Measurement of Flaws

It is clear that macroscopic and microscopic flaws affect the properties of PTFE parts. It is important to characterize their impact quantitatively. These flaws can be directly measured by a number of techniques. The measurement methods are complex and not suitable for routine quality control. Macroscopic flaws are frequently detectable visually or by a simple magnifying glass. Internal defects can be detected by x-ray techniques such as radiography. ASTM E94 can be applied as a guideline in establishing procedures. 

Molding Technique Advantages Disadvantages Typical Process Shear Rate (sec ) 

Injection Molding The most precise control of shape and dimensions, highly automatic process, fast cycle time the widest choice of materials. High capital cost is only good for large numbers of parts large mold pressures (140 MPa). 1,000-10,000 

Transfer Molding Good for encapsulating metal parts and electronic circuits. Some scrap with every part and each charge is loaded by hand. 1-100 

Blow Molding Can make hollow parts (such as bottles) stretching action improves mechanical properties, fast cycle requires low labor. No direct control over wall thickness cannot mold small details with high precision requires a polymer with high melt strength. - 

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