of the PHFNW-t ranged from 240 to 400 nm, 7 to 12 nm, and 32.22 to 36.00, respectively. The PS/PHFNW-t nanocomposite films exhibited higher ultraviolet absorption, transparency, tensile strength, elongation at break, and water-resistance than both the neat PS film and the PS/PHF film (as a control with a t of 0 h). The PS/PHFNW-8 film showed the highest transparency, tensile strength, and elongation at break among the PS/PHFNW-t films, due to the high L/D of PHFNW-8. These results revealed that the length of hydrolysis time had a great effect on the structure (including L, D and L/D) of the PHFNW-t nanowhiskers, as well as on the structure and performance of the resulting PS/PHFNW-t films. For preparation of PHFNW-t nanowhiskers and corresponding PS/PHFNW-t films, the most suitable hydrolysis time, in this work, is 8 h.     

Characterization of Corn Starch Films Reinforced with CaCO3 Nanoparticles

The characterization of corn starch (CS) films impregnated with CaCO₃ nanoparticles was investigated. Criteria such as morphology, crystallinity, water vapor permeability (WVP), opacity, and mechanical properties were the focus of the investigation. It was found that the CaCO₃ contents had significant effects on the tensile properties of the nanocomposite films. The addition of CaCO₃ nanoparticles to the CS films significantly increased tensile strength from 1.40 to 2.24 MPa, elongation from 79.21 to 118.98%, and Young’s modulus from 1.82 to 2.41 MPa. The incorporation of CaCO₃ nanoparticles increased the opacity of films, lowered the degree of WVP and film solubility value compared to those of the CS films. The results of scanning electron microscopy (SEM) showed that with the increase of CaCO₃ nanoparticles content in starch films, the roughness of the films increased, and pores or cavities were found on the surface of the films, while small cracks were observed in the structures of the fractured surfaces. X-ray diffraction showed that the addition of nanoparticles increased the peaks in the intensity of films.     

Biodegradable starch based nanocomposites with low water vapor permeability and high storage modulus

Nanocomposite materials based on a starch matrix reinforced with very small amounts of multi-walled carbon nanotubes (MWCNTs) (from 0.005 wt% to 0.055 wt%) were developed. The material's dynamic-mechanical and water vapor permeability properties were investigated. An increasing trend of storage modulus (E′) and a decreasing trend of water vapor permeability (WVP) with filler content were observed at room temperature. For the composite with 0.055 wt% of filler, E′ value was about 100% higher and WVP value was almost 43% lower than the corresponding matrix values. MWCNTs were wrapped in an aqueous solution of a starch-iodine complex before their incorporation into the matrix, obtaining exceptionally well-dispersed nanotubes and optimizing interfacial adhesion. This excellent filler dispersion leads to the development of an important contact surface area with the matrix material, producing remarkable changes in the starch-rich phase glass transition temperature even in composites with very low filler contents. This transition is shifted towards higher temperatures with increasing content of nanotubes. So at room temperature, some composites are in the rubber zone while others, in the transition zone. Therefore, this change in the material glass transition temperature can be taken as responsible for the important improvements obtained in the composites WVP and E′ values for carbon nanotubes content as low as 0.05 wt%.     

A Novel Itraconazole Bioadhesive Film for Vaginal Delivery: Design, Optimization, and Physicodynamic Characterization

The purpose of this work was to design and optimize a novel vaginal drug delivery system for more effective treatment against vaginal candidiasis. Itraconazole was formulated in bioadhesive film formulations that could be retained in the vagina for prolonged intervals. The polymeric films were prepared by solvent evaporation and optimized for various physicodynamic and aesthetic properties. In addition, percentage drug retained on vaginal mucosa was evaluated using a simulated dynamic vaginal system as function of time. A polymeric film containing 100 mg itraconazole per unit (2.5 cm × 2.5 cm) have been developed using generally regarded as safe listed excipients. The pH of vaginal film was found to be slightly acidic (4.90 ± 0.04) in simulated vaginal fluid and alkaline (7.04 ± 0.07) in water. The little moisture content (7.66 ± 0.51% w/w) was present in the film, which helps them to remain stable and kept them from being completely dry and brittle. The mechanical properties, tensile strength, and percentage elongation at break (9.64 N/mm² and 67.56% for ITRF₆₅) reveal that the formulations were found to be soft and tough. The films (ITRF₆₅) contained solid dispersion of itraconazole (2.5)/hydroxypropyl cellulose (1)/polyethylene glycol 400 (0.5), which was found to be the optimal composition for a novel bioadhesive vaginal formulation, as they showed good peelability, relatively good swelling index, and moderate tensile strength and retained vaginal mucosa up to 8 h. Also, the film did not markedly affect normal vaginal flora (lactobacillus) and was noncytotoxic as indicated by the negligible decrease in cell viability.     

Properties of blend film based on cuttlefish (Sepia pharaonis) skin gelatin and mungbean protein isolate

Blend films based on cuttlefish (Sepia pharaonis) ventral skin gelatin (CG) and mungbean protein isolate (MPI) at different blend ratios (CG/MPI = 10:0, 8:2, 6:4, 4:6, 2:8 and 0:10, w/w) prepared at pH 11 using 50% glycerol (based on total protein) as plasticizer were characterized. CG films incorporated with MPI at increasing amounts had the decreases in tensile strength (TS) (p < 0.05). The increases in elongation at break (EAB) were observed when CG/MPI ratios of 6:4 or 4:6 were used (p < 0.05). Decreased water vapor permeability (WVP) was obtained for films having the increasing proportion of MPI (p < 0.05). CG/MPI blend films with higher MPI proportion had lower film solubility and L*-values (lightness) but higher b*-values (yellowness) and ΔE*-values (total color difference) (p < 0.05). Electrophoretic study revealed that disulfide bond was present in MPI and CG/MPI blend films. However, hydrogen bonds between CG and MPI in the film matrix were dominant, as elucidated from FTIR spectroscopic analysis. Moreover, thermal stability of CG/MPI blend film was improved as compared to that of films from respective single proteins. Differential scanning calorimetry result suggested solid-state morphology of CG/MPI (6:4) blend film that consisted of amorphous phase of partially miscible CG/MPI mixture and the coexisting two different order phases of individual CG and MPI domains. Thus, the incorporation of MPI into gelatin film could improve the properties of resulting blend film, which were governed by CG/MPI ratio.     

Characterization of Biosynthesized Silver Nanoparticles Using Lactobacillus rhamnosus GG and its In Vitro Assessment Against Colorectal Cancer Cells

Silver nanoparticles are the most desirable nanoparticles broadly used in diverse fields. This study intends to investigate the anticancer properties of synthesized silver/Lactobacillus rhamnosus GG nanoparticles (Ag-LNPs) as a reducing and stabilizing agent in the synthesis process. To prepare silver/Lactobacillus rhamnosus GG nanoparticles, 1 mg/ml cell lysate of Lactobacillus rhamnosus GG and 1 mM silver nitrate solution were mixed and incubated for 72 h. XRD, FTIR, and TEM methods were used for nanoparticle characterization. MTT assay and annexin/PI staining were employed to analyze the toxicity and apoptotic cells levels of Ag-LNPs, respectively. TEM showed that these nanoparticles are spherical shaped about 233 nm in size. FTIR spectroscopy demonstrated that Ag-LNPs were functionalized with biomolecules. XRD pattern showed high purity and face-centered crystal structure of Ag-LNPs. MTT assay revealed that the percentages of HT-29 live cells significantly reduced in the high concentration of Ag-LNPs. Annexin/PI staining showed that these nanoparticles could lead HT-29 cells to apoptosis. This study showed the new Ag-LNP-synthesizing method using Lactobacillus rhamnosus GG as a cost-effective and efficient approach. Also, it showed that these nanoparticles can be considered as a potential active agent for biomedical applications and drug delivery due to their anticancer activities.

     

The influence of nanoscopically thin silver films on bacterial viability and attachment

The physicochemical and bactericidal properties of thin silver films have been analysed. Silver films of 3 and 150 nm thicknesses were fabricated using a magnetron sputtering thin-film deposition system. X-ray photoelectron and energy dispersive X-ray spectroscopy and atomic force microscopy analyses confirmed that the resulting surfaces were homogeneous, and that silver was the most abundant element present on both surfaces, being 45 and 53 at.% on the 3- and 150-nm films, respectively. Inductively coupled plasma time of flight mass spectroscopy (ICP-TOF-MS) was used to measure the concentration of silver ions released from these films. Concentrations of 0.9 and 5.2 ppb were detected for the 3- and 150-nm films, respectively. The surface wettability of the films remained nearly identical for both film thicknesses, displaying a static water contact angle of 95°, while the surface free energy of the 150-nm film was found to be slightly greater than that of the 3-nm film, being 28.8 and 23.9 mN m⁻¹, respectively. The two silver film thicknesses exhibited statistically significant differences in surface topographic profiles on the nanoscopic scale, with R _a, R _q and R _max values of 1.4, 1.8 and 15.4 nm for the 3-nm film and 0.8, 1.2 and 10.7 nm for the 150-nm film over a 5 × 5 μm scanning area. Confocal scanning laser microscopy and scanning electron microscopy revealed that the bactericidal activity of the 3-nm silver film was not significant, whereas the nanoscopically smoother 150-nm silver film exhibited appreciable bactericidal activity towards Pseudomonas aeruginosa ATCC 9027 cells and Staphylococcus aureus CIP 65.8 cells, obtaining up to 75% and 27% sterilisation effect, respectively.     

Citric acid and maleic anhydride as compatibilizers in starch/poly(butylene adipate-co-terephthalate) blends by one-step reactive extrusion

Starch/poly(butylene adipate-co-terephthalate) films were obtained by one-step reactive extrusion using maleic anhydride (MA) and citric acid (CA) as compatibilizers. The mechanical, structural, optical and barrier properties of the films were analyzed when glycerol (GLY), CA and MA were added to the starch/PBAT (55:45, w/w) according to mixture design. FTIR analysis showed that CA and MA were able to promote esterification/transesterification reactions and that CA induced them more efficiently. When a greater proportion of compatibilizer (1.5 wt%) was used, the resulting films were more opaque and had a greater tensile strength. A greater proportion of GLY (10.0%, w/w) improved the elongation at the break of the films. The barrier properties to water vapor of the films were improved by high levels of CA (1.5 wt%) and intermediate levels of GLY (9.25 wt%). The inclusion of compatibilizers resulted in blends with improved properties, representing a potential replacement for non-biodegradable films.     

Divergicin M35-Chitosan Film: Development and Characterization

Chitosan films loaded with bacteriocin were examined by FTIR spectroscopy, tested for color, puncture strength, water vapor permeability, and as antimicrobials of Listeria innocua HPB13. Divergicin M35, a bacteriocin produced by Carnobacterium divergens, was incorporated into films made with chitosan of molecular mass 2 kDa, 20 kDa, or 100 kDa and de-acetylated either 87% or 95%. Only 100 kDa chitosan yielded films that could be peeled and handled easily. The higher degree of de-acetylation increased the total color factor (ΔE) of bacteriocin-loaded films, their permeability, and puncture strength. Incorporation of divergicin M35 into the films increased amide I peak intensity but otherwise did not induce significant structural change. The FTIR spectra of divergicin M35 shed from the films did not differ from those of the original free bacteriocin, except in overall peak intensity. The release of active divergicin M35 from the film was faster into the buffer than into tryptic soy broth and peaked at 10–12 h in both cases. Chitosan 95% de-acetylated and loaded with divergicin M35 was the most active, producing a six-log drop in Listeria innocua HPB13 viable count within 24 h. These results suggest that the biocompatible and biodegradable films developed here have the potential for application as antimicrobials of Listeria spp. in foods, especially ready-to-eat, minimally processed products.

     

Significantly Enhanced Electrostatic Energy Storage Performance of Flexible Polymer Composites by Introducing Highly Insulating‐Ferroelectric Microhybrids as Fillers

A hybrid nanoparticle, consisting of BaTiO₃ nanoparticles tightly embedded in bronnitride (BN) nanosheets, has been fabricated based on a daring supposition that BN may act as a host to incorporate ferroelectric nanoparticles to improve insulation and polarization under a high electric field. Using the hybrids as fillers in poly(vinylidene fluoride) (PVDF) composites, a high electric breakdown strength (E_b ≈580 kV/mm), which is 1.76 times of the PVDF film, is obtained when the filler content is 5 wt%. A large displacement (9.3 µC/cm² under 580 kV/mm) is observed so as to obtain a high discharged energy density (U_d ≈17.6 J/cm³) of the BT@BN/PVDF composites, which is 2.8 times of the PVDF film. The enhancement ratio of E_b achieved in this study demonstrates the highest among the reported results. This hybrid structure of fillers provides an effective way to adjust and improve the energy storage properties of the polymer‐based dielectrics.     

The influence of porosity on the hemocompatibility of polyhedral oligomeric silsesquioxane poly (caprolactone-urea) urethane

BackgroundThe physio-chemical properties of blood contacting biomaterials play an important role in determining their hemocompatibility. It is shown in literature that surface roughness and porosity have significant effect on hemocompatibility. In this study, we use a biocompatible, low thrombogenic nanocomposite polymer called POSS-PCU to test this hypothesis: would porosity compromise the hemocompatibility of POSS-PCU. We compared the hemocompatibility of POSS-PCU films of various pore sizes with PTFE, which is a commercially available material used in most blood contacting devices.MethodsSterilized POSS-PCU films with different size pores were prepared as samples and porous PTFE film were selected as control. And all samples were subjected to SEM for topograpgy, mechanical test for characterization and hemocompatibility tests to evaluate contact activation, platelet adhesion and activation, as well as whole blood clotting response to the samples.ResultsWCA significantly increased with the pore size of POSS-PCU film, whereas both tensile stress and strain decreased significantly as the sizes of pores increased. However, when compared to PTFE film with same size pores, POSS-PCU films showed both higher tensile stress and strain. Pore size had little impact over POSS-PCU's surface chemistry groups as tested by FTIR analysis. Contact activation and platelet adhesion essay also showed no significant difference between different POSS-PCU samples. However, in whole blood reactions, POSS-PCU with pores size around 2–5 μm showed higher BCI than plain films and those with pores size around 35–45 μm. POSS-PCU showed lower thrombogencity and higher hemocompatibility comparing with porous PTFE on the aspects of platelet activation, adhesion and whole blood reaction.Summary and conclusionsPOSS-PCU polymer films as a biomaterial in chronic blood contacting implants show significant lower thrombogencity and higher hemocompatibility than porous PTFE film. It is desirable as a coating or covering material in small diameter stents for treating cardiovascular diseases, cerebral vascular diseases and peripheral arterial diseases.     

Thermal, Mechanical and Microstructures Properties of Cellulose Derivatives Films: A Comparative Study

The proposal in this study was to evaluate the physical properties of different biopolymers films. The materials used were: pectin, carboxyl methylcellulose, methylcellulose, hydroxyl propylcellulose, hydroxypropyl-methylcellulose, and corn waxy starch; from these polysaccharides aqueous dispersions were prepared to 3% (w/v) for obtained films. In these biopolymer films, the thermal diffusivities (α) was evaluated by the Open Photoacoustic Cell method; also, their mechanical properties as tensile strength, elongation, and Young’s modulus were measured, their crystallinity percentage was evaluated by X-ray diffraction and microstructure through atomic force microscopy in contact mode. From the polysaccharide films, it was observed that most of them were flexible and transparent. In the case of the films, mechanical properties were found that the highest value of tensile strength and Young’s modulus corresponded to carboxyl methylcellulose with 69.17 and 1,912.20 MPa values, respectively. Also, Open Photoacoustic Cell method and X-ray diffraction measurements showed that there exist a correlation between the thermal diffusivity values and the crystallinity measured in the biopolymer films. It was also observed that α values of cellulose derived was affected by the substitution group in the molecule, reaching the highest α value, the films of carboxyl methylcellulose. Regarding the microstructural of the films, starch showed the highest roughness value (88.6 nm) whereas hydroxypropyl-methylcellulose resulted with the lowest roughness value (7.67 nm).     

Morphological and Structural Studies of ZnO Nanotube Films Using Thermal Evaporation Technique

Simple thermal evaporation technique has been used to prepare Pb-doped ZnO nanotube films on Si (100) substrate. X-ray photoelectron spectroscopy (XPS) and energy-dispersive X-ray spectroscopy (EDX) characterization have been employed to investigate the element’s contents, which indicates the presence of stoichiometry ZnO nanotube film. The XRD pattern has shown the wurtzite phase of ZnO and polycrystalline structure. Thickness and morphology of the films were explored from the cross sectional of the films and the surface using scanning electron microscopy (SEM) images. SEM images have confirmed the ZnO nanotubes and modifications of the morphology when adding Pb; the recorded images have proved that the diameter of the nanotubes is about 50 nm. However, AFM and SEM images have shown dense structure (without nanotubes) for non-doped ZnO film (Pb = 0 wt.%).

     

2‐(4‐Ethoxy phenyl)‐4‐phenyl quinoline organic phosphor for solution processed blue organic light‐emitting diodes

This paper reports the synthesis and characterization of 2‐(4‐ethoxyphenyl)‐4‐phenyl quinoline (OEt‐DPQ) organic phosphor using an acid‐catalyzed Friedlander reaction and the preparation of blended thin films by molecularly doping OEt‐DPQ in poly(methyl methacrylate) (PMMA) at different wt%. The molecular structure of the synthesized phosphor was confirmed by Fourier transform infra‐red (FTIR) spectroscopy and nuclear magnetic resonance spectra (NMR). Surface morphology and percent composition of the elements were assessed by scanning electron microscopy (SEM) and energy dispersive analysis of X‐rays (EDAX). The thermal stability and melting point of OEt‐DPQ and thin films were probed by thermo‐gravimetric analysis (TGA)/differential thermal analysis (DTA) and were found to be 80°C and 113.6°C, respectively. UV–visible optical absorption spectra of OEt‐DPQ in the solid state and blended films produced absorption bands in the range 260–340 nm, while photoluminescence (PL) spectra of OEt‐DPQ in the solid state and blended thin films demonstrated blue emission that was registered at 432 nm when excited at 363–369 nm. However, solvated OEt‐DPQ in chloroform, tetrahydrofuran or dichloromethane showed a blue shift of 31–43 nm. Optical absorption and emission parameters such as molar extinction coefficient (ε), energy gap (E_g), transmittance (T), reflectance (R), refractive index (n), oscillator energy (E₀) and oscillator strength (f), quantum yield (φ_f), oscillator energy (E₀), dispersion energy (E_d), Commission Internationale de l'Éclairage (CIE) co‐ordinates and energy yield fluorescence (E_F) were calculated to assess the phosphor's suitability as a blue emissive material for opto‐electronic applications such as organic light‐emitting diodes (OLEDs), flexible displays and solid‐state lighting technology.     

Study on the Effect of Poly(Styrene 4-Sulfonic Acid-co-Maleic Acid) Toward Metallization and Plasmonic Tuning of Silver Nanoparticle Thin Films

Thin films with tunable optical properties from yellow to metallic were prepared from a monolayer coating of silver nanoparticles (AgNP) onto a polyelectrolyte multilayer (PEM) thin film. The AgNP were synthesized using various concentrations of stabilizing polyelectrolytes leading to a competitive adsorption concept in which AgNP compete with excess polyelectrolytes to coat the cationic PEM top layer. The AgNP were synthesized by chemical reduction of Ag salts using poly(styrene 4-sulfonic acid-co-maleic acid) (PSS-co-MA) as stabilizing agent to produce nanoparticles coated with both a strong acid (sulfonic) and a weak acid (carboxylic) moiety. Although all the nanoparticle solutions displayed a characteristic bright yellow due to the localized surface plasmon band around 420 nm, the monolayer films of nanoparticles obtained after dipping displayed striking different optical properties. When using a high PSS-co-MA content in the solution, a pale-yellow film was obtained which color shifted to orange and metallic when the capping concentration was decreased from 0.25 to 0.001 mM. The optical properties of the AgNP film could be further changed by galvanic replacement of the Ag with gold ions to produce a gold monolayer. These results are interesting to produce surface with tunable catalytic properties, tunable optical properties, or to be used as primer for the metallization of polymeric surfaces.

     

Immobilization of Serratia marcescens lipase onto amino-functionalized magnetic nanoparticles for repeated use in enzymatic synthesis of Diltiazem intermediate

Magnetic Fe₃O₄ nanoparticles were prepared by chemical coprecipitation method and subsequently coated with 3-aminopropyltriethoxysilane (APTES) via silanization reaction. The synthesized materials were characterized by transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FTIR). With glutaraldehyde as the coupling agent, the lipase from Serratia marcescens ECU1010 (SmL) was successfully immobilized onto the amino-functionalized magnetic nanoparticles. The results showed that the immobilized protein load could reach as high as 35.2 mg protein g⁻¹ support and the activity recovery was up to 62.0%. The immobilized lipase demonstrated a high enantioselectivity toward (+)-MPGM (with an E-value of 122) and it also displayed the improved thermal stability as compared to the free lipase. When the immobilized lipase was employed to enantioselectively hydrolyze (±)-trans-3-(4-methoxyphenyl)glycidic acid methyl ester [(±)-MPGM] in water/toluene biphasic reaction system for 11 consecutive cycles (totally 105 h), still 59.6% of its initial activity was retained, indicating a high stability in practical operation.     

The effect of citric acid on the structural properties and cytotoxicity of the polyvinyl alcohol/starch films when molding at high temperature

A series of starch/polyvinyl alcohol (PVA) films, denoted SP films, with varying concentrations (5–30 wt%) of citric acid (CA) were solvent cast at 140 °C. The effects of CA on the chemical structure, thermal properties, swelling degree, mechanical properties, crystallinity, and cytotoxicity were investigated. Fourier-transform infrared (FT-IR) spectroscopy showed that an esterification took place between CA and starch (or PVA) during molding at 140 °C. This esterification and the multi-carboxyl structure of CA resulted in a chemical cross-linking of the blended system. Furthermore, the esterification occurred more easily between starch and CA as opposed to between the PVA and CA. The residual-free CA acted as a plasticizer for the starch and PVA. As compared to the hydroxyl groups on glycerol, the carboxyl groups on CA were capable of forming stronger hydrogen bonds between CA and other components, and this cross-linking and strong hydrogen bonding enhanced the thermal stability of the SP films. Consequently, the water absorbance decreased from 33% to 20% as the CA percentage increased from 5 to 30 wt%. When 5 wt% CA was added, the tensile strength of the sample increased from 39 to 48 MPa, but when even more CA was added (from 5 to 30 wt%), the tensile strength decreased from 48 to 42 MPa and the elongation at break increased from 102% to 208%. This was caused by the plasticizing effect of the residual-free CA in the blend. The cell relative growth rates of samples with varying CA concentrations exceeded 80% after 7 days of incubation, and this demonstrated that there was no significant toxicity on the cells’ growth when the CA content was less than 20 wt%.     

Influences of plant spacing on root tensile strength of Schefflera arboricola and soil shear strength

Mechanical root reinforcement depends not only on root biomechanical properties but also on root biomass. Although it is known that plant spacing can affect root growth, it is not clear how it affects root tensile strength. We interpreted a set of field data to study the effects of spacing of Schefflera arboricola on root area ratio (RAR), root tensile strength and their combined effects on soil shear strength (also termed root cohesion). S. arboricola was transplanted into compacted silty sand at a spacing of 0.5 m, 0.8 m and 1.1 m. After 20 months of growth in the field, the root systems were excavated for root tensile testing and post-test trait measurements. Plant spacing affected the growth and tensile strength of roots. More closely spaced plants had higher RAR but lower root tensile strength, especially for roots 0.5–2 mm in diameter. According to the existing root breakage and fibre bundle models used in this study, which calculate root cohesion as the product of RAR and root tensile strength, the effects of plant spacing on root cohesion were minimal for most soil depths apart from 0.4- to 0.5-m depth.