Fully water-blown polyisocyanurate-polyurethane foams with improved mechanical properties prepared from aqueous solution of gelling/ blowing and trimerization catalysts

Abstract Fully water-blown polyisocyanurate-polyurethane (PIR-PUR) foams with improved mechanical properties have been prepared using aqueous solutions of metal-ammonia complex, Cu(Am) or Zn(Am), as gelling/blowing catalysts and potassium octoate (KOct) solution in diethylene glycol as a trimerization catalyst. Two catalyst mixtures, Cu(Am)+KOct and Zn(Am)+KOct, were obtained as homogeneous aqueous solutions. In comparison to commercial catalyst system, DMCHA+KOct (DMCHA = N,N-dimethylcyclohexylamine), Cu(Am) and Zn(Am) could be miscible with KOct solution and water easier than DMCHA. This miscibility improvement led Cu(Am)+KOct and Zn(Am)+KOct to show faster catalytic reactivity in PIR-PUR foam reactions than DMCHA+KOct. All obtained PIR-PUR foams showed self-extinguishing properties and achieved HF1 materials. However, PIR-PUR foams prepared from Cu(Am)+KOct and Zn(Am)+KOct at NCO:OH ratio of 2:1 had suitable density for industrial applications and showed higher compressive strength than that prepared from DMCHA+KOct. These foams have high potential to apply as insulations for constructions, core laminates in wall panel or storage tanks.


Introduction
Let F denote a eld and let V denote a vector space over F with nite positive pair A, A * of diagonalizable F-linear maps on V, each of which acts on an eigenb irreducible tridiagonal fashion.Such a pair is called a Leonard pair (see [13, De n A, A * is said to be self-dual whenever there exists an automorphism of the endom swaps A and A * .In this case such an automorphism is unique, and called the du The literature contains many examples of self-dual Leonard pairs.For instance ated with an irreducible module for the Terwilliger algebra of the hypercube (see [4 Leonard pair of Krawtchouk type (see [10, De nition 6.1]); (iii) the Leonard pair ass module for the Terwilliger algebra of a distance-regular graph that has a spin mod bra (see [1,Theorem], [3, Theorems 4.1, 5.5]); (iv) an appropriately normalized to (see [11, Lemma 14.8]); (v) the Leonard pair consisting of any two of a modular Le De nition 1.4]); (vi) the Leonard pair consisting of a pair of opposite generators bra, acting on an evaluation module (see [5, Proposition 9.2]).The example (i) is a examples (iii), (iv) are special cases of (v).
Let A, A * denote a Leonard pair on V. We can determine whether A, A * is sel By [13, Lemma 1.3]

Appearance of metal-ammonia complex aqueous solutions
The reaction of 30 wt% ammonia aqueous solution with copper and zinc acetate gave Cu(Am) and Zn(Am) aqueous solutions, respectively.The solutions were clear and had low viscosity as shown in Figure S1.

Supplementary material
(1).The maximum % volume change (Figure S4) and % mass change (Figure S5) for both -25°C and 70°C of RPUR/ Cu(Am)-1:1 were less than those of RPUR/Zn(Am)-1:1.These results indicated that RPUR/Cu(Am)-1:1 had better dimensional stability than RPUR/Zn(Am)-1:1.The slight shrinkage and mass decrease of the foams were observed after the testing period due to the fact that diffusion rate of air into the foams is about an order of magnitude slower than that of CO 2 out of the foams, especially at high temperature (2).

Morphology of PIR-PUR foams
The cell morphology of PIR-PUR foams catalyzed by Zn(Am)+KOct and DMCHA+KOct was compared to that of their reference RPUR foams (Figure S6).6 Catalytic mechanism of the gelling reaction accelerated by Cu(Am) and Zn(Am) Copper or zinc could act as the Lewis acid and induce more electrophilicity of NCO groups, while nitrogens of ammonia ligand could act as the Lewis base and induce more nucleophilicity of OH groups.In the case of isocyanurate formation accelerated by KOct, there has been the proposed catalytic mechanism of this commercial trimerization catalyst.Octoate anions seem to be the reactive species inducing the cyclization of NCO groups, whereas potassium cations appear not to have an important role in catalysis (3).Table S1: Description of foam appearances used in recording the reaction times.

Start time
The time that was recorded when CO2 bubbles began to emerge on the surface of liquid foam mixture.

Gelation time
The time that was recorded when liquid foam mixture became gel.

Tack-free time
The time that was recorded when the outer surface of foam dried and lost stickiness with other materials.
Expansion time The time that was recorded when rising process stopped.

Figure S2 :
Figure S2: RPUR foam appearance after 14 days of dimensional stability test.

Figure S7 :
Figure S7: Digital images of burnt RPUR and PIR-PUR foams after horizontal burning test.

Figure S8 :
Figure S8: Horowitz-Metzger plots for calculating activation energy (Ea) of thermal degradation of the foams; (a) the first and (b) the second thermal degradation stages.
each eigenspace of A, A * has dimension one.Let {θ i } d i= deno values of A. For ≤ i ≤ d let v i denote a θ i -eigenvector for A. The ordering {θ whenever A * acts on the basis {v i } d i= in an irreducible tridiagonal fashion.If the then the ordering {θ d−i } d i= is also standard, and no further ordering is standard.A * .Let {θ i } d i= denote a standard ordering of the eigenvalues of A. Then A, A * is se is a standard ordering of the eigenvalues of A * (see [7, Proposition 8.7]).