Mechanism of the degradation of polyamides

Achhammer, B. G.; Reinhart, Frank W.; Kline, Gordon M.

doi:10.1002/jbt.2570010704

Cited by 8 publications

(7 citation statements)

References 30 publications

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“…After that time, the samples maintained a constant weight until the end of the test. These small reductions in weight are related to the leaching of plasticizers and additives added to the polymer to prevent hardening [29,30]. It can be seen in Figure 2C that the POM did not show any significant differences in mass after immersion in the fuel blends, exhibiting small mass increases close to 0.1 wt % in B100 and B100–acid blends, during the first 8 weeks of exposure.…”

Section: Resultsmentioning

confidence: 99%

Evaluation of the Stability of Polymeric Materials Exposed to Palm Biodiesel and Biodiesel–Organic Acid Blends

2018

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Abstract:The aim of the present work is to evaluate the impact of pure palm biodiesel fuel (B100) and biodiesel blends with 0.32% oleic, palmitic, acetic, myristic, and stearic acids on the properties of some polymeric materials used commonly in the manufacture of auto parts such as the polyamide 66 (PA66), polyoxymethylene (POM), and high-density polyethylene (HDPE). The effects of the B100 and B100-acid blends on polymeric materials were examined by comparing changes in the gain/loss of mass and by measuring the hardness, the impact strength, and the tensile strength of the materials at the end of the exposure. The characterization of the polymers was carried out before and after exposure by using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and Fourier transform infrared spectroscopy (FTIR). After the immersion in B100-acids blends, the HDPE exhibited an increase in mass of 5%, which was very similar in all blends. The PA66 showed a small decrease in weight (2% approx.) in all mixtures. The POM presented an increase in the percentage of weight in the mixture of B100 with acetic acid of 0.3%. A decrease was observed in the crystallinity of the HDPE when exposed to blends of B100-acids. This behavior may be associated with a plasticizing effect in the HDPE exposed to the blends. The mechanical properties of POM and HDPE showed no significant changes after immersion in the fuels. On the other hand, PA66 exhibited a significant decrease in maximum stress value after immersion in B100, B100-oleic acid and B100-palmitic acid blends. The variation of the mechanical properties of the PA66 after exposure to B100 was potentiated by addition of organic acids. The assessed polymers did not undergo appreciable changes in the chemical structure of the samples after immersion in the fuels, so the variation in the mechanical properties could be explained by physical absorption of the fuel into the polymers.

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Section: Resultsmentioning

confidence: 99%

Evaluation of the Stability of Polymeric Materials Exposed to Palm Biodiesel and Biodiesel–Organic Acid Blends

2018

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“…The free OH from EVOH reacts with PA and forms adipic acid, which eventually reduces to cyclopentane (m/z = 84), CO 2 (m/z = 44), and H 2 O at around 285−295 °C (demonstrated in reaction Scheme 3). 32 In PA/EVOH/MB, at the interface region, PP-g-MA reacts with both polymers, as shown in reaction Scheme 4, and forms cross-linked structures. The formation of long chains in an intermediate step could be responsible for the initial high cross-link densities in PA/EVOH/MB, as shown in Figure 10.…”

Section: Resultsmentioning

confidence: 99%

Mechanism of Thermal Degradation-Induced Gel Formation in Polyamide 6/Ethylene Vinyl Alcohol Blend Nanocomposites Studied by Time-Resolved Rheology and Hyphenated Thermogravimetric Analyzer Fourier Transform Infrared Spectroscopy Mass Spectroscopy: Synergistic Role of Nanoparticles and Maleic-anhydride-Grafted Polypropylene

2019

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In this study, polyamide 6 (PA) is blended with ethylene vinyl alcohol (EVOH) to yield packaging materials with a balance of mechanical and gas barrier properties. However, the formation of gel-like structures in both polymers because of thermal degradation at high temperatures leads to a processing challenge, particularly during thin-gauge film extrusion. To address this challenge, nanoclays are introduced either directly or via a masterbatch of maleic-anhydride-grafted polypropylene to the PA/EVOH blend and time-resolved rheometry is used to study the effect of different modes of nanoclay incorporation on the kinetics of thermo-oxidative degradation of PA/EVOH blend and its nanocomposites. Time-resolved rheometry measurements allow the acquisition of accurate frequency-dependent linear viscoelastic behavior and offer insights into the rate of degradation or gel formation kinetics and cross-link density. The thermal degradation was studied by thermogravimetric analysis coupled with Fourier transform infrared spectroscopy and mass spectroscopy, allowing the prediction of the possible reactions that take place during the rheological property measurements. The results show that when nanoclays are incorporated directly, the oxidative reactions occur faster. In contrast, in the masterbatch method, oxidative degradation is hindered. The difference in the behaviors is shown to lie in the different nanoclay distributions in the blends; in the blends prepared by the masterbatch method, the nanoclays are dispersed at the interface. In conclusion, the masterbatch-containing blend nanocomposite would benefit processing and product development.

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“…This change may be attributed to the decrease in the number of the amide groups by the scission reaction as in eq. (2) and to the decrease in the number of the methylene groups which move cooperatively with the amide groups by the crosslinking reaction. The change in the dynamic modulus by the photodegradation is the same as that in the dry state.…”

Section: )mentioning

confidence: 97%

Effect of photodegradation on dynamic mechanical properties of nylon 6

Yano¹,

Murayama²

1980

J of Applied Polymer Sci

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SynopsisChanges in the dynamic mechanical properties of nylon 6 (a-form) under ultraviolet light irradiation were investigated. On irradiation with spectrally dispersed ultraviolet light in the wavelength range of 219-415 nm, the dynamic modulus E'and the density of nylon 6 were increased below about 300 nm. It was found that the increment in E' and the density were the result of crosslinking. When E' was measured with time elapsed during irradiation by light of 253.7 nm, E' initially decreased with time, increased at a longer time, and then reached a limiting value asymptotically. From the result of the change in E' with time, it was assumed that the scission and crosslinking reactions occur simultaneously during ultraviolet light irradiation. Thus, the change in E' with elapsed time was expressed by the equation E; = Eb exp (-kit) + Eb.[1-exp ( -k z t ) ] , where E ; is the dynamic modulus at time t , Eb is the E' at t = 0, Eb. is the limiting value of E', and k l and kz are the rate constants. The apparent activation energies for k l and k z were 3.23 and 2.50 kcal/mole, respectively, and the former value agreed with the activation energy for the scission of the amide groups. The effects of the photodegradation on the temperature dispersion of nylon 6 were also investigated. On irradiation with light at 253.7 nm, the a-relaxation which appeared at about 90°C was broadened and the intensity of the y-relaxation at -95OC in the tan 6-versus-temperature curve was lowered. The B-relaxation which appeared at -45OC for the wet nylon 6 decreased its intensity.

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Mechanism of the degradation of polyamides

Cited by 8 publications

References 30 publications

Evaluation of the Stability of Polymeric Materials Exposed to Palm Biodiesel and Biodiesel–Organic Acid Blends

Evaluation of the Stability of Polymeric Materials Exposed to Palm Biodiesel and Biodiesel–Organic Acid Blends

Effect of photodegradation on dynamic mechanical properties of nylon 6

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