POSS-triol

According to a report presented by Fu et al. [180], the influence of POSS-triol on epoxy-amine reaction depends mostly on the magnitude of AT (Tg -Tc) used. Since Tg for epoxy cured with linear aliphatic diamine—2-methyl-1,5-pentadiamine (MPDA)—was higher than the Tg of the same epoxy cured with diamine-terminated polypropylene oxide (PPO), when cured at the same temperature, epoxy-cured MPDA showed a greater improvement in the value of Tg. Moreover, the addition of POSS-triol in tetraglycidyl diamino diphenyl methane (TGDDM) cured with MPDA also increased the rubbery plateau modulus (Fig. 6). 

On the other hand, the glassy-state modulus was retained in all epoxy systems. The Tg improvement was caused by the promotion of the diffusion-controlled epoxy-amine reaction, hence, this promotion worked better in a network with a higher AT. Moreover, the addition of a small amount of POSS-triol ensured the consistency of the thermomechanical properties of epoxy networks with a high degree of steric constraints (high functionality of epoxy monomer), as evidenced by several parallel experiments. Because the addition of such a small amount of POSS-triol did not increase the viscosity of... 

Fig. 6 Storage modulus E ) and tan 5 versus temperature for TGDDM containing 1 wt% POSS-triol cured with MPDA at 150 °C for 12 h and at 100 °C for 24 h [180]...

Starters. Nearly any compound having an active hydrogen can be used as starter (initiator) for the polymerization of PO. The common types are alcohols, amines, and thiols. Thus in Figure 2 ROH could be RNH2 or RSH. The fiinctionahty is derived from the starter, thus glycerol results in a triol. Some common starters are shown in Table 4. The term starter is preferred over the commonly used term initiator because the latter has a slightly different connotation in polymer chemistry. Table 5 Hsts some homopolymer and copolymer products from various starters. 

Place Arcol Polyol F-3022 (100 g, 0.1 eq., 56 OH, mixed PO/EO triol from Bayer) into a suitable container. To this add distilled water (3.3 g, 0.4125 eq.), Niax Silicone L-620 (0.5 g, a silicone surfactant from OSi Specialties), and Niax C-183 (0.12 g, an amine catalyst from OSi Specialties). Thoroughly blend this mixture without incorporating air bubbles. Then add Dabco T-9 (0.25 g, stannous octoate from Air Products) and mix again. The T-9 must be added last because it is quite water sensitive, so its exposure to the water-containing polyol blend should be kept to a minimum. To this polyol blend, quickly add Mondur TD-80 (42.6 g, 0.4868 eq., a mixture of 80% 2,4-TDI and 20% 2,6-TDI isomers from Bayer) and immediately stir at 3000 rpm for 5 s. Quickly pour the reaction mixture into a suitable container such as a 1-qt paper or plastic cup and allow the foam to free-rise. The stir blade may be wiped or brushed clean. 

The product is called l,l,l—Trimethylolpropane (TMP) and is used mainly in the manufacture of triols by adduction with propylene oxide (PO), for flexible polyurethane foams and of synthetic lubricants by esterification with fatty acids. The allyl ethers of trimethylolpropane are used as crosslinking agents, for example, in acrylic resin systems. The world-wide capacity for TMP production is in an increasing trend. 

By using two oxiranic monomers, such as PO and EO, it is possible to obtain a great variety of polyether polyols homopolymers of PO, block copolymers PO-EO (with terminal or internal poly[EO] block) or random copolymers (heteropolyethers) of PO-EO, diols or triols of different MW. 

The polyether triols are the most important class of polyether polyols and they are used in flexible PU foam fabrication. The majority of polyether triols used in flexible foams are copolymers of PO-EO. Random copolymers are used in continuous slabstock flexible foams and block copolymers (PO-EO), with terminal poly[EO] block, are used in moulded foams (hot moulding and cold cure moulding processes). 

The high MW polyether triols, copolymers of PO-EO are the most important oligo-polyols for PU, having the biggest volume of industrial production. This is the reason why the synthesis of polyether triols, by polymerisation of PO and/or EO and initiated by glycerol, will be presented in detail. 

Synthesis of Polyether Triols Based on Glycerol Homopolymers of PO... 

The PO homopolymers (MW of 3000) initiated by glycerol are some of the most popular polyols for flexible PO slabstock. This structure is one of the oldest structures of a polyether used for flexible PU foams. In essence these polyether triols are obtained by the anionic polymerisation of PO initiated by glycerol and catalysed by KOH. 

We can conclude that the polyether triols obtained by anionic polymerisation of PO initiated by glycerol consist of four polymeric species ... 

The polyethers obtained by the anionic polymerisation of PO initiated by glycerol are not trifunctional, having a lower functionality than 3, but usually in the range 2 < f < 3. The diols and monols decrease the functionality. The functionality is lower for high MW polyethers and for the polyethers obtained at higher polymerisation temperatures. In Figure 4.6, one observes the strong polyether triol functionality decrease as the polyether MW increases. 

Figure 4.6 The real functionality of polyether triols, PO homopolymers, as function of...

Thus, in Figure 4.12 the thin layer chromatograms of PO homopolymers, triols and diols are presented. One observes that the polyether diols are mixtures of polyether diols and monols and the polyether triols are mixtures of polyether triols, diols and monols. The polyether monol was obtained by propoxylation of the allyl alcohol. 

Figure 4.13 Optical density measurements of a thin layer chromatogram of polyether triol, PO homopolymer, of MW of 3000 daltons...

Polyether diols are obtained in the same way as polyether triols, with the difference that the starter is propylene glycol or DPG instead of glycerol or TMP. Because potassium hydroxide and water lead, by the reaction with PO, to polyether diols, it is not necessary to anhydrisate the initial mixture of starter - KOH (solid or aqueous solution). The polyether diols, homopolymers of PO, are obtained by direct propoxylation of a propylene glycol or DPG mixture with KOH (solid or aqueous KOH 40-50% solution). 

The most important characteristics of industrially produced polyether diols and triols homopolymers of propylene oxide are presented in Tables 4.4 and 4.5. All the polyether PO homopolymers, diols or triols have mostly secondary hydroxyls as terminal groups (94-96 % secondary hydroxyls) (see Figure 4.14). 

The random copolyether triols PO-EO, usually called heteropolyether polyols, with a MW of 3000-3600 daltons, are the most important polyether polyols for flexible PU slabstock foams, generally used in furniture industry. The worldwide consumption of flexible PU foams is presented in Figure 4.16. 

For continuous flexible PU slabstock production, the heteropolyether triols PO-EO are considered universal polyols used in conventional soft and supersoft flexible PU foams, covering a large range of densities (12-40 kg/m3) and load bearing properties. 

The polyether most used in practice for continuous free rise slabstock flexible PU foams are the triols, copolyethers PO-EO, containing around 10-15% EO randomly distributed (most used 10-12% EO), of MW in the range of 3000-3600 daltons (OH = 42-60 mg KOH/g). 

The general structure of random copolymers of PO-EO and copolyether triols (PO-EO) is presented in Figure 4.18. The main characteristics of the random copolymers of PO-EO, heteropolyether triols, which are used most, are presented in Table 4.7. 

Figure 4.18 The general structure of random copolymers of PO-EO (heteropolyether triols)...

Table 4.7 The main characteristics of polyether triol random copolymers (PO-EO heteropolyether polyols) ...

Figure 4.19 Polyether triols, EO-PO random copolymers, with high EO content...

This polyether triol hybrid structure block [PO] - random [PO - EO]- block EO, with a MW of 3000 daltons, was used successfully for hot moulded flexible PU foams with... 

Figure 4.20 Polyether triol type block [PO] - random [PO-EO]...

The pseudoliving character of PO anionic polymerisation produces a large variety of block copolymers, by simply changing the nature of the oxirane monomer because the catalytic species (potassium alcoholate) remains active during and after the polymerisation reaction. Thus, if a polyether is synthesised first by anionic polymerisation of PO and the polymerisation continues with another monomer, such as EO, a block copolyether PO-EO with a terminal poly[EO] block is obtained. Another synthetic variant is to obtain a polyethoxylated polyether first by the anionic polymerisation of EO initiated by glycerol [108], followed by the addition of PO to the resulting polyethoxylated triol. A block copolyether PO-EO is obtained with internal poly[EO] block linked to the starter. Another possibility is to add the monomers in three steps first PO is added to glycerol, followed by EO addition and finally by the addition of PO. A copolyether triol block copolymer PO-EO with the internal poly[EO] block situated inside the polyetheric chain between two poly[PO] blocks is obtained [4, 100, 101]. 

The synthesis of polyether triols, block copolymers with terminal poly[EO] block is relatively simple in the first step a propoxylated intermediate polyether is synthesised by the polyaddition of PO to the starter (glycerol or propylene glycol). After the addition of the required quantity of PO, the unreacted monomer is eliminated by vacuum distillation and the polymerisation continues by the addition of EO, the second monomer. 

Polyether triol, block copolymer PO-EO, with terminal poly[EO] block... 

Figure 4.23 Variation of primary hydroxyl content as a function of EO content in polyether triols block copolymers [PO-EO] with terminal poly[EO] block MW = 5000 daltons catalyst KOH - 0.0056 mol%...

Figure 4.24 Graphical representation of Equation 4.17 in the form of a straight line, at polyether triols of MW of 5000 daltons, block copolymers PO-EO with terminal poly[EO] block Distribution constant K = 14...

The polyether diols, block copolymers of PO-EO with terminal poly[EO] block are obtained absolutely identically to the previously described EO capped polyether triols, the difference being that the propoxylated intermediate is a propoxylated polyether diol. 

Figure 4.28 The structures of polyether triol block copolymers PO-EO a) terminal poly[EO)] block b) poly[EO] block linked to the starter c) internal poly[EO] block...

The most important polyether triol, PO-EO block copolymers with poly[EO] block, used in practice, are ... 

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