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Improved FDM 3D Printing with Lignin Biocomposites

In the recently published ‘Lignin: A Biopolymer from Forestry Biomass for Biocomposites and 3D Printing,’ international researchers Mihaela Tanase-Opedal, Eduardo Espinosa, Alejandro Rodríguez, and Gary Chinga-Carrasco explore a very specific area of materials related to biopolymers.

As composites are used more often these days to improve existing materials—especially in 3D printing—alternative materials like wood are being experimented with also. Fiber-based biocomposites and lignin can be better options than petrochemical-based products. For this study, the authors gleaned lignin from spruce trees being reduced to pulp. They used the material to create composite filaments, printing sample dogbones to test mechanical properties.

Natural-fiber biocomposites offer the following:

  • Affordability
  • Good mechanical properties
  • No emission of toxins
  • Light weight

PLA is a popular polymer used in 3D printing, and as the authors remind us, it is actually a biopolymer—featuring good mechanical properties, biodegradability, easy melt-processability, and much more; however, it is also not always cost-effective or suitable for every project. As a composite, however, PLA becomes more versatile.

“Each year, over 50 million tons of lignin are produced worldwide as a side product from biorefineries, of which 98% are burned to generate energy. Only 2% of the lignin has been used for other purposes, mainly in applications such as dispersants, adhesives, and fillers,” state the researchers.

“Without modification, lignin can be directly incorporated into a polymeric matrix, such as UV-light stabilizer, antioxidant, flame retardant, plasticizer, and flow enhancer to reduce production cost, reduce plastic, and potentially improve material properties.”

As 3D printing brings so many advantages forth to industrial users, with the ability to create affordable and complex structures, as well as leaving behind less waste and energy usage, materials like lignin are attractive for use when mixed with other polymers. For this study, the researchers focused on PLA/soda lignin biocomposite filament for 3D printing.

“A motivation for selecting soda lignin is that it is sulphur-free. Soda lignin was thus expected to reduce the typical smell that is experienced when melt-processing biocompounds containing kraft lignin or lignosulfonates,” stated the researchers.

Samples were assessed for:

  • Mechanical (tensile testing)
  • Thermal (TGA, DSC analysis)
  • Morphological (SEM)
  • X-ray diffraction
  • Antioxidant properties

An original Prusa i3 MK3S was used in FDM 3D printing of the dogbone samples, with a length of 63mm and width of 3mm. Three sets were printed, as well as a phone case. The biocomposite demonstrated an increase in mechanical properties when temperatures were increased, with elastic modulus decreasing by 25% to 32%. Lignin offered an improvement in ductility, but a decrease in plasticity.

Mechanical properties of PLA and PLA/Lignin biocomposites.

 

Stress−strain curves for the different biocomposites

Antioxidant properties were also confirmed, showing that 3D printed samples with lignin had even more antioxidant capability than PLA, meaning there is the potential for use for other applications such as food packaging.

“The suitability of the PLA/lignin biocomposite filament for 3D printing was also tested, by printing a smartphone protective case,” stated the researchers. “The printing process revealed a good performance of the lignin-containing filament, and a functional protective case was effectively 3D printed. PLA/Lignin filaments are a plausible option for lignin utilization with potential in, e.g., rapid prototyping and consumer products. It is worth to mention that the typical smell from some lignins was not detected during the extrusion of the filaments or during the printing process, which is an additional advantage of using soda lignin in PLA biomaterials.

“Biocomposites exhibited good extrudability and flowability with no observable agglomeration of the lignin. This suggests that lignin-containing biocomposites are plausible alternatives for 3D printing applications.”

3D printing of a smartphone protective case with PLA/lignin biocomposite filament

The use of composites today is a growing trend due to the ability to improve prototypes and parts, from glass composites to copper metal to particle reinforced nanocomposites. What do you think of this news? Let us know your thoughts! Join the discussion of this and other 3D printing topics at 3DPrintBoard.com.

[Source / Images – ‘Lignin: A Biopolymer from Forestry Biomass for Biocomposites and 3D Printing’]

 

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Russian Researchers Develop Biocompatible 3D Polymeric Materials for Tissue Repair

Many researchers and scientists have turned to 3D printing for applications in tissue engineering, and a team from the Polymer Materials for Tissue Engineering and Transplantology Laboratory of Peter the Great St. Petersburg Polytechnic University (SPbPU) is no different. In a joint project with researchers from the Russian Academy of Sciences and Pavlov First St. Petersburg State Medical University, the SPbPU team has developed innovative, polymeric medical materials that can be used to fix human organs that have undergone trauma.

The project is taking place under Project 5-100, a state support program for Russian universities that’s been going on since 2013. The goal of the project is to elevate the standing of Russian higher education institutes, so that they can move forward and strengthen their research and education initiatives by promoting R&D, streamlining administration, growing international cooperation, and providing incentives to attract top professors and facilitate existing faculty’s professional growth.

For its part of Project 5-100, SPbPU invents, applies, and shares its cross-disciplinary polytechnic knowledge and advanced manufacturing technologies. In this instance, scientists at the university have created a porous, 3D material made of chitosan – a bone tissue analog – and collagen, which is the most promising material for fabricating tissue scaffolds. The new material can then be used to help restore lost parts of bone. The materials in this new medical area are referred to as mimicking materials, because they can actually trick the human body…but not in a bad way.

“We are not deceiving nature, we are just helping it to cope with a medical problem,” explained Vladimir Yudin, the Head of the Polymer Materials for Tissue Engineering and Transplantology Laboratory. “Experts are currently debating whether it is better to use an implant or restore an organ. A person with an artificial organ must take medication for the rest of their lifetime to prevent the body from rejecting it. This is not the case for tissue grown from human cells.”


Preclinical study results show that after a certain length of time, a 3D sponge embedded in human bone will begin to be covered in natural bone tissue as the artificial material decomposes. The researchers also studied the 3D collagen sponge in both muscle and liver tissue and found that the material can stimulate natural organ tissues to be restored.

The team published a paper on their research, titled “Bioresorption of Porous 3D Matrices Based on Collagen in Liver and Muscular Tissue,” in the Cell and Tissue Biology journal; co-authors include P. V. Popryadukhin, G. Y. Yukina, I. P. Dobrovolskaya, E. M. Ivankova, and Yudin.

The abstract reads, “Highly porous cylinder-shaped 3D matrices with diameters of 1.3 and 3 mm were obtained by lyophilization of collagen solution. A study in vivo of the mechanism and rate of resorption of the resulting material showed that complete resorption of the matrix occurred 6 weeks after their implantation into liver tissue and 3 weeks after implantation into muscle tissue of animals. Surrounding tissues were not altered or damaged. Histological analysis revealed that, simultaneously with the resorption of matrix collagen, connective tissue and blood vessels were formed. This allows us to recommend the developed porous material based on collagen for use as matrices for tissue engineering and cellular transplantation.”

In the case of these mimicking materials, a polymer matrix is first implanted into damaged liver tissue, vessels, or bones, which have been saturated with the organ cells. The body is tricked into not rejecting the foreign object which has been implanted, as the materials are made from the biocompatible chitosan and collagen components. Eventually, this matrix will decompose, and the implanted artificial tissue will then be replaced by natural human tissue.

Implanted materials have to be able to stay whole, and not disintegrate before new, natural tissue is formed in its place. These biocompatible 3D polymer materials are special in that they not only stimulate the restoration of natural tissues, but they can also regulate the resorption time, so premature disintegration is not an issue.

The researchers also used their new 3D materials to develop suture threads, blood vessel prostheses and wound covers, which were all proven effective during in vivo preclinical trials. So according to SPbPU, these materials have been recommended for use in cellular transplantation and tissue engineering.

It’s a vitally important mission in the world of modern medicine to develop artificial organs for the purposes of transplant, and continued development in this field depends on scientists and researchers, like the multi-disciplinary team from SPbPU, the Russian Academy of Sciences, and Pavlov First St. Petersburg State Medical University, creating bioresorbable and biocompatible polymer materials.

Discuss this story and other 3D printing topics at 3DPrintBoard.com or share your thoughts in the Facebook comments below. 

[Images: Peter the Great St. Petersburg Polytechnic University]