This report presents data on Induced seismicity studies in South Carolina up to September 1979.The low level seismicity at Lake Oocassee was interrupted by a MbL 3.7 earthquake on August 25, 1979 (9:31 PM local time). This intensity VI event was the largest event to occur at Lake Oocassee and it was widely felt. Its focal mechanism revealed a large component of normal faulting.Comparison with earlier focal mechanisms and stress measurements suggests that only a thin veneer (^ 1.5 km) of the near surface rocks are highly stressed.In addition to the routine analysis of seismicity data at Monticello reservoir, we analysed in detail 180 events recorded on analog tapes between July and December 1978. This detailed analysis revealed that the seismicity is shallow (< 2 km), appears to spread in discrete jumps and occurs along existing joint and fracture planes by the diffusion of pore pressure to hypocentral depths.

Organophosphites are a versatile component of liquid PVC heat stabilizers and stabilize PVC through a variety of mechanisms. Organophosphites can decompose peroxides, replace labile chlorines on the PVC backbone, scavenge HCl (via the Arbuzov rearrangement), complex Lewis acids, and add to double bonds. This paper attempts to identify the relative contributions of these mechanisms in both model systems and flexible PVC formulations.

The initial rates of air oxidation of eight aromatic phosphites were measured at 200°C in hydrocarbon solvents. The phosphites were oxidized to the corresponding phosphates, and, in every case, a small amount of the corresponding substituted phenol was also detected. The phenolic compounds likely arose from hydrolysis of the phosphites by water generated during oxidation. In general, alkyl substitution caused a decrease in the rate of oxidation. Phosphite 7 [bis(2,4‐dicumylphenyl) pentaerythritol diphosphite] and, to a lesser extent, phosphite 6 [bis(2,6‐di‐t‐butyl‐4‐methylphenyl) pentaerythritol diphosphite] had a combination of high rate of oxidation and good resistance towards hydrolysis in the bulk state, a combination that is not usual with most commercially available phosphites (1).

The activity of various structural classes of liquid organophosphite esters has bee11 examined in flexible PVC applications. Blends of the most active phosphites have been developed as alternative heat stabilizers for PVC. These new phosphite mixtures eliminate the dependence of compounders upon mixed-metal stabilizer systems based on heavy metals such as barium and cadmium. Static oven aging tests showed the superior performance of these blends compared to that of traditional mixed-metal stabilizers. IWI'RODUCTIONhe WC industry began with the invention of plas-T ticized polyvinyl chloride by Waldo Semon of the B. F. Goodrich Company in 1933 (1). In 2001, over 12 billion pounds of flexible WC were employed throughout the world in a wide variety of commercial applications, including vinyl flooring, wall covering, roofing, pond and pool liners, film, upholstery, apparel, hose, tubing and wire insulation (2).In order to succes:sfully process flexiile vinyl compounds into finished vinyl articles by extrusion, calendering or molding, it is necessary to incorporate between one and five percent of a heat stabilizer to prevent dehydrochloilnation and discoloration of the polymer during theimal processing. The preferred vinyl heat stabilizers for most flexible PVC applications in the United States are referred to as "mixed metal" heat stabilize~s. They are complex multi-component chemical admixtures based upon combinations of alkaline earth and heavy metal salts with a variety of antioxidanrs, HCl absorbers and chelating agents. The most widely used mixed metals are based upon and referred to as barium-cadmium, bariumcadmium-zinc, barium-zinc, and calcium-zinc stabilizers (3).Early mixed metal stabilizers were solids based upon barium and cadmium soaps. For optimum performance these were used in combination with liquid phosphite esters such as biphenyl phosphite. Beginning in 1951, liquid mixed metal stabilizers were produced by dissolving the metallic components in liquid phosphite esters (4). Since 1980, phosphite esters have become an increasingly important component of liquid mixed metal stslbilizers. as formulatom have attempted to decrease or eliminate the use of toxic metal components. Today, state-of-the-art, high-efficiency mixed metal stabiliztm can contain over 5Owt?? of phosphite esters.Phosphite esters contribute to vinyl stabilization through a variety of mechanisms. They decompose hydroperoxides. react with HCl. add to double bonds, complex with Lewis acids and replace labile chlorides via Arbmv -Rearrangement (4,5). As the heavy metal components are decseased and phosphite ester components are in-ed in mixed metal stabilizers, seveml ancillary properties of the vinyl compounds improve, including heat stability, light stability, stain resistance, and plate-out resistance. The purpose of this paper is to illustrate the manner in which various phosphite esters can be used to augment or replace heavy metal components of mixed metal vinyl heat stabilizers. E x P E x u l u E m A LMatedab. WC resin (1.02 nr), dio...