Polyolefin orientation biaxial

Polyolefin foams are easier to model than polyurethane (PU) foams, since the polymer mechanical properties does not change with foam density. An increase in water content decreases the density of PU foams, but increases the hard block content of the PU, hence increasing its Young s modulus. However, the microstructure of semi-crystalline PE and PP in foams is not spherulitic, as in bulk mouldings. Rodriguez-Perez and co-workers (20) showed that the cell faces in PE foams contain oriented crystals. Consequently, their properties are anisotropic. Mechanical data for PE or PP injection mouldings should not be used for modelling foam properties. Ideally the mechanical properties of the PE/PP in the cell faces should be measured. However, as such data is not available, it is possible to use data for blown PE film, since this is also biaxially stretched, and the texture of the crystalline orientation is known to be similar to that in foam faces. 

The method also includes foimtain-flowing the mixture into a closed mold. The layer is substantially impenetrable to water and is a biaxially-oriented thermoplastic pol5mier, such as a polyolefin. 

Tables IV and V illustrate the pattern of dramatically reduced total elongations and increased embrittlement that accompanies most plastics upon cooling to cryogenic temperatures. These changes are most pronounced with the low-density, low-modulus polyolefins. A high-density, biaxially-oriented laminated polypropylene tape...

The mechanical properties of biaxially drawn PHB are intermediate between those of poly(ethylene terephthalate) and polypropylene as shown in Table 11. The biopolymer films are mechanically strong and tough, and they are transparent with good clarity. Moreover, their gas barrier properties, particularly to oxygen, are excellent and much superior to those of uncoated polyolefin films. In fact PHB and its copolymers would appear to have a promising future as packaging materials in both oriented and unoriented form. 

Polyolefins. Biaxially oriented PP/PE/EPR, films laminated with PVDC and an adhesive layer in between, were recycled by soaking the film at T = 25-140°C in a caustic solution comprising 0.1-50 wt% NaOH and 0.05-1 wt% of a wetting agent. Next, the PO layer was separated from the PVDC layer, and washed. The recovered polymers were reprocessed by blending them with virgin polymers, and subsequently re-used [25]. 

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... 

There are many applications for polyolefin compounds in the processing of pipes, tubings, and fittings from polyethylene (PE), crosslinked polyethylene (XPE), biaxially oriented polyethylene (PEO), polypropylene, and polybutylene. 

A number of processes exist for mechanically entangling or bonding a web to form a nonwoven substrate. One method that is mechanical in nature does not involve a web but rather splitting of a polyolefin film. In this process a film is extruded followed by either a discontinuous pattern cut ly knife slitting or by embossing the film followed by biaxial orientation to form a network structure. 

Entek Membranes LLG produces Teklon membranes for use as lithium-ion battery separators at their facility in Lebanon, WA. Teklon is a biaxially oriented, polyolefin membrane-containing ultrahigh-molecular-weight polyethylene (UHMWPE). 

One of the most important commercial polyolefin films is biaxially oriented... 

---