1. Introduction
A preliminary review of the trends in woven polypropylene bags fabrications was done giving some highlight on the simulation, optimization and improvements reported in the open literature.
2. About polypropylene ,
Polypropylene (PP) is a linear hydrocarbon polymer, produced by polymerization of the propylene (alkene). It is a polymer manufactured form addition from the monomer propylene, by means of the so-called Ziegler-Natta polymerization (see figure besides the text) using an organometallic compound, known as a Ziegler-Natta catalyst. The two chemists who first developed this process awarded the Nobel Prize in 1963 (Karl Ziegler and Giulio Natta).
It belongs to the family of the polyolefins or saturated polymers, like polyethylene (acronyms HDPE, LDPE, L/LLDPE) and polybutene (PB). The British Plastic Federation published in their Plastipedia an excellent summary of the key features of this polyolefin, some of whose aspects are here summarized but the reader is referred to the original source for deeper orientation.
Its versatility makes it available for many applications in almost all end-use markets for plastic, because it can be manufactured in different structural forms in applications like packaging and labeling, textiles, plastic parts and reusable containers, as shown in figure besides the text (adapted from The Essential of Chemical Industry):
Mouldings (automotive and sailing components, etc)
Fibers (carpets, bailing twine, clothing, etc.)
Tape (replaced jute)
Film (biaxially oriented film)
Foam (structural foam and low density packaging)
2.1. Chemical structure
When polymerized, the propene molecule, that is asymmetrical, and dependending on the position of the methyl groups can form three basic chain structures: two of them are stereoregular (isotactic and syndiotactic) while the other is irregular and is called atactic, as shown in the figure besides this text (adapted from The Essential of Chemical Industry).
2.2. Chemical and physical properties
It is a translucent white; semi-rigid and mechanically rugged material; with excellent electrical resistance at higher temperatures and outstanding resistance to chemical solvents, acids and alkalis; as well as good fatigue and heat resistance. Is a stress-free and cracking-free material
Even being similar to other polyolefins, like polyethylene, it has a lower density, higher softening point and higher rigidity and hardness and does not melt below 160 C.
Polypropylene is similar to polyethylene, especially in solution behavior and electrical properties.
2.3. Mechanical properties
Polypropylene specific gravity ranges between 0.895 and 0.92, being the lowest density commodity plastic. Its Young's modulus lies between 1300 and 1800 N/mmÂ².
Polypropylene exhibits good tough and flexibility, in particular if ethylene was used as copolymer and has also good resistance

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