Synthesis, Characterizations and Application of Bisphenol-A Based Highly Branched Polyol in Polyurethanes Coatings

Amardip M. Patil

Department of Polymer Chemistry, School of Chemical Sciences, North Maharashtra University, Jalgaon, 425001 (MS), India

*Corresponding Author E-mail: patilamardip007@rediffmail.com

ABSTRACT:

In present work, bisphenol-A based polyol was synthesized by melt condensation polymerization with 2, 2-Bis (hydroxymethyl) propionic acid. FTIR, NMR were used for structural characterization of polyol. Also TGA and DSC were used for the thermal properties determinations. The polyurethanes were obtained using reactions between polyol and isophoronediisocynate in various OH: NCO molar ratios which were applied on mild steel panels and glass plates coating purpose. The coating properties of polyurethanes were determined by gloss, cross cut adhesion, corrosion by emersion test in HCl, NaCl, NaOH and Water.

KEYWORDS:Highly branched polyol, polyurethane, gloss, cross cut adhesion, corrosion.

INTRODUCTION:

Due to the three-dimensional polymeric architectures, unique physical and chemical properties the hyperbranched polymers are attracting the polymer scientist over last two decades [1-3]. The hyperbranched polymers are offering high functional groups as compared to the linear polymer, so they have many applications in various fields like adhesives, coating applications, drug delivery and gene therapy. Also, some physical characters, high solubility and unique rheological behavior are offering the vital role in applications [4-6]. The dendritic polymers are divided into two different classes: the monodisperse dendrimers and the polydispersity hyperbranched polymers. Dendritic polymers are offering high functional groups as well as variety of functional groups. Also they provide high solubility and distinctive rheological behavior due to these dendrimers are industrially important [1, 7-10].

HBPs with hydroxyl terminal groups have potential application in polyurethane coatings design. Generally polycondensation reaction of 2, 2-bis (hydroxymethyl) propionic acid (bis-MPA) with a core molecule having multiple hydroxyl groups (core+AB₂) are used for dendrimers synthesis. To attain some additional properties to the polyurethane coatings, we need to modify the structure of the polymer or need to add some cross-linking agents or chain extenders to the NCO-terminated polyurethane with a hydroxyl or amine-terminated molecules. In the structure of the polymer, we can adopt certain functionalities either in a core or repeating unit of the HBPs.

Materials:

Bisphenol-A (BPA) and para-toluene sulphonic acid (pTSA) were purchased from s.d. fine chemical India. While 2, 2-Bis (hydroxymethyl) propionic acid and isophoronediisocynate (IPDI) were purchased from Sigma-Aldrich. All the chemicals used without further purification.

Synthesis of Bisphenol A based hyperbranched polymer:

Weigh accurately both the reactant, i.e., bisphenol-A and bis-MPA in 1:6 mole ratio taken in a three-necked round bottomed flask equipped with a mechanical stirrer, thermometer and nitrogen inlet. 0.04 % weight of bis-MPA, PTSA was used as a catalyst. All these mixtures were taken in a three-necked round bottomed flask containing tetrahydrofuran as a solvent. This mixture was put at the temperature to 180to 200⁰C slowly and refluxes the mixture for 4 to 5 hr. The reaction was stopped when the acid value was found to be below 10. The product was waxy dark and brown in color.

Preparation of MS panels:

Clean the mild steel panels from adhering dust and oil material using sand paper. Again, wrap with acetone for removal of the metal particle after sanding from the surface. Thus, reaction mixture applied on the panels using a brush.

Synthesis of Bisphenol –A based hyperbranched polyurethanes (PU):

The preparation of PU was carried out by mixing of proper mole ratio (OH: NCO, 1: 1.2, 0.5:0.5, and 0.1:0.9 mole) of Bisphenol-A based hyperbranched polymer with IPDI to prepared PU. The Bisphenol A based hyperbranched polymer dissolved in THF with IPDI and mixed it well. The reaction mixtures applied on the mild steel panels using brush. Allow the coatings were cured at room temperature for 24 hrs. The panels were kept at 70⁰C in oven for post curing for 45 minutes.

Characterization: -

Determination of acid value and the hydroxyl value of Synthesis of Bisphenol-A Based Hyperbranched:

Acid value (ASTM D 974) is defined as the milligrams of KOH required neutralizing the amount of acid group present in one gram of polymer. The unit of acid number is mg of KOH/g of the polymer. The following formula used for the determination of acid value. The acid value of the polyol resin was 8.791 mg of KOH / g. of sample

Acid Value=(56.1×ml of KOH consumed×exact normality of KOH solution)/ (Weight of sample in gram)

The hydroxyl value (D 4274) of a substance is the amount of in milligrams of potassium hydroxide required to neutralize any acid when combined by acylation in 1 g of the sample under examination. The unit of acid number is mg of KOH/g of the polymer. Hydroxyl value determined by using the following formula

Hydroxyl number=(56.1×ml of KOH consumed(B-A)×exact normality of KOH solution)/(Weight of samle in gram)

Structural characterizations of highly branched polyol by FTIR and NMR:

The FTIR and NMR are significant tools for the structural determination of organic compounds as well as polymers. The FTIR spectra of the hyperbranched polymer were scanned (Perkin-Elmer 2000 FTIR spectrometer) in the range of 4000−500 cm−1 by using KBr pellets.1HNMR measurements were performed (Varian Mercury 300 MHz spectrometer) using TMS as an internal standard in d₆-DMSO.

Characterizations of properties of PU-coating

Gloss:

Coated panels were for the gloss measurement at angle 60⁰and 90⁰on the digital gloss meter (Raj Scientific Company, India) Prior to analysis digital gloss meter was calibrated using the standard provided by the manufacturer. Gloss is the ratio of incident light to reflected light. Gloss is the measurement of reflected light at a different angle which depends on the thickness of coatings.

Cross cut adhesion Test:

Adhesion test was carried out as per ASTM D-3359-02 standard, in this test cross cut adhesion tester consisting of die with a number of close setup parallel blades 11 teeth were functionalized under pressure on the coated panels in two directions at the right angle to each other to achieve a pattern of a square. A strip of self-adhesive tape stuck over the mild steel panels and removed sharply. Adhesion of the film assessed by accounting the number of square peeled with adhesive tape.

Chemical and Corrosion test:

The corrosion test of PU coating against acid, water and salt presented in the table. The corrosion resistance of PU coating before A) and after B) testing in NaCl (3.5%), NaOH (5%), HCl solution (5%), and water are shown in the figure. All PU coating sample panels viz. uncoated panels (blank) were dipped into the all above solutions and examined for corrosion.

Examination showed that the prepared PU coating has superior anticorrosive performance only in NaOH solution than uncoated (blank) panels.

Pencil Hardness Test:

The set of Elcometer 3366 Hardness Testing Pencil is a simple but efficient technique to evaluate the hardness of many coatings.

Coating Properties: -

The coating properties tested for prepared PU sample include gloss, cross cut adhesion and corrosion resistance are as shown below:

Table 1 Gloss of Bisphenol-A based hyperbranched PU Coating

Sr. No.	PU –Coating OH: NCO in mole	Gloss at 60⁰	Gloss at 90⁰	Cross cut adhesion	Hardness
1.	1:1.2	98.7	111.5	5B	4H
2.	0.1:0.9	64.4	106.7	5B	4H
3.	0.5:0.5	78.9	89.9	2B	2H

Table 2 Corrosion study of Bisphenol-A based hyperbranched PU-Coating

Ratio (mole OH: NCO)	HCl	NaCl	NaOH	Water
Without Coating
1:1.2
0.5:0.5
0.1:0.9

3) Study of FTIR Spectrum: -

Figure 3 FTIR spectrum of Bisphenol-A based hyperbranched polymer

Bisphenol A based Hyperbranched polymer characterized by Infrared spectroscopic technique and the spectrum is given in figure 1. The spectrum showed absorption band at 3350cm-1 for O-H stretching’s and 2962cm-1 for C-H stretching and 2343cm-1shows C=N stretching’s and 2075cm-1 shows that –C=C- .Absorption band at1726cm-1 shows C=O carbonyl stretching frequency for alfa and beta unsaturated ester.

FTIR spectrum of PU

Figure 4 FTIR spectrum of PU coating

PU coating on the glass plate characterized by Infrared spectroscopic technique and the spectrum is given in figure 2. The spectrum showed absorption band at 3471 cm^-1 shows O-H terminal hydroxyl group. The band at 3036 cm^-1 shows aromatic C-H stretching. The strong absorption band at 2565 cm^-1shows acidic O-H stretching. The carbamide (urethane) bands were found at 1718 cm^-1. The band at1548cm-1 shows C=C stretching vibration of unsaturated region. FTIR band for OH bending was found at 1338 cm^-1 while C-O stretching attributed to1041-1257 cm^-1. Hydroxyl and ester carbonyl peaks in FTIR of prepared BPA based hyperbranched polymer were present.

Study of H1 NMR for Hyperbranched polymer

Figure 5 NMR spectra of Hyperbranched polyol

H1 NMR spectrum of Bisphenol Abased hyperbranched polymer showed as in fig. distinguish the signals of chemical shift at 2.05-2.32 were assigned to CH₃-C=O while the signal of chemical shift at 3.91 - 3.79 corresponding to CH₃-O and another signal at 5.04 ascribed to OH and those at 7.21, 7.25, 7.26. Were assigned to Ar–H that is Aromatic hydrogen is on phenyl ring and 7.27 were assigned to d₆-DMSO solvent.

Study TGA Study of Bisphenol-A Based Hyperbranched polymer

Figure 6 TGA of Bisphenol-A based hyperbranched polyol

Thermal stability of Bisphenol A based hyperbranched polymer studied by thermal gravimetric analysis. Here TGA of hyperbranched polymer stable up to 150⁰C. The hyperbranched polymer was observed two step degradations. The first step degradation occurred by the breakdown of urethane moiety and weight loss was occurred by 53% in the temperature range of 150-300⁰C. The second step degradation occurred in temp between 350-800⁰C and 47% weight loss occurred by breakdown of ether moiety.

CONCLUSION:

The Bisphenol A based Hyperbranched polymer were prepared by Bisphenol A and 2, 2-Bis (hydroxymethyl) propionic acid by melt condensation polymerization and characterized by the spectroscopic technique. Further, all prepared Hyperbranched polymer was used as polyol in preparation of PU coatings. The performance of Bisphenol A based Hyperbranched polymer coatings were tested by evaluating their coatings properties. The PU coatings Prepared from Bisphenol A and dimethylpropionic acid exhibited better anticorrosive performance. From above experimental, we can conclude that Bisphenol based polymer has strong potential for its used in the formation of hyperbranched polymer and it can be used for utilization in the formulation of PU coatings.

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Received on 25.11.2017 Modified on 23.12.2017

Asian J. Research Chem. 2018; 11(3):593-598.

DOI:10.5958/0974-4150.2018.00106.2