Page 71 - Engineering Plastics Handbook

Properties 45

flows and temperatures for materials’ thermal transitions including T ,
g
crystallization phase changes, melting, product stability, oxidative stabil-
ity, cure, and cure kinetics [3].
Thermogravimetric analysis (TGA) measures changes in materials’
weight over a temperature and time range, to determine composition and
heat stability [3].
Engineering thermoplastics possess better dynamic mechanical prop-
erties than other thermoplastics. They have current or potential applica-
tions for gears, valves, rotating blades, biomechanicals such as prosthetics
and orthopedic implants, springs, pumps, thin film membranes, trans-
mission components, and small-amplitude vibration step-loading appli-
cations [3].
ASTM D4065-01 (ISO 6721-1), “Standard Practice for Determining and
Reporting Dynamic Mechanical Properties of Plastics,” (Adoptions: DOD
Adopted, Building Codes Adopted) describes tests for torsional, flexible,
compressive, or tensile dynamic properties. It includes laboratory proce-
dures for determining the dynamic mechanical properties of plastics sub-
jected to different oscillatory deformations on dynamic thermomechanical
analyzers (TMAs) or dynamic mechanical analyzers. The methods are
used for viscoelastic plastics with an elastic modulus from 0.5 MPa to 100
7
GPa (73 psi to 1.45 × 10 psi). Data are used for determining viscoelastic
properties such as elastic modulus and loss modulus as a function of tem-
perature, frequency, or time; and transition temperatures. Five free-
vibration, resonant or nonresonant forced-vibration test methods in ASTM
D4065-01 (ISO 6721-1), “Standard Practice for Determining and Reporting
Dynamic Mechanical Properties of Plastics,” are (1) torsional pendulum,
(2) torsional braid analyzer, (3) dynamic mechanical analyzer, (4) vis-
coelastometer, and (5) mechanical spectrometer. The torsional pendulum
data are used to calculate oscillating strain, usually of a rectangular cross
section. The ratio of loss modulus to the storage modulus tan δ is meas-
ured in compression, tension, flexure, and shear. The torsional braid ana-
lyzer test method uses a resin-coated glass fiber braid to determine
oscillating strain, with the elastic component and damping component. The
dynamic mechanical analyzer, viscoelastometer, and mechanical spec-
trometer test methods use a rectangular or circular specimen to determine
the oscillating strain, elastic component, and damping component.
ASTM D4092-01 (ISO 6721) is entitled “Standard Terminology for
Dynamic Mechanical Measurements on Plastics,” DoD Adopted. It con-
tains descriptions of the technical terms for dynamic mechanical prop-
erty measurements on plastics including solids, melts, and solutions. It
is also relatable to ISO 472 ‘Definitions’ and certain items in ISO 6721-
01, “Plastics—Determination of Dynamic Mechanical Properties, Part
1, General Principles.” Other ASTM/ISO standard test methods for
dynamic mechanical analyses are