Modification of a Fischer-Tropsch Wax by Grafting with Maleic Anhydride I. Nova ´k, 1 I. Krupa, 1 A. S. Luyt 2 1 Polymer Institute, Slovak Academy of Science, 842 36 Bratislava, Slovakia 2 Department of Chemistry, University of the Free State (Qwa-Qwa Campus), Private Bag X13, Phuthaditjhaba, 9866, South Africa Received 12 August 2003; accepted 29 January 2004 DOI 10.1002/app.20513 Published online in Wiley InterScience (www.interscience.wiley.com). ABSTRACT: The polarity of a hard Fischer-Tropsch par- affin wax was improved through grafting of maleic anhy- dride (MA) initiated by dibenzoyl peroxide (DBP), which is reflected by a significant increase in the polar component of the surface free energy. MA and DBP concentrations of 3 wt % each are sufficient for significant modification of the po- larity of the wax. FTIR spectra confirm the presence of anhydride groups on the wax chains, while gel permeation chromatograms show the development of a low molecular weight peak, which may be indicative of wax degradation. The grafting of wax by MA decreases the specific enthalpy of melting, as determined through differential scanning cal- orimetry. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 662– 668, 2004 Key words: Fischer–Tropsch wax; grafting; maleic anhy- dride; polarity; differential scanning calorimetry (DSC); FT- IR; functionalization of polymers INTRODUCTION Paraffin waxes (Fischer-Tropsch synthesis) are ali- phatic hydrocarbons consisting of straight or branched carbon chains. They are white, translucent, tasteless, and odorless solids consisting of a mixture of solid hydrocarbons of high molecular weight. Com- mon properties are water repellency, smooth texture, low toxicity, and freedom from objectionable odor and color. They are combustible and have good dielectric properties. They are used for preparation of candles, paper coating, protective sealant for food products and beverages, glass-cleaning preparation, hot-melt carpet backing, biodegradable mulch, lubricants, stop- pers for acid bottles, electrical insulation, and others. 1 Waxes and polymers, particularly polyolefines as low-energy substances, have low surface free energy values. 2 The introduction of specific polar groups onto polymer chains through chemical modification leads to the improvement of physical interactions such as hydrogen bonds, van der Waals forces or dipolar in- teractions. 3 This is reflected in higher values of surface energy, as well as in mechanical work of adhesion to more polar substrates. The untreated paraffins and polyolefins possess poorer wetability, because of their low polarity and low adhesives properties, 4 than the more polar sub- strates, which restricts its use in several technologi- cally important fields. These drawbacks can be over- come by graft polymerization of polyolefins 5 or by adding more polar low or high molecular weight ad- ditives to the polymer melt. 6,7 In fact, a small percent- age of functionality can dramatically increase the sur- face energy and the adhesive properties of polyolefins. Grafting of polyolefins by monomers containing polar functional groups is a highly efficient means of in- creasing the surface free energy, as well as of regulat- ing their adhesive interaction with different solid sur- faces, including metals. 8,9 Grafting has advantages over other methods of modification of polymers, among others the controlled introduction of grafted chains without changing the bulk properties. In the case of polyolefins, it is usually induced by a free radical initiator, but ionically initiated processes have also been used. 10 –13 Nonradiation induced chemical modifications of polyolefins have been even more diverse. They in- clude oxidation, reduction, substitution, elimination, cyclization, and addition reactions. 14 –17 The free rad- ical polymerization using organic peroxides such as benzoyl peroxide is the most widely used method for the synthesis of grafted polymers, because the process is relatively simple. The synthesis of polyolefin graft copolymers by reactive extrusion is a similar method for enhancement of its wetability and adhesive prop- erties. 18,19 For grafting of polyolefins, i.e., polyethylene, graft- ing and crosslinking in the melt are very important and are characterized by the formation of gels or Correspondence to: A. S. Luyt (luytas@qwa.uovs.ac.za). Journal of Applied Polymer Science, Vol. 93, 662– 668 (2004) © 2004 Wiley Periodicals, Inc.