GPC appearance volumes have been determined for a series of linear polyethylene, polystyrene, and polybutadiene fractions (Mw/Mn < 1.1) in trichlorobenzene at 130°C. and for the latter two series in tetrahydrofuran at 23°C. A polymer‐type independent relationship between appearance volumes and the equivalent hydrodynamic radii of the polymer molecules has been demonstrated. The equivalent hydrodynamic radius is calculated from intrinsic viscosity data. It is proposed that this relationship can be used to construct a universal GPC calibration curve for polymers that assume a spherical conformation in solution. Methods for applying the universal curve to the determination of molecular weight averages and molecular weight distribution are described. In addition, a method is outlined by which the universal calibration curve can be empolyed for determining number‐average Mark‐Houwink constants from polydisperse samples.
A study is reported of the degradation of irradiated methacrylate polymers, the formation and trapping of free radicals, and their electron spin resonance (e.s.r.) spectrum. Several different radicals are apparently formed and it seems necessary to assume that they are formed by different mechanisms. This is also suggested by a number of observations of main chain degradation and the ratio of chain scission to ester removal for several methacrylate polymers. It is probable that several mechanisms of degradation and radical formation are operative and the one which predominates is dependent on the pendant ester structure.
The effects of operational variables on calibration of GPC are reported. Variables examined include (1) temperature and solvent changes, (2) sample concentration, (3) injection time, and (4) flow rate. Each of these variables significantly affected molecular weight averages calculated from GPC data. The causes and methods of minimizing the effects produced by the individual variables are discussed.
Available information defining the state of the art of encapsulation materials and processes for terrestrial photovoltaic devices and related applications were collected and analyzed. Based on criteria of properties, processability, availability, and cost, candidate materials were identified which have potential for use in encapsulation systems for low-cost, long-life terrestrial photovoltaic arrays manufactured by automated, high-volume processes. The study was in support of the Encapsulation Task of the ERDA Low-Cost Silicon Solar Array (LSSA) Project, managed by JPL. The criteria for consideration of the encapsulation systems were based on the LSSA goals for arrays with a lifetime of over 20 years high reliability, an efficiency greater than 10 percent, a total array price less than $500/kW, and a production capacity of 5 x 10-> kW/yr. Published and unpublished information relating to encapsulation systems and materials properties was collected by searching the literature and appropriate data bases (over 1300 documents were selected and reviewed) and by personal contacts including site and company visits. A data tabulation summarizing World experience with terrestrial photovoltaic arrays (50 installations) is presented in the report. None of the encapsulation materials used meets all of the LSSA criteria (particularly cost), but some have performed well. R. B. Bennett. F. A. Sliemers led the polymer-chemist effort with contributions from R. E. Sharpe, G. P. Nance, and A. R. Bunk. R. D. Igou led the information searching and retrieval efforts. E. L. Briich managed the information system for the study and J. J. Breslin helped with the reporting; their assistance is certainly appreciated.
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