A note on brittle crack deceleration in a structural steel

The deceleration of a brittle crack in a steel is attributed to plastic deformation developed around the crack. The investigation shows that a ductile fibrous crack stops suddenly, but a brittle cleavage crack does sluggishly.

---

Résumé La décélération d'une fissure fragile dans un acier est attribuée à la déformation plastique qui se développe autour de cette fissure.L'étude montre qu'une fissure fibreuse et ductile s'arrête brutalement tandis qu'une fissure fragile et de clivage s'arrête lentement.

     

Homo- and copolymerization of ethylene and propylene with a soluble chromium catalyst

Polymerization of ethylene and propylene was carried out with a soluble $\text{Cr(C}{}_{17}\text{H}{}_{35}\text{COO}\text{)}{}_3\text{AlEt}{}_2\text{Cl}$ catalytic system in toluene. The system was found to be active only for ehtylene polymerization. From e.s.r. measurements of the catalytic system combined with some qualitative experiments, the active species was determined to be Cr²⁺. The reason why it should be incapable of polymerization of propylene was also discussed. The catalytic system showed some activity for ethylene-propylene copolymerization to give a random copolymer with a narrow molecular weight distribution.     

Nonaqueous titrimetric analysis of sulfuric and alkylbenzene sulfonic acids in detergent intermediates

A single differential nonaqueous titration method is presented for the analysis of sulfuric and alkylbenzene sulfonic acids in a detergent intermediate material. The organic and sulfuric acids in the sample were quantitatively titrated potentiometrically with standard cyclohexylamine solution. With certain specified sample compositions, approximate sulfuric acid determinations may be made without sample weighing or the use of standardized titrant. The titration is based upon the ratio of the first and second end points of the differential titration curve. Because of its simplicity, the latter method adaption is especially useful for routine control type analyses.     

Determination of water content of granulated detergents

A quick analytical procedure was described for the determination of water content of granulated detergents. A constant weight loss of sample was obtained within 5 min by microwave drying. The weight loss agrees with the water content by the modified distillation method. The coefficient of variation was 0.7%.     

Syntheses and polymerizations of macromers

Summary Living poly(tetrahydrofuran) (PTHF) was coupled with sodium p-vinylbenzyloxide quantitatively to prepare a macromer of p-vinylbenzyloxyl poly(tetrahydrofuran) (VBO-PTHF). The radical polymerization of the macromer with AIBN was performed. From the GPC measurement the conversion of the macromer to poly-macromer was shown to be high percentage, but the degree of polymerization of poly-macromer was much lower than that expected in the case of regular monomers such as styrene.