Intrinsically heat-sealable polyimide films derived from 2,3,3′,4′-oxydiphthalic anhydride and aromatic diamines with various ether linkages

Abstract

A series of polyimides (PIs) with good heat sealability were synthesized from an asymmetric aromatic dianhydride, 2,3,3 0 ,4 0 -oxydiphthalic anhydride, and aromatic ether diamines with different structures featured by ether amounts, substituted positions of ether linkages, and substituted positions of amino groups. In detail, the effects of these three substructures in the diamine were investigated on thermal resistance, thermoplasticity, and heat sealability of the PI film. It is found that the glass transition temperatures and heat-sealing strengths of the prepared PI films are influenced to different extents by the variations of the substructures, because of their different contributions to the chain mobility. These PI films are demonstrated to possess good heat sealability evidenced by completely fused heat-sealing interfaces and high heat-sealing strengths up to 580 N m À1 .

Preparation of organo‐soluble co‐polyimides using N‐methyl‐2‐pyrrolidone as the solvent via one‐pot high‐temperature polymerization

“…To overcome the above problems, much efforts have been focused on designing new PIs with bulky pendent groups (trifluoromethyl groups, etc.) or flexible linkages (such as ether or sulfone bonds) to decrease the packing densities and intermolecular interactions of polymer chains. Our previous report has illustrated that the incorporation of bulky trifluoromethyl groups into the PI backbones results in great benefits for improving polymer solubility without sacrificing the excellent mechanical and thermal properties of PIs .…”

Preparation and properties of heat-sealable polyimide films with comparable coefficient of thermal expansion and good adhesion to copper matrix

“…One of the main purposes for the current work is to increase the T g values of the thermoplastic aODPA-PIs. In our previous work, a series of aODPA-PI films have been developed from aromatic diamines containing different ether contents [18]. Introduction of flexible ether linkages greatly deteriorated the glass transition temperature (T g ) values of the polymers.…”

“…The optimal conditions were obtained by observing the micro-interface between the PI film and copper foil, in which homogeneous adhesion was achieved. First, the peeling strength samples were prepared according to the procedures reported before in our laboratory, as shown in Figure 7 [18]. The 180° peeling strength of the PI/Cu composite films were tabulated in Table 4.…”

“…Thus, heat-sealing samples were prepared first. Heat sealing of PI films was implemented with the hot-bar method on laboratory heat sealer, as presented in our previous work [18]. A pair of PI film and copper foil (thickness: 0.025 mm) with the size of 90×70×0.025 mm were overlapped and plugged into the platen molds for 20 mm width at a set temperature depending on the glass transition temperatures (T g s) of the PI samples.…”

“…Although several classes of heat sealable PI films have been reported in the literature, further improvements for their performances, including decreasing their CTE values to be match with that of copper foil (CTE: 17·10 -6 1/K) [16,17] and increasing their adhesion to copper matrix (peeling strength >1.0 N/mm) have been continuously performed so as to meet the severe demands of advanced FCCL fabrications. In the current work, as one of our continuous efforts developing high performance thermoplastic PI films for FCCLs [14,18], a series of PI films based on aODPA and aromatic diamines with different characteristics were designed, synthesized and characterized. The effects of the specific substituents on their heat sealability, dimensional stability at elevated temperatures, and adhering properties to copper foil were investigated in detail.…”