The greenhouse effect and plastic pollution caused by the accumulation of plastics have led to a global concern for environmental protection, as well as the development and application of biodegradable materials. Polypropylene carbonate (PPC) is a biodegradable polymer with the function of “carbon sequestration”, which has the potential to mitigate the greenhouse effect and the plastic crisis. It has the advantages of good ductility, oxygen barrier and biocompatibility. However, the mechanical and thermal properties of PPC are poor, especially the low thermal degradation temperature, which limits its industrial use. In order to overcome this problem, PPC can be modified using environmentally friendly materials, which can also reduce the cost of PPC-based products to a certain extent and enhance their competitiveness in terms of improving their mechanical and thermal properties. In this paper, we present different perspectives on the synthesis, properties, degradation, modification and post-modification applications of PPC. The modification part mainly introduces the influence of inorganic materials, natural polymer materials and degradable polymers on the performance of PPC. It is hoped that this work will serve as a reference for the early promotion of PPC.

Herein, a simple and environment-friendly method of coupling agent treatment of APP (ammonium polyphosphate) is provided and an optimum process of modification via coupling agent is identified. The effects of coupling agent type, dosage, modification time, and modification temperature on the modification of ammonium polyphosphate (APP) were investigated using an orthogonal experimental design. The modified ammonium polyphosphate (KAPP) was characterized under optimal process conditions using Fourier Transform Infrared (FT-IR), X-ray Diffraction (XRD), Thermogravimetry (TG), and Scanning Electron Microscope (SEM) analysis. The treatment greatly improved the water solubility, dispersibility, and thermal stability of KAPP; and the application of KAPP in polypropylene (PP) was investigated. The flexural properties, thermal stability, and flame retardancy were studied using mechanical testing, thermogravimetric analysis, oxygen index, and UL-94 vertical combustion. The results show that the KAPP-added polypropylene composites have better bending properties when compared with the APP-added PP composites. SEM analysis suggests that the surface of KAPP became smoother and flat; dispersion was better, compatibility with the PP matrix was improved, and there were no prominent voids and gaps in the cross-section. A different degree of improvement in flame retardancy was also observed as per the LOI and vertical combustion results, wherein the PP composites prepared by adding 20% KAPP achieved the LOI of 27.6% and passed the UL-94 test with V-0 rating.

Soil origin, mycorrhizal plant partners and environmental factors affect the growth and development of SongRong (Tricholoma matsutake). In order to clarify the relationships of fungi–bacteria networks and various influence factors in the habitat of SongRong, we chose three collection sites with a Quercus mongolica pure forest (plot A without SongRong was used as the control sample site), Q. mongolica mixed Rhododendron dauricum (plot B) and Q. mongolica mixed with R. dauricum and Pinus densiflora (plot C). By using high-throughput sequencing, we obtained a total of 4930 fungal and 55501 bacterial amplicon sequence variants (ASVs) based on internally transcribed spacer ribosomal RNA (ITS rRNA) and 16S ribosomal RNA (16S rRNA) sequencing via the Illumina NovaSeq platform. In the habitat soil of SongRong (plot B and plot C), alpha or beta diversity and species compositions of fungi and bacteria were different from plot A. The fungal–bacterial networks follow the selection rule that few dominant genera account for the greater relative abundance. Forest types, but not the host itself, drove the fungal–bacterial networks of the forest soil, and soil physicochemical characteristics and texture affected their abundance. The abundance of Tricholoma was affected by the fungal and bacterial abundance in the habitat.

Host plants are known to determine the distribution and development of ectomycorrhizal fungi such as Tricholoma matsutake; however, we found that the fruit body distribution of T. matsutake was different in Quercus mongolica pure or mixed forests. To clarify the fungal and other microbial composition rules of host plants, ectomycorrhizal root tip samples of Q. mongolica mixed with different plants were selected for study. By using high-throughput sequencing, we obtained 5229 fungal and 38,834 bacterial amplicon sequence variants (ASVs) as determined by internally transcribed spacer ribosomal RNA (ITS rRNA) and 16S ribosomal RNA (16S rRNA) sequencing via the Illumina NovaSeq platform. Among the neighboring plants, there were no significant differences in fungal or bacterial alpha diversity, but there was a significant difference (p < 0.05) in ectomycorrhizal alpha diversity. The fungal, bacterial and ectomycorrhizal fungal communities in the ectomycorrhizosphere of Q. mongolica all showed differences in beta diversity and species composition. In addition, the physical and chemical properties of the soil and the relationships among species could affect the relative abundance of fungi, bacteria and ectomycorrhizal fungi, but the soil microbial pool had little effect on microbial composition. Using PICRUSt2, some significantly up-regulated (p < 0.05) metabolic functions in ectomycorrrhizospheric microbial communities were predicted, which would be an interesting research field for ectomycorrhizal microecology.