Polymer crystallinity and crystallization kinetics via benchtop 1H NMR relaxometry: Revisited method, data analysis, and experiments on common polymers

Abstract

Semi crystalline polymers play an enormously important role in materials science, engineering, and nature. Two thirds of all synthetic polymers have the ability to crystallize which allows for the extensive use of these materials in a variety of applications as molded parts, films, or fibers. Here, we present a study on the applicability of benchtop 1 H NMR relaxometry to obtain information on the bulk crystal linity and crystallization kinetics of the most relevant synthetic semi crystalline polymers. In the first part, we investigated the temperature dependent relaxation behavior and identified T ¼ T g þ 100 K as the minimum relative temperature difference with respect to T g for which the mobility contrast between crystalline and amorphous protons is sufficient for an unambiguous determination of polymer crystal linity. The obtained bulk crystallinities from 1 H NMR were compared to results from DSC and XRD, and all three methods showed relatively good agreement for all polymers. In the second part, we focused on the determination of the crystallization kinetics, i.e., monitoring of isothermal crystallization, which required a robust design of the pulse sequence, precise temperature calibration, and careful data analysis. We found the combination of a magic sandwich echo (MSE) with a short acquisition time followed by a Carr Purcell Meiboom Gill (CPMG) echo train with short pulse timings to be the most suitable for monitoring crystallization. This study demonstrates the application of benchtop 1 H NMR relaxometry to investigate the bulk crystallinity and crystallization kinetics of polymers, which can lead to its optimal use as an in situ technique in research, quality control, and processing labs.

Poly(propylene-co-1-pentene-co-1-heptene) terpolymers: Mechanical and rheological behavior

“…Thus, the total crystallinity has been obtained for these terpolymers following the procedure described before for poly(propylene-co-1-pentene) 33 and poly(propylene-co-1-heptene) 19 copolymers. Once the different amorphous halos at room temperature are determined, their subtraction from the actual profile at a specific content in comonomers allows estimating the degree of crystallinity 19,32,34 . The deconvolution into the distinct characteristic reflections permits estimation of the amount of each polymorph.…”

Polymer Crystallization Studied by Hyphenated Rheology Techniques: Rheo‐NMR, Rheo‐SAXS, and Rheo‐Microscopy

“…The flow and deformation behavior of polymer melts can be thoroughly studied using rheology, whereas low‐field NMR relaxometry (also called Time Domain (TD)‐NMR) is a powerful technique for the characterization of molecular dynamics in polymeric materials . To achieve a substantial insight into the interplay of these domains, especially under flow, these two methods were combined into a single set‐up (Figure a) .…”

“…Low‐field Rheo‐NMR can be used to study processes with changes in the molecular dynamics and macroscopic flow behavior such as the curing of resins, the cross‐linking of rubbers, or the crystallization of soft matter . Based on the changes in molecular dynamics, a compositional analysis of multiphase soft matter systems during start‐up and continued application of linear and nonlinear shear deformations can be obtained . Furthermore, the effect of flow on the molecular dynamics of, for example, polymeric materials can be investigated making it a valuable tool to confirm certain concepts of polymer physics.…”

“…For Rheo‐NMR, the changes in molecular dynamics and the buildup of crystallinity from an isotropic melt were monitored by 1 H NMR relaxometry using a combined MSE‐CPMG pulse sequence . The mass crystallinity X c ( t ) was converted into a volume fraction φ c ( t ) using the densities of a fully amorphous and a theoretically 100% crystalline sample…”

Desenvolvimento da sequência de pulso RK-ROSE e aplicações em RMN-DT para analise de componentes sólidos

“…Oztop comprova a dependência linear da cristalinidade com o segundo momento ( ). Diversos trabalhos [49][50][51][52][53][54][55][56] utilizam a RMN-DT para estudo físicoquímico da matéria, as análises em sólidos vem crescendo com o desenvolvimento de sequências de pulsos.…”