Safety Helmet for Safety Diagnosis and Inspection, and Method for Manufacturing the Same

Abstract

The present invention relates to a safety helmet for safety inspection and a method for manufacturing the same. The safety helmet for safety inspection according to the present invention comprises an outer shell formed of a self-healing polymer composite and a liner bonded to the inner side of the outer shell and comprising a shape-memory polymer. The self-healing polymer of the outer shell re-forms reversibly bonds upon heating to repair cracks that have occurred in the outer shell, and the shape-memory polymer of the liner deforms in response to external force when heated above its transformation temperature and maintains its deformed shape when cooled below its transformation temperature. According to the present invention, cracks in the outer shell of the safety helmet are repaired by active heating by the user, thereby extending the service life of the safety helmet, and the liner deforms and fixes to fit the head shape of each inspector, so that the safety helmet does not detach from the inspector's head even due to lateral impact.

Description

Technology Field

[0001] The present invention relates to a safety helmet for safety diagnosis inspection and a method for manufacturing the same. Background Technology

[0002] Safety inspection work is a task in which an inspector accesses the surface or interior of a facility to directly observe and measure damage such as cracks, deformation, spalling, or leakage in order to evaluate the safety of social infrastructure facilities such as bridges, tunnels, retaining walls, buildings, or dams. In such safety inspection work, wearing a safety helmet is essential to protect the inspector from the risk of falling objects, protrusions, or impacts that may be applied to the inspector's head.

[0003] Conventional safety helmets for safety inspection have been manufactured with a structure comprising an outer shell formed of a hard polymer, such as polycarbonate, polyethylene, or acrylonitrile-butadiene-styrene resin, to absorb external impact, and a liner formed of a foamed polymer, such as expanded polystyrene or expanded polyurethane, to cushion the impact on the inspector's head.

[0004] However, conventional safety helmets have a limitation in that it is difficult for inspectors to visually perceive micro-cracks in the outer shell caused by external impacts, UV exposure, friction, or moisture penetration during facility inspection work. Consequently, there is a risk of head injury to the inspector during safety diagnosis inspection work as the inspector continues to use a safety helmet with reduced shock absorption performance.

[0005] In addition, while the head shape of each inspector varies, conventional safety helmets include a liner manufactured in a standard size; consequently, the liner does not adhere completely to the specific head shape of each inspector, which results in the helmet detaching from the inspector's head when a lateral impact is applied, thereby reducing impact protection performance.

[0006] Furthermore, conventional safety helmets have limitations in that once a crack occurs, the crack cannot be repaired and must be discarded immediately, resulting in a limited lifespan and low resource efficiency due to the high frequency of helmet replacement in inspection operations.

[0007] Accordingly, there is a need for a new type of safety helmet for safety inspection in which cracks in the outer shell are restored by active heating by the user, the shape of the liner is deformed and fixed to fit the head shape of each inspector, and the heating mode can be visually recognized, as well as a method for manufacturing the same. Prior art literature

[0008] Korean Published Patent No. 10-2018-0019608 Korean Published Patent No. 10-2021-0012345

[0009] Chen, The problem to be solved

[0010] The present invention aims to provide a safety helmet for safety inspection in which cracks in the outer shell are restored by active heating by the user, even if cracks occur in the outer shell during use.

[0011] In addition, the present invention aims to provide a safety helmet for safety inspection in which a liner is deformed and fixed to fit the head shape of each inspector, so that the safety helmet does not detach from the inspector's head even due to lateral impact.

[0012] In addition, the present invention aims to provide a safety helmet for safety diagnostic inspection in which the heating mode of the safety helmet is visually recognized as a liner deformation mode and an outer shell self-healing mode, allowing the user to visually check the heating conditions.

[0013] In addition, the present invention aims to provide a method for manufacturing a safety helmet in which the self-healing behavior of the outer shell and the shape memory behavior of the liner are stably manifested by manufacturing the safety helmet for safety diagnosis inspection in a separation step. means of solving the problem

[0014] One aspect of the present invention relates to a self-healing polymer composite for a safety helmet sheath. A self-healing polymer composite according to one aspect of the present invention comprises a polymer matrix and a self-healing functional group reversibly bonded to the polymer matrix, wherein the reversible bond is reformed by heating to repair a crack that has occurred in the polymer matrix.

[0015] Another aspect of the present invention relates to a safety helmet for safety inspection that protects the head of an inspector. A safety helmet according to another aspect of the present invention comprises (a) an outer shell and (b) a liner coupled to the inner side of the outer shell, wherein the outer shell is formed of a self-healing polymer composite according to one aspect of the present invention, and the liner comprises a shape memory polymer, wherein the shape memory polymer deforms according to an external force when heated above a transformation temperature and maintains the deformed shape when cooled below the transformation temperature.

[0016] Another aspect of the present invention relates to a method for manufacturing a safety helmet for safety inspection. A manufacturing method according to another aspect of the present invention comprises the steps of: (A) forming an outer shell with a self-healing polymer composite; (B) forming a liner with a shape-memory polymer; and (C) bonding the liner to the inner side of the outer shell. Effects of the invention

[0017] The safety helmet for safety inspection according to the present invention has an outer shell formed of a self-healing polymer composite material, so that even if micro-cracks occur in the outer shell due to external impact, ultraviolet rays, or exposure to moisture, reversible bonds are reformed by active heating by the user to heal the cracks. Accordingly, unlike conventional safety helmets, the helmet is not immediately discarded after cracks occur, and its safety rating is restored solely through heat treatment, thereby extending the lifespan of the safety helmet.

[0018] In addition, the safety helmet according to the present invention has a liner formed of a shape-memory polymer, so when the liner is temporarily heated above the transformation temperature while the safety helmet is worn on the head of an inspector, the liner deforms to fit the individual head shape of the inspector, and after cooling below the transformation temperature, the deformed shape is maintained; thus, unlike standard-size safety helmets, the safety helmet does not detach from the inspector's head even due to lateral impact, and impact protection behavior is exhibited.

[0019] In addition, the safety helmet according to the present invention has a thermochromic indicator formed on the outer surface of the outer shell that changes color at a first discoloration temperature in the liner transformation temperature range and a second discoloration temperature in the outer shell self-healing recovery temperature range, respectively, so that while heating the safety helmet, the user can visually distinguish whether the heating mode corresponds to the liner deformation mode or the outer shell self-healing mode.

[0020] In addition, in the method for manufacturing a safety helmet according to the present invention, the outer shell molding step and the liner molding step are performed separately, thereby stably exhibiting both the self-healing behavior of the outer shell and the shape memory behavior of the liner. Furthermore, if a step of deforming the liner to fit the user's head shape is added after liner molding, the user can wear the safety helmet as is without any separate additional shape fitting procedure at the time of receiving it. Brief explanation of the drawing

[0021] FIG. 1 is a cross-sectional view showing the overall configuration of a safety helmet for safety diagnosis inspection according to one embodiment of the present invention. FIG. 2 is a schematic diagram showing the self-healing mechanism of a self-healing polymer composite for an outer skin according to one embodiment of the present invention. FIG. 3 is an operating principle diagram showing the transformation behavior of a shape memory polymer of a liner in stages according to one embodiment of the present invention. FIG. 4 is a schematic diagram showing the circuit configuration of a heating element according to one embodiment of the present invention. FIG. 5 is a schematic diagram showing the multi-color change behavior of a thermochromic display unit according to one embodiment of the present invention. FIG. 6 is a process flow diagram showing (A) an outer shell molding step, (B) a liner molding step, and (C) a step of combining the outer shell and the liner of a method for manufacturing a safety helmet according to one embodiment of the present invention. FIG. 7 is a schematic diagram illustrating (D) a step of deforming the liner head shape and (E) a step of fixing the deformed shape by cooling below the transformation temperature of a method for manufacturing a safety helmet according to one embodiment of the present invention. Specific details for implementing the invention

[0022] Embodiments of the present invention will be described in detail below with reference to the drawings. However, detailed descriptions of known functions or configurations that may obscure the essence of the present invention in the following description and the attached drawings are omitted.

[0023] Additionally, throughout the specification, the term 'comprising' a component means that, unless specifically stated otherwise, it does not exclude other components but may include additional components. That is, expressions such as 'comprising,' 'having,' 'consisting of,' and 'composed of' in this specification may include additional parts unless 'only' is used.

[0024] Furthermore, numerical values ​​or numerical ranges described in this specification shall be interpreted as including a margin of error unless otherwise explicitly stated. Additionally, the expression 'X to Y' indicating a numerical range in this specification means 'X or greater and Y or less'.

[0025] The key terms used in this specification are defined below.

[0026] In this specification, "self-healing polymer" refers to a polymer in which, when a crack occurs in the polymer due to external impact or environmental exposure, the cracked area is healed by external stimuli such as heating or light irradiation, thereby restoring the polymer's original mechanical behavior.

[0027] In this specification, "reversible bond" refers to a chemical bond in which bonding and dissociation proceed reversibly due to external stimuli, and in this invention, the Diels-Alder reversible cyclic bond between a furan group and a maleimide group corresponds to an example of a reversible bond.

[0028] In this specification, "shape memory polymer" refers to a polymer that exhibits behavior in which it deforms into an arbitrary shape upon reaching a transformation temperature above the transformation temperature upon heating, maintains the deformed shape upon cooling below the transformation temperature, and returns to its original shape upon reheating above the transformation temperature.

[0029] In this specification, "transformation temperature" refers to the temperature at which a phase transition occurs between the crystalline and amorphous phases or between the glass and rubber phases of a shape memory polymer, and in the case of poly(ε-caprolactone)-based shape memory polymers, it corresponds to the vicinity of the melting point.

[0030] One aspect of the present invention relates to a self-healing polymer composite for safety helmet shells.

[0031] A self-healing polymer composite according to one aspect of the present invention comprises (a) a polymer matrix and (b) a self-healing functional group reversibly bonded to the polymer matrix. The self-healing functional group repairs a crack that has formed in the polymer matrix by reforming the reversible bond upon heating.

[0032] The polymer matrix above provides the mechanical strength and shock absorption capabilities required for a safety helmet shell, and according to one embodiment, comprises one or more selected from the group consisting of polyurethane, epoxy resin, poly(methyl methacrylate), and polystyrene. Polyurethane and epoxy resin have excellent cross-linking reactivity with reversible self-healing functional groups, forming strong cross-linking bonds between the self-healing functional groups and the matrix.

[0033] The self-healing functional group is a functional group in which the dissociation and reformation of reversible bonds proceed reversibly upon heating, and according to one embodiment, includes a furan group and a maleimide group. The furan group and the maleimide group form a Diels-Alder reversible cyclic bond upon heating, the cyclic bond dissociates upon further heating, and the cyclic bond reforms upon cooling, exhibiting reversible cyclic behavior.

[0034] In a self-healing polymer composite according to one aspect of the present invention, even if microcracks occur in the outer shell due to external impact, ultraviolet rays, or moisture exposure during use of a safety helmet, the cracked area is restored by reversibly reforming the bonds of self-healing functional groups through external heating, and accordingly, the shock absorption behavior of the safety helmet is restored.

[0035] According to one embodiment, the content of the self-healing polymer containing the self-healing functional group is 5-20 wt% based on the total weight of the self-healing polymer composite.

[0036] When the content of the self-healing polymer is 5-20 wt%, the distribution density of self-healing functional groups within the polymer matrix satisfies the critical value required for crack recovery, and reversible bonds are sufficiently reformed at the crack site, thereby exhibiting self-healing recovery behavior. On the other hand, when the content of the self-healing polymer is less than 5 wt%, the distribution density of self-healing functional groups is insufficient, so reversible bond reformation at the crack site is interrupted and self-healing behavior is not exhibited. When the content of the self-healing polymer is more than 20 wt%, the self-healing polymer excessively plasticizes the cross-linked structure of the polymer matrix, and behavior is exhibited in which the mechanical strength required for the outer shell of a safety helmet is reduced.

[0037] According to another embodiment, the self-healing functional group comprises a furan group and a maleimide group, and the reversible bond is a Diels-Alder reversible cyclic bond between the furan group and the maleimide group.

[0038] In the case where the self-healing functional groups are furan and maleimide groups and the reversible bond is a Diels-Alder reversible cyclic bond, a cycle behavior is exhibited in which the cyclic bond is reversibly dissociated and reformed by heating, so that even if the same safety helmet shell undergoes multiple heating self-healing cycles, the decrease in self-healing efficiency is minimal. On the other hand, when a method of releasing self-healing monomers through microcapsule rupture is adopted as another self-healing mechanism, the monomers within the microcapsules are depleted in a single self-healing cycle, so that additional self-healing is impossible when additional cracks occur in the same area.

[0039] According to another embodiment, the self-healing is performed at a recovery temperature of 80-120°C.

[0040] When the above self-healing recovery temperature is 80-120 ℃, the reversible bonds of the self-healing functional groups are sufficiently dissociated and reformed, thereby ensuring self-healing efficiency. However, when the recovery temperature is below 80 ℃, the self-healing behavior does not proceed because it falls short of the activation energy for the dissociation and reformation of reversible bonds, and when the recovery temperature exceeds 120 ℃, thermal deformation of the polymer matrix itself occurs, resulting in behavior in which the original shape of the safety helmet shell is damaged.

[0041] Another aspect of the present invention relates to a safety helmet for safety inspection that protects the inspector's head.

[0042] A safety helmet according to another aspect of the present invention comprises (a) an outer shell and (b) a liner coupled to the inner side of the outer shell. The outer shell is formed of a self-healing polymer composite according to one aspect of the present invention, and the liner comprises a shape memory polymer, wherein the shape memory polymer deforms according to an external force when heated above a transformation temperature and maintains the deformed shape when cooled below the transformation temperature.

[0043] The above outer shell is formed of a self-healing polymer composite according to one aspect of the present invention, and even if microcracks occur due to external impact, ultraviolet rays, or moisture exposure while using the safety helmet, the cracks are restored by reversibly reforming the bonds through active heating by the user.

[0044] The above-mentioned liner is positioned between the inspector's head and the outer shell to cushion impact, and in the present invention, as the liner includes a shape-memory polymer, it can be deformed and fixed to fit the shape of the inspector's head. According to one embodiment, when the liner is heated above the transformation temperature while the inspector is wearing the safety helmet on their head, the liner is deformed by the external force applied by the inspector's head, and when cooled below the transformation temperature, the deformed shape is maintained.

[0045] According to one embodiment, the shape memory polymer of the liner comprises poly(ε-caprolactone), and the transformation temperature is 35-55 ℃.

[0046] When the shape memory polymer of the above-mentioned liner contains poly(ε-caprolactone) and the transformation temperature is 35-55°C, the liner deforms to fit the shape of the inspector's head without causing burns to the inspector's head skin in direct contact with the liner, even when the liner is heated above the transformation temperature while the inspector is wearing a safety helmet. However, when the transformation temperature is less than 35°C, the liner deforms near the inspector's body temperature and does not maintain the deformation to fit the head shape, and when the transformation temperature is greater than 55°C, behavior that can cause burns to the inspector's head skin is exhibited upon heating.

[0047] According to another embodiment, the safety helmet further includes a heating element embedded in the liner, and the heating element generates heat by electrical energy supplied from an external power source to heat the liner above the transformation temperature.

[0048] According to one embodiment, the heating element has a structure in which a heating wire, such as a nickel-chromium alloy wire, a copper-nickel alloy wire, or a carbon fiber, is embedded within a liner matrix and generates heat by electrical energy supplied through an external power terminal. As the heating element embedded in the liner generates heat by electrical energy supplied from an external power source and heats the liner above the transformation temperature, an inspector can heat the liner above the transformation temperature simply by connecting an external power source to the safety helmet without the need for a separate external heating device.

[0049] According to another embodiment, the safety helmet further includes a thermochromic indicator formed on the outer surface of the outer shell, and the thermochromic indicator changes color at a first discoloration temperature of 35-55 ℃ and a second discoloration temperature of 80-120 ℃, respectively.

[0050] According to one embodiment, the above-described thermochromic display is composed of a coating layer in which a reversible color-changing pigment or liquid crystal microcapsule is applied to the outer surface of the outer shell, and the color changes as the molecular structure or optical behavior of the reversible color-changing pigment or liquid crystal microcapsule changes reversibly according to the heating temperature. According to one embodiment, the above-described thermochromic display changes to a first color at a first color-changing temperature of 35-55 ℃ and further changes to a second color at a second color-changing temperature of 80-120 ℃.

[0051] As the above-mentioned thermochromic indicator exhibits multiple color change behaviors, it is visually confirmed that while the inspector heats the safety helmet to mold the liner to the head shape, the thermochromic indicator changes color only at the first color change temperature and has not reached the self-healing recovery temperature of the outer shell, and when the inspector further heats the safety helmet to self-heal cracks in the outer shell, it is visually confirmed that the thermochromic indicator additionally changes color at the second color change temperature and has reached the self-healing recovery temperature.

[0052] Another aspect of the present invention relates to a method for manufacturing a safety helmet for safety diagnosis inspection.

[0053] A manufacturing method according to another aspect of the present invention comprises the steps of: (A) forming an outer shell with a self-healing polymer composite; (B) forming a liner with a shape-memory polymer; and (C) bonding the liner to the inner side of the outer shell.

[0054] According to one embodiment, the outer shell molding of step (A) above is performed by molding a self-healing polymer composite powder or pellet into the shape of a safety helmet outer shell using a polymer molding process such as injection molding, compression molding, or vacuum thermoforming. According to one embodiment, the molding temperature of step (A) above is controlled to be above the glass transition temperature of the polymer matrix and below the reversible bond dissociation temperature of the self-healing functional group.

[0055] According to one embodiment, the liner molding in step (B) above is performed by molding shape memory polymer powder or pellets, such as poly(ε-caprolactone), into the shape of a safety helmet liner using an injection molding or compression molding process. According to one embodiment, the molding temperature in step (B) above is controlled to be above the transformation temperature of the shape memory polymer, so that the deformed shape is fixed by cooling after molding.

[0056] According to one embodiment, the bonding of the outer shell and the liner in step (C) above is performed by adhesive bonding by applying an adhesive, mechanical interlocking, or bonding using an interlocking member between the outer shell and the liner.

[0057] In the method for manufacturing a safety helmet according to the present invention, the step of forming an outer shell with a self-healing polymer composite and the step of forming a liner with a shape-memory polymer are performed separately. Consequently, even when the processing temperatures of the outer shell and the liner are different, each step proceeds independently without being affected by the processing temperatures of the other, thereby stably exhibiting both the self-healing behavior of the outer shell and the shape-memory behavior of the liner.

[0058] According to one embodiment, the manufacturing method further comprises, after step (C), (D) a step of deforming the liner to fit the shape of the user's head by pressing the safety helmet against the user's head while the liner is heated above the transformation temperature of the shape memory polymer, and (E) a step of fixing the deformed shape by cooling the liner below the transformation temperature.

[0059] As steps (D) and (E) above are added, the liner shape of the safety helmet manufactured by the present manufacturing method is provided in a fixed state after being deformed to fit the user's head shape, so that the user can use a safety helmet fitted to the user's head shape even if the user wears the safety helmet manufactured by the present manufacturing method as is without any separate additional shape fitting procedure.

[0060] According to a preferred embodiment, it is desirable to satisfy all of (i) to (iii) in that (i) the content of the self-healing polymer is 5-20 wt% based on the total weight of the self-healing polymer composite, (ii) the self-healing functional group includes a furan group and a maleimide group, and the reversible bond is a Diels-Alder reversible cyclization bond, and (iii) when the self-healing is performed at a recovery temperature of 80-120 ℃, the microcracks generated on the outer surface exhibit behavior in which they recover without a decrease in self-healing efficiency even after undergoing multiple heating self-healing cycles by active heating by the user, whereas if any one of (i) to (iii) is not satisfied, the behavior of efficiency stability of the multiple self-healing cycles is not observed.

[0061] According to another preferred embodiment, (iv) the shape memory polymer of the liner comprises poly(ε-caprolactone) and has a transformation temperature of 35-55°C, (v) a heating element embedded in the liner generates heat by the electrical energy of an external power source and heats the liner above the transformation temperature, and (vi) a thermochromic indicator formed on the outer surface of the outer shell changes color at a first color change temperature of 35-55°C and a second color change temperature of 80-120°C, respectively, so that when the inspector wears the safety helmet on their head and connects only an external power source to deform the liner to fit the shape of the head, a response is expressed in which the heating mode is visually separated into a liner deformation mode and an outer shell self-healing mode by the change of the thermochromic indicator, whereas if any one of (iv) to (vi) is not satisfied, the behavior of simultaneous expression of the self-heating + visual separation of heating modes is not observed. Therefore, it is preferable to satisfy all of (iv) to (vi).

[0062] According to a more preferred embodiment, it is desirable to satisfy all of the above (i) to (vi) in that when all of the above configurations (i) to (vi) are satisfied, the self-healing recovery behavior of the outer shell and the head-shaping deformation behavior of the liner are simultaneously manifested in a single safety helmet, and a response is manifested in which the two behaviors are visually perceived separately by the multiple color change of the thermochromic indicator, whereas when any one of the above (i) to (vi) is not satisfied, neither the simultaneous manifestation of the two behaviors within the single safety helmet nor the visual perception of separate behaviors is observed.

[0063] The present invention is to be explained in more detail below through examples, etc.; however, the scope and content of the present invention shall not be interpreted as being narrowed or limited by the examples, etc. below. Furthermore, based on the disclosure of the present invention including the examples below, it is evident that a person skilled in the art can easily practice the present invention even without specific experimental results presented, and it is natural that such variations and modifications fall within the scope of the appended claims.

[0064] Furthermore, the experimental results presented below describe only the representative experimental results of the above examples and comparative examples, and the respective effects of various embodiments of the present invention not explicitly presented below will be described in detail in the relevant sections.

[0065] Examples

[0066] Example 1: Fabrication of a safety helmet for safety diagnosis inspection

[0067] (1) Manufacture of self-healing polymer composite for outer skin

[0068] Specifically, 50 g of 4,4'-(trimethylene)dipiperidine-furfuryl alcohol adduct as a multiol monomer having a furan functional group and 30 g of 1,1'-(methylenedi-4,1-phenylene)bismaleimide as a crosslinking agent having a maleimide functional group were dissolved in 200 mL of 1,4-dioxane, and a self-healing polymer crosslinker was synthesized by forming Diels-Alder reversible cyclic bonds while magnetically stirring at 80 °C for 4 hours. 80 g of the above self-healing polymer crosslinker and 700 g of a polyurethane matrix (weight-average molecular weight approx. 250,000 g / mol) were dissolved in 1.5 L of N,N-dimethylformamide, and a homogeneous self-healing polymer composite dispersion was prepared by magnetically stirring at 65 °C for 1 hour (SHPC-10D). The content of the self-healing polymer crosslinker in the above dispersion was adjusted to about 10% by weight based on the total weight of the dispersion.

[0069] (2) Skin molding

[0070] The above self-healing polymer composite dispersion (SHPC-10D) was vacuum dried at 60°C for 24 hours to remove the solvent, and then a self-healing polymer composite powder (SHPC-10P) was obtained. The above powder was filled into an injection molding die shaped like a safety helmet shell, and then compression molded at a molding temperature of 70°C at a pressure of 50 MPa for 10 minutes to form a safety helmet shell with a thickness of about 4 mm.

[0071] (3) Liner molding

[0072] 500 g of poly(ε-caprolactone) powder (number average molecular weight approx. 80,000 g / mol) was filled into an injection molding die shaped like a safety helmet liner, and then compression molded at a molding temperature of 70 ℃ under a pressure of 30 MPa for 5 minutes to form a safety helmet liner with a thickness of approx. 8 mm. After molding, the safety helmet liner was cooled in a cooling chamber at 30 ℃ for 30 minutes to fix the deformed shape.

[0073] (4) Burial of heating element

[0074] A nickel-chromium alloy wire with a diameter of 0.2 mm (resistance value of approximately 4.5 Ω / m) was arranged in a grid pattern along the inner surface of the upper liner, and then poly(ε-caprolactone) powder was additionally applied to form a structure in which a heating element is embedded within the liner matrix. Both ends of the heating element were drawn out to the sides of the liner so that they could be connected to an external power terminal.

[0075] (5) Zion indicator coating

[0076] A thermochromic indicator coating solution was prepared by dispersing 10 g of a leuco-die microcapsule powder that changes from colorless to blue at 45 ℃ as a first color-changing pigment and 10 g of a leuco-die microcapsule powder that changes from blue to red at 100 ℃ as a second color-changing pigment in 100 mL of xylene solvent together with 80 g of polymethyl methacrylate binder. The above coating solution was applied to the outer surface of the stomach casing to a thickness of about 50 μm, and then dried at 50 ℃ for 2 hours to form a thermochromic indicator.

[0077] (6) Combination of outer shell and liner

[0078] After fitting and joining a liner with the heating element embedded therein to the inner side of the outer shell having the above-mentioned temperature indicator formed therein, a polyurethane-based adhesive was applied to the joint between the outer shell and the liner to integrate the outer shell and the liner.

[0079] Example 2: Adoption of different self-healing polymer contents

[0080] A safety helmet was manufactured using the same procedure as in Example 1, except that the content of the self-healing polymer crosslinker in the self-healing polymer composite dispersion (SHPC-10D) of Example 1 was changed from 10 wt% to 7 wt%.

[0081] Example 3: Adoption of different liner transformation temperatures

[0082] A safety helmet was manufactured using the same procedure as in Example 1, except that the number average molecular weight of the poly(ε-caprolactone) used in the liner of Example 1 was changed from 80,000 g / mol to 50,000 g / mol. The transformation temperature of the liner manufactured according to Example 3 was measured to be approximately 42 ℃.

[0083] Comparative Example 1: Self-healing polymer content 3 wt%

[0084] A safety helmet was manufactured using the same procedure as in Example 1, except that the content of the self-healing polymer crosslinker in the self-healing polymer composite dispersion (SHPC-10D) of Example 1 was changed from 10 wt% to 3 wt%.

[0085] Comparative Example 2: Self-healing polymer content 25 wt%

[0086] A safety helmet was manufactured using the same procedure as in Example 1, except that the content of the self-healing polymer crosslinker in the self-healing polymer composite dispersion (SHPC-10D) of Example 1 was changed from 10 wt% to 25 wt%.

[0087] Comparative Example 3: Liner transformation temperature less than 30 ℃

[0088] A safety helmet was manufactured using the same procedure as in Example 1, except that the poly(ε-caprolactone) used in the liner of Example 1 was replaced with another shape memory polymer having a transformation temperature of about 28°C.

[0089] Comparative Example 4: Liner transformation temperature exceeding 60 ℃

[0090] A safety helmet was manufactured using the same procedure as in Example 1, except that the poly(ε-caprolactone) used in the liner of Example 1 was replaced with another shape memory polymer having a transformation temperature of about 65°C.

[0091] Test Example 1: Evaluation of Self-Healing Efficiency for Skin Cracks

[0092] Outer shell specimens were taken from the safety helmets of Example 1 and Comparative Examples 1 and 2, and microcracks were induced in the specimens by tensile testing using a universal testing machine. After self-healing treatment by heating at 100°C for 30 minutes, a tensile test was performed again to measure the tensile strength before and after self-healing.

[0093] As a result of the test, the outer shell specimen of Example 1 had a tensile strength of approximately 45 MPa before self-healing, and after self-healing treatment at 100°C for 30 minutes, the tensile strength was measured to be approximately 40 MPa, resulting in a self-healing efficiency of approximately 88.9%. When the above self-healing cycle was repeated 10 times on the same specimen, the self-healing efficiency after 10 cycles was measured to be approximately 82.3%, confirming that the decrease in self-healing efficiency was minimal even with multiple cycles. Meanwhile, the outer shell specimen of Comparative Example 1 (self-healing polymer content 3 wt%) had a tensile strength of approximately 15 MPa after self-healing treatment, resulting in a self-healing efficiency of only about 33.3%. The outer shell specimen of Comparative Example 2 (self-healing polymer content 25 wt%) had a tensile strength of approximately 28 MPa before self-healing, which fell short of the mechanical strength (approximately 35 MPa or higher) required for a safety helmet outer shell.

[0094] Test Example 2: Evaluation of Liner Head Shape Fit Deformation

[0095] With the safety helmets of Examples 1 and 3 and Comparative Examples 3 and 4 worn on head models (three types with circumferences of approximately 56 cm, 58 cm, and 60 cm), an external power source was connected to the heating element embedded in the liner to heat the liner above the transformation temperature for 5 minutes, and then the external power source was cut off to allow natural cooling for 30 minutes.

[0096] As a result of the test, it was confirmed that the safety helmet of Example 1 (transformation temperature approximately 50°C) reached a liner surface temperature of approximately 52°C upon heating for 5 minutes, deformed to fit the shape of the head, and maintained the deformed shape after cooling. The safety helmet of Example 3 (transformation temperature approximately 42°C) completed the deformation to fit the head shape upon heating for approximately 3 minutes. Meanwhile, the safety helmet of Comparative Example 3 (transformation temperature approximately 28°C) did not maintain the fit to the head shape because the liner was deformed by the inspector's body temperature even without heating, and the safety helmet of Comparative Example 4 (transformation temperature approximately 65°C) reached a liner surface temperature of approximately 67°C upon heating for 5 minutes, forming an image-simulating pattern on the surface of the head model.

[0097] Test Example 3: Evaluation of Multiple Color Changes in the Zion Indicator

[0098] While heating the safety helmet of Example 1 stepwise in an external heating chamber, the color of the thermochromic indicator formed on the outer surface of the outer shell was photographed with a digital camera at 5°C intervals.

[0099] As a result of the test, the thermochromic indicator of Example 1 changed from colorless to blue when the internal temperature of the heating chamber reached approximately 45°C, and further changed from blue to red when the internal temperature of the external heating chamber reached approximately 100°C. After cooling the internal temperature of the heating chamber to below 30°C, the color of the thermochromic indicator reversibly returned to a colorless state. It was confirmed that due to this multiple color change behavior, an inspector can visually distinguish between the liner deformation mode (blue discoloration) and the outer shell self-healing mode (additional red discoloration) while heating the safety helmet.

[0100] Test Example 4: Evaluation of Shock Absorption Behavior

[0101] The safety helmet of Example 1 and a conventional standard safety helmet (a conventional polycarbonate outer shell + expanded polystyrene liner safety helmet without a self-healing outer shell + SMP liner) were each fitted onto a head model, and a 5 kg weight was dropped from a height of 1 m onto the top of the safety helmet to measure the impact acceleration using an acceleration sensor inside the head model.

[0102] As a result of the test, the initial impact acceleration of the safety helmet of Example 1 was measured to be approximately 65 g (based on gravitational acceleration). After forming artificial microcracks on the outer shell and performing a self-healing treatment at 100°C for 30 minutes, the same impact test was repeated, and the impact acceleration after self-healing was measured to be approximately 68 g, confirming that the impact absorption behavior was restored by the self-healing treatment. On the other hand, the conventional standard safety helmet, which had artificial microcracks formed in the same way, could not undergo self-healing treatment, and the impact acceleration increased by approximately twofold from approximately 70 g before the cracks occurred to approximately 145 g.

[0103] Test Example 5: Evaluation of Safety Helmet Service Life

[0104] For five samples each of the safety helmet of Example 1 and a conventional standard safety helmet, microcracks were generated in the outer shell by applying an intentional impact once a day for 30 days, and then the crack recovery and shock absorption behavior were evaluated through self-healing treatment.

[0105] As a result of the test, all five safety helmets of Example 1 recovered their cracks through self-healing treatment even after repeated impacts for 30 days, and their shock absorption behavior maintained the standard requirement level for safety helmets (less than 150 g), confirming that they were usable even after 30 days. On the other hand, five conventional standard safety helmets were disposed of after their shock absorption behavior was evaluated as failing to meet the safety grade due to outer shell cracks after an average of about 8 days.

[0106] Specific parts of the present invention have been described in detail above. It is evident to those skilled in the art that such specific descriptions are merely preferred embodiments and do not limit the scope of the invention. Accordingly, the actual scope of the invention is defined by the appended claims and their equivalents. Explanation of the symbols

[0107] 100: Safety helmet for safety inspection 200: Outer shell 210: Liner 220: Heating element 221: Heating wire 222: External power terminal 223: Control unit 230: Zion Mark Part 231: 1st discoloration layer 232: Second discoloration layer 300: Inspector Head

Claims

Claim 1 delete Claim 2 delete Claim 3 delete Claim 4 delete Claim 5 A safety helmet for safety inspection that protects the inspector's head, comprising: (a) an outer shell; and (b) a liner bonded to the inner side of the outer shell; wherein the outer shell is formed of a self-healing polymer composite, the self-healing polymer composite comprises a polymer matrix comprising polyurethane and a self-healing polymer dispersed in the polymer matrix, the content of the self-healing polymer is 5-20 weight% based on the total weight of the solid content of the self-healing polymer composite, the self-healing polymer has self-healing functional groups including furan groups and maleimide groups, and a Diels-Alder reversible cyclic bond is formed between the furan groups and the maleimide groups, the self-healing polymer composite has a self-healing ability in which the Diels-Alder reversible cyclic bond is reformed at 80-120 ℃ to recover cracks that have occurred in the outer shell, and the liner comprises a shape memory polymer including poly(ε-caprolactone), the shape memory polymer deforms according to an external force when heated above a transformation temperature of 35-55 ℃ and below the transformation temperature A safety helmet that maintains a deformed shape when cooled, and further comprises a heating element embedded in the liner and a thermochromic indicator formed on the outer surface of the outer shell, wherein the heating element generates heat by electrical energy supplied from an external power source to heat the liner above the transformation temperature, and the thermochromic indicator changes color at a first discoloration temperature of 35-55 ℃ and a second discoloration temperature of 80-120 ℃, respectively. Claim 6 delete Claim 7 delete Claim 8 delete Claim 9 A method for manufacturing a safety helmet for safety inspection according to claim 5, comprising: (A) a step of molding the outer shell with the self-healing polymer composite material; (B) a step of molding the liner with the shape memory polymer and embedding the heating element in the liner; (C) a step of forming the thermochromic indicator on the outer surface of the outer shell; and (D) a step of bonding the liner to the inner side of the outer shell. Claim 10 A method for manufacturing a safety helmet according to claim 9, further comprising, after step (D), (E) a step of deforming the liner to fit the shape of the user's head by pressing the safety helmet against the user's head while the liner is heated above the transformation temperature of the shape memory polymer; and (F) a step of fixing the deformed shape by cooling the liner below the transformation temperature.

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