A facile route for preparing stable co-continuous morphology of LLDPE/PA6 blends with low PA6 content

Preparation of porous antibacterial polyamide 6 (PA6) membrane with zinc oxide (ZnO) nanoparticles selectively localized at the pore walls via reactive extrusion

Antibacterial polymer membranes have been widely used in many fields of our daily life. In this study, porous PA6 membrane with ZnO nanoparticles attaching on to the surface of inner pore walls is prepared. Firstly, SMA (styrene maleic anhydride copolymer) is used to graft onto the surface of ZnO nanoparticle in DMF (dimethylformamide). Then the pre-treated ZnO nanoparticles (ZnO-SMA) are added into SEBS (Styrene-ethylene-butylene-styrene copolymer)/PA6 (60/40 wt/wt) blends with co-continuous morphology. The effects of SMA molecular structure (molecular weight and maleic anhydride content) used for ZnO-SMA nanoparticles on their dispersion states in SEBS/PA6/ZnO-SMA nanocomposites are investigated. When SMA3 (MAH = 8 wt%, Mn = 250,000 g mol^-1), which has relatively higher molecular weight and lower MAH content, is used as the pre-treating agent, ZnO-SMA3 nanoparticles tend to be dispersed at the phase interface in SEBS/PA6/ZnO-SMA nanocomposites. However, when SMA2 (MAH = 23 wt%, Mn = 110,000 g mol^-1) with relatively lower molecular weight and higher MAH content is used, no ZnO-SMA2 nanoparticles locate at the interface but stay within PA6 phase. Porous PA6 membranes are obtained by selectively etching SEBS phase out with xylene. It can be found that porous PA6 membrane containing ZnO-SMA3 nanoparticles still exhibits much better antibacterial property (R = 3.76) toward S. aureus even at a very low ZnO content (0.5 wt%). This result should be ascribed to almost all the ZnO-SMA3 nanoparticles being exposed to the surface of inner pore walls of PA6 membrane. This work proposes an effective method to prepare porous polymer membrane with functional nanoparticles selectively located at the inner pore walls.

A New Strategy for the Use of Post-Processing Vacuum Bags from Aerospace Supplies: Nucleating Agent to LLDPE Phase in PA6/LLDPE Blends

In the aerospace industry, many composite parts are manufactured by processes using plastic vacuum bags made of polyamide 6 (PA6) as a consumable material. This implies that after demolding the part, this plastic material should be discarded, generating a considerable amount of waste. Tons of vacuum bags are discarded and incinerated per month by several companies in this sector, which highlights the need to recycle and/or reuse this material. PA6/linear low-density polyethylene (LLDPE) blends are of great technological interest because they can combine the excellent thermo-mechanical and oxygen barrier properties of the PA6 with high impact strength, good processability, and low cost of LLDPE. The replacement of neat PA6 by the post-processing vacuum bags residue PA6 may be a new strategy for the recycling of this material. In this work, PA6/LLDPE/maleic anhydride-grafted LLDPE (LLDPE-g-MA) (90/5/5) blends were prepared using a co-rotational twin-screw extruder and the neat PA6 was replaced by different contents of post-processing PA6 (5, 10, 15 and 20 wt.%). The mechanical, thermal, and morphological characterization was evaluated. The increase in the content of post-processing PA6 caused an increase in the crystallinity degree of the LLDPE phase, acting as a nucleating agent to the LLDPE phase, reducing the toughening effect of this phase in the blends and, therefore, providing this phase to act as a reinforcing agent.

An effective approach to fabrication of antifouling ultrafiltration membrane based on zwitterionic polyimide

In this study, a new kind of membrane material, an aromatic zwitterionic polyimide (PI) copolymer, was synthesized through a one-pot polymerization reaction by precise variation of the molar ratios of different monomers with specific groups. The zwitterionic PI ultrafiltration (UF) membrane was prepared through an immersion precipitation phase inversion method and thoroughly characterized by scanning electron microscopy, water contact angle measurement, protein adsorption measurement, and UF experiment. The zwitterionic PI membrane showed significantly improved hydrophilicity and permeability and stable antifouling property. The amount of bovine serum albumin adsorbed on the zwitterionic PI membrane was considerably lower compared with the reference PI membrane. According to the cycle UF experiment for protein solution, the zwitterionic PI membrane had a water flux recovery ratio of 86.7%, compared with only 61.1% for the reference PI membrane. Moreover, the irreversible fouling of the zwitterionic PI membrane was significantly decreased, suggesting superior antifouling property. This new approach to the preparation of a zwitterionic polymer seems promising for potential applications in separation membrane.

Preparation and Compatibility Evaluation of Polypropylene/High Density Polyethylene Polyblends

This study proposes melt-blending polypropylene (PP) and high density polyethylene (HDPE) that have a similar melt flow index (MFI) to form PP/HDPE polyblends. The influence of the content of HDPE on the properties and compatibility of polyblends is examined by using a tensile test, flexural test, Izod impact test, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), polarized light microscopy (PLM), and X-ray diffraction (XRD). The SEM results show that PP and HDPE are incompatible polymers with PP being a continuous phase and HDPE being a dispersed phase. The FTIR results show that the combination of HDPE does not influence the chemical structure of PP, indicating that the polyblends are made of a physical blending. The DSC and XRD results show that PP and HDPE are not compatible, and the combination of HDPE is not correlated with the crystalline structure and stability of PP. The PLM results show that the combination of HDPE causes stacking and incompatibility between HDPE and PP spherulites, and PP thus has incomplete spherulite morphology and a smaller spherulite size. However, according to mechanical property test results, the combination of HDPE improves the impact strength of PP.

Compatibilization of Immiscible Polymer Blends Using in Situ Formed Janus Nanomicelles by Reactive Blending

Block or graft copolymers located at polymer-polymer interfaces have been considered as ideal compatibilizers for immiscible polymer blends. Herein, we report a novel compatibilization mechanism using Janus nanomicelles (JNMs) formed in situ at the polymer-polymer interface in immiscible polyvinylidene fluoride (PVDF)/polylactic acid (PLLA) blends. A small amount of a reactive graft copolymer, poly(styrene-co-glycidyl methacrylate)-graft-poly(methyl methacrylate) (P((S-co-GMA)-g-MMA)), is incorporated into the PLLA/PVDF blends by simple melt mixing. The in situ grafting of PLLA chains onto P((S-co-GMA)-g-MMA) during melt mixing leads to the formation of numerous JNMs with a shell structure consisting of PLLA and PMMA hemispheres. These JNMs are located at the PLLA/PVDF interface, where they behave as effective compatibilizers for the immiscible PLLA/PVDF blends. This interfacial micelle compatibilization (IMC) mechanism opens new opportunities to exploit interfacial emulsification using JNMs and should be of great significance in the compatibilization of polymer alloys.

The Effect of Different Peroxide on LDPE Foam Properties in the Presence of Polyfunctional Monomers

The crosslinking promotion effect of different peroxide decomposition temperatures in the formation of crosslinked low density polyethylene/polyfunctional monomers (LDPE)/(PFM) foam was investigated. Two peroxides, namely Dicumyl Peroxide (DCP) and 2,5-Dimethyl-2,5-di(tert-butylperoxy) hexyne-3 (T145), were compared. This was conducted to establish a base performance for the T145 and would essentially open new grounds for work for higher temperatures crosslinking materials. From this work the results indicate that at similar peroxide concentrations, T145 gave a higher crosslinking level than DCP. Comparisons between DCP and T145 indicated that similar gel content was achieved by taking into account molar masses and radicals generated per peroxide molecule. It was determined that the curing cycle time of DCP alone could be reduced by approximately 67% by increasing the curing temperature from 165°C to 185°C. Polyfunctional monomers containing allylic groups, which can generate allylic and alkyl radicals, appeared to be significantly more effective than methacrylates, which generate only alkyl radicals. Foaming behaviour can be predicted from the swell ratio obtained from testing solid crosslinked polymers while the more traditional predictive parameters, gel content and melt modulus, are not universally applicable. Irrespective of peroxide, curing temperature and polyfunctional monomer type and concentration, foam density is shown to be a function of swell ratio. Independent of the type of peroxide, crosslinking promotion was shown to be in the order of TAC > DALP > TMPTMA where the latter actually suppressed crosslinking at higher peroxide concentrations.