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, долговечность, and suitability for end-use. This article breaks down the two most common test methods (Shore and Rockwell), Ключевые влиятельные факторы, and practical applications—with clear comparisons, step-by-step guides, and tips to ensure accurate, надежные результаты.
1. Common Silicone Hardness Test Methods
Silicone’s elastic properties require specialized testing methods. Below are the two primary techniques, along with their principles, процедуры, и варианты использования:
| Test Method | Основной принцип | Step-by-Step Procedure | Ключевые параметры | Идеальные приложения |
| 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. Настраивать: Place the specimen on a rigid, flat surface (НАПРИМЕР., marble table) to avoid deformation during testing.3. Тестирование: Align the Shore hardness tester’s needle vertically with the specimen (no tilting). 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 (20мм друг от друга) and take the average. | – Берег а: For soft silicone (0–100 HA); indentation depth ~0.1–1mm.- Шор d: For hard silicone (0–100 HD); used when Shore A reads >90 HA.- Нагрузка: 1кг (Берег а), 5кг (Шор d). | – Soft silicone: Baby bottle nipples (20–30 HA), silicone phone cases (50–70 HA), medical catheters (30–40 HA).- Hard silicone: Автомобильные прокладки (80–90 HA → switch to Shore D), silicone cookware handles (60–80 HA). |
| Rockwell Hardness Test | A diamond cone (120° угол) or carbide ball (1.588мм диаметр) indenter is pressed into the silicone using two loads: initial load (to seat the indenter) и 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. Настраивать: Secure the specimen on the Rockwell tester’s stage. Select the indenter (diamond cone for hard silicone) and load (initial load: 10кг; main load: 60–150kg, depending on hardness).3. Тестирование: 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 (НАПРИМЕР., 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 (10кг) + Main (60kg = HRB, 150kg = HRC).- Точность: ±1 HR unit. | – High-precision industrial silicone: Aerospace seals (90–95 HA → HRC 20–30), high-wear silicone parts (НАПРИМЕР., pump diaphragms), and silicone composites (силикон + fiber reinforcement). |
Сравнение ключей: For most silicone products, а 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 (НАПРИМЕР., Промышленные детали).
2. Key Factors Influencing Test Accuracy
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 Specimen Thickness & Размер
Silicone’s elasticity means thin specimens deform under the tester’s load, leading to false low-hardness readings.
- Thickness Requirement: For Shore A tests, the specimen must be at least 10 times the indentation depth (НАПРИМЕР., if indentation is 1mm, specimen thickness ≥10mm). For Rockwell tests, thickness ≥6mm (to avoid the indenter touching the test surface below).
- Size Requirement: The specimen must be large enough to avoid “edge effects”—test points must be at least 20mm away from the specimen’s edges (edges deform more easily, skewing results).
- Пример: A 5mm-thick silicone phone case specimen will read 5–10 HA lower than its actual hardness (30 HA → 20–25 HA) because the thin material bends under the Shore tester’s load.
2.2 Test Environment (Температура & Влажность)
Silicone’s molecular structure is sensitive to temperature and moisture, which alter its hardness:
- Температура:
- Эффект: As temperature rises, silicone softens (hardness decreases). A 10°C increase can lower Shore A hardness by 3–5 HA (НАПРИМЕР., 50 HA at 23°C → 45–47 HA at 33°C).
- Control: Test at комнатная температура (23± 2 ° C.). If testing in hot/cold environments, let the specimen acclimate for 2–4 hours (until it reaches 23±2°C) before testing.
- Влажность:
- Эффект: Высокая влажность (>60%) causes silicone to absorb moisture, making it slightly softer (1–3 HA decrease).
- Control: Store specimens in a dry environment (humidity 40%–60%) для 24 hours before testing. For high-humidity regions, use a dehumidifier in the test area.
2.3 Tester Operation & Калибровка
Human error and uncalibrated tools are major sources of inaccuracy:
- Vertical Alignment: The tester’s needle must be perfectly vertical (±1°). A 5° tilt can increase indentation depth by 10% (НАПРИМЕР., 1mm → 1.1mm), lowering hardness by 5–8 HA.
- Loading Speed: Apply pressure at 1–2mm/s. Loading too fast (≥3mm/s) causes over-indentation (false low hardness); Слишком медленно (≤0.5mm/s) lets silicone recover elastically (false high hardness).
- Калибровка: Calibrate the tester every 3–6 months using a standard hardness block (НАПРИМЕР., 50 HA, 80 HA blocks for Shore A). An uncalibrated tester may read 10+ HA off (НАПРИМЕР., 60 HA actual → 70 HA uncalibrated).
3. Цель & Significance of Silicone Hardness Testing
Hardness testing isn’t just a quality check—it guides every stage of silicone product development and production:
3.1 Контроль качества (Производство)
- Raw Material Inspection: Test incoming silicone raw materials to ensure they meet hardness specifications (НАПРИМЕР., 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. Например, a silicone gasket factory tests 10 gaskets per batch—if 2 read 85 HA (spec: 75–80 HA), the batch is reworked (adjust crosslinker dosage to soften the silicone).
3.2 Material R&Дюймовый & Выбор
- Formulation Optimization: Ведущий&D teams adjust silicone formulations (НАПРИМЕР., adding fillers like silica powder) and test hardness to achieve target properties. Например:
- Добавление 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, достаточно тяжелый, чтобы сопротивляться износу).
- Силиконовые формы: 50–60 HA (balances flexibility for demolding and rigidity to retain shape).
4. Yigu Technology’s Perspective on Silicone Hardness Testing
В Yigu Technology, Мы видели 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: Расставить приоритеты Shore A testing for most applications—it’s cost-effective and aligns with consumer product needs. For industrial clients making hard silicone parts (НАПРИМЕР., 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. Окончательно, train operators on vertical alignment and loading speed—even small mistakes (НАПРИМЕР., 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. Часто задаваемые вопросы: Common Questions About Silicone Hardness Testing
1 квартал: Can I use a Shore A tester for hard silicone (НАПРИМЕР., 95 HA)?
А1: Нет — тестеры по Шору А рассчитаны на 0–90 HA.. Для силикона сложнее, чем 90 HA, Используйте Тестер по Шору D— Показания по Шору А выше 90 неточны (игла не может войти достаточно глубоко, чтобы измерить истинную твердость). Например, 95 Силикон HA покажет ~92 HA на тестере Shore A, но покажет правильное значение. 50 HD на тестере Shore D.
2 квартал: Why do my test results vary by 5–8 HA even with the same specimen?
А2: Изменения обычно происходят из трех проблем.: (1) Краевые эффекты: Испытание слишком близко к краю образца (должно быть на расстоянии ≥20 мм). (2) Эластическое восстановление: Не держите тестер достаточно долго (подождите 5–10 секунд, чтобы силикон стабилизировался.). (3) Поверхностные дефекты: 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?
А3: Rockwell tests require a minimum specimen thickness of 6мм—thinner specimens let the indenter touch the test stage below, causing false high hardness readings. Например, 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.