Embrittlement sampling

Ni (0.124nm) (Goldschmidt 1954), it is likely that the environmental structure around La is mainly changed in the embrittlement process. On the other hand, the reductilization process produces a slight shift of the first peak maximum towards a smaller r, and the sharpness of the peak is decreased and smoothed out at some details as shown at the bottom of fig. 135. The differences of the reduced RDFs between the embrittled and as-quenched samples, and between the reductilized and embrittled samples in the nearest-neighbor region from 0.2 to 0.45 nm are magnified and shown with the full and dotted curves in the middle of fig. 135. The profiles of the difference show an inverse pattern of G r). Consequently, it appears that the reductilization process is reversed by the embrittlement process. 

Fig. 135. Comparison of reduced RDF G(r) of embrittled (lull curve) and as-quenched (dotted curve) samples in the top panel and those of re-ductilized (dotted curve) and embrittled (liill curve) samples in the bottom panel. The diiierence in G(r) between the embrittled and as-quenched samples, and between the reductilized and embrittled samples in the nearest-neighboring region from 0.2 nm to 0.4S nm are shown in the middle panel.

Examination of oven-aged samples has demonstrated that substantial degradation is limited to the outer surface (34), ie, the oxidation process is diffusion limited. Consistent with this conclusion is the observation that oxidation rates are dependent on sample thickness (32). Impact property measurements by high speed puncture tests have shown that the critical thickness of the degraded layer at which surface fracture changes from ductile to brittle is about 0.2 mm. Removal of the degraded layer restores ductiHty (34). Effects of embrittled surface thickness on impact have been studied using ABS coated with styrene—acrylonitrile copolymer (35). 

Polyamides, like other macromolecules, degrade as a result of mechanical stress either in the melt phase, in solution, or in the soHd state (124). Degradation in the fluid state is usually detected via a change in viscosity or molecular weight distribution (125). However, in the soHd state it is possible to observe the free radicals formed as a result of polymer chains breaking under the appHed stress. If the polymer is protected from oxygen, then alkyl radicals can be observed (126). However, if the sample is exposed to air then the radicals react with oxygen in a manner similar to thermo- and photooxidation. These reactions lead to the formation of microcracks, embrittlement, and fracture, which can eventually result in failure of the fiber, film, or plastic article. 

Film or fibers derived from low molecular weight polymer tend to embrittle on immersion ia acetone those based on higher molecular weight polymer (>0.60 dL/g) become opaque, dilated, and elastomeric. When a dilated sample is stretched and dried, it retains orientation and is crystalline, exhibiting enhanced tensile strength. The tensile heat-distortion temperature of the crystalline film is iacreased by about 20°C, and the gas permeabiUty and resistance to solvent attack is iacreased. 

The polymers also have excellent resistance to oxidative degradation, most chemicals other than strong bases and high-energy radiation. Exposure for 1500 hours to a radiation of about 10 rads at 175°C led to embrittlement but the sample retained form stability. 

The nitroxide radical (from processes 5 and 6 and attack by other radicals on the parent piperidine) is found in photo-oxidizing PPH samples in concentrations of M. x 10 M (initial piperidine level 5 x 10-3M) up to the embrittlement point of the PPH film (7.). Nitroxides are well known to scavenge carbon centered radicals (but not peroxyl radicals) in both polymers and liquid alkanes (reaction 7) (10, 8). In the liquid phase k7 is... 

The cracking susceptibility of a micro-alloyed HSLA-100 steel was examined and compared to that of a HY-100 steel in the as-received condition and after heat treatment to simulate the thermal history of a single pass weld. Slow strain rate tensile tests were conducted on samples of these alloys with these thermal histories in an inert environment and in an aqueous solution during continuous cathodic charging at different potentials with respect to a reference electrode. Both alloys exhibited reduced ductilities at cathodic potentials indicating susceptibility to hydrogen embrittlement. The results of these experiments will be presented and discussed in relation to the observed microstructures and fractography. 

Elemental analyses of these samples were obtained by energy dispersive x-ray spectrometry (EOS). Total sulfur, ash, and pH of the samples is also reported, and colorants were determined. The presence of mordants, weighting materials, and colorants is discussed with reference to the embrittlement of the silk. The connection between fiber deterioration and color is discussed as well as the effects of contemporary manufacturing treatments on the present fiber condition. 

Time to Embrittlement of 0.02-inch Thick Polypropylene Sample, Sulfur Compound hours... 

Nineteen archaeological pre-Columbian textile specimens from the collections of the American Museum of Natural History and the Metropolitan Museum of Art were examined. The textiles (Huari/Tiahuanaco, lea, Paracas-Caver-nas, and Paracas-Necropolis) are described. Elemental analyses for archaeological textile and modern wool samples (C, H, N, S, and ash) are reported. Elemental analyses for samples treated with distilled H20 and CClk are compared with analyses of modern wool samples similarly treated. An unambiguous direct correlation between loss of sulfur and embrittlement could not be made. The possibilities of dating and provenance determination by technical means are discussed. 

Radiocarbon analysis is possible for dating ancient textiles only where sufficient sample is available. Unfortunately, the uncertainty in dating becomes unacceptably large with small sample size, contamination, and specimens of lesser antiquity (5). Chemical methods of dating are mainly limited to the observation that reducing the sulfur content of wool textiles appears to coincide, in some cases, with embrittlement and/or age (6). The presence of certain kinds of dyes and the manner in which they fade are sometimes used as the evidence of provenance (7). 

In this paper we discuss (1) small main-chain motions and their effect on the flow processes, (2) the embrittlement of polycarbonate, (3) the formation of microvoids from sample preparation and their effect on the brittleness of polymer glasses, and (4) the modification of the degree of brittleness of polymer glasses at the filler interface in polymer composites. 

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