Principles of Polymer Chemistry

Ravve, A.

doi:10.1007/978-1-4899-1283-1

Cited by 64 publications

(42 citation statements)

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“…Thus, it is necessary to characterize lignin in terms of average molecular weight. Two common averages used are number average molecular weight (M n ) and weight average molecular weight (M w ) (Eqns and ) . The polydispersity index (D) represents the molecular weight distribution of the polymers (Eqn ) …”

Section: Definition Of Average Molecular Weights Of Ligninmentioning

confidence: 99%

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Characterization and analysis of the molecular weight of lignin for biorefining studies

Tolbert

Akinosho

Khunsupat

et al. 2014

Biofuels Bioprod Bioref

378

250

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The molecular weight of lignin is a fundamental property that influences the recalcitrance of biomass and the valorization of lignin. The determination of the molecular weight of lignin in native biomass is dependent on the bioresources used and the isolation and purification procedures employed. The three most commonly employed isolation methods are milled wood lignin (MWL), cellulolytic enzyme lignin (CEL), and enzymatic mild acidolysis lignin (EMAL). Common characterization techniques for determining the molecular weight of lignin will be addressed, with an emphasis on gel permeation chromatography (GPC). This review also examines the mechanisms behind several biological, physical, and chemical pre‐treatments and their impact on the molecular weight of lignin. The number average molecular weight (Mn), weight average molecular weight (Mw) and polydispersity index (D) all vary in magnitude depending on the biomass source, pre‐treatment conditions, and isolation method. Additionally, there is a growing body of literature that supports changes in the molecular weight of lignin in response to genetic modifications in the lignin biosynthetic pathways. This review summarizes different procedures for obtaining the molecular weight of lignin that have been used in recent years and highlight future opportunities for applications of lignin. © 2014 Society of Chemical Industry and John Wiley & Sons, Ltd

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Section: Definition Of Average Molecular Weights Of Ligninmentioning

confidence: 99%

“…Here the index number, i , represents the number of different molecular weights present in the lignin sample and N i is the total number of moles with the molar mass of M i …”

Section: Definition Of Average Molecular Weights Of Ligninmentioning

confidence: 99%

Characterization and analysis of the molecular weight of lignin for biorefining studies

Tolbert

Akinosho

Khunsupat

et al. 2014

Biofuels Bioprod Bioref

378

250

View full text Add to dashboard Cite

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“…They become part of the network structure and affect the viscosity and the reactivity of the formulation. Via curing with initiators the homopolymerization of the resin is effectuated . The type of curing agent defines the kind of chemical bonds, which are formed, and therefore the basic structure and the functionality of the cross‐linked matrix.…”

Section: Introductionmentioning

confidence: 99%

Improvement of fracture toughness and glass transition temperature of DGEBA‐based epoxy systems using toughening and crosslinking modifiers

Utaloff

Kothmann

Ciesielski

et al. 2018

Polymer Engineering & Sci

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Several toughening and crosslinking modifiers were tested in two epoxy resin systems based on the diglycidyl ether of bisphenol A (DGEBA) with the objective to improve the critical stress intensity factor KIC and the glass transition temperature (Tg) simultaneously. An amine hardener (isophorone diamine (IPD)) and a homopolymerization initiator (1‐ethyl‐3‐methylimidazolium acetate (EMIM Ac)) were used as curing agents. The highest effect on the KIC value of the resin system DGEBA/IPD (KIC = 0.72 MPa1/2; Tg = 164°C) was achieved with the dendric polymer Boltorn P501 (10 wt%), but it decreased the Tg (KIC = 1.39 MPa1/2; Tg = 136°C). A high toughening effect with a low decrease of Tg was achieved with a combination of a self‐organized block copolymer (Nanostrength M22N) and silica nanoparticles (Nanopox F400) (KIC =1.15 MPa1/2; Tg =157°C). The KIC value of the resin system DGEBA/EMIM Ac was improved from 0.44 to 0.66 MPa1/2. An improvement of both, the thermal and mechanical properties was established for a combination of a poly(tetrahydrofuran) as toughening modifier (PolyTHF2000) with the post‐crosslinking modifier diethylphosphite (DEP) in the resin system DGEBA/IPD (KIC = 0.86 MPa1/2; Tg = 180°C). A system with chemical linkages between both modifiers was investigated for comparison but yielded inferior results. POLYM. ENG. SCI., 59:86–95, 2019. © 2018 Society of Plastics Engineers

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“…Using these two data points and solving for the water–copovidone interaction parameter, we obtained an estimated value of around 0.8. This value, being slightly larger than the critical value of 0.5 for polymer solutions, suggested that the mixing of copovidone with water was slightly unfavorable. This result could be compared to the previously reported χ value of 0.36 for the pure hydrophilic poly(vinyl pyrrolidone); this indicated slightly better mixing favorability with water .…”

Section: Resultsmentioning

confidence: 80%

Impact of moisture and plasticizer properties on polymer–plasticizer physical mixing performance

Sun

Chen

2014

J of Applied Polymer Sci

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The ability for polymers and additives to physically mix in many industrial applications is dictated by a combination of kinetic and thermodynamic factors. The presence of moisture may complicate the mixing performance as water can interact at various degrees with each of the components; this depends on the hydrophilicity of the materials. In this study, the physical mixing behavior of a ternary system consisting of a hygroscopic polymer (copovidone), a plasticizer, and water was examined. Three different liquid plasticizers with a range of hydrophilic-lipophilic properties and viscosities were evaluated for their physical mixing performance and the impact of their water content. Inverse gas chromatography was introduced as a new method for measuring the surface characteristics of the physical mixtures to quantify the mixing performance. Through the application of the Flory-Huggins model to understand the thermodynamic behavior of the system, it was shown that mixing was less effective in a system of high water content for a hydrophobic plasticizer. However, the underlying thermodynamic unfavorability of such a system could be overcome by kinetic influence to provide a good mixing performance. Specifically, as the viscosity of the plasticizer decreased, the influence of the thermodynamic characteristics was found to become less apparent.

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Principles of Polymer Chemistry

Cited by 64 publications

References 0 publications

Characterization and analysis of the molecular weight of lignin for biorefining studies

Characterization and analysis of the molecular weight of lignin for biorefining studies

Improvement of fracture toughness and glass transition temperature of DGEBA‐based epoxy systems using toughening and crosslinking modifiers

Impact of moisture and plasticizer properties on polymer–plasticizer physical mixing performance

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