Development of Plastic FRP Hardhat Shell

At present, domestic materials used for manufacturing hard hats include high-density polyethylene (HDPE), ABS, polycarbonate (PC), toughened modified polypropylene, glass fiber reinforced polypropylene, and polyester fiberglass. Cap lining materials are: low density polyethylene (LDPE), HDPE/LDPE blends, etc. No matter what type of helmet shell, the design of the helmet must meet the requirements of use. The most important one is to protect the user's head from harm and to wear comfortably. FRP helmets have the advantages of insulation, acid and alkali resistance, high temperature resistance, low temperature resistance, static electricity resistance, impact resistance, flame retardance, and not easy to age, so in recent years, the production of hard plastic caps made of polyester fiberglass has developed rapidly, with an annual output of approximately 200 Wanding has played an important role in safety protection in construction, transportation, power and mining production. In order to improve the safety of such safety helmets for use at night and in dark places, we have developed on the basis of the original production of FRP helmets. A new luminous glass steel helmet has achieved good economic and social benefits.

Design of Hard Hat Caps

According to the principle of ergonomics, it can be known that the simulation of human head force: the geometric shape of the human head has better impact resistance. According to GB2428-89 "China Adult Head Series", the shape of the cap shell should be round or oval, with an internal diameter of 195~50mm, a width of 170~220mm, and a height of 120~150mm. The cap shell is provided with vent holes for heat dissipation. According to the strength of the cap shell, the electrician's safety helmet shall not be allowed to have vent holes, the color of the cap shell shall be clear, the protrusion in the cap shell shall not exceed 5mm, and there shall be a cushion around it to prevent the head from being damaged during impact compression deformation.

Raw materials and recipes

Unsaturated polyester (196): Changzhou Huarun Composite Material Co., Ltd.;
Initiator (MEKP-II): Yixing Hongda Plastic Chemical Co., Ltd.;
Accelerator: cobalt naphthenate solution (1% cobalt content);
Functional filler: homemade;
Luminous agent (PLO-7B): Dalian Luming Luminescence Technology Co., Ltd.;
Coupling agent (SiLink silanes): Nanjing Nengde Chemical Co., Ltd.;
Toughening agent (polysulfide rubber): Shanghai Hucheng Rubber Chemical Co., Ltd.;
Reinforced material (0.18~0.4mm alkali base cloth).

Unsaturated polyester fiberglass helmets can be manufactured using a variety of processes, including molding, injection, injection, hand lay-up and other processes. In the trial production process, we use the hand lay-up process.

Molding

Unsaturated polyester resin, initiator, accelerator, functional filler, coloring agent, luminous agent (PLO-7B) were thrown into the reactor, stirred and then put into a thickening agent, and then the reinforcing material was impregnated with the reaction solution. According to the GB2811-2007 provisions on the weight of helmets quantitative quantitative floor design. In order to improve the penetration resistance, a layer of 0.4mm gingham cloth is applied to the Φ120 cap top. Press molding was performed on the press and curing was performed in an oven at 60°C for 3 to 5 hours. According to the pattern dash, machining, and finally get the product.

Performance and Analysis of FRP Hard Hat Shell

The national standard GB2811-07 of the application helmet is used to test the product performance.

Note: The helmet shell weighs between 248-254 grams, and the total weight of the helmet is between 448-452.

From the test results, it can be seen that the performance of the helmet shell manufactured according to the basic formula and molding process fully meets the performance requirements of GB2811-07, and the light emission in the darkness is more than 12 hours, which fully meets the requirements for use.

The main performance of the hard hat shell is to see the impact performance, wear resistance, flame resistance, side pressure rigidity, luminous resistance, antistatic properties and appearance quality. Impact performance test is to use 5kg hemispherical steel hammer free to land from 1m high, impact cap top, cap head mold impact force should not be greater than 4900N, hat shell does not allow greater than 50mm cracks, with a tether rope does not promise to pull Broken. Therefore, the 196 unsaturated polyester resin with good toughness and high strength is used in the formula, and the initiator is MEKP-II. Polysulfide rubber is added into the formula as a toughening agent to improve its impact resistance. In addition, self-made functional fillers also play a role in improving impact resistance. In addition, from the structure of the helmet shell, the cap shell is contoured with a uniform streamline shape, and the surface is smooth. When the flying object or the falling object slides sideways on the cap shell, the impulse is decomposed, and The impulse on the cap reduces. The puncture resistance test is to use a 3kg steel cone (hardness HR45, taper 60°, cone tip radius 0.5mm) to fall freely from a height of 1m to impact the top of the cap and the steel cone should not be in contact with the headform.

From the production practice point of view, the helmet with impact performance up to the national standard has generally better wear-resistance performance. During the molding process, a layer of 0.4 square fiberglass cloth is developed in the top Φ120mm range of the cap shell to improve. The wear-resistance properties of the part, and the addition of toughening agents and functional fillers in the formulation to better ensure its puncture resistance. The side pressure rigidity of the helmet is when the helmet is laterally loaded with 424N pressure, the lateral deformation of the shell is not more than 40mm, and after the pressure relief, the residual deformation is less than 15mm. In order to satisfy the lateral rigidity requirements of the FRP helmets, only the high-rigidity resin and the good reinforcing material are selected, and the reinforcing measures are taken at the periphery of the cap shell without affecting the total weight of the cap shell.

The flame-retardant performance test of the FRP helmet is to install 70# gasoline into the 2kg gasoline torch, burn the cap for 10s, remove the flame, and the cap should self-extinguish in 5 (the temperature of the ignition temperature of the cap is 790±40°C). Environment 10~30°C. In order to achieve the flame-retardant requirements of the hard hat shell, chloroparaffin paraffin wax (chlorine content is 70%) and antimony trioxide are added to the functional fillers in the formula, and it has been proved in practice that the flame retardant is added to the functional filler. , And then filled with functional fillers into unsaturated polyester resins, can make its helmet's flame retardant reach the national standard. Antistatic performance According to the test method of GB2812-89 standard, the surface resistance of the cap shell is measured, and the requirement is not more than 1×109 ohms. Mainly in the functional filler by adding an appropriate amount of antistatic agent, reducing its surface resistance, thus playing an antistatic role.

The luminescent property of the helmet is the innovation point of the product. The product is developed on the basis of the ordinary glass steel safety helmet. The long residual glow additive is added into the unsaturated polyester glue solution. Or incandescent light can absorb light energy, in the dark state can absorb the light to glow in the form of glow, so as to ensure that the helmet glows in the dark. The darkness of the helmet that was produced by using the luminous agent (PLO-7B) produced by Dalian Luming Luminescent Technology Co., Ltd. was lighted for more than 12 hours, fully satisfying the user's requirements.

Appearance quality requirements appearance should not have microbubbles, pinholes, surface holes, wrinkles, cracks, bumps, defects, bruises, scars, poor curing, glitches and other defects, but promised to repair; products around the promise of burrs, degumming Stratification; the inner surface is flat and does not allow poor impregnation, delamination, frostbite, or defects.

in conclusion

Through the selection of raw materials, a fair formula is adopted, and a hand-paste process can be used to obtain a long-lasting glow-resistant glass steel helmet with a luminous time of over 12 months, and other properties that meet or exceed the national standards for safety helmet production (GB2811-07). The cap has a wide range of uses in the transportation, construction, mining, and power industries, and plays a good role in improving the security of staff operations in dark places and night operations.

Copyright Statement: This article is reproduced from online media and represents only the author's opinion. It has nothing to do with this site. If news articles and comments infringe your legal rights, please call us and we will handle it in a timely manner.