What is EPS
What is foam?
"Foam" is generally known everywhere but in fact its' meaning is so wide. According to translation "Foam" means, "expand" or "blow".
Herewith we concern "Foam" as the expanded plastics. There are many kinds of plastics in the world, any plastics when react with the Blowing Agent will become "Foam" which generally called "Foam Plastics".
The example of well -known foam plastics is sponge, food box, foam sheet, spray foam for insulation and etc. These foam plastics are produced from different kinds of plastics.
We will only mention about foam that produced from Polystyrene / PS (C8H8) plastic. PS Foam or so-called "Expanded Polystyrene" are made for food box, ice box, packaging for television and floating Krathong foam.
There are two kinds of Polystyrene Foams:
1. Expandable Polystyrene / EPS usually use as packaging for many kind of products such as television, electrical appliances, helmet, ice box, sheet foam and block foam for road construction.
2. Polystyrene Paper / PSP so called Extruded Polystyrene / XPS which use to produce food tray and food box.
How to produce foam?
1.1 Shape molding machine that produce various shapes of foam products according to the molds such as icebox, helmet and packaging foam.
1.2 Block molding machine that produce block foam and sheet foam Expanded EPS foam bead contains 98% air per volume, only 2% is plastic. This make EPS foam very light weight, has low thermal conductivity because air is the best insulation, high compressive strength and excellent shock absorption. These properties make EPS to be ideal material for packaging and construction.
2. Polystyrene Paper (PSP) is a PS Foam which produced by extruding process as another plastic. Production process start when put polystyrene resin pellets into the extruder that heated by electric. Foaming process occur at the end of extruder where the blowing agent, butane (C4H10) gas react with the melt plastic then become foam. The melted polystyrene foam then extended as sheet then roll as paper roll, that is why commonly known as "Polystyrene Paper". The polystyrene foam sheet or polystyrene paper can be produced as many shape according to the mold by thermal forming process such as food tray, cups, bow, and food box.
There's no any CFC's in PS foam
Both EPS and PSP contain 95 -98 % air another 2-5% is polystyrene which is pure hydrocarbon. CFC's is Chlorofluorocarbons which is totally different chemical structure from polystyrene. CFC's has very low blowing point and uneasy to be maintained in EPS beads. Therefore, EPS Foam never use CFC's at any stage of its production. The blowing agent used since EPS Foam was first introduced in 1952 by BASF of Germany is Pentane gas which, does not contain any chlorine atoms as CFC's. PSP Foam in the beginning used CFC's as blowing agent. In the past two decades CFC's are gradually phased out from plastics and refrigerator industries. PSP molders in Thailand already use Butane (C4H10) as the blowing agent since the last 15 years. Butane gas is the gas that we use at home for cooking. The blowing agents that use in producing PS Foam are Pentane and Butane, which are pure hydrocarbon as polystyrene. They belong to the same chemical family, the paraffin series as methane, ethane, and propane gas.
How to manage the EPS foam waste
Apart from recycling by melting and compacting, there are many ways to manage the EPS waste as the followings:
1. Crush in to small particle and mix with soil. Foam waste will improve ventilation in the soil, organic substances in the soil will become easier the humus.
2. Mixing the crushed bead with cement to reduce the weight and increase insulation properties.
3. Combustion at 1000 C with sufficient air supplies in to generate heat. Burning EPS require no any additional fuel, in fact EPS can replace the fuel normally required for combustion, l kg of EPS saves 1 kg = 1.2 - 1.4 Litre of fuel oil.
The Recycling of PSSince both EPS and PSP Foam are made of Polystyrene, which is thermoplastic, so that it will become again a polystyrene plastic when recycled. We recycle both EPS and PSP Foam by first crushing into small particle then melting or compacting it. Melting can be done by heated roller, disk or screw extruders, where the regrind scraps is heated usually by electrical power for some time above the melting temperature. Compacting can be done by rotary compactors where pressure and frictional force create heat below melting temperature to soften the regrind scraps for only few seconds. This method also called "agglomeration".
PSP waste is average not over 20% of production capacity or 300 tons per month (since the production process are different, the waste between EPS and PSP are not equal). Not only foam manufactures who recycle foam, but also the waste processors who buy the foam scraps from molders to recycle as PS plastics.
Moreover, EPS is bulky but lightweight therefore it creates higher transportation cost than other plastics.
Nowadays, our group keeps trying to educate and promote correct facts about PS foam to public. We also now trying to make the compactor to reduce the volume of PS foam in order to create economic possibility to collect and transport foam waste for recycle
Later on, when country's industrial sectors expand, shape molding of EPS for packaging for export products then started in 70's. Until nowadays, EPS foam is also using in building and road construction.
There are 5 EPS materials producers and about 25 EPS molders most of them locate in Bangkok and nearby area. Monthly production capability is round 2,800 -3,000 tons mostly for packaging. PSP have started since 15 years ago, there are 5 materials makers (PS plastic) and 5 PSP Molders which only one who are not located in Bangkok. Total capability of PSP is about 1300-1500 tons per month. PSP is produced for food box and tray for domestic and export market.