Bamboo waste makes plastic 173% tougher, blocks unwanted signals in smartphones

Chinese researchers have recently come up with a new bamboo-reinforced plastic that is 81 percent stronger and 173 percent tougher, and could be used to shield electronic devices from unwanted electromagnetic waves.

The breakthrough material was developed by a group of scientists from the Anhui Agricultural University located in Hefei. According to the team the new composite doesn’t primarily reflect electromagnetic waves. In contrast, it absorbs most of the incoming radiation, and reduces secondary interference.

To create the novel composite, the team used bamboo biochar, which is a carbon-rich substance produced by heating bamboo in an oxygen-limited environment. This process is known as pyrolysis.

The researchers are certain that the material could shield smartphones, laptops, and other electronic devices from electromagnetic interference. “By combining electromagnetic protection with mechanical performance in a biochar-based material, the design could guide the development of components for electronic devices and other applications that require durable shielding,” the team said.

How bamboo blocks waves

Electromagnetic interference (EMI) is unwanted noise or interference that disrupts electrical circuits. Typically caused by an external source, it has become a growing concern for electronics manufacturers.

However, traditional conductive shielding materials often reflect incoming waves, and create additional interference. To address this challenge, the scientists turned to bamboo biochar, a carbon-rich material created by heating bamboo biomass with little to no oxygen.

Biochar could reportedly serve as a renewable substitute for standard conductive fillers. Nevertheless, its low conductivity and poor bonding with plastics can limit its performance.

The researchers first heated bamboo powder under nitrogen to produce biochar. They then applied flash Joule heating (also known as ohmic or resistive heating), which uses a brief burst of electrical energy to modify the carbon structure.

They then treated the particles with APTES, a chemical that is used to improve the bonding with plastics. The modified biochar was then inserted between layers of two biodegradable plastics, polylactic acid (PLA) and polybutylene adipate-co-terephthalate (PBAT), therefore creating pathways that could absorb and weaken electromagnetic waves.

Stronger, tougher plastic

For the study, the team compared plastics containing untreated, flash-heated and chemically modified biochar along with a nonlayered version. Lab tests found that the optimized composite achieved a tensile strength of 25.5 megapascals (MPa). Its strength increased by 81 percent.

At the same time, its toughness increased by 173 percent to 2.68 megajoules per cubic meter, while its ability to stretch before breaking more than doubled, rising from 11.5 percent to 24.7 percent. The material also conducted electricity much better. Its conductivity hit 12.8 siemens per centimeter, compared to just 1.7 for the version with untreated biochar.

Further tests found that the material blocked electromagnetic interference, by an average of 36.7 decibels (dB) at frequencies of 8.2 to 12.4 gigahertz (GHz). On the other hand, a nonlayered composite with the same amount of filler achieved just 7.5 decibels.

On top of that most of the shielding came from absorbing electromagnetic waves (30.8 dB), while the reflection accounted for just 5.9 dB. The scientists believe that the carbon network and layers forced the electromagnetic waves to travel longer distances through the plastic.

The study has been published in the journal Sustainable Carbon Materials.

Source: https://interestingengineering.com/science/bamboo-waste-makes-plastic-blocks