Product testing dimensional stability

The moisture content of a plastic affects such conditions as electrical insulation resistance, dielectric losses, mechanical properties, dimensions, and appearances. The effect on the properties due to moisture content depends largely on the type of exposure (by immersion in water or by exposure to high humidity), the shape of the product, and the inherent behavior properties of the plastic material. The ultimate proof for tolerance of moisture in a product has to be a product test under extreme conditions of usage in which critical dimensions and needed properties are verified. Plastics with very low water-moisture absorption rates tend to have better dimensional stability. 

They have prepared some compressed wood samples which show, in addition to increased density and surface hardness, a lower moisture regain than untreated wood up to 80% relative humidity. Using materials such as these, they have experimented with the manufacture of parquet flooring, a rather severe test of dimensional stability. A variety of other finished products have been prepared, some on pilot plant scale. However, it is not known to what extent they have appeared as products in the open market. Their technology is available through licensure. 

In order to select materials that will maintain acceptable mechanical characteristics and dimensional stability one must be aware of both the normal and extreme thermal operating environments to which a product will be subjected. TS plastics have specific thermal conditions when compared to TPs that have various factors to consider which influence the product s performance and processing capabilities. TPs properties and processes are influenced by their thermal characteristics such as melt temperature (Tm), glass-transition temperature (Tg), dimensional stability, thermal conductivity, specific heat, thermal diffusivity, heat capacity, coefficient of thermal expansion, and decomposition (Td) Table 1.2 also provides some of these data on different plastics. There is a maximum temperature or, to be more precise, a maximum time-to-temperature relationship for all materials preceding loss of performance or decomposition. Data presented for different plastics in Figure 1.5 show 50% retention of mechanical and physical properties obtainable at room temperature, with plastics exposure and testing at elevated temperatures. 

Another effort is being made to examine the recycle of wood fiber-PS composites into the same material and testing the resultant product under extreme conditions (e.g., exposure to boiling water, at room temperature, 105°C and -20 C). The composite material was reground to a number 20 mesh size and remolded three times in the experiment. Compared with the original extruded composite, the mechanical properties and dimensional stabilities of the recycled material did not change significantly even after exposure under extreme conditions. Detailed data on the study are contained in Maldas and Kokta [ 1990]. 

There is an almost unlimited number of ways to characterize spunbonded fabrics. Many tests in use were originally developed for the characterization of textiles and paper products. When taken together, properties such as tensile, tear, and burst strength toughness elongation to break basis weight thickness air porosity dimensional stability and resistance to heat and chemicals are often... 

Primary container-closure system-related data will need to cover storage, transportation, and use. The choice of materials of construction, their description, and the ability of the container-closure system to protect from moisture and/or light will need to be considered. The compatibility of the container-closure and its contents will need to consider sorption, leaching, and safety. The performance of the container-closure system will also need to be considered in terms of dose delivery from any associated device that is to be supplied as part of the product. Container-closure components will require adequate specifications covering description, identification, critical dimensional tolerances, and test methodology (including pharma-copeial and noncompendial methods). More data are likely to be required for liquid or semi-liquid products than for solid dosage forms. In the latter, product stability data and container-closure system specifications may suffice. 

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