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All Journal Jurnal Matematika UNAND Analit: Analytical And Environmental Chemistry
Vitri Aprilla Handayani
Batam Institute of Technology
Computer Science & IT Mathematics

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THE EFFECT OF VARIATION IN POLYPROPYLENE CONCENTRATION ADDED TO GONGGONG (Laevistrombus Canarium) SHELL POWDER COMPOSITE MATERIAL ON TENSILE STRENGTH CHARACATERISTICS AS A FILLER Sari Rahmiati; Taufiq Rahman; Vitri Aprilla Handayani; Mulyono; Putriana Carona Manurung
Analit : Analytical and Environmental Chemistry Vol. 10, No. 02 October (2025) Analit : Analytical and Environmental Chemistry
Publisher : Jurusan Kimia FMIPA Universitas Lampung

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.23960/analit.v10i02.234

Abstract

The utilization of shell waste is often suboptimal, despite its potential as a composite filler material. This study aims to develop an environmentally friendly composite material based on gonggong shell powder combined with polypropylene. The research method involved the preparation of composite samples by mixing gonggong shell powder and polypropylene at various concentrations, followed by specimen fabrication using the hot press molding method. The resulting specimens were mechanically characterized through tensile testing based on the ASTM D638 standard, and the data were statistically analyzed using ANOVA to determine the significance of differences among composition variations. The research stages included observation, shell waste collection, cleaning, sterilization using NaOH solution, drying, grinding, and sieving to obtain fine powder. XRF analysis showed that gonggong shells are predominantly composed of calcium oxide (65.108%), indicating a high calcium carbonate content and strong potential as a composite filler. Tensile test results for specimens with polypropylene variations of 2.5%, 5%, 7.5%, and 10% revealed statistically significant differences (p < 0.05), with the optimal tensile strength of 35.03 MPa achieved at 5% concentration. These findings demonstrate that the developed composite material based on gonggong shell powder and polypropylene has strong potential as an environmentally friendly filler material with competitive mechanical properties.
Identifying Leading Hazards in Riau Islands: A Monthly Markov Chain Analysis of Disaster Dominance Patterns Nahrul Hayati; Eko Sulistyono; Andini Setyo Anggraeni; Vitri Aprilla Handayani; Sabarinsyah; Laras Devikaduri
Jurnal Matematika UNAND Vol. 15 No. 3 (2026)
Publisher : Departemen Matematika dan Sains Data FMIPA Universitas Andalas Padang

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.25077/jmua.15.3.436-448.2026

Abstract

This study analyzes disaster dominance patterns in the Riau Islands using a monthly Markov chain model with five states: non hazard (S0), hydrological (S1,flood), geomorphological (S2,landslide), meteorological (S3,extreme weather), and ecological (S4,wildfire) hazard. Based on 2019-2024 data from Indonesia’s National Disaster Management Agency (BNPB), the research quantifies transition probabilities between hazard states and computes steady-state distributions to identify long-term risks. Key findings reveal wildfires dominate the system with 40.6% steady-state probability and high persistence (63% monthly recurrence), reflecting the region’s dry-seasonal vulnerability. Extreme weather and floods show significant but secondary prevalence (24.1% and 12.5%, respectively). Landslides are rare (2.5%) but often escalate to wildfires. The transition matrix highlights wildfire transitions following floods (44.5% probability), suggesting delayed risk cascades. Methodologically, this study advances archipelagic hazard modeling by integrating monthly timesteps and hazard taxonomy, offering granular insights for policymakers. Practical implications include prioritizing peatland restoration, flood-resistant infrastructure, and ASEAN-wide early warning systems to address transboundary haze.
Co-Authors Andini Setyo Anggraeni Eko Sulistyono Laras Devikaduri Mulyono Nahrul Hayati Putriana Carona Manurung Sabarinsyah Sari Rahmiati Taufiq Rahman