Volume 41, Issue 9

In order to reduce the damage to soil caused by degradation residues in the application of superabsorbent resin (SAR), the primary target of this study was to improve its biodegradability by doping with starch and cellulose. After that, the water absorption performance of composite SAR doped with starch and cellulose was improved as much as possible by changing the formulation when the biodegradability changed in a narrow range. The degradation percentage in soil and compost after 60 days is much higher than that of the SAR without doping which is 8.42 and 14.17%, but the performance for water absorption depends on the type of starch that was used. Experiments showed that the presence of amylopectin in starch contributes significantly to the performance for water absorption of composite SAR. The more amylopectin content, the better performance for water absorption, but the specific relationship between the degradability and the amylopectin content has not to be proven. Finally, the best mass ratio of starch, cellulose, and acrylic was 4.2:1.8:65, which was determined via the experiments. A kind of composite SAR doped with starch and cellulose with excellent performance was obtained.

Radiation shielding composites based on polyvinyl chloride (PVC) reinforced with different weight ratios of Pb(NO 3 ) 2 (5, 10, and 20 wt%) were prepared using the solution-casting technique. Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy, and tensile testing method were used to characterize the PVC composite films. FTIR and XRD investigations illustrate the structural change and modification of the as-prepared PVC composites. The morphological analysis of the composite revealed that Pb(NO 3 ) 2 was dispersed uniformly within PVC polymer matrix. TGA revealed that the incorporation of Pb(NO 3 ) 2 improved the thermal stability of the investigated composites, whereas adding Pb(NO 3 ) 2 to the polymer matrix worsened its tensile properties. The as-prepared composite films were investigated for radiation-shielding of gamma-rays radioactive point sources ( 241 Am, 133 Ba, 137 Cs, and 60 Co). Linear attenuation coefficient ( μ , cm −1 ), mass attenuation coefficient ( μ / ρ , cm 2 /g), and half-value layer (HVL, cm) have been estimated from the obtained data using the MicroShield program. Reasonable agreement was attended between theoretical and experimental results. The deviation between the experiment and theoretical values of mass attenuation coefficient is being to be lower than 9%, and this can be correlated to the good distribution of Pb(NO 3 ) 2 . The results revealed that adding Pb(NO 3 ) 2 to PVC polymer composites improved their mass attenuation coefficient.

We compared the performance of bio-based and biodegradable polymers for packaging applications. Cost-effective inorganic fillers (talc, kaolin and calcium carbonate) were first melt-compounded with polylactic acid (PLA), poly(butylene adipate-co-terephthalate) (PBAT) and poly(hydroxy butyrate-co-valerate) (PHBV). Following this, injection- and compression-molded specimens were produced to test the effect of filler loading (0–30 wt%) in relation to the morphological, thermal, mechanical and barrier properties of the composites. All the fillers were homogeneously dispersed in the polymer matrices and suitable polymer–filler adhesion was observed for talc and kaolin. The elastic modulus increased at the expense of a reduced tensile and elongation. The most significant improvements in water vapor and oxygen barrier properties were achieved with talc in PLA, PBAT and PHBV films. Overall, the results point to the promise of the introduced compositions for food packaging materials.

A range of ultra-high molecular weight polyethylene (UHMWPE)/tetraphenyltin (Ph 4 Sn) nanocomposites were fabricated by hot-pressing. The surface hardness and crystallinity of composites were studied. It revealed that the surface hardness of the composites decreased slightly, and the changing trend of crystallinity was consistent with the hardness. The tribological properties of composites under seawater lubricating conditions were investigated. The experimental results showed that the friction coefficients of the composites almost keep the same but the wear reduced sharply. With the increases of Ph 4 Sn content, the wear of composites first decreases significantly and then increases, meanwhile the friction coefficient remains basically unchanged. The dominant wear mechanism has changed from adhesive wear to plastic deformation and finally to abrasive wear. The addition of Ph 4 Sn particles reduces the sensitivity of the Ph 4 Sn/UHMWPE composites to water and transfers the load to the UHMWPE network, resulting in the wear resistance improved.

The adoption of polymer nanocomposites in the design/manufacturing of parts for engineering and technological applications showcases their outstanding properties. Among the polymer nanocomposites, polyimide (PI) nanocomposites have attracted much attention as a composite material capable of withstanding mechanical, thermal and electrical stresses, hence engineered for use in harsh environments. However, the nanocomposites are limited to the application area that demands conduction polymer and polymer composites due to the low electrical conductivity of PI. Although, there has been advancement in improving the mechanical, thermal and electrical properties of PI nanocomposites. Thus, the review focuses on recent progress on improving the mechanical, thermal and electrical conductivity properties of PI nanocomposites via the incorporation of carbon nanotubes (CNTs), graphene and graphene oxide (GO) fillers into the PI matrix. The review summarises the influence of CNTs, graphene and GO on the mechanical and conductivity properties of PI nanocomposites. The authors ended the review with advancement, challenges and recommendations for future improvement of PI reinforced conductive nanofillers composites. Therefore, the review study proffers an understanding of the improvement and selection of PI nanocomposites material for mechanical, thermal and electrical conductivity applications. Additionally, in the area of conductive polymer nanocomposites, this review will also pave way for future study.

The purpose of the present work is to enhance the thermal stability and rheological properties of semi-interpenetrating polymer network (IPN) hydrogel based on partially hydrolyzed polyacrylamide/hydroxypropyl guar (HPAM/HPG) nanocomposite reinforced with graphene oxide (GO), at temperatures (200 and 240 °F) for use in oil recovery applications. FTIR spectra of the IPN nanocomposite hydrogels revealed interactions of GO with HPAM/HPG chains. An increase in the viscosity is also observed from the rheological study. Moreover, IPN and its nanocomposite hydrogels exhibited non-Newtonian behavior. The decline of viscosity of IPN nanocomposite hydrogels was observed with an increase in the temperature from 200 to 240 °F but was still higher than IPN hydrogel without GO. Dispersion of GO through the HPAM/HPG hydrogel matrix was evaluated by SEM morphology and electrical conductivity. The IPN nanocomposite hydrogels showed high viscosity stability, thermal stability, and flow activation energy as compared to IPN hydrogel without GO. Therefore, the addition of 0.1 wt.% of GO to the HPAM/HPG matrix is suitable to create a cross-linked polymer solution with improved properties which may be beneficial for use in oil recovery applications.

Tubes from nylon 12 and Pebax 6333 resins were produced using an extrusion process. The extruded tubes were used to produce balloons for angioplasty applications. The tubes were stretched using blow molding process to produce balloons. Melt rheology behavior for nylon 12 and Pebax were studied and nylon 12 showed a more pronounced shear thinning behavior compared to Pebax. Orientations of the tubes and the balloons were assessed using Fourier transform infrared spectroscopy (FTIR) and it was found that nylon material is more sensitive to molecular orientation when stretched compared to Pebax material. Melting behavior for the tubes and balloons were investigated using dynamic scanning calorimetry (DSC). The melting temperature shifted to higher temperatures when the tubes are stretched into balloons and the shift was more pronounced for Pebax balloon than nylon. Morphology of Pebax balloon surface revealed a hybrid structure consisting of hard segments dispersed in soft segments and amorphous phases. The hard segments are crystallized polyamides that are biaxially oriented in the balloon with higher molecular orientation in the radial direction compared to axial direction. This resulted in a higher tensile strength along the radial direction compared to axial for the balloons. Dynamic mechanical analyzer (DMA) tests showed that the glass transition temperature of the nylon tubes shifted to higher temperatures (from 51 to 82 °C) during the balloon forming process, which means the nylon becomes stiffer and less flexible when formed into a balloon.

Bio-based films containing poly (vinyl alcohol)/casein have poor mechanical and water vapor barrier properties that limit their use in packaging application. Some properties such as water resistance and tensile strength can be increased by the cross-linking process. For this reason, poly(vinyl alcohol)/sodium caseinate (PVA/SC) blends were crosslinked by adding glutaraldehyde (GLA) and glyoxal (GL) at different ratios in this work. The films were prepared by solution casting technique. Fourier transform infrared analysis (FTIR) confirmed the crosslinking reaction between the components. As a result of the crosslinking, the thicknesses, water vapor barrier properties and water contact angle values of the films have increased. The total soluble matters (TSM) of PVA/SC film decreased with increasing amounts of crosslinkers and GLA crosslinked films exhibited lower TSM. The addition of GLA and GL resulted in more strengthened films as verified by the tensile test. On the other hand, GLA crosslinked films were more flexible than un-crosslinked and GL crosslinked PVA/SC films. The hydrophilic PVA/SC film became more hydrophobic with the increasing amounts of crosslinkers. With the crosslinking, the PVA/SC film became more thermally stable. In conclusion, the crosslinked PVA/SC films were obtained with suitable properties for packaging applications.

Following the stipulation to replace nondegradable plastics with biodegradable materials in China, cost-effective and water-resistant packaging materials have become increasingly necessary. In this work, lignin reinforced thermoplastic cassava starch (TPS) pieces were prepared by filling glycerol and lignin powder into starch via a melt blending process and then being pressed into thin pieces. A mechanical properties test showed that following the addition of 3 wt% lignin, the tensile strength of the TPS piece was improved to 16.15 MPa from 3.71 MPa of the original TPS piece. The porous structures of the lignin powder tie the TPS macromolecular chains, induce higher crystallization, and thus provide higher tensile strength and lower elongation at break. After sandwiching two pieces of poly (butylene adipateco-terephthalate) (PBAT)/peanut shell powder composite thin film to each side of the TPS piece, the PBAT/TPS/PBAT sandwich gains excellent water resistance properties. However, as soon as the sandwich piece is cut into smaller ones, they absorb water quickly, implying such pieces can be biodegraded rapidly. These characteristics make it especially suitable for use in the preparation of cabinet waste bags, which are generally stirred into organic fertilizer with the cabinet waste. Slow degradation may negatively affect soil health and farm production.

Nanocomposites of single-wall carbon nanotubes in isobutylene isoprene rubber (IIR/SWCNTs) were successfully prepared by a simple and green wet process. The traditional melt mixing process and organic solvent dissolution suffered from unable to effectively disperse the SWCNTs of tangled structure, and degradation of polymer molecules, respectively. Our process very well avoided these two problems. The SWCNTs aqueous solutions emulsified by polyoxyethylene octyl phenol ether (OP-10) were firstly mixed and compounded with IIR rubber at a relatively high temperature, followed by the second step of melt compounding process with the addition of cross-linking agent and accelerators. The SWCNTs were dispersed uniformly, and a fine network was constructed in the matrix of the obtained IIR/SWCNTs nanocomposite with a low percolation threshold. With the concentration of SWCNTs as low as 2 phr, the IIR/SWCNTs nanocomposite received an electrical conductivity of 10 −6 ∼10 −3  S/cm, and a 71% improvement of tensile strength. By varying the loadings of SWCNTs in a certain range, the tensile strength, electrical conductivity, and dielectric property were found tunable. Besides, the nanocomposites also presented strain responsive specific resistance, excellent elongation (600–740%), and better heat resistance.