Japan has monopolized a bio-polycarbonate produced by scientists from the Korea Research Institute of Chemical Technology (KRICT). The study paves the way for the possible commercialization of the bio-polycarbonate.
Bio-polycarbonate is an environment-friendly bioplastic. This material could be a substitute for traditional polycarbonate, which consists of bisphenol A (BPA), an environmental hormone-causing substance. So far, Mitsubishi Chemical Corp., a Japanese company, is the only one to successfully commercialize the production of bio-polycarbonate.
Using the plant-based components of nanocellulose and isosorbide, Dr Jeyoung Park, Dr Dongyeop Oh, and Dr Sung Yeon Hwang from the Research Center for Bio-based Chemistry of KRICT produced the bio-polycarbonate.
BPA is a petrochemical substance as well as an environmental hormone that can cause metabolic complications and interferences in the endocrine systems. BPA is largely used in polycarbonate, but in Korea, its use in cosmetics and milk bottles has been banned. It has also been used in the coating materials of canned foods and receipt papers.
Although this makes bio-polycarbonate an attractive alternative to polycarbonate-containing BPA, it is not easy to simultaneously satisfy economic possibility and high mechanical performance of general plant-ingredient plastics. KRICT managed to overcome this by using a combination of nanocellulose and isosorbide, and was successful in producing bio-polycarbonate that outperforms the petroleum polycarbonate.
Isosorbide is an environment-friendly compound obtained from glucose and can improve the mechanical properties of the integrated polymer. It also has good optical and UV-resistive properties owing to its unique molecular structure.
Scientists applied the “like dissolves like” principle in which analogous compounds combine well. Isosorbide combined well with nanocellulose as a bio-derived reinforcing agent, as both substances are hydrophilic and have a similar structure. Later, the nanocomposite plastic was polymerized. Hence, the effectively dispersed nanocellulose that served as a metal rebar in the concrete increased the strength of the bioplastic.
We wanted to break the stereotype that bio-plastic has inferior mechanical properties and is expensive. Through the synergistic interplay between the plant-based ingredients, we were able to develop a bio-plastic that is superior to petroleum plastic.
Dr Jeyoung Park, Research Center for Bio-based Chemistry, Korea Research Institute of Chemical Technology
Thus, it greatly enhanced the physical properties of the bioplastic, like transparency and strength, which have been found to be the restrictions of common bioplastics.
The prepared bio-polycarbonate has a tensile strength (how sturdy a material is) of 93 MPa, which is the maximum measurement so far among all current bio-polycarbonates and petroleum polycarbonates. The tensile strength of petroleum polycarbonate lies between 55 and 75 MPa, whereas the tensile strength of the bio-polycarbonate produced by Mitsubishi Chemical Corp. lies between 64 and 79 MPa.
The light transmittance that characterizes the transparency of the plastic was found to be 93% because of the suppressed crystallinity through the dispersed nanocellulose. Hence, it is highly superior to commercially available petroleum polycarbonate.
The reason for this striking performance is that almost all nanocomposites have a lower transparency because of the scattering of light by nonuniform aggregates. Furthermore, there is no possibility of discoloration even after long UV exposure because of the absence of benzene ring in bio-polycarbonate, in contrast to petroleum polycarbonate.
Hence, bio-polycarbonate finds application in industries manufacturing headlights, automobile sunroofs, transparent highway noise barriers, and exteriors of electronics like smartphones. It is anticipated that such material could be a possible substitute for the current polycarbonate.
Moreover, using a rat model, the low toxicity of the material was confirmed by animal in vivo inflammatory testing, which promotes the ability of the material for biomedical uses. The incorporation of the polymer into the subcutaneous tissue was done to verify the presence of inflammation. A toxicity level of 1, from a range between 0 and 5, was estimated (toxicity is least when the value reaches 0).
A low toxicity result was obtained from the in vivo inflammatory testing using a rat. The toxicity level is safe for infants and children to put in their mouth, which means that the materials can be used for medical purposes in such things as implants and artificial bones, as well as toys, milk bottles, and baby strollers.
Dr Dongyeop Oh, Research Center for Bio-based Chemistry, Korea Research Institute of Chemical Technology
The total sale of petroleum polycarbonate based on the existing production is approximately 5 million tons per year, and the annual production capacity of bio-polycarbonate by Mitsubishi Chemical Corp. is approximately 20,000 tons. Despite the fact that the bio-polycarbonate market is still in its early stage, the transformation to commercialization due to this effort would contribute to the dominance of the bioplastic market in the future.
This successful study titled “Preparation of synergistically reinforced transparent bio-polycarbonate nanocomposites with highly dispersed cellulose nanocrystals” appeared on the front cover of the October issue of Green Chemistry of the Royal Society of Chemistry, the highest authority in the green chemistry field. At the same time, this paper was chosen as a Hot Article of 2019.
Fear of plastics is growing because of the issues like plastic waste and chemophobia, but plastics have become an essential part of everyday life so we will develop bioplastics that people can use without fear.
Dr Hwang Sung Yeon, Director, Research Center for Bio-based Chemistry, Korea Research Institute of Chemical Technology
This study was financially supported by the Biochemical Materials Certification Center establishment project of the Ministry of Trade, Industry and Energy, Korea, and key projects of KRICT.