Effects of cross-linking methods for polyethylene-based carbon fibers: review

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  • ABSTRACT

    In recent decades, there has been an increasing interest in the use of carbon fiber reinforced plastic (CFRP) in aerospace, renewable energy and other industries, due to its low weight and relatively good mechanical properties compared with traditional metals. However, due to the high cost of petroleum-based precursors and their associated processing costs, CF remains a specialty product and as such has been limited to use in high-end aerospace, sporting goods, automotive, and specialist industrial applications. The high cost of CF is a problem in various applications and the use of CFRP has been impeded by the high cost of CF in various applications. This paper presents an overview of research related to the fabrication of low cost CF using polyethylene (PE) control technology, and identifies areas requiring additional research and development. It critically reviews the results of cross-linked PE control technology studies, and the development of promising control technologies, including acid, peroxide, radiation and silane cross-linking methods.


  • KEYWORD

    polyethylene , cross-linked , low cost carbon fiber

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  • [Fig. 1.] (a) Chain scission in polyethylene (PE); (b) the cross-linking reaction, or formation of C-C covalent bonds between adjacent molecular chains in PE [55].
    (a) Chain scission in polyethylene (PE); (b) the cross-linking reaction, or formation of C-C covalent bonds between adjacent molecular chains in PE [55].
  • [Fig. 2.] Non-isothermal crystallization of gamma irradiated low density polyethylene (LDPE) in the presence of oxygen. Reprinted with permission from [56]: (a) non-isothermal crystallization curves obtained at a cooling rate of 10o C/min of samples prepared with different oxygen concentrations (%v/v), irradiated with 33 kGy, 83 kGy, 153 kGy, and 222 kGy; (b) activation energies of studied materials as a function of the relative degree of crystallinity; (c) CCT plots for A original and irradiated LDPE (nitrogen atmosphere) and B irradiated with 222 kGy in different atmospheres.
    Non-isothermal crystallization of gamma irradiated low density polyethylene (LDPE) in the presence of oxygen. Reprinted with permission from [56]: (a) non-isothermal crystallization curves obtained at a cooling rate of 10o C/min of samples prepared with different oxygen concentrations (%v/v), irradiated with 33 kGy, 83 kGy, 153 kGy, and 222 kGy; (b) activation energies of studied materials as a function of the relative degree of crystallinity; (c) CCT plots for A original and irradiated LDPE (nitrogen atmosphere) and B irradiated with 222 kGy in different atmospheres.
  • [Fig. 3.] Characteristics and properties of gamma irradiated cross-linked low density polyethylene foams. Reprinted with permission from [57]: (a) presents thermal behavior results obtained by each individual foam sample; (b) melt strength, extrudate swell and expansion index for 0?30 kGy foams samples; (c) gel fraction and melt flow index results in 0?30 kGy foams samples; (d) ATR spectra for 0?30 kGy foams samples (identification of carbonyl range: 1699, 1716 and 1743 cm?1).
    Characteristics and properties of gamma irradiated cross-linked low density polyethylene foams. Reprinted with permission from [57]: (a) presents thermal behavior results obtained by each individual foam sample; (b) melt strength, extrudate swell and expansion index for 0?30 kGy foams samples; (c) gel fraction and melt flow index results in 0?30 kGy foams samples; (d) ATR spectra for 0?30 kGy foams samples (identification of carbonyl range: 1699, 1716 and 1743 cm?1).
  • [Fig. 4.] Thermal and structural properties of energy electron beam irradiation on low density polyethylene (LDPE). Reprinted with permission from [58]: (a) MDSC thermograms of the second scan cycle for the nonirradiated and irradiated LDPE samples; (b) FTIR spectra for the non-irradiated and irradiated LDPE samples (carbonyl range); (c) melting temp erature (Tm), crystallisation temperature (Tc) and crystallinity of the LDPE, before and after electron beam irradiation.
    Thermal and structural properties of energy electron beam irradiation on low density polyethylene (LDPE). Reprinted with permission from [58]: (a) MDSC thermograms of the second scan cycle for the nonirradiated and irradiated LDPE samples; (b) FTIR spectra for the non-irradiated and irradiated LDPE samples (carbonyl range); (c) melting temp erature (Tm), crystallisation temperature (Tc) and crystallinity of the LDPE, before and after electron beam irradiation.
  • [Fig. 5.] Cross-link density and crystalline structure of electron-irradiation on low density polyethylene (LDPE) and high density PE (HDPE). Reprinted with permission from [59]: (a) gel content, cross-link density and hot set data for cross-linked LDPE and HDPE with different irradiation doses; (b) melting temperature Tm heat of fusion ΔHm, degree of crystallinity Xc of first heating of samples and crystallization temperature Tc of irradiated LDPE and HDPE with different irradiation dose; (c) WAXS curves (shifrted 3D-plot) for HDPE irradiated with different dose rates (dose in kGy: ― 0; - + - 50; - × - 100; - ● - 150; - ○ - 200; - ☆ - 250).
    Cross-link density and crystalline structure of electron-irradiation on low density polyethylene (LDPE) and high density PE (HDPE). Reprinted with permission from [59]: (a) gel content, cross-link density and hot set data for cross-linked LDPE and HDPE with different irradiation doses; (b) melting temperature Tm heat of fusion ΔHm, degree of crystallinity Xc of first heating of samples and crystallization temperature Tc of irradiated LDPE and HDPE with different irradiation dose; (c) WAXS curves (shifrted 3D-plot) for HDPE irradiated with different dose rates (dose in kGy: ― 0; - + - 50; - × - 100; - ● - 150; - ○ - 200; - ☆ - 250).
  • [Fig. 6.] Surface properties of ion beam modification of polyethylene. Reprinted with permission from [60]: (a) AFM micrographs of the HDPE surface of pristine sample A and after the Ar-ion bombardment with a dose of 1 × 1016 at/cm2 B; (b) hardness and friction coefficient for HDPE as a function of the He-ion dose; (c) hardness and friction coefficient for HDPE as a function of the Ar-ion dose; (d) maximal values of hardness for different types of polyethylene prior and after ion bombardment; (e) maximal values of friction coefficient for different types of polyethylene prior and after ion bombardment.
    Surface properties of ion beam modification of polyethylene. Reprinted with permission from [60]: (a) AFM micrographs of the HDPE surface of pristine sample A and after the Ar-ion bombardment with a dose of 1 × 1016 at/cm2 B; (b) hardness and friction coefficient for HDPE as a function of the He-ion dose; (c) hardness and friction coefficient for HDPE as a function of the Ar-ion dose; (d) maximal values of hardness for different types of polyethylene prior and after ion bombardment; (e) maximal values of friction coefficient for different types of polyethylene prior and after ion bombardment.
  • [Fig. 7.] Scheme of the mechanism of peroxide polyethylene cross-linking [71].
    Scheme of the mechanism of peroxide polyethylene cross-linking [71].
  • [Fig. 8.] Thermal and morphology properties of structural effects on cross-linked polyethylene. Reprinted with permission from [63]: (a) changes in vinyl content, gel content and crosslink density with DCP content; (b) elongation at break and ultimate tensile strength for material A and B; (c) Tm, Tc, and Xc as function of DCP content; (d) scanning electron micrographs on etched samples showing the change in spherulite size and structure and appearance after crosslinking with DCP; (e) morphology of materials A and B with increasing peroxide content.
    Thermal and morphology properties of structural effects on cross-linked polyethylene. Reprinted with permission from [63]: (a) changes in vinyl content, gel content and crosslink density with DCP content; (b) elongation at break and ultimate tensile strength for material A and B; (c) Tm, Tc, and Xc as function of DCP content; (d) scanning electron micrographs on etched samples showing the change in spherulite size and structure and appearance after crosslinking with DCP; (e) morphology of materials A and B with increasing peroxide content.
  • [Fig. 9.] Thermal and catalytic pyrolysis properties of cross-linked polyethylene. Reprinted with permission from [71]; (a) calorimetric curves of samples with different peroxide concentration; (b) temperature corresponding to 10% of weight loss for different samples with and without catalyst; (c) gel content measurements; (d) TGA A and DTG B curves for samples without catalyst: (―) 0% peroxide, (?) 0.5% peroxide, (*) 1% peroxide, (?) 2% peroxide, (●) 3% peroxide, and (▲) 4% peroxide; (e) melting enthalpy A and melting temperature B of crosslinked polyethylene samples with different peroxide concentration.
    Thermal and catalytic pyrolysis properties of cross-linked polyethylene. Reprinted with permission from [71]; (a) calorimetric curves of samples with different peroxide concentration; (b) temperature corresponding to 10% of weight loss for different samples with and without catalyst; (c) gel content measurements; (d) TGA A and DTG B curves for samples without catalyst: (―) 0% peroxide, (?) 0.5% peroxide, (*) 1% peroxide, (?) 2% peroxide, (●) 3% peroxide, and (▲) 4% peroxide; (e) melting enthalpy A and melting temperature B of crosslinked polyethylene samples with different peroxide concentration.
  • [Fig. 10.] Thermal conduction behaviors of chemically cross-linked high-density polyethylenes (HDPEs). Reprinted with permission from [72]; (a) DSC thermographs of pristine and crosslinked HDPEs via a heating scan; (b) A synchrotron WAXS patterns of HDPE and crosslinked HDPEs. Top and bottom insets show high magnification of (110) diffraction and amorphous halo B resolved peaks of HDPE, and C crystallite size of HDPE and crosslinked HDPEs; (c) gel contents and bulk densities of the pristine and crosslinked HDPEs with various DCP contents; (d) polarized optical micrographs of A HDPE and B crosslinked HDPE with DCP 3.0 wt.%; (e) characteristics of the pristine and crosslinked HDPEs with various DCP contents including thermal diffusivity, density and specific heat data.
    Thermal conduction behaviors of chemically cross-linked high-density polyethylenes (HDPEs). Reprinted with permission from [72]; (a) DSC thermographs of pristine and crosslinked HDPEs via a heating scan; (b) A synchrotron WAXS patterns of HDPE and crosslinked HDPEs. Top and bottom insets show high magnification of (110) diffraction and amorphous halo B resolved peaks of HDPE, and C crystallite size of HDPE and crosslinked HDPEs; (c) gel contents and bulk densities of the pristine and crosslinked HDPEs with various DCP contents; (d) polarized optical micrographs of A HDPE and B crosslinked HDPE with DCP 3.0 wt.%; (e) characteristics of the pristine and crosslinked HDPEs with various DCP contents including thermal diffusivity, density and specific heat data.
  • [Fig. 11.] Non-isothermal crystallization kinetics of peroxide-cross-linked polyethylene (XLPE): effect of solid state mechanochemical milling. Reprinted with permission from [73]; (a) DSC thermograms of non-isothermal crystallization for XLPE A, de-XLPE B, and LDPE C at the cooling rate of 2.5 ℃/min; (b) effect of mechanochemical milling on the gel content of XLPE; (c) characteristic data of nonisothermal crystallization exotherms for XLPE, de-XLPE, and LDPE at different cooling rates; (d) non-isothermal crystallization kinetic parameters based on the Ozawa method.
    Non-isothermal crystallization kinetics of peroxide-cross-linked polyethylene (XLPE): effect of solid state mechanochemical milling. Reprinted with permission from [73]; (a) DSC thermograms of non-isothermal crystallization for XLPE A, de-XLPE B, and LDPE C at the cooling rate of 2.5 ℃/min; (b) effect of mechanochemical milling on the gel content of XLPE; (c) characteristic data of nonisothermal crystallization exotherms for XLPE, de-XLPE, and LDPE at different cooling rates; (d) non-isothermal crystallization kinetic parameters based on the Ozawa method.
  • [Fig. 12.] Principal reactions involved in silane cross-linking of polyethylene [82].
    Principal reactions involved in silane cross-linking of polyethylene [82].
  • [Fig. 13.] Characterization and mechanical properties of cross-linked high density polyethylene (HDPE) by silane. Reprinted with permission from [83]: (a) yield strength and Young’s modulus as a function of processing conditions of HDPE, PEX -3% silane, and PEX -4% silane; (b) yield strength and Young’s modulus as a function of processing conditions of HDPE; (c) FTIR spectra of HDPE and PEXs crosslinked with 3% and 4% silane; (d) DTG curves of HDPE and PEX with 3% and 4% silane; (e) X-ray diffractograms of samples of HDPE and PEX with 3% and 4% silane; (f) gel content and solvent uptake factor values of the extraction carried out with trichloroethylene for crosslinked samples at crosslinking time of 90 min.
    Characterization and mechanical properties of cross-linked high density polyethylene (HDPE) by silane. Reprinted with permission from [83]: (a) yield strength and Young’s modulus as a function of processing conditions of HDPE, PEX -3% silane, and PEX -4% silane; (b) yield strength and Young’s modulus as a function of processing conditions of HDPE; (c) FTIR spectra of HDPE and PEXs crosslinked with 3% and 4% silane; (d) DTG curves of HDPE and PEX with 3% and 4% silane; (e) X-ray diffractograms of samples of HDPE and PEX with 3% and 4% silane; (f) gel content and solvent uptake factor values of the extraction carried out with trichloroethylene for crosslinked samples at crosslinking time of 90 min.
  • [Fig. 14.] Effect of silane carriers on silane grafting of high density polyethylene (HDPE) and properties of cross-linked products. Reprinted with permission From [84]: (a) FTIR spectra of HDPE, grafted HDPE, and grafted HDPE blended with various silane carriers; (b) IR peak positions and their assignments; (c) crosslink density as a function of immersing time of various crosslinked HDPE; (d) melting temperature (Tm), heat of fusion (?Hf), percentage of crystallinity (%χc) and crystallisation temperature (Tc) of various samples before and after performing a silane?crosslink reaction; (e) effect of silane carriers on the grafting index, rate of silane crosslinking, and gel content of various HDPE systems; (f) A modulus and B yield stress of unmodified, grafted and crosslinked systems; (g) A tensile strength at break and B elongation at break of unmodified, grafted and crosslinked systems; (h) effect of silane carrier on heat distortion temperature (HDT), onset of decomposition temperature (Tdonset), decomposition temperature (Td) and activation energy (Ed) of thermal decomposition reaction of various samples before and after performing a silane?crosslink reaction.
    Effect of silane carriers on silane grafting of high density polyethylene (HDPE) and properties of cross-linked products. Reprinted with permission From [84]: (a) FTIR spectra of HDPE, grafted HDPE, and grafted HDPE blended with various silane carriers; (b) IR peak positions and their assignments; (c) crosslink density as a function of immersing time of various crosslinked HDPE; (d) melting temperature (Tm), heat of fusion (?Hf), percentage of crystallinity (%χc) and crystallisation temperature (Tc) of various samples before and after performing a silane?crosslink reaction; (e) effect of silane carriers on the grafting index, rate of silane crosslinking, and gel content of various HDPE systems; (f) A modulus and B yield stress of unmodified, grafted and crosslinked systems; (g) A tensile strength at break and B elongation at break of unmodified, grafted and crosslinked systems; (h) effect of silane carrier on heat distortion temperature (HDT), onset of decomposition temperature (Tdonset), decomposition temperature (Td) and activation energy (Ed) of thermal decomposition reaction of various samples before and after performing a silane?crosslink reaction.
  • [Fig. 15.] Non-isothermal crystallization kinetics of peroxide-cross-linked polyethylene: effect of solid state mechanochemical milling. Reprinted with permission from [85]; (a) FTIR spectra of silane-grafted and crosslinked EOR samples; (b) effect of immersing time on gel content of various crosslinked samples A EOR, B 90/10 blend, C 70/30 blend, D 50/50 blend, and E LDPE; (c) crosslinking rate as a function of content of crystalline component in the crosslinked samples; (d) A relationship between solvent uptake factor and gel content. B logarithmic plot of solvent uptake factor and gel content; (e) relationship between IR absorption index and gel content.
    Non-isothermal crystallization kinetics of peroxide-cross-linked polyethylene: effect of solid state mechanochemical milling. Reprinted with permission from [85]; (a) FTIR spectra of silane-grafted and crosslinked EOR samples; (b) effect of immersing time on gel content of various crosslinked samples A EOR, B 90/10 blend, C 70/30 blend, D 50/50 blend, and E LDPE; (c) crosslinking rate as a function of content of crystalline component in the crosslinked samples; (d) A relationship between solvent uptake factor and gel content. B logarithmic plot of solvent uptake factor and gel content; (e) relationship between IR absorption index and gel content.
  • [Fig. 16.] Free radical modification of low density polyethylene (LDPE) with vinyltriethoxysilane. Reprinted with permission from [70]; (a) infrared spectra of LDPE and PE?VTES; (b) correlation between degree of functionalization (F) determined by RBS and ratio A958 / A2020 obtained from FTIR (r =0.995); (c) degree of functionalization as a function of VTES concentration for two DCP concentrations; (d) molecular weights of PE; (e) gel fraction of PE-VTESa ; (f ) crystallinity, melting temperature (Tm) and crystallization temperature (Tc) of PE and PE?VTES; (g) mechanical properties of PE and PE?VTES.
    Free radical modification of low density polyethylene (LDPE) with vinyltriethoxysilane. Reprinted with permission from [70]; (a) infrared spectra of LDPE and PE?VTES; (b) correlation between degree of functionalization (F) determined by RBS and ratio A958 / A2020 obtained from FTIR (r =0.995); (c) degree of functionalization as a function of VTES concentration for two DCP concentrations; (d) molecular weights of PE; (e) gel fraction of PE-VTESa ; (f ) crystallinity, melting temperature (Tm) and crystallization temperature (Tc) of PE and PE?VTES; (g) mechanical properties of PE and PE?VTES.
  • [Fig. 17.] Reaction mechanism of sulfuric acid with low density polyethylene, introducing sulfuric groups and carbon-to-carbon double bonds [86].
    Reaction mechanism of sulfuric acid with low density polyethylene, introducing sulfuric groups and carbon-to-carbon double bonds [86].
  • [Fig. 18.] Pyrolysis pathways of sulfonated polyethylene, an alternative carbon fiber precursor. Reprinted with permission from [87]: (a) scheme showing Ei5 elimination (top) and the radical chain reaction (bottom) for H4S; (b) M06-2X/6-311++G(3df,3pd)//M06-2X/6-31G** BDEs in kcal/mol at 298 K; (c) binned minima from R?SO3H rotational coordinate. Reactant A is in purple, B is in green, and C is in blue; (d) A TGA thermogram of partially functionalized PE fiber (inset: scanning electron micrograph of pyrolyzed fiber from a partially sulfonated polyethylene). B TGA thermogram of fully functionalized PE fiber (inset: scanning electron micrograph of pyrolyzed fiber from a fully sulfonated polyethylene).
    Pyrolysis pathways of sulfonated polyethylene, an alternative carbon fiber precursor. Reprinted with permission from [87]: (a) scheme showing Ei5 elimination (top) and the radical chain reaction (bottom) for H4S; (b) M06-2X/6-311++G(3df,3pd)//M06-2X/6-31G** BDEs in kcal/mol at 298 K; (c) binned minima from R?SO3H rotational coordinate. Reactant A is in purple, B is in green, and C is in blue; (d) A TGA thermogram of partially functionalized PE fiber (inset: scanning electron micrograph of pyrolyzed fiber from a partially sulfonated polyethylene). B TGA thermogram of fully functionalized PE fiber (inset: scanning electron micrograph of pyrolyzed fiber from a fully sulfonated polyethylene).
  • [Fig. 18.] Continued: (a) M06-2X/6-311++G(3df,3pd)//6-31G** Kooij Parameters from 300 to 1000 K for Various Reaction Stepsa ; (b) A experimental TGAs based on sulfonated PE at heating rates of 2.5 (red), 5 (green), 10 (blue), and 20 (pink) ℃/min. B H4S kMC simulations (1.6 ng mL?1 20 ℃/min) detailing TGA dependence on O˙H/H4S ratio: 3.3 × 10?7 (red), 3.3 × 10?6 (green), 3.3 × 10?5 (blue), 3.3 × 10?4 (pink), 6.7 × 10?4 (aqua), 1.3 × 10?3 (orange), 2.7 × 10?3 (gray), and experimental (black, based on sulfonated PE). C H4S kMC simulations (20 ℃/min) detailing TGA dependence on H4S density (first number) and high O˙H/H4S ratio (second number): 1.6 pg mL?1, 6.7 × 10?3 (red); 16 pg mL?1, 3.3 × 10?3 (green); 160 pg mL?1, 2.7 × 10?3 (blue); 1.6 ng mL?1, 2.7 × 10?3 (pink); 16 ng mL?1, 2.7 × 10?3 (aqua); 160 ng mL?1; 2.7 × 10?3 (gray); and experimental (black, based on sulfonated PE). D TGA (1.6 ng mL?1 20 ℃/min) mole ratio of H4S and O˙H as a function of temperature/time with O˙H/H4S ratio: 3.3 × 10?5 (aqua), 3.3 × 10?4 (pink), 6.7 × 10?4 (blue), 1.3 × 10?3 (green), and 2.7 × 10?3 (red). See the Supporting Information for all TGAs.
    Continued: (a) M06-2X/6-311++G(3df,3pd)//6-31G** Kooij Parameters from 300 to 1000 K for Various Reaction Stepsa ; (b) A experimental TGAs based on sulfonated PE at heating rates of 2.5 (red), 5 (green), 10 (blue), and 20 (pink) ℃/min. B H4S kMC simulations (1.6 ng mL?1 20 ℃/min) detailing TGA dependence on O˙H/H4S ratio: 3.3 × 10?7 (red), 3.3 × 10?6 (green), 3.3 × 10?5 (blue), 3.3 × 10?4 (pink), 6.7 × 10?4 (aqua), 1.3 × 10?3 (orange), 2.7 × 10?3 (gray), and experimental (black, based on sulfonated PE). C H4S kMC simulations (20 ℃/min) detailing TGA dependence on H4S density (first number) and high O˙H/H4S ratio (second number): 1.6 pg mL?1, 6.7 × 10?3 (red); 16 pg mL?1, 3.3 × 10?3 (green); 160 pg mL?1, 2.7 × 10?3 (blue); 1.6 ng mL?1, 2.7 × 10?3 (pink); 16 ng mL?1, 2.7 × 10?3 (aqua); 160 ng mL?1; 2.7 × 10?3 (gray); and experimental (black, based on sulfonated PE). D TGA (1.6 ng mL?1 20 ℃/min) mole ratio of H4S and O˙H as a function of temperature/time with O˙H/H4S ratio: 3.3 × 10?5 (aqua), 3.3 × 10?4 (pink), 6.7 × 10?4 (blue), 1.3 × 10?3 (green), and 2.7 × 10?3 (red). See the Supporting Information for all TGAs.
  • [Fig. 19.] Morphology and mechanical properties of amorphous carbon fibers from linear low density polyethylene. Reprinted with permission from [110]: (a) IR spectra of LLDPE films treated with chlorosulphonic acid for different periods of time. At = 30 min, bt = 1 h, ct = 2 h, dt = 4 h; (b) SEM micrograph of the surface of a chlorosulphonated LLDPE fibre showing longitudinal and perpendicular cracks (fibre B); (c) tensile strength and Young’s modulus of carbon fibres obtained from precursor B (chlorosulphonation time 12h) as a function of applied stress (heat-treatment temperature 900℃; heat-treatment time 5 min); (d) SEM micrograph of the surface texture of a carbon fibre made at 900 ~ C from precfirsor A (heat-treatment time 5 min, stress 0.10 MPa); (e) SEM micrograph of the surface texture of a carbon fibre made at 900 ~ C from precursor B (heat-treatment time 5 rain, stress 1.3 MPa).
    Morphology and mechanical properties of amorphous carbon fibers from linear low density polyethylene. Reprinted with permission from [110]: (a) IR spectra of LLDPE films treated with chlorosulphonic acid for different periods of time. At = 30 min, bt = 1 h, ct = 2 h, dt = 4 h; (b) SEM micrograph of the surface of a chlorosulphonated LLDPE fibre showing longitudinal and perpendicular cracks (fibre B); (c) tensile strength and Young’s modulus of carbon fibres obtained from precursor B (chlorosulphonation time 12h) as a function of applied stress (heat-treatment temperature 900℃; heat-treatment time 5 min); (d) SEM micrograph of the surface texture of a carbon fibre made at 900 ~ C from precfirsor A (heat-treatment time 5 min, stress 0.10 MPa); (e) SEM micrograph of the surface texture of a carbon fibre made at 900 ~ C from precursor B (heat-treatment time 5 rain, stress 1.3 MPa).
  • [Fig. 20.] Mechanical properties of amorphous carbon fibers from linear low density polyethylene, due to diameter. Reprinted with permission from [111]: (a) effect of chlorosulfonation time on the mechanical properties of carbon fibres, prepared from fibre A (●) and fibre B (○); (b) effect of fibre stress during pyrolysis of fibre B on the mechanical properties of the resulting carbon fibres. Heating rate : 26 ℃/min; (c) effect of carbon fibre diameter on the ultimate mechanical properties; (d) optimal chlorosulfonation time as a function of precursor fibre diameter); (e) effect of heating rate during pyrolysis of fibre B on the mechanical properties of the resulting carbon fibres. Fibre stress : 2.8 Mpa; (f) scanning electron micrograph of the fracture surface of a 1.90 GPa carbon fibre.
    Mechanical properties of amorphous carbon fibers from linear low density polyethylene, due to diameter. Reprinted with permission from [111]: (a) effect of chlorosulfonation time on the mechanical properties of carbon fibres, prepared from fibre A (●) and fibre B (○); (b) effect of fibre stress during pyrolysis of fibre B on the mechanical properties of the resulting carbon fibres. Heating rate : 26 ℃/min; (c) effect of carbon fibre diameter on the ultimate mechanical properties; (d) optimal chlorosulfonation time as a function of precursor fibre diameter); (e) effect of heating rate during pyrolysis of fibre B on the mechanical properties of the resulting carbon fibres. Fibre stress : 2.8 Mpa; (f) scanning electron micrograph of the fracture surface of a 1.90 GPa carbon fibre.
  • [Fig. 21.] Structure and properties during the conversion of polyethylene precursors to carbon fibers. Reprinted with permission from [54]: (a) burning Testing for Stabilized Fibers; (b) DSC scans of fiber samples stabilized at different temperatures and time. (1) Precursor, (2) 150℃ and 30 min, (3) 160℃ and 45 min, (4) 170℃ and 60 min; (c) DSC scans for differences between highly oriented polyethylene and partially drawn polyethylene. (1) Highly oriented polyethylene, (2) partially drawn polyethylene, (3) HOPE stabilized at 150℃ for 60 min, (4) PDPE stabilized at 150℃ for 30 min; (d) TGA scans (in nitrogen) of’ fiber samples stabilized at different temperatures and time. (1) Precursor, (2) 150℃ and 30 min, (3) 160℃ and 45 min, (4) 170℃ and 60 min; (e) tensile properties of resultant carbon fibers; (f) SEM photographs of resultant carbon fibers from a) insufficient stabilization and b) sufficient stabilization; (g) X-ray diffraction photographs of fiber samples. a) precursor, b) partially stabilized.
    Structure and properties during the conversion of polyethylene precursors to carbon fibers. Reprinted with permission from [54]: (a) burning Testing for Stabilized Fibers; (b) DSC scans of fiber samples stabilized at different temperatures and time. (1) Precursor, (2) 150℃ and 30 min, (3) 160℃ and 45 min, (4) 170℃ and 60 min; (c) DSC scans for differences between highly oriented polyethylene and partially drawn polyethylene. (1) Highly oriented polyethylene, (2) partially drawn polyethylene, (3) HOPE stabilized at 150℃ for 60 min, (4) PDPE stabilized at 150℃ for 30 min; (d) TGA scans (in nitrogen) of’ fiber samples stabilized at different temperatures and time. (1) Precursor, (2) 150℃ and 30 min, (3) 160℃ and 45 min, (4) 170℃ and 60 min; (e) tensile properties of resultant carbon fibers; (f) SEM photographs of resultant carbon fibers from a) insufficient stabilization and b) sufficient stabilization; (g) X-ray diffraction photographs of fiber samples. a) precursor, b) partially stabilized.
  • [Fig. 22.] Mechanical properties of amorphous carbon fibers from linear low density polyethylene, due to diameter [48]: (a) DSC curves of the cross-linked LDPE fibers treated by sulfuric acid with different temperatures. A heating B and cooling scan; (b) TGA curves of the cross-linked LDPE fibers treated by sulfuric acid with different temperatures; (c) SEM image of the cross-linked LDPE fibers treated by sulfuric acid: A As-received, B cross-linked LDPE fibers, C carbonized LDPE fiber; (d) TGA curve parameters of the cross-linked LDPE treated by sulfuric acid with different temperatures.
    Mechanical properties of amorphous carbon fibers from linear low density polyethylene, due to diameter [48]: (a) DSC curves of the cross-linked LDPE fibers treated by sulfuric acid with different temperatures. A heating B and cooling scan; (b) TGA curves of the cross-linked LDPE fibers treated by sulfuric acid with different temperatures; (c) SEM image of the cross-linked LDPE fibers treated by sulfuric acid: A As-received, B cross-linked LDPE fibers, C carbonized LDPE fiber; (d) TGA curve parameters of the cross-linked LDPE treated by sulfuric acid with different temperatures.