--Polystyrene another named styrofoam is a high volume world-wide consumed plastic. It is used in many different formulations. Styrofoam is noted for its sparkling clarity, hardness, low water absorption, extreme ease of processing general purpose PS, excelent colorability, dimensional stability, and relatively low cost. This amorphous TP often competes favorably with higher priced plastics.
--In its basic crystal PS form it is brittle, with low heat and chemical resistance, poor weather resistance. High impact polystyrene is made with butadiene modifiers that provides significant improvement in impact strength and elongation over crystal polystyrene accomponied by a loss of transparency and little other property improvement.
(Dominick V. Rosato,Donald V. Rosato,Matthew V. Rosato, Plastic product material and process selection handbook, page 63)
Polypropylene (11:15 am 23.04.2011)
--Polypropylene is a thermoplastic material that is produced by polymerizing propylene moleculesi which are the monomer units, into very long polymer molecule or chains. There are number of different ways to link the monomers together but PP asa commercially used material in its most widely used form is made with catalyst that is a semi-crystalline solid with good pysical, mechanical and thermal properties. Another form of PP, produced in much lower volumes as a byproduct of semicrystalline PP production and having very poor mechanical and thermal properties, is a soft, tacky material used in adhesives, sealants, and caulk products. The above two products are often referred to "isostatic" (crystallizable) PP (i-PP) and "static" (non-crystallizable) PP (a-PP), respectively.
(By Karian, Marcel Dekker, Handbook of Polypropylene and Polypropylene Composites, page 10)Hot Adhesives (14:52 pm 24.04.2011)
--A hot melt adhesive is defined as an adhesive applied from the melt and it gains strength upon solidification and crystallization. Hot melt adhesives are applied without solvents. The increase in solvent emission regulations has increased the demand for hot melt adhesives. Certain types of hot melt adhesives cure over time after application. However, with the general purpose hot melt adhesive, the material is applied as a thermoplastic melt and the resulting adhesive is also a thermoplastic. Attention has to be paid to the type of polimers forming the adhesive, since the resultant material has be low viscosity in the melt (for easy application) but must solidify into a cohesively strong material.
--Hot melt adhesives are divided into two classes; the first class depend upon formulation design. That is, the properties of hot melt come from the combination of components that give the desired balance of properties. This situation should now be familiar, as it was encountered for elastomer based as well as structural adhesives. In the second class of hot melt adhesives, adhesive performance is molecularly designed. That is, the hot melt performance does not come from formulation, but rather from the choice of monomers used to make the base polymer.
(Alphonsus V. Pocius, Adhesion and adhesives technology: an introduction, page 271)
Natural Adhesives (15:14 pm 24.04.2011)
This term is used to include vegetable and animal based adhesives and natural gums. These include organic materials such as casein, blood, albumin, hide, bone, fish, starch, resin, shellac, asphalt, chitosan, and inorganic adhesives like sodium silicate. Their use, except for the inorganic adhesives, is mostly limited to paper , paperboard, foil, and light wood. They are inexpensive, easy yo apply, and have a long shelf life. These adhesives develop tack quickly, but have low strength properties. Most are water soluble and use water as a solvent. They are supplied as liquids or dry powders to be mixed with water. Some are dispersions in organic solvents.
( Sina Ebnesajjad, Adhesives Technology Handbook, page 49)
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