Reactive antioxidants for peroxide crosslinked polyethylene (original) (raw)
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Polymer Degradation and Stability, 2003
Comparative experiments were carried out with two hindered phenolic antioxidants of different chemical structures to determine their hydrolytic stability and performance in the presence of extractive media. Hostanox O10 1 (HO10) and Hostanox O3 1 (HO3) were hydrolysed in solution and the reaction products were identified by HPLC-ESI-MS analysis. The efficiency of the two additives was checked by standard multiple extrusion test in HDPE. Samples were stored in water for a year to determine their hydrolytic stability under more practical conditions. The results proved that Hostanox O10 is a better processing stabilizer than HO3, while the latter performs much better under the effect of extractive media. Besides hydrolysis other reactions, mainly the splitting off one or more alkyl groups from the original molecule, may also take place during storage at 80 C in water, which may also lead to a decrease in stabilizer efficiency. The results clearly prove that high efficiency in a short-term laboratory test is not the only criterion to rank a stabilizer. Under long term conditions such as storage in an extractive environment HO3 outperforms HO10. #
Journal of Biomedical Materials Research Part A, 2010
Oxidative degradation of the polyurethane elastomeric (PU) components greatly reduces the efficacy of PU-containing cardiovascular devices. Covalently appending the phenol-based antioxidant, 4-substituted 2,6-di-tert-butylphenol (DBP), to PU hard segments effectively reduced oxidative degradation of the PU in vivo and in vitro in prior studies by our group. In these experiments, we analyze the contribution of the tethering molecule to the antioxidant capabilities of the DBP-modified PU. Bromoalkylation chemistry was used to link DBP to the hard segment of the polyether PU, Tecothane, via our original linker (PU-DBP) or variants containing side chains with one (PU-C-DBP) or three (PU-3C-DBP) carbons. Two additional DBP variants were fabricated in which the DBP group was appended to the alkyl chain via an oxygen atom (PU-O-DBP) or an amide linkage in the middle of the tether (PU-NHCO-DBP). All DBP variant films and unmodified control films were subject to oxidative degradation via 15-day immersion in a solution of 20% H 2 O 2 þ 0.1M CoCl 2 . At the end of the oxidation protocol, films were analyzed for the presence of oxidation-related endpoints via scanning electron microscopy, contact angle measurements, and Fourier transformation infrared spectroscopy (FTIR). All DBP-containing variants resisted oxidation damage significantly better than the unmodified control PU. SEM analysis of oxidized PU-C-DBP and PU-O-DBP showed evidence of surface cracking, consistent with oxidative degradation of the PU surfaces. Similarly, there was a trend in increased ether crosslinking, a marker for oxidative degradation, in PU-C-DBP and PU-NHCO-DBP films. Consistent with these FTIR results, both PU-C-DBP and PU-NHCO-DBP had significant reductions in measured surface hydrophobicity as a result of oxidation. These data show for the first time that the choice of linker molecule significantly affects the efficiency of the linked phenolic antioxidant. V C 2010 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 94A: 751-759, 2010
European Polymer Journal, 1978
Oxidation of atactic polypropylene (PPH) has been used in the preparation and characterization of hydroperoxide PPOOH, from which radicals PPOO. were generated. Their interaction with 2,6-ditert-butyl-4-methylphenol (BHT) demonstrated transformations of the antioxidant, leading, on the one hand, to peroxycyclohexadienone, PPOO-CHD, in which the residue of reacted BHT is bound on PPOO" and, on the other, to compounds resulting from the oxidative coupling .of BHT; of these, 4,4'-ethylenebis (2,6-ditert-butylphenol) and 3,3',5,5'-tetratert-butylstilbenequinone were identified. Further products of coupling are light-to deep-brown; some of them contain phenolic and quinomethinoidic functions. PPOO-CHD may take an active part in the atmospheric ageing of PPH arising from decomposition caused by heat, radiation or catalytic impurities.
Antioxidative activity of 3-aryl-benzofuran-2-one stabilizers (Irganox®HP-136) in polypropylene
Polymer Degradation and Stability, 2002
Irganox 1 HP-136(lactone), which is a mixture of 90% of 5,7-di-tert-butyl-3-(3,4-dimethylphenyl)3H-benzofuran-2-one and 10% of 5,7-di-tert-butyl-3-(2,3-dimethylphenyl)3H-benzofuran-2-one behaves as a medium strength chain-breaking antioxidant during polypropylene oxidation at 180 and 200 C. The critical concentration (vide infra) required to inhibit oxidation is higher than that of the phenolic antioxidant 2246. The lactone is slowly consumed during the induction period and then much faster when the critical concentration is reached. Phosphites, sulphides and phenols increase the efficiency of the lactone during polymer oxidation. The use of lactone allows the amount of phenolic and phosphorous containing stabilizers to decrease without decreasing the thermooxidative stability of the polymer.
Natural antioxidants as stabilizers for polymers
Polymer Degradation and Stability
The additive packages routinely used today usually consist of a phenolic antioxidant and a phosphorus or sulfur containing secondary stabilizer. Several years ago some questions were raised about the health and environmental hazard of these additives and industry has not offered an alternatively solution yet. Nature produces a large number of antioxidants, which play a key role in radical reactions taking place in the human body. The substances containing these antioxidants are used in natural medicine for ages and they are applied in increasing quantities also in the food industry. The application of natural antioxidants for the protection of polymers is in its infancy, the information available is limited and often contradictory. This review paper summarizes published results, analyzes them and points out the advantages and drawbacks of the approach. Although a wide variety of compounds have been added to polymers to improve their stability, the most promising candidates are the carotenoids, the flavonoids, other natural phenols and phenolic polymers including lignin. Available results indicate that flavonoids are much more efficient stabilizers than the hindered phenols used in industrial practice. On the other hand, most of the natural antioxidants discolor the polymer and their solubility is limited. Nevertheless, natural antioxidants can be efficiently used in specific applications, but further research is needed to explore all their advantages and include them into additive packages used in practice.
Clinical orthopaedics and related research, 2015
Ultrahigh-molecular-weight polyethylene (UHMWPE) is subjected to radiation crosslinking to form highly crosslinked polyethylene (HXLPE), which has improved wear resistance. First-generation HXLPE was subjected to thermal treatment to reduce or quench free radicals that can induce long-term oxidative degeneration. Most recently, antioxidants have been added to HXLPE to induce oxidative resistance rather than by thermal treatment. However, antioxidants can interfere with the efficiency of radiation crosslinking. We sought to identify (1) which antioxidant from among those tested (vitamin E, β-carotene, butylated hydroxytoluene, or pentaerythritol tetrakis [methylene-3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate]) causes the least reduction of crosslinking; (2) which promotes the greatest oxidative stability; and (3) which had the lowest ratio of oxidation index to crosslink density. Medical-grade polyethylene (PE) resin was blended with 0.1 weight % of the following stabilizers: al...
Macromolecules, 2018
Currently, hindered phenol (HP) antioxidants mixed in PP products provide thermal-oxidative protection during PP melt processing (homogeneous mixing). However, there are concerns about their effectiveness during applications. This paper presents computer simulation and experimental results to demonstrate a facile phase separation of HP molecules in the PP matrix and investigates a new approach that can dramatically improve PP thermal-oxidative stability under elevated temperatures. This technology is centered on a new PP−HP copolymer containing a few comonomer units with HP moieties, homogeneously distributed along the polymer chain. Because of the cocrystallization between the PP and PP−HP copolymer, all HP antioxidant groups are homogeneously distributed in the PP matrix (amorphous domains). The resulting PP/PP−HP blends demonstrate a thermal-oxidative stability nearly proportional to the HP content. While commercial PP products (containing regular antioxidants and stabilizers) degrade within a few minutes at 210°C in air, the PP/PP−HP blend, with the same concentration of HP groups, demonstrates nearly no detectable weight loss after 1000 h. In an ASTM endurance test under a targeted application temperature (140°C in air), the commercial PP shows 1% weight loss within 10 days. On the other hand, the new PP/PP−HP (5/1) blend with the same HP content lasts for about 2 years under the same constant heating condition. Overall, the experiment results of the PP−HP antioxidant present the potential of expanding PP applications into a far higher temperature range (>140°C) under thermal-oxidative environments.