Thermo-oxidation polyethylene

The initiation of thermo-oxidation of polyethylene films by transition metal catalysts during composting proceeded slowly compared to oxidation at the same temperature in an oven (60-70 °C) [56]. The starch-filled polyethylene bags exposed on the surface of the compost broke down into small pieces while the buried bags remained intact after 49 days of exposure [55,... 

Figure 9. Distribution of nitroxyl radicals concentration by thickness of sample underwent thermo-oxidative destruction at 120°C a - poly(acrylonitril-butadiene-styrene (ABS) copolymer), thickness of sample is 3,8mm b - polypropylene copolymer with polyethylene, thickness of sample is 3,4mm. The inset is the example of EPR-spectrum of nitroxyl radical in ABS-copolymer.

Ethanox 376 is a stabilizer that provides heat stability by preventing thermo-oxidative degradation during processing and service life. It provides compatibility with resins and extraction resistance. It can be applied in polyolefins, such as polyethylene, polypropylene, polybutene-1 and other polymers such as engineering plastics, styrenes, polyurethanes, saturated and unsaturated elastomers, styrenics, rubber modified styrenics, segmented block copolymers, and PVC. 

Non-discoloring, sulfur containing phenolic antioxidant and stabilizer that provides long-term heat stability by preventing thermo-oxidative degradation. Used for the process stabilization of polyethylene wire and cable resins for polyethylene during extruder compounding. Can also be applied in styrenic polymers, polypropylene, elastomers such as EPDM and SBR and for carboxylated SBR latex, polybutadiene rubber and polyisopropene rubber. 

The search for accelerated testing procedures to predict the useful service life for polyethylene (PE) compositions has been the main incentive for numerous studies on the thermo-oxidative degradation of PE in oxygen-rich atmospheres below 200 C (1 ). 

As a result of this extensive experimental program, it has been found that in rotational molding, polyethylene and polypropylene polymers show different degradation behavior. While in polypropylene the thermo-oxidative degradation causes mainly chain scission, in polyethylene crosslinking dominates. The use of increased amounts of antioxidant in the... 

Khabbaz F, Albertsson A-C, Karlsson S (1999) Chemical and morphological changes of environmentally degradable polyethylene films exposed to thermo-oxidation. Polymer degradation and stability. 63 127-138. 

Two review articles have been published, one relating to the thermo-oxidative degradation and stabilization of polyolefins and the other to the effect of thermal and thermo-oxidative breakdown of polyethylene and polypropylene upon overall properties. The latter paper specifically considers the effects of reprocessing. A... 

Related very much to practical considerations are the results of thermooxidation in the melt, or of immersion in boiling water, followed by extrusion, of pyrolysis in a fluidized bed reactor and of thermo-oxidation of an oriented film, whilst under stress. Depending upon the stress applied the rate of oxidation may either be increased, or decreased. A study has also been made of the effects of layer thickness, temperature, oxygen pressure, and antioxidants on the thermo-oxidative degradation of both polypropylene and polyethylene. The degradation mechanisms are discussed in detail. 

Crystalline starch beads can be used as a natural filler in traditional plastics [3]. They have been particularly used in polyolefins. When blended with starch beads, polyethylene films biodeteriorate upon exposure to a soil environment. The microbial consumption of the starch component leads to increased porosity, void formation, and loss of integrity of the plastic matrix. Generally, starch is added at fairly low concentrations (6-15 wt%). The total disintegration of these materials is obtained using transition metal compounds, soluble in the thermoplastic matrix, used as pro-oxidant additives to catalyze the photo and thermo-oxidative processes [4]. These products belong to the first generation of degradable polymers that biodeteriorate more than mineralize to CO2 and H2O in a time... 

Processing stabilization of polyethylene is usually done by a combination of phenolic and phosphorous antioxidants. A phosphate stabilizer used in the absence of a phenolic antioxidant imparts very low oxidative stability to polyethylene. When hindered phenols are used in combination with phosphites or phosphonites, the melt flow behavior during processing and the thermo-oxidative stability of the polymer improve significantly. Fearon et al. [17] attributed the positive effect of phenolic antioxidants to their interaction with peroxides. The trivalent phosphorous additives often help to improve the color of polymers [18-21]. 

Polyethylene naphthalate (PEN) is a polyester with two condensed aromatic rings in molecular main chain compare to PET confer on it improvements in strength and modulus, chemical and hydrolytic resistance, gaseous barrier, thermal and thermo-oxidative resistance and ultraviolet (UV) light barrier compared to PET (Table 2.44). Pentex PEN hber produced by Honeywell, which stretches only 40% as much as standard PET hbers, shows twice than Kevlar 29. 

---