Polymers and composites by X-ray diffraction analysis determines the degree of crystallinity for semi-crystalline, amorphous polymeric and composite materials
Performing X-Ray Diffraction (XRD) analysis on samples of polymers or composites provides important solid-state structural information such as the degree of crystallinity.
Polymers come in many forms, including highly crystalline, semi-crystalline, microcrystalline or amorphous, and it is possible that in a single polymer sample, all three may be observed. The presence and relative quantity of these forms depend on how the polymer was formulated and processed and this in turn is known to affect mechanical properties such as compression, tensile strength, buckling, and creep. Consequently the degree of crystallinity is an important property to accurately determine.
Our polymer scientists use X-ray diffraction analysis (XRD) to study solid-state structural properties such as the degree of crystallinity for semi-crystalline, amorphous polymeric and composite materials which can be inferred from the XRD pattern appearance.
XRD analysis can assist in assessment and quantification of the crystalline phases (polymorphism), polytypes and all types of solid state molecular arrangements. If the polymer is crystalline, then the XRD diffraction pattern is a result of a crystal structure (as related by Bragg’s law); the pattern can be indexed and represented by a stick pattern of positions and intensities. We use this to aid the identification of semi-crystalline polymers in a polymers sample using the position and relative intensities of the X ray fingerprint of the crystalline phases of polymer. Where the sample consists of two materials our experts use XRD data to distinguish between block copolymers, alternating or randomly mixed copolymers.
Polymers can be processed into fibres and films and they can be molded and extruded. Each of these processes can orient the molecules and diffraction can be used to measure the orientation – in both crystalline and non-crystalline materials. Our experts use XRD patterns as the primary tool for the determination of crystalline orientation through the Hermans orientation function.
For amorphous materials, we utilise pair distribution function analysis to provide insights into the crystalline coherence length and nearest atom bonding. Low angle or small angle scattering can be used to determine the size and shapes of polymer domains within a specimen.
Our composites experts utilise X-ray studies to assess the structure of amorphous-crystalline composite materials which can help to determine the thermal stability limits of the composite structures and the temperature dependences of the parameters of crystalline and amorphous composite components.
Our experts - who have many years of experience of working in the polymer and polymer application industries - can extract an enormous amount of information from diffraction patterns of polymers. The insight we deliver from X-ray diffraction studies can be enhanced by our wider polymer analysis capabilities which include thermal techniques such as DSC and DMA techniques or chemical analysis methods such as High temperature-Gel Permeation Chromatography (HT-GPC) or FTIR spectroscopy. Using a strategic combination of analytical testing approaches we can support your decision-making process regarding polymer or product development, process development or to facilitate resolution of contamination or product failure issues.
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