TY - JOUR A1 - Bismarck, A. A1 - Menner, A. A1 - Kumru, M.E. A1 - Sezai Sarac, A. A1 - Bistritz, Martina A1 - Schulz, Eckhard T1 - Poly(carbazole-co-acrylamide) electrocoated carbon fibers and their adhesion behaviour to an epoxy resin matrix JF - Journal of materials science N2 - The surface properties of original high strength and preoxidized high modulus carbon fibers were altered by electrocopolymerizing acryl amide and carbazole and therefore depositing a copolymer coating onto the fibers. Scanning electron microscopy and zeta-potential measurements confirmed the presence of a rough but dense and continuous electrocoating with a basic surface character. Therefore, lsquogoodrsquo adhesion behavior between the electrocoated carbon fibers and an epoxy resin matrix should be expected. The interfacial adhesion was measured using the single fiber pull-out and single fiber indentation test. It was shown that only lsquointermediatersquo adhesion was present between the carbon fibers and the electrocoating, but superior adhesion between the coating and epoxy resin exists. The single fiber model composites always failed at the fiber/electrocoating interface. However, as shown by using the indentation test, the interfacial adhesion between fibers and electrocoating can be significantly improved if preoxidized fibers are used as substrate for electropolymerization. A very high tensile strength for the electrocoating can be expected as derived from the single fiber pull-out tests. PY - 2002 DO - https://doi.org/10.1023/A:1013749019958 SN - 0022-2461 SN - 1573-4803 VL - 37 IS - 3 SP - 461 EP - 471 PB - Springer Science + Business Media B.V. CY - Norwell, Mass. AN - OPUS4-6844 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bismarck, A. A1 - Pfaffernoschke, M. A1 - Springer, J. A1 - Schulz, Eckhard T1 - Polystyrene-grafted Carbon Fibers: Surface Properties and Adhesion to Polystyrene JF - Journal of thermoplastic composite materials N2 - It is highly desirable to improve attractive interactions between carbon fibers and unreactive thermoplastic matrices to the possible maximum. This could be achieved by a simple grafting process to create a covalently bonded interface or interlayer, which should result in cohesive interactions between the polymer-grafted fibers and the same matrix material, leading to a better adhesion strength in the obtained composite material. Here, we are describing the grafting of styrene onto unmodified and unsized carbon fibers via free-radical bulk polymerization in the presence of fibers. After grafting, the surface properties of the carbon fiber approach those of pure polystyrene which was proven by contact angle and zeta ({zeta}) potential measurements. As indicated by the water contact angle, the carbon fiber surface becomes more hydrophobic. Scanning electron microscopy (SEM) provides evidence of grafted polymer. This simple procedure results in a continuous polystyrene coating. The fiber diameter increases significantly after polymer grafting. The adhesion and fracture behavior between the original and polystyrene-grafted carbon fibers to a polystyrene (VESTYRON®) matrix was characterized using the single-fiber pull-out test. There is a considerable increase in the measurable adhesion, i.e., the interfacial shear strength IFSS, by almost 300% between the grafted fibers and polystyrene as compared to untreated original fibers. Two planes of interfacial failure could be distinguished; first in the fiber coating interface leading to lower interfacial shear strength and second in the PS-matrix-PS-coating interphase resulting in a higher interfacial shear strength. In addition to the improved adhesion, there are also clear differences in the pull-out behavior between the nongrafted and grafted fibers. After the initial debonding process corresponding to the maximal pull-out force is completed, the pull-out force is increasing again. PY - 2005 DO - https://doi.org/10.1177/0892705705049559 SN - 0892-7057 SN - 1530-7980 VL - 18 IS - 4 SP - 307 EP - 331 PB - Sage Publ. CY - London AN - OPUS4-11599 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Safinia, L. A1 - Dantan, Nathalie A1 - Höhse, Marek A1 - Mantalaris, A. A1 - Bismarck, A. T1 - Towards a methodology for the effective surface modification of porous polymer scaffolds JF - Biomaterials N2 - A novel low-pressure radio-frequency plasma treatment protocol was developed to achieve the effective through-thickness surface modification of large porous poly (d,l-lactide) (PDLLA) polymer scaffolds using air or water: ammonia plasma treatments. Polymer films were modified as controls. Scanning electron micrographs and maximum bubble point measurements demonstrated that the PDLLA foams have the high porosity, void fraction and interconnected pores required for use as tissue engineering scaffolds. The polymer surface of the virgin polymer does contain acidic functional groups but is hydrophobic. Following exposure to air or water: ammonia plasma, an increased number of polar functional groups and improved wetting behaviour, i.e. hydrophilicity, of wet surfaces was detected. The number of polar surface functional groups increased (hence the decrease in water contact angles) with increasing exposure time to plasma. The change in surface composition and wettablility of wet polymer constructs was characterised by zeta potential and contact angle measurements. The hydrophobic recovery of the treated PDLLA polymer surfaces was also studied. Storage of the treated polymer constructs in ambient air caused an appreciable hydrophobic recovery, whereas in water only partial hydrophobic recovery occurred. However, in both cases the initial surface characteristics decay as function of time. KW - Scaffold KW - Polyactic acid KW - Plasma KW - Surface modification KW - Contact angle KW - Wettability hydrophilicity PY - 2005 DO - https://doi.org/10.1016/j.biomaterials.2005.05.078 SN - 0142-9612 VL - 26 IS - 36 SP - 7537 EP - 7547 PB - Elsevier CY - Oxford AN - OPUS4-11487 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bismarck, A. A1 - Lee, A.F. A1 - Sarac, A.S. A1 - Schulz, Eckhard A1 - Wilson, K. T1 - Electrocoating of carbon fibres: A route for interface control in carbon fibre reinforced poly methylmethacrylate? JF - Composites science and technology N2 - A simple method of creating defined PMMA and poly (MMA-co-Cz) electrocoatings on carbon fibres is described. The electrodeposition of poly methylmethacrylate (PMMA) onto unsized, unmodified carbon fibres was performed by simple constant current electrolyses of methylmethacrylate (MMA) monomer in dimethylformamide (DMF) solutions and the ‘pure’ liquid monomer using sodium nitrate and lithium perchlorate as supporting electrolytes. The presence of polymeric coatings successfully attached to the carbon fibres was verified by scanning electron microscopy and photoelectron spectroscopy (XPS). Performing the electrolysis in dilute MMA in DMF solutions ([MMA] < 5 M) results in the deposition of powder-like polymer on the carbon fibre electrodes. Increasing the MMA concentration in the DMF solution results in a homogeneous PMMA coating of the carbon fibres. The degree of grafting or coating increases with increasing MMA concentration, except when pure MMA is used without solvent. The adhesive strength between the electrocoated carbon fibres and a PMMA matrix was determined using the single fibre pull-out test. It was found that the interfacial fracture behaviour of all carbon fibre/PMMA model composites is rather brittle. The adhesion strength between the unmodified carbon fibres and the PMMA matrix was equal to the cohesive strength of the polymer matrix itself. Nevertheless, the electrodeposition of thin and homogeneous PMMA coatings resulted in much improved adhesion strengths. KW - Carbon fibres KW - Coating KW - Interfacial strength KW - Fibre - matrix bond KW - Photoelectron spectroscopy (XPS) PY - 2005 DO - https://doi.org/10.1016/j.compscitech.2005.01.006 SN - 0266-3538 VL - 65 IS - 10 SP - 1564 EP - 1573 PB - Elsevier CY - Barking AN - OPUS4-7540 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Ho, K.K.C. A1 - Lamoriniere, S. A1 - Kalinka, Gerhard A1 - Schulz, Eckhard A1 - Bismarck, A. T1 - Interfacial behavior between atmospheric-plasma-fluorinated carbon fibers and poly(vinylidene fluoride) JF - Journal of colloid and interface science N2 - Atmospheric-plasma fluorination was used to introduce fluorine functionalities onto the surface of carbon fibers without affecting their bulk properties. The interfacial adhesion between atmospheric-plasma-fluorinated carbon fibers and poly(vinylidene fluoride) (PVDF) was studied by means of direct wetting measurements and single fiber pullout tests. Measured contact angles of PVDF melt droplets on modified carbon fibers show that short exposure times of carbon fibers to atmospheric-plasma fluorination (corresponding to a degree of surface fluorination of F/C = 0.01 (1.1%)) leads to improved wettability of the fibers by PVDF melts. The apparent interfacial shear strength as a measure of practical adhesion, determined by the single-fiber pullout test, increases by 65% under optimal treatment conditions. The improved practical adhesion is not due to the formation of transcrystalline regions around the fibers or a change of the bulk matrix crystallinity or to an increased surface roughness; it seems to be due to the compatibilization of the interface caused of the atmospheric-plasma fluorination of the carbon fibers. KW - Carbon fibers KW - Fluorination KW - Contact angle KW - Interface KW - Adhesion KW - Surface area KW - Fiber properties PY - 2007 DO - https://doi.org/10.1016/j.jcis.2007.04.076 SN - 0021-9797 SN - 1095-7103 VL - 313 IS - 2 SP - 476 EP - 484 PB - Elsevier CY - Orlando, Fla. AN - OPUS4-16026 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Ho, K.K.C. A1 - Kalinka, Gerhard A1 - Tran, M.Q. A1 - Polyakova, N.V. A1 - Bismarck, A. T1 - Fluorinated carbon fibres and their suitability as reinforcement for fluoropolymers JF - Composites science and technology N2 - The interaction between direct fluorinated carbon fibres and various fluoropolymers (ethylene-chlorotrifluoroethylene, poly vinylidene fluoride, fluorinated ethylene propylene copolymer and tetrafluoroethylene-perfluoro alkoxy vinyl ether copolymer) was studied by means of direct wetting measurements between fibres and the polymer melts and single fibre pull-out tests. The results of both techniques allow the adhesion behaviour between the fibres and the matrices to be predicted. The results obtained show that a low degree of surface fluorination of carbon fibres leads to an improved wettability between the fibres and fluoropolymer melts and this is an indicator for an improved thermodynamic work of adhesion. The apparent interfacial shear strength as measure of practical adhesion, determined by the single fibre pull-out test, increases with increasing degree of surface fluorine content up to a maximum, which depends on the degree of fluorination of the matrix used. The improved interaction between the fibre and the matrix is due to an enhanced compatibility at the fibre/matrix interface. KW - Adhesion KW - A. Carbon fibres KW - B. Debonding KW - B. Interfacial strength PY - 2007 DO - https://doi.org/10.1016/j.compscitech.2007.02.012 SN - 0266-3538 VL - 67 IS - 13 SP - 2699 EP - 2706 PB - Elsevier CY - Barking AN - OPUS4-15814 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Juntaro, J. A1 - Pommet, M. A1 - Kalinka, Gerhard A1 - Mantalaris, A. A1 - Shaffer, M.S.P. A1 - Bismarck, A. T1 - Creating Hierarchical Structures in Renewable Composites by Attaching Bacterial Cellulose onto Sisal Fibers JF - Advanced materials KW - Nanotubes KW - Cellulose KW - Polymer KW - Interface KW - Hierarchical Structures PY - 2008 DO - https://doi.org/10.1002/adma.200703176 SN - 0935-9648 SN - 1521-4095 VL - 20 IS - 16 SP - 3122 EP - 3126 PB - Wiley-VCH Verl. CY - Weinheim AN - OPUS4-18258 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Tran, M.Q. A1 - Ho, K.K.C. A1 - Kalinka, Gerhard A1 - Shaffer, M.S.P. A1 - Bismarck, A. T1 - Carbon fibre reinforced poly(vinylidene fluoride): Impact of matrix modification on fibre/polymer adhesion JF - Composites science and technology N2 - The quality of interfacial interaction is dictated by the surface chemistry of the carbon fibres and the composition of the matrix. The composition of poly(vinylidene fluoride) (PVDF) was modified by the addition of maleic anhydride grafted PVDF. The surface properties of the various matrix formulations were characterised by contact angle and electrokinetic measurements. Carbon fibres were modified by industrial electrochemical oxidation and oxidation in nitric acid, or the use of a traditional epoxy-sizing of industrially oxidised fibres. The surface composition, morphology and wetting behaviour of the carbon fibres was characterised. The interaction between modified PVDF and the carbon fibres was studied by direct contact angle measurements between PVDF melt on single carbon fibres and by single fibre pull-out tests. The best wetting and adhesion behaviour was achieved between PVDF containing 5 ppm grafted maleic anhydride (MAH) and epoxy-sized carbon fibres. The addition of MAH-grafted PVDF to the unmodified PVDF caused the apparent interfacial shear strength to increase by 184%. The apparent interfacial shear strength of this fibre–matrix combination allowed for the utilisation of 100% of the yield tensile strength of PVDF. KW - A. Carbon fibres KW - A. Coupling agents KW - B. Interface KW - B. Adhesion KW - Wetting PY - 2008 DO - https://doi.org/10.1016/j.compscitech.2008.02.021 SN - 0266-3538 VL - 68 IS - 7-8 SP - 1766 EP - 1776 PB - Elsevier CY - Barking AN - OPUS4-18259 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Pommet, M. A1 - Juntaro, J. A1 - Heng, J.Y.Y. A1 - Mantalaris, A. A1 - Lee, A.F. A1 - Wilson, K. A1 - Kalinka, Gerhard A1 - Shaffer, M.S.P. A1 - Bismarck, A. T1 - Surface modification of natural fibers using bacteria: depositing bacterial cellulose onto natural fibers to create hierarchical fiber reinforced nanocomposites JF - Biomacromolecules N2 - Triggered biodegradable composites made entirely from renewable resources are urgently sought after to improve material recyclability or be able to divert materials from waste streams. Many biobased polymers and natural fibers usually display poor interfacial adhesion when combined in a composite material. Here we propose a way to modify the surfaces of natural fibers by utilizing bacteria (Acetobacter xylinum) to deposit nanosized bacterial cellulose around natural fibers, which enhances their adhesion to renewable polymers. This paper describes the process of modifying large quantities of natural fibers with bacterial cellulose through their use as substrates for bacteria during fermentation. The modified fibers were characterized by scanning electron microscopy, single fiber tensile tests, X-ray photoelectron spectroscopy, and inverse gas chromatography to determine their surface and mechanical properties. The practical adhesion between the modified fibers and the renewable polymers cellulose acetate butyrate and poly(l-lactic acid) was quantified using the single fiber pullout test. KW - Composires KW - Bacteria KW - Surface KW - Cellulose natural fibers PY - 2008 DO - https://doi.org/10.1021/bm800169g SN - 1525-7797 VL - 9 IS - 6 SP - 1643 EP - 1651 PB - ACS Publ. CY - Washington, DC, USA AN - OPUS4-23162 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Qian, Hui A1 - Bismarck, A. A1 - Greenhalgh, E.S. A1 - Kalinka, Gerhard A1 - Shaffer, M.S.P. T1 - Hierarchical composites reinforced with carbon nanotube grafted fibers: The potential assessed at the single fiber level JF - Chemistry of materials N2 - The feasibility of reinforcing conventional carbon fiber composites by grafting carbon nanotubes (CNTs) onto the fiber surface has been investigated. Carbon nanotubes were grown on carbon fibers using the chemical vapor deposition (CVD) method. Iron was selected as the catalyst and predeposited using the incipient wetness technique before the growth reaction. The morphology of the products was characterized using scanning electron microscopy (SEM), which showed evidence of a uniform coating of CNTs on the fiber surface. Contact angle measurements on individual fibers, before and after the CNT growth, demonstrated a change in wettability that can be linked to a change of the polarity of the modified surface. Model composites based on CNT-grafted carbon fibers/epoxy were fabricated in order to examine apparent interfacial shear strength (IFSS). A dramatic improvement in IFSS over carbon fiber/epoxy composites was observed in the single fiber pull-out tests, but no significant change was shown in the push-out tests. The different IFSS results were provisionally attributed to a change of failure mechanism between the two types of tests, supported by fractographic analysis. KW - Composites KW - Nano tubes KW - Grafting KW - Interface PY - 2008 DO - https://doi.org/10.1021/cm702782j SN - 0897-4756 SN - 1520-5002 VL - 20 IS - 5 SP - 1862 EP - 1869 PB - American Chemical Society CY - Washington, DC AN - OPUS4-34568 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -