Comparison of thermal techniques for glass transition assignment. II. Commercial polymers

Ferrillo, R. G.; Achorn, Peter J.

doi:10.1002/(sici)1097-4628(19970404)64:1<191::aid-app17>3.0.co;2-7

Cited by 29 publications

(20 citation statements)

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“…Achorn et al suggest a method to decrease the difference between the DSC and DMTA values by adopting a new DMTA T g definition. [37][38] A much deeper understanding of the relationship between different measures of the glass transition is necessary, but it is not within the scope of the research done here.…”

Section: Physical Agingmentioning

confidence: 99%

Mechanical property changes and degradation during accelerated weathering of polyester-urethane coatings

Skaja

Fernando

Croll

2006

J Coat. Technol. Res.

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Chemical changes, measured using spectroscopy, and crosslink density, measured by mechanical thermal analysis, were determined during accelerated weathering on a model polyester-urethane coating of known composition. The tensile modulus, measured above the glass transition temperature, and thus the crosslink density, decreased with exposure, as expected from the chemical changes. However, the tensile modulus, measured at room temperature, increased with exposure. Physical aging of the polymer network was found to occur concurrently with photodegradation and accounts for much of the increase in room temperature modulus. Increased hydrogen bonding in the increasingly oxidized polyesterurethane may also contribute to the increase in modulus at room temperature. Both physical and chemical changes must be determined if changes, and rates of change, in performance due to weathering are to be understood. C oatings are used in many applications and environments where high levels of durability are required. Often, the requirements include maintenance of appearance, barrier properties, toughness, etc. during exposure to natural weathering, which includes solar ultraviolet radiation, heat, moisture, and pollutants. In many cases, the lifetime of the coating is determined by a change in appearance, but crucial equipment may rely on the protective properties of the coating. However, understanding the relationship between coating composition and how it changes during exposure and how that is related to macroscopic end-use properties remains a fertile field of research. Many protective attributes of a coating can be related to its mechanical integrity, e.g., chemical and corrosion protection depend crucially on whether a coating remains intact and continuous during service. Cracks or adhesion failures due to in-service stresses immediately define the useful service life of a coating. These macroscopic failures are the accumulations of, or initiated by, the erosion processes that result from chemical changes during degradation.Understanding how the mechanical integrity of a coating, or any construction material, changes under exposure is very important. However, mechanical measurements, while relating closely to end-use and service life, are not directly linked to the chemical changes in the material and, thus, how the environment affects a polymer. It is necessary to examine the chemical changes, relate those to changes in the polymer network, and include any other physical changes that occur before understanding the important factors that determine the macroscopic mechanical properties of a coating.There has been a great deal of excellent basic work done in determining the chemical changes that occur during degradation of a particular coating's chemistry. Unfortunately, further progress towards connecting that information with macroscopic properties has often been hindered by examining commercial polymers that are undisclosed complex mixtures of functionality and composition. This work examines model polyester-urethane systems...

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Section: Physical Agingmentioning

confidence: 99%

Mechanical property changes and degradation during accelerated weathering of polyester-urethane coatings

Skaja

Fernando

Croll

2006

J Coat. Technol. Res.

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“…More specifically, the onset of the thermal transition from a glassy to elastomeric material occurs at approximately the same temperature and the rubbery moduli, which are proportional to the crosslink density, are similar. The temperature at the tan δ maximum (assigned here as the T g )22–23 demonstrates that both allyl and propyl sulfide-based materials exhibit super-ambient T g s (allyl sulfide-based system: 41 ± 1ºC, propyl sulfide-based system: 39 ± 1ºC ). Overall, the similarity of these networks indicates that the propyl sulfide addition to the MeDTBY enables this system to serve as an excellent control for which the only significant differences in material behavior should all be related to the simultaneous AFCT-polymerization mechanism rather than differences in the network structure.…”

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confidence: 99%

Stress Relaxation by Addition−Fragmentation Chain Transfer in Highly Cross-Linked Thiol−Yne Networks

et al. 2010

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Radical mediated addition-fragmentation chain transfer of mid-chain allyl sulfide functional groups was utilized to reduce polymerization-induced shrinkage stress in thiol-yne step-growth photopolymerization reactions. In previous studies, the addition-fragmentation of allyl sulfide during the polymerization of a step-growth thiol-ene network demonstrated reduced polymerization stress; however, the glass transition temperature of the material was well below room temperature (~ −20°C). Many applications require super-ambient glass transition temperatures, such as microelectronics and dental materials. Polymerization reactions utilizing thiol-yne functional groups have many of the advantageous attributes of the thiol-ene-based materials, such as possessing a delayed gel-point, resistant to oxygen inhibition, and fast reaction kinetics, while also possessing a high glass transition temperature. Here we incorporate allyl sulfide functional groups into a highly crosslinked thiol-yne network to reduce polymerizationinduced shrinkage stress. Simultaneous shrinkage stress and functional group conversion measurements were performed during polymerization using a cantilever-type tensometer coupled with a FTIR spectrometer. The resulting networks were highly crosslinked, possessed superambient glass transition temperatures, and exhibited significantly reduced polymerization-induced shrinkage stress when compared with analogous propyl sulfide-containing materials that are incapable of addition-fragmentation.Polymerization of multifunctional monomers yields crosslinked polymeric networks (i.e., thermosets) that are extensively utilized in applications ranging from coatings and adhesives to dental materials and microelectronics [1][2][3] . Unfortunately, these polymerizations are also typically accompanied by significant amounts of volumetric shrinkage 4 , where the associated stress that arises, leading to a wide range of deleterious effects such as material warping and cracking. Mitigation of this polymerization-induced shrinkage and/or the associated stress has been the focus of extensive research efforts over the past several decades 5-6 and several methods, including ring-opening polymerization 7 , thiol-ene polymerizations 8 , and polymerization-induced phase separation 9 .One approach to mitigate shrinkage stress was recently conceived whereby minimization of polymerization shrinkage itself is not directly addressed. Rather, the network connectivity continuously rearranges during the polymerization, thus promoting network relaxation and alleviating polymerization shrinkage stress to establish these materials as covalent adaptable networks [10][11] . This network connectivity rearrangement approach is realized via radical-* Corresponding author, christopher.bowman@colorado.edu. NIH Public Access Author ManuscriptMacromolecules. Author manuscript; available in PMC 2011 July 13. NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript mediated, addition-fragmentation chain transfer (i.e., AFCT) th...

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“…The MAEs for the predicted results estimated by SVR were less than those of QSPR for both the training set and validation set. Thus, the prediction errors for the calculations based on [8,34,35] or even over 10 degrees [36] in T g values of a polymer measured by different experimental techniques. These imply that the established SVR model can be used, in practice, to satisfactorily predict the T g of an unknown structurally similar polymer outside of the training set.…”

Section: Resultsmentioning

confidence: 99%

Prediction of the Glass Transition Temperatures of Styrenic Copolymers by Using Support Vector Regression Combined with Particle Swarm Optimization

Pei

Cai

Tang

et al. 2011

Journal of Macromolecular Science, Part B

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Based on three quantum chemical descriptors (the average polarizability of a molecule (α), the most positive net atomic charge on hydrogen atoms in a molecule (q + ) and the heat capacity at constant volume (C v ) derived from the monomers using the density functional theory (DFT), the support vector regression (SVR) approach combined with particle swarm optimization (PSO), is proposed to establish a model for prediction of the glass transition temperature (T g ) of random copolymers including poly(styrene-co-acrylamide) (SAAM), poly(styrene-co-acrylic acid) (SAA), poly(styrene-co-acrylonitrile) (SAN), poly(styrene-co-butyl acrylate) (SBA), poly(styrene-co-methyl acrylate) (SMA), poly(styrene-co-ethyl acrylate) (SEA), and poly(acrylonitrile-co-methyl acrylate) (ANMA). The mean absolute error (MAE = 1.6 K), mean absolute percentage error (MAPE = 0.45%), and correlation coefficient (R 2 = 0.9978) calculated by SVR model are superior to those (MAE = 5.47 K, MAPE = 1.51%, and R 2 = 0.9829) achieved by a quantitative structure-property relationship (QSPR)/multivariate linear regression (MLR) model for the identical training set, whereas the MAE = 3.03 K, MAPE = 0.90%, and R 2 = 0.9952 calculated by SVR also outperform those (MAE = 5.38 K, MAPE = 1.61%, and R 2 = 0.9778) achieved by the QSPR/MLR model for the identical validation set, respectively. The prediction results strongly support that the modeling and generalization ability of the SVR model consistently surpasses that of the QSPR/MLR model by applying identical training and validation samples. It is demonstrated that the established SVR model is more suitable to be used for prediction of the T g values for unknown polymers possessing similar structure than the conventional MLR model. It is also shown that the hybrid PSO-SVR approach is a promising and practical methodology to predict the glass transition temperature of styrenic copolymers.

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Comparison of thermal techniques for glass transition assignment. II. Commercial polymers

Cited by 29 publications

References 1 publication

Mechanical property changes and degradation during accelerated weathering of polyester-urethane coatings

Mechanical property changes and degradation during accelerated weathering of polyester-urethane coatings

Stress Relaxation by Addition−Fragmentation Chain Transfer in Highly Cross-Linked Thiol−Yne Networks

Prediction of the Glass Transition Temperatures of Styrenic Copolymers by Using Support Vector Regression Combined with Particle Swarm Optimization

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