TY  - GEN
A1  - Wang, Jingwen
A1  - Rychkov, Dmitry
A1  - Gerhard, Reimund
T1  - Influence of Charge Density on Charge Decay in Chemically Modified Polypropylene Films
T2  - 2018 IEEE 2nd International Conference on Dielectrics (ICD)
N2  - Previous work has shown that surface modification with orthophosphoric acid can significantly enhance the charge stability on polypropylene (PP) surface by generating deeper traps. In the present study, thermally stimulated potential-decay measurements revealed that the chemical treatment may also significantly increase the number of available trapping sites on the surface. Thus, as a consequence, the so-called "cross-over" phenomenon, which is observed on as-received and thermally treated PP electrets, may be overcome in a certain range of initial charge densities. Furthermore, the discharge behavior of chemically modified samples indicates that charges can be injected from the treated surface into the bulk, and/or charges of opposite polarity can be pulled from the rear electrode into the bulk at elevated temperatures and at the high electric fields that are caused by the deposited charges. In the bulk, a lack of deep traps causes rapid charge decay already in the temperature range around 95 degrees C.
KW  - polypropylene
KW  - surface charge stability
KW  - thermally stimulated discharge
KW  - cross-over effect
KW  - chemical modification
Y1  - 2018
SN  - 978-1-5386-6389-9
U6  - https://doi.org/10.1109/ICD.2018.8514718
PB  - IEEE
CY  - New York
ER  - 
TY  - JOUR
A1  - Rychkov, Dmitry
A1  - Gerhard, Reimund
A1  - Kuznetsov, Alexey
A1  - Rychkov, Andrey
T1  - Influence of charge density on the trap energy spectrum in fluoroethylenepropylene copolymer films with chemically modified surfaces
JF  - IEEE transactions on dielectrics and electrical insulation
N2  - Tetrafluoroethylene-hexafluoropropylene copolymer (FEP) films were treated with titanium-tetrachloride vapor by means of molecular-layer deposition. The treatment leads to considerable improvements of the electret-charge stability on positively charged films. A slight improvement is also observed for negatively charged films. In line with our previous findings, we attribute the improvement in electret properties to the formation of deeper traps on the chemically modified polymer surfaces. Here, we investigate the influence of the charge density on electret stability of FEP films with modified surfaces. Trap-energy spectra obtained from thermally-stimulated-discharge measurements indicate that the charge stability on modified FEP films depends on how the surface traps are populated and on the availability of additional deeper traps.
KW  - Electrets
KW  - chemical modification
KW  - surface treatment
KW  - space-charge stability
KW  - charge-carrier transport
KW  - polytetrafluoroethylene (PTFE)
KW  - fluoroethylenepropylene (FEP) copolymer
Y1  - 2018
U6  - https://doi.org/10.1109/TDEI.2018.007437
SN  - 1070-9878
SN  - 1558-4135
VL  - 25
IS  - 3
SP  - 840
EP  - 844
PB  - Inst. of Electr. and Electronics Engineers
CY  - Piscataway
ER  - 
TY  - JOUR
A1  - Hardy, John G.
A1  - Bertin, Annabelle
A1  - Torres-Rendon, Jose Guillermo
A1  - Leal-Egana, Aldo
A1  - Humenik, Martin
A1  - Bauer, Felix
A1  - Walther, Andreas
A1  - Cölfen, Helmut
A1  - Schlaad, Helmut
A1  - Scheibel, Thomas R.
T1  - Facile photochemical modification of silk protein-based biomaterials
JF  - Macromolecular bioscience
N2  - Silk protein-based materials show promise for application as biomaterials for tissue engineering. The simple and rapid photochemical modification of silk protein-based materials composed of either Bombyx mori silkworm silk or engineered spider silk proteins (eADF4(C16)) is reported. Radicals formed on the silk-based materials initiate the polymerization of monomers (acrylic acid, methacrylic acid, or allylamine) which functionalize the surface of the silk materials with poly(acrylic acid) (PAA), poly(methacrylic acid) (PMAA), or poly(allylamine) (PAAm). To demonstrate potential applications of this type of modification, the polymer-modified silks are mineralized. The PAA- and PMAA-functionalized silks are mineralized with calcium carbonate, whereas the PAAm-functionalized silks are mineralized with silica, both of which provide a coating on the materials that may be useful for bone tissue engineering, which will be the subject of future investigations.
KW  - biomaterials
KW  - chemical modification
KW  - photochemistry
KW  - silkworm silk
KW  - spider silk
Y1  - 2018
U6  - https://doi.org/10.1002/mabi.201800216
SN  - 1616-5187
SN  - 1616-5195
VL  - 18
IS  - 11
PB  - Wiley-VCH
CY  - Weinheim
ER  -