Preparation of a Compatibilizer

Compatibilizer preparations are needed for use with a polypropylene and NBR/ HNBR blend, the components of which are grossly incompatible [7]. This could be a one-step process if one starts with commercially available maleic anhydride (MA) modified polypropylene and amine-terminated nitrile rubber. Then one can melt mix the above fimctionalized polymers in a batch or a continuous mixer and prepare the compatibilizer, as shown in step 2 below. One can also modify the polypropylene as described below in step 1, and use it to prepare the compatibilizer. 

Polypropylene is melt mixed with an organic peroxide and maleic anhydride using a Brabender, Banbtuy, or twin-screw mixer to graft anhydride ftmctionality on the polymer. The components could be blended together and fed to either a batch mixer or continuous mixer or the polymer is melted first and then the maleic anhydride and peroxide are added in that order. The unreacted maleic anhydride is removed before use. 

Maleic anhydride modified polypropylene is then melt-mixed with secondary amine-terminated nitrile rubber (NHR-NBR, known as ATBN) to form a graft copolymer containing nitrile rubber (NBR) segments and polypropylene (PP) segments. 

The PP segment of this compatibilizer will be compatible with PP or any other polymer that is compatible with polypropylene and the NBR segment will be 

The compatibilizer can be prepared first and melt blended with the polymer blend or it can be produced in situ during melt mixing of the blend. The compatibilizer composition will depend upon the polymer pair that is being compatibilized. 

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To toughen PA, 2-5 wt% of either PO, elastomer, ionomer, acidified or epoxidized copolymer may be added. PA/PO blends of type (2) were developed to improve dimensional stability and to reduce water absorbency of PA. Alloying PA with PO reduces the rate of water migration to and from the blend, but not the inherent water absorption of PA [Utracki and Sammut, 1991, 1992]. The alloying is either a two- or three-step reactive process (1°) acidification of PO, (2°) preparation of a compatibilizer, and (3°) compounding PP, PA, and the compatibilizer. Usually, the reactive blending is carried out in a twin screw extruder [Nishio et al., 1990 Hu and Cartier, 1998], Since it may cause reduction of the blend crystallinity (thus performance), the extend must be optimized. The rigid PA/PP blends usually comprise PA PP =... 

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