Biodegradable Foams Research Articles

Properties of Cassava Bagasse and Polyvinyl Alcohol Biodegradable Foams

The objectives of this work were to develop biodegradable foam trays based on cassava bagasse (CB) and polyvinyl alcohol (PVA) and to study the effects of these components on the microstructure, physicochemical and mechanical properties of the trays. The trays were produced by baking mixtures of 90–100 % (w/w) of CB and 0–10 % (w/w) of PVA. All of the formulations were able to form well-shaped and homogeneous trays with a good appearance. Incorporation of PVA improved the production yield and reduced the water sorption capacity of the produced materials, mainly at low levels. Moreover, the addition of PVA resulted in an increase in stress and strain at break values. The most positive effects of PVA were obtained when this polymer was used at lower levels (2.5 and 5.0 %).

Study on Preparation of Biodegradable Polyurethane Foam

Biodegradable polyurethane foam (PUF) was prepared by using tung oil and starch as the modifiers, they were mixed with polyether polyol and some other reaction auxiliary agents, and then reacted with toluene diisocyanate (TDI). The structure and thermal stability of products were analyzed based on SEM and TG, and the soil burial method was used to investigate the biodegradability of products. The results indicated that polyurethane foam modified by tung oil and starch has good thermal stability, good mechanical properties and good biodegradability. The degradation rate of PUF modified by 5: 2 of starch/ tung oil was 38% after 120 d.

Cassava Starch-Based Biodegradable Foam Composited with Plant Fibers and Proteins

The development of starch foam trays has attracted an increasing amount of attention. However, starch foam trays exhibit poor physical and mechanical properties, and low water and oil resistance. This research aimed to improve the properties of baked composite cassava starch foam tray (CSF) by adding the leaf sheath of betel nut palm, coconut husk or kraft fibers, sunflower meal protein and gluten protein at concentrations of 0, 5 and 10%. All formulations of the CSF trays formed well-shaped trays. The addition of 10% kraft fiber and 10% gluten protein to the CSF trays exhibited the best properties for maximal flexural strength (4.8 MPa) and compressive strength (1.74 MPa). The water and oil absorptions of the trays were reduced by 43% and 72%, respectively. Moreover, composite CSF trays blended with 10% kraft fiber and 10% gluten protein were used as packaging for minimally processed durian (MPD) and kept at 4°C for 5 days. Results showed that compressive strength of the composite CSF slightly decreased from 1.74 to 1.51 MPa, while water and oil absorptions did not change during storage of MPD.

Characterization and mechanical properties of foamed poly(ɛ-caprolactone) and Mater-Bi blends using CO2 as blowing agent

Biodegradable foams are a key area of growth for packaging applications. Starch-based materials have been a successful environmentally degradable polymer. However, making foams out of these materials has been challenging due to their chemical composition and consequent low miscibility in CO2. We examine the potential for developing biodegradable foams with one component being a starch-based polymer by introducing it into polycaprolactone. Polycaprolactone has thus far shown very high-expansion ratios for foams with supercritical CO2. Blends with increasing amounts of starch-based materials were processed and foamed using isothermal treatments with supercritical CO2. Characterization of the samples was done using X-ray diffraction, differential scanning calorimetry, and scanning electron microscopy. The melting enthalpies and temperatures of the starch-based materials phase decreased with decreasing starch-based materials indicating some an influence of polycaprolactone on the starch-based materials crystallinity. Foaming, however, caused a reversal in this effect with the foamed melting points similar to the pure components. Micrographs of the samples from the scanning electron microscopy revealed that the cell size of the foams reduced with the increase in starch-based materials concentration. Mechanical tests—tensile, compression, shear, and impact—were performed on the foamed samples. The results indicate a valuable approach to foaming materials that are compostable but not CO2 miscible through blending with a highly foamable polymer such as polycaprolactone.

Preparation of biodegradable foam from walnut shells treated by subcritical water

BACKGROUND Subcritical water treatment is considered an environment-friendly method to liquefy biomass to prepare valuable chemicals. Several researchers have studied the solid obtained after autohydrolysis treatment for use as reinforcement in biocomposities and was the base pulp and paper technologies. The novelty of this present research is the use of solid in the manufacture of starch foams. RESULTS Subcritical water was used to extract hemicellulosic carbohydrate from walnut shells at temperatures from 160 to 260 °C for 15 min and at 200 °C for various treatment times. The maximum yield was obtained at 200 °C for 15 min. The residue of the walnut shells obtained at the maximum carbohydrates extraction yield was used to prepare a biodegradable foam by compounding with corn starch using a technique similar to compression molding. It was found that replacing 20% of the corn starch by the residue had no deleterious effects on the density and morphology, as indicated by scanning electron microscopy. The prepared foams had a dense outer skin and a less dense interior with large, mostly open cells. The flexural strains were similar to that of foamed polystyrene and the flexural modulus and flexural stresses were larger. CONCLUSION It was considered that the prepared biodegradable foam was a promising material to take the place of plastic products in the future. © 2014 Society of Chemical Industry

Validation of a Mathematical Model for the Description of Hydrophilic and Hydrophobic Drug Delivery from Biodegradable Foams: Experimental and Comparison Using Indomethacin as Released Drug

In drug delivery systems, mathematical modeling plays an important role in elucidating the release mechanisms, the potential applications of a determinate system matrix–drug, or the design of new delivery systems. In this work, we have modeled porous biodegradable foams based on polylactide (PLA) and poly(lactide-co-glycolide) (PLGA) impregnated with a hydrophobic drug (indomethacin) through a single-step process using supercritical CO2 as foaming agent. The modeling of indomethacin in vitro release was based on a previous model developed to describe accurately the process of release of a hydrophilic drug and consisting of three simpler and more comprehensible stages: external and internal mass transfer as well polymer degradation. It has been modified considering the low aqueous solubility of indomethacin and the variations in the mechanism produced, consequently improving its physical signification. Finally, the solubility of different drugs impregnated and their response in the release profiles were evaluated.

Use of malt bagasse to produce biodegradable baked foams made from cassava starch

Malt bagasse, a byproduct of the brewing industry, was used to produce biodegradable foam trays made from cassava starch using a baking process. These foams were prepared with different concentrations of malt bagasse (0–20%, w/w) and then were characterized according to their microstructure, physical and mechanical properties. The trays produced with 5 and 10% (w/w) malt bagasse had the highest production yields (100%), the trays thicknesses ranged from 2.16 to 2.24mm and densities ranged from 0.415 to 0.450g/cm3. There was a good distribution of the malt bagasse throughout the polymeric matrix, which had an amorphous structure. The variation in the relative humidity (RH) from 33 to 58% did not affect the mechanical properties of the produced foams, but the stress at break decreased and the strain at break increased when the trays were stored at 90% RH. As demonstrated by the sorption isotherm data, the incorporation of malt bagasse at 10% w/w resulted in a decrease in the hygroscopicity of starch foams. The addition of bagasse at concentrations up to 15% w/w decreased the initial water adsorption rate of the trays. The produced trays can be a viable alternative for packing dry foods, reducing the use of petroleum based materials.

Cellulose Nanofibril (CNF) Reinforced Starch Insulating Foams

ABSTRACTIn this study, biodegradable foams were produced using cellulose nanofibrils (CNFs) and starch (S). The availability of high volumes of CNFs at lower costs is rapidly progressing with advances in pilot-scale and commercial facilities. The foams were produced using a freeze-drying process with CNF/S water suspensions ranging from 1 to 7.5 wt. % solids content. Microscopic evaluation showed that the foams have a microcellular structure and that the foam walls are covered with CNF`s. The CNF's had diameters ranging from 30 nm to 100 nm. Pore sizes within the foam walls ranged from 20 nm to 100 nm. The materials` densities ranging from 0.012 to 0.082 g/cm3 with corresponding porosities between 93.46% and 99.10%. Thermal conductivity ranged from 0.041 to 0.054 W/m-K. The mechanical performance of the foams produced from the starch control was extremely low and the material was very friable. The addition of CNF's to starch was required to produce foams, which exhibited structural integrity. The mechanical properties of materials were positively correlated with solids content and CNF/S ratios. The mechanical and thermal properties for the foams produced in this study appear promising for applications such as insulation and packaging.

Solid-state foaming of biodegradable polyesters by means of supercritical CO2/ethyl lactate mixtures: Towards designing advanced materials by means of sustainable processes

In this work, a clean and sustainable approach for the design and manufacture of biodegradable foams with controlled pore structures is reported. Porous polycaprolactone (PCL), polylactic acid (PLA) and poly(L-lactide/caprolactone) (PLC) homo- and co-polymers have been prepared by a supercritical solid-state foaming technique. The process has been carried out at low temperature, in the range of 35–40°C, and at the pressure of 20MPa. Supercritical CO2 (scCO2), pure or with a 0.2% molar fraction of ethyl lactate (EL), has been selected as the blowing agent. Foaming has been induced by a pressure quench approach and by using either a low (0.5min) or a high (6min) depressurization time. Results showed that blowing agent uptake and foaming was strongly affected by the thermal properties and crystalline structure of the polymers. Furthermore, adding a small amount of EL to scCO2 decreased the plasticization temperature of the polymeric materials, finally improving foams uniformity and polymer foaming. Hence, homogeneous foams could be manufactured avoiding the use of toxic chemicals and at a temperature as low as 35°C for PLA and PLC, and as low as 40°C for the more crystalline PCL.

Effect of Lidocaine-soaked Nasal Packing on Pain Relief after Endoscopic Sinus Surgery

Nasal packing is usually performed to control bleeding after endoscopic sinus surgery (ESS). Although new packing materials have been developed, they still cause pain. This study was designed to evaluate the effect of lidocaine-soaked packs on pain after ESS. A prospective, randomized, double-blind controlled trial was conducted in 63 patients with CRS undergoing ESS. At the conclusion of the operation, 2% lidocaine-soaked biodegradable synthetic polyurethane foam and saline-soaked polyurethane foam were inserted in both nasal cavities of 31 patients and 32 control patients, respectively. The same lidocaine or saline was reapplied into the nasal packs at postoperative 8 hours. Pain was evaluated using a visual analog scale at postoperative 1, 4, 8, 16, 20, and 24 hour(s). The number of gauze that cleaned the blood around the nose was counted. Heart rate, rhythm, and blood pressures were checked preoperatively and postoperatively to evaluate the influence of lidocaine on vital signs. Postoperative pain decreased in lidocaine group at all of the postoperative time periods (p < 0.05). Lidocaine reduced postoperative bleeding at postoperative 8 and 24 hours. Changes of blood pressure from preoperative values in the lidocaine group were not different from those in the control group (p > 0.05). Heart rate in the lidocaine group was more stable than that in the control group (p < 0.05). Lidocaine-soaked packs significantly reduced postoperative pain without serious changes on vital sign. These findings suggest that topical lidocaine application to nasal packs could be a useful method to reduce pain during the early postoperative period after ESS.

A clean and sustainable route towards the design and fabrication of biodegradable foams by means of supercritical CO2/ethyl lactate solid-state foaming

Polymeric foams are essential elements of our life as they are widely used for applications requiring light-weight materials coupled with good mechanical properties and controlled energy and mass transfer. However, foams are often made of petroleum-derivate non degradable materials and manufactured by means of toxic and often hazardous blowing agents. In this work, a clean and sustainable approach to design and fabricate porous biodegradable poly(e-caprolactone) (PCL) materials via solid-state foaming is investigated. The foaming process was performed by using supercritical mixtures of carbon dioxide (CO2) and ethyl lactate (EL) as non-toxic and environmentally friendly blowing agents. Operating temperatures, in the range of 35–40 °C, a small amount of EL (up to 0.2%) and either one or two step depressurization profiles were used to control PCL foaming. The results of this study demonstrate that supercritical CO2/EL binary mixtures are promising safer and sustainable blowing agents to design and fabricate renewable PCL foams at relatively low temperatures and with density as low as 0.2 g cm−3, mean pore size in the 14–530 μm range and pore density from 3.9 × 104 to 1.4 x 108 pore cm−3.

Nanoreinforced xylan–cellulose composite foams by freeze-casting

Structured biofoams have been prepared from the readily available renewable biopolymer xylan by employing an ice-templating technique, where the pore morphology of the material can be controlled by the solidification conditions and the molecular structure of the polysaccharide. Furthermore, reinforcement of these biodegradable foams using cellulose nanocrystals shows potential for strongly improved mechanical properties.

Preparation and Characterization of Biodegradable Polylactic Acid/Gelatinized Cornstarch Foams

Biodegradable foams derived from poly(lactic acid) (PLA) and gelatinized cornstarch (GS) were prepared by twin-screw extrusion using Azodicarbonamide(AC) as blowing agent and talc as nucleation agent. Foams with a relatively fine and uniform cell morphology and better foam properties were obtained under optimized conditions of PLA/GS ratio at 3:1, 1.5% AC content, and MAH and glycerol blend system.

Mechanical and physical properties of expanded starch, reinforced by natural fibres

Biodegradable foams made from potato starch and natural fibres were obtained by extrusion. The effects of varying origins of these fibres on foam properties were studied, as well the relationships between their properties and the foam microstructure. The addition of fibres increased the expansion index and led to a significant reduction in water adsorption of starch foams, generally improving foam properties. The mechanical properties of the foams were affected by both relative humidity (RH) of storage and foam formulation. In general, as the RH increased, the foam strength decreased. The formulation presenting the best mechanical properties contained 10wt% hemp fibre and had a maximal resistance of 4.14MPa and a modulus of 228MPa, corresponding to a more compact and dense microstructure.

Biodegradable foams based on starch, polyvinyl alcohol, chitosan and sugarcane fibers obtained by extrusion

Biodegradable foams made from cassava starch, polyvinyl alcohol (PVA), sugarcane bagasse fibers and chitosan were obtained by extrusion. The composites were prepared with formulations determined by a constrained ternary mixtures experimental design, using as variables: (X1) starch / PVA (100 - 70%), (X2) chitosan (0 - 2%) and (X3) fibers from sugar cane (0 - 28%). The effects of varying proportions of these three components on foam properties were studied, as well the relationship between their properties and foam microstructure. The addition of starch/PVA in high proportions increased the expansion index and mechanical resistance of studied foams. Fibers addition improved the expansion and mechanical properties of the foams. There was a trend of red and yellow colors when the composites were produced with the highest proportions of fibers and chitosan, respectively. All the formulations were resistant to moisture content increase until 75% relative humidity of storage.

Biodegradable foam tray from cassava starch blended with natural fiber and chitosan

This work developed biodegradable foam trays from cassava starch blended with the natural polymers of fiber and chitosan. The kraft fiber at 0, 10, 20, 30 and 40% (w/w of starch) was mixed with cassava starch solution. Chitosan solution at 0, 2, 4 and 6% (w/v) was added into starch/fiber batter with 1:1. Hot mold baking was used to develop the cassava starch-based foam by using an oven machine with controlled temperature at 250°C for 5min. Results showed that foam produced from cassava starch with 30% kraft fiber and 4% chitosan had properties similar to polystyrene foam. Color as L*, a* and b* value of starch foam tray was slightly increased. Density, tensile strength and elongation of the starch-based foam were 0.14g/cm3, 944.40kPa and 2.43%, respectively, but water absorption index (WAI) and water solubility index (WSI) were greater than the polystyrene foam.

Preparation and Properties of Biodegradable Foams

Foam extrusion of biodegradable polyester [poly(butylene adipate-co-terephthalate) (PBAT)] and its blends with maleated thermoplastic starch (MTPS) using a chemical blowing agent was performed. The effect of MTPS and percentage of chemical blowing agent on various foam properties is discussed. In general, an increased amount of PBAT in the foams improves the properties of the foams. The foam samples were characterized by measurements of density, expansion ratio, specific length, compressive strength, resiliency, moisture sorption, and imaging using digital light microscopy. Density, expansion ratio, and specific length measurements show that the best characteristics of lowest density, highest expansion ratio, and highest specific length are exhibited by the PBAT samples. The compressive strength and foam density exhibit a power-law relationship. Greater amounts of PBAT in the samples increase the resiliency and decrease the steady state weight gain during moisture sorption. All samples show regions of unfoamed material when only 3% chemical blowing agent is used, but when 5 and 7% chemical blowing agent is used, the samples exhibit cells throughout the matrix.

Development of a biodegradable foam for use in negative pressure wound therapy

Treatment of wounds using negative pressure wound therapy (NPWT) uses a nondegradable polyvinyl alcohol (PVA) foam in the application of negative pressures typically for 1-3 days. The purpose of this study was to construct and test biodegradable poly(ε-caprolactone) (PCL) foam as a substitute for the PVA foam. Such a foam would be left within the wound until healing was achieved and form a biodegradable matrix into which tissue would grow. The use of such foam would obviate the need for any serial foam changes and a final foam removal, thus making patient care much easier and more economical. PCL foams were prepared by salt leaching and phase separation. Morphological and mechanical properties of the foams were characterized and compared to PVA foam. PCL and PVA foams were tested on the uncut surface of a pig liver maintained in a hydration chamber continuously replenished with saline under the conditions of negative pressure of 50 mm Hg for 72 h. The results demonstrated that PCL foam made from phase separation had the similar properties and function as the PVA foam. The results demonstrate that PCL foam is an appropriate substitute for currently used nondegradable PVA foam in NPWT applications.

Synthetic Aliphatic Biodegradable Poly(Butylene Succinate)/MWNT Nanocomposite Foams and Their Physical Characteristics

Synthetic aliphatic biodegradable poly(butylene succinate) (PBS) nanocomposites with multiwalled carbon nanotube (MWNT) were investigated to study the effects of the preparation method and MWNTs on physical characteristics of biodegradable polymer nanocomposite foams. PBS nanocomposites were prepared by the solution blending and melt mixing methods. Nanocomposites of PBS/MWNT were also prepared by the SOAM method, where the solution-blended nanocomposites were further mixed in the melt state. The dispersion of MWNTs in the PBS matrix was characterized by FT-Raman spectroscopy, field-emission scanning electron microscopy (FE-SEM), and field-emission transmission electron microscopy (FE-TEM). The mechanical and thermal properties of the PBS nanocomposites were measured using a universal test machine (UTM), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). Nanocomposite foams with high-density closed cells were prepared by using a chemical blowing agent (CBA) that acted as a cell-nucleating agent. The effects of the foaming conditions and MWNTs on the blowing ratio, cell size distribution, and morphology of the expanded PBS foams were investigated. The effect of the CBA content on the blowing ratio, cell size distribution, and morphology was also investigated.

Analysis and Study on the Components of Starch and Wood Fiber Biodegradable Foam

Experiment design is to find the main influence factors through analysis of initial experiment data, which is an important foundation to further experiment .This paper studies a kind of biodegradable foam packaging material. It is composed of starch and plant fiber and PVA as raw materials by molding. Using of uniform experimental design method obtains the experimental program. And applying SAS software, selecting stepwise linear regression method analyzes on the experiment results. Analysis results indicate that the contents of starch, fiber and PVA have significant influence to material tensile strength and establish the regression model. This research lays the foundation and provides the theories basis for further studies.