Thermo-oxidation Of Polypropylene Research Articles

Photo- and Thermo-Oxidation of Polypropylene, Recycled Polypropylene and Polylactide Biocomposites in a Microenvironment Chamber

This work presents and discusses the photo- and thermo-oxidation of some sustainable biocomposites based on biodegradable materials from renewable resources and virgin and recycled petroleum-based polymeric materials as matrix and reinforced with natural fibres. PP/wood flour, recycled PP/cellulose and PLA/wood flour composites were degraded by photo-oxidation in a microenvironment chamber, in parallel thermo-oxidation was performed in a forced-ventilation oven. Physical and chemical property changes were monitored by tensile testing, DSC, FTIR and SEM. Both PPW and recPPcell composites showed deterioration of the mechanical properties after 15 days of thermo-oxidation, indicating that the incorporated natural fibres influenced the thermal stability of the whole composite. PLAW showed a smaller increase in crystallinity (13%) and a decrease in melt temperature than the corresponding neat PLA. The advantages of reinforcement of PLA by natural fibres are shown by the dramatically improved thermal properties of PLAW compared to the neat polymer.

A representation of the autoacceleration stage of polypropylene thermooxidation in reduced coordinates

The kinetic curves of hydroperoxide build-up and chemiluminescence emission along the thermooxidation of polypropylene have been normalised by using the co-ordinates of the autoacceleration point of inflection. It has been found that the curves thus normalised do not depend on the oxidation temperature (between 130 and 160°C) nor on the presence of stabilisers or on whether the kinetics of chemiluminescence emission or hydroperoxide build-up are considered. To find out what do these curves depend on, the spreading equation given by George and co-workers (George GA, Celina M, Lerf C, Cash G, Weddell D. Macromol Symp 1997;115;69) has been normalised with the co-ordinates of its analytical point of inflection. The normalisation of the spreading equation results in a new function which depends only on one parameter, a, which is related to the initial fraction of oxidation centres. The comparison of experimental normalised curves with the analytically normalised spreading equation is proposed as a means of further understanding the initiation and propagation of oxidation in polypropylene.

Antioxidative efficiency of N‐(arylamine) imides in thermal oxidation of polypropylene

AbstractElectron‐donating substituents of N‐(arylamine) phthalimides and succinimides promote antioxidative efficiency of these compounds in thermooxidation of polypropylene (190°C, oxygen), while electron‐withdrawing substituents contribute to a reduced volatilization of the polymer. 2,6‐Ditert.butyl‐4‐methylphenol (ionol) raises the antioxidative efficiency of 4‐methoxy and 4‐methyl substituted derivatives displaying a distinct synergism.

Thermo-oxidation of polypropylene in the presence of PbO

A significant retardation effect by PbO on the formation of volatile products from isotactic polypropylene (IPP) was found at temperatures up to 380°C. The effect is explained by the formation of a surface active form of PbO (possibly Pb 3O 4) which is formed by interaction of PbO with peroxy radicals. Primary and secondary alkyl radicals terminate effectively on the active surface and the kinetic length of the degradation reaction is thus decreased. A compensation effect exists between the Arrhenius parameters ln A and E for both inhibited and uninhibited formation of volatile products.

Thermo-oxidation of polypropylene in the presence of triphenylphosphonium cyclopentadienylide

From measurements of weight losses of samples of isotactic polypropylene (IPP) with triphenylphosphonium cyclopentadienylide (TPCP) under various conditions and from the measurements of time courses of chemiluminescence, kinetic parameters of the process were determined. At concentrations of TPCP >1 wt%, the rate of loss of weight changes with the additive concentration. Compensation of the values of activation energy and pre-exponential term, determined from thermo-oxidation of IPP alone and IPP with TPCP, indicates that interaction of TPCP with oxidized polymer is complex.

Chemiluminescence in thermo-oxidation of polypropylene

Chemiluminescence in thermo-oxidation of polypropylene was interpreted, noting its course with time at different temperatures and the corresponding spectra. The light emission was attributed to decomposition of α-ketone-hydroperoxides and to chain oxidation of polymer proceeding via secondary peroxy radicals.

Analysis of thermo-oxidation products of polypropylene and polyethylene by Gas chromatography/mass spectrometry

Thermal and thermo-oxidative degradation of polyethylene and polypropylene is discussed. The products of thermal and thermo-oxidative degradation are analysed using a GC-MS after previous adsorption in a column containing a sorbent of styrene divinyl benzene copolymer type. Aldehydes are the products mostly resulting from the thermo-oxidation of polyethylene and methyl ketones are those resulting from the thermo-oxidation of polypropylene.