Shixin Song

Compatibilization effect of MMA-co-GMA copolymers on the properties of polyamide 6/Poly(vinylidene fluoride) blends

Methyl methacrylate-co-glycidyl methacrylate copolymers (MMA-co-GMA) with different GMA contents were prepared to compatibilize the polyamide 6 (PA6) and poly(vinylidene fluoride) (PVDF) blend. The chemical reactions between the carboxyl/amino end groups of PA6 and the epoxy groups, and the good miscibility between PVDF and MMA-co-GMA were responsible for the excellent compatibilization effect. DMA results showed that the glass transition peaks of PVDF phase almost disappeared in the PA6/PVDF/MMA-co-GMA blends; this proved the suppressed thermal transition due to the restricted movement of PVDF chains. MMA-co-GMA copolymers significantly decreased the phase domain size of the PA6/PVDF blends. PVDF dispersed in the PA6 matrix uniformly and the interface between the two phases was obscure due to the compatibilization. The addition of MMA-co-GMA into the PA6/PVDF blend decreased the crystallization temperature of the PVDF phase, which proved that the compatibilizer enhanced the interaction between PVDF and PA6 and retarded the crystallization. Mechanical tests indicated that the impact strength and elongation at break of the PA6/PVDF blends increased with the addition of MMA-co-GMA. The increase of the fracture toughness was due to the compatibilization effect of MMA-co-GMA copolymers, which induced a delay of the debonding of PA6 and PVDF phases at the interface and inhibited the initiation and propagation of cracks.

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

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.

Performance improvement of poly(vinylidene fluoride) by in situ copolymerization of methyl methacrylate and ionic liquid

Abstract1-Butyl-3-vinylimdazolium tetrafluoroborate ([BVIM][BF4]) was used as ionic liquid to in situ copolymerized with methyl methacrylate (MMA) in poly(vinylidene fluoride) (PVDF) solution by the free radical polymerization method. The content of [BVIM][BF4] in the copolymerized monomers ranges from 0 to 50%. Soxhlet extraction results showed that more than 60% P(MMA-co-[BVIM][BF4]) were grafted onto the PVDF chains and the grafting degree was higher than 15%. 1H NMR tests proved the occurrence of grafting reaction. SEM morphology indicated that phase separation took place for the in situ PVDF/P(MMA-co-[BVIM][BF4]) composites when the [BVIM][BF4] content was more than 40 wt%. FTIR and XRD measurements indicated the crystal transformation of PVDF from α-phase to ß/γ phase due to the ion-dipole interaction between PVDF and [BVIM][BF4]. Furthermore, the introduction of [BVIM][BF4] into the in situ PVDF/P(MMA-co-[BVIM][BF4]) composites enhanced the electrical conductivity and dielectric constant of PVDF. The present method improved the stability of ionic liquid in the PVDF composites and the in situ PVDF/P(MMA-co-[BVIM][BF4]) composites show potential applications in sensor, actuator and battery fields.

Enhanced Properties of PBT/PC Blends with the Addition of Carboxyl-functionalized Multiwalled Carbon Nanotube

Carboxyl-functionalized multiwalled carbon nanotube (c-MWCNT) was used to enhance the properties of poly(butylene terephthalate)/polycarbonate (PBT/PC) blends by melt blending. The c-MWCNT inhibited transesterification reactions between PBT and PC. SEM result showed that most of the c-MWCNT dispersed in the PBT matrix and partial c-MWCNT lied between the interface of PBT and PC phases. c-MWCNT promoted the crystallization of PBT due to the decreased transesterification and the heterogeneous nucleating effect, which led to a 20 C increase of the crystallization temperature. DMA test indicated that the miscibility between PBT and PC decreased with the c-MWCNT loading since the inhibited transesterification. When the c-MWCNT content was 4 wt%, the yield strength of 65.9 MPa and tensile modulus of 2116 MPa were achieved, which corresponded to 23.9 and 19.5% increase relative to the pure PBT/ PC blend. The conductivity and dielectric properties of PBT/PC were largely enhanced by the c-MWCNT. The σdc values of PBT/PC improved greatly by several orders of magnitude from 10 to 10 when the c-MWCNT content was 2 wt%. The dielectric constant at 100 Hz for the nanocomposites increased from 2.8 to 146 when the c-MWCNT loading varied from 0.1 to 4 wt%, which improved more than 50 times.

A Facile Strategy to Enhance the Dielectric and Mechanical Properties of MWCNTs/PVDF Composites with the Aid of MMA-co-GMA Copolymer

A facile strategy is adopted to prepare carboxylic functionalized multiwalled carbon nanotube (c-MWCNT) modified high dielectric constant (high-k) poly(vinylidene fluoride) (PVDF) composites with the aid of methyl methacrylate-co-glycidyl methacrylate copolymer (MG). The MG is miscible with PVDF and the epoxy groups of the copolymer can react with the carboxylic groups of c-MWCNT, which induce the uniform dispersion of c-MWCNT and a form insulator layer on the surface of c-MWCNT. The c-MWCNTs/MG/PVDF composites with 8 vol % c-MWCNT present excellent dielectric properties with high dielectric constant (~448) and low dielectric loss (~2.36) at the frequency of 1 KHz, the dielectric loss is much lower than the c-MWCNT/PVDF composites without MG. The obvious improvement in dielectric properties ascribes to the existence of MG, which impede the direct contact of c-MWCNTs and PVDF and avoid the formation of conductive network. Therefore, we propose a practical and simple strategy for preparing composites with excellent dielectric properties, which are promising for applications in electronics devices.

Research of the synthesis and film performance of silica/poly(St-BA-MPS) core-shell latexes obtained by miniemulsion co-polymerization

Colloid silica nanoparticles were hydrophobic modified by γ-methacryloxypropyl trimethoxysilane (MPS) for the encapsulation into polymer. The alkoxysilane-functionalized core-shell latexes were successfully synthesized via miniemulsion copolymerization of the butyl acrylate, styrene with MPS as the functional monomer in the presence of the modified silica. When these latexes dried at room-temperature, the post-cross-linking occurred due to the alkoxysilane groups on the particle surface and lead to the formation of the films. The morphology of the nanocomposite latexes and the mechanical properties, thermal properties, fire-resistant, optical properties and micro-structure of the resulted films were characterized and discussed. Scanning electron microscope result showed most of the nanoparticles dispersed homogeneously in the polymer matrix when the content of MPS-silica was 10%. However, when the content of MPS-silica nanoparticles was beyond 10%, the aggregation of the nanoparticles became obvious. The tensile test showed that the stress at break increased a lot with the increase of silica content. The thermal and fire-resistant behaviors of the nanocomposite films were improved greatly by the incorporation of silica particles. The optical test showed that the hybrid film was comparable to the pure polymer film at around 84% transmittance.