Let’s Get Nerdy for a Moment
I googled my name a while ago. Why? Wala lang, gusto ko lang. Anyway, I found this write-up about my college thesis way back in 2005. My co-adviser gave the interview.
Here it is in full. I will post the link of the source at the end of the article.
Super fine industrial materials from discarded CDs
What keeps off-the-shelf food safe, mobile phone housing sturdy, and even computer hardware durable may have actually come from used CDs.
When CDs and CD-R outlive their usefulness, it’s not the end of the optical road for these cool media doodads. These could be recycled to recover the polymer or plastic content for other creative uses instead of dumping them in landfills. The recycled polycarbonate can be mixed with clay to make a polymer-clay nanocomposite system, a super fine material that has many industrial applications. The materials are compressed to form into sheets.
“These materials do not go back to CDs but are used in making housings for computers, mobile phones, refrigerators, and for food packaging containers”, Dr. Blessie Basilia of the Department of Science and Technology said.
The nanocomposite came out of a study done by Basilia, a senior science research specialist at the DOST’s Industrial Technology Development Institute, and Edna L. Desabelle of the University of the Philippines Diliman’s College of Engineering.
Basilia and Desabelle studied to recover polycarbonate recyclates from these wastes and to produce economic value.
Their study was undertaken in the light of the recycled polycarbonate nanocomposites’ extensive potential applications in automobile (bumpers, interior and exterior panels), construction (wall panels), electronics and electrical (printed circuits, electric components, housings for computers, mobile phones, electrical chargers, etc.), food packaging (containers), aviation (integrated circuit box, panel, etc) and, in communication systems (connection panel, switchboard, integrated block of programmed telephone interchange equipment).
Polycarbonate is a type of plastic with a high melting point (called thermoplastic) that is usually used for engineering purposes. It is tough and durable, and its high melting point properties make it heat-resistant and not easily deformed.
It has other excellent properties like visual clarity, toughness, size/range and thermal stability, which make it an ideal material in the manufacture of compact discs, riot shields, packaging materials, glass lenses, films, tools and appliance housings, and printed circuit boards, among others. Polycarbonate is extensively used in the manufacture of optical storage media like compact disc, CD-R, and DVD.
Millions of CDs are scrapped due to defects along with those destroyed due to copyrights and software updates. Post-consumer CD wastes are dumped in landfills, which piles up waste disposal problems elsewhere.
In their study, the researchers developed a product called polymer-layered silicate nanocomposites (PLSN), using polycarbonate recyclates (RPC) from CD wastes as polymer (plastic) matrix and filled with montmorillonite, a local clay mineral. The two materials—polymer and clay—are then mixed or synthesized through in-melt intercalation or filling in using a two-roll mill.
The process involves blending the melted thermoplastic (RPC) with an organoclay to favor polymer-clay interaction. The mixture is then annealed (heated then cooled) at a temperature above the glass transition temperature of the polymer, forming a nanocomposite or super fine material.
In their experiments, the researchers used a combination of waste audio, video, and rejected CD-R. They used local clay or montmorillonite taken from the natural deposits of Bo. Humapon, Legaspi City in Bicol and treated with dialkyldimethyl ammonium chloride or C22, a technical grade quaternary ammonium salt. An imported organoclay dubbed “FLUKA” from Switzerland was also used in the comparative studies.
The challenge in recovering the polycarbonates from used CDs is the removal of top coatings such as metal aluminum coating, the lacquer and acrylic coatings. Two major processes are involved—mechanical abrasion and chemical washing. Mechanical abrasion is worked out using electric sander and a 120 grit silicon carbide abrasive paper. After sanding, chemical washing with technical grade sodium hydroxide solution (NaOH) is done to remove residual coatings.
The washing process was patterned after the chemical stripping process done in the Bayer recycling plant in Dormagen, Germany .
Meanwhile, comparative studies on the use of local and imported clays in the development of nanocomposites such as RPC and montmorillonite, RPC and FLUKA revealed promising results. The nanocomposite with the local clay has higher tensile strength, exhibiting a 95% increase at 5% local clay addition, compared to only 76% for RPC with 5% FLUKA.
The local clay also has higher resistance to impact loading than the imported clay. These results indicate that the local clay is more compatible with RPC. Generally, the local clay improves the mechanical properties of the PLSN, increasing its barrier properties to moisture, solvents, chemical vapors, gases (such as oxygen), and flavors.
“This means that if the developed nanocomposite is used as a packaging material for food, for example, moisture or other flavors can not easily penetrate that help maintain the quality of the food product and prolong its shelf-life,” Dr. Basilia explained.
In the Philippines , demand for polycarbonate resins and related products like CDs continue to grow. About 900 tons of CDs approximately valued at US$6 million had been imported in 2004. An average import increase of 43 percent was recorded since 2001.
Last year alone, some 6.8 million tons of polycarbonates were imported in different forms [primary form (cellular), non-cellular (plates, sheet, film, foil & strip), and CDs]. Of these volume, 13 per cent are CDs or 38.11 per cent of the total cost of US$15.8 million. Despite the increasing trend in demand, CD recycling has never been done locally.
Several technologies and innovations on nanocomposite materials have already been recorded worldwide, but none has used Philippine montmorillonite. The country has numerous deposits of this material that are still untapped.
Basilia hopes that their study “will trigger interest on this material and find its application in many industries that will boost the local mining industry and help create employment.” She is also hopeful that the technology will spur the recycling of CDs for the polycarbonates that could help in the management of waste materials.