Ryouichi Kitagawa

An exploratory research of PVC-Chlorella composite material (PCCM) as effective utilization of Chlorella biologically fixing CO2

A new PVC-Chlorella composite material (PCCM) was investigated aiming at the effective utilization of biological CO2 fixing Chlorella. The microalga Chlorella, after fixing CO2, was molded with PVC. Molding conditions of PCCM, and physical properties of Chlorella were studied using tensile strength as an index for estimating the properties of PCCM. The optimum parameters for molding of PCCM were as follows: temperature = 180°C, pressure = 4.4 MPa and time = 5 min. The following physical parameters of Chlorella best enhance high tensile strength: water content of 2%, average particle size of 30–80 μm and a relatively homogeneous distribution of particle size. Chlorella, maintaining its original shape, exists in PCCM as an empty ball inlaid in the matrix of PVC. The PCCM shows a lower elongation and is more brittle than PVC, possibly as a result of gas and residual PVC primary particles around Chlorella grains. A comparison between theoretical and experimental results show that there is an effective combination between the PVC matrix and the Chlorella surface in PCCM. PCCM has a tensile strength higher than 30 MPa which meets the requirements for rigid PVC products, if Chlorella content is less than 20%. Chlorella can thus be effectively utilized as a practical filler.

Synthesis and characterization of a novel blendof polypropylene with Chlorella

A novel blend of polypropylene (PP) with Chlorella, a natural microalga, was synthesized successfully by a melt-mixing method with maleic anhydride-modified polypropylene (MPP) as a compatibilizer. The adhesion of hydrophobic PP to hydrophilic Chlorella is based on the formation of chemical bonds between the maleic anhydride groups of MPP and hydroxy groups of Chlorella through solid-phase esterification. The single maleic anhydride groups have the highest reactivity with Chlorella. From the comparison with PP–Chlorella blends without MPP, the ester bonds between MPP and Chlorella cause a decrease in crystallinity of the MPP matrix which is a primary origin of the decrease in melting and solidification enthalpies of the MPP–Chlorella blend, and induce intensive expansion of the MPP matrix around the Chlorella particles which decreases the glass transition temperature. Consequently, the PP–Chlorella blend with MPP exhibits a marked increase in tensile strength and Youngs modulus compared with the blend without MPP because of the stronger interactions between MPP and Chlorella than those between Chlorella cells.

A novel polyethylene-chlorella composite. I. Characterization of chlorella biologically fixing CO2

Chlorella, a microalga massively produced from biological fixation of CO 2 , was investigated to evaluate the possibility of processing it with polyethylene. Chlorella grain, a hollow aggregate sphere constituted of chlorella cells binding with each other by hydrogen bonds, exhibits a higher thermal stability than cellulose and strong resistance to cracking under mechanical forces up to 150 MPa, possibly due to the spherical structure and unique manner of assembly of chlorella cells. These characteristics of chlorella strongly indicate that it can resist deformation and thermal decomposition in a compounding process with polyethylene.

New application of cellulose and chitosan for biodegradable polymer material

We found that a combination of fine cellulose and chitosan was suitable for forming biodegradable films and moldings. The composite film demonstrated high strength and had a maximum wet strength at 10-20% chitosan content. Besides the major hydrogen bonding between chitosan and cellulose, the amino groups in chitosan and the trace amounts of carbonyl groups in cellulose played an important role in the formation of the composite. This film was completely decomposed by microorganisms in soil or sea water. The biodegradability was controlled by adjusting the temperature in heat treatment, the quantity of carbonyl group in the cellulose, etc. We have also been working on joint research with companies to produce films, nonwoven fabrics and foams. Foams and nonwoven fabrics of the composite were found to be effective in healing of skin defects of rats. We are also trying to produce fine cellulose material for the biodegradable plastic by simple and convenient method grinding together with an organic solvent. The production of chitosan by cultivation of a fungus such as Rhizopus acetoinus is also discussed.