Scientists from the Technology and design of multicomponent products group of the University of Seville (US), together with experts from the University of Huelva, have obtained a natural bioplastic from soy protein that can absorb up to forty times its weight.
This new ecological and biodegradable product is environmentally friendly. Experts are therefore exploring its application in the field of horticulture, specifically as a raw material from which to manufacture agricultural nutrient dispensers. To arrive at the design of the material, which they report in an article published in the journal Polymer Testing, the researchers have carried out different experiments in the laboratory by altering the composition of this legume. Specifically, they modified its affinity for water and made it retain a higher percentage of water.
“The soybean itself has a high absorption capacity, which makes it an ideal material, but we wondered whether it would fit into the category of superabsorbent bioplastics, which are those that have to absorb between 10 and 1,000 times their actual weight in water. After introducing some variants, the result obtained was positive,” says US researcher Antonio Guerrero, head of the study.
During the tests, the experts found that depending on the processing variables and the combination of the mixture, the absorption properties of soybeans are altered. “Without interfering with its composition, this legume is capable of absorbing twelve times its weight, while if we modify its molecular structure to increase its affinity for water, this capacity is multiplied by three to reach 36 times its initial weight, that is, an increase of 3,600% over its real weight,” Guerrero specifies.
To carry out the experiments, they first processed the soybeans to extract the protein. In order to separate the liquid part from the solid compounds, the scientists used the freeze-drying technique. “This method is gentler and less aggressive than atomization, so it practically does not affect the protein. This way we manage to isolate the raw material with which we are going to work,” the researcher explains.
After this dehydration process, the experts mixed the already modified protein isolate with a plasticizer. “We obtain a solid protein concentrate and once this composition is prepared, we introduce it into an injection machine and deposit it in a mold. From there we obtain the test tube with which we are going to carry out the tests,” explains the scientist.
Ecological nutrient distributors
In addition to having a higher absorption capacity than other conventional bioplastics, the researchers have advanced that this compound potentially has qualities for use in horticulture, specifically as devices for distributing agricultural nutrients. In fact, the next phase of this project is to study the feasibility of releasing these compounds in the field through natural dispensers formed from superabsorbent soybeans.
To do this, they will simulate a soil in the laboratory and place the matrices loaded with micronutrients such as mineral salts, iron and zinc, to which they will add water. In this way, they will check whether, after the drainage phase and as a result of the action of these dosing devices, the water contains nutrients and in what quantity it does.
“We want to make sure that there is a controlled supply that is adjusted to the needs of the soil. In addition, as it is a biodegradable plastic made from soy proteins, the containers themselves, once empty, would serve as a substrate for the soil,” Guerrero says. Following this line of study, the researchers will continue experimenting with other products such as rapeseed or cotton from which superabsorbent materials can be obtained with applications in the sanitary hygiene industry and agriculture. This applied research project is financed by the Ministry of Economy, Industry and Competitiveness, in addition to FEDER funds.
