New MDO Medium Molecular Weight High Density Polyethylene Films

Abstract

Machine Direction Orientation (MDO) can enhance many film properties such as tensile strength, elongation, stiffness, optics (haze and gloss) and water vapor transmission rate (WVTR). Although MDO can be used with high molecular weight-high density polyethylene (HMW-HDPE) resins, few or no medium molecular weight-high density polyethylene (MMW-HDPE) films have previously been available due to MDO processing issues, namely stretch resonance, which is a phenomena where the film stretches unevenly. Thus it has not been possible to take advantage of the better barrier properties and improved process capabilities of the MMW resin. This paper describes a new line of machine direction orientable MMW-HDPE films that are now commercially available; these were made possible through the use of a proprietary processing aid (PA) that overcomes the stretching problem previously encountered with MMW-HDPE resins. Physical property data for two MDO MMW-HDPE films are presented.

Progress in the Preparation and Application of Breathable Membranes

“…Next, it is stretched between rolls at controlled speeds and temperatures, with the fast roll moving 2.5 to 10 times quicker than the slow roll, ensuring continuous stretching. The next step is the annealing hot roll, which achieves stress relaxation by holding the film at a high temperature for a period of time—this step provides dimensional stability—and finally, it is cooled at room temperature prior to winding [ 38 ]. Blown film extrusion allows for precise control over film thickness and air permeability by adjusting various parameters like extruder temperature, screw speed, blow ratio, and draw ratio, which produce effects on the film’s mechanical [ 39 ] and optical properties [ 40 ].…”

Photostabilization of polyethylene by a hindered amine light stabilizer in blooming conditions and impact of MDO processing

“…At the macromolecular scale, it causes the initial spherulitic morphology to progressively transform into a fibrillar morphology oriented along the machine direction (MD) as the drawing rate is increased [17]. Accordingly, the polymer optical (increase in gloss and transparency, decrease in haze) [18,19,20], mechanical (increase in the Young's modulus along the machine and transverse directions, as well as stress at break along the MD) [18,19,20,21] and barrier (gas, water vapor) [18,21] properties are enhanced. MDO technology was developed 50 years ago [22] and is widely used at the industrial scale.…”

“…MDO technology was developed 50 years ago [22] and is widely used at the industrial scale. However, its effect on polymer properties remains confidential in the scientific literature [17,18,19,20,21,23,24], and its consequences on stabilizer solubility and polymer photoaging have never been considered thus far.…”