The photolysis and photo-oxidation of poly(ethylene 2,6-naphthalene-dicarboxylate) have been investigated using Fourier transform infrared spectroscopy and UV absorption spectroscopy. Four different ...polymers with 0, 8, 50 and 100% naphthalene dicarboxylate as the aromatic unit were studied and compared. The results indicate that the photochemical reactions are restricted to the very outer surface of the polymer within a layer around 10 μm. Photo-oxidation is responsible for the formation of acidic end groups as major photoproducts. An intense photoyellowing resulting from the conversion of the naphthalate units, accompanied by the formation of gel, was observed.
The degradation of three high density polyethylene geomembranes (GMBs) (denoted xA, xB and xC) when immersed in simulated landfill leachate at 85 °C is examined. All three GMBs met the requirements ...of the generic industry specification GRI-GM13 with respect to their performance properties. The large high-pressure oxidative induction time (HP-OIT) (i.e., 790 min for xB and 960 min for xC) combined with the relatively high level of trace nitrogen detected, suggest the presence of hindered amine light stabilizers (HALS) as part of the antioxidant package in these GMBs, whereas, the relatively low initial HP-OITs (i.e., 260 min) and the low level of trace nitrogen for xA, suggest the absence of HALS in xA. Although xA had the lowest initial standard Std-OIT (Std-OIT was 115, 158 and 175 min for xA, xB and xC, respectively) it exhibited the longest time to antioxidant depletion based on Std-OIT. For the three GMBs, the HP-OIT depleted following exponential decay model until reaching a residual value. xB had the slowest HP-OIT depletion (0.016 month−1) and was still depleting without reaching a residual value at the end of this study (after 46 months). xA experienced the fastest HP-OIT depletion (∼62 times faster than of xB) and reached a residual value of 78 min. For xC, HP-OIT depleted 40 times faster than for xB reaching a residual value (∼610 min) that was still higher than the HP-OIT of 400 min specified by GRI-GM13 for a new GMB. xB had the longest time to nominal failure despite having the lowest initial SCR value (330 h for xB compared to 910 and 800 h for xA and xC, respectively) and not having the highest OITs values. Although xC had a residual HP-OIT of 610 min, the SCR, melt index (MI) and tensile properties for xC had decreased to the point that xC was at nominal failure, indicating that the degradation can take place without the total depletion of antioxidants/stabilizers captured by the HP-OIT.
The depolymerisation of low molecular weight poly(ethylene oxide) (PEO) under mild conditions was studied using a linear temperature ramped non-isothermal technique and the results compared with ...those obtained from a conventional isothermal technique. The analysis of the non-isothermal kinetic (NIK) data was performed using an original computer program incorporating an algorithm that systematically minimizes the sum of the squares of the residuals between the experimental data and the calculated theoretical kinetic profile in order to extract the kinetic parameters. The results revealed that the depolymerisation of PEO proceeds in accordance with the Ekenstam model and follows the Arrhenius equation over the temperature range of
ca. 40–130 °C. The NIK analysis resulted in a two-dimensional convergence to produce a unique solution set for the kinetic parameters of
E
a = 89.4 kJ mol
−1 and
A = 9.6 × 10
6 h
−1. These data are consistent with the results obtained from the isothermal experiments. It is proposed that NIK analysis is a quick and reliable means of obtaining kinetic parameters relevant to lifetime predictions in polymers whose degradation behaviour can be considered to be close to ideal.
A dynamic heating experiment was used to examine the influence of temperature on the degradation of the Kraft insulating paper in transformer oil. The degradation was monitored by measuring a number ...of key indicators on selected samples as a function of progressive ageing. These indicators included the degree of polymerization (DP), level of furanic compounds and level of gases such as carbon oxides and oxygen. The results show that the formation of furanic compounds and of gases begins significantly after a large reduction in DP, indicatinga two-stage process: firstly scission leading to a sharp drop in DP and secondly formation of low molecular weight degradation products.
The degree of polymerization (DP) of a polymer system subjected to non-isothermal depolymerization is examined kinetically with a preliminary application to the study of cellulose degradation. An ...equation for the time dependence of the DP observed under non-isothermal degradation using a linear temperature ramp is derived from the relevant isothermal kinetic equations. An iterative computerbased method of fitting non-isothermal degree of polymerization (NIDP) data is also presented. The activation energy and the Arrhenius A-factor associated with the depolymerization process can be varied independently to achieve an optimized fit to experimental NIDP data and may be used to calculate the predicted lifetime of the polymer in service. The potential of NIDP data analysis to quickly deliver these kinetic parameters is identified and the confidence ranges in the predicted lifetimes derived from NIDP data analyses appear to be similar to those derived from isothermal analyses of DP data. Experimental NIDP data support the notion that the prolonged degradation of cellulose does not produce oligomers of DP much less than ca. 200.
The antagonism between five commercial grades of erucamide and seven commercial grades of inorganic antiblock agents used in LDPE film formulations is investigated. Mixtures of erucamide and ...antiblock agents were thermally aged in air at 90°C and the increase in discoloration of the mixtures was quantified by measuring the optical absorbance at 440
nm. The formation of coloured degradation products of erucamide appears to be autocatalytic and increases with increasing pH of the antiblock agent. The experimental results suggest impurities in commercial antiblock agents such as transition metal oxides and alkaline earth metal oxides as well as surface silanol groups in silica antiblocks play significant roles in the degradation of erucamide. A mechanism is proposed to account for the observed variation in the extent of antagonism exhibited by the different antiblock agents.
Infrared and UV absorption spectroscopy were used to study the photochemical behaviour of poly(butylene naphthalate) (PBN). Based on a comparison with poly(ethylene naphthalate) (PEN) and ...poly(butylene terephthalate), the mechanism accounting for the formation of the photoproducts responsible for the yellowing and the chain scissioning were proposed. The photochemical oxidation of PBN was shown to be restricted to the surface layer (~5 μm) whilst the photoyellowing affected a thicker layer.
The application of oxygen uptake techniques to the determination of polyolefin stability is extensively reviewed and includes the consideration of both manometric apparatuses and devices which ...incorporate pressure transducers. The sensitivity of oxygen uptake instruments, types of heating facilities, molecular sieves and adsorbents, the shape of the oxygen uptake profile and the technique of oxygen uptake as related to other techniques are also discussed. A comprehensive table listing oxygen uptake apparatuses in chronological order is included in the review.
The characterization of oligomeric compounds separated from waste material produced in the high-pressure, free-radical ethylene polymerization process is reported. A solid wax layer, constituting 11 ...% (
w
w
) of the total waste material, was analysed by Fourier transform infrared (FTIR) spectroscopy and gas chromatography/mass spectrometry (GC-MS) and was found to contain mostly short-branched C
18C
26 paraffins. An oil fraction constituting 64% (
w
w
) of the material was identified by FTIR and NMR analyses as a polyether of complex structure. Both the wax and the oil fractions contain a degree of unsaturation. The molecular weight characteristics of the polyether were determined by gel permeation chromatography and found to be
M
n
= 1716 Da,
M
w
= 1926 Da, dispersity
M
w
/
M
n
= 1.22, using polystyrene standards to calibrate the Chromatographie column. A liquid fraction constituting about 25% (
w
w
) of the waste was separated from the oil layer by distillation. It was identified by FTIR and GC-MS analyses as mainly propan-1-one. This compound is used both as a solvent for the initiator and as a chain transfer agent in the low-density polyethylene (LDPE) polymerization process.
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