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A series of new flame retardants (FR) based on dibenzo[d,f][1,3,2]dioxaphosphepine 6-oxide (BPPO) incorporating acrylates and benzoquinone were developed previously. In this study, we examine the fire behavior of the new flame retardants in polyisocyanurate (PIR) foams. The foam characteristics, thermal decomposition, and fire behavior are investigated. The fire properties of the foams containing BPPO-based derivatives were found to depend on the chemical structure of the substituents. We also compare our results to state-of-the-art non-halogenated FR such as triphenylphosphate and chemically similar phosphinate, i.e. 9,10-dihydro-9-oxa-10- phosphaphenanthrene-10-oxide (DOPO), based derivatives to discuss the role of the phosphorus oxidation state.
As a potential substitute for currently used halogenated flame retardants we explored the synthesis of dibenzo[d,f][1,3,2]dioxaphosphepine 6-oxide (BPPO) and derivatives. BPPO is a cyclic phosphonate and was synthesized by a simple, three-component condensation using 2,2´-biphenol, phosphorus trichloride and water by improving a procedure given by Natchev. Subsequently, BPPO was employed in phospha-Michael additions in line with the known synthesis of DOPO-compounds to double bonds. These reactions result in novel phosphorus-containing compounds with flame retardant activíty. The chemical structure of the unsaturated compounds was systematically varied yielding non-reactive flame retardants (without functional groups) from acrylates and diesters, and reactive (with functional groups) flame retardants from p-benzoquinone. The use of the phosphonate BPPO and its derivatives as flame retarding additives has not been described yet. The BPPO ring is highly reactive. Therefore, it is supposed that it mainly acts in the gas phase.
The new phosphonates were applied as additives for improving the flame retardancy of rigid PUR/PIR foams with triethyl phosphate (TEP) as plasticizer. The foam characteristics like density, cell integrity, pore size and mechanical properties were investigated. The burning properties of the foams were analyzed in the vertical flame spread according to DIN 4102 and by cone calorimetry. The relevant parameters depended on the phosphorus content, which is illustrated for PIR foams with ethyl 3-(6-oxidodibenzo[d,f][1,3,2]dioxaphosphepin-6-yl)propanoate (X, Z = H; Y = OEt; EA-BPPO) as FR additive.
At comparable P-content, the EA-BPPO additive reached the PHHR-values of the benchmark foam with TEP and triphenyl phosphate as FR additive. With increased P-content the values were further reduced. TML and MARHE parameters showed a similar tendency. The FR additives dispersed well in the formulation and had no significant influence on foam density, cell integrity and pore size compared to the reference sample.
The conventional hybridoma screening and subcloning process is generally considered to be one of the most critical steps in hapten-specific antibody production. It is time-consuming, monoclonality is not guaranteed, and the number of clones that can be screened is limited. Our approach employs a novel hapten-specific labeling technique of hybridoma cells. This allows for fluorescence-activated cell sorting (FACS) and single-cell deposition and thereby eliminates the above-mentioned problems. A two-step staining approach is used to detect antigen specificity and antibody expression: in order to detect antigen specificity, hybridoma cells are incubated with a hapten−horseradish peroxidase conjugate (hapten−HRP), which is subsequently incubated with a fluorophore-labeled polyclonal anti-peroxidase antibody (anti-HRP−Alexa Fluor 488). To characterize the expression of membrane-bound immunoglobulin G (IgG), a fluorophore-labeled anti-mouse IgG antibody (anti-IgG−Alexa Fluor 647) is used. Hundreds of labeled hybridoma cells producing monoclonal antibodies (mAbs) specific for a hapten were rapidly isolated and deposited from a fusion mixture as single-cell clones via FACS. Enzyme-linked immunosorbent assay (ELISA) measurements of the supernatants of the sorted hybridoma clones revealed that all hapten-specific hybridoma clones secrete antibodies against the target. There are significant improvements using this high-throughput technique for the generation of mAbs including increased yield of antibody-producing hybridoma clones, ensured monoclonality of sorted cells, and reduced development times.
The impact of phosphorus-containing flame retardants (FR) on rigid polyisocyanurate (PIR) foams is studied by systematic variation of the chemical structure of the FR, including non-NCO-reactive and NCO-reactive dibenzo[d,f][1,3,2]dioxaphosphepine 6-oxide (BPPO)- and 9,10 dihydro-9-oxa-10 phosphaphenanthrene-10-oxide (DOPO)-containing compounds, among them a number of compounds not reported so far. These PIR foams are compared with PIR foams without FR and with standard FRs with respect to foam properties, thermal decomposition, and fire behavior. Although BPPO and DOPO differ by just one oxygen atom, the impact on the FR properties is very significant: when the FR is a filler or a dangling (dead) end in the PIR polymer network, DOPO is more effective than BPPO. When the FR is a subunit of a diol and it is fully incorporated in the PIR network, BPPO delivers superior results.
Polymers that help tailoring rheological properties during the casting process have become inevitable constituents for all kinds of high-performance concrete technologies. Due to lacking industries, these typically crude-oil based admixtures are not readily available in many parts of the world, which limits the implementation of more sustainable high-performance construction technologies in these regions. Alternative polymers, which often demand for less processing, can be derived from local plant-based resources. The paper provides experimental data of flow tests of cement pastes with polysaccharides from Triumfetta pendrata A. Rich, acacia gum and cassava without and in the presence of polycarboxylate ether superplasticizer. The flow tests are amended by observations of the zeta potentials and the hydrodynamic diameters in the presence of and without calcium ions in the dispersion medium. The results show that in the presence of and without calcium ions all polysaccharides provide negative zeta potentials, yet, they affect flowability and thixotropy in different ways. Cassava starch, acacia gum, and the gum of Triumfetta pendrata A. Rich qualified well for robustness improvement, strong stiffening, and additive manufacturing, respectively. The reason for the different effects can be found in their average sizes and size distribution. Due to the promising results, a flow chart for local value chains is derived on the example of yet unused cassava wastes, which can be converted in parallel.