Chemical composition elastic properties affected

Chemical Composition The chemical composition of the materials of construction may affect the safety of a packaging component. New materials may result in new substances being extracted into the dosage form or a change in the amount of known extractables. The chemical composition may also affect the compatibility, functional characteristics, or protective properties of packaging components by changing rheological or other physical properties (e.g., elasticity, resistance to solvents, or gas permeability). 

It is generally accepted that the structure and the chemical composition of polyester hard segments have influence on the rate of synthesis, molecular weight, crystallization rate, elastic recovery, as well as tensile and tear strength. The hard segments structure affects primarily mechanical and processing properties, while the structure of the soft segments influences physical and chemical properties. It is known that the poly(ether ester)s... 

Elasticity is exhibited by materials of varying chemical composition. The primary condition for a material to be elastic is that it should predominantly consist of long linear molecules, i.e. it should have a large number of recurring units linked together by strong chemical bonds, and these should he cross-linked. Elasticity is apparently independent of whether these units are identical throughout the whole chain or whether other monomers are present. Properties other than elasticity, however, such heat and fluid resistance, will be markedly affected by the structure and type of flie chemical units involved in the chain. 

Seidl created a model based on the state of the surface film (e.g. expanded or condensed), the equilibrium spreading pressure, and the area per film molecule to describe organic film formation from fatty acids, then applied it to rainwater and aerosol particles [245]. He concluded that, in most cases, only dilute films (with concentrations below that necessary to form a complete monolayer) would form on aerosols and raindrops, and such films would not affect their physical or chemical properties. However, dense films were predicted to form on aerosols in the western U.S., mainly attributable to biomass burning. Mazurek and coworkers developed a model to describe structural parameters (elastic properties, etc.) of fatty acid films on rainwater without requiring knowledge of the surfactant concentration or composition by using surface pressure-area and surface pressure-temperature isochors and the rain rate and drop diameter distribution [33]. This model can be used to identify the origin of specific compounds and an approximate chemical composition based on the force-area characteristics of collected rainwater films. 

Sealants are used to seal cracks and joints in window frames or between panels, to prevent rain, air and dust from passing through the joint and even to improve the thermal performance of a wall. Sealants are available in a non-cured, pourable or extrudable state for easy application. Upon curing, they are transformed into a solid elastomeric material. Sealants must be deformable, have good recovery properties and should have good overall elastic properties. They should be durable and should not be affected by the environment to which they wiU be subjected. The general composition of a sealant consists of a base polym and additives. Sealants can be classified based on their chemical conq)osition. Two of the most widely used groups in the construction industry, are siliccmes and polyurethanes (i). 

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