Polyolefin foams manufacturing process

Atlanta, Ga., 26th-30th April 1998, p. 1842-9. 012 PRODUCT AND PROCESS DEVELOPMENTS IN THE NITROGEN AUTOCLAVE PROCESS FOR POLYOLEFIN FOAM MANUFACTURE Eaves D E Witten N Zotefoams pic (SPE)... 

FIGURE 1.62 Block diagram of polyolefin foam manufacture by extrusion process. 

The commercially available ferroelectret film is based on polyolefin foam manufactured in a continuous biaxial orientation process, followed by an expansion process to adjust the mechanical and the piezoelectric properties (Fig. 2 left). The equivalent circuit of a ferroelectret film sensor consists of a current source in parallel to the sensor capacitance (Fig. 2 right). The sensor capacitance Cp follows fromCp = eoeA/s, where sq is the permittivity of vacuum, e is the dielectric constant of the ferroelectret foam, A is the electrode area, and s is the thickness of the film. With a typical thickness of S = 70 pm and a dielectric constant of e = 1.5, the sensor capacitance is 19 pF/cm, a small capacitance in comparison to other piezoelectric sensor elements. The ferroelectret sensor element produces a current i(t) when a force F(t) is applied to the sensor element, according to i t) = where the dot... 

A review is presented of the nitrogen autoclave process for the manufacture of crosslinked polyolefin foams. Process and product developments over the last few years are summarised and future possibilities are described. Process developments include use of higher temperatures and pressures to produce foams having densities as low as 10 kg/cub.m. Product developments include foams based on HDPE/LDPE blends, propylene copolymers and metallocene-catalysed ethylene copolymers. The structure and properties of these foams are compared with those of foams produced by alternative processes. 5 refs. 

Electron Beam Process in the Manufacture of Polyolefin Foams... 

A cross-linked polyolefin foam sheet is produced by two methods using chemical cross-linking and by two methods of radiation cross-linking. The two well-established manufacturing processes for polyolefin foams using radiation cross-linking are the Sekisui process and Toray process. The differences between these two manufacturing methods are mainly in the expansion step, which is almost always done separately. However, the... 

Flow diagram of the manufacturing process for polyolefin foams using radiation cross-linking. 

Polyolefin foams are manufactured in a variety of processes and in low density (25-250 kg/m ) or high density (250-700 kg/m ) versions. Foamed polyolefins have a long tradition in research, production and application. The consumption in 1995/96 all over the world was more than 190000 tonnes, including almost 18000 tonnes of expandable polyolefin beads. Polyolefin foams are expected to continue growing at a faster rate than other plastic foams. A major part of the polyolefin foams is based on polyethlyene (PE) and its copol)uners. Nearly 50% of the PE-based foam is partly cross-linked material. 

Electron beam processing in the manufacture of polyolefin foams is another important technical application, whereby (mostly) polyethylene is irradiated in the... 

Patent Number US 5883145 A 19990316 CROSSLINKED FOAM STRUCTURES OF POLYOLEFINS AND PROCESS FOR MANUFACTURING... 

Patent Number EP 702032 A2 19960320 CROSSLINKED FOAM STRUCTURES OF ESSENTIALLY LINEAR POLYOLEFINS AND PROCESS FOR MANUFACTURE... 

---