Technical Practice of Rubber Electrical Performance, Tear Strength and Dielectric Performance Test Molds
With the continuous increase in requirements for extreme environmental resistance and performance stability of high-end rubber products, rubber electrical performance test molds, rubber tear strength test molds, and rubber dielectric performance test molds are facing industry pain points such as insufficient accuracy, weak scenario adaptability, and high energy consumption. Promoting the iteration of these molds towards high-precision forming, multi-scenario customization, low-carbon production, and intelligent control has become an important path to ensure the effectiveness of rubber material performance evaluation and support industrial technological upgrading.
1. Core Design Logic and Technical Parameters of Three Types of Test Molds
1.1 Rubber Electrical Performance Test Molds
Designed to evaluate the electrical properties (e.g., conductivity, insulation) of rubber materials, these molds focus on ensuring sample forming accuracy and electrode compatibility. The cavity body is made of Cr12MoV alloy tool steel, with a hardness of HRC58-62 after cryogenic treatment, ensuring a dimensional deviation of no more than 0.005mm after long-term use to avoid test data errors caused by sample geometric deviations.
For plate electrode testing, the cavity accommodates circular samples (50-100mm in diameter) or square samples (50-75mm), with a thickness adjustment range of 0.5-5mm and a strict tolerance of ±0.05mm. The cavity surface is mirror-polished (Ra≤0.2μm) and equipped with 0.1mm-wide micro-exhaust grooves to reduce bubble formation during vulcanization—bubbles can cause over 15% deviation in breakdown voltage test results, severely affecting data accuracy. The guiding mechanism uses 20CrMnTi alloy steel guide pillars with a fit clearance of 0.02-0.03mm to ensure mold clamping accuracy and improve sample consistency.
1.2 Rubber Tear Strength Test Molds
These molds are designed to produce standard tear samples, complying with the shape requirements of standards such as ASTM D624. The main body is made of H13 hot-work die steel, with a tensile strength of ≥1200MPa after quenching and tempering, enabling it to withstand temperature and pressure impacts during vulcanization and extend mold life.
The cavity is compatible with multiple sample types (Type A, B, C) and strictly follows standard dimensions: Type A samples have a narrow section width of 6.0±0.1mm; Type B samples have a notch area radius of 19.0±0.1mm. A notch positioning slot is reserved to control the initial notch depth at 0.50±0.05mm. The sample thickness is uniformly set to 2.3±0.2mm, and the cavity adopts an integrated structure to avoid sample burrs caused by splicing gaps. The cavity surface is coated with PTFE, reducing demolding resistance by over 35% and controlling the sample damage rate below 0.3%.
1.3 Rubber Dielectric Performance Test Molds
Dielectric performance testing requires high sample uniformity, so these molds focus on ensuring thickness consistency and insulation protection. The cavity is made of ceramic-reinforced composite materials with excellent insulation properties, combined with a Cr12MoV steel mold frame to ensure structural strength and avoid stray current interference.
The cavity adopts an independent single-cavity design, accommodating circular samples (75mm in diameter) with a thickness tolerance of ±0.03mm, ensuring a dielectric constant test deviation of no more than ±2%. For high-frequency electric field testing, the mold has a built-in shielding structure to reduce external electromagnetic interference. During vulcanization, the cavity temperature is stabilized at 150±1℃ through flexible temperature control channels, and with a vulcanization pressure of 10-15MPa, the sample density uniformity is increased to over 98%. The cavity surface is coated with Al₂O₃ ceramic to enhance chemical corrosion resistance and adapt to the vulcanization of various rubber materials.
2. Practical Application and Maintenance Specifications of Molds
2.1 Key Processes of Sample Preparation
Rubber pre-treatment is essential: rubber materials should be placed in an environment with 23±2℃ and 50±5% relative humidity for 3-24 hours to eliminate internal stress—untreated rubber can cause an 8% sample warpage rate, directly affecting test accuracy. Mold preheating varies by type: electrical and dielectric performance molds are preheated to 80-90℃, while tear strength molds are preheated to 70-80℃, with a 15-minute heat preservation before loading.
Vulcanization parameters are adjusted based on rubber types: natural rubber is vulcanized at 150±2℃ for 15-20 minutes; nitrile rubber at 155±2℃ for 20-25 minutes, both with a pressure of 12-15MPa. After demolding, samples should be placed in a standard environment for 24 hours to stabilize performance before testing.
2.2 Core Points of Mold Maintenance
After daily use, the cavity should be wiped with acetone using a dust-free cloth to remove residual rubber scraps; moving parts should be lubricated with special grease weekly to prevent increased fit clearance. For periodic calibration, 0-grade gauge blocks are used monthly to test cavity dimensions—when the narrow section width deviation of tear strength samples exceeds ±0.05mm, diamond grinding wheels are used for repair.
Coating maintenance should be carried out regularly: after 200 molding cycles, an eddy current thickness gauge is used to test the coating thickness; PTFE coating should be replenished when its thickness is less than 2μm to ensure stable demolding performance. When not in use, molds should be coated with anti-rust oil, sealed, and stored in a dry environment (20±5℃, relative humidity ≤65%) to avoid oxidation and rust affecting accuracy.
3. Technology Development Trends and Industry Application Expansion
3.1 In-depth Integration of Sensing and Control Technology
Traditional molds are gradually upgrading to "sensing and controllable" models. Micro temperature and pressure sensors are embedded in key parts (e.g., cavity, guiding mechanism) to collect real-time vulcanization data at a sampling frequency of 100Hz; data is transmitted to cloud platforms via industrial IoT for analysis and modeling. Combined with digital twin technology to build virtual simulation models of molds, the molding effects under different rubber materials and process parameters can be simulated in advance, reducing mold testing times by over 40% and significantly shortening the R&D cycle. High-end molds have achieved closed-loop control—when cavity pressure fluctuation exceeds ±0.5MPa, the system automatically adjusts vulcanizing machine parameters to increase sample consistency to over 95%. Meanwhile, mold wear status is analyzed through vibration data and temperature curves to achieve predictive maintenance, reducing fault downtime by 60%.
3.2 Upgrade of Low-Carbon Manufacturing and Efficient Resource Utilization
Driven by the "dual carbon" goal, the mold industry is achieving low-carbon transformation through material innovation and process optimization. In terms of materials, the application ratio of recycled alloy tool steel is increasing—recycled Cr12MoV steel has a recovery rate of 85%, with mechanical properties equivalent to new steel after vacuum heat treatment and a 20% lower production cost. In processing, laser engraving and 3D printing replace traditional milling, reducing metal scrap generation by 55% and increasing material utilization from 30% to 95%. Demolding coatings gradually adopt water-based environmentally friendly formulas to replace traditional solvent-based coatings, reducing VOCs emissions by 80%; meanwhile, coating service life is extended to over 200 cycles through thickness increase and process optimization, reducing consumable replacement frequency.
3.3 Breakthrough in Cross-Scenario Customization and Performance Enhancement
To meet the extreme service requirements of emerging industries, mold customization capabilities and performance limits are continuously breaking through. For high-voltage rubber parts testing in new energy vehicles, special molds for -40℃ low-temperature vulcanization have been developed—with built-in low-temperature insulation layers and flexible temperature control channels in the cavity, the vulcanization temperature is stabilized at -40±2℃ to meet insulation performance testing needs in low-temperature environments. In the aerospace field, tungsten alloy-reinforced cavities are used to withstand vulcanization temperatures above 300℃ while maintaining cavity dimensional accuracy within ±0.005mm. In terms of performance enhancement, dielectric performance test molds use nano-SiO₂ composite coatings—compared with traditional Al₂O₃ coatings, insulation resistance is increased by one order of magnitude, and stray capacitance interference is reduced by 40%, adapting to higher-precision dielectric constant testing. The guiding mechanism of electrical performance test molds adopts self-lubricating ceramic bearings, increasing fit clearance stability by 50% and ensuring sample forming accuracy even after long-term high-frequency use, reducing test deviations caused by mechanism wear.
As core equipment for rubber material performance evaluation, the technological iteration of these three types of molds directly improves test accuracy and efficiency. In the future, with the expansion of emerging industry demands and the advancement of material technology, molds will continue to break through towards "scenario-based customization and high-performance enhancement," providing more precise technical support for the R&D and quality control of high-end rubber products.
