Degradation Of Polymeric Materials Research Articles

Interaction of conductor with polymeric materials (XLPE/EPR) at partial discharges

A novel investigation into the behavior of the interface between an insulating material and a conductor subjected to sinusoidal stimulus is presented. Both copper and aluminum wires are used in the windings of electrical machines and also as power cable conductors. During in-service operation, partial discharges (PD) may be initiated in the insulation systems. The paper presents experimental results showing the interaction of different kinds of conductors and dielectric materials on the mechanism of partial discharges in the insulation system. The dedicated test setup is designed to perform experiments with various electrodes, with special focus on copper. Two kinds of specially prepared insulation samples were tested, ethylene propylene rubber (EPR), cross-linked polyethylene (XLPE). These insulating materials were subjected to a sinusoidal stimulus at predefined time intervals and were exposed to PD action. The paper comprises the results of PD measurements and microstructural observations performed by means of scanning electron microscope (SEM) coupled with energy dispersive analysis (EDS). The morphological and elemental analysis reveals the interaction of conductor on polymeric material degradation. Two zones were distinguished, migration and erosion. The migration of atoms of electrode material into the dielectric substrate due to PD activity was observed.

Orthogonal design study on factors affecting the degradation of polylactic acid fibers of melt electrospinning

AbstractMelt electrospinning is a much simpler and safer method in the production of ultra‐fine fibers compared with solution electrospinning. However, high‐spinning temperature usually leads to serious degradation of polymer materials. In determining factors that affect the relative molecular mass of polylactic acid (PLA) fibers during melt electrospinning, an orthogonal design method was used to examine the influence of melting temperature, spinning distance, and species and content of antioxidants. Results showed that antioxidant content at the present three levels (i.e., 0.1%, 0.3%, and 0.5%) has the most considerable effect on the relative molecular mass of PLA fibers. Error analysis showed that changes in temperature, distance, and antioxidant content influence the experiment's results significantly. All interaction effects were larger than those of the single factor in the experimental results. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Odour perception – A rapid and easy method to detect early degradation of polymers

Human perception of odour is presented as a tool to detect early degradation of polymeric materials. Polyamide 66 (PA66) was selected as model material and subjected to accelerated ageing through thermo-oxidation. After different degradation times, participants smelled at the headspace of jars with aged polymer and scaled their perceived odour intensity. In parallel, conventional analysis by GC–MS and tensile testing was performed to measure the volatile compounds released and accompanying changes in mechanical properties during degradation. Perceived odour intensity correlated with a significant deterioration in mechanical properties and the release profiles of eight degradation products. This relationship was detected at a very early stage of degradation before any significant changes could be observed in thermal and surface properties. Odour perception, thus, constitutes a rapid and convenient method to determine the quality of plastic materials.

高分子材料の光・熱・酸化劣化迅速評価のためのオンライン紫外線照射熱分解GC/MS法の開発と応用

縦型加熱炉熱分解装置を用いる熱分解GC/MSシステムをベースに，Xeランプを光源とするマイクロ紫外線(UV)照射装置を組合せた，オンラインUV照射熱分解GC/MS測定システムを開発し，ポリスチレンやポリカーボネートの光・熱・酸化劣化により生成する揮発劣化生成物をオンラインでGC/MS分析し，劣化挙動を解析することができた．また，耐衝撃性ポリスチレンや塗膜試料について，マイクロUV照射装置による照射後残留物の発生ガス–質量分析を通じて劣化状態を評価した結果，従来の促進劣化試験法などによる結果とよい相関が認められるだけでなく，劣化評価に要する時間を大幅に短縮できることを示した．さらに，ポリ塩化ビニルを試料として，光触媒による有機物の分解反応機構の解析にも本法を応用した．

New C-type Apparatus for Evaluating Environment and Stress Degradation of Polymeric Materials

New C-type Apparatus for Evaluating Environment and Stress Degradation of Polymeric Materials

Molybdenum oxide nanoparticles: preparation, characterization, and application in heterogeneous catalysis

An adduct behaviour of ammonium molybdate tetrahydarte (AMT) with polytetrafluoroethylene (PTFE) resulted in three significant benefits: (a) a much lower degradation temperature (ΔTm, 82 K) of the PTFE in the adduct and a much lower final residual mass (ΔRM, 39%) of the adduct compared to the theoretical prediction, (b) the formation of MoO3 and MoO2 nanoparticles, and (c) the shuttle-shaped MoO2 nanoparticles coated with graphite exhibits superior soft magnetic property. The much earlier degradation suggested that there was a strong mutual effect between AMT and PTFE. The much lower residual mass implied that the intervention of a chemical reaction was responsible for the effect in nitrogen. Actually, Raman spectra revealed that the adducted PTFE was degraded into a graphite structure at this atmosphere, and the presence of the graphite layer led to the reduction of AMT into shuttle-shaped MoO2 nanoparticles at 837 K to a complete extent. Controlled sintering measurements in air indicated that the AMT in the presence of PTFE produced α-MoO3 nanoparticles, instead of MoO2. Further, our results indicated that the MoO3 nanoparticles obtained had a positive response to the heterogeneous catalytic oxidation of thiophene in the presence of hydrogen peroxide. We believe that the present work is not only of relevance for applications in the degradation of polymer materials, but also will attract the attention of many groups studying the preparation and magnetic properties of transition metal oxide nanoparticles and their practical application in heterogeneous catalytic reactions.

β-Glucans and Pentosans and their Degradation Products in Commercial Beers

Several commercial beers have been analyzed for their content of β-glucans, pentosans and their degradation products using high performance liquid chromatography, thin layer chromatography and chemical and enzymic analysis procedures. The beers tested contained high levels of residual high molecular weight pentosan, but much less high molecular weight β-glucan. The beers also contained sizeable levels of oligosaccharides, especially trisaccharides, reflecting the incomplete degradation of polymeric materials in malting and mashing and the inability of yeast to ferment them. There is substantially more β-linked glucosyl material in beer than pentosyl substances, although the higher molecular weight of the latter probably makes it more likely to represent soluble fibre. In respect of fibre claims for the beers examined, even for the beer containing the least pentosan, it seems that less than a litre of the product would afford sufficient material.

Biodegradation of Polymeric Material and Adhesive Properties of Cells of Microorganisms

The chemical composition of cell membranes of microscopic fungi destroying polymeric materials is analyzed. The concentrations of the major chemical components – phospholipids, glycans, and amines – in nine types of fungi are estimated. The measured ratios of these components provide an estimate of the hydrophobic properties of conidia, controlling microorganism adhesion to polymer surface and subsequent degradation of polymeric materials.

Synergistic effect between expandable graphite and ammonium polyphosphate on flame retarded polylactide

Synergistic effect was observed between expandable graphite (EG) and ammonium polyphosphate (APP) on flame retarded polylactide (PLA) in this paper using limiting oxygen index (LOI), thermal gravimetric analysis (TGA), scanning electron microscopy (SEM) and X-ray spectroscopy (XPS) and cone calorimeter tests etc. In the experiments, PLA composites with 15 wt% of APP/EG(1:3) combinations showed a LOI value of 36.5 and V-0 rating in UL-94 tests, greatly improved flame retardant properties from composites with APP or EG alone. Results from TGA and cone calorimeter demonstrated that APP/EG combination could retard the degradation of polymeric materials above the temperature of 520 °C by promoting the formation of a compact char layer. This char layer protects the matrix effectively from heat penetrating inside and prevents its further degradation, resulting in lower weight loss rate and better flame retarded performance.

MQ NMR and SPME Analysis of Nonlinearity in the Degradation of a Filled Silicone Elastomer

Radiation-induced degradation of polymeric materials occurs through numerous, simultaneous, competing chemical reactions. Although degradation is typically found to be linear in adsorbed dose, some silicone materials exhibit nonlinear dose dependence due to dose-dependent dominant degradation pathways. We have characterized the effects of radiative and thermal degradation on a model filled-PDMS system, Sylgard 184 (commonly used in electronic encapsulation and in biomedical applications), using traditional mechanical testing, NMR spectroscopy, and sample headspace analysis using solid-phase microextraction (SPME) followed by gas chromatography/mass spectrometry (GC/MS). The mechanical data and (1)H spin-echo NMR spectra indicated that radiation exposure leads to predominantly cross-linking over the cumulative dose range studied (0-250 kGy) with a rate roughly linear with dose. (1)H multiple-quantum NMR spectroscopy detected a bimodal distribution in the network structure, as expected from the proposed structure of Sylgard 184. The MQ NMR spectra further indicated that the radiation-induced structural changes were not linear in adsorbed dose and that competing chain scission mechanisms made a greater contribution to the overall degradation process in the range of 50-100 kGy (although cross-linking still dominated). The SPME-GC/MS data were analyzed using principal component analysis (PCA), which identified subtle changes in the distributions of degradation products (the cyclic siloxanes and other components of the material) as a function of age that provide insight into the dominant degradation pathways at low and high adsorbed dose.

New Analytical Methods for Evaluating the Degradation of Polymeric Materials

New Analytical Methods for Evaluating the Degradation of Polymeric Materials

Combined kinetic analysis of thermal degradation of polymeric materials under any thermal pathway

Combined kinetic analysis has been applied for the first time to the thermal degradation of polymeric materials. The combined kinetic analysis allows the determination of the kinetic parameters from the simultaneous analysis of a set of experimental curves recorded under any thermal schedule. The method does not make any assumptions about the kinetic model or activation energy and allows analysis even when the process does not follow one of the ideal kinetic models already proposed in the literature. In the present paper the kinetics of the thermal degradation of both polytetrafluoroethylene (PTFE) and polyethylene (PE) have been analysed. It has been concluded, without previous assumptions on the kinetic model, that the thermal degradation of PTFE obeys a first order kinetic law, while the thermal degradation of PE follows a diffusion-controlled kinetic model.

Compostability of Co-Extruded Starch/Poly(Lactic Acid) Polymeric Material Degradation in an Activated Inert Solid Medium

The aim of this work was to estimate the biodegradation of a co-extruded starch/poly(lactic acid) polymeric material using a vermiculite based inert solid medium which could simulate compost medium and enable us to achieve complete carbon balances. At the end of the test the mineralisation rate was compared to those obtained for co-extruded starch/poly(lactic acid) polymeric material degradation in compost. It was shown that the mineralisation rate after 45 days of degradation was similar in activated vermiculite medium to the one in compost. A protocol for both extraction and quantification of the carbon included in the different degradation by-products was proposed and the carbon balance of the polymer degradation was followed during the test with a satisfactory accuracy. As the non-degraded PLA and starch material had been retrieved during the test, the evolution of the glass transition temperature and the molecular weight of PLA could be followed. A two-step degradation mechanism was highlighted in inert solid medium, showing the fundamental role of abiotic reactions for PLA degradation in compost.

Depth profiling of coil coating using step-scan photoacoustic FTIR

Photoacoustic (PA) Fourier Transform Infrared Spectroscopy (FTIR) has been demonstrated to be very useful in the analysis of molecular distribution and/or degradation in polymeric materials in a non-destructive manner. Step-scan (SS) PA FTIR has been found to be especially suitable to depth profile multi-layered polymer coating/laminate systems. In this current study, the capability of SSPA-FTIR in assessing industrial coil coatings was evaluated. Two multi-layered model coil coating samples were prepared, one had a pigmented Polyvinylidene Fluoride (PVdF) top coat and the other had a clear Polyethylene Terephthalate (PET) laminate film on the surface; both were depth profiled by SSPA-FTIR. The signal magnitude and phase angle were used to obtain a modulation frequency and a phase angle resolved depth profile, respectively. The advantages and disadvantages of the technique were also investigated. Optical microscopy was used to determine the true thicknesses of the PET and PVdF layers from the sample cross-sections. The values were compared with those predicted by SSPA-FTIR. It was found that a precise depth profile was only obtained with the PET sample whereas in the high pigmented coating system, the predicted values were smaller than the true PVdF thickness, possibly due to the high thermal diffusivity of the inorganic pigment.

Electrical treeing characteristics in XLPE power cable insulation in frequency range between 20 and 500 Hz

Electrical treeing is one of the main reasons for long term degradation of polymeric materials used in high voltage AC applications. In this paper we report on an investigation of electrical tree growth characteristics in XLPE samples from a commercial XLPE power cable. Electrical trees have been grown over a frequency range from 20 Hz to 500 Hz and images of trees were taken using CCD camera without interrupting the application of voltage. The fractal dimension of electric tree is obtained using a simple box-counting technique. Contrary to our expectation it has been found that the fractal dimension prior to the breakdown shows no significant change when frequency of the applied voltage increases. Instead, the frequency accelerates tree growth rate and reduces the time to breakdown. A new approach for investigating the frequency effect on trees has been devised. In addition to looking into the fractal analysis of tree as a whole, regions of growth are being sectioned to reveal differences in terms of growth rate, accumulated damage and fractal dimension.

ものづくりを支える分析技術 高分子材料の劣化評価法

ものづくりを支える分析技術 高分子材料の劣化評価法

Degradacja materialow polimerowych pochodzenia naturalnego w srodowisku wody morskie

The presented investigations covered environmental degradation of polymer materials (thermoplastic starch, modified cellulose and two types of starch-cellulose composites) in The Baltic Sea at Nordic Wharf of Gdynia harbor. Degradation process was also tested in laboratory conditions in sea water with sodium azide (NaN3, eliminating the microorganisms activity) added. These tests let evaluate the part of chemical hydrolysis in the process of degradation in natural sea environment. During samples' incubation (from 14 to 336 days) the following characteristic parameters of sea water were inspected: temperature, pH, oxygen content, chlorides' content and salinity (Table 1). The progress of environmental degradation of polymeric materials has been evaluated on the basis of weight loss (Fig. 5-7), changes of the surface (Fig. 1-4) as well as changes of the structure of the material, observed microscopically (Fig. 8-10). It was found that in the natural environment of sea water the enzymatic hydrolysis of the tested materials occurred, what was demonstrated by clear erosion of the surface and weight loss. The samples of modified cellulose were more susceptible to attacks of microorganisms living in sea water than the samples of thermoplastic starch. In case of composites more distinct weight changes were observed for material A (film form) than for B one (sheet form) because of large surface development at phase boundary. Their degradation in sea water is of enzymatic character and first the amorphous phase is degraded then the crystalline one.

示差走査熱量計による昇温法と等温法の測定値の精度検討と劣化検出

The initial oxidation temperature, which can be measured by DSC using dynamic temperature ramp method, is an index which can be obtained rapidly and with high sensitivity, for quantification of degradation of polymeric materials. On the other hand, there are isothermal DSC methods specified in regulatory methods, such as ASTM D3895 and JWWA K144, mainly for evaluation of thermal stability of polyolefins. However, one of the disadvantages of these isothermal methods is that their measurement times are long.Here, we have studied the features of both dynamic and isothermal methods, to investigate the usefulness of the methods for determining degradation of polymers. We compared the accuracy of the results using both methods, with four different polymer samples: polypropylene, high-density polyethylene, poly-4-methyl-1-pentene, and chloroprene rubber.By using dynamic method, more accurate results compared with that by isothermal one were obtained. In addition to this, smaller amount of sample was needed for the former method to evaluate the degradation. Furthermore, the dynamic method was more sensitive than other conventional methods used for degradation studies, such as tensile strength test and FT-IR analysis.

Dependence of ultraviolet absorbers' performance on ultraviolet wavelength

So far, ultraviolet absorbers (UVA) have been discussed mainly on the basis of the extinction coefficient ( ɛ), and the light degradation of polymeric materials is explained by photolysis of hydroperoxides and Norrish reactions of ketones. This study focuses on the photo-antioxidant ability as characteristic which UVA must possess for the light stabilization, and examines the dependence of the photo-initiation by oxidation products on UV wavelength range. As a result, it has been made clear that UV rays ranging 290–320 nm trigger photo-oxidation (degradation) by photolysis of hydroperoxides and Norrish reactions of ketones, and α-diketone derived from further oxidation of the ketones, for example, initiates photo-oxidation at a surprisingly higher velocity under UV rays above 350 nm. UV rays in the range of 320–350 nm participate in the photo-initiation by an enone ( C C CO ) structure in addition to the above-mentioned oxidation products, in which the initiation velocity is the medium between the velocities for the above two wavelength ranges. That is to say, the longer the UV rays wavelength range, the faster the photo-initiation velocity. Finally, it is concluded that excellent UVA are judged based on λ max rather than ɛ, and that UVA absorbing longer wavelength UV rays can more control the photo-oxidation.

Study on permeation behavior and chemical degradation of PA66 in acid solution

In many polymers under corrosive liquids, degradation followed after permeation of environmental solution for a long period. The permeation rate of environmental solution, in many cases, is very low in corrosion-resistant polymeric materials. Therefore, the observation of the permeation of environmental solution and degradation of polymeric materials are very difficult in practical application. A simulation of permeation of solution is required in order to understand the permeation behavior of environmental solution and polymer degradation. A detailed analysis of the permeation behavior of solution accompanied by chemical reaction is important to study for improving the lifetime of polymers. Polyamide 66 (PA66) and sulfuric acid solution were used to investigate the quantitative study of permeation of environmental solution and its relation to degradation of polymeric materials. Correlation between diffusion process and degradation of PA66 related to the decrease of weight average molecular weight was defined. The diffusion rate of sulfuric acid solution was found to increase by decreasing weight average molecular weight of PA66 due to the established chain scission by hydrolysis reaction. The permeation of sulfuric acid solution that affected the decomposition reaction was modeled and quantitative evaluation of permeation of sulfuric acid was established.