Journal of Plastic Film & Sheeting

Rice husk and nanoclay (montmorillonite)-filled low-density polyethylene composite films were prepared by extrusion blown film. Maleic anhydride-modified polyethylene was used as compatibiliser in various concentrations ranging from 0 to 8 parts per hundred. X-ray difractograms showed an increase in interlayer spacing of montmorillonite from the use of compatibiliser when compared to the uncompatibilised composites; an increase of 20, 33, 36 and 38% for 2, 4, 6 and 8 parts per hundred, respectively, of maleic anhydride-modified polyethylene. With the incorporation of maleic anhydride-modified polyethylene, a better dispersion of the fillers was also achieved, as confirmed by scanning electron microscopy. The compatibilised composite films showed improved tensile and barrier properties. The addition of 4 parts per hundred of the compatibiliser resulted in an improvement by 22% in tensile strength. Furthermore, oxygen barrier property of the composite films improved more than twofold by adding 4 parts per hundred of maleic anhydride-modified polyethylene. This improvement in tensile and barrier properties is due to an increase in the interfacial adhesion between the fibre and matrix and better dispersion of impermeable nanoparticles.

Polystyrene/thermoplastic starch blends from 90/10 to 50/50 (w/w) were prepared by melt blending. Blends were characterized by scanning electron microscopy (morphology); thermogravimetric analysis (thermal stability and weight content of each component); Fourier transform infrared spectroscopy (identification of functional groups); differential scanning calorimetry (thermal properties); tensile tests (strength, modulus, elongation at break and tenacity) and biodegradation in soil (biodegradability). The biodegradation process was also followed by thermogravimetric analysis calculating the loss of each component after removing the samples from soil at different time intervals. Scanning electron microscopy results showed good starch dispersion in the blend. The Fourier transform infrared spectroscopy analysis suggested that only physical interaction took place between the polystyrene and the thermoplastic starch. The tensile tests revealed a considerable decrease in the mechanical properties of the polystyrene-thermoplastic starch blends as a function of the thermoplastic starch content. The 50/50 blend showed decreases of 48% in the Young’s modulus, 62% in the tensile strength and increases of 62% in the elongation at break, in comparison to neat polystyrene. The biodegradability tests showed that the greater the thermoplastic starch concentration in the blend, the faster the mass loss, which was also confirmed by the thermogravimetric analysis and Fourier transform infrared spectroscopy analysis.

Two grades of 5 mm thick polypropylene (PP) sheets, one having linear polymer chains (PP-TF-1) and the other having long-chain branches (PP-TF-2), were drape formed, using moulds of different parameters. Single-sided heating of sheet was found to be suitable only at lower depths of draw. Double-sided heating gave good part shape conformance at all depths of draw. PP-TF-2 was found to have lower crystallinity than PP-TF-1, suggesting that it would have a lower sagging tendency and would give parts with more uniform wall thickness distribution. This was confirmed in formability studies. At higher depths of draw, an increase in draft angle was found to give more uniform wall thickness distribution, maintaining reasonable values of wall thickness. At lower depths of draw, draft angle was found to have no influence on product quality. Irrespective of material characteristics and other mould parameters, only moulds with generous values of corner radii gave strong corners.

Poly(azo-pyridyl-urethane)/multi-walled carbon nanotube (PAPU/MWCNT) nanocomposites were prepared by first synthesizing polyurethane followed by solution dispersing MWCNT in the matrix. We have used two different MWCNTs: the first set of MWCNT contained carboxylic acid group (MWCNT-COOH) and the second set contained acid chloride group (MWCNT-COCl). Afterward, these MWCNT particles were used in the preparation of PAPU/MWCNT nanocomposites. In the first set of nanocomposites, MWCNT-COOH and PAPU were just physically mixed and were designated as PAPU/MWCNT-A. In the second set of nanocomposites, PAPU chains were tethered onto the surfaces of MWCNT-COCl particles and designated as PAPU/MWCNT-AC. Two types of nanocomposites were thus fabricated, including acid functionalized nanotube-based non-tethered PAPU/MWCNT and acid chloride functionalized MWCNT-based tethered system. We have incorporated hydroxyl end-terminated polyurethane via “grafting to” approach to acid chloride functional MWCNT through esterification. Fourier transform infrared spectra confirmed that the matrix was covalently attached to sidewalls of nanotube. Various nanotube loading levels and surface-modified groups were considered to regulate mechanical, thermal and electrical performance of PAPU/MWCNT. The experimental results showed that a moderate loading level of 5 wt. % MWCNT produced the maximum tensile strength (63.1 MPa) in tethered nanocomposites, while the presence of surface carboxylation of MWCNT relatively decreased the tensile strength (49.7 MPa). Comparative studies based on scanning and transmission electron microscopy of the chemically bonded samples revealed unique nano-fibriller morphology. Dynamic mechanical analysis of nanocomposite films showed an increased segmental rigidity with T_g of 144–153℃ in the tethered system relative to pristine PAPU (133℃). Addition of acid chloride functional MWCNT also contributed to an enhancement in the conductivity (2.9–4.7 S cm⁻¹), relative to PAPU/carboxylated MWCNT (2.0–2.7 S cm⁻¹).

Nanocomposite composed of amine-terminated polyamide (an aramid)/bisphenol A diglycidyl ether epoxy matrix and functionalized and non-functionalized multi-walled carbon nanotube have been fabricated. Polyamide/bisphenol A diglycidyl ether/multi-walled carbon nanotube nanocomposite was cured at 120℃ with different filler content. In order to investigate the influence of functional filler on nanocomposite properties, morphological, mechanical and thermal profile of polyamide/bisphenol A diglycidyl ether nanocomposite with varying multi-walled carbon nanotube content were studied. Functional multi-walled carbon nanotube-reinforced nanocomposite showed greater strengthening at all weight percent as they actively control the failure mechanism; 5 wt% functional multi-walled carbon nanotube-based sample showed 62% improvement in toughness i.e. area under the stress–strain curve (35.6 J/m³) relative to non-functional (13.7 J/m³) nanocomposite. The ultimate tensile strength also improved from 39.2 to 59.7 MPa. The multi-walled carbon nanotube ratio was an interesting feature significantly influencing the properties of polyamide/bisphenol A diglycidyl ether/multi-walled carbon nanotube due to the contribution of hydrogen bonding and π-π staking between the matrix and filler. Thermal stability consistently increased with amalgamation of functional multi-walled carbon nanotube in the polyamide/bisphenol A diglycidyl ether matrix (T₀ 523–565℃; T_g 247–253℃) over polyamide/bisphenol A diglycidyl ether /non-functional multi-walled carbon nanotube (T₀ 499℃; T_g 246℃). Novelty of the research lies in exclusive architecture, exceptional heat stability and mechanical properties of aramid/epoxy-based nanocomposite.