3D FEM Study of the Flow Uniformity of Flat Polypropylene Film/Sheet Extrusion Dies

Coat-hanger dies are widely used in the extrusion of polymer sheets and films. However, when designing the flat film/sheet extrusion dies manufacturing companies still facing difficulties in achieving the flow uniformity of the polymer melt. This affects the product quality and tool life. This study examines the existing extrusion die design which is used in in the industry in Kazakhstan for polypropylene sheet production and proposes better geometry of a die. These die geometries will be tested for flow uniformity in terms of velocity and pressure at the outlet.

Effects of Blade Tip Profile on In-Plane Tensile Properties of Wedge-Notched Polypropylene Sheet

In this work, the tensile characteristics of a 0.2-mm-thick polypropylene (PP) sheet subjected to indentation with virgin and blunt knives (apex angle, α=42◦; tip thickness, w=6 and 20 μm, respectively), were experimentally investigated. To determine the effect of mechanical condition, such as the notched depth and the profile of the root surface, on the breaking behavior of the half-cut PP specimen, the tensile testing of the half-cut specimen was carried out by varying the indentation depth and tensile velocity. By the experiments, the breakage behavior of the scored (half-cut) zone was determined by varying the indentation depth, tip thickness of the blade, and elongation rate. A kind of crazing or cracking by the blunt knife decreased the tensile resistance and burr elongation for an indentation depth larger than 0.9, whereas the work hardening by the blunt knife increased these properties for an indentation depth less than 0.8. When a blunt knife was used at a high elongation rate larger than 0.01 s-1, the half-cut zone of the PP sheet exhibited brittle fracture, i.e., the tensile resistance and burr elongation decreased.

Thermal Performance of Pulsating Heat Stripes Built With Plastic Materials

A low-cost, flexible pulsating heat pipe (PHP) was built in a composite polypropylene sheet consisting of three layers joint together by selective laser welding, to address the demand of heat transfer devices characterized by low weight, small unit thickness, low cost, and high mechanical flexibility. A thin, flexible, and lightweight heat pipe is advantageous for various aerospace, aircraft, and portable electronic applications where the device weight, and its mechanical flexibility are essential. The concept is to sandwich a serpentine channel, cut out in a polypropylene sheet and containing a self-propelled mixture of a working fluid with its vapor, between two transparent sheets of the same material; this results into a thin, flat enclosure with parallel channels hence the name “pulsating heat stripes” (PHS). The transient and steady-state thermal response of the device was characterized for different heat input levels and different configurations, either straight or bent at different angles. The equivalent thermal resistance was estimated by measuring the wall temperatures at both the evaporator and the condenser, showing a multifold increase of the equivalent thermal conductance with respect to solid polypropylene.

Mechanical, Degradation and Water Uptake Properties of Fabric Reinforced Polypropylene Based Composites: Effect of Alkali on Composites

In this study, a fabric was manufactured consisting of 50% pineapple, 25% jute and 25% cotton fibers by weight, to make composites using polypropylene (PP) as a matrix material. We used compression molding technique, which kept 30% of the fabric content by total weight as the composite. The tensile strength (TS), tensile modulus (TM), elongation break (Eb%), bending strength (BS) and bending modulus (BM) were investigated. From analyzed data, it was found that the composite values of TS, TM, Eb%, BS and BM were 58 MPa, 867 MPa, 22.38%, 42 MPa and 495 MPa, respectively. The TS, TM, Eb%, BS and BM of the neat polypropylene sheet were 28 MPa, 338 MPa, 75%, 20 MPa and 230 MPa, respectively. Due to fabric reinforcement, composite values for TS, TM, BS and BM increased 107%, 156%, 110% and 115%, respectively in comparison with a polypropylene sheet. A water absorption test was performed by dipping the composite samples in deionized water and it was noticed that water absorption was lower for PP-based composites. For investigating the effect of alkali, we sunk the composites in a solution containing 3%, 5% and 7% sodium hydroxide alkali solutions by weight, for 60 min after which their mechanical properties were investigated. A degradation test was carried out by putting the samples in soil for six months and it was noticed that the mechanical properties of fabric/PP composites degraded slowly.