Abstract: A method and apparatus for controlling the density of a foam. The method involves measuring the electrical conductivity of a foam wherein the electrical conductivity of the foam varies with the density thereof and adjusting the density of the foam in response to the measured electrical conductivity to prepare a foam having a desired density. The apparatus comprises means for generating and applying a foam, said means being connected by an enclosed pathway. Located within the enclosed pathway is an electrical conductivity sensor. The conductivity sensor is electronically connected to a translation means. The conductivity sensor provides an electrical signal, related to conductivity of the foam, to the translation means. The translation means is connected to a gas flow controlling means.

Abstract: Improved shaft seal is provided wherein generally radially extending distendable diaphragms are used to adjust the sealed gap. A flushing lubricant is provided. The seal is particularly suited for use in gear pumps handling viscous materials such as heat plastified thermoplastics.

Abstract: A process for producing polymers or copolymers of ethylene, in which ethylene, optionally together with one or more copolymerizable compounds, is polymerized at a pressure above 50,000 kPa and a temperature of between 100.degree. and 400.degree. C. in the presence of an initiator, using an autoclave reactor and a tubular reactor connected in series with said autoclave reactor. The monomeric mixture in the presence of the initiator is passed first into a stirred autoclave, in which it is partially polymerized. Thereafter the reaction mixture from said autoclave, is passed through a heat exchanger, cooled to a pre-determined value, and then subsequently passed to a non-cooled tubular reactor, in which the further polymerization is carried out under adiabatic conditions.