Hygroexpansion and Surface Roughness Cause Defects and Increase the Electrical Resistivity of Physical Vapor Deposited Aluminum Coatings on Paper

Lindner, Martina; Heider, Julia; Reinelt, M.; Langowski, Horst‐Christian

doi:10.3390/coatings9010033

Cited by 3 publications

(2 citation statements)

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“…For 90% relative humidity, the dimensional change is 1.5 times the size of the change at 10% relative humidity. The almost linear relation to the relative humidity was also observed by other researchers [34][35][36]. The coated material shows about the same dimensional change in MD and 5%-22% more in CD compared to the raw material.…”

Section: Hygroexpansionsupporting

confidence: 82%

Influence of Moisture, Temperature and Bleaching on the Mechanical Properties of Coated Fiber-Based Substrates

2022

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Substrates from fibrous materials are widely used in packaging applications and are produced in high quantities on roll-to-roll production lines. The anisotropic material behavior presents a demanding situation for the process control of the converting step. In this work, the influence of moisture and temperature on the mechanical properties of coated and uncoated fiber-based substrates and the influence of other material properties were investigated. The change of moisture content in relation to the surrounding temperature and relative humidity was investigated for different products. The hygroexpansion in dependence of the humidity is measured in machine and cross direction. The changes in the mechanical properties of the different materials due to changes in moisture content were investigated by tensile testing. The material behavior was highly responsive to the surrounding humidity and, thus, the material’s moisture content. A relative humidity between 60% and 70% showed the influence on the material properties most clearly. The presented work showed an influence of the coating on the moisture content for higher grammages. The effect of bleaching was also investigated. Bleaching decreases the potential for moisture absorption and, therefore, influences the moisture content and properties such as hygroexpansion. Coatings influence the hygroexpansion in an anisotropic manner. Coating and bleaching also influence the tensile properties of fiber-based materials. This article is an expanded version of a talk given at the 14th European Coating Symposium, 6–9 September 2021, Brussels, Belgium.

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Section: Hygroexpansionsupporting

confidence: 82%

Influence of Moisture, Temperature and Bleaching on the Mechanical Properties of Coated Fiber-Based Substrates

2022

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“…[15][16][17] Although both the substrate and the coating are of different nature, this work demonstrates the sensitivity of thin coatings to strain. Lindner et al 18,19 demonstrated that hygroexpansive strains induce defects in vacuum-deposited aluminium coatings by monitoring the surface electrical resistivity of metallized papers showing an increase in the resistivity linked to the creation of defects upon application of high levels of RH. The authors further showed that upon reconditioning of the paper to lower humidity, the resistivity increase was not fully recovered suggesting the irreversible damage of the metallic coating.…”

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confidence: 99%

Understanding barrier degradation during water vapour transmission rate testing of high barrier metallized paper

et al. 2021

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Single use packaging is one of the major contributors to environmental issues linked to waste in the environment. Packaging materials often consist of several plastics, which, when combined, are difficult to recycle. One option to reduce these issues are packaging materials for which recycling infrastructure and end markets exist, such as paper. Use of paper in food packaging applications is limited due to poor barrier properties. Enhancing barrier properties without impacting recyclability can be achieved by thin polymeric coatings combined with vapour-deposited aluminium. Water vapour transmission rate (WVTR) of packaging materials is often assessed at 38 C and 90% relative humidity (RH). These conditions, not experienced in the supply chain, may not be optimal for paper as they have the potential to alter the structure of paper by inducing expansion disrupting barrier. This study aims at verifying this hypothesis by evaluating the influence of temperature and RH on the measured WVTR of high barrier paper. Results show that testing such papers at 38 C and 90% RH yields WVTR approximately 10 times higher than when tested at 23 C and 85% RH. The link between this increase and the disruption of the barrier layer is demonstrated by testing samples preconditioned at 38 C and 90% RH and tested at 23 C and 85% RH, depicting an increased WVTR as well. Results suggest that integrity of barrier layer in paper was disrupted at 38 C and 90% RH, and hence, these conditions are deemed inappropriate for testing barrier performance of paper materials.

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Hygroexpansion, Surface Roughness and Porosity Affect the Electrical Resistance of EVOH-Aluminum- Coated Paper

et al. 2019

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When aluminum is applied to paper by physical vapor deposition, substrate roughness contributes to the defect density and hygroexpansion can cause defects that impair the aluminum coating. Both effects can manifest as an increase in electrical resistance. We quantified the effect of substrate paper hygroexpansion (0–95% relative humidity) and paper surface roughness on the effective resistivity (ρEFF) of aluminum coatings. To create different degrees of roughness, five different papers were used. Each of them had one pigment coated side and one side without pigment coating. These different rough paper surfaces were pre-coated with ethylene vinyl alcohol co-polymer (EVOH). Hygroexpansion was promoted by pre-coating and increased more when the coating was applied on rough and porous surfaces. Simultaneously, the pre-coating reduced surface roughness; especially porosity. The reduction of porosity decreased effective resistivity (ρEFF). Based on these results, an aluminum thickness of ≥35 nm is recommended to ensure maximum mechanical stability during hygroexpansion in combination with minimum material usage. Moreover, the resistivity did not regain its initial value when the paper substrate shrank during re-drying.

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Hygroexpansion and Surface Roughness Cause Defects and Increase the Electrical Resistivity of Physical Vapor Deposited Aluminum Coatings on Paper

Cited by 3 publications

References 35 publications

Influence of Moisture, Temperature and Bleaching on the Mechanical Properties of Coated Fiber-Based Substrates

Influence of Moisture, Temperature and Bleaching on the Mechanical Properties of Coated Fiber-Based Substrates

Understanding barrier degradation during water vapour transmission rate testing of high barrier metallized paper

Hygroexpansion, Surface Roughness and Porosity Affect the Electrical Resistance of EVOH-Aluminum- Coated Paper

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