Journal Boliviano de Ciencias

Tensile and Impact Properties of Mechanically Recycled Polypropylene: A Structured Literature Review

Roger Alejandro Del Barco Valdivia — 2025-06-30

This literature review aimed to analyze the mechanical and thermal behavior of recycled polypropylene (PP), with a specific focus on tensile and impact performance. A structured search was conducted using Google Scholar, selecting eight scientific articles published between 2017 and 2025 that met inclusion criteria such as full-text availability, focus on mechanical recycling, and reporting of key mechanical properties. The selected studies were analyzed and compared based on material composition, additive use, and number of recycling cycles. The results showed that tensile strength was generally retained, with minimal reduction in some cases, especially when fillers such as talc were used. However, impact resistance decreased significantly with increasing recycled content, particularly in the absence of elastomeric modifiers. Differences in feedstock origin, test protocols, and additive strategies were identified as key sources of variability. Despite these challenges, promising approaches were found, including the use of tailored additive systems, closed-loop recycling strategies, and advances in preprocessing technologies. It is concluded that recycled PP can be a technically viable material for various applications, particularly when combined with targeted additives and supported by standardized characterization methods.

Automated composting monitoring and control based on Raspberry pi microcontrollers, gas, temperature, pH, humidity sensors and development boards

Wilson Veizaga Balta — 2025-06-30

This article presents a comprehensive literature review on the current state of automated monitoring and control in composting processes, with a particular focus on the integration of microcontrollers, gas, temperature, pH, and humidity sensors, as well as development boards. The main objective is to analyze and compare recent studies related to the development of automated composting systems.

The methodology employed consisted of a systematic review of the most recent scientific literature, in which multiple studies that have developed and implemented automated systems for monitoring and controlling composting conditions were analyzed. Various technological approaches were examined to identify trends, benefits, and challenges in the application of these tools.

The research findings showed that the use of controllers enables the continuous collection and processing of critical data, significantly improving the monitoring of key variables in the composting process. The importance of gas sensors—particularly those designed to measure carbon dioxide—was emphasized due to their role in assessing microbial activity and process efficiency. Likewise, temperature and humidity sensors were highlighted for their relevance in maintaining optimal conditions for the decomposition of organic matter. However, gaps in the literature were identified regarding the efficient integration of multiple sensors and the long-term evaluation of their impact on the final quality of the compost.

The conclusions underscore that, although technological advancements have enabled increasingly sophisticated composting automation, there are still challenges to be addressed. Future research is recommended to deepen the integration of multiple monitoring parameters and to analyze their influence on the physicochemical and biological characteristics of the produced compost. This study reaffirms the potential of these technologies to transform composting into a more efficient, controlled, and sustainable process, with relevant applications in both urban waste management and agricultural production.

Comparison of Hinf Robust with mixed sensitivity and LQRy Robust with uncertainty in a quadcopter vehicle

Francisco Triveño Vargas — 2025-06-30

In this article, a comparative study is presented between two controllers intended for the stabilization of a quadcopter. The two controllers under analysis are the Hinf Robust controller with mixed sensitivity and the LQRy Robust controller. Both controllers have been designed taking into account uncertainties of 10\% in the mass and inertias of the quadcopter plant. The primary objective of this research is to discern which of the two control techniques offers optimal performance in the stabilization of the quadcopter to ensure maximum flight stability. To address the challenge of stabilizing the quadcopter, both controllers are designed using the linearized model of this quadcopter. Therefore, given that the quadcopter has a MIMO (Multiple Inputs, Multiple Outputs) configuration and that its study becomes complicated by incorporating uncertainties diagonal in MIMO systems, a simplification was made to SISO (Single Input, Single Output), which facilitates the incorporation of diagonal uncertainties in the quadcopter model. The simulations have been conducted in the MATLAB environment, enabling an analysis of the responses of both controllers. The results obtained indicate that the LQRy controller exhibits superior performance compared to the Hinf controller in stabilizing the quadcopter. These findings suggest that the LQRy approach may be more effective in achieving stable flight under ideal simulation conditions.

Editorial Note

Pablo Arce Maldonado — 2025-06-30

Analysis of Potential Development Scenarios for Bolivia’s Vehicle Fleet and its Greenhouse Gas Emissions using the LEAP Software for the 2020–2030 Period

Sergio Adrián Marañón Rodríguez — 2025-06-30

This study analyzes the contribution of the Bolivian vehicle fleet to greenhouse gas (GHG) emissions for the period 2020-2030, through scenario modeling in the LEAP platform. The vehicle fleet was characterized using a bottom-up methodology, processing the information in consumption, performance and mileage matrices. A base scenario (Business As Usual, BAU) and three alternative scenarios were established: vehicle efficiency, telework and electromobility. The results show that electromobility would allow a 9% reduction in emissions by 2030, efficiency by 4% and telework by 2%. It was found that private vehicles, especially heavy vehicles, are the biggest emitters. This work seeks to serve as technical input for the design of public policies to reduce emissions in the transportation sector.

Development and application of homemade equipment for the mechanical recovery of plastics

Roberto Carlos Berdeja Zambrana — 2025-06-30

The accumulation of plastic waste has reached alarming levels worldwide, and Cochabamba is among the most affected cities in Bolivia. Reports from 2019 and studies by the WWF (World Wildlife Fund) indicate that this city generates more plastic waste than four other departments combined, highlighting the urgent need for effective solutions.

In this context, this study evaluates the functionality of two homemade devices developed at the Research Center for Applied Engineering (CIIA) of the Universidad Privada del Valle: a plastic shredder and an extruder, designed for the mechanical recovery of plastic waste.

The methodology involves operating these devices in a complementary manner. The shredder uses a blade system (one fixed and one mobile), coupled to a 40:1 gear motor with a 1 HP motor, to grind plastics into small fragments. The extruder, in turn, employs a screw inside a barrel heated by electric resistors operating between 0 and 280 °C, producing filaments whose diameter varies depending on the nozzle used. An optional system for winding recycled filaments is also considered.

The resulting products include 3D printing filaments, pellets, and molded boards, derived from shredded and thermally processed materials. This process demonstrates that, with homemade machines, it is possible to reuse various plastics, reduce their environmental impact, and facilitate their storage or transportation when they are not recyclable. In this way, an accessible circular economy is promoted for users interested in manufacturing these devices, and recyclable plastics are prevented from ending up in the Kara Kara landfill in Cochabamba, Bolivia.

Experimental evaluation of the physical-mechanical behavior of fiber cement reinforced with kraft cellulose pulp using the hatschek process

Nahúm Gamalier Cayo Chileno — 2025-06-30

The study of construction materials reinforced with recyclable elements demonstrates positive effects on the promotion of a circular economy and the development of environmentally friendly materials. Under this aspect, the objective of this article is to experimentally evaluate the physical mechanical behavior of fiber cement reinforced with cellulose pulp from kraft cardboard. The methodology of the work focused on the characterization of the materials, the elaboration of test bodies through the techniques adapted for the hatschek process, and the physical-mechanical characterization at 7 and 28 days of age. The results show that a cementitious matrix reinforced with treated cellulose pulp presents a higher percentage of water absorption; as for bulk density, these do not present a statistically significant difference concerning the influence of age and treatment. The mechanical behavior response (MOE and LOP) values indicate that applying untreated cellulose pulp provides a more rigid behavior, contrary to the treated pulp, which presents a slightly higher load resistance at 28 days (MOR).In conclusion, the fiber cement bodies elaborated through the hatschek process and reinforced with 2.5% treated cellulose pulp have a favorable mechanical performance; however, a high percentage of absorption is observed, so it is necessary to carry out more studies to achieve a material applicable within the construction industry.