I. Project Background
Electric tools are widely used in industrial production, construction, and home DIY projects. As a key component that provides direct contact between the user and the electric tool, the handle’s performance directly affects the user experience and operational safety. Traditional electric-tool handles are typically made from single materials—either rigid plastics or metals—which can easily cause hand fatigue during prolonged use. Moreover, in wet or oily environments, these handles tend to slip, posing significant safety risks. To enhance the comfort, anti-slip performance, and durability of electric-tool handles, TPE material TN65A - DDGJ, with its unique properties, has become the ideal choice for handle overmolding.
II. TN65A - DDGJ Material Properties
Moderate Hardness and High Elasticity: TN65A - DDGJ has a Shore A hardness of 65A, which enables it to provide excellent support while maintaining outstanding elasticity. When users grip the handle of power tools, this material effectively cushions the impact forces generated by tool vibrations, thereby reducing hand fatigue. For instance, when using power tools with significant vibration—such as electric drills or chainsaws—for extended periods, the TN65A - DDGJ material used for handle grips can absorb most of the vibrational energy, significantly reducing the vibrations felt by the hands.
Excellent anti-slip performance: The material surface has undergone special treatment, giving it a high coefficient of friction. Even when the handle surface is wet or oily, it can still provide users with a reliable grip. According to friction coefficient tests, the TN65A-DDGJ achieves a friction coefficient of up to 0.8 in dry conditions and maintains a value above 0.6 even in damp conditions, effectively preventing tools from slipping unexpectedly during use and ensuring operational safety.
Excellent Chemical Resistance: During operation, the handles of power tools may come into contact with various chemicals, such as lubricants and cleaning agents. The TN65A - DDGJ exhibits outstanding chemical resistance; after immersion in common chemical reagents, its material properties show no significant changes. For example, after being immersed for 72 hours in a 5% hydrochloric acid solution, a 10% sodium hydroxide solution, and common lubricants, the material’s hardness, tensile strength, and elasticity remained within a variation of 5%, ensuring the handle’s long-term stability even in challenging operating environments.
Excellent processing performance: This material exhibits excellent flowability, enabling it to fill mold cavities quickly and uniformly during injection molding, thereby boosting production efficiency. At the same time, it demonstrates outstanding adhesion to common electric tool handle substrates (such as PP and ABS). Through a two-shot injection molding process, it can be firmly bonded to the substrate, ensuring that the overmolded layer remains securely attached even under prolonged use. In actual production, when using TN65A-DDGJ for handle overmolding, the yield rate of qualified products can exceed 98%.
Environmental and Safety Compliance: TN65A - DDGJ meets environmental standards and is free from harmful substances such as phthalates and heavy metals. During both production and use, it poses no risk to the environment or human health, thus satisfying modern consumers’ demand for eco-friendly products. Moreover, the material’s non-toxic and odorless properties enhance user comfort when operating power tools.
III. Key Design Considerations for Rubber-Coated Handles on Power Tools
Ergonomic Design: The shape and size of the handle have been optimized based on human hand-gripping habits. The handle’s thickness should be moderate, typically with a diameter ranging from 30 to 40 mm, ensuring that users with different hand sizes can hold it comfortably. At the same time, the handle surface features grooves and protrusions that correspond to the natural resting positions of the fingers—for example, finger grooves are designed on both sides of the handle, allowing users to better control the tool and reducing tension in the hand muscles.
Thickness of the rubber-coating layer: The thickness of the rubber-coating layer should be determined appropriately based on the type of power tool and its intended application scenario. For small power tools such as electric screwdrivers and electric grinders, a rubber-coating thickness of 1–2 mm is generally sufficient to meet requirements. For larger power tools that generate significant vibrations—such as electric hammers and electric saws—the rubber-coating thickness can be appropriately increased to 2–3 mm to provide better shock absorption and anti-slip performance.
Color and Appearance Design: The TN65A - DDGJ model can be customized in a variety of colors by adding color masterbatches, meeting the personalized appearance requirements of different brands. At the same time, special textures such as matte finishes or diamond patterns can be designed on the surface of the overmolded layer, which not only enhance the aesthetic appeal of the handle but also further improve its anti-slip performance. Additionally, through two-color injection molding or multi-color injection molding processes, brand logos or warning signs can be incorporated into the handle, thereby boosting product recognition and safety.
4. Production Process
Raw material preparation
TN65A - DDGJ Preprocessing: Dry the TN65A - DDGJ raw material in an oven at 80℃ for 2–3 hours to remove moisture from the material, thereby preventing defects such as bubbles and silver streaks in the molded products caused by moisture evaporation during injection molding.
Substrate Preparation: Clean the PP or ABS substrate—used as the handle’s main body—to remove surface oils, dust, and other impurities. Methods such as ultrasonic cleaning or alcohol wiping can be employed. At the same time, perform appropriate surface roughening treatment on the substrate, such as sandblasting, to increase the bonding area between the substrate and the TN65A-DDGJ overmolding layer, thereby enhancing the bonding strength.
Injection Molding Process Parameters
Injection molding temperature: For TN65A—DDGJ, the injection molding temperature is typically maintained within the range of 180–200℃ to ensure thorough melting of the material and excellent flowability. In actual production, the temperature can be adjusted appropriately based on factors such as mold design, product dimensions, and the performance of the injection molding machine. For instance, for thin-walled products, the injection molding temperature can be slightly increased to 190–210℃; whereas for thick-walled products, the temperature can be slightly reduced to 170–190℃.
Injection Pressure and Speed: The injection pressure is determined based on the product’s shape, size, and mold structure, typically ranging from 80 to 120 MPa. The injection speed should not be too fast, as this could lead to jetting marks that compromise the product’s appearance quality; it is usually controlled within the range of 30 to 60 mm/s. During the filling process, it is essential to ensure that the material fills the mold cavity uniformly and rapidly, thereby avoiding issues such as insufficient material or trapped air.
Holding pressure and holding time: The holding pressure is typically 60% to 80% of the injection pressure. The holding time is determined based on the product thickness, generally ranging from 5 to 15 seconds. The purpose of holding pressure is to replenish material into the mold cavity during the cooling and shrinkage process of the product, thereby preventing defects such as sink marks and deformation. For products with greater thickness, the holding time can be appropriately extended; for products with thinner walls, the holding time can be slightly shortened.
Cooling Time: The cooling time is determined by the product thickness and the efficiency of the mold cooling system, typically ranging from 15 to 30 seconds. During the cooling process, it is essential to ensure that the product cools sufficiently and sets properly without deforming when demolded. By optimizing the mold cooling system—such as adopting circulating water cooling or increasing the number of cooling channels—cooling time can be effectively shortened, thereby improving production efficiency.
Secondary Injection Molding Operation
Substrate Positioning and Fixation: Before the secondary injection molding, precisely position and securely fix the substrate—previously formed through primary injection molding—within the mold. Positioning can be achieved using methods such as locating pins or locating grooves to ensure that the substrate remains accurately positioned during the injection of the TN65A-DDGJ overmolding layer, thereby preventing issues like overmolding shift or uneven thickness. The positioning accuracy should be controlled within ±0.1 mm.
Injection Molding Sequence Control: First, inject the base material. After the base material has cooled and solidified, rotate or move the mold to the second injection station and then proceed with the injection of the TN65A-DDGJ overmolding layer. During the injection process, strictly control the time interval between the two injections—generally no more than 30 seconds—to ensure optimal adhesion between the TN65A-DDGJ and the base material. At the same time, during the second injection, make sure that parameters such as injection pressure and injection speed are consistent with those used in the first injection, thereby guaranteeing product quality consistency.
V. Quality Control
Appearance Inspection: A combination of visual inspection and optical instrument inspection is employed to perform 100% inspection of product appearance. The inspection checks the product surface for defects such as bubbles, flow marks, insufficient material, and flash. It also verifies that the product dimensions meet the design requirements, with dimensional tolerances controlled within ±0.1 mm. Products with obvious appearance defects are directly scrapped; those with dimensional deviations within the allowable range may be appropriately trimmed before being accepted into inventory.
Bond Strength Testing: A certain proportion of products is randomly selected, and the bond strength between TN65A - DDGJ and the substrate is tested using methods such as peel tests and tensile tests. The peel strength requirement is no less than 3.5 N/cm, and the tensile strength must be at least 4 MPa, ensuring that the coating layer remains firmly bonded to the substrate over the long term. For products that fail to meet the bond strength requirements, the underlying causes—such as improper injection molding process parameters or inadequate surface treatment of the substrate—are analyzed, and appropriate corrective measures are implemented, including adjusting process parameters and optimizing the substrate surface treatment process.
Performance Testing: Conduct appropriate performance tests based on the usage scenarios and functional requirements of power tools, such as slip resistance testing, chemical resistance testing, and vibration attenuation testing. For slip resistance testing, a method that simulates real-world usage conditions is employed—for example, after applying water or oil to the handle surface, the tool’s sliding behavior at different tilt angles is tested. In chemical resistance testing, the product is immersed in common chemical reagents to observe whether it exhibits deformation, discoloration, or delamination. Vibration attenuation testing involves simulating the actual vibration conditions experienced by power tools to evaluate the handle’s grip layer’s ability to absorb and attenuate vibrations. For products that fail performance testing, timely corrective actions shall be taken to ensure that product quality meets the relevant standards.
VI. Cost Analysis
Material Cost: The material price of TN65A - DDGJ is relatively moderate and offers a certain cost advantage compared to some high-performance TPE materials. By optimizing product design and manufacturing processes and appropriately controlling the thickness of the rubber-coating layer, material usage can be effectively reduced, further lowering material costs. For example, while maintaining product performance, reducing the rubber-coating layer thickness from 3 mm to 2.5 mm can cut material consumption by approximately 20%.
Mold Costs: The design and manufacture of rubber-coating molds for power tool handles are relatively complex and costly. However, by selecting the appropriate mold type and materials, optimizing the mold structure, and extending the mold’s service life, it is possible to amortize the mold costs. For example, using hot-runner molds can reduce material waste, improve production efficiency, and lower the overall cost of mold usage. Moreover, choosing high-quality mold steels—such as Cr12MoV—can enhance the mold’s wear resistance and service life, thereby reducing the frequency of mold repairs and replacements.
Production efficiency and cost: TN65A—DDGJ boasts excellent processing performance and reasonably set injection molding process parameters, which can enhance production efficiency, shorten the production cycle, and reduce labor costs and equipment energy consumption. By optimizing the production process and reducing the defect rate, production costs can also be effectively lowered. For example, by fine-tuning the injection molding process parameters to increase the yield of good-quality products from 95% to 98%, the per-unit production cost can be reduced by approximately 3%.
VII. Market Prospects
As consumer demand for electric tools continues to rise and environmental awareness grows, the market for electric tools featuring high-performance TPE materials such as TN65A-DDGJ for handle coating holds great promise. In the industrial sector, high-performance electric tool handles can enhance worker productivity, reduce fatigue, and lower the likelihood of workplace injuries, making them highly favored by businesses. In the home DIY market, electric tools that boast attractive aesthetics, comfortable use, and reliable safety are even more likely to capture consumers’ attention. Meanwhile, as the application of TN65A-DDGJ in electric tool handle coatings continues to expand, its potential applications in other fields—such as gardening tools and fitness equipment handles—are also expected to grow, indicating strong market development potential.