PA has higher impact strength in the wet state, but poor impact strength in dry and low temperature, and insufficient toughness in the cold season, can be modified by blending it with low modulus polymers or impact modifiers However, general polymers are not compatible with PA, so simple physical blending, because rubber particles are too large to effectively disperse impact energy and have little effect, good compatibility is the key to improving the performance of PA blends, through The third component is added to act as a coupling agent or a compatibilizer to increase the compatibility between the PA (parent resin) and the added polymer (disperse phase). The most commonly used are block and graft copolymers, which have been used in the past. The polymer (also called the second component) is a low modulus rubber, such as ethylene propylene rubber and nitrile rubber, and the influencing factors are (1): (1) the size and dispersion state of the rubber particles; (2) the interface bonding between the matrix resin and the dispersed phase State; (3) Interfacial energy; (4) Shear modulus and glass transition temperature of rubber. The size of the rubber particles should be greater than the thickness of the cracks, so that the rubber particles are not covered by the growing cracks, and the interfacial adhesion force should be large enough to ensure effective transfer of stress and passivation of crack propagation. In addition, the average distance between particles should be small enough to terminate the crack.
According to reports in the literature, the earliest typical compatibilizer used for PA toughening was 1974 MAH-g-PP (maleic anhydride grafted polypropylene) or MAA-S (acrylic-styrene copolymer) as PA66/PP. Or PA66/PS copolymer compatibilizer, and later launched MAH-g-EPDM, MAH-g-LDPE, MAH-g-PP, oxidized PE, MAH/S block copolymer, MAH-g-SEBS , S/AN/MAH copolymers and the like as a PA toughening compatibilizer. There are many manufacturers in the world for toughening and modifying industrial production, and they are constantly introducing new varieties and improving product performance. Du Pont, Allied, Dexter, Bayer AG, Exxon, Wilson-Fiberfil, EMS-Chem, GE, Mitsubishi Chemical, Atochem , Rhone Poulenc, LNP, BASF, Wellman and other companies have products listed, some are PA resin plants, and there are professional compounding plants. The toughened modified PAs Du Pont has introduced successively are: Bexloy C (amorphous PA/elastomer), ETP (PA/NBR), Minlon (PA/mineral filler, modifier), Selar (PA/PO, Modifiers), Zytel ST (PA66/elastomer, glass fiber), Zytel ST-350 (PA12/elastomer), Zytel ST 801 (PA/elastomer), Zytel 300,400 (PA66/impact modifier )Wait. Among them, Du Pont's Zytel ST 801 is a world-renowned toughening-modified PA66 grade. Its standard PA66 grade Zytel 101L has a Charpy impact strength of 5 kJ/m2 and 15 kJ/m2 in the wet state and 50% RH. The Zytel ST 801 is 90kJ/m2 and 115kJ/m2, respectively, and the increase in the range is quite impressive, making the PA66's application range greatly expanded.