Volume 43, Issue 9

In this study, the development and characterization of a plant-derived biopolymer, gum acacia, chemically modified by an herbal dye, red beetroot (Latin Beta vulgaris ) has been presented. Red beetroot, a flowering plant with abundant phytochemicals, prevents diseases and produces colorful chromophores. Chromophores interact with incident intense electromagnetic field and thereby absorb radiation in ultraviolet and/or visible region of the spectrum, promoting low to high-level electron excitation between different energy states. Such transition influences variation in optical and electrical properties of the system. Optical properties of both biopolymer unmodified gum acacia specimen and after modification with red beet induced chromophore are investigated by UV–visible absorption spectroscopy. Pronounced light absorption is observed in the visible range of the spectrum compared to the unmodified specimen in which absorption is found to be observed in the deep ultraviolet range. Electrical characterization of the modified biopolymer with red beetroot extract suggests eviation from ideal dielectric relaxation obeying Debye mechanism. Electrical conductivity is found to be enhanced over pure specimen. These properties are eligible for application in energy storage devices, especially as a sensitizer in photovoltaic material which are ongoing extensive research area.

Two isotactic polypropylene (iPP) resins with approximate weight-average molecular weight ( Mw ) and different molecular weight distribution ( MWD ) were chosen to prepare cast films by the melt-stretching method. The lamellar morphology and mechanical properties of the initial precursor films and stretched microporous membranes were characterized. It was found that PP1 resin with a broader MWD exhibits a higher relaxation time of around 5.5 s, a larger entanglement density of 24.7 mol/m 3 and fast crystalline ability. The lamellar lateral size, orientation degree and entanglement density of the corresponding cast film are significantly increasing, resulting in higher elastic recovery and more apparent strain-hardening behavior. The PP resin with broader MWD also benefits the pore formation, resulting in a larger pore size and better air permeability of the stretched microporous membrane.

As the second largest synthetic rubber after styrene butadiene rubber, cis-butadiene rubber (BR) is one of the important raw materials for automobile tires and cold-resistant products. Herein, a traditional rubber preparation process was used to introduce dynamic reversible bonds into BR based on an “imitative” click reaction. Compared with traditional complex self-healing techniques, this method is undoubtedly simpler and more efficient. Dynamic reversible bonds are able to break and recombine under the stimulation of external conditions, which endow rubber with self-healing properties. We use the small biological molecule lipoic acid (LA) as a cross-linking agent and cross-link LA and BR through mechanical compounding and hot press vulcanization to obtain self-healing butadiene rubber (BLA). In addition, BLA-(Zn 2+ ) was further prepared by introducing Zn 2+ to form metal-oxygen coordination bonds with carboxyl groups. And systematically studied the effect of Zn 2+ on the mechanical properties and self-healing properties of cross-linked BR. Through the combined action of disulfide bonds, hydrogen bonds and Zn 2+ -O coordination bonds, BLA-(Zn 2+ ) has better properties than BLA, the tensile strength can reach 3.76 MPa, and the repair efficiency is about 82 %. This simple preparation process is certainly more cost effective.

Effective anti-infection prophylaxis for chronic wounds can reduce the risk of wound infection and improve healing rates. The use of good anti-infection wound dressings is particularly important. In this paper, an antimicrobial composite hydrocolloid sponge dressing with zinc oxide nanoparticles, hydroxypropyl chitosan, and polyvinyl alcohol as the main components was prepared using freeze-drying of the formulated suspensions. The characterizations by scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy were performed; the antibacterial activity was determined; the on-demand dissolving properties were evaluated; and the basic properties such as porosity, vapor permeability, and water absorption were measured. The results showed that, when the mass ratio of HPCs/PVA was 6:4, the porosity, the steam permeability, the water absorption ratio, and dynamic complete dissolving time in 1 % acetic acid aqueous solution, respectively, reached the optimum value of 63.2 %, 57.7 %, 54.4, and 35 min. Antibacterial activity experiments showed that the sponges significantly inhibited Staphylococcus aureus , Escherichia coli , and Candida albicans . In conclusion, the above results indicate that the prepared hydrocolloid composite sponge has good air permeability, water absorption, antibacterial activity, and on-demand dissolving property and has potential applications in anti-infection treatment of hypo-exudative chronic wounds and pressure sore prevention.

In plastic injection molding (PIM), the process parameters determine the quality and productivity of molded parts. The traditional injection molding process analysis method mainly relies on production experience. It is lack of advanced and rationality and seriously increases production costs. In this paper, a hybrid multiobjective optimization method is proposed to minimize the warpage, volumetric shrinkage and cycle time. The method integrates orthogonal experimental design, numerical simulation, and the metamodel method with multiobjective optimization. The orthogonal experiment chooses seven parameters as the design variables to generate sampling data and determines key factors that affect product quality by the numerical simulation. A gradient-enhanced Kriging (GEK) surrogate model strategy is introduced to construct the response predictors to calculate objective responses in the global design space. Multipopulation differential evolution (MPDE) is conducted to locate the Pareto-optimal solutions, where the response predictors are taken as the fitness functions. This study shows that the proposed GEK-MPDE method can reduce warpage, volumetric shrinkage and cycle time by 5.7 %, 4.7 %, and 18.1 %, respectively. It helps plastic industry to realize collaborative scheduling of multiple tasks between different production lines by providing a low-cost and effective dynamic control method.