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Sizing and fit for pressure garments 341

13.4 Materials for pressure garments

Pressure garments usually have direct contact and tightly cling to human skin, con-
forming to the structure of the human body and its dynamic changes. Therefore the
elasticity of the material plays a crucial role. Pressure garments also rely mainly
on elastic materials, followed by structural design (Liu, 2009). Material properties
and garment structure (construction) are the two factors that contribute to or impede
the comfort. Therefore, it is necessary to consider the physical properties of materials
and the dynamic characteristics of the human body under the condition of health and
safety. Generally speaking, the material elasticity of pressure garments will satisfy the
dynamic changes of the human body in the covered area.
To investigate the relations existing in the system “body-garment” between the
pressure created under the compression garment on one side and the material strain
on the other side, the physical model of a cylinder is used. Textile material is consid-
ered as a tight-fitted shell covering the body parts. The theoretical pressure P on a
cylinder with a radius of curvature r is calculated by the Laplace law (ASTM
D2594-04, 2016; Sloan, 1963)

P ¼ σ=r (13.1)
where σ is the stress of textile material.
The human body has a much more complicated shape than the cylinder, and is
described in terms of girth, arc, and linear measurements. Besides, the deformable
body should be considered after comparison of the surface curvature before and after
donning the garment. Thus, for precise calculation of pressure, it is necessary to take
into account the deformation of the horizontal sections due to compression of soft tis-
sues in different areas of the body.
So the ability of textile materials to push the human body directly depends on its
stress under elongation. Knitted materials have a certain elasticity, with excellent flex-
ibility due to the interlaced structure. In general, the materials are defined as follows: as
stretch materials with elongation more than 15%; as rigid materials with elonga-
tion smaller than 15%; as power stretch materials with elongation more than 30%.
The materials having 15%–30% elongation are called comfort stretch materials (Fan
and Hunter, 2009). Close-fitting garments made of such materials will have minimum
resistance to body movements. However, the research on the relationship between struc-
tural characteristics of high-stretch knitted materials and garment pressure is limited
(Sang and Park, 2013). The high-stretch materials are often used for compression gar-
ments because the compression garment must fit extremely closely (tightly to body) to
apply pressure to the skin (Lee et al., 2017). The pressure level (value) of a high-stretch
knitted material depends on the knit structure, yarn composition, and knitting types.
The materials for pressure garments are generally made of synthetic fibers. The
garments in daily-wear styles are generally made as a single layer. For production
of some sports protective garments, double or multiple layers are used. Typical fiber
compositions are complex and contain, for examples: