Barrier and mechanical properties of pulp fiber/polymer laminates and blends

Paperboard laminates coated with two grades of poly(epsilon-caprolactone) ( PCL), poly(hydroxy butyrate-co-valerate) (PHBV) or a liquid crystalline cop olyester (LCP) were prepared by compression molding, and the influence of t he processing conditions and polymer content of the laminate on the laminat e properties was studied. Ligno-cellulose fiber/polymer blends were prepare d from wet pulps and PCL and PHBV. The morphology, water vapor transmission rates, creasability, curl and twist and mechanical properties of the lamin ates and blends were studied. LCP and slowly cooled high molar mass PCL lam inated paperboards showed the best creasing properties and the paperboards that were penetrated by the polymer showed the smallest degree of curl and twist. Extensive penetration occurred during compression molding of the pap erboard with the low molar mass PCL at all temperatures and with PHBV and L CP at the higher molding temperatures. The water vapor transmission rates r anged from 1 to 300 times that of polyethylene depending on the polymer use d and on the thermal history. In the case of blends, competitive properties were obtained only in those with a high polymer content. The laminate stif fness decreased and the strength increased in two polymer concentration reg ions, at similar to 20 wt% due to fiber-fiber separation and at similar to 60 wt% due to phase inversion.