Morphology and physical properties of polyethylene/silicate nanocomposite prepared by melt intercalation

Jumali MH, Al-Asbahi BA, Ibtehaj K, Yap CC, Qaid SMH, Ghaithan HM, Farooq WA. Improving Photophysical Properties of White Emitting Ternary Conjugated Polymer Blend Thin Film via Additions of TiO2 Nanoparticles

The effect of TiO₂ nanoparticles on the photophysical properties of ternary conjugated polymer (CP) blends of poly(9,9-dioctylfluorene-2,7-diyl) (PFO), poly 9,9-dioctylfluorene-alt-benzothiadiazole (F8BT) and poly(2-methoxy-5(2-ethylhexyl)-1,4 -phenylenevinylene (MEH-PPV) thin films was investigated. This ternary blend used a fixed amount of PFO as the donor with MEH-PPV and F8BT in various ratios as the acceptors. The solution-blending method and the spin-coating technique were used to prepare the blends and the thin films, respectively. Through efficient Förster Resonance Energy Transfer (FRET), the desired white emission was achieved with PFO/0.3 wt.% F8BT/0.5 wt.% MEH-PPV ternary blend thin film. Additions of nanoparticles up to 10 wt.% dramatically intensified the white emission which then dimmed at higher contents due to agglomerations. The current density–voltage characteristics of the nanocomposite thin films exhibited dependency on the content and distributions of the nanoparticles. Finally, a possible underlying mechanism for the intensification of emission is proposed.

The Grafting of PE-g-MA Chains on Graphene Derivatives to Improve Tensile Properties of Polyethylene

Polyethylene chains having functional maleic anhydride groups were grafted on several graphene derivatives. These chain grafted graphene derivatives were added to polyethylene and the properties of the obtained nano-composites were investigated. Modified Hummers' method was employed to produce graphite oxide (GO). Then amino-functionalized GO (AFGO) was prepared through the functionalization of GO by ethylenediamine. Thermally reduced GO (TRGO) was prepared by the heating of the GO in the presence of nitrogen. TRGO was amino-functionalized to obtain amino functionalized nano-graphite (AFNG). Low density polyethylene (PE) and polyethylene grafted maleic anhydride (PEgMA) nano-composites, containing 1 to 3 wt% of the obtained fillers, were produced by solution mixing. With the incorporation of amino-functionalized graphene into PEgMA, the amine groups on the graphene surface and the maleic anhydride in PE chains covalently bonded and improved the mechanical properties of the nano-composites; by comparing PEgMA nano-composite with 1 wt% AFGO and 1 wt% GO, a 155 percent enhancement in the elongation at break was observed. The modulus and tensile strength of these nano-composites increased over the pure matrix. In addition, the effect of PEgMA content in the 1 wt% AFGO nano-composites was studied and the optimum ratio of PEgMA to PE was found to be 0.40 to 0.60. At this ratio, the best mechanical properties were achieved. Also, at 2 wt% nano-filler the elongation at break of the AFNG nano-composite was higher than that of the TRGO nano-composite. AFNG created more chain grafting but AFNG exfoliates more. The electrical conductivity of TRGO powders by amino-functionalization decreased about 20 times. Therefore, the electrical conductivity of the graphene nano-composites was higher than amino-functionalized graphene nano-composites.

Influence of Blending Protocol on the Thermal and Mechanical Properties of HDPE/LLDPE Blend-Based Nanocomposites

Nanocomposites based on high density polyethylene (HDPE)/linear low density polyethylene (LLDPE) blend were prepared by melt compounding in a twin-screw extruder using an organoclay (montmorillonite) as nano-filler and maleic anhydride-grafted linear low density polyethylene (LLDPE-g-MA) as compatibilizer. The effects of two blending protocols were also investigated. In the first blending protocol LLDPE and LLDPE-g-MA were first reinforced with organoclay and then this nanocomposite was later blended with HDPE, and the second blending protocol LLDPE-g-MA was mixed with organoclay first and then this masterbatch was diluted with HDPE and LLDPE. The preparation of the masterbatch resulted in the degradation of polyethylene, with crosslinking formation which increase the viscosity of the polymer and facilitated the dispersion of the organoclay in the polymeric matrix. WAXD and TEM were used to determine the effect of blending protocol and organoclay content on the intercalation and mechanical properties. The introduction of a maleated polyethylene was required to improve the organoclay dispersion in the nanocomposites. Thermal and mechanical properties of the nanocomposites were affected by blending protocols and the content of organoclay. The degree of crystallinity of the materials prepared using the first blending protocol decreased upon the intercalation of clay platelets whereas for the materials obtained using the second blending protocol the degree of crystallinity decreased due the crosslinking which further restricted mobility and diffusion of polymer chains. The nanocomposites show higher values of tensile modulus, flexural modulus and HDT compared to the blend without the addition of organoclay. The OMMT content added to the polymer blend results in significant and well correlated improvements in tensile and flexural moduli.

Tapioca Starch-poly (lactic acid)-based Nanocomposite Foams as Affected by Type of Nanoclay

Tapioca starch (TS), poly (lactic acid) (PLA), and clay nanocomposite foams, with three clays (Cloisite 30B, Na+, and 20A), were prepared by melt-intercalation method. The structural, thermal, physical and mechanical properties were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and Instron universal testing machine, respectively. XRD results indicated that the intercalation of TS/PLA into the nanoclay layers occurred for all three clays. The extents of intercalation depended on the types of clay and were exhibited in the sequence of Cloisite 30B>Na+ > 20A. At the same time, a mixture of intercalation and tactoid phenomena was observed for the TS/PLA/Cloisite Na+ nanocomposite. SEM results indicated a decrease in cell size of the TS/PLA foam matrix with the addition of nanoclay and cells had hexagonal and pentagonal shapes. Melting temperature (Tm) decreased with the addition of clays into TS/PLA matrix. Expansion ratios of the nanocomposites were significantly different (p<0.05) from each other. TS/PLA/Cloisite Na+ nanocomposite had the highest expansion ratio of 20.9 compared to its TS/PLA/Cloisite 20A (9.65) and TS/PLA/Cloisite 30B counterparts (8.23). Addition of Cloisite Na+ resulted in the lowest unit density of 0.046 kg/m3, while no significant differences in unit density were observed for the foams with addition of Cloisite 30B and Cloisite 20A. Bulk spring index (BSI) was influenced significantly (p<0.05) with the addition of nanoclays into the TS/PLA matrix. TS/PLA/Cloisite Na+ nanocomposite had the lowest BSI of 0.936. The bulk compressibility was decreased from 14.1MPa for pure tapioca starch foam to 4.45MPa with the addition of PLA. The nanocomposite with Cloisite 30B showed the highest value of 17.4MPa, followed by those with Cloisite 20A (10.4MPa), and Cloisite Na+ (6.47MPa).

Microwave-Assisted Preparation of Biodegradable Water Absorbent Polyacrylonitrile/Montmorillonite Clay Nanocomposite

Polyacrylonitrile (PAN)/Montmorillonite (MMT) clay nanocomposite was prepared in a microwave oven using a transition metal Co(III) complex taking ammonium persulfate (APS) as initiator with a motive of converting hydrophobic PAN into hydrophilic nanocomposite material via nanotechnology by the inclusion of MMT to the virgin polymer. UV-visible spectral analysis revealed various interactions between the developed complex with other reaction components. The formation of the PAN/MMT nanocomposites was characterized by FTIR. Furthermore, as evidenced by X-ray diffraction (XRD), transmission electron microscopy (TEM), the composite so obtained was found to have nano-order. XRD and TEM were suggesting that montmorillonite layers were exfoliated during the polymerization process. An increasing in the thermal stability for the developed nanocomposite was recorded by thermogravimetric analysis (TGA). The water absorption and biodegradation properties were carried out for its ecofriendly nature and better commercialization.