Thermal Stability of Some New Metal Containing Polymers Based on Resol-Bisphenol A Formaldehyde Resin

Huda S. Khaudeyer*, Zaki N. Kadhim and Widad S. Hanoosh

Department of Chemistry, College of Science, University of Basrah, Iraq

*Corresponding Author E-mail: bluewave.hs@gmail.com

Abstract:

Polymers containing vanadium, molybdenum, nickel, copper and zinc ions have been synthesized by reaction of resol- bisphenol A formaldehyde resin (RBF) with the schiff base complexes of these metal ions. The incorporation of metal ions, especially the molybdenum ion, into the polymer matrices produced polymers with good thermal stability. The resulting metal containing polymers showed higher thermal stability. The thermal analysis of the obtained polymers were evaluated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC).

KEY WORDS: bisphenol-A, formaldehyde, metal containing polymers, thermal stability, schiff base

Introduction:

Metal containing polymers have been gaining more attention because of their potential important applications^(1,2). The incorporation of metals can be modify the essential bulk properties of these polymer such as thermal stability, dielectric, conductivity and other physicochemical characteristics. In general, the thermal stability of metal-containing polymer systems is relatively enhanced compared to that of the bulk polymer⁽³⁾. Moreover, the coordinating ability of the metal within the polymer backbone permits these materials to act as sensors, and as building blocks for supramolecular structures⁽⁴⁾. Also, the metal moiety can be incorporated into the polymer back-bone by either covalently bonding directly to the main chain or coordinating to ligands within the backbone. The metal moiety could also be pendant or attached to the side chain of the polymer^(5,6).

Two approaches are generally used for the attachment of metal complexes with polymers. The first approach involves the introduction of the bifunctional metal complexes as a monomer, followed by their polymerization⁽⁷⁾. The second approach involves the linking of metal complexes directly onto preformed functional polymers⁽⁸⁾. Some metal complexes commonly used in the synthesis of metal containing polymers are Schiff base, ferrocene, imidazole, secondary and tertiary amine metal complexes, and so forth^(9-12). Among these metal complexes Schiff base metal complexes have been widely used due to their corrosive resistant, microbial as well as thermal resistant properties^(13-15). In this work, Schiff base metal complexes were reacted with RBF in 1:3 molar ratios to produced metal containing polymers. The hydroxyl functional groups in the metal complexes are expected to undergo a reaction with RBF to yield thermally stable polymers and thermal behavior of the obtained polymers have been investigated.

EXPERIMENTAL:

Materials:

All chemicals were obtained from Merck, BDH, RDH, Aldrich, Fluka, H&W, Thomas and Tedia, and were provided in pure grade.

Analytical Methods:

The FTIR spectra were recorded on a FTIR-8400S spectrophotometer in 4000-400 cm⁻¹ region by using KBr discs. Elemental analyses were carried out using a Perkine-Elmer 2400 Series II CHN analyser. The thermal properties of the cured metal containing polymers were investigated with Perkin-Elmer differential scanning calorimeters (DSC-7), and thermogravimetric analysis (TGA-7 and TGA-Q50) Perkin-Elmer at a heating rate of 5 ̊C min^-1 and 10 ̊C min^-1 respectively under a nitrogen atmosphere.

Synthesis:

Synthesis of Resol- Bisphenol A Formaldehyde Resin (RBF):

The resin was syntheses by condensation reaction between BPA and formaldehyde with sodium hydroxide as catalyst⁽¹⁶⁾ (scheme 1).

Scheme 1: Synthesis of RBF

Synthesis of Schiff Base Complexes (ML):

The Schiff bases were synthesis by condensation of salicylaldehyde with 2-amino-2-methyl-1,3-propane-diol and 2-amino-2-(hydroxymethyl)-1,3-propanediol in 1:3 molar ratios, respectively^(17,18) (scheme 2-3). Then these ligands were reacted with transition metal ions: V(V), Mo(VI), Ni, Cu and Zn(II)^(19-24)

Scheme 2: Synthesis of L₁

Scheme 3: Synthesis of L₂

Synthesis of Metal-Containing Polymers (RBF-ML): All polymer-metal complexes were blended by mixing (0.75 g) resol of bisphenol-A (RBF) and (0.25 g) of the Schiff base complexes (ML) at room temperature, according to scheme 4. Then placed in an oven at (120 ̊C) for 3 hours to complete the process of hardening and subsequent hardening process at (150 ̊C) for 2 hours and at (180 ̊C) for 2 hours for post curing.

Scheme 3: Synthesis of RBF-ML (ML=V(V)L₁, V(V)L₂, Mo(VI)L₁, Mo(VI)L₂, Ni(II)L₁, Ni(II)L₂, Cu(II)L₁, Cu(II)L₂, Zn(II)L₁, Zn(II)L₂)

RESULTS AND DISCUSSION:

RBF resin was obtained via the reaction of BPA with formaldehyde in a basic medium leads to formation of the resol-type resin. The FTIR spectra of RBF exhibited absorption band of group OH at 3409 cm^-1, CH ₃ at 1369 and 1288 cm^-1, CH aromatic at 2931 cm^-1, 900 and 850 cm^-1 due to three- or tetra- substituted aromatics.

The Schiff base 1,3-dihydroxy-2-methyl-(salicylideneamino) propane (L₁) and 1,3-dihydroxy-2-hydroxymethyl-(salicylideneamino) propane (L₂) were synthesized by condensation of carbonyl compounds with primary amine and these ligands reacted with transition metal ions. The FTIR spectra and CHN analysis data are summarized in Table 1 and. Table 2.

Table 1: FTIR data of Schiff base and its complexes (cm^-1)

ν(M=O)	ν(M−N)	ν(M−O)	ν(C-O)	ν (C=N)	ν(O-H)	Compounds
-	-	-	1278	1629	3328	L1
-	-	-	1307	1639	3300	L2
956	462	563	1299	1623	3400	V(V)L1
958	466	576	1296	1627	3375	V(V)L2
929,891	453	572	1296	1620	3321	Mo(VI)L1
929,896	457	576	1292	1622	3311	Mo(VI)L2
-	457	582	1284	1637	3396	Ni(II)L1
-	447	584	1321	1629	3319	Ni(II)L2
-	474	591	1305	1634	3294	Cu(II)L1
-	460	549	1307	1625	3323	Cu(II)L2
-	455	584	1286	1637	3311	Zn(II)L1
-	453	578	1288	1631	3294	Zn(II)L2

Table 2: Elemental analysis data of Schiff base and its complexes

Elemental analysis data calculated (found) (%)			Formula	Compound
N	H	C
(6.56)6.22	(7.19 7.61	(61.74)61.32	C11.5H17NO3.5	L1
(5.97) 6.22	(6.55) 6.71	(58.53) 58.66	C11H15NO4	L2
(4.87) 5.11	4.19)) 4.78	48.19 (47.77)	C20H26N2O8V2	V(V)L1
)4.59) 4.56	(4.11 (4.59	)42.7743.01 (	C11H14NO6V	V(V)L2
(3.84 (3.97	(3.97 (4.28	(37.16)37.41	C11H15NO6Mo	Mo(VI)L1
(3.61 (3.79	(3.63 (4.10	35.28 (35.78	C11H15NO7Mo	Mo(VI)L2
(4.08 (4.23	(5.19 (6.09	(45.04 (45.36	C28H46N2O14Ni2	Ni(II)L1
(3.75 (3.93	(5.27 (5.95	(42.00) 42.17	C27H42N2O15Ni2	Ni(II)L2
(4.56 (4.85	(4.71 (5.24	(46.23 (45.75	C44H60N4O16Cu4	Cu(II)L1
(4.03 (4.60	(4.62 (4.96	)43.05 (43.35	C44H60N4O20Cu4	Cu(II)L2
(4.08 (3.57	(4.73 (5.39	)46.54 (45.88	C15H21NO7Zn	Zn(II)L1
(3.75 (3.82	(4.88 (5.22	(42.03) 42.58	C15H21NO8Zn	Zn(II)L2

Polymer-metal complexes have been prepared by blending ML with RBF, the functional groups which undergo a reaction are the hydroxyl groups in ML and the methylol groups in RBF, they were mix well until the homogeneity of the mixture and the process of hardening at (120 ̊C) for (15-30 min) to ensure interaction of methylol groups in phenolic resins with hydroxyl groups in the metal complexes, that leads to the formation of ether linkage (-COC), then the temperature was raised to (150 ̊C) for two hours and the loss of formalin molecules (CH₂O) were occurred the ether groups were converted to methylene linkage (-CH2-). The subsequent hardening process occurred at (180 C) for 2 hours to ensure that the polymer network were frowned completely. The metal-containing polymers were characterized by FTIR spectroscopy, All Polymers had similar FTIR spectra (Table 3).. The important characteristic absorption bands are as follows: the high intense band due to phenolic-OH appeared in the region at (3413-3309) cm⁻¹ and azomethine ν(C=N) at (1637-1620) cm⁻¹.The ν(M–O) and ν(M–N) bands have been assigned in the region (559-524) cm⁻¹ and (474-433) cm⁻¹, respectively.

Table 3: FTIR data of metal-containing polymers (RBF-ML) (cm^-1)

ν(M=O)	ν(M−N)	ν(M−O)	ν(C-O)	ν(C=N)	ν(O-H)	Resins
952	462	559	1087	1627	3413	RBF-V(V)L1
956	474	543	1049	1608	3371	RBF-V(V)L2
929,889	455	559	1060	1647	3409	RBF-Mo(VI)L1
931,887	459	555	1049	1650	3409	RBF-Mo(VI)L2
-	457	543	1051	1639	3379	RBF-Ni(II)L1
-	470	524	1049	1620	3382	RBF-Ni(II)L2
-	451	536	1053	1623	3379	RBF-Cu(II)L1
-	459	543	1053	1620	3382	RBF-Cu(II)L2
-	433	551	1054	1612	3371	RBF-Zn(II)L1
-	455	551	1053	1620	3386	RBF-Zn(II)L2

Thermal Analysis

The thermal properties of cured the metal-containing polymers have been carried on by DSC and TGA techniques. The DSC theromgrams of cured polymer containing vanadium, molybdenum, nickel, copper and zine ions are shown in Figures (1-11) and the Tg values

Table 4: Tg of metal-containing polymer

C^0 ((Tg	Resins
46.59	RBF-V(V)L1
81.46	RBF-V(V)L2
81.42	RBF-Mo(VI)L1
-	RBF-Mo(VI)L2
55.76	RBF-Ni(II)L1
59.46	RBF-Ni(II)L2
-	RBF-Cu(II)L1
67.39	RBF-Cu(II)L2
82.50	RBF-Zn(II)L1
82.31	RBF-Zn(II)L2

Tg (C⁰)- glass transition temperature

of are higher for the complexes V(V)L₂, Mo(VI)L₁, Cu(II)L₂, Zn(II)L_1, Zn(II)L₂.It was noted a difference in the Tg values of polymer to another depending on the density of cross linking and the presence of aromatic structures in the repeating unit and the polymer chain length. The exothermic peck at higher than 200 C⁰ was attributed to the dissociation of these polymers.

Fig. 1. DSC thermogramsof RBF

Fig. 2. DSC thermograms of RBF-V(V)L₁

Fig. 3. DSC thermograms of RBF-V(V)L₂

Fig. 4. DSC thermograms of RBF-Mo(VI)L₁

F Fig. 5. DSC thermograms of RBF-Mo(VI)L₂

Fig. 6. DSC thermograms of RBF-Ni(II)L₁

Fig. 7. DSC thermograms of RBF-Ni(II)L2

Fig. 8. DSC thermograms of RBF-Cu(II)L₁

Fig. 9. DSC thermograms of RBF-Cu(II)L₂

Fig. 10. DSC thermograms of RBF-Zn(II)L₁

Fig. 11. DSC thermograms of RBF-Zn(II)L₂

The thermal stability of cured resol- bisphenol A formaldehyde containing metals ions were investigated by TGA and DTG thermograms (Figs. 12-22) and Table 5. For these polymers shows more than one thermal decomposition temperature. The enhancement of the thermal stability due to incorporation of metal ions into RBF. The thermograms of the cured resol- bisphenol A formaldehyde containing metal ions clearly indicate that the thermal stability of cured resins were improved with the incorporation of metal ions into the RBF resin. The results of thermogravimetric analysis were revealed that

Table 5: TGA / DTG thermograms data

Char (%) at 700^oC	∆E (KJ/ mol)	Ts(^oC)	T50% (^oC)	DT (^oC)			Resin
				Top3	Top2	Top1
45.76	43.21	-	561	-	408	267	RBF
55.18	52.31	471	700 <	-	408	267	RBF-V(V)L1
52.98	62.74	446	700 <	-	446	272	RBF-V(V)L2
59.14	83.27	471	700 <	500	417	252	RBF-Mo(VI)L1
58.76	79.32	457	700 <	480	429	257	RBF-Mo(VI)L2
54.53	70.11	417	700 <	-	383	274	RBF-Ni(II)L1
52.58	63.63	410	700 <	-	392	249	RBF-Ni(II)L2
51.35	52.81	391	700 <	380	291	257	RBF-Cu(II)L1
48.69	51.05	400	700 <	-	386	263	RBF-Cu(II)L2
55.45	71.03	398	700 <	-	386	-	RBF-Zn(II)L1
54.78	69.72	402	700 <	-	386	257	RBF-Zn(II)L2

DT: decomposition temperature; Top: optimum decomposition temperature; T_50%: Half Weight Loss Temperature (temperature for 50 % weight loss); Ts: half volatilization temperature; ∆E: activation energy of decomposition

the RBF–Mo(VI)L₁are thermally more stable. The order of stability on the basis of thermal weight at 700 C can be given in thefollowing order RBF–Mo(VI)L₁> RBF–Mo(VI)L₂> RBF–Zn(II)L₁> RBF–Zn(II)L₂> RBF–Ni(II)L₁> RBF–V(V)L₂> RBF–Ni(II)L₂> RBF–V(V)L₁> RBF–Cu(II)L₁> RBF–Cu(II)L₁. All the polymers showed good thermal stability even at high temperature than the RBF due to the presence of the metal ions in the polymer networks. Activation energy for these polymers are higher in L₁ then L₂. On the other hand, it was observed that these polymers have a higher decomposition temperature, activation energy, T_50% and char % content compared with RBF. These were indicated that the chemical modification process of resolresin increasing the thermal stability. Therefore, these polymers can be used as thermal insulation.

Fig. 12. TGA thermograms of RBF

Fig. 13. TGA thermograms of RBF-V(V)L₁

Fig. 14. TGA thermograms of RBF-V(V)L₂

Fig. 15. TGA thermograms of RBF-Mo(VI)L₁

Fig. 16. TGA thermograms of RBF-Mo(VI)L₂

Fig. 17. TGA thermograms of RBF-Ni(II)L₁

Fig. 18. TGA thermograms of RBF-Ni(II)L₂

Fig. 19. TGA thermograms of RBF-Cu(II)L₁

Fig. 20. TGA thermograms of RBF-Cu(II)L₂

Fig. 21. TGA thermograms of RBF-Zn(II)L₁

Fig. 22. TGA thermograms of RBF-Zn(II)L₂

CONCLUSIONS:

Polymers containing metal complexes were prepared by blending schiff base metal complexes with RBF. Introduction of schiff base metal complexes into the polymer matrix results in good thermal stability, especially in the case of the molybdenum-containing polymer, which is comparable to the resol resin. Also, the char % content reach more than 50 % which may allow these polymers to be used in different thermal purposes like, thermal insulate.

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Received on 27.04.2015 Modified on 20.05.2015

Accepted on 25.05.2015 ©A&V Publications All right reserved

Research J. Science and Tech. 7(3):July- Sept. 2015; Page 183-190

DOI: 10.5958/2349-2988.2015.00025.X