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.

In this study, a composite modifier for wood impregnation is prepared, which is functional and environmentally friendly. The surface of silica sol was modified by using KH-560. The modified silica sol, melamine, and glyoxal were used as raw materials. The silica sol/melamine glyoxal resin (from now on referred to as Silica sol/MG) composite modifier was prepared based on in-situ polymerization. The physicochemical properties (viscosity, solid content and etc.) of the composite modifier were evaluated. The structural and thermal properties were characterized and analyzed by FTIR spectroscopy, particle size distribution, TG and DSC. The results showed that the viscosity and solid content of the composite modifier decreased with the increase in the mass of the silica sol. The FTIR spectroscopy showed peaks at 473 cm⁻¹ and 1101 cm⁻¹, which were assigned to bending and stretching vibrations of the Si-O-Si bond, respectively, indicating that the modified silica sol was successfully introduced into the MG resin. When the modified silica sol mass fraction was 30%-40%, the particle size distribution of the composite modifier was relatively uniform. TG analysis found that the thermal stability of the composite modifier was significantly improved compared with the unmodified resin. DSC analysis showed that adding the modified silica sol reduced the curing temperature of the modifier from 115.5 °C to 107.9 °C.

This study used silica sol, phenol, formaldehyde, etc. as raw materials to prepare silica sol/phenolic resin based on in-situ polymerization. The influence of silica sol content on the viscosity, solid content, and other properties of the composite resin were discussed. The structure and performance of the product were characterized and tested via laser particle size analyzer, infrared spectrum analyzer, thermogravimetric (TG) analyzer, and rheometer. The results show that the viscosity of the composite resin increased with increased silica sol content, and the solid content and the free formaldehyde content exhibited the opposite trend. The laser particle size analysis revealed that when the amount of silica sol was 40%, the particle size distribution of the composite resin was relatively uniform. Fourier transform infrared analysis illustrated a new chemical bond of Si-O-C formed between silica sol and phenolic resin. TG analysis showed that when the amount of modified silica sol was added at a 40% level, the decomposition temperature of composite resin (10% weight loss) increased from 294.8 to 324.4 °C, and the residual amount increased from 55.2% to 60.2%; rheological analysis revealed that when the content of silica sol was 40%, it had better flow properties, creating conditions for the composite resin to penetrate the wood.

In order to overcome the defects of fast-growing poplar wood, such as low strength and poor toughness, this paper introduces a method of modifying poplar wood via impregnation with silica sol/melamine–glyoxal (silica sol/MG) resin and explores its effects on the physical, mechanical, and thermal properties of poplar wood. It was found via scanning electron microscopy that the composite modifier covered and filled the cell lumen, cell interstitial space, and cell wall pores of poplar wood. Further, infrared spectroscopy and X-ray photoelectron spectroscopy analyses confirmed that chemical cross-linking occurred between the silica sol/MG resin composite modifier and the internal groups of poplar wood and that the Si-O-Si flexible long chains introduced in the composite modifier formed a cross-linking network with poplar wood such as Si-O-Si and Si-O-C, which led to the improvement of the physical and mechanical properties and the enhancement of the thermal stability of poplar wood. The method provides a theoretical basis for the high-value utilization of fast-growing poplar wood.