Thermoplastic Rubber (TPR) is a synthetic material generally considered soft, though its texture and feel change significantly depending on its specific formulation. TPR is a composite material that blends the elasticity and soft touch of rubber with the manufacturing advantages of plastic. Unlike traditional rubber, which requires complex vulcanization, TPR can be melted and molded like a plastic. This ability to be easily processed and recycled while maintaining a rubber-like feel makes it a popular choice for many consumer goods.
The Variable Softness of Thermoplastic Rubber
The question of whether TPR is soft does not have a single answer because its softness is a deliberately engineered property, not an inherent fixed state. This material is designed to bridge the gap between rigid plastics, which offer structural integrity, and highly elastic, floppy rubbers. Manufacturers can adjust the formulation to produce textures ranging from a soft, gel-like feel to a firm, dense rubber. The resulting texture can be highly pliable and cushiony, or it can be tougher and more resilient, similar to a tire tread. This wide range means the TPR used in a soft toy will feel vastly different from the TPR used in a heavy-duty tool grip.
Measuring Softness: Understanding Shore Hardness
To accurately describe this variable softness, the industry uses a technical measurement known as Shore Hardness, specifically the Shore A scale for flexible materials like TPR. Shore Hardness is measured by a device called a durometer, which determines a material’s resistance to indentation by a spring-loaded needle. The scale runs from 0 to 100, where a lower number indicates a softer, more easily indented material. TPR commonly exhibits a Shore Hardness in the range of 20A to 90A, covering a vast spectrum of textures. For example, a Shore 30A material feels similar to a soft rubber band, while a material rated around 70A is closer to a car tire tread or a shoe sole.
How TPR Composition Affects Final Texture
The specific texture and Shore Hardness rating of a TPR product are determined by its internal chemical makeup, which is based on a block copolymer structure. TPR is typically composed of Styrene-Butadiene-Styrene (SBS) copolymers, which feature both hard and soft segments. The hard, plastic-like styrene segments provide the material’s strength and thermoplastic processing capabilities. The soft, rubbery butadiene segments impart the material’s elasticity and soft feel. By changing the ratio between these hard and soft components, manufacturers can precisely manipulate the final texture, a process known as compounding. Furthermore, the addition of plasticizers, fillers, and other functional additives allows for fine-tuning the softness, grip, and overall tactile feel of the finished product.
Common Applications of Soft TPR
The soft grades of TPR are deliberately chosen for products where a comfortable, non-slip, or shock-absorbing feel is desired. Soft TPR is frequently used in footwear, particularly for injection-molded shoe soles, where its flexibility and cushioning are highly valued. The material’s grip and pleasant feel also make it an ideal choice for overmolded soft-touch handles on tools, kitchen utensils, and toothbrushes. In the toy industry, soft TPR is used to create pliable action figures, squeeze toys, and components that require a rubber-like texture for safety and playability.