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. 2017 Aug 16;10(8):957.
doi: 10.3390/ma10080957.

Grafting Modification of the Reactive Core-Shell Particles to Enhance the Toughening Ability of Polylactide

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Free PMC article

Grafting Modification of the Reactive Core-Shell Particles to Enhance the Toughening Ability of Polylactide

Zhaokun Li et al. Materials (Basel). .
Free PMC article

Abstract

In order to overcome the brittleness of polylactide (PLA), reactive core-shell particles (RCS) with polybutadiene as core and methyl methacrylate-co-styrene-co-glycidyl methacrylate as shell were prepared to toughen PLA. Tert-dodecyl mercaptan (TDDM) was used as chain transfer agent to modify the grafting properties (such as grafting degree, shell thickness, internal and external grafting) of the core-shell particles. The introduction of TDDM decreased the grafting degree, shell thickness and the Tg of the core phase. When the content of TDDM was lower than 1.15%, the RCS particles dispersed in the PLA matrix uniformly-otherwise, agglomeration took place. The addition of RCS particles induced a higher cold crystallization temperature and a lower melting temperature of PLA which indicated the decreased crystallization ability of PLA. Dynamic mechanical analysis (DMA) results proved the good miscibility between PLA and the RCS particles and the increase of TDDM in RCS induced higher storage modulus of PLA/RCS blends. Suitable TDDM addition improved the toughening ability of RCS particles for PLA. In the present research, PLA/RCS-T4 (RCS-T4: the reactive core-shell particles with 0.76 wt % TDDM addition) blends displayed much better impact strength than other blends due to the easier cavitation/debonding ability and good dispersion morphology of the RCS-T4 particles. When the RCS-T4 content was 25 wt %, the impact strength of PLA/RCS-T4 blend reached 768 J/m, which was more than 25 times that of the pure PLA.

Keywords: core-shell particles; grafting modification; polylactide; toughening.

Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Schematic pictures of the RCS core-shell particles.
Figure 2
Figure 2
Tanδ-temperature curves of RCS particles with different TDDM content.
Figure 3
Figure 3
Influence of TDDM content on the properties of RCS particles (a) grafting degree and glass transition temperature (Tg) (b) particle size and shell thickness.
Figure 4
Figure 4
Dispersed phase morphology of PLA blends with different RCS particles (a) PLA; (b) PLA/RCS-T0; (c) PLA/RCS-T2; (d) PLA/RCS-T4; (e) PLA/RCS-T6; (f) PLA/RCS-T8. (The red cycles show the agglomeration of RCS particles)
Figure 4
Figure 4
Dispersed phase morphology of PLA blends with different RCS particles (a) PLA; (b) PLA/RCS-T0; (c) PLA/RCS-T2; (d) PLA/RCS-T4; (e) PLA/RCS-T6; (f) PLA/RCS-T8. (The red cycles show the agglomeration of RCS particles)
Figure 5
Figure 5
DSC thermogram of PLA and PLA/RCS blends recorded during the second heating (a) and cooling (b) runs.
Figure 6
Figure 6
Tan δ-temperature (a) and E’-temperature (b) curves of PLA and PLA/RCS blends.
Figure 7
Figure 7
Mechanical properties of PLA/RCS blends (a) Impact strength; (b) Yield strength.
Figure 8
Figure 8
Fracture surface morphologies of PLA and PLA/RCS blends. (a) PLA; (b) PLA/RCS-T0; (c) PLA/-T2; (d) PLA/RCS-T4; (e) PLA/RCS-T6; (f) PLA/RCS-T8.
Figure 8
Figure 8
Fracture surface morphologies of PLA and PLA/RCS blends. (a) PLA; (b) PLA/RCS-T0; (c) PLA/-T2; (d) PLA/RCS-T4; (e) PLA/RCS-T6; (f) PLA/RCS-T8.
Figure 9
Figure 9
Deformation zone morphologies of PLA/RCS blends. (a) PLA/RCS-T0; (b) PLA/RCS-T2; (c) PLA/RCS-T4; (d) PLA/RCS-T6; (e) PLA/RCS-T8.
Figure 9
Figure 9
Deformation zone morphologies of PLA/RCS blends. (a) PLA/RCS-T0; (b) PLA/RCS-T2; (c) PLA/RCS-T4; (d) PLA/RCS-T6; (e) PLA/RCS-T8.

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