Polyolefin Resin Grade Verification via Attenuated Total Reflectance Spectroscopy
ATR-FTIR verifies polyolefin grades by measuring specific infrared absorbance ratios to quantify comonomer content, branching density, and copolymer structure.
Cryogenic Microtomy
Meaning
Precise preparation technique for polymers involves slicing thin sections of soft or elastomeric materials at temperatures below their glass transition point. Cryogenic microtomy provides the ultra-thin specimens necessary for transmission electron microscopy and infrared spectroscopy when ambient temperature cutting would smear the polymer structure. By hardening the sample with liquid nitrogen, the blade achieves clean cleavage through the rubbery phase of a toughened polypropylene.
This method prevents mechanical deformation.
Sample Preparation
Cooling the material below its brittle point ensures that the mechanical energy of the knife does not induce localized melting or flow. While standard microtomy works for rigid resins like polystyrene, cryogenic microtomy is required for any polymer with a glass transition temperature near or below room temperature. The technique relies on a precision-controlled chamber where both the glass or diamond knife and the specimen stay at a constant sub-zero temperature.
Defect Analysis
Evaluation of multi-layer films or co-extruded parts depends on the integrity of the interface layers captured by this process. If the temperature is too high during cutting, the layers may delaminate or compress, masking the true thickness or the presence of interfacial voids. A moulder uses these sections to verify the dispersion of flame retardants or the migration of additives that might cause surface blooming.
Material Integrity
Maintaining the specimen in a glassy state preserves the spatial arrangement of fillers and crystalline domains. This precision is necessary when measuring the aspect ratio of glass fibres or the size distribution of regrind particles within a virgin matrix.