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A variant of the metric perm is used in DIN Standard 53122, where permeance is also expressed in grams per square meter per day, but at a fixed, "standard" vapor-pressure difference of 17.918 mmHg. This unit is thus 17.918 times smaller than a metric perm, corresponding to about 0.084683 of a U.S. perm.
Materials have a moisture vapor transmission rate (MVTR) that is established by standard test methods. One common set of units is g/m 2 ·day or g/100in 2 ·day. Permeability can be reported in perms , a measure of the rate of transfer of water vapor through a material (1.0 US perm = 1.0 grain/square-foot·hour· inch of mercury ≈ 57 SI perm ...
Housewrap (or house wrap), also known by the genericized trademark homewrap (or home wrap), generally denotes a modern synthetic material used to protect buildings. Housewrap functions as a weather-resistant barrier , preventing rain or other forms of moisture from getting into the wall assembly while allowing water vapor to pass to the exterior.
Time-domain thermoreflectance is a method by which the thermal properties of a material can be measured, most importantly thermal conductivity. This method can be applied most notably to thin film materials, which have properties that vary greatly when compared to the same materials in bulk.
Polymers represent another large area in which thermal analysis finds strong applications. Thermoplastic polymers are commonly found in everyday packaging and household items, but for the analysis of the raw materials, effects of the many additive used (including stabilisers and colours) and fine-tuning of the moulding or extrusion processing used can be achieved by using differential scanning ...
Increased thermal vibrations produce thermal expansion characterized by the coefficient of thermal expansion (CTE) that is the gradient of the graph of dimensional change versus temperature. CTE depends upon thermal transitions such as the glass transition. CTE of the glassy state is low, while at the glass transition temperature (Tg) increased ...
In its simplest form, a small tabletop or lab size machine can be used to heat small cut sections of plastic sheet and stretch it over a mold using vacuum. This method is often used for sample and prototype parts. In complex and high-volume applications, very large production machines are utilized to heat and form the plastic sheet and trim the ...
The crystallinity of PVF ranges from 20 to 60%, depending on the polymerization method and thermal history of the polymer. It has been found that lower polymerization temperature leads to a decrease in head-to-head linkages and subsequently increase in melting point since the highly regular structures display higher crystallinity .