The Succession of Bacterial Community Attached on Biodegradable Plastic Mulches During the Degradation in Soil

Despite the increasing application of biodegradable plastic mulches (BDMs) in agriculture, the colonization and succession of the attached microbial community on BDMs during their degradation processes remain poorly characterized. Here, we buried four types of commonly used BDMs, including pure polylactic acid (PLA), pure polybutylene adipate terephthalate (PBAT), and two mixtures of PLA and PBAT (85:15 and 15:85 w/w), and one classic polyethylene (PE) mulch in soil for 5 months. Both plastic components and incubation time significantly shaped the β-diversities of microbiota on the plastic mulches (p < 0.001). Meanwhile, the microbial compositions and community structures on BDMs were significantly different from PE mulch, and when excluding PE mulch, the microbiota varied more with time than by the composition of the four BDMs. The orders Burkholderiales and Pseudonocardiales were dominant on most BDMs across different time points. The genus Ramlibacter was revealed as a common biomarker for both PLA and PBAT by random-forest model, and all biomarkers for the BDMs belonged to the dominant order Burkholderiales. In addition, degradation-related and pathogen-related functional taxa were enriched in all mulches among all 40 functional groups, while surprisingly, potential pathogens were detected at higher levels on BDMs than PE. For community assembly on all mulches, the drift and dispersal processes played more important roles than selection, and in particular, the contribution of stochastic drift increased during the degradation process of BDMs while selection decreased, while the opposite trend was observed with PE mulch. Overall, our results demonstrated some degradation species and pathogens were specifically enriched on BDMs, though stochastic processes also had important impacts on the community assembly. It suggested that, similar to conventional plastic mulch, the increased usage of BDMs could lead to potential hazards to crops and human health.

Modification of the Cavity of Plastic Injection Molds: A Brief Review of Materials and Influence on the Cooling Rates

In the 21st century, a great percentage of the plastic industry production is associated with both injection molding and extrusion processes. Manufactured plastic components/parts are used in several industry sectors, where the automotive and aeronautic stand out. In the injection process cycle, the cooling step represents 60% to 80% of the total injection process time, and it is used to estimate the production capabilities and costs. Therefore, efforts have been focused on obtaining more efficient cooling systems, seeking the best relationship between the shape, the quantity, and the distribution of the cooling channels into the injection molds. Concomitantly, the surface coating of the mold cavity also assumes great importance as it can provide increased hardness and a more straightforward demolding process. These aspects contribute to the decrease of rejected parts due to surface defects. However, the effect of the coated cavity on the heat transfer and, consequently, on the time of the injection cycle is not often addressed. This paper reviews the effects of the materials and surface coatings of molds cavity on the filling and cooling of the injection molding cycle. It shows how the design of cooling channels affects the cooling rates and warpage for molded parts. It also addresses how the surface coating influence the mold filling patterns and mold cooling. This review shows, more specifically, the influence of the coating process on the cooling step of the injection cycle and, consequently, in the productivity of the process.

Features of boriding die steel D5 by electron beams

The microstructure and microhardness of the boride layers formed on die D5 steel by the methods of electron beam borating in vacuum under continuous and impulsive bunch modes are investigated and confronted. Formed layers have a heterogeneous structure, which combines solid and plastic components resulting in the fragility reduction of boride layer.

Film thickness interrelationship of base oil and grease lubricated compliant and hard non-conformal contacts

The interfaces of plastic components are often operated as self-lubricating or lubricated with greases close to the piezoviscous-elastic lubrication regime. However, current basic tribological knowledge about grease-lubricated compliant contacts is still very limited. This experimental study provides insight into relations between film thicknesses of grease and its base oil in compliant polymethylmethacrylate–steel and stiff glass–steel point contacts at different speeds and loads. The results are compared with predictions. The ratio between grease and its base oil film thickness was found to be significantly influenced by the interplay of load and the non-Newtonian response of grease, especially for the compliant contact, while the effect of speed and the slide-to-roll ratio was considerably lower. The role of viscoelasticity and grease thickener concentration is discussed.

Taguchi Optimization of Roundness and Concentricity of a Plastic Injection Molded Barrel of a Telecentric Lens

Plastic is an attractive material for the fabrication of tubular optical instruments due to its light weight, high strength, and ease of processing. However, for plastic components fabricated using the injection molding technique, roundness and concentricity remain an important concern. For example, in the case of a telecentric lens, concentricity errors of the lens barrel result in optical aberrations due to the deviation of the light path, while roundness errors cause radial stress due to the mismatch of the lens geometry during assembly. Accordingly, the present study applies the Taguchi design methodology to determine the optimal injection molding parameters which simultaneously minimize both the overall roundness and the overall concentricity of the optical barrel. The results show that the geometrical errors of the optical barrel are determined mainly by the melt temperature, the packing pressure, and the cooling time. The results also show that the optimal processing parameters reduce the average volume shrinkage rate (from 4.409% to 3.465%) and the average deformations from (0.592 mm to 0.469 mm) of the optical barrel, and the corresponding standard deviation values are reduced from 1.528% to 1.297% and from 0.263 mm to 0.211 mm, respectively. In addition, the overall roundness and overall concentricity of the barrel in the four planes are positively correlated.

Experimental Investigation on Concrete with E-waste - A Way to Minimize Solid Waste Deposition

In recent years, the generation of Electronic waste (E-waste) has increased to a greater extent worldwide. The use of electronic devices has proliferated in recent decades and proportionality, and the quantity of electronic devices that are disposed of is growing rapidly throughout the world. Electronic waste (E-waste) typically includes general household electronics, discarded electronic gadgets, and circuit boards. With the growing use of consumer electronics, there is a huge generation of E-waste every day. Reuse of E-waste plastics as aggregates or filler in some or other forms of in construction industry may be considered as economical and technically viable for solving the disposal of a large amount of waste and this can be used as aggregates and fine filler in concrete or the construction of flexible pavement. The idea was to determine whether E-waste plastic components can be used as an alternative to conventional material like bitumen, filler in the bituminous mix in a flexible pavement structure. This is an effective alternative solution to reduce the growing quantity of E-waste.

Estimation of stressed-deformed state of polymer composite material with hybrid matrix

Properties of polymer composite material consisting of carbon fabric and two matrix types (epoxy and organic-silicon) have been studied. The main purpose of the organic-silicon matrix is to relax stresses arising in carbon-filled plastic components under loads and to decelerate (or stop) crack growth. The structure of the composite material was determined by using a tomography. On the basis of the structure, a finite-element model was developed and a calculation of the stressed-deformed state depending on elastic characteristics of the matrix was performed. A safety factor calculation was made. It was found out that the addition of organic-silicon material in the composite composition made possible to decrease stress values in the crack tip that considerably increased the service life of such materials.