Rubber

Rubber

This is an exert from a report on resilients done by a group of students including myself at the Ryerson School of Interior Design. For more information see cork, resilients, linoleum and vinyl

Origin and History

South American ancestors of the Olmec and Mayans first used rubber for ball games in public courts. Later generations discovered rubber’s waterproofing properties and applied this knowledge in making shoes, bottles, and other necessities. In the early 1600s this knowledge was passed on to Spanish Conquistadors who then excited the rest of Europe with this mysterious milky tree sap called latex. Transporting latex from the initial tapping of the trees, and across the Atlantic to Europe was difficult because of its solidification. In the United Kingdom, rubber was discovered to be great for erasing pencil markings, hence the name ‘rubber’. Until the great rubber boom, rubber was used for catheters, hoses, shoes, gloves, inflatable cushions, elastic bands, and helium balloons.

In 1839, Charles Goodyear accidently created the vulcanization process by leaving a solution of rubber, sulfur, and white lead on a stove. The transformed material was no longer defective. It didn’t soften when heated or harden when cooled and was no longer sticky. Rubber supply increased because of the spread of rubber plantations to the more climatically suitable South East Asia. Due to the increased supply and mass industrialization, rubber became a driving force in the Industrial Revolution culminating in the invention of the automobile. Increased popularity of motor vehicles created more demand for rubber and the plantations could not keep up with demand. To combat soaring rubber prices, synthetic rubber was invented in various private labs. Only until the advent of World War Two where Axis nations controlled rubber plantations in Southeast Asia did mass production of synthetic rubber begin in Allied nations. After the war, synthetic rubber replaced natural rubber in many of its applications.

Harvesting and Manufacturing

Plantations in Thailand, Indonesia, Malaysia, India, Vietnam, and China supply 90% of the world’s natural rubber^[1]. The tapping process where tappers collect the latex of various rubber tree species is somewhat different from the maple tree tapping North Americans are accustomed to. Rubber trees cannot be tapped until they are at least 50cm in circumference, which is 5 years after its initial planting. Tree tapping is a labour intensive process where tappers gouge a shallow channel around the tree using a spiraled straightedge, making sure not to damage the core of the tree. A gutter and cup is then hung below the channel to collect the latex. Each tree produces about half a cup of latex per day. The time of day and day of the week to tap is very important in collecting the optimum amount of latex and ensuring the trees stay healthy. One tree should provide sap for only 28 years and it is advised to start a new plantation afterwards^[2].

After the tapping process, the latex is mixed with an acid, such as formic acid. Once the solution is coagulated it is then put through a rolling press to remove excess water and left to dry. The natural rubber is then ready to be exported for further processing and possible vulcanization^[3]. Vulcanization involves heating the rubber with an amount of sulfur 10% the weight of the rubber. The sulfur alters the cross-linking of the rubber molecules, making it 10 times stronger and more elastic. Adding too much sulfur will cause the rubber to form ebonite, a fragile and inelastic material^[4].

To create styrene-butadiene, the most common synthetic rubber, petroleum needs to be distilled. One chemical in petroleum has a lower boiling point and will become a gas first. The other chemical has a high boiling point and will remain a liquid. When subjected to specific chemical reactions, the chemicals will form styrene and butadiene, which are then mixed together with a catalyst. The catalyst helps form rubber particles. Stabilizers, modifiers, and a coagulant are then added. Lastly the solution undergoes the same vulcanization process as natural rubber^[5].

Cultural Significance

The harvesting and exportation of rubber makes up a large percentage of the Asian economy because of the highly suitable southern tropical climate^[6]. To the Southeast Asian people, rubber is essentially a means of living. However, most people recognize rubber for its durability, elasticity, and resilience which consequently are more apparent in synthetic rubber. With the introduction of synthetic rubber, natural rubber’s number of applications is multiplied. Synthetic rubber is recognized for having a larger range of flexibility and density than natural rubber^[7].

Properties, Installation and Maintenance

Rubber used as flooring is acoustically good for absorbing sound, slip resistant, resistant to heavy impact, and is resistant to minor burns and chemical spills. It has a homogeneous construction, consistent colour, is environmentally friendly, recyclable, and low maintenance.96 Recycled rubber is more durable than synthetic or virgin rubber.

To install rubber flooring, the subfloor needs to have no more than 3% moisture content. Use a hydrometer to measure if necessary. Make sure the subfloor is dry, clean, and level. Sand any minor elevations until level and patch any cracks or depressions. Adhesives should be low-VOCs and there must be adequate ventilation when working with adhesives. Rubber tiles should be installed in the center of the room and continue outwards to the walls, trimming where necessary^[8]. Rubber flooring rolls can be started in the center of rooms or against walls, leaving excess at the ends for later trimming after the gradual adhesion process^[9]. High quality double-sided flooring tape can be used in smaller rooms but adhesive is recommended for larger commercial settings. There are also more temporary varieties of rubber flooring made of tiles with interlocking joints or dowels that don’t require adhesives^[10].

For regular cleaning of rubber flooring, swep or wipe away any dirt, then mop using a neutral cleaning solution mixed with water. For annual cleaning repeat this procedure followed by scrubbing from a single disk-scrubbing machine. Then remove cleaning solution with a wet mop and allow to dry^[11].

Interior Uses

Synthetic and natural rubbers are commonly used for interior flooring because of their broad range of properties. Almost all synthetic rubbers can be used as a base for adhesives. Styrene-butadiene is the most popular and is used in water-based latex paint, stair nosing, wall bases, and more^[12].

Another synthetic rubber called butadiene is used as a plasticizer, coating, ink, or sealant. Chloroprene is highly resistant to fire and can be used as upholstery foam, or acoustic paneling.^[13]. Nitrile butadiene can be formed into synthetic leather and is used for wire and cable jacketing, gaskets, and weather stripping. Butyl and silicone rubber can be used as caulking^[14]. Much research has shown that silicone is a suitable home insulator because of its flame retardant and chemical resistant properties^[15].

Due to rubber’s resilience and malleability, it can be bent and curved to make more organic shapes. It can transform a basic staircase into piece of art, for example, Longchamp Store in New York, by Heatherwick Studios^[16].

Ecological Footprint

Natural rubber is a sustainable, renewable material because it is harvested from trees. Much of this rubber’s environmental impact is primarily attributed to the transportation of raw materials to the factory and the vulcanization process, which requires large amounts of heat, during production ^[17].

Synthetic rubber is not a sustainable material. Derived from petroleum, which is a by-product of crude oil, synthetic rubber requires the use of a finite resource which proves costly for the environment ^[18]. While natural rubber does have minor off-gassing it does not release harmful chemicals into the atmosphere, only a slight odour. Synthetic rubber adhesives are more likely to carry volatile organic compounds (VOCs) which are released into the air during the drying process ^[19].

The biggest contributors to environmental waste are automotive and bicycle tires, both which are made from synthetic rubber. The United States alone produces 290 million used tires a year^[20]. Each year, over 27 million of these tires are not recycled and end up in landfills. There are many recycling opportunities which can divert used tires from landfills. Shredding the rubber tires in order to produce new products is one of the most popular forms of synthetic rubber recycling^[21]. Shredded rubber has been used for the perimeters of lawn bowling greens, enhancing turf grass on sports fields, high traffic public places as well as recreational spaces^[22].

People are also realizing the versatility of recycled rubber. In 1999, artist Noel Harding created the art installation, “Elevated Wetlands”. Comprised of 5,000 pounds of shredded recycled rubber, the functional sculptures are located in the Taylor Creek Park next to the Don River ^[23].

Size and Costs

Rubber rolls are typically 6mm to 8mm thick and 4’ by 25’ or 4’ by 50’^[24]. All rubber tiles (normal, interlocking, and dowel) come in a variety of textures and usually have varying thicknesses depending on uses and are 12” by 12” or 24” by 24”^[25]. For more information see Appendix 5.

It is evident in Appendix 4 that rubber is significantly less money to install per square foot and also to keep clean for 15 years. It’s life cycle cost (which is a multiple of the initial cost) is a factor of 2116, making it the lowest out of the 5 flooring materials.

For the consumer, the cost of rubber is the amount paid to the producer, the price of ocean freight, financing, insurance, markup, overheads, and a number of other factors. If the company is well managed, most of these costs can be negotiated and minimized^[26].

Rubber rolls range in price from about $1.25 per square foot to around $4.00 per square foot in a variety of thicknesses. Rubber interlocking tiles range in price from $41.00 - $95.00 depending on dimensions, color and quality^[27].

Recycle

After vulcanization, natural rubber will not decompose as other sustainable materials would. Vulcanized rubber can only be recycled into new composite rubber materials and is considered much stronger than virgin rubber. Recycling reduces the need to harvest more latex. The same can be said for synthetic rubbers. Recycling is a better alternative than extracting new petroleum from oil^[28].

There's a tire recycling program called "The Ontario Tire Stewardship". This program help ensure that tires are being properly recycle and not being thrown out illegally. The used tires are being recycle and being given a new life into something else, that we use in our daily lives. ^[29]