The weathering of polymers is reviewed with attention concentrated on the mechanisms of degradation and stabilization, the methods of testing weatherability, and the predictive modelling of weathering behaviour. An introduction to the chemical mechanisms of degradation and stabilization is given and reference made to some of the many reviews available in the literature. Significant emphasis is placed here on engineering aspects, such as the way that weathering influences fracture mechanisms. The difficulties associated with relating accelerated laboratory tests with outdoor service behaviour are discussed. The complexities of the degradation processes limit modelling of the rate of degradation to rather specific systems and the predictions cannot be generalized.

Weathering of polymers: mechanisms of degradation and stabilization, testing strategies and modelling

The radiation chemistry of fluoropolymers

An ultrasensitive technique for testing the Arrhenius extrapolation assumption for thermally aged elastomers

Quantitative model for the time development of diffusion-limited oxidation profiles

https://digital.library.unt.edu/ark:/67531/metadc785174/m2/1/high_res_d/8479.pdf

Correlation of Chemical and Mechanical Property Changes During Oxidative Degradation of Neoprene

Modulus profiling of polymers

: When polymeric materials are irradiated in the presence of air, oxygen-diffusion effects can, depending upon dose rate, lead to oxidative degradation which occurs only near the edges. This report describes the use of several recently developed techniques which are of general use for studying heterogeneous degradation in commercial polymeric materials. The techniques discussed are: optical evaluation of cross-sectioned, polished samples; cross-sectional profiling of changes in relative hardness; and profiling of density changes. Oxidation penetration depths are given for a number of major polymer types as a function of dose rate. A detailed example is given graphically illustrating the effects of differing oxidative penetration depths on the radiation-degradation behavior of a Viton(R) O-ring material; this particular material becomes hard and brittle when irradiated at high dose rate. but soft and stretchable when irradiated at low dose rates. jg p4

Heterogeneous oxidative degradation in irradiated polymers

Low density, microporous polymer foams are provided by a process which comprises forming a solution of polymer and a suitable solvent followed by rapid cooling of the solution to form a phase-separated system and freeze the phase-separated system. The phase-separated system comprises a polymer phase and a solvent phase, each of which is substantially continuous within the other. The morphology of the polymer phase prior to and subsequent to freezing determine the morphology of the resultant foam. Both isotropic and anisotropic foams can be produced. If isotropic foams are produced, the polymer and solvent are tailored such that the solution spontaneously phase-separates prior to the point at which any component freezes. The morphology of the resultant polymer phase determines the morphology of the resultant foam and the morphology of the polymer phase is retained by cooling the system at a rate sufficient to freeze one or both components of the system before a change in morphology can occur. Anisotropic foams are produced by forming a solution of polymer and solvent that will not phase separate prior to freezing of one or both components of the solution. In such a process, the solvent typically freezes before phase separation occurs. The morphology of the resultant frozen two-phase system determines the morphology of the resultant foam. The process involves subjecting the solution to essentially one-dimensional cooling. Means for subjecting such a solvent to one-dimensional cooling are also provided. Foams having a density of less than 0.1 g/cc and a uniform cell size of less than 10 μm and a volume such that the foams have a length greater than 1 cm are provided.

Low density microcellular foams

An apparatus has been developed which allows one to easily obtain >20 tensile compliance measurements per mm of sample cross section. Modulus profiles are shown for radiation-aged viton and 120/sup 0/C-aged nitrile rubber. (DLC)

Carlos A. Quintana

Papers

Modulus profiling of polymers

Heterogeneous oxidative degradation in irradiated polymers

Low density microcellular foams

Aging studies of elastomers using a modulus profiling apparatus