Page 217 - Biomedical Engineering and Design Handbook Volume 2, Applications

196 MEDICAL DEVICE DESIGN

TABLE 7.3 Properties of Polyvinyl Chloride
Polyvinyl Chloride
Density 1380 kg/m 3
Young’s modulus (E) 2900–3300 MPa
Tensile strength (σ ) 50–80 MPa
t
Elongation at break 20–40%
Notch test 2–5 kJ/m 2
Glass temperature 87°C
Melting point 80°C
Vicat B * 85°C
Heat transfer coefficient (λ) 0.16 W/(m · K)
Effective heat of combustion 17.95 MJ/kg
–5
Linear expansion coefficient (α) 8 10 /K
Specific heat (c) 0.9 kJ/(kg · K)
Water absorption (ASTM) 0.04–0.4
Price 0.5–1.25 €/kg
* Deformation temperature at 10 kN needle load.
Source: Wikipedia (http://en.wikipedia.org/wiki/Polycarbonate).

packaging application for blow-molded bottles, blisters, and thermoform trays. PVC is tough and
clear and has excellent barrier properties as well as high impact resistance (Table 7.3).
Polystyrene (PS). Polystyrene (PS) is one of the most versatile, easily fabricated, and cost-
effective plastic used in the packaging industry. It can be molded, extruded, and foamed. It is prob-
ably best known for its use as cushioning materials for electronic products. There are two types of
polystyrene available for packaging applications: general purpose and high impact (HIPS). It is the
high-impact type that is used for medical device packaging applications. High-impact polystyrene
contains a small amount of rubberlike polybutadiene blended in to overcome the brittleness of the
general-purpose material. This makes the HIPS tougher but less clear, usually translucent or opaque.
The material may be acceptable for applications where visibility of the device is not required. The
advantages of the material are its cost, heat resistance, and ease of formability (Table 7.4). However, it
may be susceptible to impact damage during shipping and handling. Another styrene-based material is

TABLE 7.4 Properties of Polystyrene
Polystyrene
Density 1050 kg/m 3
Density of EPS 25–200 kg/m 3
Specific gravity 1.05
Electrical conductivity (s) 10 –16 S/m
Thermal conductivity (k) 0.08 W/(m · K)
Young’s modulus (E) 3000–3600 MPa
Tensile strength (s ) 46–60 MPa
t
Elongation at break 3–4%
Notch test 2–5 kJ/m 2
Glass temperature 95°C
Melting point 240°C
Vicat B 90°C
2
Heat transfer coefficient (Q) 0.17 W/(m K)
–5
Linear expansion coefficient (a) 8 10 /K
Specific heat (c) 1.3 kJ/(kg · K)
Water absorption (ASTM) 0.03–0.1
Decomposition X years, still decaying
Source: Wikipedia (http://en.wikipedia.org/wiki/Polystrene).