An electron microscopic reinforcement criteria for carbon black masterbatches

Abstract

IntraductionThe adequate dispersion of carbon black in rubber has long been recognized as an important factor in obtaining good physical properties in black rubber masterbatches. At the present time the most widely used methods for the microscopic evaluation of carbon black dispersions in rubber are those described by Sweitaer, Hess, and Callan' and Leigh-Dugmore.2 These methods are based on the fact that in dry mixed masterbatches the major difference between two dissimilar dispersions is likely to be in the size and the number of the agglomerate black particles.' With the development of wet masterbatching methods,3.* which greatly reduces the size and quantity of carbon black agglomerates, such evaluations prove inadequate.Preliminary results indicated that simply evaluating the manner in which the carbon black was scattered or dispersed in the polymer matrix could not account for observed changes in physical properties of wet masterbatches. This electron microscopic study was made to establish and define terms relating to the reinforcement of rubber stocks by carbon black at levels below the limits of resolution of the light microscope. Experimental ProceduresSamples of the masterbatches to be studied were frozen in a Dry Iceisopropyl alcohol bath and subsequently fractured. Replicas were then made of this freshly fractured surface. Either raw or compounded stocks yielded equivalent results.The replication procedure employed was a refinement of that used by Andrews and Walsh6 to produce preshadowed positive carbon replicas. Faxfilm,6 a cellulose-based tape, was substituted for the gelatin as the intermediate negative replica in this two-stage system. This substitution greatly reduced the time necessary for replication, as gelatin requires enzymatic digestion for complete removal from the positive. Light uranium shadowing was then applied before the deposition of the carbon film. This method permits routinely resolutions of better than 100 A.Since acetone was used as the softener for the Faxfilm during repli- 27

A Novel Type of Retinoic Acid Response Element in the Second Intron of the Mouse H2Kb Gene is Activated by the RAR/RXR Heterodimer

“…1). Inspection of this DNA region for potential cis-acting regulatory sequences using the SIGNAL SCAN program (17) revealed the sequence motif AGGTCA (+576 to +581) which represents the half site of the consensus retinoic acid response element (RARE): PuG(G/T)TCA(N 1-5 )PuG(G/T)TCA (23). Furthermore, the sequence immediately upstream creates together with the above mentioned motif an everted repeat and a direct repeat, respectively, which we termed Hi-RARE (histocompatibility-intron RARE): 5′-TGACCC C GGGTCG G AGGTCA-3′ (+562 to +581).…”

Mechanical properties of silica nanoparticle reinforced poly(ethylene 2, 6-naphthalate)

“…These agglomerates can act as weak points in the material, and easily break down when stress is applied to the composite. 31 Therefore, the tensile strength of the unmodified silica nanoparticle reinforced PEN composites decreased with increasing silica content.…”

Electron Microscopy

“…By comparing systems having good, moderate and poor carbon black dispersions, they discovered that the degree of dispersion could be correlated with field emission characteristics. Using replica techniques to study the fractured surfaces of carbon black master-batches, Prestridge (373) has shown that dispersion, grinding and bonding w'ere the most important factors for evaluating the quality of the black. By applying these criteria, the performance of a tread stock made with such master-batches can be reliably predicted.…”