Effect of Introducing Long Chain Branching on Fiber Diameter and Fiber Diameter Distribution in Melt Blowing Process of Polypropylene

In the melt blowing process, the molten polymers extruded from nozzles are elongated by high-velocity and high-temperature air flow. In this study, with the aim of stabilizing the melt blowing process for producing nonwoven webs with fine diameter fibers, the effect of the control of polymer rheology by the introduction of either low melt flow rate (MFR) polypropylene (PP) or long chain branched PP (LCB-PP) to regular high MFR PP was investigated. Introduction of low MFR PP into regular PP increased shear viscosity and fibers of larger diameter were produced in the melt blowing process, while introduction of low MFR LCB-PP suppressed the elongational viscosity reduction with the increase of strain rate, and eventually spinning was stabilized. It was found that the blending of an optimum amount of LCB-PP to regular PP caused the stabilization of the melt blowing process. As a result, the formation of nonwoven webs consisting of fine fibers of rather uniform diameter distribution could be achieved.

EXPERIMENTAL AND NUMERICAL STUDIES OF STRESS FIELDS OF A BRANCHED POLYBUTADIENE IN A FLAT DIE

There is a growing body of laboratory and industrial evidence that the viscoelastic characteristics of molten polymers contribute to improving the efficiency of polymer extrusion molding. Understanding the behavior of molten polymers in manufacturing processes requires the qualitative and quantitative determination of flow kinematics and stress distribution. The optimization of the forming processes and the final properties of the transformed products requires the mastery of high-performance simulation models. So, it is necessary to be able to correctly describe the non-linear rheological behavior of the molten polymers by appropriate constitutive equations and a relatively easy implementation in computer codes. In this work, experimental and numerical studies are performed to investigate the rheological behavior of branched polybutadiene into a two-dimensional channel of a capillary rheometer. The stress field in the flow was analyzed with a birefringence device to identify areas of stress concentration and to show its progress in different areas of the extrusion die. Also, we obtain the stress field with numerical simulations using ANSYS Fluent 16.0 as a solver and Gambit as a mesh generator. The rheological model adopted in the numerical study is the power-law or Ostwald-de Waele model.

Innovative Farming and Building Materials from Recycled Plastics

Despite the ban on use of plastic paper bags, large amounts of plastic litter still exist in our environment. Plastic bottles form a greater percentage of the litter. The growth of the consumer market for cosmetics and soft drinks which are usually packaged in plastic containers continues to give rise to plastic pollution. To maintain the quality of the environment while achieving sustainable development plastic litter could be viewed as raw and innovative materials for making new items. Plastics can be recycled and made into furniture, ornamental products, and building blocks among others. This paper describes how recycling plastic waste into products of plastic sheets and blocks is conducted for multi-purpose use. The resultant sheets and blocks can be designed to have slots and extensions on the edges such that they allow interlocking the same way concrete interlock blocks work. The sheets and blocks can be used to make furniture, office partitions, and interior design. The sheets for furniture making can be craftily decorated with beads while they are still in molten state to produce ornamental furniture. This can be achieved through arranging beads in molds before introducing the molten polymers into them. The plastic blocks and sheets can also be used to make swimming pools and fish ponds. Heating temperature and oxidation should however be monitored to prevent degradation of the polymers. The resultant products are durable, attractive and affordable.

Evaluation of the properties of plastic-metal interfaces directly bonded via injection molding

Plastic and metal can be directly bonded via insert injection molding by creating surface porous structures with 30–50 nm sizes on metal surface. Molten polymers can be penetrated into the small pores created on metal surface in the short molding process, and strong joint can be obtained. The bonding mechanism of aluminum alloy (Al5052) and polyphenylene sulfide (PPS) with two different surface features of Al5052 was studied. Scanning transmission electron microscopy (STEM) was performed to investigate the interfacial structures in terms of elemental distributions and three-dimensional (3D) inter-connectivity of the pores on the Al5052, and the chemical reaction which takes place during the joint process was investigated by X-ray photon spectroscopy (XPS). The properties of the joint interfaces were evaluated to discuss the effect of interfacial structures on the joint properties.