A systematic sequence of materials was investigated to develop phytic-acid (Phyt)–based flame retarded poly (lactide acid) (PLA), while factoring in molecular weight (MW), crystallinity and mechanical properties. Synergistic approaches were developed based on combinations with lignin and expandable graphite (EG), as well as by applying different Phyt salts of melamine (Mel), piperazine (Pip), and arginine (Arg). Compounds were twin screw extruded, injection molded, hot pressed and investigated with thermal analysis, size exclusion chromatography, infrared spectroscopy, tensile testing, limited oxygen index (LOI), UL 94, cone calorimeter, and scanning electron microscope. 16.7 wt.% flame retardant (FR) slightly enhances crystallization while MW remains unchanged in PLA Phyt Arg and PLA Phyt Mel. LOI was improved to 43.7 vol.% for PLA Phyt Arg, UL 94 V0 achieved for PLA Phyt Pip. Cone calorimeter results show total heat evolved reduced by 14 %, maximum average rate of heat emission 43 % lower, and peak heat release rate reduced by 50 % for PLA Phyt Mel. Phyt Mel combined with EG increased the char yield of PLA to 20 wt.% and 15.5 wt.% at 600 and 900 ◦C, respectively. Phyt is exploited to enhance char yield, stabilize the intumescent char, and lower the apparent effective heat of combustion. The combination of Phyt Mel and EG was proposed as an efficient FR for PLA via an evidence based developing route.

Plastics components are degrading over time to small entities mostly known as microplastics (MP). Microplastics particles (MPPs) (by definition <5 mm) can enter the human food chain on different levels. MPPs have been found in several organisms and human heart tissue. MPPs also occur in the plant world. MPPs can be analyzed by light microscopy (LM). The different MP hydrocarbons distinguish from biomaterial matrices. But the degradation doesn’t stop. Microplastics can degrade further to nanoparticles (NPs), being smaller than cells. These nanoplastics particles (NPPs) require higher efforts to be detected. Electron microscopy (EM) is suitable to depict those nanoscale regions. Metal nanoparticles (MNPs) are often well visible in bulk biomaterial with scanning electron microscopy (SEM). But polymeric nanoparticles (PNPs) are more difficult to be detected in biomaterials than MNPs. Dependent on experiment and imaging conditions, PNPs can be distinguished from bulk biomaterial with SEM. Thus, we approach this issue with correlative microscopy (CM) to develop reliable NPP analytics. Using a plant model system with PNPs, combining LM and fluorescence microscopy (FM) with SEM data in a correlative light and electron microscopy (CLEM) approach, non-uniform patch formation of NPPs in- and outside the biomaterial matrix is observed. Energy-dispersive X-ray spectroscopy (EDS), Raman, micro-computer tomography (uCT), ultramicrotomy (UM) and focused ion beam (FIB) data provide additional information. Specific discovery of contaminated plant biomaterial areas is thus possible with single NP resolution. The investigation of the biomaterial matrix behaviour exposed to different PNP sizes and materials is so enabled. The procedural correlative microscopy approach reveals that PNPs seem to be tightly attached to the biomaterial. It indicates further that basic food cleaning procedures might be insufficient for PNP or NPPs removal. The model system can reliably detect PNPs, showing solution pathways in general NPPs analytics.

A systematic sequence of materials was investigated to develop phytic-acid (Phyt)–based flame retarded poly(lactide acid) (PLA), while factoring in molecular weight (MW), crystallinity and mechanical properties. Synergistic approaches were developed based on combinations with lignin and expandable graphite (EG), as well as by applying different Phyt salts of melamine (Mel), piperazine (Pip), and arginine (Arg). Compounds were twin screw extruded, injection molded, hot pressed and investigated with thermal analysis, size exclusion chromatography, infrared spectroscopy, tensile testing, limited oxygen index (LOI), UL 94, cone calorimeter, and scanning electron microscope. 16.7 wt.% flame retardant (FR) slightly enhances crystallization while MW remains unchanged in PLA Phyt Arg and PLA Phyt Mel. LOI was improved to 43.7 vol.% for PLA Phyt Arg, UL 94 V0 achieved for PLA Phyt Pip. Cone calorimeter results show total heat evolved reduced by 14 %, maximum average rate of heat emission 43 % lower, and peak heat release rate reduced by 50 % for PLA Phyt Mel. Phyt Mel combined with EG increased the char yield of PLA to 20 wt.% and 15.5 wt.% at 600 and 900 °C, respectively. Phyt is exploited to enhance char yield, stabilize the intumescent char, and lower the apparent effective heat of combustion. The combination of Phyt Mel and EG was proposed as an efficient FR for PLA via an evidence based developing route.

The world-wide plastics pollution into nature enters the human food chain as degradation products, influencing environmental habitat and health. Micro- and nanoplastics as foreign bodies contaminating beverages and foods on the cellular level are likely to have a long-term impact on nutrition growth, public and personal health. Nanoparticles and their spatial location are generally difficult to detect in biological specimens, especially plastic particles due to their analogous hydrocarbon-based matrix. Reliable analysis methods for the discovery of micro- and nanoplastic particles in entities are not fully established yet. We are therefore developing a correlative workflow for detecting plastics residuals in cellular tissue. We determined that light microscopy (LM) is usable for a coarse estimation of the contamination grade of plant samples. Due to its optical diffraction limit, LM rather detects nanoparticle patches than single particles, shown with fluorescent particles. Scanning electron microscopy (SEM) instead provides higher resolution, especially for single particle detection. EM sample staining is still required to depict polymerous nanoparticle specimens. Using LM and SEM data in a CLEM approach with TESCAN CORAL, discovery of contaminated plant areas is possible with single nanoparticle resolution. It reveals that nanoparticles seem to be tightly attached to the plant material. It indicates further that basic food cleaning procedures might be insufficient for particle removal. The workflow circumvents correlative sample 3D-topography issues. But insights into the plant matrix is best possible with z-information. Therefore, we additionally use focused ion beam (FIB) to determine inclusions of micro- and nanoplastics in the tissue/cellular matrix, investigating the optimal procedural approach as model for biomaterial systems. Procedural correlative microscopy provides a promising analysis method for the semiquantitative analysis of micro- and nanoparticles plant contaminations.