# Time Domain NMR in Polymer Science: From the Laboratory to the Industry
## 3 Applications
### Industrial Applications
Similar behavior can be observed after exposure to solvents, due to increased mobility of chains, but in the longer time the morphological changes are less strong than the reorganization attained with temperature. The impact of PE grade was also taken into consideration, showing almost no composition change for LLDPE and HDPE and instead wider thermal evolution for LDPE (Figure 18c), because of its lower melting temperature, lower crystallinity, and tertiary carbons easily subjected to attack by free-radicals [107]. Exposure of rubbers to solvents was also explored, since many rubbery materials have applications at direct contact with liquids, for example as sealing components. Commercial natural rubber (NR) susceptibility to biodiesel was investigated, exposing commercial carbon black (CB)-filled NR to  
Figure 18: Effect of aging processes onto NMR parameters. (**a**) Increase of crosslinking density, determined with MQ, with time of NBR rubbers exposed to air, base oil and full oil (Reprinted with permission from reference [103]. Copyright 2018 Elsevier). (**b**) Variation of the proton effective relaxation times with depth for a non-stabilized PA12 at increasing thermal-aging time (Reprinted with permission from reference [106]. Copyright 2016 Elsevier). (**c**) Temperature-induced morphology changes, quantified with the proton effective relaxation time, for different PE grades (Reprinted with permission from reference [107]. Copyright 2018 Wiley-VCH). a different mixture of diesel/biodiesel. CPMG measurements were recorded before and after 30 and 90 days of exposure, showing three components that steadily increase with the addition of solvent and time. To separate the effect of swelling from the actual biodiesel addition effect, MQ measurements were conducted, indicating a systematic lower DQ intensity, at same exposure times, for samples immersed in mixtures containing biodiesel, and a concurrent increase in the fraction of defects, indicating degradation of the network. A complete breakdown is reached after 90 days of sole biodiesel, where no DQ intensity is detected. MSE-FID analysis was able to detect the presence of a rigid phase in the liquid mixtures containing biodiesel after sample removal, as evidenced by the increasing signals with an immersion time of Figure 19, indicating chains with highly hindered mobility, which are attributed to CB exudation, leading to impairment of mechanical properties [108]. Even the effect of processing methodology on network structure has been analyzed. The blending method, in solution or mechanical in a two-roll mill, for NR/SBR blends with different composition has an impact on \(\mathrm{D_{res}}\) difference between the experimental values and the theoretical ones, based on a mixture law. Mechanical blending gives the highest differences, meaning lower efficacy, giving rise to stronger phase separation that leads to preferential migration of curatives in the NR phase, while solution blending enhances the interface between the phases [109]. Even materials subjected to mechanical deformations can be distinguished from pristine samples. Fluorosilicone O-rings underwent accelerated aging under compression to elucidate if they had taken a compression set. A modified version of DQ NMR sequence was employed, with an evolution period of fixed time t\({}_{1}\) to dephase completely zero and double quantum coherences and applying a \(\pi\)-pulse in alternate scans during this period to filter out longitudinal magnetization. A dipolar decay rate is then recorded, showing increased rates after compression sets respect to pristine samples, indicating a compression-induced order. However, the technique is not sensitive enough to discriminate between compression sets of different magnitude, because decay rates for compressed samples are quite similar [110]. However, differentiation capabilities between samples with subtle differences are attainable with other measurements, implementing statistical protocols.