A New Process of Thermoplastic Polypropylene Reinforced by Interlayered Activated Carbon Fiber Treated by Electron Beam Irradiation under Nitrogen Gas Atmosphere with Oxygen Prior to Assembly and Hot-Press

Abstract

A new process of internal activation of carbon fiber reinforced thermoplastic polymer (CFRTP) of polypropylene (PP) by applying electron beam irradiation (EBI) under oxygen (O 2 )rich nitrogen gas (N 2 ) atmosphere to CF chopped strand matt (CSM) layers prior to assembly and hot press to strengthen the typically weak CF/thermoplastic polymers (TPs) adhesion was proposed. Samples were interlayered composite with layup of alternating PP and CF plies, [PP] 4 [CF] 3 . Composite fabrication was performed by one directional hot-press under constant pressure of 4.0 MPa at 473 K for 1 min. Results showed applying an optimum 0.22 MGy-EBI under protective N 2 gas with O 2 concentrations between 200 ppm and 200,000 ppm mostly improved the bending strength (· b ) while reducing strain at the bending strength (· b ) apparently increasing the elasticity. The method appears to work well for the weakest samples in the data sets: at low accumulative probability P f = 0.06 by median rank method, · b was apparently improved by the 200 ppm and 2,000 ppm O 2 atmospheres. Namely, 0.22 MGy-EBI under N 2 gas atmosphere with 200 ppm to 2,000 ppm-O 2 improved · b at P f = 0.06 (57 MPa) about 21%, over that of untreated (47 MPa). Strength increase could be explained by mutual entangling of both sizing epoxy film on CF and PP with strong covalent bonding, which formation of direct CF: C:C :PP induced by EBI and oxygen assisted CF: C:O:C :PP by concentrating the O 2 gas molecules from 200 ppm to 2,000 ppm-O 2 in N 2 atmosphere, rather than weak molecular bonding CF-(H 2 O, N 2 , O 2 )-PP for the untreated samples. Moreover, the action of the EBI apparently acts to clean residual H 2 O, N 2 , and O 2 to purify and activate the CF surface increasing polar group and active site density. They most likely contributed to bending strength enhancement. The 0.22 MGy-EBI in O 2 -rich N 2 atmosphere appears to be a viable method to increase carbon fiber-thermoplastic polypropylene adhesion enhancing reliability and safety of the PP

A new strengthening process of thermoplastic polypropylene reinforced by interlayered activated sizing film-free carbon fiber treated by electron beam irradiation under oxygen-rich nitrogen gas prior to assembly and hot-press

“…Moreover, an interlayered composite [PP] 4 [CF] 3 with same conditions as this study of EBI in O 2 -rich N 2 atmosphere but to sized CF mat prior to lamination assembly and hot press has been carried out. 25 EBI of 0.22 MGy under protective N 2 gas with O 2 concentrations of 200 ppm and 2,000 ppm to sized CFs improved maximum bending strength (r b ) at P f ¼ 0.06 (57 MPa) about 21%, over that of untreated (47 MPa) while reducing the strain (e b ) at the r b apparently raising elasticity. 25 The 200 ppm O 2 condition improved r b at all P f .…”

“…25 EBI of 0.22 MGy under protective N 2 gas with O 2 concentrations of 200 ppm and 2,000 ppm to sized CFs improved maximum bending strength (r b ) at P f ¼ 0.06 (57 MPa) about 21%, over that of untreated (47 MPa) while reducing the strain (e b ) at the r b apparently raising elasticity. 25 The 200 ppm O 2 condition improved r b at all P f . Improvements in the [PP] 4 [CF] 3 with sized CFs were reported to be attributed to mutual entangling of sizing epoxy film on CF and PP along with active oxygen groups generated on the CFs creating strong covalent bonding with the PP.…”

“…Improvements in the [PP] 4 [CF] 3 with sized CFs were reported to be attributed to mutual entangling of sizing epoxy film on CF and PP along with active oxygen groups generated on the CFs creating strong covalent bonding with the PP. 25 Since CFRTP without sizing has lower strength than that of sized, the purpose is to demonstrate HLEBI under O 2 rich N 2 atmosphere can increase bending strength in sizing film free (removed sizing) carbon fiber (SFF-CF) interlayered [PP] 4 [SFF-CF] 3 samples.…”

Strengthening Process by Electron Beam to Carbon Fiber for Impact Strength Enhancement of Interlayered Thermoplastic-Polypropylene Carbon Fiber Composite

“…Since the short solidification cycle of TPs advances cost reduction, glass fiber reinforced thermoplastic polymers (GFRTPs) [ 2 , 3 ] have been used in automobile manufacture. On the other hand, TPs and CF are difficult to adhere due to their being nonpolar, having low wettability, and hydrophobicity with their chemically inert surfaces [ 4 ].…”

“…Therefore, a wide body of research has been focusing on CF surface treatments to strengthen adhesion at the CF/Polymer interface [ 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 ]. One method used is to create higher interfacial friction at the CF surface by acidic modification [ 5 ], however, drawbacks are lowered strength [ 6 , 7 ] by degradation of the surface, along with weight reduction of the fiber itself [ 8 ].…”