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Polymer blends containing up to 70% organosolv lignin content and lyotropic cellulose derivatives have been established as "lignin inks" for direct ink writing of fully biobased 3D parts. However, a fast-crosslinking mechanism is needed to improve throughput and design space. In this paper, UV-photocrosslinkable organosolv lignin/hydroxypropyl cellulose inks are formulated through doping with common photocrosslinkers. The most potent photocrosslinkers for neat hydroxypropyl cellulose, lignin and their blends are determined through a series of DOEs. Hydroxypropyl cellulose is significantly more amenable to photocrosslinking than organosolv lignin. The optimal photocrosslinkable ink formulations are printable and exhibit up to 70% gel content, although thermal post-curing remains essential. Chemical, thermal, and mechanical investigations of the photocrosslinked 3D parts evidence efficient crosslinking of HPC through its hydroxyl groups, while lignin appears internally plasticized and/or degraded during inefficient photocrosslinking. Despite this, photocrosslinkable inks exhibit improved tensile properties, shape flexibility, and fidelity. The heterogeneous crosslinking and residual creep highlight the need to further activate lignin for homogeneous photocrosslinking in order to fully exploit the potential of lignin inks in DIW. [ABSTRACT FROM AUTHOR]

Condensed and hydrolysable tannins are non-toxic natural polyphenols that are a commercial commodity industrialized for tanning hides to obtain leather and for a growing number of other industrial applications mainly to substitute petroleum-based products. They are a definite class of sustainable materials of the forestry industry. They have been in operation for hundreds of years to manufacture leather and now for a growing number of applications in a variety of other industries, such as wood adhesives, metal coating, pharmaceutical/medical applications and several others. This review presents the main sources, either already or potentially commercial of this forestry by-materials, their industrial and laboratory extraction systems, their systems of analysis with their advantages and drawbacks, be these methods so simple to even appear primitive but nonetheless of proven effectiveness, or very modern and instrumental. It constitutes a basic but essential summary of what is necessary to know of these sustainable materials. In doing so, the review highlights some of the main challenges that remain to be addressed to deliver the quality and economics of tannin supply necessary to fulfill the industrial production requirements for some materials-based uses. [ABSTRACT FROM AUTHOR]