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Design
Considerations
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Design for assembly of plastic materials requires that special consideration be given to the strength requirements, operating environment, material properties, joint function, safety and regulatory requirements of the application to insure successful performance.
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Assembly performance is sensitive to polymer orientation, strain rate, application temperature, applied stress and chemical environment as well as the physical properties of the materials used. Each of these issues should be considered to optimize assembly performance.
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Plexiglas Acrylic Resins
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Property
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Units
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V052
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V825
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V826
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MI-7
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DR
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Tensile Strength (ASTM
D638)
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PSI
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10,200
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10,200
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10,200
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7,000
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5,000
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Tensile Elongation @
Break
(ASTM D790)
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%
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6
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6
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6
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35
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50
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Flexural
Modulus
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PSI
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450,000
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450,000
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450,000
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380,000
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270,000
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Poisson's
Ratio
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--
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0.34
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0.34
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0.34
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0.34
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0.34
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Vicat Softening Point
(ASTM D1525 90°F/hr,11.0 lb.)
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°F
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200
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220
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220
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191
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185
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Falling Dart Impact
Strength
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ft-lb
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1
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1
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1
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7
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10
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Plexiglas V-Series acrylic resins are high modulus, high
tensile strength polymers with maximum heat resistance and
dimensional stability. Plexiglas MI-7 and DR impact modified
acrylic resins provide 7-10 times the impact strength of
Plexiglas V-Series resins and have a higher elongation to
failure for increased tolerance to assembly induced
strain.
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Properly designed ribs can increase load
carrying capacity, permit a decrease in wall thickness and
increase part stiffness. Excessive rib thickness may result
in sink or part warpage.
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Generous radii should be designed into
all corners and edges to avoid sharp changes in geometry
which develop stress concentration areas prone to
failure.
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Thermal expansion rates of dissimilar
materials must be considered to avoid the development of
high stresses during temperature changes.
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