Testing and quality control of foam rubber

Foam rubber is a consumer product. Therefore various national standards organizations have taken steps to ensure the production and marketing of good quality foam rubber . Important properties tested for quality control and their specification limits are given in that follow.

• Indentation hardness index

• It is the load in kilograms required to give an indentation  in the sample equivalent to 40% of the original thickness of the sample under specified condition. It is a measure of the load bearing capacity of the foam rubber. Foam rubber product are graded by indentation hardness such as Code A has 7-14 indentation hardness.

• Compression set

• It is a measure of state of cure of the foam rubber . The test consists of compressong the test piece under specified condition of time, temperature and constant deflation and noting the effect on the height of the released test sample.The compression set of the sample when determined by the first method shall not exceed 15% and by the second method shall noe exceed 5%

• The color of latex foam rubber shall be as agreed between the purchaser and supplier.
• Flexing test that involves submitting the whole sample to a continuous flexing with an indenter for 2,500,000 cycles at 4 Hz and measuring the loss in hardness and thickness.
• Aging test 

• The test sample of aging test is kept in an oven at 70 +/- 1 *C for 168 hr. Upon removal from the oven after 10 hr, the hardness is measured. The hardness of the test sample after aging shall not vary by more than +/- 20% of the value obthained with the unaged test sample.

• Metallic Impurities

• The copper and manganese content in the test sample shall not be more than 0.001 and 0.005% respectively.

How to used a waste rubber?

Regenerated rubber is often popularly known as reclaim rubber in the tires and rubber industry. This is becoming more and more popular with the increase in natural rubber and synthetic rubber prices. Regenerated rubber is a product obtained from waste and worn out vulcanized scrap. Use of reclaim rubber is already established in automotive tires, butyl tube. Energy recovery is one of the important processes of tires reclaim. Tires (once the steel wire is removed) have a relatively high specific heat value, as compare to coal. Worldwide energy recovery makes up one of the largest uses of reclaim tires. Test suggests that the use of waste tires as a substitute for coal result in lower emissions of nitrogen and sulfur. There has been a significant amount of reclaim tires used in cement kilns.

The rubber industry worldwide has focused mainly on the disposal of waste rubber rather than recapturing the economic value of the resources incorporated in the waste, historically the uses for waste rubber have been of low economic value, resulting in a low volume of recycling and stockpiling of tires. Tires are consider as the most visible of waste rubber product and their accumulation is increasing at an alarming rate worldwide.

There is an enormous potential for reclaim and reuse of rubber in developing countries. Whether rubber tires are reused, reprocessed, or used for making article for human use, the end result is there is less waste and less degradation of these materials which could cause harmful effects in our environment.

In Asian countries there has been a culture to reuse and to recycle all materials. Other than making reclaim rubber, scrap tires parts have also been used in shoe soles, slippers and in washers. Worn out tread have been nicely stripped off and used on the wheel of bull carts. Sidewalls of a tires are stripped off and knitted nicely with steel wire to make mats, mattresses and flooring products. Worn out bladders have been used in making flower garden and so on.

There is tremendous potential for the application of rubber crumb (powder rubber) in the construction of road. Crumb rubber may be used as : Fill material , In asphalt(wet and dry), As a crack sealant and in repair membranes.

What is rubber roll?

The application of rubber to the surface of metal cores to make rubber covered rolls generally referred to as rubber roll. The function of rubber roll in various application are diverse, demanding different properties from the rubber that is used. One of the the most extensive uses of rubber roll is in the control liquids by pressing or squeezing, as exemplified in the manufacture of paper and in the processing of metal, textiles, plastics, and leather. Such typical device as the press roll, the touch roll, the padding roll and the transfering roll.

Rubber roll are used for many conveying purposes such as feed rools and guide rools of various kinds, as used in the paper steel textile and plastic industries. The properties of rubber that are important for such application include elasticity, friction abrasion resistance and chemical resistance . In advantage resistance to solvents and plasticizer as well as resistance to heat are desired in application such as laminating, embrossing and coating.

The design of rubber roll involves considering of general factor such as the work place, the working condition, the desire performance and the required durability. The core is designed on factors such as the load, the speed and the the required precision. The core may be built the seamless, welded or cast pipe and may be made from mild steel, cast iron, stainless steel etc. It is almost possible to vulcanize soft rubber satisfactorily to the cast iron core because during vulcanization heat drives gases out the porous iron causing blisters in the covering and resulting in early service failure. To overcome this problem a layer of ebonite is applied to the core and before the soft rubber cover.