packer deswells if the solvent is not present anymore for example water in the case of water swellables also the swollen material loses mechanical properties therefore lowering the maximum differential pressure the swollen packer can withstand fig2 a and 2b show a conventional oil swellable material the graphs are of volume change and modulus ratio as a function of time for an oil swell material oil swellable elastomers swell by fluid absorption in the rubber matrix and as can be seen in fig2 b their modulus tends to decrease as they swell and this affects the amount of differential pressure the packer is able to sustain after setting embodiments of the subject disclosure relate to downhole swellable fixtures composed of a swellable matrix comprising a reactive filler which reinforces the swellable matrix after swelling or setting further embodiments of the subject disclosure relate to downhole swellable fixtures composed of a swellable matrix which remains swollen after the swelling fluid is removed for example water the swellable matrix disclosed in the subject disclosure may be used for sealing applications for example packers the material is initially a compliant material after the filler reacts for example the cement sets the material becomes a stiffer and swollen material with hydration increasing volume the base material of the seal is generally selected from any suitable material known in the industry for forming seals preferably the base material is a polymer more preferably the base material is an elastomer elastomers that are particularly useful in the present invention include nitrile rubber nbr hydrogenated nitrile rubber hnbr carboxylated nitrile rubber xnbr carboxylated hydrogenated nitrile rubber xhnbr silicone rubber ethylene propylene diene copolymer epdm fluoroelastomer fkm fepm and perfluoroelastomer ffkm and any mixture or blends of the above u201c elastomer u201d as used herein is.