Standard Thai Rubber (STR) is a primary natural rubber product produced in Thailand through a process that involves chopping, grinding, and shredding various forms of natural rubber such as cup lump rubber, crepe rubber, scrap rolled rubber sheets, and other natural rubber scraps, which are then combined into a uniform substance. It is a form of technically specified rubber (TSR) used extensively in industries like tire manufacturing, automotive components, gloves, and construction materials

​STR is categorized into several grades based on quality and physical characteristics, including STR10, STR20, STR5L, STR XL, and CV grades (e.g., CV60). These grades differ in purity, elasticity, strength, and impurity content, catering to different industrial applications. For example, STR20 is a widely traded grade known for its strength and durability, mainly used in tire production, while STR5L is valued for its low impurity content and high elasticity, suitable for medical products like glove.

​The production of STR involves controlled quality processes, including laboratory testing to ensure consistency and meet specific standards. The rubber is typically packed in bales weighing around 33.33 to 35 kg for ease of handling and transportation.

Thailand’s STR is recognized internationally and compared to similar standards in other countries, such as Standard Indonesia Rubber (SIR) and Standard Malaysia Rubber (SMR)

Standard Thai Rubber (STR) grades such as STR3L, STR5L, and CV grades refer to specific classifications of natural rubber based on quality parameters like dirt content, ash content, nitrogen, volatile matter, plasticity, colour, and viscosity.

STR5L is a high-quality grade of STR characterized by low dirt (max 0.04% wt), low ash content (max 0.40% wt), nitrogen max 0.60%, and volatile matter max 0.80%. It is processed from quality latex and dried at higher temperatures (around 100°C), resulting in a light color rubber with good uniformity and elasticity. STR5L is widely produced in Thailand and is favored for applications requiring higher purity and elasticity, such as medical gloves and fine rubber products.

STR5 has slightly higher ash content (max 0.60% wt) but similar limits on dirt and nitrogen. It is a common grade used in general rubber products.

CV Grades CV stands for "Concentrated Vulcanizable" or sometimes "Concentrated Vacuum" grades, which are controlled for dirt and ash content to meet specific industrial requirements. CV grades are often used in tire manufacturing and other applications where consistent vulcanization properties are critical

STR3L is less commonly referenced but generally refers to a grade with slightly different parameters, often related to the ribbed smoked sheet (RSS) grading system. It is a standard quality grade used in Thailand and comparable to TSR grades. It has slightly higher dirt and ash limits compared to STR5L, making it suitable for general industrial use but not for high-purity applications.

Concentrated latex is a processed form of natural rubber latex derived from field latex collected from rubber trees. It typically has a dry rubber content (DRC) of about 60%, meaning the rubber solids make up roughly 60% of the total weight, with the rest being water and other components

How Concentrated Latex is Made

• Collection: Raw latex is collected by tapping rubber trees.
• Preservation: Ammonia or other preservatives are added to prevent coagulation and maintain latex stability.
• Centrifugation: The latex is centrifuged to remove excess water and impurities, increasing the dry rubber content to around 60%

Characteristics

• Concentrated latex is a clean, uniform, and stable liquid form of natural rubber.
• The ammonia level can be adjusted based on customer or processing requirements.
• It is preserved to maintain colloidal stability for longer storage and transport.

Applications

Concentrated latex is widely used as a raw material in manufacturing various dipped rubber products, such as:

• Medical and examination gloves
• Condoms
• Baby pacifiers
• Elastic bands
• Adhesives
• Foam products like mattresses and cushions

Standards

There are international standards (e.g., ISO 2004,EUDR or FSC ) specifying the quality and preservation methods for natural rubber latex concentrate, including types preserved with ammonia and other chemicals

Ribbed Smoked Sheets (RSS) are natural rubber sheets processed from coagulated field latex and classified into five main grades—RSS1, RSS2, RSS3, RSS4, and RSS5—based on factors such as purity, elasticity, color, cleanliness, and tear strength.

RSS3 is considered a medium-to-high grade sheet. It is one of the preferred raw materials for manufacturing radial tires and is used in medical, pharmaceutical, and engineering products as well as in general rubber goods. It offers a good balance of purity and elasticity, making it suitable for a wide range of applications.

RSS4 is a lower grade compared to RSS3 but still widely used in tire manufacturing, especially for automobile tires and retreading materials. It has slightly higher impurity levels and lower elasticity than RSS3 but remains suitable for many industrial applications.

RSS5 is the lowest grade among these three and generally used for more general-purpose rubber products where high purity and elasticity are less critical. It has higher levels of impurities and lower overall quality compared to RSS3 and RSS4.

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