TY - JOUR A1 - Mix, Renate A1 - Friedrich, Jörg Florian A1 - Neubert, Dietmar A1 - Inagaki, N. T1 - Response of linear, branched or crosslinked polyethylene structures on the attack of oxygen plasma JF - Plasma chemistry and plasma processing N2 - Linear, branched and crosslinked polyethylenes (PE) were exposed to the low-pressure oxygen plasma for 2–120 s. In the following the samples were washed with solvents to remove low-molecular weight oxidized material and to excavate the subjacent polymer structure for microscopic characterization. X-ray photoelectron spectroscopy (XPS) measurements provided information about changes in elemental composition and chemical structure of PE after plasma exposure and washing. The calculation of the concentration of tertiary C atoms using XPS data was a measure of branches and crosslinking in the polymer before and after exposure to oxygen plasma. Linear PE was most sensitive towards oxygen plasma and showed the highest concentration in tertiary C atoms after plasma exposure. On the other hand branched PE types, which possess originally more tertiary carbon atoms, have lost two-third of them after 2 s oxygen plasma exposure. Branched PE show also topological changes at their surface as detected by atomic force microscopy. Differential scanning calorimetry measurements confirmed strong changes in crystallinity and molecular orientation of linear PE already after 120 s exposure to the oxygen plasma interpreted as amorphization. These effects should be interpreted as result of crosslinking caused by the recombination of dangling bond sites. KW - Linear and branched polyethylene KW - Oxygen plasma KW - Functionalization KW - Crosslinking PY - 2014 UR - http://link.springer.com/article/10.1007%2Fs11090-014-9558-9/fulltext.html DO - https://doi.org/10.1007/s11090-014-9558-9 SN - 0272-4324 VL - 34 IS - 5 SP - 1199 EP - 1218 PB - Plenum Publ. Corp. CY - New York, NY, USA AN - OPUS4-30741 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CHAP A1 - Mix, Renate A1 - Friedrich, Jörg Florian A1 - Inagaki, N. ED - Thomas, M. ED - Mittal, K.L. T1 - Permanence of functional groups at polyolefin surfaces introduced by dielectric barrier discharge pretreatment in presence of aerosols T2 - Atmospheric pressure plasma treatment of polymers N2 - A convenient way to overcome the chemical inertness of polyolefin surfaces is to expose them to the atmospheric air plasma of a dielectric barrier discharge (DBD). To improve the efficiency in formation of polar groups at the polyolefin surface, different liquids such as water and ethanol were sprayed as aerosol into the plasma zone between the powered electrode and the polyolefin surface. Both sprayed liquids as well as the polyolefin surface were simultaneously activated; thus, the formation of different functional groups at the polyolefin surface was realized. The type of aerosol-sprayed additive, exposure time, power etc. have been found to determine the efficiency with respect to introduction of polar groups. KW - PE KW - PP KW - Surface modification KW - Aerosol-assisted DBD PY - 2013 SN - 978-1-118-59621-0 DO - https://doi.org/10.1002/9781118747308.ch4 N1 - Serientitel: Adhesion and Adhesives: Fundamental and applied aspects – Series title: Adhesion and Adhesives: Fundamental and applied aspects IS - Part 1 / Chapter 4 SP - 131 EP - 156 PB - Wiley AN - OPUS4-28657 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Friedrich, Jörg Florian A1 - Mix, Renate T1 - Combination of plasma-chemical and wet-chemical processes - a simple way to optimize interfaces in metal-polymer composites for maximal adhesion T2 - ISPC 21 - 21st International Symposium on Plasma Chemistry N2 - Different surface treatments of polypropylene (PP) were tested to improve the peel strength of aluminium-PP systems. Plasma exposure followed by chemical grafting of spacers with -SiOH endgroups and thin adhesion promoting layers deposited by aerosol-assisted DBD using aqu. solutions of classic polymers were compared. Both methods were effective, however, –SiOH terminated spacers effected no peeling also after ageing. T2 - ISPC 21 - 21st International Symposium on Plasma Chemistry CY - Cairns, QLD, Australia DA - 2013-08-02 KW - Adhesion polypropylene-aluminium KW - Tailored interface structures KW - Aerosol-assisted DBD PY - 2013 UR - http://www.ispc-conference.org/ispcproc/ispc21/ID549.pdf SP - Paper 549, 1 EP - 4 AN - OPUS4-28661 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Fahmy, A. A1 - Mix, Renate A1 - Schönhals, Andreas A1 - Friedrich, Jörg Florian T1 - Structure of plasma-deposited copolymer films prepared from acrylic acid and styrene: Part II variation of the comonomer ratio JF - Plasma processes and polymers N2 - Copolymers of acrylic acid and styrene (AA/S) were prepared by pulsed plasma deposition technique. Their structure–property relationships were studied in dependence on the comonomer ratio. Both, the regularity of the structure and the composition of the thin copolymer films were investigated by bulk-sensitive (dielectric spectroscopy, FTIR, and differential scanning calorimetry) as well as surface-sensitive methods such as X-ray photoelectron spectroscopy (XPS). For an unambiguous identification of the functionality of the deposited films the COOH groups were estimated by derivatization with trifluoroethanol and subsequent XPS measurement as well as by the quantitative analysis of the FTIR data. As a result, the concentration of COOH groups on the surface and in the bulk is increasing with the fraction of AA in precursor mixture in a non-monotonous way but similar to the dependence obtained by conventional free radical polymerization. KW - Acrylic acid-styrene copolymer KW - Bulk properties KW - Dielectric properties KW - Plasma polymerization KW - Surface functionalization PY - 2013 DO - https://doi.org/10.1002/ppap.201200110 SN - 1612-8850 SN - 1612-8869 VL - 10 IS - 9 SP - 750 EP - 760 PB - Wiley-VCH Verl. CY - Weinheim AN - OPUS4-29096 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CHAP A1 - Mix, Renate A1 - Yin, Huajie A1 - Friedrich, Jörg Florian ED - Gutowski, W. ED - Dodiuk, H. T1 - Aerosol-based DBD - A simple way to provide polymers with functional groups for adhesion promotion T2 - Recent advances in adhesion science and technology in honor of Dr. Kash Mittal N2 - Polypropylene (PP) foils were exposed to the plasma of an atmospheric dielectric barrier discharge (DBD) in presence of different aerosols. Pure liquids such as water, ethanol, and 1/1 mixtures ethanol/water (v/v) or aqueous Solutions of acetic acid, poly(acrylic acid), poly(vinyl alcohol), and ethylene glycolpoly(vinyl alcohol) copolymer were introduced into the DBD. Surface composition, the number of functional groups per 100 C atoms, and water contact angles were correlated with the energy density of DBD plasma exposure. The wettability of the treated surfaces was investigated for different storage times. Peel strength of the thermally deposited aluminum layer to modified polymer surfaces revealed that the aerosol introduction strongly improves the adhesion between aluminum and polypropylene. KW - Aerosol-assisted DBD KW - Functional groups KW - Surface modification PY - 2013 SN - 978-90-04-20173-6 SN - 978-90-04-20174-3 SP - Chapter 8, 155 EP - 170 PB - CRC Press AN - OPUS4-30035 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Ramanujam, Maalolan A1 - Mix, Renate A1 - Wagner, M. A1 - Friedrich, Jörg Florian T1 - Effect of Br gassing after Ar plasma treatment of polyolefins JF - Journal of adhesion science and technology N2 - For simulation and acceleration of artificial polymer ageing, polyolefin foils were exposed to low-pressure Ar plasma. Plasma particle bombardment and irradiation induce C–C and C–H bond scissions by σ→σ* excitations on the surface and in near-surface layers. Consequently, radicals are generated. They react by recombination, cross-linking, metastable trapping of the radical site or formation of olefinic double bonds. The long-living and metastable trapped C-radicals as well as double bonds in polyolefins were immediately exposed to bromine vapour without breaking the vacuum after switching-off the plasma. These reactive sites rapidly react with the molecular bromine under formation of C–Br bonds. For 5 min of argon plasma exposure, the elemental concentration of bromine was 13% for polyethylene and 22% Br/C for polypropylene as analysed by X-ray photoelectron spectroscopy. Nevertheless, not all C radical sites have reacted with bromine. Later on, when the polyolefins brought in contact with ambient air, an additional post-plasma reaction of the remaining trapped radicals with oxygen was observed. The oxygen concentrations were lower after bromine gassing, thus repressing partially the post-plasma oxidation in the analysed layer (ca. 6 nm) by radical quenching. Such bromination took place either at the surface or in near-surface layers because the Attenuated Total Reflectance (ATR)-FTIR spectra (sampling depth ca. 2500 nm) did not show significant changes for argon plasma-treated PE foils with and without bromine vapour exposure. Further addition of bromine may also occur on C=C double bonds. KW - Ageing of polyolefins KW - Argon plasma KW - Radical formation KW - Formation of double bonds PY - 2013 DO - https://doi.org/10.1080/01694243.2012.762326 SN - 0169-4243 SN - 1568-5616 VL - 27 IS - 6 SP - 1828 EP - 1839 PB - VNU Science Press CY - Utrecht AN - OPUS4-30572 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Fahmy, A. A1 - Mix, Renate A1 - Schönhals, Andreas A1 - Friedrich, Jörg Florian T1 - Structure of plasma-deposited copolymer films prepared from acrylic acid and styrene: Part I dependence on the duty cycle JF - Plasma processes and polymers N2 - Copolymers of acrylic acid and styrene (AA/S) were prepared by pulsed plasma deposition and their structures were studied in dependence on the duty cycle (DC) for a fixed composition of 1:1. As a result, low values of DC doses preserve the structure of monomers in the plasma deposited polymers while high DC leads to a higher degree of fragmentation and a loss in regular structure. Regarding plasma copolymerisation as a feasible method to finish surfaces with a definite number of functional groups it is necessary to characterize both, the chemical nature and the physical properties of the deposited layer. Therefore, a combination of different methods was employed for the characterization of thin plasma copolymer films (FTIR, dielectric spectroscopy, differential scanning calorimetry, X-ray photoelectron spectroscopy (XPS)). Special attention was paid on the unambiguous identification of COOH groups at the surface after derivatization with trifluoroethanol by XPS and in the volume by FTIR. The glass transition temperature of the copolymer system is lower than that for the both plasma deposited homopolymers and increases with the DC in difference to plasma deposited poly(acrylic acid). The dielectric measurements showed that the plasma deposited films were not thermally stable and underwent an undesired post-plasma chemical reaction. The results obtained by dielectric spectroscopy are discussed in detail in comparison with the data from FTIR and XPS measurements. KW - Plasmapolymerisation KW - Copolymerisation KW - Acrylic acid–styrene copolymer KW - Dynamic mobility KW - Plasma copolymerisation KW - Surface functionalization KW - Thin film properties PY - 2012 DO - https://doi.org/10.1002/ppap.201100117 SN - 1612-8850 SN - 1612-8869 VL - 9 IS - 3 SP - 273 EP - 284 PB - Wiley-VCH Verl. CY - Weinheim AN - OPUS4-25654 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Mix, Renate A1 - Friedrich, Jörg Florian A1 - Inagaki, N. T1 - Modification of branched polyethylene by aerosol-assisted dielectric barrier discharge JF - Plasma processes and polymers N2 - Three polyethylene (PE) types with different branching structures were subjected to air, water and ethanol aerosol-assisted dielectric barrier discharges (DBD) for surface modification. Using the air DBD the incorporated oxygen concentration was found to be independent on the branching of PE in contrast to the introduction of OH groups, which was PE-2 > PE-1 > PE-3. For water-aerosol DBD the succession of OH concentration was in the order of PE-1 > PE-2 > PE-3. Ethanol aerosol-assisted DBD produced the lowest concentration of OH groups also independent on the branching of PE. The chemical nature of introduced oxygen functional groups was inspected by X-ray photoelectron spectroscopy (XPS) and assigned as C–O, >C=O/CHO/O–C–O and O=C–O. KW - PE KW - Surface modification KW - Aerosol-assisted DBD PY - 2012 DO - https://doi.org/10.1002/ppap.201100052 SN - 1612-8850 SN - 1612-8869 VL - 9 IS - 4 SP - 406 EP - 416 PB - Wiley-VCH Verl. CY - Weinheim AN - OPUS4-25748 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Mix, Renate A1 - Hielscher, Stefan A1 - Beck, Uwe A1 - Friedrich, Jörg Florian T1 - Plasma meets chemistry: Combined methods for tailored interface design in metal-polymer composites by selective chemical reactions on plasma modified surfaces JF - Journal of physics / Conference series N2 - The applicability of polymer-metal composites is mainly determined by the durability of the adhesive strength between both components. Aluminium (Al) deposited on polypropylene (PP) exemplifies different options of interface design. By deposition of plasma polymers on PP the effect of the type of the functionality was investigated. Spacer insertion was accomplished to position the functional group away from the topmost surface. A further kind of interface design involved a partial condensation of functional groups. Hydroxyl and carboxyl groups were most effective to improve adhesion in Al-PP systems. Approximately 7-10 carboxyl or 25-27 hydroxyl groups per 100 C atoms were necessary to increase the peel strength up to ~700 N/m. In this range, the failure of the composite propagated along the interface Al-tape (no peeling of the metal). Spacer molecules between surface and functional groups provoked the effect that the number of needed functional groups for maximum adhesion was strongly reduced. Linking of the functional groups resulted in non-peelable Al-PP laminates. Two adhesion tests were applied - the peel test and the centrifuge technology. For PP foils modified with chemically bonded and additionally linked silanol groups (no peeling) an adhesive strength of (2.5 ± 0.2) N/mm² was determined by centrifuge technology. XPS inspection of both fracture surfaces indicated a sub-surface failure in the polymer. T2 - HTPP-12 - 12th High-tech plasma processes conference CY - Bologna, Italy DA - 2012-06-24 KW - Adhesion PP-Al KW - Modified surfaces KW - Interface design PY - 2012 DO - https://doi.org/10.1088/1742-6596/406/1/012004 SN - 1742-6588 SN - 1742-6596 VL - 406 SP - 012004-1 - 012004-11 PB - IOP Publ. CY - Bristol, UK AN - OPUS4-28658 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Ramanujam, Maalolan A1 - Wachtendorf, Volker A1 - Purohit, Purv A1 - Mix, Renate A1 - Schönhals, Andreas A1 - Friedrich, Jörg Florian T1 - A detailed dielectric relaxation spectroscopy study of artificial UV weathered low density polyethylene JF - Thermochimica Acta N2 - Artificial weathering of LDPE under dry conditions (<10% of relative humidity) by UV radiation was monitored by dielectric spectroscopy. For an apolar polymer like LDPE, dielectric study yields information about the change in structure and dynamics of the system. The fluctuations of the polar groups which are generated as a result of photooxidation such as carbonyl groups can be monitored as characteristic relaxation processes like the αc or β mode. The dielectric loss characterized by typical dielectric parameters like the activation energy and dielectric strength are strongly dependent upon changes induced by photooxidation in the amorphous and crystalline domains. This paper discusses in detail how the foil reached its mechanical disintegration. It was found that initial stages of weathering induce chain scission and/or crosslinking in the amorphous domains of the polymer and the motional processes in the crystalline regions are not affected. After this induction period, an increase in the degree of crystallization was observed by employing differential calorimetry. The increasing crystallinity is considered as one of the reasons for embrittlement which finally leads to the complete loss of the structural integrity. KW - Artificial weathering KW - UV radiation KW - Dielectric relaxation KW - LDPE PY - 2012 DO - https://doi.org/10.1016/j.tca.2011.12.003 SN - 0040-6031 SN - 1872-762X VL - 530 SP - 73 EP - 78 PB - Elsevier CY - Amsterdam AN - OPUS4-25547 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -