Silicone hardness test is a critical quality control and R&D tool for silicone products—from soft baby bottle nipples to hard automotive gaskets. It measures a silicone’s resistance to indentation, directly reflecting its flexibility, durabilidad, and suitability for end-use. Este artículo desglosa los dos métodos de prueba más comunes. (Costa y Rockwell), Factores de influencia clave, y aplicaciones prácticas, con comparaciones claras, guías paso a paso, y consejos para garantizar una precisión, resultados confiables.
1. Métodos comunes de prueba de dureza de la silicona
Silicone’s elastic properties require specialized testing methods. Below are the two primary techniques, along with their principles, procedimientos, y casos de uso:
| Test Method | Principio fundamental | Step-by-Step Procedure | Parámetros clave | Aplicaciones ideales |
| Shore Hardness Test | A needle of specific shape (conical for Shore A, spherical for Shore D) is pressed into the silicone surface under a fixed load. Hardness is determined by indentation depth—shallower = harder material. | 1. Sample Prep: Cut the silicone into flat, uniform specimens (surface roughness Ra ≤ 1.6μm). Ensure no bubbles or defects in the test area.2. Configuración: Place the specimen on a rigid, superficie plana (P.EJ., marble table) to avoid deformation during testing.3. Pruebas: Align the Shore hardness tester’s needle vertically with the specimen (sin inclinación). Apply pressure evenly at a speed of 1–2mm/s until the tester’s base touches the silicone surface.4. Reading: Hold the tester for 5–10 seconds (to account for silicone’s elasticity) and record the value. Repeat 3–5 times at different locations (20mm aparte) and take the average. | – Costa a: For soft silicone (0–100 HA); indentation depth ~0.1–1mm.- Orilla D: For hard silicone (0–100 HD); used when Shore A reads >90 HA.- Carga: 1kilos (Costa a), 5kilos (Orilla D). | – Soft silicone: Baby bottle nipples (20–30 HA), silicone phone cases (50–70 HA), medical catheters (30–40 HA).- Hard silicone: Juntas automotrices (80–90 HA → switch to Shore D), silicone cookware handles (60–80 HA). |
| Rockwell Hardness Test | A diamond cone (120° ángulo) or carbide ball (1.588diámetro mm) indenter is pressed into the silicone using two loads: initial load (to seat the indenter) y main load (to create the indentation). Hardness is calculated from the difference in indentation depth before/after removing the main load. | 1. Sample Prep: Machine the silicone into specimens with flat, parallel surfaces (thickness ≥6mm; size ≥10mm × 10mm). Polish the test surface to remove scratches.2. Configuración: Secure the specimen on the Rockwell tester’s stage. Select the indenter (diamond cone for hard silicone) and load (initial load: 10kilos; main load: 60–150kg, depending on hardness).3. Pruebas: Apply the initial load first—this ensures the indenter makes consistent contact with the silicone. Then add the main load and hold for 15–30 seconds. Remove the main load (keep the initial load) and record the indentation depth difference.4. Calculation: The tester automatically converts depth difference to Rockwell hardness (HR) values (P.EJ., HRC for diamond cone, HRB for carbide ball). | – Indenter: Diamond cone (HRC scale) for hard silicone; carbide ball (HRB) for medium-hard silicone.- Loads: Initial (10kilos) + Main (60kg = HRB, 150kg = HRC).- Exactitud: ±1 HR unit. | – High-precision industrial silicone: Aerospace seals (90–95 HA → HRC 20–30), high-wear silicone parts (P.EJ., pump diaphragms), and silicone composites (silicona + fiber reinforcement). |
Comparación clave: For most silicone products, el Shore Hardness Test is preferred—it’s faster, simpler, and causes minimal damage to specimens. The Rockwell test is reserved for hard, high-performance silicones where precise, load-based measurements are critical (P.EJ., piezas de maquinaria industrial).
2. Factores clave que influyen en la precisión de la prueba
Even the best test method yields unreliable results if external factors are unregulated. Below are the three most critical variables and how to control them:
2.1 Espesor de la muestra & Tamaño
Silicone’s elasticity means thin specimens deform under the tester’s load, lo que lleva a lecturas falsas de baja dureza.
- Requisito de espesor: Para pruebas Shore A, la muestra debe ser al menos 10 veces la profundidad de la sangría (P.EJ., si la sangría es de 1 mm, espesor de la muestra ≥10 mm). Para pruebas de Rockwell, thickness ≥6mm (para evitar que el penetrador toque la superficie de prueba debajo).
- Requisito de tamaño: La muestra debe ser lo suficientemente grande para evitar "efectos de borde"; los puntos de prueba deben ser al menos 20mm de distancia de los bordes de la muestra (Los bordes se deforman más fácilmente., resultados sesgados).
- Ejemplo: Una muestra de funda de teléfono de silicona de 5 mm de espesor leerá entre 5 y 10 HA menos que su dureza real (30 HA → 20-25 HA) porque el material delgado se dobla bajo la carga del probador Shore.
2.2 Entorno de prueba (Temperatura & Humedad)
La estructura molecular de la silicona es sensible a la temperatura y la humedad., que alteran su dureza:
- Temperatura:
- Efecto: A medida que aumenta la temperatura, la silicona suaviza (la dureza disminuye). Un aumento de 10°C puede reducir la dureza Shore A entre 3 y 5 HA (P.EJ., 50 Ha y 23 °C → 45–47 ha y 33 °C).
- Control: Prueba en temperatura ambiente (23± 2 ° C). Si realiza pruebas en ambientes fríos/calientes, Deje que la muestra se aclimate durante 2 a 4 horas. (hasta alcanzar los 23±2°C) antes de probar.
- Humedad:
- Efecto: Alta humedad (>60%) hace que la silicona absorba la humedad, haciéndolo un poco más suave (1–Disminución de 3 HA).
- Control: Almacene las muestras en un ambiente seco. (humedad 40%–60%) para 24 horas antes de la prueba. Para regiones de alta humedad, use un deshumidificador en el área de prueba.
2.3 Operación del probador & Calibración
El error humano y las herramientas no calibradas son fuentes importantes de inexactitud:
- Alineación vertical: La aguja del probador debe estar perfectamente vertical. (±1°). Una inclinación de 5° puede aumentar la profundidad de la sangría 10% (P.EJ., 1milímetros → 1,1 mm), reducir la dureza en 5–8 HA.
- Velocidad de carga: Aplicar presión a 1-2 mm/s. Cargando demasiado rápido (≥3 mm/s) causa una sangría excesiva (falsa baja dureza); demasiado lento (≤0,5 mm/s) permite que la silicona se recupere elásticamente (false high hardness).
- Calibración: Calibrate the tester every 3–6 months using a standard hardness block (P.EJ., 50 JA, 80 HA blocks for Shore A). An uncalibrated tester may read 10+ HA off (P.EJ., 60 HA actual → 70 HA uncalibrated).
3. Objetivo & Importancia de la prueba de dureza de la silicona
Hardness testing isn’t just a quality check—it guides every stage of silicone product development and production:
3.1 Control de calidad (Producción)
- Raw Material Inspection: Test incoming silicone raw materials to ensure they meet hardness specifications (P.EJ., a baby bottle manufacturer rejects silicone with 15 HA—too soft for safe use).
- Finished Product Testing: Sample 1–5% of finished goods to verify consistency. Por ejemplo, a silicone gasket factory tests 10 gaskets per batch—if 2 read 85 JA (spec: 75–80 HA), the batch is reworked (adjust crosslinker dosage to soften the silicone).
3.2 Material R&D & Selección
- Formulation Optimization: Riñonal&D teams adjust silicone formulations (P.EJ., adding fillers like silica powder) and test hardness to achieve target properties. Por ejemplo:
- Con la atención 5% silica powder increases Shore A hardness by 10–15 HA (30 HA → 40–45 HA), making the silicone suitable for cookware handles.
- Reducing crosslinker dosage by 2% lowers hardness by 5–8 HA (60 HA → 52–55 HA), ideal for flexible phone cases.
- Product-Specific Selection: Choose silicone hardness based on end-use needs:
- Medical gloves: 30–40 HA (soft for comfort, durable for repeated use).
- Automotive door seals: 60–70 HA (flexible to seal gaps, lo suficientemente difícil para resistir el desgaste).
- Moldes de silicona: 50–60 HA (balances flexibility for demolding and rigidity to retain shape).
4. La perspectiva de Yigu Technology sobre las pruebas de dureza de la silicona
En la tecnología yigu, Hemos visto 70% of silicone product failures stem from overlooked hardness issues—e.g., a client used 80 HA silicone for a baby pacifier (spec: 25–30 HA), leading to safety recalls. Our key advice: Priorizar Shore A testing for most applications—it’s cost-effective and aligns with consumer product needs. For industrial clients making hard silicone parts (P.EJ., aerospace seals), we recommend combining Shore D and Rockwell tests to cross-verify results. We also emphasize environmental control: A client in a tropical region (30°C+ humidity) saw 5–7 HA hardness variations until they installed dehumidifiers and temperature controllers. Finalmente, train operators on vertical alignment and loading speed—even small mistakes (P.EJ., 3° needle tilt) cost thousands in rework. Hardness testing is the foundation of reliable silicone products; cutting corners here risks product failure and brand damage.
5. Preguntas frecuentes: Preguntas comunes sobre las pruebas de dureza de la silicona
Q1: ¿Puedo utilizar un probador Shore A para silicona dura? (P.EJ., 95 JA)?
A1: No—Shore A testers are designed for 0–90 HA. For silicone harder than 90 JA, usar un Shore D tester—Shore A readings above 90 are inaccurate (the needle can’t indent deeply enough to measure true hardness). Por ejemplo, 95 HA silicone will read ~92 HA on a Shore A tester but show the correct 50 HD on a Shore D tester.
Q2: Why do my test results vary by 5–8 HA even with the same specimen?
A2: Variations usually come from three issues: (1) Edge effects: Testing too close to the specimen’s edge (must be ≥20mm away). (2) Elastic recovery: Not holding the tester long enough (wait 5–10 seconds for silicone to stabilize). (3) Defectos de la superficie: Bubbles or scratches in the test area—use a new specimen or test a different location. Fix these, and variations will drop to ≤2 HA.
Q3: How thick should my silicone specimen be for a Rockwell test?
A3: Rockwell tests require a minimum specimen thickness of 6milímetros—thinner specimens let the indenter touch the test stage below, causing false high hardness readings. Por ejemplo, a 4mm-thick specimen may read 10 HR higher than its actual value. If your silicone is thinner than 6mm, layer 2–3 specimens (each ≥2mm) with a thin layer of silicone glue (to avoid separation during testing)—ensure the glued surface is flat and free of air bubbles.