Synthesis and characterization of new liquid, branched and random poly(methylhydrosiloxanes)

Flexible, self-extinguishing silicone foams (SFs) with a relatively low density (0.25-0.45 g/cm 3 ) were obtained from a mixture of a,x-(dihydroxy)polydimethylsiloxanes, water, flame retardants (melamine and/or expanded graphite), and polyisocyanates [poly(diphenylmethane isocyanate)]. These compositions were crosslinked at room temperature with branched polymethylhydrosiloxanes with the structure (MeSiO 1.5 ) 3 (MeHSiO) 102 (Me 3 SiO 0.5 ) 5 in the presence of tin octoate as a catalyst. The SFs were modified by the addition of linear or graft carbofunctional polysiloxanes containing chydroxypropyl groups. Only the SFs prepared by means of a dehydrocondensation reaction had a good homogeneity of pores, whereas the foams formed with two kinds of blowing agents (hydrogen and carbon dioxide, generated in the reaction of water with isocyanate groups) had lower densities but a poor homogeneity of pores. Unmodified SFs showed a tensile strength of 20 kPa or less, whereas the foams formed with the addition of poly(diphenylmethane isocyanate) and water had a tensile strength of 23-25 kPa. The SFs with 15 and 30% contents of melamine or expanded graphite had tensile strengths in the ranges 38-45 and 51-54 kPa, respectively. All of the prepared SFs were combustible materials. The SFs without the addition of flame retardants had a limiting oxygen index of approximately 21%, whereas the SFs with a 30% content of fire retardant had self-extinguishing properties and a limited oxygen index of 41-43%.

show abstract

“…A polymethylhydrosiloxane with a branched, random structure (T‐3) was used as the crosslinking agent; its general formula was T 3 D

_{102}^{H}

M 5 (where T is MeSiO 1.5 , D H is MeHSiO, and M is Me 3 SiO 0.5 ) 35…”

Section: Methodsmentioning

confidence: 99%

Preparation of flexible, self‐extinguishing silicone foams

Chruściel

Leśniak

2010

J of Applied Polymer Sci

View full text Add to dashboard Cite

show abstract

“…Hydrogen atoms and methyl groups are the main substituents of silicon atoms in PMHS; however, other organic groups may be attached to silicon atoms in their structures as well. Most PMHS are colorless oils, though some of them are solids [1,2,3,4,5,6,7,8,9]. Linear, star, hyperbranched and dendritic poly(methylhydrosiloxanes), as well as spherical hydrosilicates, are important classes of functional silicones.…”

Section: Introductionmentioning

confidence: 99%

“…Linear, star, hyperbranched and dendritic poly(methylhydrosiloxanes), as well as spherical hydrosilicates, are important classes of functional silicones. Many methods of their preparation were described in our previous publication, concerning synthesis and characterization of branched PMHS containing triple branching units MeSiO 1.5 (T) [ 9 ]. PMHS find numerous practical applications.…”

Section: Introductionmentioning

confidence: 99%

“…PMHS find numerous practical applications. Most often they are used as cross-linking agents in a technology of silicone elastomers [ 9 , 10 , 11 , 12 , 13 , 14 , 15 ].…”

Section: Introductionmentioning

confidence: 99%

“…The starting monomer c-D 2 D H was prepared by heterocondensation of MeHSiCl 2 with HO(Me 2 SiO) 2 H (yield: 49%). At the same time was elaborated a new sequential polycondensation method (“one-pot”) leading to three homological series of new PDMS- b -PMHS with a general formula: RMe 2 SiO[(Me 2 SiO) m (MeHSiO) k ] n (Me 2 SiO) m SiMe 2 R, (where: R = –OH or –Me; m = 2, 6, 10, 14, ~50; k = 1–4; n = 5, 10, 15, 20), containing single or multiple MeHSiO units in macromolecules [ 9 , 24 ]. This synthetic method is based on a non-stoichiometric polycondensation of appropriate dimethylsiloxane-α,ω-diols HO(Me 2 SiO) m H with siloxane oligomers of a general formula Cl(MeHSiO) k-1 SiHMeCl, having chloro(hydro)silyl functionalities, followed by termination reactions with chlorotrimethylsilane Me 3 SiCl, when PDMS- b -PMHS chains were blocked with (CH 3 ) 3 SiO 0.5 (M) groups.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Synthesis, Characterization and Microstructure of New Liquid Poly(methylhydrosiloxanes) Containing Branching Units SiO4/2

2018

Self Cite

View full text Add to dashboard Cite

Six liquid branched poly(methylhydrosiloxanes) of new random structures (PMHS-Q), containing quadruple branching units SiO4/2 (Q), both MeHSiO (DH) and Me2SiO (D) chain building units (or only mers MeHSiO), and terminal groups Me3SiO0.5 (M) were prepared by a hydrolytic polycondensation method of appropriate organic chlorosilanes and tetraethyl ortosilicate (TEOS), in diethyl ether medium at temperature below 0 °C. Volatile low molecular weight siloxanes were removed by a vacuum distillation at 150–155 °C. Yields of PMHS-Q reached from 55–69 wt%. Their dynamic viscosities were measured in the Brookfield HBDV+IIcP cone-plate viscometer and ranged from 10.7–13.1 cP. Molecular weights (MW) of PMHS-Q (Mn = 2440–6310 g/mol, Mw = 5750–10,350 g/mol) and polydispersities of MW (Mw/Mn = 2.0–2.8) were determined by a size exclusion chromatography (SEC). All polymers were characterized by FTIR, 1H- and 29Si-NMR, and an elemental analysis. A microstructure of siloxane chains was proposed on a basis of 29Si-NMR results and compared with literature data.

show abstract

Hydrosilyl-Functional Polysiloxanes: Synthesis, Reactions and Applications

Chruściel

2020

Reactive and Functional Polymers Volume One

View full text Add to dashboard Cite

Synthesis and characterization of new liquid, branched and random poly(methylhydrosiloxanes)

Cited by 4 publications

References 28 publications

Preparation of flexible, self‐extinguishing silicone foams

Preparation of flexible, self‐extinguishing silicone foams

Synthesis, Characterization and Microstructure of New Liquid Poly(methylhydrosiloxanes) Containing Branching Units SiO4/2

Hydrosilyl-Functional Polysiloxanes: Synthesis, Reactions and Applications

Contact Info

Product

Resources

About