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Papers by Horst-Christian Langowski

Journal of Adhesion Science and Technology, 1997

In a roll-to-roll vacuum coater, homopolymer and copolymer biaxially oriented polypropylene films... more In a roll-to-roll vacuum coater, homopolymer and copolymer biaxially oriented polypropylene films (BOPP HOMO and BOPP P/E COPO) were pretreated by a microwave-powered oxygen plasma. A plasma monitor and a Langmuir probe were used to analyze the plasma parameters, i.e. the composition of neutral and positive ions, and floating and plasma potential. With this set-up, surface overtreatment, i.e. destruction of the polymer surface, was also detected in situ. Atomic force microscope (AFM), X-ray photoelectron spectroscopy (XPS), and polar surface energy measurements characterized the surface before and after the pretreatment. The BOPP samples, poly(vinyl chloride) (PVC), and poly(ethyleneterephthalate) (PET) were coated with thin aluminum, aluminum oxide, and silicon monoxide layers by an electron beam evaporator. It is shown that the commonly used rule of thumb - a higher polar surface energy of a polymer results in better adhesion of a thin layer coated onto this surface- fails in some cases. High adhesion o...

Polymers, Jun 21, 2023

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Applied physics, Apr 1, 1992

By exposure to low fluence UV laser radiation, the optical absorption coefficient of subsurface p... more By exposure to low fluence UV laser radiation, the optical absorption coefficient of subsurface polymer material can be increased ("incubation") with spatial control, using a suitable contact mask, proper imaging of the mask, or laser direct writing. Spatially selective ablation of polymethylmethacrylate (PMMA) is then achieved with large area XeC1 excimer laser pulses at 308 nm. In this way, the transfer of spatial information to the material can be decoupled from the high laser fluence removal ("ablation") step. The advantages are: The mask is exposed to only low fluence laser radiation-damage is avoided. Since the mask can be removed before the ablation step, mask contamination by the ablated plume cannot occur. Using this incubation/ablation method, PMMA surfaces can be patterned (248 nm/308 nm) with submicrometer spatial control and edge contrasts better than 0.2 gm. This has impact on optical storage technology and laser surface processing techniques in general. The smallest single structure obtained was somewhat smaller than 0.5 gm in diameter up to now, given by the mask.

Brazilian Journal of Medical and Biological Research, Aug 1, 2005

Little is known about the barrier properties of polymer films during high pressure processing of ... more Little is known about the barrier properties of polymer films during high pressure processing of prepackaged foods. In order to learn more about this, we examined the influence of high hydrostatic pressure on the permeation of raspberry ketone (dissolved in ethanol/water) through polyamide-6 films at temperatures between 20 and 60ºC. Permeation was lowered by increasing pressure at all temperatures. At 23°C, the increasing pressure sequence 0.1, 50, 100, 150, and 200 MPa correlated with the decreasing permeation coefficients P/(10 9 cm 2 s-1) of 6.2, 3.8, 3.0, 2.2, and 1.6. Analysis of the permeation kinetics indicated that this effect was due to a reduced diffusion coefficient. Pressure and temperature acted antagonistically to each other. The decrease in permeation at 200 MPa was compensated for by a temperature increase of 20ºC. After release of pressure, the former permeation coefficients were recovered, which suggests that this 'pressure effect' is reversible. Taken together, our data revealed no detrimental effects of high hydrostatic pressure on the barrier properties of polymer films.

Food Packaging and Shelf Life, Apr 1, 2023

Springer series in surface sciences, 1990

Desorption of NO from multilayer systems condensed on NaC1(100) as well as on C-films evaporated ... more Desorption of NO from multilayer systems condensed on NaC1(100) as well as on C-films evaporated onto NaCl(100) was induced by resonant excitation of the symmetric stretch vibration υ1 of the NO cis-dimer with the frequency doubled radiation of a CO2 laser. On C-film-NaC1(100), additional non-resonant desorption was observed at lower condensate coverages (≈16 monolayers). Translational temperatures as derived from the time-of-flight distributions of the desorbed NO monomers are higher than or equal to the calculated maxima of the laser-induced surface temperatures. State-selective detection of desorbed NO molecules by resonance enhanced multi-photon ionization (REMPI) indicates rotational temperatures of 190 ± 20 K at corresponding desorbate translational temperatures of 120 K.

Chemie Ingenieur Technik, Jul 1, 2002

Food Packaging and Shelf Life, 2022

European Food Research and Technology, 2019

The accumulation of unwanted deposits in food-processing equipment may cause significant producti... more The accumulation of unwanted deposits in food-processing equipment may cause significant production downtime, add to expenses for cleaning agents and wastewater disposal, as well as food contamination. Nuclear magnetic resonance (NMR) is considered as a promising non-invasive tool for the monitoring of processes in food industry. In this work, two deposit models and cleaning agents are investigated by low-field 1 H NMR: (1) Paenibacillus polymyxa biofilm, (2) dairy biofouling and (3) clean-in-place (CIP) cleaning agents. The transverse relaxation times T 2 obtained by inverse Laplace transform as well as diffusion coefficients D S of the samples are studied. The obtained results reveal that low-field NMR can be used for the detection and identification of selected deposit models and CIP-cleaning agents. Transverse relaxation times T 2 demonstrate characteristic relaxation behavior of flexible tubing, differently structured deposits, and liquid phases. Moreover, with increasing biofouling thickness (up to 406.2 mg/cm 2), transverse relaxation times T 2 shift toward slower relaxation rates up to T 2 111.9 ms. In addition, significant differences in the diffusion behavior of water are noted in each sample group of the deposit models and CIP-cleaning agents. The diffusion coefficient of water in dairy biofouling and in microbial biofilm matrix corresponds to approximately 65% and 75% of the value in pure water, respectively. In addition to the NMR results, the biofilm and biofouling identification is validated through microbiological methods and by microscope images.

Food Packaging and Shelf Life

Chemie Ingenieur Technik, 2007

Foods 2021, Oct 14, 2021