Determination of molecular parameters of NR/PU block copolymers by transport studies

Gopakumar, S.; Nair, M. R. Gopinathan

doi:10.1016/j.eurpolymj.2005.04.002

Cited by 15 publications

(14 citation statements)

References 16 publications

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“…Physical crosslinks are the entanglements and also the point of secondary bond interactions. 8 The trend observed in the experimentally calculated M c is in agreement with the trend observed in theoretically obtained values to some extent. As the diol/crosslinker ratio increases, M c increases in both cases.…”

Section: Diffusion Processsupporting

confidence: 91%

“…The deviations were also observed within the different solvents and the extent of deviation was more for the solvents with which the polymer has lesser interaction. Similar results have been reported earlier 2,8,18 and may be because of limitations of the FloryRhener theory for heterogeneous system like PU comprising of hard and soft segments. The complexity of polymer-solvent interaction affects the microdomain structure of PU to different extents.…”

Section: Diffusion Processsupporting

confidence: 88%

“…For the solvents under study, it is observed that chlorobenzene has the closest solubility parameter to the polymers, and hence shows highest swelling coefficient (Table III). Solubility parameter was also calculated from the following equation 8 representing Gee's theory.…”

Section: Diffusion Processmentioning

confidence: 99%

“…Nair et al 8 have carried out swelling experiments of block copolymers based on natural rubber as soft segment and PU derived from toluene diisocyanate and 1,3-butane diol (1,3-BDO) as hard segment in various solvents. Block copolymers with different NCO/ OH ratio, viz., from 1.26 to 1.96 were employed in this study.…”

Section: Introductionmentioning

confidence: 99%

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Sorption behavior of biodegradable polyurethanes with carbohydrate crosslinkers

Lalwani

Desai

2009

J of Applied Polymer Sci

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Polyether-polyurethanes (PUs) with a series of carbohydrate crosslinkers: monosaccharide (glucose), disaccharide (fructose) and polysaccharide (starch), were synthesized. The kinetics of swelling was studied in industrially important solvents like toluene, xylene and chlorobenzene. The R value and diol / triol ratio were varied to study the effect on crosslink density and sorption. It was observed that the swelling extent increased with increasing concentration of crosslinker in the polymer. Interestingly the effect of diisocyanate concentration on extent of sorption varied with the type of carbohydrate used for crosslinking. Considering the effect of diisocyanate concentration, the PUs containing disaccharide sucrose showed greater solvent uptake. Though the sorption behaviours were different, the solubility parameters of all PUs were the same irrespective of the type and concentration of the crosslinkers. All the PUs were observed to be biodegradable with glucose containing PUs exhibiting highest weight loss. Scanning electron microscope revealed absence of phase segregation in all the PU systems.

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Section: Diffusion Processsupporting

confidence: 91%

Section: Diffusion Processsupporting

confidence: 88%

Section: Diffusion Processmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Sorption behavior of biodegradable polyurethanes with carbohydrate crosslinkers

Lalwani

Desai

2009

J of Applied Polymer Sci

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“…Entretanto, em acetona, um elevado índice de inchamento foi observado. Esse comportamento pode estar relacionado à semelhança entre os parâmetros de solubilidade dos poliuretanos (9,3 a 9,5 (cal cm -3 )1/2) [25,27] e da acetona (9,9 (cal.cm -3 )1/2) [28,29] .…”

Section: Resistência Químicaunclassified

Efeito da concentração de segmentos rígidos nas propriedades físico-mecânicas, químicas e na morfologia de elastômeros microcelulares de poliuretano

Pacheco

Fiório²,

Zattera³

et al. 2007

Polímeros

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Resumo: Neste trabalho, foram preparados três diferentes elastômeros microcelulares de poliuretano (EMPU) baseados em 4,4'-diisocianato de difenilmetano (MDI), com diferentes concentrações de fase rígida (Formulações 1, 2 e 3, com 32, 35 e 42% de fase rígida, respectivamente). As amostras foram preparadas através do método de duas etapas, pelo sistema de pré-polímero. As amostras dos EMPU foram caracterizadas através de ensaios físico-mecânicos, químicos e morfológicos. Os resultados dos ensaios mecânicos mostraram que o aumento no percentual da fase rígida levou a um aumento na resistência à tração e na resistência ao rasgo. O alongamento na ruptura não apresentou variação significativa com a modificação do percentual da fase rígida. O ensaio de resistência química demonstrou que os EMPU formulados apresentaram baixos índices de inchamento para solventes industriais comumente utilizados. Entretanto, em acetona, um elevado índice de inchamento foi observado. As análises morfológicas indicaram que o aumento no percentual da fase rígida promoveu a formação de células menores distribuídas de forma mais homogênea no EMPU. Palavras-chave: Elastômero microcelular de poliuretano, propriedades mecânicas, microscopia eletrônica de varredura. Effect of rigid Segment content on the Physical, Mechanical, Chemical and Morphological Properties of Microcellular Polyurethane ElastomersAbstract: In this study, three different microcellular polyurethane elastomers (MPUE) based on 4,4'-diphenylmethane diisocyanate (MDI) with different rigid segment contents were prepared (Formulations 1, 2 and 3 with 32, 35 and 42% of rigid segment content, respectively). The MPUE were obtained through a two-step method using the prepolymer system. The samples were analyzed to determine their physical, mechanical, morphological and chemical properties. The results showed that a greater rigid segment content gave higher tensile, compressive and tear strength values. The deformation at break did not show significant changes with a variation in the rigid segment content. The MPUE had a low swelling index in common industrial solvents. However, in acetone a high swelling index was observed. The SEM micrographs indicated a large number of closed cells, and that a higher rigid segment content gave a better cell homogeneity of the samples. Keywords: Microcellular polyurethane elastomers, mechanical properties, scanning electron microscopy. IntroduçãoOs poliuretanos (PUs) são considerados como copolímeros em bloco segmentados, formados pela reação de poliadição entre diisocianatos, polióis e extensores de cadeia [1][2][3] . Os mesmos são constituídos por segmentos rígidos e flexíveis [4,5] . A reação entre diisocianato e extensores de cadeia forma o segmento rígido, enquanto que o poliol é responsável pelo segmento flexível [2,4,5] .Os elastômeros microcelulares de poliuretano (EMPU) são materiais que resistem a condições severas encontradas em diversas aplicações, como em automóveis e máquinas industriais [7,8] . Os mesmos apresentam uma densidade apare...

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3D Printing of High Viscosity UV‐Curable Resin for Highly Stretchable and Resilient Elastomer

Huang,

Peng,

Zheng

et al. 2023

Advanced Materials

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Vat photopolymerization prepared elastomers usually exhibit unsatisfied mechanical properties due to their insufficient growth of molecular weight upon UV exposure. Increasing the weight ratio of oligomer in the resin system is an effective approach to enhance the mechanical properties, yet the viscosity of the UV‐curable resin increased dramatically which makes it difficult to be used. Here, a linear scan‐based vat photopolymerization (LSVP) system which can print high‐viscosity resin was carried out to 3D print the oligomer‐dominated UV‐curable resin via a dual‐curing mechanism. Briefly, a polyurethane methacrylate blocking (PUB) oligomer is first synthesized and then mixed with a commercialized bifunctional oligomer, photoinitiator, and primary amine as a chain extender to prepare high‐viscosity UV‐curable resin for LSVP system. Through thermal treatment, deblocked isocyanate is further crosslinked with a chain extender to construct a highly entangled polymer chain network. The optimal thermal treatment parameters are investigated. Simultaneously, the resilience of the 3D‐printed elastomer was evaluated by continuous tensile loading and unloading tests. Subsequently, complex structured elastomers were printed, exhibiting favorable mechanical durability without defects. The results obtained from this work will provide a reference for preparing elastomeric devices with excellent physical properties and expand the application fields of vat photopolymerization.This article is protected by copyright. All rights reserved

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Determination of molecular parameters of NR/PU block copolymers by transport studies

Cited by 15 publications

References 16 publications

Sorption behavior of biodegradable polyurethanes with carbohydrate crosslinkers

Sorption behavior of biodegradable polyurethanes with carbohydrate crosslinkers

Efeito da concentração de segmentos rígidos nas propriedades físico-mecânicas, químicas e na morfologia de elastômeros microcelulares de poliuretano

3D Printing of High Viscosity UV‐Curable Resin for Highly Stretchable and Resilient Elastomer

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