Article featured on the cover of ACS Applied Nano Materials presents findings on effectiveness and sustainability when nanocellulose and latex are combined
Replacing petroleum-based adhesives represents a challenge for global industry, which is looking for alternative materials and processes with less environmental impact
Researchers at CNPEM have just published an article in the journal ACS Applied Nano Materials describing findings that pave the way toward developing a simpler method to control the physical and chemical properties of a combination of renewable materials to produce more water-resistant adhesives with desirable mechanical properties.
Understanding these interactions at the nano scale is essential to optimize processes and develop alternative products with similar or even better properties than adhesives used in various applications.
The study
Electrostatic interaction between compounds with opposite electrical charges is very important to understand why some materials have such special adhesive and cohesive properties.
For this reason, the research team evaluated the properties of cationic cellulose nanofibrils (CCNF), tiny filaments with a positive electrical surface charge which are obtained from sugarcane waste, combined with natural latex rubber, which has a negative charge.
These materials are cheap and abundant in nature and also offer advantages such as low toxicity, biodegradability, high capacity for surface modification, strength, and exceptional mechanical properties.
The research used sophisticated resources from the microscopy facilities at the Brazilian Nanotechnology National Laboratory (LNNano/CNPEM) such as cryomicroscopy and atomic force microscopy (AFM) to investigate the interactions between the surfaces of these materials in detail in order to synthesize an adhesive with a low solids content that can stick to various materials in wet as well as dry settings.
“With the help of AFM and cryomicroscopy, we were able to observe that during the complexation of the materials, the latex (which is a spherical particle) was coated by the nanofibers, and when in contact with water it was responsible for the anchoring property that preserved the mechanical properties. Meanwhile, the nanofibers on the outer surface ensured the adhesive effect,” explains Daiane Batista da Silva, one of the authors of the article.
Results and advantages
Tensile tests were run on some of the most common products used to manufacture packaging, like paper, aluminum (Al), and polypropylene (PP) as substrates.
“The adhesive produced very strong bonds with strength similar to the materials used in this segment of the industry,” said Silva.
Images from cryogenic electron microscopy of the adhesive made from cationic cellulose nanofibrils covering the natural rubber latex particles
“One of the greatest challenges in the industry is package recycling. The amount of additives added to them complicate this process. In paper packaging, the fiber can be pulped and reused, but the presence of some fossil-based polymers impedes this process. In this study, since biopolymers were used, the fiber could be easily reprocessed. Also, for packaging made of other materials, our adhesive can easily be removed via wet cleaning,” explains Juliana Bernardes, who coordinated the study.
Next steps
The CNPEM researchers are very optimistic about the possibilities for controlling the properties that can be obtained with the resulting knowledge on combining these materials. The formula has been perfected through testing with other types of substrates.
“We used latex particles, which are relatively large. In the next phase of research, we intend to use molecules to improve water resistance. By bringing the anchoring points from the nano scale to the molecular, with greater penetration in the fibers, we hope to obtain a compound with even better adhesion properties,” says Bernardes.
Support and patent
Daiane Batista da Silva’s work was recognized with the CRQ-IV 2022 prize from the São Paulo Regional Chemistry Council in the Upper-Level Chemistry category, and received support from the São Paulo Research Foundation (FAPESP). The process to obtain the adhesive also led to a patent.
About CNPEM
A sophisticated and effervescent environment for research and development, unique in Brazil and present in few scientific centers in the world, the Brazilian Center for Research in Energy and Materials (CNPEM) is a private non-profit organization, under the supervision of the Ministry of Science, Technology and Innovation (MCTI). The Center operates four National Laboratories and is the birthplace of the most complex project in Brazilian science – Sirius – one of the most advanced synchrotron light sources in the world. CNPEM brings together highly specialized multi-thematic teams, globally competitive laboratory infrastructures open to the scientific community, strategic lines of investigation, innovative projects in partnership with the productive sector and training of researchers and students. The Center is an environment driven by the search for solutions with impact in the areas of Health, Energy and Renewable Materials, Agro-environment, and Quantum Technologies. As of 2022, with the support of the Ministry of Education (MEC), CNPEM expanded its activities with the opening of the Ilum School of Science. The interdisciplinary higher course in Science, Technology and Innovation adopts innovative proposals with the aim of offering excellent, free, full-time training with immersion in the CNPEM research environment. Through the CNPEM 360 Platform, it is possible to explore, in a virtual and immersive way, the main environments and activities of the Center, visit: https://pages.cnpem.br/cnpem360/.
