in a polymer matrix the composition may contain carbon black attainment of sustained release of trifluralin that is applied to gaps in pavements can be improved by using a clay trifluralin polymer composite material it can be made by sorbing trifluralin into clay e g montmorillonite that is in colloidal form the colloidal state is essential for best performance in longevity and reduced trifluralin degradation compared with carbon black and other fillers presented in the prior art the sorption process can use trifluralin vapor that contacts and permeates into the tiny clay particles a fluidized bed process is especially convenient for loading the particles however molten or dissolved trifluralin also can be used for loading the loaded clay is incorporated into a polymer matrix that is preferably polypropylene or polyethylene or polyester e g pet the composite material can be applied to the gaps in the pavement directly or as part of a product that includes a sealant the weakest point of resistance to plant root intrusion frequently is the seal between lengths of pipe gaskets that join the pipes usually are made of elastomeric materials incorporation of trifluralin into gasket materials has been described by cataldo and coworkers in u s pat no 5 449 250 longevity and effectiveness in preventing root intrusion at the gasket is attained in this invention by using a clay trifluralin elastomer composite material it can be made by sorbing trifluralin into clay e g montmorillonite that is in colloidal form the colloidal state is essential for best performance in longevity and reduced trifluralin degradation compared with.