Dielectric relaxation in a styrene-acrylonitrile copolymer during and after its polymerization

Abstract

rela,,:ation in plasticized copolymers of styrene and acrylonitri le is s tudied dUring ~helr formatIOn as well as in t he fully polymerized copolymers b y measurements of dlelectn ? .constant and loss fa ctor at several frequencies from 100 cis to 100 kc/s . In t he p? lyme~'lzl!1g nuxture, t here occur, at an early stage of the reaction, sigmo id decrea es in t h e dlelectl'lc co nstan t at each frequency, accompanied by maxima in t he loss fa cto r when t hese vanables are plotted as ~ fun ction o~ reaction t im e. These changes are interpreted as res ultll1~ from the relaxatl?n of the mtnle groups. The. electrical properties of t he ful ly polymeI.lzed copolymer, as It goes .throu~h Its glass tran;ntIOn , are in semiquan t itativ e agreement ,,?th those of the polymerIZing mIXture at t he stao-e of t h e reaction referred to demonstratlllg the Occurrence of similar phenomena in each ~ase.'

Fringe capacitance of a parallel-plate capacitor

“…As a 'by-product' of the method the relative permittivity E, of perspex was found to be 2.70 (k0.05) at 5 MHz and this is consistent with data from Nakajima et ul (1957). The corresponding value for PTFE is 2.00 (k0.05) which agrees with published data (Ehrlich 1953). However, it is felt that the latter experiments do not offer conclusive proof that the dielectric disc of larger area is filled by all the fringe field, and other factors could be investigated.…”

Rapid measurements of the insulation resistance of capacitors

“…The current iL is 0pp0Je4 by the reference bias current ib ( Figure 3) which is itself ,..opartional to V, such that k·V i.,= a;and at balance Therefore and which may be rewritten as (5) or (6) The factors RuCu and ReCe may be replaced by their equivalent timo-constants, Tu for the unknown and Te for the coupling capacitor, and the equations (S) and (6) can therefore be simplified with respect to low or high values of unknown capacitors.…”

Reactivity Ratios and Sequence Distribution Characterization by Quantitative 13C NMR for RAFT Synthesis of Styrene‐Acrylonitrile Copolymers

“…Styrene‐acrylonitrile (SA) copolymers, due to their outstanding chemical, thermal, mechanical, and optical properties and their easy processability, are found in a wide range of industrial applications . Therefore, this monomer pair has been one of the most studied from the early days of polymer science . Prior to the introduction of controlled radical polymerization, free radical polymerization (FRP) was used to synthesize SA copolymers and a number of scientists have studied the kinetics of SA copolymerization both in bulk and in a variety of solvents .…”