Modification of Nylon 6 , 6 1

Nylon 6, 6 is regarded as tough and ductile materials since it exhibit high tensile elongation to break and high drop weight impact strengths. However, under conditions of stress concentration such as in the presence of sharp notches or cracks, polyamides exhibit brittle failure. This property, evaluated as notched Izod or Charpy impact tests, indicates that unmodified polyamides exhibit relatively low energies for crack propagation. Crystalline thermoplastic polymeric materials such as low carbon monomer nylons are very sensitive to craze and crack propagation and so their toughness and impact resistance properties are relatively low. Nylon 6 and 6,6 are relatively low cost engineering thermoplastics that have been found so many applications including automotive industry. However, relatively low impact and bending resistance of these materials especially at low temperatures and high deformation rates, restrict applications of these materials. Rubber toughening can be considered as an economical and effective method to toughen and extend applications of nylon without any important increase in its price or decrease in its engineering properties. Many rubbers such as EPR, EPDM (ethylene propylenediene monomers), NR (nitrile rubber), SBR (styrene-butadiene rubber), and SEBS (styrene ethylenebutadiene-styrene tri-block copolymer) have been successfully used in toughening of thermoplastic materials. However, most rubbers are not compatible with nylon and cannot be finely dispersed in it. To overcome this deficiency, polyamides have been blended with several types of impact modifiers that are typically elastomeric or low modulus type olefinic polymers. However, the inherent immiscibility of polyamides with other polymers such as olefinic rubbers necessitated the development of proper compatibilization techniques to reduce the interfacial tension and improve the dispersability of the rubber for effective impact modification. This development in the area of nylon 6, 6/EPDM blend may give the more advantageous characteristics of the presently available nylon and may compensate the deficiencies of the same.