Polyethylene pipe joint structure

Abstract

The utility model discloses a polyethylene pipe joint structure relates to the field of polyethylene pipe, is provided with a plurality of resistance band on the inner wall of joint pipeline, when two to be connected pipelines are connected with the both ends of joint pipeline, the outer wall of two to be connected pipelines and a plurality of resistance band contact each other, resistance band is along the radial direction of joint pipeline and is arranged, is provided with a plurality of through -holes on resistance band. This structure is provided with a plurality of through -holes on resistance band, and polyethylene material can form reticular connection through the through -hole of resistance band, and the mechanical compatibility and tensile capacity of pipe fitting joint are enhanced.

Description

Technical Field

[0001] This utility model relates to the field of polyethylene pipes, and specifically to a polyethylene pipe joint structure. Background Technology

[0002] Polyethylene (PE) pipe fittings are widely used in many fields such as water supply and drainage, gas transmission, and agricultural irrigation due to their numerous advantages, including corrosion resistance, wear resistance, good flexibility, and light weight. However, the connection problem of PE pipe fittings has always been a key factor affecting their performance and safety. Currently, common connection methods for PE pipe fittings mainly include butt fusion connection, electrofusion connection, and rubber ring sealing connection.

[0003] Butt fusion welding involves heating the ends of the polyethylene pipe fittings to a molten state, then quickly butt-joining them under pressure to fuse them together. This method offers advantages such as high connection strength and good sealing, but it requires specialized equipment and skilled technicians. Furthermore, improper control of parameters such as heating temperature, heating time, and butt-joining pressure during butt fusion welding can easily lead to defects such as bubbles and incomplete welds at the joint, thus affecting the connection strength and service life.

[0004] Electrofusion welding involves heating a resistance wire inside the fitting to melt the contact surface between the fitting and the pipe, thus achieving a connection. Electrofusion welding is relatively simple to operate, produces stable connection quality, and can adapt to various construction environments. However, electrofusion fittings are expensive, and the distribution and heating uniformity of the resistance wire can significantly affect the connection quality. Current electrofusion welding methods use a spirally wound heating wire within the fitting. This spiral arrangement is the root cause of the poor compressive strength and susceptibility to breakage at the polyethylene pipe connection. This is because the spirally wound heating wire creates a natural fracture layer between the fitting and the pipe, reducing connection strength and compressive strength.

[0005] Therefore, researching and developing a new connection method and technology, such as using a longitudinally arranged distribution structure of electric heating tape to improve the connection strength of polyethylene pipe fittings, has important practical significance and application value. Utility Model Content

[0006] One objective of this invention is to provide a polyethylene pipe joint structure that uses a resistance band along the radial direction of the joint pipe to heat and connect the joint pipe and two pipes to be connected, thereby increasing the compressive strength of the connection.

[0007] This objective is achieved using the following technical solution:

[0008] A polyethylene pipe joint structure includes two ends of a joint pipe for connecting two pipes to be connected, and a plurality of resistance strips are provided on the inner wall of the joint pipe. The resistance strips are arranged in the radial direction of the joint pipe. When the two pipes to be connected are connected to the two ends of the joint pipe, the outer walls of the two pipes to be connected are in contact with the plurality of resistance strips.

[0009] The existing joint assembly uses a spirally wound heating wire inside the joint fitting. The resistance wire is a linear heating element. During spiral winding, uneven spacing and poor contact can easily lead to local overheating or insufficient heating (such as low temperature at the spiral spacing and high temperature at the resistance wire contact point), resulting in uneven melting areas and affecting the connection strength.

[0010] The existing joint assembly forms a continuous circumferential weak zone inside the joint fitting by spirally winding an electric heating wire. After the welding and cooling, the electric heating wire and the polyethylene matrix are physically separated, and the stress is concentrated and released along the spiral line, forming a natural fracture path.

[0011] In this structure, several resistance bands are arranged radially, dividing the connection area of ​​the inner wall of the pipe joint into multiple independent units. When external stress is transmitted to the resistance bands, it is dispersed into each independent block, avoiding the formation of continuous paths. Furthermore, the stress transmission path is blocked by the non-closed ring structure. Therefore, compared with existing structures, this structure can effectively improve the compressive strength of the pipe joint.

[0012] Furthermore, the resistance band has several through holes. When the resistance band is heated, the connector pipe and the two pipes to be connected are all made of polyethylene. When the resistance band is energized, it heats the connector pipe and the two pipes to be connected, causing the polyethylene material of the connector pipe and the two pipes to be connected to melt. The polyethylene material passes through the several through holes on the resistance band, allowing the polyethylene material of the connector pipe and the two pipes to be connected to pass through the through holes. After cooling, the connector pipe and the two pipes to be connected are fused together, further enhancing the mechanical compatibility and tensile strength of the connector pipe.

[0013] Furthermore, a heat-shrinkable material layer is provided between the resistance band and the inner wall of the connector pipe. The heat-shrinkable material is a polymeric shape memory material (such as polyethylene or polyolefin), which transforms a linear structure into a network structure through radiation cross-linking, possessing the characteristic of "high-temperature shrinkage." It expands and sets when heated to a highly elastic state, and retains its shape after cooling; upon reheating, it shrinks and returns to its original shape, with a shrinkage rate reaching 50%-80%.

[0014] Preferably, a hot melt adhesive layer is provided between the heat-shrinkable material layer and the joint pipe. The hot melt adhesive melts and becomes sticky when heated, and solidifies and bonds upon cooling; its main function is interfacial bonding.

[0015] Heat-shrinkable material is a product of polyethylene through radiation cross-linking. When heated by a resistance band, the heat-shrinkable material shrinks radially, restoring its original diameter and tightly wrapping around the two pipes to be connected. After shrinking, the heat-shrinkable material forms a seamless fit with the joint pipe and the two pipes to be connected, preventing the intrusion of oxygen or corrosive media. The shrunken heat-shrinkable material forms a rigid / semi-rigid protective layer to resist external impacts. For the joint pipes, the shrinking heat-shrinkable material tightens the polyethylene material at the joint pipe, enhancing the connection strength.

[0016] The resistance band is a heating element that generates heat through resistance. Heat-shrink tubing covers the resistance band and shrinks upon heating, forming an insulating barrier to prevent contact between the resistance band and external conductors. The heat from the resistance band facilitates the shrinkage of the heat-shrink material, which then tightly secures the resistance band to the two pipes to be connected, preventing displacement.

[0017] Hot melt adhesive is a thermoplastic resin (such as EVA) that melts into a liquid state when heated, and then undergoes physical adsorption and chemical bonding with polar groups (such as hydroxyl groups) on the surface of the joint pipe. Hot melt material can also fill minor defects, such as scratches and dents, on the surfaces of the joint pipe and the two pipes to be connected, forming a sealing layer to further prevent media leakage at the interface during use.

[0018] When energized, the resistance band heats up to 150-200℃, melting the surrounding hot-melt material and polyethylene material to achieve welding. The heat from the resistance band melts the hot-melt material, causing it to adhere to the surface of the resistance band or the joint pipe and the two pipes to be connected, thus fixing the position of the resistance band. After melting, the hot-melt material forms a composite structure with the resistance band and polyethylene material, enhancing the tensile strength of the resistance band. Simultaneously, the molten hot-melt material and polyethylene material interweave through the through-holes in the resistance band, further improving the stability of the connection and increasing the tensile strength of the interface.

[0019] Therefore, the resistance band is arranged radially along the connector pipe, and the heat is released by the Joule heat generated by the current passing through the conductor after energization. The design of several through holes on the surface of the connector pipe allows heat to be transferred evenly to both the inner and outer sides, avoiding local overheating or uneven heat distribution, and ensuring that the heat field covers the entire connection area.

[0020] During the heating process of the resistance band, a large amount of heat is generated. Polyethylene has a certain coefficient of thermal expansion, and it will expand during heating. The material of the resistance band should also have a similar coefficient of thermal expansion to avoid stress concentration and interface separation caused by excessive differences in thermal expansion. If the coefficients of thermal expansion of the resistance band and the polyethylene pipe differ significantly, cracks may occur at the connection interface during heating and cooling cycles, thereby reducing the connection strength.

[0021] The heat-shrinkable material layer is located between the resistance band and the inner wall of the connector pipe. When heated, the temperature of the heat-shrinkable material layer needs to reach its softening point, such as approximately 80-120℃ for EVA-based heat-shrinkable materials. The heat-shrinkable material will shrink radially. This shrinkage force, on the one hand, tightly presses the resistance band onto the two pipes to be connected, enhancing heat conduction efficiency; on the other hand, it physically squeezes out air at the interface, initially forming a sealed structure, creating a closed environment for the subsequent flow and filling of hot melt adhesive.

[0022] The hot melt adhesive layer, such as polyethylene-based hot melt adhesive, is located between the heat-shrinkable material layer and the connector pipe. Its melting point is typically lower than that of polyethylene, which has a melting point of 130-150°C. When the resistance band is heated above the hot melt adhesive's melting point, it melts rapidly and becomes fluid. The shrinkage pressure of the heat-shrinkable material layer fills the tiny gaps between the connector pipe and the outer walls of the two pipes to be connected, achieving physical wetting of the interface. Simultaneously, the molten hot melt adhesive diffuses and partially cross-links with the polyethylene material at the molecular level, forming a dual bonding force of mechanical interlocking and chemical adhesion.

[0023] As heat continues to transfer, the inner layer of the joint pipe and the outer layers of the two pipes to be connected gradually melt. At this point, the polyethylene material of the joint pipe and the two pipes to be connected forms a continuous phase with the molten hot melt adhesive. After cooling, they solidify together into a homogeneous whole, transforming the mechanical connection of the joint pipe and the two pipes to be connected into a molecular-level connection, ultimately achieving a balance between structural strength and sealing performance.

[0024] This structure, through the chemical bonding of hot melt adhesive and the melt blending of polyethylene material, achieves an interfacial strength between the joint pipe and the two pipes to be connected that approaches or even exceeds the strength of the substrate itself, enabling it to withstand higher axial tensile and radial compressive forces. Simultaneously, the synergistic effect of the multi-layered materials disperses stress concentration, making it less prone to interfacial cracking due to vibration or temperature changes during long-term use, and exhibiting significantly better fatigue resistance than traditional joints.

[0025] Heat-shrinkable materials solve macroscopic sealing problems, while hot melt adhesives solve microscopic interface sealing problems. This structure effectively blocks the penetration of water, gas, and corrosive media, making it suitable for harsh environments such as underground and underwater applications. Furthermore, both polyethylene and hot melt adhesives have good chemical inertness, and are not prone to swelling or degradation during long-term contact with media.

[0026] Compared to traditional hot-melt or electrofusion connections, this structure achieves plug-and-play functionality through a built-in resistance band. Simply insert the two pipes to be connected into the ends of the connector, apply electricity for heating, and the connection is complete. No complex alignment or pressure control is required, reducing reliance on the skills of the installers. Furthermore, the through-hole design of the resistance band and the flexible shrinkage of the heat-shrink material can accommodate minor misalignments during pipe insertion, improving the tolerance for errors during on-site installation.

[0027] Furthermore, the resistance strip is arranged in a Z or S pattern along the radial direction of the joint pipe. First, the resistance strip is laid in a Z or S pattern along the radial direction of the joint, and the coverage area is much larger than that of a single resistance wire. Heat is evenly diffused radially through the strip structure, avoiding local hot spots.

[0028] Preferably, the resistance band and the inner wall of the connector pipe are located on the same curved surface. The resistance band and the inner wall of the connector pipe have the same curvature, and after welding, full-surface molecular chain entanglement is achieved, with no air gaps or delamination (traditional spiral wires have line contact with the pipe wall). Several resistance bands are evenly distributed in the circumferential direction of the inner wall of the connector pipe.

[0029] Compared with the prior art, this utility model has the following advantages and beneficial effects:

[0030] This utility model discloses a polyethylene pipe joint structure. The radial resistance band of this structure is a planar heating body, which has a larger coverage area and more sufficient contact with the material. At the same time, the through-hole design on the resistance band can form a heat transfer channel, allowing heat to diffuse to the surroundings through the through-holes, avoiding local heat accumulation, and achieving uniform heating in the circumferential and radial directions of the joint. This ensures that the polyethylene material of the joint pipe and the two pipes to be connected, as well as the hot melt adhesive and heat shrink material, melt synchronously and mix evenly, reducing defects such as bubbles and incomplete fusion.

[0031] In existing resistance wire winding structures, the resistance wire itself is a metallic foreign object, which is prone to forming linear weak areas at the interface after melting. The difference in thermal expansion coefficients between the resistance wire and polyethylene may lead to microcracks.

[0032] This structure, with several through holes in the resistance band, allows polyethylene material to form a mesh-like connection through these holes, enhancing the mechanical compatibility and tensile strength of the pipe fittings. Since the polyethylene pipe connection points need to withstand certain mechanical loads, such as tension, bending, and shear forces, the good mechanical compatibility between the resistance band and the polyethylene pipe fittings ensures they work together under stress. The flexibility and strength of the resistance band are matched with the polyethylene pipe fittings, preventing connection quality issues caused by excessively hard or soft heating tape. Furthermore, the penetrating connection between the resistance band structure and the longitudinally arranged polyethylene pipe fittings provides a stronger bond, ensuring no relative slippage or separation occurs under stress.

[0033] In addition, through the synergistic effect of the heat-shrinkable material layer and the hot melt adhesive material layer, the heat-shrinkable material layer shrinks inward due to the heat-shrink effect when heated, applying radial pressure to the molten polyethylene material and the outer wall of the pipe, promoting the tight adhesion of the materials; the hot melt adhesive material layer melts after heating, filling the tiny gap between the joint pipe and the two pipes to be connected, and undergoes chemical compatibility bonding with the polyethylene material, that is, the hot melt adhesive molecular chains and the polyethylene molecular chains entwine and diffuse, forming a gradient transition interface rather than a rigid boundary;

[0034] Meanwhile, the through holes in the resistance band allow the molten hot melt adhesive and polyethylene to permeate each other through the through holes, further enhancing the interfacial bonding and improving the overall sealing and anti-leakage capabilities.

[0035] This structure organically combines physical sealing, chemical bonding, and material melting through a multi-stage process involving resistance heating, shrinkage of heat-shrinkable materials, melting of hot melt adhesive, and blending with polyethylene. This solves the problem of insufficient strength in traditional mechanical connections while overcoming the complexity of single hot melt connections. This structure achieves a balance of high strength, high sealing performance, and high construction efficiency with a low-cost material combination, making it particularly suitable for scenarios with stringent requirements for connection reliability, such as municipal water supply and drainage, gas transmission, and chemical pipelines, and has broad engineering application prospects. Attached Figure Description

[0036] The accompanying drawings, which are included to provide a further understanding of the embodiments of the present invention and form part of this application, do not constitute a limitation thereof. In the drawings:

[0037] Figure 1 This is a schematic diagram of the joint pipe structure;

[0038] Figure 2 This is a schematic diagram of a structure in which the resistance band is arranged in a Z-shape along the radial direction of the connector pipe;

[0039] Figure 3 This is a schematic diagram of a structure in which the resistance band is arranged in an S-shape along the radial direction of the connector pipe;

[0040] Figure 4 This is a schematic diagram of the structure after the first pipe, the second pipe, and the joint pipe are connected in Example 3;

[0041] Figure 5 A schematic diagram of a structure in which six resistance bands are evenly arranged around the circumference of the connector pipe.

[0042] The attached diagram shows the markings and corresponding component names:

[0043] 1-Connector pipe, 2-Resistor strip, 3-Heat shrink material layer, 4-Hot melt adhesive material layer, 5-Terminal, 6-First pipe, 7-Second pipe, 8-Through hole. Detailed Implementation

[0044] To make the objectives, technical solutions, and advantages of this utility model clearer, the present utility model will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of this utility model are only used to explain this utility model and are not intended to limit this utility model.

[0045] In the description of this utility model, it should be understood that the terms "front", "rear", "left", "right", "up", "down", "vertical", "horizontal", "high", "low", "inner", and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting the scope of protection of this utility model.

[0046] Example 1

[0047] like Figure 1 As shown, a polyethylene pipe joint structure includes a joint pipe 1 with two ends for connecting two pipes to be connected. Both ends of the joint pipe 1 have connection areas. The two pipes to be connected are a first pipe 6 and a second pipe 7. When the first pipe 6 and the second pipe 7 are connected to the two ends of the joint pipe 1, they are connected to the connection areas of the joint pipe 1. Both pipes to be connected and the joint pipe 1 are made of polyethylene.

[0048] Several resistance bands 2 are provided in the connection areas at both ends of the connector pipe 1. The resistance bands 2 are arranged along the radial direction of the connector pipe 1, and several through holes 8 are provided on the resistance bands 2. When the first pipe 6 and the second pipe 7 are respectively connected to the two ends of the connector pipe 1, the first pipe 6 and the second pipe 7 are in contact with the resistance bands 2.

[0049] When using, fix the connector pipe 1 on the workbench or bracket, keeping it horizontal. Insert the first pipe 6 and the second pipe 7 into both ends of the connector pipe 1, ensuring that the first pipe 6 and the second pipe 7 are inserted to the required depth and that the resistance band 2 is in full contact with the outer walls of the first pipe 6 and the second pipe 7.

[0050] A terminal 5 is provided on the connector pipe 1. The output cable of the electrofusion welding machine is connected to the terminal 5 on the connector pipe 1, ensuring correct polarity. Power is supplied through the terminal 5, causing the resistance band 2 to heat up to the melting point of polyethylene, i.e., 130-150℃. During the heating process, molten polyethylene flows through the through holes, filling gaps and improving sealing. The through holes 8 ensure uniform heat transfer and prevent localized overheating; the molten material interpenetrates through the through holes, forming molecular-level bonds.

[0051] After power is cut off, keep the pipes stationary and allow them to cool naturally in the connection area to solidify the fusion layer, thus achieving the connection between the first pipe 6 and the second pipe 7 and the joint pipe 1.

[0052] Example 2

[0053] Based on Example 1, the resistor strip 2 and the inner wall of the connector pipe 1 are located on the same curved surface.

[0054] Several resistance bands 2 are evenly distributed along the circumferential direction of the inner wall of the connector pipe 1. There is a gap between two adjacent resistance bands 2 on the inner wall of the connector pipe 1.

[0055] In some embodiments, the resistance band is arranged in a Z-shape along the radial direction of the connector pipe, such as... Figure 2 As shown.

[0056] In some embodiments, the resistance band is arranged in an S-shape along the radial direction of the connector pipe, such as... Figure 3 As shown.

[0057] When the resistance band is energized, it generates heat. If the gap between the resistance bands is too small, the heat will concentrate, causing the polyethylene to burn, degrade, or bubble. If the gap is too large, the heat will not dissipate sufficiently, creating cold areas. The molten adhesive cannot flow fully, and the connection strength will decrease.

[0058] The resistance bands should be set in a Z or S pattern to increase the heating path length. The gaps must match the curvature to ensure uniform heating of the entire inner wall surface. A gap of 5-10mm can balance heat conduction efficiency and avoid hot or cold spots.

[0059] Example 3

[0060] Based on the above embodiments, such as Figure 4 As shown, a heat-shrinkable material layer 3 is provided between the resistance band 2 and the inner wall of the connector pipe 1. A hot melt adhesive material layer 4 is provided between the heat-shrinkable material layer 3 and the connector pipe 1. The first pipe 6, the second pipe 7, and the connector pipe 1 are all made of polyethylene. The thickness of the resistance band 2 is 0.1-0.3 mm. The heat-melting temperature of polyethylene (PE) is usually 130-150℃, and the resistance band needs to reach this temperature range quickly through Joule heating. If it is greater than 0.3 mm, it will be too thick, resulting in increased heat capacity, slow heating, and possibly affecting the adhesion to the inner wall of the pipe due to excessive rigidity; if it is less than 0.1 mm, it will be too thin, with an excessively high resistance value, making it easy to burn out or cause localized overheating.

[0061] The resistor strip is made of nickel-chromium alloy (NiCr) or copper-nickel alloy (constantan), which has low resistivity, ensuring heating efficiency and good ductility, so as to better fit curved surfaces.

[0062] The width of resistor strip 2 is 5-10mm. This width is not the overall width of the resistor strip, but the width when arranged in a Z or S pattern. The width needs to balance heat uniformity and ease of installation. When the width of the resistor strip is less than 5mm, it will cause local heat concentration; when it is greater than 10mm, it is too wide, which increases the difficulty of bending when arranged in a Z or S pattern, and is prone to stress cracking due to uneven thermal expansion.

[0063] In some embodiments, the thickness of the heat-shrinkable material layer is 0.8-1.5mm. As an isolation layer between the resistor strip and the hot melt adhesive layer, the heat-shrinkable material layer has the first function of insulation to prevent short circuit of the resistor strip, the second function of heat conduction to transfer heat to the hot melt adhesive, and the third function of mechanical protection and buffering the friction between the resistor strip and the joint pipe.

[0064] The thermal conductivity of the heat-shrinkable material layer is approximately 0.2~0.3 W / (m·K). Excessive thickness of the heat-shrinkable material reduces heat transfer efficiency, leading to a prolonged melting time for the hot melt adhesive. Cross-linked polyethylene (XLPE) or polyolefin heat-shrinkable materials are preferred for the heat-shrinkable material layer, with a shrinkage temperature of 80-120℃, lower than the melting point of polyethylene, ensuring pre-shrinkage and shaping are completed before the resistance band heats up.

[0065] The thickness of the hot melt adhesive material layer is 1.0-2.0 mm. After melting, it fills the gaps between the first pipe, the second pipe, and the joint pipe, forming a seal and structural connection. If it is too thick, it will lead to a longer cooling and curing time, and the adhesive layer is prone to internal stress due to uneven heat dissipation. The preferred hot melt adhesive material layer is ethylene-vinyl acetate (EVA) based hot melt adhesive to ensure the melt viscosity.

[0066] When using, remove the oxide layer on the inner wall of the first pipe, the second pipe, and the joint pipe with sandpaper or a special scraper to expose the fresh PE surface; wipe the surface oil with anhydrous ethanol to ensure the wettability of the hot melt adhesive with PE (contact angle <30°).

[0067] Using an adjustable temperature DC power supply, connect the resistor strip via terminals and employ a stepped heating method. Initially, raise the temperature to 80 degrees Celsius and hold for 8 minutes, then raise it to 150 degrees Celsius and hold for 5 minutes. Disconnect the power supply and allow it to cool naturally to below 60 degrees Celsius. Complete the connection of the first pipe, the second pipe, and the connector pipe.

[0068] Example 4

[0069] Based on the above embodiments, the components after connecting the first pipe, the second pipe and the joint pipe in embodiments 1-3 are subjected to performance tests of compressive strength, circumferential peel force and thermal cycle life.

[0070] The compressive strength test verifies the maximum pressure-bearing capacity and sealing performance by gradually increasing the pressure until the joint fails. During the test, after the first and second pipes are connected to the joint pipe, the internal air is purged, and the pressure is gradually increased until the joint fails to obtain the compressive strength of the specimen.

[0071] The circumferential peel force test simulates circumferential stress to detect the peel resistance of the joint interface. The joint pipe is horizontally fixed to a tensile testing machine, and a clamp is installed at the circumferential joint. A uniform tensile force is applied along the circumferential direction (perpendicular to the pipe axis), and the peak peel force is recorded. It is then observed whether the peel occurs at the adhesive layer or the metal / plastic bond.

[0072] Thermal cycling life is assessed by simulating environmental changes through temperature cycling to evaluate the fatigue resistance of the joint. A single cycle consists of 30 minutes at low temperature, 30 minutes at high temperature, and 30 minutes returning to room temperature, for a total duration of 90 minutes; the number of cycles is ≥1000. Pressure synchronization is achieved by applying a pulse pressure 1.33 times the working pressure during the temperature cycling. Leakage is checked after each cycle, and an airtightness test is performed at the end of the cycle.

[0073] The first component is obtained by heating and connecting the first and second pipes through a spiral winding of resistance wire;

[0074] In Example 1, the resistor strip is rectangular, and the second component is obtained by heating and connecting the first and second pipes;

[0075] In Example 2, the resistor strip is S-shaped, and the third component is obtained by heating and connecting the first and second pipes;

[0076] In Example 3, the resistor strip is S-shaped, and a heat-shrinkable material layer 3 is provided between the resistor strip 2 and the inner wall of the connector pipe 1. A hot melt adhesive material layer 4 is provided between the heat-shrinkable material layer 3 and the connector pipe 1. The first pipe and the second pipe are heated and connected to obtain the fourth component.

[0077] The first, second, third, and fourth components were subjected to performance tests for compressive strength, circumferential peel force, and thermal cycling life. The test results are shown in Table 1.

[0078] Table 1

[0079]

[0080] The second component has a rectangular resistance band with uneven heat distribution. Overheating at the edges leads to polyethylene degradation, while insufficient melting in the central region creates a weak bonding zone. The molten polymer has poor fluidity, and pores easily exist at the interface. Therefore, its compressive strength is higher than the first component but lower than the third and fourth components, which have the lowest strength. Furthermore, stress concentration occurs at the right angles of the rectangular resistance band in the second component, and crack propagation easily occurs at the edges of the through-holes. Thus, weak points in the fusion zone result in a tortuous peeling path with low strength. The second component exhibits oxidative embrittlement in locally overheated areas, and high residual stress at the through-holes. During thermal cycling, differences in thermal expansion coefficients cause surface microcracks, which propagate rapidly and lead to leakage. Therefore, the performance of the second component is higher than the first component but worse than the third and fourth components.

[0081] The resistance band of the third component is S-shaped. The S-shaped path extends the heat conduction distance, resulting in a more uniform temperature distribution. The through-holes promote interpenetration of molten polyethylene. Molecular chain entanglement is more complete, interfacial continuity is improved, and compressive strength is significantly increased. The S-shaped curve of the third component disperses circumferential stress, and the through-holes become channels for molten material flow, increasing the effective bonding area. Furthermore, the uniform melting of the third component reduces initial defects, and the S-shaped interface slows down crack propagation.

[0082] The heat-shrinkable layer of the fourth component contracts radially and is pressurized when heated. Hot melt adhesive fills the through-holes and interfacial micro-gaps in the resistance band. After curing, the modulus of the hot melt adhesive is higher than that of polyethylene, synergistically enhancing overall rigidity. The hot melt adhesive layer co-crystallizes with polyethylene, forming a transition layer; the heat-shrinkable layer provides continuous clamping force, inhibiting interfacial peeling and cracking. Peeling failure requires penetration through all three layers, resulting in the greatest energy consumption. The heat-shrinkable layer acts as a stress buffer, absorbing the deformation energy of PE; the hot melt adhesive layer seals pores, blocking oxygen and inhibiting thermal oxidation aging. The three-layer structure achieves a gradient transition in thermal expansion, thus significantly improving lifespan.

[0083] Example 5

[0084] Based on the above embodiments, the first pipe, the second pipe, and the connector pipe are all made of polyethylene. The first pipe and the second pipe are respectively connected to the two ends of the connector pipe. Several resistance bands are provided in the connection areas at both ends of the connector pipe, and the resistance bands are arranged radially along the connector pipe, with several through holes on each resistance band. A heat-shrinkable material layer is provided between the resistance band and the inner wall of the connector pipe, and a hot melt adhesive material layer is provided between the heat-shrinkable material layer and the connector pipe. When the first pipe and the second pipe are respectively connected to the two ends of the connector pipe, the first pipe and the second pipe are in contact with the resistance bands. The resistance bands are S-shaped, and the overall arc width of the resistance band is one-seventh of the circumference of the inner diameter of the connector pipe 1. Six resistance bands are evenly arranged circumferentially on the connector pipe. Figure 5 As shown, the spacing between two adjacent resistor strips is the same. Energizing the resistor strips completes the connection of the first pipe, the second pipe, and the connector pipe, resulting in the fifth component.

[0085] The first pipe, the second pipe, and the connector pipe are all made of polyethylene. The first and second pipes are connected to the two ends of the connector pipe, respectively. Several resistance bands are provided in the connection areas at both ends of the connector pipe, arranged radially along the connector pipe, and each resistance band has several through holes. A heat-shrinkable material layer is placed between the resistance band and the inner wall of the connector pipe, and a hot-melt adhesive layer is placed between the heat-shrinkable material layer and the connector pipe. When the first and second pipes are connected to the two ends of the connector pipe, they are in contact with the resistance bands. The resistance bands are S-shaped, and the overall arc width of the resistance band is one-eighth of the circumference of the inner diameter of connector pipe 1. Seven resistance bands are evenly arranged circumferentially on the connector pipe, with equal spacing between adjacent resistance bands. Energizing the resistance bands completes the connection of the first pipe, the second pipe, and the connector pipe, resulting in the sixth component.

[0086] The first pipe, the second pipe, and the connector pipe are all made of polyethylene. The first pipe and the second pipe are respectively connected to the two ends of the connector pipe. Several resistance bands are provided in the connection area at both ends of the connector pipe, arranged radially along the connector pipe, and each resistance band has several through holes. A heat-shrinkable material layer is placed between the resistance band and the inner wall of the connector pipe, and a hot melt adhesive layer is placed between the heat-shrinkable material layer and the connector pipe. When the first pipe and the second pipe are connected to the two ends of the connector pipe, they are in contact with the resistance bands. The resistance bands are S-shaped, and their overall width is one-fifth of the circumference of the inner diameter of connector pipe 1. Four resistance bands are evenly arranged circumferentially on the connector pipe, with equal spacing between adjacent resistance bands. The resistance bands are energized to complete the connection of the first pipe, the second pipe, and the connector pipe, resulting in the seventh component.

[0087] The first pipe, the second pipe, and the connector pipe are all made of polyethylene. The first pipe and the second pipe are respectively connected to the two ends of the connector pipe. Several resistance strips are provided in the connection area at both ends of the connector pipe. The resistance strips are arranged along the radial direction of the connector pipe and have several through holes. A heat-shrinkable material layer is provided between the resistance strip and the inner wall of the connector pipe, and a hot melt adhesive material layer is provided between the heat-shrinkable material layer and the connector pipe. When the first pipe and the second pipe are respectively connected to the two ends of the connector pipe, the first pipe and the second pipe are in contact with the resistance strips. The resistance strips are S-shaped, and the overall width of the resistance strips is one-quarter of the circumference of the inner diameter of the connector pipe (1). Three resistance strips are evenly arranged in the circumferential direction of the connector pipe, and the spacing between two adjacent resistance strips is the same. The resistance strips are energized to complete the connection of the first pipe, the second pipe, and the connector pipe, resulting in the eighth component.

[0088] The compressive strength of components five, six, seven, and eight was tested, and the results are shown in Table 2.

[0089] Table 2

[0090]

[0091] The fifth and sixth components exhibit the highest relative compressive strength. The sixth component, with its numerous, uniformly distributed, and closely spaced resistance bands, provides dense support points. Upon heating, the heat-shrinkable material and hot-melt adhesive melt uniformly, forming a continuous and robust fusion layer. Furthermore, the curved design of the S-shaped resistance bands helps disperse stress, reducing the risk of localized deformation. The fusion interface of polyethylene exhibits higher crystallinity under uniform heating, enhancing overall rigidity.

[0092] The seventh component has moderate compressive strength. While the number of resistance bands is reduced, their width is increased, resulting in fewer support points and larger gaps. Although the wider resistance bands provide a larger heating area and enhance local fusion strength, circumferential uniformity decreases. Under compressive loads, stress may concentrate in the area between the resistance bands, leading to a slightly lower compressive strength than the fifth component.

[0093] The eighth component has the lowest relative compressive strength, the fewest resistance bands, and the largest width, which amplifies circumferential non-uniformity. The large gaps result in sparse support points, potentially leading to uneven heat distribution and creating weak points during heating. In compression tests, the load tends to concentrate at a few wide resistance bands, causing localized buckling or interfacial cracking. Furthermore, the low crystallinity of polyethylene material under non-uniform fusion further reduces its strength.

[0094] Therefore, the sixth component outperforms the fifth component, and the sixth component outperforms both the seventh and eighth components. The core reason is the dominant effect of the number of resistance bands on the support density; more resistance bands can better simulate continuous ring-shaped supports, reducing stress concentration.

[0095] The terms "first," "second," and "third" used in this document are merely for clarity of description and are not intended to restrict any order or emphasize importance. Furthermore, the term "connection" used in this document, unless otherwise specified, can refer to a direct connection or an indirect connection via other components.

[0096] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of this utility model. It should be understood that the above description is only a specific embodiment of this utility model and is not intended to limit the scope of protection of this utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this utility model should be included within the scope of protection of this utility model.

Claims

1. A polyethylene pipe joint structure, characterized in that, The two ends of the connector pipe (1) are used to connect two pipes to be connected. Several resistance bands (2) are provided on the inner wall of the connector pipe (1). When the two pipes to be connected are connected to the two ends of the connector pipe (1), the outer walls of the two pipes to be connected are in contact with the several resistance bands (2). The resistance band (2) is arranged in the radial direction of the connector pipe (1), and several through holes (8) are provided on the resistance band (2).

2. The polyethylene pipe joint structure according to claim 1, characterized in that, The resistance band (2) is arranged in a Z-shape along the radial direction of the joint pipe (1).

3. The polyethylene pipe joint structure according to claim 1, characterized in that, The resistor strip (2) and the inner wall of the connector pipe (1) are located on the same curved surface.

4. The polyethylene pipe joint structure according to claim 1, characterized in that, Several resistance bands (2) are evenly distributed in the circumferential direction of the inner wall of the joint pipe (1).

5. A polyethylene pipe joint structure according to claim 1, characterized in that, A heat-shrinkable material layer (3) is provided between the resistor strip (2) and the inner wall of the connector pipe (1).

6. A polyethylene pipe joint structure according to claim 5, characterized in that, A hot melt adhesive layer (4) is provided between the heat shrinkable material layer (3) and the joint pipe (1).

7. A polyethylene pipe joint structure according to claim 1, characterized in that, Both pipes to be connected and the connector pipe (1) are made of polyethylene.

8. A polyethylene pipe joint structure according to claim 1, characterized in that, The thickness of the heat-shrinkable material layer (3) is 0.8-1.5 mm, and the thickness of the hot melt adhesive material layer (4) is 1.0-2.0 mm.

9. A polyethylene pipe joint structure according to claim 1, characterized in that, There is a gap between two adjacent resistance bands (2) on the inner wall of the connector pipe (1).

10. A polyethylene pipe joint structure according to claim 1, characterized in that, The resistance band (2) is set in an S-shape along the radial direction of the joint pipe (1).

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