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Transparent Plastics

Data on transparent plastics is available within Granta’s PolymerUniverse data module (a subset of the MaterialUniverse data). It can be used with GRANTA MI or CES Polymer Selector  to support rational selection, implementation of enterprise-wide materials strategies, and positioning (technical and economic) for these important materials.

Why would you be interested?

If you design products and parts with transparent or clear plastics for:

• Functional reasons: combining transparency or optics with mechanical function

• Medical products - transparency is especially valued in medicine where the ability to make things visible to doctors, nurses, and patients is at a premium

• Aesthetic effect – think Apple’s classic ‘iMac G3’ design
  
  
• Glass substitution: where these plastics offer a lighter, tougher alternative to glass.

The problem

Transparency carries compromise and comes at a cost. CD jewel cases, well known for cracking easily, are made from crystal clear polystyrene (PS), which is cheap, but brittle. Clear plastics are usually more prone to 'environmental stress cracking' (ESC).  ESC is cracking due to the simultaneous effect of stress and a fluid.  Polycarbonate is optically clear, strong, and very tough – apparently ideal for riot shields, until rioters discovered that baking soda caused them to crack. Failure from ESC is often unexpected.

Compared to opaque plastics, transparent materials offer a more limited range of strength, stiffness, durability, electrical, and thermal properties.  To work around these limitations, material suppliers have developed a broad range of specialized clear plastics, each with advantages and disadvantages for specific design challenges. There are now many thousands of commercially available transparent grades belonging to over 40 polymer types.

This makes selection of the optimal clear material both more rewarding and more complicated.  How does a designer identify the most cost effective two or three clear plastics for their design exhaustively, reproducibly, auditably, and quickly? 

The Granta solution

This is where Granta helps - you can use our property data on transparent plastics along with the analysis tools of CES Polymer Selector or GRANTA MI to make better design and business decisions about these materials, and to do so in a reliable, repeatable, and auditable manner.

The data consists of around 120 transparent material records presenting comparable properties for thousands of commercially available transparent grades.  The table summarizes the categories and types of plastic. 

New in 2008 - materials in red have been revised or added to the database.

All standard PolymerUniverse attributes are available for every material:

• cost
  
  
• physical
  
  
• mechanical
  
  
• thermal
  
  
• electrical
  
  
• optical
  
  
• durability
  
  
• chemical 

Specific properties provided in the data module that are of particular relevance for transparent materials selection include:

• impact strength - toughness (23 and –30 C)
  
  
• biocompatibility (for medical or food contact applications)
  
  
• refractive index
  
  
• environmental stress crack index
  
  
• resistance to 190 different chemical environments