Laminates, controlled release polymers

Cellulose esters have been commercially important polymers for nearly a century, and have found a variety of applications, including solvent-borne coatings, separation, medical and controlled release applications as well as composites and laminates and plastics. 

The extremely active academical and industrial research focused on the use of biodegradable polymers for agricultural applications has induced the introduction of several products to the market. These products based on biodegradable materials are supposed to be applied as mulching films, green houses sheets, laminates, and containers in agricultural practices and for application such as soil structurization and controlled release of chemicals such as fertilizers and herbicides. 

Another method of pilocarpine release is the use of a thin laminate of hydrophile polymers inserted in the conjunctiva cul-de-sac. This pilocarpine Ocusert system releases pilocarpine at a constant pre-determined rate. The sustained-release system, providing such advantages as maximum duration of pressure control, less round-the-clock pressure variation, use of smaller drug concentrations with decrease of ocular and systemic side effects, also has some disadvantages one problem is the burst phenomenon, in which there is a large initial release of pilocarpine after insertion, resulting in severe miosis and ciliary body spasm. Up to the present several cases of loss of device and 8 -formation, comeal erosion, subconjunctival bleeding and displacement to the pupil have been reported. 

The second system was developed by the Hereon Division of Health Chem Corporation and consists of a laminated plastic chip. Figure 2. The chip is composed of a pheromone saturated polymer reservoir with a semi-permeable plastic membrane on either side. The pheromone is thus released by diffusion from the reservoir through the membrane. The rate is controlled by the membrane composition and thickness(2,). The two systems are applied in a polybutene sticker to facilitate adhesion to the plant surface. 

Coated and laminated textiles usually consist of a textile substrate, which will typically be a woven, knitted or nonwoven fabric, combined with a thin, flexible fdm composed of a natural or synthetic polymeric substance. A coated fabric is one in which the textile substrate has a polymer film applied directly to one or both surfaces as a viscous liquid in a solvent or water, the thickness of which is controlled by application via a blade or similar aperture. A transfer coated fabric is an intermediate product in which a thermoplastic film is first prepared on a release paper prior to thermally bonding to the textile substrate. A laminated fabric usually consists of one or more textile substrates that are combined with a pre-prepared polymer film or membrane by adhesives or heat and pressure (Hall, 2000). 

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