The change in tensile strength after blending TPE elastomer with PP depends on the ratio of the two materials, their compatibility, and the processing technology. Generally, tensile strength increases significantly with increasing PP content; however, excessively high PP content may lead to increased brittleness, requiring compatibilizers or process optimization to balance performance.
The blending of TPE elastomer and PP is a typical composite system of thermoplastic elastomer and crystalline plastic. The rubber phase of TPE provides flexibility and elasticity, while the crystalline phase of PP imparts rigidity. When the PP content is low, the continuous phase structure of TPE dominates, maintaining good elasticity, but the increase in tensile strength is limited. As the PP content increases, its crystalline structure gradually forms a continuous phase, significantly improving the tensile strength through physical entanglement and possible chemical bonding between molecular chains. For example, in applications such as automotive sealing strips or tool handles, appropriately increasing the PP content can enhance the product's resistance to deformation and meet high strength requirements.
Compatibility is a key factor affecting tensile strength. The polarity difference between TPE and PP may lead to weak interfacial bonding between the two phases, forming a significant phase separation structure, thus limiting the improvement of tensile strength. To address this issue, compatibilizers are typically added, such as maleic anhydride-grafted polypropylene (MAH-g-PP) or chlorinated polypropylene (CPP). These compatibilizers improve the interface between the two phases through chemical bonding or intermolecular forces, promoting stress transfer and significantly increasing tensile strength. Experiments show that adding an appropriate amount of compatibilizer can increase the tensile strength of the blend several times while maintaining good elongation at break.
The processing technology also significantly affects tensile strength. Temperature, shear force, and mixing time during blending must be precisely controlled to ensure uniform dispersion of PP in the TPE matrix. If PP particles are too large or unevenly distributed, stress concentration points can easily form, leading to a decrease in tensile strength. Furthermore, the application of dynamic vulcanization can further enhance performance. By introducing a vulcanizing agent during blending, the rubber phase of the TPE forms a cross-linked structure, while the PP remains thermoplastic, thus preparing a thermoplastic vulcanizate (TPV) with both high strength and high elasticity. This material outperforms ordinary blends in terms of tensile strength, abrasion resistance, and aging resistance.
The tensile strength of TPE/PP blends is also influenced by the material's morphology and structure. When PP is the dispersed phase, the material exhibits typical elastomer behavior with low tensile strength. As the PP proportion increases, it gradually forms a continuous phase, and the material transforms into a plastic material, significantly increasing tensile strength. For example, when the PP mass fraction exceeds a certain level, the tensile curve shows a distinct yield point and necking phenomenon, typical characteristics of plastic tensile behavior. At this point, the tensile strength of the material approaches that of pure PP, but the elongation at break decreases significantly, requiring adjustment of the formulation to balance strength and toughness.
In practical applications, optimizing the tensile strength of TPE/PP blends requires a comprehensive consideration of cost and performance. PP is inexpensive and widely available; increasing its proportion can effectively reduce material costs while simultaneously improving strength. However, excessively pursuing high strength may lead to a loss of elasticity, affecting the user experience. Therefore, the formulation needs to be adjusted according to the specific application scenario. For example, automotive interior parts require a balance between strength and tactile feel, typically using a medium PP content; while tool handles may opt for a higher PP proportion to enhance durability.
The change in tensile strength after TPE elastomer is blended with PP is the result of the combined effects of formulation ratio, compatibility, processing technology, and morphological structure. Through rational design of formulations and processes, materials with both high strength and high elasticity can be prepared to meet the needs of various fields. In the future, with the further development of compatibilizer technology and dynamic vulcanization processes, the performance of TPE/PP blends will be even better, and their application range will continue to expand.
