Microencapsulation of phosphate: application to flame retarded coated cotton Stephane Giraud a , Serge Bourbigot a, *, Maryline Rochery a , Isabelle Vroman a , Lan Tighzert b , Rene Delobel c a Laboratoire de Ge ´nie et Mate ´riaux Textiles (GEMTEX), UPRES EA2161, Ecole Nationale Supe ´rieure des Arts et Industries Textiles (ENSAIT), 9 rue de l’Ermitage, BP 30329, 59056 Roubaix cedex 01, France b Laboratoire de Chimie Macromole ´culaire (LCM), UPRESA-CNRS 8009, Universite ´ des Sciences et Technologies de Lille (USTL)—Ba ˆt. C6, 59655 Villeneuve d’Ascq cedex, France c Centre de Recherche et d’E ´ tude sur les Proce ´de ´s d’Ignifugation des Mate ´riaux (CREPIM), Parc de la Porte Nord—Rue Christophe Colomb, 62700 Bruay La Buissie `re, France Received 19 October 2001; received in revised form 18 January 2002; accepted 3 February 2002 Abstract Polyurethane-phosphatescombinationisknowntoformaflameretardant(FR)intumescentsystem.Theintumescentformulation could not be permanent because of the water solubility of the phosphate. This problem could be solved by the technique of microencapsulation. Di-ammonium hydrogen phosphate (DAHP) was microencapsulated with a polyurethane (PU) shell. Polyurethane for textile coating was loaded with neat or microencapsulated DAHP. We studied the thermal degradation behaviour ofDAHPmicrocapsules,PUloadedformulationsandcottoncoatedbythesePUformulations.Improvementofthethermalstability for PU textile coating was observed with neat and microencapsulated DAHP. The flame retarding behaviour of these coated cotton fabrics was also valued with the cone calorimeter. This new concept of phosphate encapsulated by PU shell showed a significant FR effect. # 2002 Elsevier Science Ltd. All rights reserved. Keywords: Polyurethane; Microencapsulation; Phosphate; Intumescence; Thermal degradation; Textile; Coating; Cotton 1. Introduction Textile coating with polyurethane (PU) resins provides to fabric properties such as abrasion resistance, water repellent,leatheraspectetc.Thistypeofcoatingoncotton or cotton-polyester blended fabrics is used in many fields such as transportation industry (e.g. car seats), garments (e.g. waterproof breathable jackets), furniture (e.g. arti- ficial leather), but these PU coatings have a bad flame retardancy. The addition of a flame retardant in PU coating is necessary to improve the fire behaviour of materials. According to several reports [1–4], ammonium phos- phates are efficient to develop with PU a flame retardant (FR) intumescent system. Intumescent formulations with ammoniumphosphatesareunfortunatelynotpermanent. Indeed, ammonium phosphates are water-soluble and they have a poor compatibility with the polymer. Thus problems of migration and solubility may occur. The microencapsulation of ammonium phosphates could avoid these problems. Microencapsulation is a process of enveloping microscopic amounts of matter in a thin film of polymer, which forms a solid wall [5]. This core/ shell structure allows isolation of the encapsulated sub- stance from the surroundings and thus protects it from any degrading factors such as water. The encapsulated substance can be liberated by fusion or dissolution of the impermeable shell or by diffusion across a porous shell [6,7]. It is of interest to study microencapsulation with a polyurethane shell for two main reasons. First, we can expect that microcapsules with PU shell will be compa- tible with the final PU coating on textiles and also with other polymeric matrices. Second, combination of the encapsulated ammonium phosphates and the PU shell could be itself an efficient FR intumescent formulation, 0141-3910/02/$ - see front matter # 2002 Elsevier Science Ltd. All rights reserved. PII: S0141-3910(02)00063-0 Polymer Degradation and Stability 77 (2002) 285–297 www.elsevier.com/locate/polydegstab * Corresponding author. Tel.: +33-3-20-25-89-84; fax: +33-3-20- 27-25-97. E-mail address: serge.bourbigot@ensait.fr (S. Bourbigot).