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The primary objectives of this experiment were:
Polymers are integral to various aspects of daily life due to their versatile properties and applications. Synthetic rubbers, a type of polymer, find extensive use in products such as tires, protective gloves, adhesives, and paints. Synthetic rubber can be produced through emulsion polymerization, a technique first patented in 1929 by R.
P. Dinsmore while working for The Goodyear Tire & Rubber Company.
Emulsion polymerization, initially developed to address the limited availability of natural rubber during World War II, has led to the synthesis of various copolymers with distinct properties. In this experiment, we focus on styrene-butyl acrylate (SBA) copolymer latex preparation via a batch process. The resulting emulsions were characterized for pH value, solubility in organic solvents, and film properties using spectroscopic techniques (FT-IR and 1H NMR) and Differential Scanning Calorimetry (DSC).
All starting materials were meticulously prepared for use:
The following steps were taken for pre-emulsion preparation:
The batch emulsion polymerization was carried out as follows:
| Component | Set I (g) | Set II (g) |
|---|---|---|
| Butyl Acrylate (BA) | 58.0 | 28.0 |
| Styrene (St) | 40.0 | 70.0 |
| Acrylic Acid (AA) | 2.0 | 2.0 |
| Water | 150.0 | 150.0 |
| Potassium Persulphate (KPS) | 1.0050 | 1.0966 |
| Sodium Lauryl Sulphate (SLS) | 4.0048 | 4.0048 |
The emulsions were characterized by the following methods:
The films casted from copolymer emulsions were characterized as follows:
The characteristic properties of the synthesized copolymers are presented in Table (2). Both emulsions were found to be acidic with Set II displaying higher viscosity and solid content (44.2%) compared to Set I. This difference can be attributed to the molecular weight and crystallite size variations caused by the differing styrene content in the compositions.
| Sample ID | Set I | Set II |
|---|---|---|
| pH | 3.00 | 4.00 |
| Solid Content, wt.% | 27.23 | 44.20 |
Both latex films were milky white, but Set I was ductile while Set II was brittle. The differences in mechanical properties can be attributed to variations in molecular weight and styrene content, with Set II displaying higher hardness due to its increased styrene content.
| Solvent | Set I Solubility | Set II Solubility | Solvent | Set I Solubility | Set II Solubility |
|---|---|---|---|---|---|
| Water | No | No | Toluene | Yes | Yes |
| Chloroform | Yes | Yes | 1,4-butanediol | No | No |
| THF | Yes | Yes | 2M HCl | No | No |
| Methanol | No | No | Acetic Acid | No | No |
| Cyclohexanone | No | No | Hexane | No | No |
Distinctive IR absorption bands for the copolymer samples are tabulated below:
| Wavenumber, γ (±4 cm-1) | Remarks | Set I | Set II |
|---|---|---|---|
| 760.31 & 698.86 (s) | Out-of-plane, C-H (aromatic) | 760.11 & 698.17 (s) | |
| 1727.57 (s) | Carbonyl, C=O stretch | 1732.51 (s) | |
| 1158.34 (s) | C-O stretch | 1165.21 (s) | |
| 2957.50 (m) | sp3 C-H stretch | 2956.43 (m) |
The 1H NMR spectra of P(BuA/St) copolymer samples were analyzed to determine their composition:
Notably, in the case of poly(butyl acrylate) (PBA), the (-OCH2) proton appeared around δ 4.0 ppm. For polystyrene, the aromatic protons showed splitting into two broad bands. The P(Bu/St) copolymer spectrum displayed (-OCH2) peak splitting, indicating variations in BuA content.
The copolymer composition was calculated from the relative intensities of phenyl (S1) and –OCH2 (S2) proton resonances, as described in Table (5).
| Sample ID | fBA | fSt | FBA | FSt |
|---|---|---|---|---|
| Set I | 0.54 | 0.46 | 0.47 | 0.53 |
| Set II | 0.25 | 0.75 | 0.30 | 0.70 |
In this experiment, we successfully prepared and characterized styrene-butyl acrylate (SBA) copolymer emulsions with varying compositions. These emulsions exhibited distinct properties, including differences in pH, solid content, and mechanical characteristics. The analysis of solubility in various solvents provided valuable insights into the materials' suitability for specific applications.
Furthermore, spectroscopic techniques, such as FT-IR and 1H NMR, were employed to elucidate the molecular structure and composition of the copolymers. The results demonstrated how variations in monomer composition affected the polymer's properties.
This study contributes to our understanding of emulsion polymerization processes and the ability to tailor polymer properties for specific applications in industries such as coatings, adhesives, and materials science.
Future research could explore the optimization of copolymer compositions to achieve specific desired properties, such as enhanced mechanical strength or improved solubility in particular solvents. Additionally, investigating the application potential of these copolymers in various industries, including automotive, paints, and adhesives, would be valuable.
Emulsion Polymerization of Styrene-Butyl Acrylate Copolymers. (2024, Jan 14). Retrieved from https://studymoose.com/document/emulsion-polymerization-of-styrene-butyl-acrylate-copolymers
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