Thermoplastic Foams

Jim Throne on October 1st, 1997

Introduction In the first part of this dissertation, we considered how the kinetic energy of an incoming mass is imparted and distributed to the shock mitigating foam. We assumed that the footprint of the incoming mass, that is, its impacting area, was the same size as the foam slab. But, what happens when the incoming […]

Continue reading about Shock Mitigation in Low-Density Thermoplastic Foams Part II

Jim Throne on September 10th, 1997

Introduction Low-density foams are used in shock mitigation, cushioning, thermal insulation and vibration isolation. Typically, these foams are made by mixing gas-generating small molecules with molten polymer at elevated pressure, then rapidly dropping the pressure to allow the gas to come from solution to produce discrete bubbles or cells. In most cases, the blowing gas […]

Continue reading about Gas Migration in Low-Density Thermoplastic Foams – I

Background Low-density thermoplastic foams are frequently used as energy-absorbing foams. That is, kinetic energy from an incoming mass is mostly dissipated in the foam, resulting in little, if any, throwback or reverse propulsion of the mass from the foam. Typically, energy absorption is described in terms of the area under the foam stress-strain curve. The […]

Continue reading about Shock Mitigation in Low-Density Thermoplastic Foams Part I – Dealing with Inbound Kinetic Energy

Jim Throne on August 29th, 1997

Summary of Part I In part I, I discussed the general types of thermoplastic polyesters, noting that polyethylene terephthalate or PET is a slowly crystallizing polymer that has a melting temperature of about 260 oC. It is considered a likely candidate for many high-temperature applications, particularly since it is relatively inexpensive when compared with other […]

Continue reading about Low-Density PET Foam, Part II

Jim Throne on June 25th, 1997

Introduction The class of thermoplastic polyesters has two major subclasses – polybutylene terephthalate or PBT, and polyethylene terephthalate or PET – and two minor subclasses – PET copolymer such as Eastman’s PETG, and polyethylene naphthanate or PEN. With the exception of the copolymers, all polyesters can be crystallized, albeit very slowly when compared with polyethylenes. […]

Continue reading about Low-Density PET Foam, Part I

Jim Throne on June 14th, 1997

Since Dr. Nam Suh and his colleagues patented a technique for producing microcellular foam in 1987, there has been an international flurry of activity in this area. This technical note reviews some of the boundaries of the current and expected technologies. Microcellular Foam – A Definition In a recent publication [J.L. Throne, Thermoplastic Foams,Sherwood Publishers, […]

Continue reading about Microcellular Foams