Synthesis, Characterization and Adhesive Property Analysis of Poly(Butyl Acryalteco- α- Methyl styrene) copolymer

Transcription

1 Synthesis, Characterization and Adhesive Property Analysis of Poly(Butyl Acryalteco- α- Methyl styrene) copolymer Abhijit Bandyopadhyay Department of Polymer Science and Technology University of Calcutta 92, A.P.C. Road, Kolkata , INDIA

2 Architecture in Polymers

3 Architecture vis-à-vis Properties Architecture affects: Chain Entanglement Density Glass Transition Temperature Functionality Void space Properties: Mechanical Properties Solution/ Melt Properties Surface Properties

4 Block Copolymer Subsequently bonded different homopolymers where each set of homopolymer refers as a block Eg: ABA Triblock copolymer Commercial Production-Highly Specialized Reaction Living Anionic Polymerization Restriction in choice of monomers for block design Laboratory Trials ATRP, RAFT Methods

5 Practical Issues with ATRP/RAFT Methods: Though these polymerization techniques provides a better control over polymeric structures, but there are major disadvantages of ATRP/RAFT which hinders its commercialization: It requires high concentrations of transition-metal catalysts, primarily copper halides, which end up as residue in the products. These copper contaminants have to be removed for the polymer products to be useful commercially Separation is difficult Process is expensive as a whole

6 Polymerization via ATRP

7 Block Copolymerization through FRP- Theoretical Aspect M 1 and M 2 are the two set of monomers taken for copolymerisation and k denotes the respective reaction rates Monomer Reactivity Ratio For Block Copolymers

8 Block Copolymerization through FRP- Practical Issues Impaired kinetics- slow initiation followed by fast propagation and finally even faster termination At any point of time a FRP system contains unreacted monomers, matured polymers and only a fewer (10-7 ) growing chains Production of dead polymer through termination Cross-Propagation Chain Transfer and Back Biting

9 To explore the possibility of: Our intervention Slowing down the propagation rate and ruling out the termination step (Living???) to form the subsequent block in a Free Radical Polymerization To achieve that: A vinyl derivative having a higher conjugation length was selected and used as a special reagent that could possibly offer both slower propagation kinetics and living chain end instead of producing dead ends

10 Objective Synthesis of a Block Copolymer Adhesive using living FRP with higher cohesive strength Technique: Emulsion (oil-in-water) Reagents: N- butyl acrylate (monomer for adhesion and tack) α- Methyl styrene (monomer for cohesive strength) Potassium persulfate (KPS) (initiator) Sodium lauryl sulfate (SLS) (Emulsifier) Sodium bicarbonate (ph adjustment) Water (medium) Special reagent Potassium chloride (de emulsifier)

11 Synthesis SLS and sodium bicarbonate were dissolved in water Butyl acrylate and the special reagent were mixed together and added into the medium Drop wise addition of KPS Formation of homopolymer block of Poly (butyl acrylate) with living end 6hrs 80ºC

12 Seeded latex with unreacted butyl acrylate Addition of more SLS and KPS 18 hrs 60ºC Drop wise addition of alpha methyl styrene Poly (butyl acrylate)-b-butyl acrylate-co-α-methyl styrene

13 Schematic Step: 1 80ºC, 6hrs Seed latex of Poly BA

14 Step 2 60ºC, 18hrs KPS Block Copolymer of a homopolymer of poly (butyl acrylate) followed by a copolymer block of poly (butyl acrylate-co-αmethyl styrene)

15 Copolymer Structure- Logical Aspect Rise in intrinsic viscosity after step 1- Living polymerization A low ceiling temperature of α-methyl styrene (70 0 C)- slow rate of polymerization inducing unreacted butyl acrylate to react along in step 2

16 Characterization- Spectroscopy FTIR spectrum White and sticky mass

17 1H NMR Spectrum

18 Characterization- Chromatography A wider molecular weight distribution implicates a typical FRP

19 Characterization: Rheometry Test parameters: Linear viscoelasticity at 30 0 C in parallel plate (dia:20 mm) with a small amplitude oscillatory shear mode G / > G // implicates higher cohesive strength Viscosity shows a typical Newtonian flow behavior characteristic of a high PDI

20 Tack Test- indigenous method The tack test was performed in the same parallel plate configuration. 0.5 gm of sample was placed in between the two plates of diameter- 20mm and the plates were tightly pressed for 10s under a constant force of 0.01kgf. After 10s, the plates were separated at a constant separation force of 0.1kg and the separation distance (bottom plate fixed) achieved against a fixed separation time of 25 sec was computed for the analysis of tack property.

21 The purified homopolymer of poly (butyl acrylate) after an initial displacement showed a sharp displacement of the upper platen The copolymer showed zero displacement in the final stage The net displacement showed by the homopolymer was 0.9 mm while that in the copolymer was only 0.5 mm implicating higher tack of the latter

22 Lap Shear Test Lap Shear determines the shear strength of adhesives for bonding materials when tested on a single-lap-joint specimen. The test is applicable for determining adhesive strengths, surface preparation parameters and adhesive environmental durability. There are a variety of ASTM single-lap-joint shear tests including ASTM D1002 which specifies lap shear for metal to metal, ASTM D3163 for plastics joints, ASTM D5868 for fiber reinforced plastics (FRP) against itself or metal etc.

23 Test Procedure: Two specimens are bonded together with adhesive as specified overnight under a constant load. The test specimens are placed in the grips of a universal testing machine and pulled at 1.3 mm/min (0.05 in/min) until failure. Specimen Size: Two specimens, each 25.4 x mm (1" x 4") were bonded together with adhesive so that the overlap was sufficient to provide failure in the adhesive, and not in the substrate. Typical overlaps were 12.7 mm and 25.4 mm (0.5" and 1"). The specimens were initially abraded before application of adhesive

24 The joints were prepared between: Rubber-Rubber Metal- Metal Metal- Rubber Rubber- Fabric

25 Lap Shear Strength comparison

26 Conclusion The characterization data implies that we were able to design a living FRP system for synthesis of tailor-made polymer structure- first objective Insertion of a small amount of alpha methyl styrene had eventually improved the cohesive strength as well as tack property of the adhesive- second objective The adhesive was found to be more active in adhering metal-metal and metal-rubber interfaces which can be explored further through tuning the composition further

27 Acknowledgement My students- Roumita, Tamalika, Srijoni who have done this work and still working on it for further improvement in material design HASETRI- for extending the GPC facility IRI- for invitation

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