Paper, embrittlement

Mechanism of Temper Embrittlement, paper presented at the ASTM Symposium, Philadelphia, PA, October, 1970. 

ASTM B695, Coatings of Zinc Mechanically Deposited on Iron and Zinc, ASTM (1985) James, D. G., Mechanical Deposition —Hydrogen Embrittlement Study . Paper to IMF Annual Conf., UK (1985)... 

M. Dadfamia, P. Sofronis, I. M. Robertson, B. P. Somerday, G. Muralidharan, and D. Stalheim, Micromechanics of Hydrogen Transport and Embrittlement in Pipeline Steels, paper IMECE 2006-16325, Proceedings of the 2006 ASME IMECE, November 5-10, Chicago, IL (2006). 

Shorter fibers because of acid hydrolysis paper is weaker, and residual acid may cause long-term embrittlement. 

Sulfite paper has a relatively short life span, since residual acid will continue to hydrolyze the cellulose and cause embrittlement. Further sources of acid include aluminum sulfate (which is added together with resin to suppress bleeding or feathering of ink into the paper) and S02 and NO from the atmosphere. Much of the world s library collections and archives will soon be lost as the paper crumbles. Various deacidification treatments (e.g., with ammonia, morpholine, cyclohexylamine carbamate, or diethyl-zinc) have been proposed and tried, but at best they can only halt the process of embrittlement and cannot reverse it.14 With the move to kraft pulping, alkaline peroxide bleaching, and increasing use of precipitated calcium carbonate as a filler, the high quality papers produced today are intrinsically acid free and should also resist subsequent acidification by S02-polluted air fairly well. 

As books age. the paper of their pages becomes brittle. A relatively Ihin coating of parylene can make these embrittled pages stronger. 

The important point is that the cellulose in these alum/rosin sized papers is susceptible to acid hydrolysis, which results in a lowering of the degree of polymerisation and, eventually, to a serious reduction in the strength of fibres and to complete embrittlement of the paper. Some recent work in the writer s laboratory suggests that when alum/rosin papers are made, the hydroxonium ions which lead to the degradation are adsorbed independently of aluminium ionic species (4). 

While Barrow solved the main problem, there are other modes of degradation which must be considered. As an organic material, cellulose and paper can be easily oxidized. Very small amounts of the transition metals, compounds of iron, copper, and cobalt, under humid conditions can accelerate oxidation and embrittlement of paper. This type of degradation, as is shown later, does not show up in the dry-oven accelerated aging which Barrow used. Thus his alkaline papers, if they contained the oxidation catalysts, may not always have been permanent. 

Celluloses are similar to other linear polymeric materials in that they can possess one-dimensional order within an individual chain as well as three-dimensional order within an aggregate of chains. Increments in the levels of order occur during the isolation of native celluloses and also as a result of exposure to conditions that promote molecular mobility, such as elevated temperatures and immersion in plasticizing fluids. These increments generally result in embrittlement of the cellulosic materials. Similar effects are expected to occur upon aging of cellulosic textiles and papers over extended periods, and may be accelerated by hydrolytic cleavage of cellulosic chains. The implications of these effects for conservation practices, both with respect to recovery of function as well as in the assessment of deterioration, are reviewed. 

Figure 2. The effect of beating on folding endurance of paper, with paper embrittlement on aging indicated...

Tjlemental sulfur has been proposed (1,2) for a wide range of applica-tions in the civil engineering field. In virtually all of these applications it has been necessary to modify the sulfur with additives designed to stop the embrittlement which occurs with pure elemental sulfur. Thus if pure elemental sulfur is heated to 140 °C and then cooled to ambient temperature, monoclinic sulfur (S/s) is instantaneously formed (3), followed by a reversion to orthorhombic sulfur (Sa) which is almost complete in about 20 hr (Figure 1). Many additives have been proposed to modify elemental sulfur, nearly all of which fall under the heading of polymeric polysulfides or, alternatively, substances which may react with elemental sulfur to give in situ formation of polymeric polysulfides. In a previous paper (3), we reviewed the various substances used as addi-... 

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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