Accelerated Heat Aging Research Articles

Improving Fire Resistance in E-Vehicles: A Study on MPP-Enhanced S-Glass/Phenolic Hybrid Composites

The automotive industry has benefited greatly from the advancements in fireproof, high-strength fiber-reinforced polymer matrix composites during the last several decades. S-Glass/Phenolic hybrid composites made by hydraulic compression molding are the subject of this investigation into the effects of Melamine Polyphosphate (MPP) on their thermal and fire performance. In addition to studying the morphology of the samples, researchers analyzed the thermal and fire performances of hybrid laminates made with neat laminates and varying compositions of MPP (ranging from 3% to 15% by weight). Tests included UL 94, limiting oxygen index (LOI), and the impacts of accelerated heat ageing on the behavior of the hybrid specimens. The results demonstrated that specimens filled with higher MPP performed better in a fire compared to neat samples. According to the results in UL 94 horizontal burning test and vertical burning test, specimens filled with 12 and 15 wt. % MPP demonstrated a reduced flame spreading rate and fulfilled the V-0 criteria. Simultaneously, the energy absorption capacity of hybrid configurations is severely limited by heat ageing, due to its temperature and duration dependent. The research proved that the suggested S-Glass / Phenolic / Melamine Polyphosphate hybrid composites were suitable for creating environmentally friendly electric vehicle battery housings and fire-resistant automotive parts.

A comprehensive overview of the performance of polyamide 6 in the consolidation of vegetable-tanned leathers

Sometimes, vegetable-tanned leathers in museums, excavations, libraries, and storehouses deteriorate due to unsuitable environmental conditions that affect their properties. Accordingly, leather becomes weak. This study evaluates some mechanical, chemical, and physical characteristics of vegetable-tanned leather treated with polyamide 6 (PA6). The authors prepared new vegetable-tanned leather samples. PA6 at different concentrations was applied to the aged leather samples. The accelerated heat aging was applied on the new sample (reference before aging) and treated samples (aged untreated sample after treatment with PA6). Analytical techniques used were: test of the mechanical properties (tensile strength and elongation), attenuated total reflectance/Fourier Transform Infrared (ATR/FTIR), differential scanning calorimeter (DSC) measurement, contact angle, and pH measurement. The results proved that the accelerated heat aging affected the properties studied, as it reduced in the mechanical properties, pH value, and contact angle. Treating aged leather samples with PA6 improved all the properties studied. The mechanical properties, pH value, and contact angle of the treated and aged treated samples increased compared to the aged- untreated- sample. FTIR and DSC analysis proved the stability of the treated and aged treated samples compared to the aged untreated sample. The concentration of 2 % of PA6 gave the best concentrations used, and it is recommended to treat fragile vegetable-tanned leather.

Antioxidant Activity of Biogenic Cinnamic Acid Derivatives in Polypropylene.

Antioxidants (AOs) from natural resources are an attractive research area, as petroleum-based products can be replaced in polymer stabilization. Therefore, novel esters based on the p-hydroxycinnamic acids p-coumaric acid, ferulic acid and sinapic acid were synthesized and their structure properties relationships were investigated. The structures of the novel bio-based antioxidants were verified using NMR and Fourier-transform infrared (FTIR) spectrometry. The high thermal stability above 280 °C and, therefore, their suitability as potential plastic stabilizers were shown using thermal gravimetric analysis (TGA). The radical scavenging activity of the synthesized esters was evaluated by using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay. Stabilization performance was evaluated in polypropylene (PP) using extended extrusion experiments, oxidation induction time (OIT) measurements and accelerated heat aging. In particular, the sinapic acid derivative provides a processing stability of PP being superior to the commercial state-of-the-art stabilizer octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate.

A critical examination of the shelf life of nitrile rubber O-Rings used in aerospace sealing applications

The shelf life of MS29513-016 nitrile O-Rings was determined by accelerated heat aging from 40 to 85 °C for varying aging times up to 50 weeks. The microhardness, tensile strength and 50% tensile stress all rise as a function of aging time while the elongation at break decreases. The crosslink density by solvent swell followed the development or loss of network chains during the aging process. In this case, the net increase in crosslink density showed a good correlation with the hardness, tensile strength and tensile stress results. Property loss is attributed to the labile nature of the sulfur cure system, the high double bound content of the nitrile rubber and the high level of ester plasticizer in the compound. Activation energies were lower than expected due to the sealed plastic packaging which impeded oxygen migration. Nevertheless, results clearly show that the O-Rings are out-of-specification beyond 7 years of shelf life due to the loss of elasticity (elongation at break < 200%). The nominal 15 year shelf life for nitrile rubber used in aerospace sealing applications according to SAE AS5316 needs to be reconsidered in light of the results.

ACCELERATED HEAT AGING OF BUTYL AND BROMOBUTYL AIRCRAFT INNER TUBES FOR SHELF LIFE DETERMINATION

ABSTRACT Butyl and bromobutyl inner tubes, specified by the Aerospace Standard AS50141 for military aircraft, were thermally aged from 40 to 120 °C for varying lengths of time and then their hardness and mechanical properties were measured. 1H double quantum nuclear magnetic resonance (DQ NMR) was used to elucidate crosslink density and distribution changes. Time–temperature superposition of the aged data coupled with the Arrhenius approach was used to determine an approximate shelf life. High (80–120 °C) and low (40–80 °C) temperature oxidation processes were occurring for both rubbers. Below 80 °C, an increase in crosslink density, hardening, stiffening, and loss of elongation was observed. Plasticizer and volatile loss contributes to compound stiffening. Sulfur crosslink network modifications during thermal aging can explain ultimate property loss and stiffness increase. Diffusion limited oxidation was taking place above 80 °C, with the development of a thin oxidized layer composed of ionic crosslinking that affected both hardness and mechanical properties. For butyl rubber, the hardness rise stabilizes as do the ultimate properties, likely due to the proliferation of chain scission reactions, whereas crosslinking reactions prevailed over chain scission events for bromobutyl rubber. Crosslink density and defect fractions B and C as measured through DQ NMR were in agreement with the physical property testing results. The degree of heterogeneity of the network as perceived visually through DQ NMR regularization increases upon exposure to higher temperatures and longer aging times due to the broadening of the crosslink density distribution. Similar Arrhenius activation energies were calculated for the low and high temperature oxidation process for butyl and bromobutyl rubbers. The projected shelf life for the butyl and bromobutyl inner tubes was 10 and 20 yr, respectively. For the first time, DQ NMR testing results (crosslink density and its distribution, defect level) have been successfully applied to support a shelf life determination.

Evaluation of the efficiency of polyacrylamide and poly(MMA-HEMA) for the consolidation of vegetable-tanned leather artifacts

PurposeThis study aims to evaluate the efficiency of using some polymers at different concentrations in the consolidation of vegetable-tanned leather artifacts.Design/methodology/approachNew vegetable-tanned leather samples were prepared. The consolidants used were polyacrylamide (PAM) and polymethyl methacrylate/hydroxyethyl methacrylate (MMA-HEMA). Accelerated heat aging was applied to the untreated and treated samples. Analytical techniques used were Fourier transform infrared spectroscopy (FTIR), digital microscope, scanning electron microscope (SEM), change of color and mechanical properties.FindingsThe characteristic FTIR bands showed the effect of accelerated heat aging on the molecular structure of the studied samples, but treated and aged treated samples used were better than aged untreated samples. Microscopic investigations (digital and SEM), and mechanical properties proved that 2% was the best concentration for polymers used. The change in the total color difference of the treated and aged treated samples was limited.Originality/valueThis study presents the important results obtained from PAM and poly(MMA-HEMA) used for the consolidation of vegetable-tanned leather artifacts. The best results of the studied polymers can be applied directly to protect historical vegetable-tanned leathers.

Evaluation of MMI/acrylate nanocomposite with hydroxyapatite as a novel paste for gap filling of archaeological bones

• MMT/MMA/EA/HEMA nanocomposite was prepared by in situ microemulsion polymerization. • A novel paste was formed from the prepared nanocomposite and hydroxyapatite. • The artificial accelerated heat ageing was applied to the novel paste. • Different analytical techniques were used for the evaluation of the novel paste. • The novel paste is good and can be applied for gaps filling of archaeological bone. Montmorillonite MMT/ Methyl Methacrylate-Ethyl acrylate-2-hydroxyethyl methacrylate MMA/EA/HEMA terpolymeric nanocomposite was prepared through in-situ microemulsion polymerization. The produced nanocomposite was evaluated with hydroxyapatite, forming a novel paste for the gap filling of archaeological bones. Thermal ageing was used for the evaluation of prepared paste. Characterizations were carried out by FTIR; change of colour, Mechanical properties, SEM, X-Ray Diffraction (XRD), Antifungal activity, Density, porosity, water absorption, and wettability. The prepared MMT/ MMA-EA-HEMA terpolymer nanocomposite was produced in well-defined nanospheres with an average size of 144 nm. The results confirmed that the novel paste was very stable and had a great resistance against thermal ageing. All analysis and investigations proved that the addition of MMT/polymer nanocomposite gave good resistance to the reduction in contact angle, density, and resistance the rise in the porosity and water absorption during ageing. Microbiological studies showed that the novel paste had a good resistance against microorganisms.

Evaluation of Nanolime-Silica Core-Shell for Consolidation of Egyptian Limestone Samples with Application on an Archaeological Object

The most of limestone objects in museums, storehouses and archaeological sites suffered from fragility and weakness which lead to the degradation of these artifacts. The present paper aims to evaluate the use of some nanolime-silica core-shell for consolidation process of these weak limestone artifacts. Two concentrations (5% and 10% w/w) were prepared for consolidating the aged limestone cubic samples. After complete drying, the cubic stones were exposed to the accelerated heat aging. The evaluation of consolidation process for the treated and aged treated samples was performed by some analytical methods such as measurement of physical properties and compressive strength. While, the investigation of surface morphology was carried out by scanning electron microscope (SEM) and measurement of contact angle. The characterization process for the prepared core-shell showed the smoothness and spherical shape of the grains with approximate size of 72 nm. The results of physical properties revealed that the treated samples with 10% of nanolime-silica core-shell gave the lowest porosity (15.57%) and water absorption (6.26%). Additionally, the treated samples with 10% concentration of nanolime-silica core-shell gave the highest values of compressive strength (21.23 Cm2/ Kg) and contact angle (122.78°). Moreover, the investigation using SEM revealed that the smoothness and good penetration for the treated sample with 10% concentration of nanolime-silica core-shell. The results of the present study revealed that the efficiency of consolidation process was maximum using 10% concentration of nanolime-silica core-shell and hence it was applied for consolidation of an archaeological limestone octagonal column, Egypt.

Evaluation of the efficiency of nanoparticles for increasing α-amylase enzyme activity for removing starch stain from paper artifacts

Starch stain is a common stain on paper artifacts. This stain leads to deformation of the surface of the paper and promotes the growth of microbiological deterioration. This study aims to use nanoparticles with an α-amylase enzyme to improve its quality for removing this type of stain from the surface of paper artifacts. Accelerated heat aging was used on starch stain applied on the new paper samples. The α-amylase enzyme was prepared. Silver and gold nanoparticles were biosynthesized by local fungal isolation. The produced silver and gold nanoparticles were characterized by using different techniques of analysis (UV- Visible spectroscopy, Transmission Electron Microscope (TEM), and X-Ray diffraction (XRD) analysis). Different concentrations of Ag-NPs and Au-NPs were added to the α-amylase reaction mixture to enhance its activity for removing starch stains. Some analytical techniques were also used for the evaluation of the efficiency of α-amylase and nanoparticles for removing starch stains (Color measurement, Scanning Electron Microscope (SEM), and pH measurement). The results proved that Ag-NPs at 20 microliters increased the activity to about 160%, whereas Au-NPs enhanced the activity to about 140% at a concentration of 5μL. The results showed that α-amylase enzyme incorporated with Ag-NPs exhibited better results more than its use alone. The addition of Ag-NPs to α-amylase enzyme for the removal of starch stain reduced the total color differences, improved the surface morphology.

Evaluation of guar gum for the consolidation of some cellulosic packaging materials for mummies

As known, linen and muslin cotton fibers are used in museums and excavation areas as packaging materials for first aid of mummies. These materials with the course of long-term exposure to improper surrounding conditions become brittle, fragile, and very weak. The current research study aimed to evaluate the effect of guar gum with different concentrations for the consolidation of linen and muslin cotton samples. Additionally, the work aimed also to monitor the changes in the properties of these mate-rials after accelerated heat aging at 100℃. The analytical techniques used for this purpose were Fourier Transform Infrared spectroscopy (FTIR) for examining the chemical changes, the morphological structure via using scanning electron microscope (SEM), mechanical properties (tensile strength and elongation), color and weight change for the treated linen and muslin cotton fabrics. The findings of FTIR proved that there were low chemical changes in the aged treated samples compared to the aged untreated samples implying that the chemical stability of the treated samples was increased while treatment with guar gum. There was good distribution in the fiber structure of the treated samples as shown from SEM data. The aged treated samples showed less destruction in the fiber structure compared to the aged untreated samples. The mechanical properties were also improved. The total color differences obtained from treated and aged treated muslin cotton samples were better than the linen samples. Moreover, the accelerated heat aging had an effect on the weight of the aged treated samples, which were better than the aged untreated samples.

Оценка ресурса и характеристик изоляции тяговых двигателей локомотивов методом ускоренного теплового старения

Objective: An equivalent mode of accelerated thermal aging of the insulation system of electrical ma- chines is described to confirm the resource corresponding to a given period and operating conditions. Methods: The equivalent mode of accelerated heat aging was determined based on the Montzinger rule and tested in the course of research and development work (R&amp;D) on the development, manufacture and implementation of a set of bench and operational tests of the insulation system of an increased heat resistance class of a diesel locomotive traction motor. Results: The relevance of R&amp;D has been revealed, as a result of which the implementation of the idea was required, based on the statement about the re- duction of the insulation resource of electrical machines when the permissible heating is exceeded by 8–12 °С to various types of insulating materials. The advantages of the method presented in the article in relation to traditional solutions of this problem are demonstrated, and also improved consumer proper- ties of the traction electric motor of a diesel locomotive with a replaced insulation system of an increased class of heat resistance are presented. Generally, experimental tests and preliminary operational data are an acceptable basis for thermal evaluation of electrical insulating materials. However, it is important to remember that the scientific criterion is met and not to use the results of different types of tests in the analysis. Based on the world experience in diagnostics of additional insulation parameters for monitoring the state of insulation parameters, the possibility of using the “Doctor” series insulation monitoring de- vices has been determined and practically confirmed. Together with the results of subsequent operational tests, during which the insulation was also monitored using these mobile devices, it is argued that after carrying out the relevant research work, thanks to the mobile devices of the “Doctor” series, it is pos- sible to carry out predictive analytics of the failure of traction motors (TED) in any operating conditions. The functional value is determined and applied in practice. The “H” class insulation system developed by the specialists of JSC “VNIKTI” is mainly based on insulating materials produced by JSC “Holding Company „Elinar“”; the compound “Elplast 180ID” (JSC “Electroizolit”) or its analogue “Elkom-180” JSC “Holding company „Elinar“”), for anchor coils and equalizers, a wound PPIPK-2 wire in polyimide- fluoroplastic insulation (GC “Moskabelmet”) is used. Practical importance: It is stated that all stages of manufacturing and testing, determined at the initial stage of R&amp;D, confirmed the results of the deve- lopment stages (overhaul (manufacture) of prototypes of TED using a new isolation system according to the design documentation of JSC “VNIKTI”). Bench tests have confirmed typical characteristics, speci- fied resource and insulation characteristics with equivalent accelerated thermal aging corresponding to an electric motor’s service life of 20 years in ordinary operation on a diesel locomotive, residual life of elements of the insulation system of naturally cut armature segments, main and auxiliary poles coils. In the specialized laboratory of JSC “Holding Company „Elinar“”, an experimental TED diesel locomotive set with the investigated insulation system was manufactured and installed on two sections of the main- line diesel locomotive 2TE116. Operational tests of an experimental TED diesel locomotive set under operating conditions were successful.

Article 3

Carbogel, a polyacrylic acid, has been applied for cleaning diff-erent materials in the field of archaeological conservation, but it was rarely applied on wooden artifacts, and its effect on wood has not been assessed. Therefore the aim of this paper is to study the effects of carbogel poultices on one type of wood, namely pine wood, a softwood commonly used in many countries around the world throughout history. Three different Carbogel poultices were prepared by mixing in: distilled water, water and ethyl alcohol and water and acetone. Wood samples were covered with the different carbogel mixtures for 5, 15 and 30 minutes. To assess the long term effect of Carbogel on the treated wood, samples were exp-osed to accelerated heat ageing and humidity. Infrared spectroscopy analyses of treated and aged wood were conducted to study the effect of the poultices on wood components. Color change meas-urements and visual examination using a digital microscope were recorded. The results obtained indicated that carbogel can be safely applied in cleaning wooden artifacts made of softwoods, because its effect on wood components is minute and color change is negligible.

A novel class of high molecular weight multifunctional antioxidants for polymers based on thiol-ene click reaction

Novel bifunctional antioxidants (AO) with high molecular weight were successfully synthesized by two-step free-radical thiol-ene click reaction and transesterification. The structures of the stabilizers were confirmed by 1H NMR spectra and Fourier Transform Infrared Spectrometry (FTIR). Thermal gravimetric analysis (TGA) showed high temperature stability above 300 °C, proving suitability as potential stabilizers for standard and technical polymers. The performance of the bifunctional antioxidants was investigated through oxidation induction time (OIT) and accelerated heat aging of PP compounds in comparison to state of the art stabilizers represented through 2,2′-thiodiethylene bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and a binary mixture of pentaerythritol tetrakis(3,5-di-tert-butyl-4-hydroxyhydrocinnamate) and dioctadecyl 3,3′-thiodipropionate. Reduced degradation and extended maintenance of mechanical values of PP stabilized through the novel antioxidants during heat aging are due to the high amount of alkyl sulfide groups. Furthermore, a low migration tendency of the high-molecular AO could be determined by FTIR mapping of heat-treated samples.

Synthesis of a novel liquid phosphorus-containing flame retardant for flexible polyurethane foam: Combustion behaviors and thermal properties

To overcome the shortcomings of limited flame retardant efficiency and migration of commercialized dimethyl methylphosphonate (DMMP) in flexible polyurethane foams (FPUFs), a novel liquid phosphorus-containing flame retardant named bis((dimethoxyphosphoryl)methyl) phenyl phosphate (BDMPP) was synthesized via dimethyl (hydroxymethyl)phosphonate and phenyl dichlorophosphate and applied into FPUFs. Compared with DMMP, BDMPP contains two kinds of phosphorus with higher molecular weight and one kind of its phosphorus is very similar with that of DMMP. The flame retardancy of FPUFs was evaluated by limiting oxygen index (LOI), vertical burning test and cone calorimetry test. In contrast with DMMP, BDMPP showed better flame retardancy. When 20 wt% BDMPP (relative to polyether polyol) was incorporated, the foam composite obtained an LOI value of 23.0% and passed the vertical burning test. Thermogravimetric analysis (TGA) demonstrated that BDMPP containing FPUFs had better thermal stability and more char yield than those of DMMP containing FPUFs. Moreover, accelerated heat ageing test revealed that BDMPP exhibited better resistance to migration than DMMP. The flame retardant mechanisms were investigated by FTIR, thermogravimetric analysis/infrared spectrometry (TG-IR), scanning electron microscopy and Raman spectroscopy. Compared with DMMP, the increase in the flame retardancy of BDMMP in FPUFs is possibly due to its different structure.

Comparison in composite performance after thermooxidative aging of injection molded polyamide 6 with glass fiber, talc, and a sustainable biocarbon filler

ABSTRACTDegradation is an unavoidable part of a material's life making it important to both monitor and control the aging behavior of plastics. This study compares thermooxidative degraded composites of a novel bio‐based and sustainable filler, Biocarbon (MBc), against that of traditional and commercially available fillers (glass fiber and talc) used in the automotive industry. The influence of thermooxidative degradation on the composites was studied under accelerated heat aging for 1000 h at 140°C. The mechanical properties of the composites were evaluated using notched Izod impact as well as both tensile and flexural tests. Morphological structure of the composites was investigated using a scanning electron microscopy. Dynamic mechanical analysis and differential scanning calorimetry were used to evaluate the physical transitions both before and after aging. The glass‐filled composites displayed the best performance; while, both the talc and biocarbon composites possessed similar strength and ductility performances. Advantageously, the biocarbon composites experienced an 11% reduction in density as compared to talc‐filled composites with similar weight content. After aging, all composites exhibited reduced tensile and flexural strengths ranging from 5 to 67% partly due to chain scission. Whereas, the modulus of all composites increased with a range of 1–24% due to an annealing effect. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci.2020,137, 48618.

ACTIVATION ENERGIES OF THERMO-OXIDIZED NITRILE RUBBER COMPOUNDS OF VARYING ACRYLONITRILE CONTENT

ABSTRACT The thermo-oxidative behavior of carbon black–reinforced sulfur-cured nitrile rubber compounds with varying acrylonitrile (ACN) content (18–49 wt%) was investigated. Accelerated heat aging was carried out from 40 °C to 115 °C for various aging times. Ambient aging was also included. Samples were tested for hardness, 10% tensile stress, tensile strength, elongation at break, network chain density by equilibrium solvent swell, and toluene-soluble fraction. Diffusion-limited oxidation affected data at high temperatures and was eliminated for time-temperature superposition. Linear Arrhenius kinetic behavior was confirmed throughout the whole temperature range, and calculated activation energies varied from 75 to 93 kJ/mol. Activation energies calculated through the hardness data were found to increase steadily with ACN concentration, whereas the other test responses showed less direct correlation, likely because of the influence of the underlying NBR microstructure, which changes as a function of ACN content. The high-temperature thermo-oxidative process consists of both oxidative crosslinking and chain scission reactions. Sulfur reversion and alkyl radical recombination reactions are likely prevalent at low temperatures during the buildup of hydroperoxides up to 60 °C. The shelf life of nitrile rubbers strongly depends on their ACN level, with lower ACN nitriles being more susceptible to degradation, leading to shorter shelf lives, than higher ACN-containing nitriles.

Accelerated thermal aging of grease-based magnetorheological fluids and their lifetime prediction

In this article, the effect of elevated temperature on the rheological properties of grease-based magnetorheological fluids (G-MRFs) with the focus on long-term storage lifetime has been investigated. These G-MRF samples were subjected to accelerated heat aging process for the estimation of thermal stability and useful lifetime prediction. The well-known Arrhenius-Weibull relationship with a modified Powell-Beal conjugate gradient (CGP) algorithm was employed to model the ‘life in service’ for the achievement of possible life distribution at different temperature conditions. By defining the failure criteria of G-MRF samples as a maximum reduction of either viscosity or shear stress by more than 10%, the underlying degradation mechanism was revealed through Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) analysis. Based on the statistical inference from accelerated life test (ALT), the life expectancy of G-MRF under nominal operating temperature is estimated to be 15.2 years, which outpaces the capability of most industrial applications. Experimental results showed that the performance of shear stress is more likely to degrade under long-term treatment of high temperature in comparison with low temperature. Thus, it is suggested to store the G-MRF at relatively low temperatures for longevity extension and reliability improvement.

Long-term performance of β-nucleated toughened polypropylene-biocarbon composites

Thermoplastic polyolefins or TPOs are of widespread use in the automotive industry. In this study, the long-term performance of biocarbon based TPOs is investigated for the first time. The durability of these bio-based composites with and without hindered phenolic antioxidants was investigated under accelerated heat aging for 1000 h. Thermo-oxidative degradation was tracked along the specimen’s thickness using energy dispersive spectroscopy. Performance of the biocomposites was gauged by Izod notched impact and tensile properties. Microstructural changes were monitored by differential scanning calorimetry and dynamic mechanical analysis. While the tensile properties were sufficiently sustained using the antioxidants after this test, the impact strength failed to retain initial values. The morphological changes in the β crystal phase were recognized as the primary factor in the reduction of the impact strength of the biocomposites.

Determining the Service Life of Polychloroprene Parts: A Case Study in Aging Behavior

This paper addresses determination of the service life of an installed elastomeric part, which is an issue of great practical use every day in industry. Unfortunately, this issue is commonly misunderstood and mishandled. The perennial confusion between “shelf life” and “service life” is clarified. A comprehensive survey of published literature on polychloroprene (CR or neoprene) aging is provided. The methodology, considerations and pitfalls of similarity analysis, accelerated heat aging and prediction using activation energy are illustrated with a case study. Shear in the dynamic mode, tensile, hardness, specific gravity and volume swell were the tests used to quantify the effect of heat aging. Tensile modulus and volume swell were determined to be the tests most sensitive to changes resulting from heat aging while specific gravity was the least sensitive. Although illustrated by an example of a polychloroprene part, this methodology is equally valid for the assessment of other elastomers also.

Thermal–oxidative degradation and accelerated aging behavior of polyamide 6/epoxy resin‐modified montmorillonite nanocomposites

ABSTRACTPolyamide 6 (PA6) nanocomposites based on epoxy resin‐modified montmorillonite (EP‐MMT) were prepared by melt processing using a typical twin‐screw extruder. X‐ray diffraction combined with transmission electron microscopy was applied to elucidate the structure and morphology of PA6/EP‐MMT nanocomposites, suggesting a nearly exfoliated structure in the nanocomposite with 2 wt % EP‐MMT (PA6/2EP‐MMT) and a partial exfoliated‐partial intercalated structure in PA6/4 wt %EP‐MMT nanocomposite (PA6/4EP‐MMT). The thermogravimetric analysis under air atmosphere was conducted to characterize the thermal–oxidative degradation behavior of the material, and the result indicated that the presence of EP‐MMT could inhibit the thermal‐oxidative degradation of PA6 effectively. Accelerated heat aging in an air circulating oven at 150°C was applied to assess the thermal–oxidative stability of PA6 nanocomposites through investigation of reduced viscosity, tensile properties, and chemical structure at various time intervals. The results indicated that the incorporation of EP‐MMT effectively enhanced the thermal–oxidative stability of PA6, resulting in the high retention of reduced viscosity and tensile strength, and the low ratio of terminal carboxyl group to amino group. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40825.