Polycondensation

Costa, Mário Rui P. F. N.; Bachmann, Rolf

doi:10.1002/9783527619870.ch3

Cited by 6 publications

(5 citation statements)

References 236 publications

(201 reference statements)

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“…Traditionally, the production of polyethers by polycondensation has been achieved by Williamson polyetherification via a nucleophilic substitution reaction between an alkoxide and a halogenated alkane . But the advantage of the self-condensation is that water is produced as side product, while in the Williamson etherification chloride is generated during the polymerization . Thus, different companies have started to commercialize polyethers which are otherwise typically petrochemical-sourced.…”

Section: Aliphatic Polyether Polyolsmentioning

confidence: 99%

From Lab to Market: Current Strategies for the Production of Biobased Polyols

Sardón

Mecerreyes

Basterretxea

et al. 2021

ACS Sustainable Chem. Eng.

122

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The global market for polyols was US$26.2 billion in 2019 and is expected to grow up to US$34.4 billion by 2024. Polyols are most commonly employed as the main component in the synthesis of polyurethanes, which is the sixth most important polymer family produced with a global production that reached around 22 Mt in 2019. In the interest of improving the sustainability of the polyurethane industry, for more than a decade the market has undergone a shift toward biobased polyols made from renewable resources. For this reason, the demand of biobased polyols has grown rapidly and offers new opportunities to valorize biomass into technical grade polyols for the polyurethane industry. This Perspective aims to summarize current strategies to produce polyols from biomass and the problems associated with their market implementation. Different natural resources, including lignocellulose, lipids, or carbohydrates for the synthesis of biobased polyester- or polyether-based polyols and polyphenols will be reviewed. Subsequently, the gaps that are currently preventing the transition from academic laboratories to industrial plants will be commented upon, highlighting in particular the use of nonscalable chemical transformations and the lack of competitive biobased raw material suppliers. Finally, a case study of the issues associated with the scale-up process of novel biobased polyols will be discussed in detail.

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Section: Aliphatic Polyether Polyolsmentioning

confidence: 99%

From Lab to Market: Current Strategies for the Production of Biobased Polyols

Sardón

Mecerreyes

Basterretxea

et al. 2021

ACS Sustainable Chem. Eng.

122

View full text Add to dashboard Cite

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“…Mejdell and Schønsby 19 have slightly extended the Kumar-Sood model 21 now including condensation reactions and achieved a good agreement with their limited experimental data, but it should be noticed that their rate equations in terms of functional groups do not reflect the correct situation concerning the reverse reactions. A slightly more consistent model has been proposed by Costa and Bachmann, 22 but as it is discussed in that same reference, it only takes into account FSSE effects. The use of second and higher order substitution effects in models of reversible polymerizations requires the simulation of the whole isomer distribution, 22 and this makes such models difficult to use.…”

Section: Introductionmentioning

confidence: 93%

“…A slightly more consistent model has been proposed by Costa and Bachmann, 22 but as it is discussed in that same reference, it only takes into account FSSE effects. The use of second and higher order substitution effects in models of reversible polymerizations requires the simulation of the whole isomer distribution, 22 and this makes such models difficult to use.…”

Section: Introductionmentioning

confidence: 93%

A very simple empirical kinetic model of the acid‐catalyzed cure of urea–formaldehyde resins

Carvalho

Costa

2006

J of Applied Polymer Sci

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ABSTRACT:The hot pressing operation is the final stage in MDF (medium density fiberboard) manufacture; the fiber mat is compressed and heated up to promote the cure of the resin. The aim of the investigations is to study the curing reactions of UF (Urea-Formaldehyde) resins as commonly used in the production of MDF, and to develop a simplified kinetic model. This investigation has combined Raman spectroscopy to study the reaction cure and 13 C-NMR for the quantitative and qualitative characterization of the liquid and still uncured resin. Raman spectroscopy was found very interesting for the study of the resin cure and permitted to obtain kinetic data as the basis for a simple empirical model, considering a homogeneous irreversible reaction of a single kind of methylol group and ureas with rate constants depending on their degree of substitution. Although these results can provide a better understanding of the composition and the cure of an UF resin, several issues remain open, such as the influence of the reversibility of the reactions taking place during the curing process as well as the possible formation of cyclic groups in the resin.

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“…The synthesis of the first synthetic step-growth polymeric material, i.e., bakelite, which was introduced in 1907 by Leo Baekeland, considered phenol and formaldehyde groups as the building blocks [ 6 ]. The largest-volume polymers made via step-growth polymerization are polyesters and polyamides, with main applications as the production of fibers, wire coatings and composites [ 1 , 7 , 8 , 9 , 10 , 11 ]. Well-known examples are polyester plastic bottles made from poly(ethylene terephthalate) and polyamide nylon 6,6.…”

Section: Introductionmentioning

confidence: 99%

“…Furthermore, polycarbonates are used as digital-storage-media substrates and for electronic devices due to their transparency and high toughness [ 1 , 12 ]. Other commercial examples are polyurethanes and cured epoxy resins [ 11 , 13 ].…”

Section: Introductionmentioning

confidence: 99%

Going Beyond the Carothers, Flory and Stockmayer Equation by Including Cyclization Reactions and Mobility Constraints

et al. 2021

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A challenge in the field of polymer network synthesis by a step-growth mechanism is the quantification of the relative importance of inter- vs. intramolecular reactions. Here we use a matrix-based kinetic Monte Carlo (kMC) framework to demonstrate that the variation of the chain length distribution and its averages (e.g., number average chain length xn), are largely affected by intramolecular reactions, as mostly ignored in theoretical studies. We showcase that a conventional approach based on equations derived by Carothers, Flory and Stockmayer, assuming constant reactivities and ignoring intramolecular reactions, is very approximate, and the use of asymptotic limits is biased. Intramolecular reactions stretch the functional group (FG) conversion range and reduce the average chain lengths. In the likely case of restricted mobilities due to diffusional limitations because of a viscosity increase during polymerization, a complex xn profile with possible plateau formation may arise. The joint consideration of stoichiometric and non-stoichiometric conditions allows the validation of hypotheses for both the intrinsic and apparent reactivities of inter- and intramolecular reactions. The kMC framework is also utilized for reverse engineering purposes, aiming at the identification of advanced (pseudo-)analytical equations, dimensionless numbers and mechanistic insights. We highlight that assuming average molecules by equally distributing A and B FGs is unsuited, and the number of AB intramolecular combinations is affected by the number of monomer units in the molecules, specifically at high FG conversions. In the absence of mobility constraints, dimensionless numbers can be considered to map the time variation of the fraction of intramolecular reactions, but still, a complex solution results, making a kMC approach overall most elegant.

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Polycondensation

Cited by 6 publications

References 236 publications

From Lab to Market: Current Strategies for the Production of Biobased Polyols

From Lab to Market: Current Strategies for the Production of Biobased Polyols

A very simple empirical kinetic model of the acid‐catalyzed cure of urea–formaldehyde resins

Going Beyond the Carothers, Flory and Stockmayer Equation by Including Cyclization Reactions and Mobility Constraints

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