Surface modification of polyimide fibers by novel alkaline–solvent hydrolysis to form high‐performance fiber‐reinforced composites

Abstract

We modified polyimide (PI) fibers by a novel hydrolysis approach and fabricated PI‐fiber‐reinforced novolac resin (NR) composites with enhanced mechanical properties. We first used an alkaline–solvent mixture containing potassium hydroxide liquor and dimethylacetamide (DMAc) for the surface modification of the PI fibers. The results indicate that the surface roughness and structure of the PI fibers were controlled by the hydrolysis time and the content of DMAc. With the optimized hydrolysis conditions, the tensile modulus of modified PI fibers improved 15% without compromises in the fracture stress, fracture strain, or thermal stability. The interfacial shear strength between the modified PI fibers and NR increased 57%; this indicated a highly enhanced interfacial adhesion. Finally, the tensile and flexural strengths of the composites increased 72 and 53%, respectively. This research provides an effective method for the surface modification of PI fibers and expands their applications for high‐performance composites. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46595.

Removal of gaseous methyl tert‐butyl ether using bagasse activated carbon pretreated with chemical agents

“…After activation, the material was modified by KOH, H 2 SO 4 , HNO 3 and CaCl 2 /HCl. These chemical modifications could increase BET surface area, pore volume and especially surface functional groups that enhance the adsorption of material . The acids could increase the surface positive charge on the material leading to enhanced MTBE removal which is negatively charged .…”

“…These chemical modifications could increase BET surface area, pore volume and especially surface functional groups that enhance the adsorption of material. [14][15][16][20][21][22] The acids could increase the surface positive charge on the material leading to enhanced MTBE removal which is negatively charged. [14][15][16]18,19 Three methods of modification were used: (i) mixing with KOH in a ratio of 1:3 (w/w); (ii) mixing with H 2 SO 4 and HNO 3 in a ratio of 1:3 (w/v); and (iii) mixing with CaCl 2 and HCl according to Goto et al 19 The impregnated samples were agitated in a shaker incubator at 150 rpm at 30 ∘ C for 24 h and then excess solution was decanted off.…”

“…Calcium chloride (CaCl 2 ) can increase calcium ion (Ca + ) on the material surface, and these positive charges effectively bond with the MTBE molecule which is negatively charged . Potassium hydroxide (KOH) and nitric acid (HNO 3 ) can increase the Brunauer‐Emmett‐Teller (BET) surface area and pore volume of material . In addition, the MTBE adsorption mechanism on various activated carbons and bagasse modifications was investigated by Fourier transform infrared spectroscopy (FTIR) and elution.…”

“…19 Potassium hydroxide (KOH) and nitric acid (HNO 3 ) can increase the Brunauer-Emmett-Teller (BET) surface area and pore volume of material. [14][15][16][20][21][22] In addition, the MTBE adsorption mechanism on various activated carbons and bagasse modifications was investigated by Fourier transform infrared spectroscopy (FTIR) and elution.…”

Effect of waterborne epoxy resin sizing on the surface and properties of high‐strength‐high‐modulus polyimide fibers

“…Yi et al 18 modified PI fibers by a novel hydrolysis approach (an alkaline‐solvent mixture containing potassium hydroxide liquor and DMAc) and the tensile and flexural strengths of the PI fibers/novolac resin composites increased 72 and 53%, respectively. Yang et al 19 carried out the surface decoration of PI fibers through surface alkali treatment, carboxylation modification, surface functionalization with acyl chloride groups and amino groups, and surface grafting of CNTs. The results indicated that the compressive strength and flexural strength of composites were increased remarkably by 120 and 283%, respectively.…”