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Nanoindentation (NI) is a contact method to investigate localized micromechanical properties of materials, whereby NI of semi-crystalline polymers is challenging. The influence of morphological str...

This work covers a lifecycle assessment of monolayer and multilayer films to quantify the environmental impacts of changing the management of plastic film waste. This lifecycle assessment offers the possibility of quantifying the environmental impacts of processes along the lifecycle of monolayer and multilayer films and mapping deviating impacts due to changed process parameters. Based on the status quo, the changes in global warming potential and abiotic fossil resource depletion were calculated in different scenarios. The changes included collecting, sorting, and recycling mono- and multilayer films. The “Functional Unit” under consideration comprised 1000 kg of plastic film waste, generated as post-consumer waste in Austria and captured in the lightweight packaging collection system. The results showed the reduction of environmental impacts over product lifecycles by improving waste management and creating a circular economy. Recycling all plastic film reduced global warming potential by 90% and abiotic fossil resource consumption by 93%. The necessary optimisation steps to meet the politically required recycling rates by 2025 and 2030 could be estimated, and the caused environmental impacts are presented. This work shows the need for increased collection, recycling, and significant improvement in the sorting of films to minimise global warming potential and resource consumption.

The main focus of this work is to investigate the degradation behavior of two newly developed encapsulants for photovoltaic applications (thermoplastic polyolefin (TPO) and polyolefin elastomer (POE)), compared to the most widely used Ethylene Vinyl Acetate (EVA) upon exposure to two different artificial ageing tests (with and without ultraviolet (UV) irradiation). Additive composition, optical and thermal properties and chemical structure (investigated by means of Thermal Desorption Gas Chromatography coupled to Mass Spectrometry, UV-Visible-Near Infrared spectroscopy, Differential Scanning Calorimetry, Thermogravimetric Analysis and Fourier Transform-Infrared spectroscopy, respectively) of the analyzed polymers were monitored throughout the exposure to artificial ageing tests. Relevant signs of photo-oxidation were detectable for TPO after the UV test, as well as a depletion of material&rsquo, s stabilizers. Signs of degradation for EVA and POE were detected when the UV dose applied was equal to 200 kW h m&minus, 2. A novel approach is presented to derive information of oxidation induction time/dose from thermogravimetric measurements that correlate well with results obtained by using oxidation indices.

Instrumented nanoindentation (NI) was used to examine the viscoelastic properties of poly(methyl methacrylate) (PMMA) as an amorphous polymer model. An evaluation combining adhesive contact and empiric spring–dashpot models has been applied to obtain the instantaneous elastic modulus E 0 and the infinitely elastic modulus E ∞ from nanoindentation creep curves. The value of E 0 has been compared to moduli obtained with atomic force microscopy-based nanoindentation (AFM-NI) and compression tests. Furthermore, the elastic modulus has been evaluated by the method introduced by Oliver and Pharr ( O & P ) for the NI and AFM-NI results. Comparison of the elastic modulus E 0 from the creep measurements of NI and AFM-NI to compression tests reveals good agreement of the results. However, only the O & P based AFM-NI results yield to lower values.

To contribute to the targeted 10 million tons per year of recycled plastic in Europe by 2025 and to improve the mechanical sorting degree of polyethylene (PE) products, density prediction models were developed from Fourier transform infrared-attenuated total reflectance (FTIR-ATR) and Raman spectroscopic data. State-of-the-art sorting in mechanical recycling provides separated polymer classes, however an improved classification with specific chemical and physical features such as density or melt flow rate has not been developed yet. Applying multivariate data analysis (MVDA) on the spectral datasets of 10 different PE materials, one FTIR-ATR and two Raman spectra based partial least square (PLS) density models were developed. However, whereas all three models are applicable to predict PE density accurately, the Raman models have shown some advantages. Firstly, less principle components (PC) are needed and secondly the density can be assessed with higher accuracy, due to the more robust cross-validated PLS model. Moreover, the obtained PC-s indicate that in the FTIR-ATR model the CH3/CH2 ratio, while in the Raman model the CH2, CH and the crystalline C–C bands can be correlated with the PE density. The most accurate PLS model was obtained from the 1500-1000 cm−1 Raman shift region. The developed models could improve the density based mechanical separation of PE and consequently increase the quality of recycled and reprocessed PE products.

Acetic acid, which is formed during degradation of the most frequently used photovoltaic (PV) encapsulant ethylene vinyl acetate (EVA), is linked to several PV module failure mechanisms like corrosion of interconnectors, cells or potential induced degradation (PID). An evaluation of a new measurement technique and data analysis for acetic acid permeation through photovoltaic backsheet films is described. The influence of the layer composition of the multilayer backsheets on the acetic acid permeation rates (AATR) was determined by investigating the permeation properties of the individual layers as well as the whole polymeric multilayer composites. Various polymeric backsheet types based on PET-core layers showing a very high barrier for acetic acid permeation were compared to fully polyamide material stacks which allow for a much higher transmission of acetic acid through the backsheet out of the module. Incorporated Al-layers were found to not affect the AATRs of PET based backsheets.

The purpose of this work was the investigation of the influence of the microclimate on the ageing behavior of polymeric encapsulants for photovoltaic (PV) modules. Different types of encapsulation films were investigated. Single film and laminated samples were artificially aged under different conditions (with and without irradiation). The results showed that there is a strong influence of the microclimate on the aging behavior of polymeric encapsulant materials on the optical, chemical and morphological properties of the materials. Differences were even detectable in the unaged state between film and module samples after the production process. Not only has the sample set-up (film or laminated module sample) highly influenced the degradation of the encapsulants, but also the type of aging (dark aging or aging with irradiation).

This paper describes the development of a novel high-performance thermoset based on epoxidized linseed oil and pure crystalline citric acid (CA). Fully bio-based polymer networks are generated and CA is shown to be a very efficient hardener for epoxidized plant oils. Comprehensive processing-structure-property relationships are established and optimum curing parameters are derived. The thermoset's polymer physical property profile (incl. high stiffness and strength) reveals its great potential to substitute petrochemical based resins.

The weathering stability of polymeric backsheets is very important for the reliability of photovoltaic (PV) modules. In addition to reliability, cost reduction and sustainability are upcoming challenges the PV backsheet industry is facing with. The most commonly used material for PV backsheets is poly(ethylene-terephthalate)-PET. However, PET is in general very sensitive to hydrolysis, which leads to chain scission and causes embrittlement, cracking, delamination, and dimensional instability of the backsheet. Compared to that newly developed modified polyolefin backsheets have favorable selective permeation properties and high mechanical flexibility, which could be key properties for backsheets in terms of higher PV module reliability. In this work, the weathering stability of PET/fluoropolymer backsheet and an alternative coextruded polyolefin-backsheet was investigated in terms of thermal and mechanical stability. Both materials were artificially aged and the changes caused by aging were investigated. The polyester-based backsheet showed embrittlement and reduced elongation at break for 70%. The polyolefin-based backsheet retained its mechanical flexibility even after 2000 h of aging under damp-heat conditions, with no significant physical or chemical aging processes occurring. The comparison of the results of both backsheets suggests that the polyolefin backsheet is a promising candidate for the reduction of cracks and delamination in the field

This work reports on the prospects of using luminescence spectroscopy as a non-destructive method for the characterization of ethylene vinyl acetate copolymer (EVA) crosslinking in photovoltaic (PV) modules. Luminescence has the potential to be easily applied in-line for monitoring purposes, e.g. during manufacturing. We investigate the correlation of luminescence, Raman spectroscopy and differential scanning calorimetry with the EVA crosslinking. We show that all these methods, including the luminescence method, show a good correlation with the hold time during the lamination process. Furthermore, time-dependent luminescence measurements are introduced. These make use of the fact that the luminescence decreases upon the ultraviolet irradiation during the measurement. In contrast to steady-state luminescence, this facilitates measurements that are inherently less dependent on possible interfering signal artifacts, as these may occur in industrial PV modules due to other components of the PV module.

The object of this paper is to determine the thermal expansion behavior of nine different encapsulants in order to identify possible deficiencies in production processes and allow for the optimization of the process parameters. High dimensional stability of the encapsulant is of great importance in photovoltaic (PV) module production to avoid problems during lamination and/or in application. For this purpose, the samples were heated twice in a thermo-mechanical analyzer (TMA) in tensile mode, and the coefficient of thermal expansion (CTE) over temperature was evaluated. To get additional information about transition temperatures of the encapsulants, differential scanning calorimetry (DSC) measurements were made. The TMA results for most samples showed anisotropic behavior which was eliminated after the first heating run. Three samples showed shrinkage with subsequent increased thermal expansion as well as anisotropic behavior. It could be shown that knowing the thermal expansion behavior of the solar cell encapsulants is highly relevant for the PV module lamination process, and Thermo-Mechanical Analysis proved to be a suitable method to evaluate and also for quality control of solar cell encapsulation films.

In order to characterize the damping behavior of thin passively constrained layer damping (CLD) loudspeaker membranes, usually the whole loudspeaker has to be built. Therefore, a method was established to characterize the damping performance of these membranes with thicknesses below 50 μm at the film level using dynamic mechanical analysis (DMA). Since in the CLD design damping is provided via shear deformation of the middle damping layer, a test was set up to determine the mechanical loss factor tan δ (f,T) in DMA shear mode. Subsequently, results from 1-200 Hz were extrapolated to application-relevant frequencies of up to 1000 Hz via time-temperature superposition. Finally, the damping behavior was rated by the frequency dependent integrated average of the mechanical loss factor t A ¯ . Furthermore, in experiments with different constraining and damping layers, it was found that the damping performance was maintained as long as the adhesion between them was sufficiently strong.

In this paper, two methods for the determination of infrared optical properties of thick polymer films, based on FTIR spectroscopy, were implemented and used. Complex index of refraction data were generated for various ethylene copolymer films. Transmittance and reflectance spectra were measured in the mid infrared range using a gold-coated 100 mm-diameter integrating sphere. For the investigated films n and k values ranging from 1.3 to 1.6 and from 10 -4 to 0.25 were determined, respectively. Regarding n, a good agreement was obtained for both methods, the transmittance/reflectance procedure (T/R method) used for transparent and semitransparent regions, and Single Substractive Kramers-Kronig (SSKK) algorithm applied for non-transparent regions. The highest k values were determined for the CH 2 stretching vibration. The k values are dependent on comonomer content and film thickness. The combination of both methods allows for an accurate determination of n and k in the entire IR region relevant for solar application.

In reliability testing of components for PV modules an always remaining question is about material (in)compatibilities and synergistic effects and thus, how results of singly tested materials correlate with materials aged within PV modules. Testing of sin- gle materials would simplify sample preparation, reduce costs and offer more testing options. Therefore the main objective of this study was to compare the aging behavior of single backsheets with that of backsheets incorporated within PV modules. Four different types of backsheets were chosen, all of them comprising of polyethylene terephthalate (PET) core layers, but differing outer protection layers. Test modules using identical components, varying only in the type of backsheet used were produced and damp heat aged (85C/85% RH 2000 h). The results revealed no influence of the PV module lamination on the thermal characteristics of the poly- meric backsheets. Even after DH aging, differences between single and module laminated backsheets were negligible. Degradation effects of PET could be detected for all aged sheets by thermal analysis and were confirmed by tensile tests and rheological measure- ments. Thus, it can be stated that testing of single PET based backsheets under DH aging conditions is a practicable way to investi- gate the applicability of a new backsheet. V C 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42093.

The power degradation and failure of photovoltaic (PV) modules can be caused by changes in the mechanical properties of the polymeric components during the module lifetime. This paper introduces instrumented nanoindentation as a method to investigate the mechanical properties of module materials such as polymeric encapsulants. To this end, nanoindentation tests were carried out on ethylene vinyl acetate (EVA) surfaces, which have been separated from the glass panel. Two types of time-dependent indentation cycle modes, the time domain (creep mode) and frequency domain (dynamic mode) were performed to determine the viscoelastic behavior. For each mode, a corresponding model was applied to calculate the main mechanical properties. The general capability of nanoindentation as cross-linking determination method is investigated with the methodological advantages over bulk mechanical characterization methods. A large number of Glass/EVA/Backsheet laminates were built using different lamination conditions resulting in different degrees of curing. Both indentation modes indicate good modulus sensitivity for following the EVA crosslinking in its early stages but could not reliably differentiate between samples with higher EVA branching. Additional dynamic mechanical analysis (DMA) characterization was used as an established method to validate the indentation measurements. Both nanoindentation and DMA tensile mode produce similar quantitative viscoelastic responses, in the form of the damping factor parameter, demonstrated for three different frequencies at room temperature. A statistical study of the data reveals the advantages for the investigation of multilayer PV laminates by using nanoindenation as a surface method while also being applicable to field aged modules.