Raw Materials Plastics

Polypropylene (PP), also known as polypropene, is a thermoplastic polymer used in a wide variety of applications including packaging and labeling, textiles (e.g., ropes, thermal underwear and carpets), stationery, plastic parts and reusable containers of various types, laboratory equipment, loudspeakers, automotive components, transvaginal mesh and polymer banknotes. An addition polymer made from the monomer propylene, it is rugged and unusually resistant to many chemical solvents, bases and acids.

Polypropylene has a relatively slippery “low energy surface” that means that many common glues will not form adequate joints. Joining of polypropylene is often done using welding processes.

The density of PP is between 0.895 and 0.92 g/cm³. Therefore, PP is the commodity plastic with the lowest density. With lower density, moldings parts with lower weight and more parts of a certain mass of plastic can be produced. Unlike polyethylene, crystalline and amorphous regions differ only slightly in their density. However, the density of polyethylene can significantly change with fillers.

The melting point of polypropylene occurs at a range, so a melting point is determined by finding the highest temperature of a differential scanning calorimetry chart. Perfectly isotactic PP has a melting point of 171 °C (340 °F). Commercial isotactic PP has a melting point that ranges from 160 to 166 °C (320 to 331 °F), depending on atactic material and crystallinity. Syndiotactic PP with a crystallinity of 30% has a melting point of 130 °C (266 °F). Below 0 °C, PP becomes brittle.

The thermal expansion of polypropylene is very large, but somewhat less than that of polyethylene.

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Mechanical properties
Polyethylene is of low strength, hardness and rigidity, but has a high ductility and impact strength as well as low friction. It shows strong creep under persistent force, which can be reduced by addition of short fibers. It feels waxy when touched.

Thermal properties
The usefulness of polyethylene is limited by its melting point of 80 °C (176 °F) (HDPE, types of low crystalline softens earlier). For common commercial grades of medium- and high-density polyethylene the melting point is typically in the range 120 to 180 °C (248 to 356 °F). The melting point for average, commercial, low-density polyethylene is typically 105 to 115 °C (221 to 239 °F). These temperatures vary strongly with the type of polyethylene.

Chemical properties
Polyethylene consists of nonpolar, saturated, high molecular weight hydrocarbons. Therefore, its chemical behavior is similar to paraffin. The individual macromolecules are not covalently linked. Because of their symmetric molecular structure, they tend to crystallize; overall polyethylene is partially crystalline. Higher crystallinity increases density and mechanical and chemical stability.

Most LDPE, MDPE, and HDPE grades have excellent chemical resistance, meaning they are not attacked by strong acids or strong bases, and are resistant to gentle oxidants and reducing agents. Crystalline samples do not dissolve at room temperature. Polyethylene (other than cross-linked polyethylene) usually can be dissolved at elevated temperatures in aromatic hydrocarbons such as toluene or xylene, or in chlorinated solvents such as trichloroethane or trichlorobenzene.

Polyethylene absorbs almost no water. The gas and water vapor permeability (only polar gases) is lower than for most plastics; oxygen, carbon dioxide and flavorings on the other hand can pass it easily.

PE can become brittle when exposed to sunlight, carbon black is usually used as a UV stabilizer.

Polyethylene burns slowly with a blue flame having a yellow tip and gives off an odour of paraffin (similar to candle flame). The material continues burning on removal of the flame source and produces a drip.

Polyethylene cannot be imprinted or stuck together without pretreatment.

Electrical properties
Polyethylene is a good electrical insulator. It offers good tracking resistance; however, it becomes easily electrostatically charged (which can be reduced by additions of graphite, carbon black or antistatic agents).

Optical properties
Depending on thermal history and film thickness PE can vary between almost clear (transparent), milky-opaque (translucent) or opaque. LDPE thereby owns the greatest, LLDPE slightly less and HDPE the least transparency. Transparency is reduced by crystallites if they are larger than the wavelength of visible light.

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ROTATIONAL MOULDING:
One of the most important application fields is the rotomoulding technology, a very young and with extraordinary growth potential , which makes use of plastic materials only in powder shape. The universally employed material is today the polythene powder(mostly linear), used to produce large hand-made for different applications, such as agricultural silos, boats and surf boards, furnitures, pottery, water tanks, road barriers and signs, building tubes, etc.

We trade a different kind of polyethylene powder. The products are of different MFI and density and they can be supplied natural or with coloured pigments on request.

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MASTERBATCHES AND COMPOUNDING:
In these two fields there is a constantly growing demand for plastic powders. In fact, it is necessary, in both the master and compound production, to obtain high degrees of dispersion and homogeneization of the components such as resins, pigments, additives.

The technological evolution of the blending and compounding plants, and the use of plastic powders with controlled particle size, guarantee these results. The family of this kind of items, includes a wide range of thermoplastic polymers both “ commodity types” and “specialities”.

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