Recycled moulded polyimide materials obtained by high‐energy ball milling

Abstract

This article presents a method of manufacturing moulding polyimide (PI) from recycling pyromellitic dianhydride‐4,4′oxydianiline PI films. Recycled PI powders were obtained by grinding PI films in high‐energy ball mill. In order to improve the sintering behavior of the recycled PI, a commercial PI powder (trade mark PM‐69) and a liquid PI resin (trade mark SP‐97) were chosen as modifying additions. PI/PM‐69 and PI/SP‐97 compositions were obtained by high‐energy ball mill. Bulk samples were obtained by compression moulding at 400 °C. The mechanical properties of the moulded PI and the reinforcing action of the PM‐69 and SP‐97 are strongly dependent on the mean size of the recycled PI powders. The flexural strength of 87 MPa and the deformation at failure −4.2% were achieved for the moulded PI/SP‐97 (10 wt %) samples. The resulting materials showed linear behavior of elastic modulus in a temperature range of 50–350 °C. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46733.

Preparation of Polyimide Powders via Hydrothermal Polymerization and Post-Heat Treatment for Application to Compression-Molding Materials

“…weights in the compression process and the release of water, which is a byproduct of imidization in the subsequent heating process. 15 In comparison, compression-molded specimens prepared with T-PI powders exhibited an increased tensile strength of up to 57.9 MPa. These results indicate that enhanced tensile strength can be achieved by post-heat treatment.…”

“…The FT-IR spectra and TGA curves of T-PI powders demonstrate that post-heat treatment achieved complete imidization. In addition, the T-PI powders exhibited excellent thermal stability based on the rigid aromatic ring and imide structures. − …”

“…They are classified as high-performance polymers and used widely in aerospace, membranes, microelectronics, and optoelectronics due to their excellent thermal and mechanical properties and chemical resistance. − For example, a PI powder prepared from pyromellitic dianhydride (PMDA) and 4,4′-oxydianiline (ODA) is a lightweight and heat-resistant compression-molding material. A commercial example of PMDA-ODA PI, DuPont Corporation’s Vespel SP-1 product, is machined into bearings or sealing parts that are used under extremely harsh conditions. − The compression-molding process ensures that the PI particles coalesce tightly, in what is called a sintering process. , The molecular weight, degree of crystallinity, and specific surface area of the PI powder are known to influence the sintering behavior. − …”

“…However, conventional synthesis of PMDA-ODA PI powder is performed using organic solvents such as N -methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), dimethylacetamide (DMAc), and cresol. − The use of the toxic high-boiling-temperature solvents presents economic and environmental disadvantages. In addition, the high degree of complexity of the manufacturing process prevents the application of compression-molding in various fields. ,− …”

New High-Performance Materials: Bio-Based, Eco-Friendly Polyimides

“…One solution to this issue is the use of polymer wastes of the same nature and proper tuning of the milling process. For example, common PMDA-ODA (pyromellitic dianhydride-4,4 0 -oxydianiline) PI films were grinded to powders and mixed with another commercial PI powder (BTDA [3,3 0 ,4,4 0 -benzophenonetetracarboxylic dianhydride]-ODA) and a liquid, BTDA-based, commercial PI resin [168].…”