Tensile Strength is the ability of materials to resist breaking under tensile. By tensile testing, you will know that how “strong” of a material really is. It is an important mechanical property when talking about polymers, fibers, rubber, metals, and etc. It is usually considered as ultimate tensile strength or tensile strength at break and with units Newton per area(mm or inch). 
Basically, all the tensile testing machines do not vary significantly. According to different standards and different test specimens, they have some differences in max load, accuracy, grips, force sensors and other aspects. When you want to do tensile testing for metal specimen, the max load should be huge and maybe it doesn’t need a very high accuracy. But if you what to do a tensile testing on a thin film, maybe 5N is enough.
Labthink is right the manufacturer of the tensile testers professionally for small-force-materials, such as polymers,paper, sheeting, single fibers.
Talking about tensile, there is another definition should be discussed together – Elongation, which is just the length the polymer sample is after it is stretched (L), divided by the original length of the sample (L0), and then multiplied by 100.
[( LT-L0)/LT ]x100=%Elongation
Here we mainly talk about the flexible plastic tensile testing and elongation rate. Flexible plastics like polyethylene and polypropylene are different from rigid plastics in that they don't resist deformation as well,but they tend not to break. Of course, the ability to deform is what keeps them from breaking. Initial modulus is high, that is it will resist deformation forawhile, but if enough stress is put on a flexible plastic, it will eventually deform. You can try this at home with a piece of a plastic bag. If you try to stretch it, it will be very hard at first, but once you've stretched it far enough it will give way and stretch easily. The bottom line is that flexible plastics may not be as strong as rigid ones, but they are a lot tougher.
International Test Standards for Small-force-materials (flexible plastics, adhesives) -- Tensile & Elongation Test
The analogous test to measure tensile properties in the ISO system is ISO 527. The values reported in the ASTM D638 and ISO 527 tests in general do not vary significantly and either test will provide good results early in the material selection process. Separate tensile test methods are commonly applied to polymer films (ASTM D882) and elastomers (ASTM D412)
- ASTM D638 -- Standard Test Method forTensile Properties of Plastics
- ASTM-D412 -- StandardTest Methods for Vulcanized Rubber and Thermoplastic Elastomers—Tension
- ASTMD882 -- Standard Test Method for Tensile Properties of Thin Plastic Sheeting
- ASTM-D5034-09 -- StandardTest Method for Breaking Strength and Elongation of Textile Fabrics (Grab Test)
- ASTM-D5035 -- StandardTest Method for Breaking Force and Elongation of Textile Fabric
- ASTM-D7269 -- StandardTest Methods for Tensile Testing of Aramid Yarns
- ASTM-D751 -- StandardTest Methods for Coated Fabrics
- BSEN ISO-527-1 -- Plastics. Determination of tensile properties. Generalprinciples
- BSEN-455-2 -- Medical gloves for single use. Requirements and testingfor physical properties
- BSEN ISO-13934-1 -- Textiles. Tensile properties of fabrics.Determination of maximum force and elongation at maximum force using the stripmethod
- BSEN ISO-2062 -- Textiles. Yarns from packages. Determination ofsingle-end breaking force and elongation at break using constant rate ofextension (CRE) tester
- ISO-1421-- Rubber- or plastics-coated fabrics - Determination of tensile strength andelongation at break.
- ISO-37 -- Rubber,vulcanized or thermoplastic - Determination of tensile stress-strain properties
- ISO-3781 -- Paperand board -- Determination of tensile strength after immersion in water
- ISO-9073-- Textiles - Test methods for nonwovens-Determination of tensile strengthand elongation
- ISO-12625-5 -- Tissuepaper and tissue products - Part 5: Determination of wet tensile strength
- BSEN ISO-527-1 -- Plastics. Determination of tensile properties.General principles
- TAPPI-T456 -- Wet tensile breaking strength of paper and paperboard
See Labthink’s range of tensile testers.