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Preparation of Water-borne Binders with Low Modulus and High Strength Characteristics Via Highly Efficient Coupling Reaction Being Confined on the Colloidal Interface

Author: YangHai
Tutor: YangLei
School: Zhejiang University of Technology
Course: Textile Chemistry and Dyeing and Finishing Engineering
Keywords: RAFT polymerization Emulsion polymerization Block copolymer Microphase separation structures Latex film Binder
CLC: TS190.2
Type: Master's thesis
Year: 2013
Downloads: 4
Quote: 0
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Abstract


Water-borne binders have wide applications in the dyeing and finishing industry. Thebinders are expected to have the mechanical properties of low modulus and high tensile strength,contributing to the soft handling and high-rank crockfastness of the finished fabrics. However,due to the closely coupled relationship between modulus and tensile strength, it is difficult toachieve a balance between handling and crockfastness. Extensive studies, which focus on ABAtriblock copolymer solvent film and their melt processed bulk materials, show that microphaseseparation structures form in the copolymers. It allows the material to show target tensileproperties, especially when the hard block domains (i.e., polystyrene, PSt.) dispersed in the softblock matrix(i.e., polybutyl acrylate, PBA). However, during the triblock latex film formationprocess, the assembled structures will be hindered from reaching global equilibrium states as aresult of the slow kinetics of block copolymers. Therefore, poly (butylacrylate)-b-polystyrene-b-poly (butyl acrylate)(PBA-b-PSt-b-PBA, SBAS) latex film couldexhibit completely different mechanical behaviors from those observed for its solvent filmcounterpart. In the current thesis, we depicted a novel method of constructing polymer chainstructure together with the latex film nanostructure via the combination of highly efficientcoupling reaction with assembly of PBA-b-PSt diblock copolymer shell-core latex particles.First, an amphiphilic macro-RAFT agent, namely, poly(N,N-dimethylacrylamide)-b-poly(n-butyl acrylate-co-glycidyl methacrylate) block copolymer with a trithiocarbonategroup, is used to mediate RAFT batch-semicontinuous two-step emulsion polymerizationstargeting at well-defined poly(n-butyl acrylate)-b-polystyrene (PBA-b-PSt) diblock copolymerlatex with shell-core morphology. RAFT BA emulsion polymerization was proved to besuccessful, but the addition of St led to the reaction exhibiting instability, limiting St conversionand multi-peak molecular weight distribution of products.Then, RAFT batch-semicontinuous two-step miniemulsion polymerizations were tried andallowed to produce the target PBA-b-PSt diblock copolymer shell-core latex successfully, where epoxy groups were confined on the particle surface. The copolymer composition was varied bychanging PBA block length. When the latexes were dried, epoxy groups underwent highlyefficient curing reactions triggered by a thermal-latent curing agent (dicyandiamide) in acontrolled manner, leading to the formation of bonded PBA blocks connecting the PSt blocks indifferent particles. TEM revealed the occurrence of ‘spherical’ microphases of PSt in all thecross-linked latex films, which correlated well with that observed for the latex particles. Thefilms behaved as vulcanized elastomer during tensile tests. Modulus and elongation at breakwere functions of copolymer compositions, whereas ultimate tensile strength remained fairlyconstant in the range between5MPa and7.0MPa. As PSt content was below35%, the tensileproperties of these latex films were comparable with those of their linear ABA type blockcopolymer solvent film counterparts with similar compositions.The diblock copolymer latex binder films with90K-30K and120K-30K copolymercompositions show low modulus and high strength characteristics. These tensile properties werefar superior to those of either the statistic copolymer with same compolymer compositions or thecommercially available FT-321binder. As a result, the pigment dyed fabrics using diblockcopolymer latex as binders show high-rank color crockfastness together with better handling incomparison to the samples using FT-321.

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CLC: > Industrial Technology > Light industry,handicrafts > Textile industry,dyeing and finishing industry > Dyeing and finishing industry > General issues > Dyes, pigments, pharmaceutical and additives
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