Aging, polymers

There are no known practical peroxide cure systems for the PO—AGE polymers. Apparentiy the peroxide attacks the polymer backbone at a rate that is unfavorably competitive with the cross-linking rate. A typical sulfur cure system consists of zinc oxide [1314-13-2] tetramethylthiuram mono sulfide (TMTM), 2-2-mercaptobenzothiazole [149-30-4] (MBT), and sulfur. A sulfur donor cure system is zinc oxide, di-o-tolylguanidine [97-39-2] (DOTG) and tetramethylthiuram hexasulftde. 

Table 1. Formation of aged polymer under reflux and nonreflux conditions with 0.05 M Pu at 105°C...

Enhancement of depolymerization rates for aged polymer (polymer with high degree of PuC>2 character (13) were observed... 

Ljungberg, N. and Wesslen, B. 2003. Tributyl citrate oligomers as plasticizers for polyjlactic add) Thermo-mechanical film properties and aging. Polymer 44 7679-7688. 

Materials and their development are fundamental to society. Major historical periods of society are ascribed to materials (e.g.. Stone Age, Bronze Age, Iron Age, Steel Age, Polymer Age, Silicon Age, and SUica Age). However, scientists will open the next societal frontiers not by understanding a particular material, but by optimizing the relative contributions afforded by a combination of different materials. 

The solubility of ethylene in freshly prepared polyethylene, and its diffusion out of the latter were studied in relation to the formation of explosive ethylene-air mixtures in storage. Explosive mixtures may be formed, because the solubility of ethylene in its polymer (e.g. 1130 ppm w/w at 30°C) considerably exceeds the concentration (30 ppm at 30°C) necessary to exceed the lower explosive limit above the gas-containing polymer in closed storage, and the diffusion coefficient is also 30% higher than for aged polymer samples. 

A high-quality metal cross-linked polymer is fortified for long-lasting durability. A metal cross-linked floor finish is made from space-age polymer and designed to provide a highly durable floor finish with... 

Figure 17. Chronology of improvement in light transmission of glasses over periods of history leading to introduction of photonics technology in the information age. Polymer protection of glass surfaces is an essential present feature.

Polycarbonates. The polycarbonates surfaced in the 1950s, so they are middle-aged polymers. They are made in a condensation polymerization process. The reactants are either Bisphenol A and phosgene or Bisphenol A, phosgene, and phenol. Since Bisphenol A is a derivative of phenol, the building block is the same in either case—phenol. The polycarbonate based on Bisphenol A has the best balance of properties. If you look hard, you can see the monomers in Figure 24—7. ... 

We saw in Section 13.6 that hydrolysis and subsequent polymerization of aqueous metal cations can lead to the precipitation of gels. In the case of Fe(H20)63+ in mildly acidic solutions, the polymerization sequence of Eqs. 13.25 and 13.26 and Fig. 13.6 first reversibly forms cationic colloidal spherules, 2-4 nm in diameter, with the structure of 7-Fe0(0H) [double chains of Fe(0,0H)6 octahedra] on a timescale of about 100 s. These lose H+ and harden over several hours and then, over several days, form aged polymer rods, then rafts, and ultimately, after several months, needles of solid goethite [cc—FeO(OH)].1,2 Thus, aging is an important feature of hydrolytic polymerization. 

These polar transformation products and sulfur oxides (SO2, SO3) arising in the ultimate stages of the transformation process are formed in trace amounts in the aged polymer matrix. Volatile products may be sources of undesirable organoleptic problems. This limits the use of organic thiocompounds in odor-sensitive applications. Organic S-proto-nic acids 85, 86 deactivate basic stabilizers (HAS). The peroxidolytic effect of 85, 86 is reduced in the presence of some antiacids or fillers, e.g., calcium carbonate. 

Apparently, there is less free volume in the aged polymer network. Any water coming into the aged network would tend to swell the polymer because there are simply less vacant sites in the distribution of free volume. In short, there is more polymer-solvent interactions as water diffuses into an aged epoxy network. 

L. Buisson, S. Ciliberto, and A. Garcimartin, Intermittent origin of the large violations of the fluctuation-dissipation relations in an aging polymer glass. Europhys. Lett. 63, 603 (2003). 

Dilute solution viscosity, aged polymer + soluble, - insoluble ... 

Keywords Charge storage properties Commodity polymers Corona charging Electret materials High performance polymers Physical aging Polymer films... 

Figure 14.5. DSC thermograms for aged polymer blends (a) polyvinylchloride/poly isopropyl methacrylate, immiscible blend, aged at a temperature of 60°C, and (b) polyvinyl chloride/polymethylmethacrylate, miscible blend, aged at 80°C. Time of aging, t in hours, is shown alongside each curve. Broken lines represent the un-aged samples for comparison.

Moisture is a well-known plasticizer for macromolecules (14). Specifically, water penetrates into an epoxy network and can lower the glass temperature of the resin (15). In this report, moisture has for the first time been utilized as a probe to characterize denslfIcatlon process during epoxy aging. Also, using the same rationale, heavy water diffused Into the epoxy resin Is used to study the Interactions of moisture with the aging polymer by hydrogen-2 (deuterium) NMR spectroscopy. 

Resistance to biological aging polymer for long-term implantation should have good biological stability. 

Spet/. Ci.. Improving The Precision Rubber Te.st Methrxis Part 2 Aging. Polymer Testing. I.K 2. 9 (1994). 

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