Natural Rubber-Based Encapsulation for Wireless Intraruminal Monitoring: Effects of Latex Processing Parameters on Mechanical, Chemical, and RF Transmission Performance

Abstract

Encapsulation for wireless dairy-cattle implants must resist acidic, moisture-rich gastrointestinal conditions while remaining transparent to radio-frequency (RF) signals. This study evaluated vulcanized natural rubber (NR) latex as an intraruminal encapsulant, examining how total solid content (TSC; 30, 40, 50 wt%), stirring duration (24–72 h), and TiO2 loading affect tensile and tear strength, acidic swelling, dip-coating thickness, and received signal strength indicator (RSSI) at 433 MHz. Multilayer dip-coating produced films 0.25–0.38 mm thick. Tensile strength rose with TSC and stirring (26.6 → 32.2 MPa), whereas tear strength peaked at 40 wt% (31.97 N mm−1). Adding 5 phr (parts per hundred rubber) TiO2 cut pH-4 swelling ~four-fold (21.1 → 5.25%) with a negligible RSSI penalty, and 3–5 coating layers kept the link well above the −120 dBm sensitivity floor over 5–55 m. The optimum—40 wt% TSC, 72 h stirring, 5 phr TiO2—best balanced mechanical integrity, swelling resistance, thickness, and wireless performance. Vulcanized NR is therefore a promising bio-based encapsulant under simulated conditions; dielectric characterization, long-term aging, and in vivo validation remain future work.