A method of injection molding a heteronaphthalene-coupled poly(arylene ether ketone) material

Abstract

The application discloses a kind of injection molding methods of hetero-naphthalene biphenyl poly (aryl ether ketone) material, and relates to the technical field of polymer processing. Including the following steps: hetero-naphthalene biphenyl poly (aryl ether ketone) material is dried, after drying, melt is obtained by being added into injection molding machine cylinder and being melt plasticized, wherein the temperature of cylinder is controlled by being segmented and raised along the feeding direction;Melt is injected into mold cavity by using multi-stage injection mode;Pressure is applied to the melt in the mold cavity and cooled to set, and after demolding, the material is heat treated and cooled to obtain high-performance hetero-naphthalene biphenyl poly (aryl ether ketone) product. By optimizing the synergistic relationship between key process parameters, the overall performance of the product is significantly improved. The key technical problems such as poor plasticizing quality, internal stress concentration and unstable mechanical properties in traditional injection molding are solved, and it has good industrial application prospect.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high polymer material processing, in particular to a kind of injection molding method of poly (phthalazinone ether ketone) material. BACKGROUND

[0002] Among poly (aryl ether ketone) high-performance engineering plastics, poly (phthalazinone ether ketone) (PPEK) has broad application prospects in aerospace, electronics and electrical equipment and other fields due to its excellent high-temperature resistance, outstanding mechanical strength and good chemical stability. However, the injection molding process of PPEK is still in its early stages of development, and its process parameters and experience system are not yet mature. In actual production, the processing method of mature engineering plastics such as poly (ether ether ketone) (PEEK) with similar structure is mainly used for reference.

[0003] Due to the stronger rigidity of PPEK molecular chain and the significant difference in melt characteristics and thermal behavior, this experience transplantation exposes a series of outstanding problems in the production process. First, the high melt viscosity and poor flowability of PPEK make injection filling difficult, and obvious weld lines are easily produced. Second, the material is extremely sensitive to temperature, and the processing window is narrow. Small temperature fluctuations can cause thermal decomposition, seriously affecting the surface quality and internal performance of the product. Third, the cooling shrinkage and solidification behavior during the molding process are difficult to control, and large internal stress is easily accumulated in the product, which in turn induces size stability defects such as warping and deformation. Fourth, the mismatch between process parameters and material characteristics leads to large mechanical property dispersion, poor repeatability and stability. The above defects seriously restrict the full play of the potential of PPEK material and the industrialization application process. Therefore, it is urgent to develop a targeted special injection molding process to systematically solve these technical bottlenecks.

[0004] In view of this, the present application is proposed. SUMMARY

[0005] The purpose of the present application is to provide an injection molding method for poly (phthalazinone ether ketone) material. By finding the optimal ratio of back pressure, melt viscosity and temperature, using a multi-stage injection strategy, and establishing an accurate correspondence between mold temperature and cooling time, the optimal synergistic control of key process parameters during the injection molding process of PPEK material is achieved, significantly improving the quality and performance stability of the product.

[0006] The present application is implemented as follows:

[0007] The application provides an injection molding method of a heteronaphthalene biphenyl polyaryletherketone material, comprising the following steps: drying the heteronaphthalene biphenyl polyaryletherketone material, melting and plasticizing the dried material in a segmented temperature-raising cylinder to obtain a melt; injecting the melt into a mold cavity by using a multi-stage injection method; performing pressure maintaining and cooling and shaping on the melt in the mold cavity, and performing heat treatment and cooling after demolding to obtain a high-performance heteronaphthalene biphenyl polyaryletherketone product.

[0008] In some preferred embodiments, the heteronaphthalene biphenyl polyaryletherketone material is dried at 150-180℃ for 4-6h, and the water content of the dried heteronaphthalene biphenyl polyaryletherketone material is ≤0.02%.

[0009] In some preferred embodiments, the segmented temperature-raising control of the cylinder temperature is as follows: 340-350℃ in region I, 350-360℃ in region II, and 355-365℃ in region III.

[0010] In some preferred embodiments, the back pressure control of the melting and plasticizing is 8-15bar, and the screw rotation speed is 70-120rpm.

[0011] In some preferred embodiments, the multi-stage injection comprises two stages; the injection speed of the first-stage injection is 20-30mm / s, and the injection pressure is 70-90MPa; the injection speed of the second-stage injection is 30-50mm / s, and the injection pressure is 80-120MPa.

[0012] In some preferred embodiments, the mold is accurately controlled by a mold temperature machine, and the mold temperature is 180-200℃.

[0013] In some preferred embodiments, the pressure maintaining pressure is 40-70MPa, and the pressure maintaining time is 4-10s.

[0014] In some preferred embodiments, the cooling and shaping time is 20-40s.

[0015] In some preferred embodiments, the heat treatment temperature is 240-280℃, and the heat treatment time is 1-6h.

[0016] In some preferred embodiments, the cooling rate after the heat treatment is ≤20℃ / h.

[0017] The application has the following beneficial effects:

[0018] The injection molding method provided by the application has achieved remarkable comprehensive effects in improving the performance of PPEK products, improving the molding quality, optimizing the production efficiency and the like by optimizing key process parameters and their synergistic effects. The mechanical properties, tensile strength and bending strength of the products are significantly improved; the molding quality is greatly improved, the defects such as melt rupture and silver streak are effectively inhibited, and the size stability is improved; at the same time, the production efficiency is improved, the molding cycle is shortened by 8%-12%, and the comprehensive energy consumption is reduced by about 10%. These improvements not only effectively solve the core process problems such as insufficient melting, flow filling difficulty, thermal decomposition sensitivity and internal stress concentration in the injection molding process of PPEK material, but also significantly enhance the controllability and economy of the production process, thereby laying an important technical foundation for the large-scale reliable application of PPEK in the high-performance field. BRIEF DESCRIPTION OF DRAWINGS

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the application, and therefore should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained without creative labor on the basis of these drawings.

[0020] Figure 1 The flow chart of the injection molding method in the embodiments of the application;

[0021] Figure 2 The schematic diagram of the heteronaphthalene-biphenyl polyaryletherketone material in Embodiment 1 of the application;

[0022] Figure 3 The schematic diagram of the heteronaphthalene-biphenyl polyaryletherketone material in Comparative Example 1 of the application. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solutions and advantages of the embodiments of the application more clear, the technical solutions in the embodiments of the application will be described clearly and completely below. The specific conditions not mentioned in the embodiments are carried out according to the conventional conditions or the conditions suggested by the manufacturer. The reagents or instruments not mentioned by the manufacturer are all conventional products that can be obtained by market purchase.

[0024] The injection molding method of a heteronaphthalene-biphenyl polyaryletherketone (PPEK) material provided by the application will be described in detail below.

[0025] The injection molding method of a heteronaphthalene-biphenyl polyaryletherketone material provided by the application is shown in the schematic diagram as Figure 1 The injection molding method of a heteronaphthalene-biphenyl polyaryletherketone material provided by the application is shown in the schematic diagram as

[0026] S1, drying the heteronaphthalene-biphenyl polyaryletherketone material, melting and plasticizing the dried material in a segmented temperature-raising cylinder to obtain a melt.

[0027] In some preferred embodiments, the heteronaphthalene poly (phthalazinone ether ketone) material is dried at 150-180°C for 4-6h to reduce the water content to below 0.02%.

[0028] In some preferred embodiments, the segmented temperature control of the barrel is set as: Zone I 340-350°C, Zone II 350-360°C and Zone III 355-365°C, wherein Zone I is the feeding zone, Zone II is the compression section and Zone III is the metering section.

[0029] In some preferred embodiments, the back pressure of the melt plasticization is controlled at 8-15bar and the screw rotation speed is 70-120rpm. Different from common plastics such as PP and ABS, PPEK has a narrow processing window, extremely high melt viscosity and is sensitive to thermal and shear history. Improper back pressure and rotation speed can cause a series of serious problems.

[0030] The main role of the back pressure control is to increase the compaction degree of the melt in the screw metering section and improve the melting effect, thereby effectively removing the trace amount of water remaining in the raw material and the volatile matter that may be generated at high temperature, preventing the occurrence of silver streaks, bubbles or internal pores in the final product. At the same time, appropriate back pressure can significantly improve the uniformity and density of the melt, reducing the shot size fluctuation and product size instability caused by uneven plasticization, which is crucial for PPEK materials with high crystallinity and narrow processing window. If the back pressure is too low, the above effects cannot be achieved; while if the back pressure is too high, the material in the barrel is prone to excessive shear and heat generation, increasing the risk of material thermal degradation.

[0031] Further, excessively high screw rotation speed can generate intense shear heat, making it difficult to accurately control the melt temperature within the narrow ideal processing range, which can easily cause local overheating degradation, resulting in a decrease in molecular weight and deterioration of mechanical properties. On the contrary, excessively low rotation speed can result in too long plasticization time and the melt stays in the high-temperature barrel for too long, which can also cause thermal aging. Therefore, a relatively low and stable screw rotation speed must be used, and its specific value must be matched with the set barrel temperature, back pressure value and product weight per unit area to ensure a gentle and homogeneous plasticization process, providing a melt with good thermal uniformity and viscosity consistency for the subsequent injection stage.

[0032] Therefore, this application proposes an optimal ratio between back pressure and screw speed to achieve uniform plasticization of the melt while avoiding overheating and decomposition. It should be noted that the back pressure needs to be adjusted according to the viscosity of the material. Generally, melt viscosity is related to the melt flow rate; at the melting temperature, the higher the melt index, the lower the melt viscosity. At 365℃, when the melt index is 20 g / 10 min, the back pressure is typically set to 14 bar; when the melt index is 30 g / 10 min, the back pressure is set to 12 bar; when the melt index is 40 g / 10 min, the back pressure is set to 10 bar; and when the melt index is 50 g / 10 min, the back pressure is set to 8 bar.

[0033] S2. The melt is injected into the mold cavity using a multi-stage injection method.

[0034] In some preferred embodiments, the multi-stage injection includes two stages; the first stage has an injection speed of 20-30 mm / s and an injection pressure of 70-90 MPa, used to fill the flow channels; the second stage has an injection speed of 30-50 mm / s and an injection pressure of 80-120 MPa, used to complete 98% filling.

[0035] This invention innovatively adopts a multi-stage injection strategy, which reconciles the contradiction between the need for rapid filling of PPEK melt to prevent cooling and the need for smooth flow to prevent deterioration. It fundamentally solves the quality problems such as filling difficulties, surface defects and internal stress concentration of large, thin-walled or complex parts, and achieves high-precision and high-yield molding, solving the problems of melt filling and quality.

[0036] Specifically, in the initial stage of filling, a lower speed is used to allow the melt to smoothly pass through the gate and enter the cavity. This effectively avoids jetting or turbulence caused by excessive shear rate, preventing air entrapment and the formation of surface flow marks. Once the melt front has smoothly passed the gate area, a higher speed can be switched to perform the main filling. This ensures that most of the cavity is filled quickly before the melt temperature drops significantly and the viscosity rises sharply, avoiding problems such as short shots, weak weld line strength, or uneven surface gloss caused by premature cooling of the flow front.

[0037] In some preferred embodiments, the mold is precisely controlled by a mold temperature controller, with the mold temperature set at 180-200°C. This allows the PPEK melt to cool and crystallize slowly and uniformly within the mold cavity, thereby fully releasing the material's inherent properties and obtaining a final product with dimensional stability, low internal stress, and excellent mechanical properties.

[0038] S3. Hold pressure and cool the melt in the mold cavity to solidify it.

[0039] In some preferred embodiments, the holding pressure is 40-70 MPa, the holding time is 4-10 s, and the holding time is adjusted according to the thickness of the desired product; the cooling and setting time is 20-40 s, and the cooling temperature is the mold temperature, to ensure that the product is fully cooled and set.

[0040] If the cooling time is too short, the product core temperature is still high when the mold is opened after holding, and the temperature difference between the inside and outside of the product is large, resulting in a huge thermal residual stress due to subsequent uneven shrinkage. If the cooling time is too long, although complete cooling can be ensured, the production efficiency will be sacrificed. Therefore, by monitoring the actual cooling curve through a hot runner sensor or an in-mold temperature sensor, and establishing a mathematical model, an optimal cooling time point can be determined, i.e., when the temperature of the thick wall of the product uniformly decreases to near the mold temperature, and the crystallization process has been basically completed. At this point, the mold is opened, the overall temperature field of the product is uniform, the uneven shrinkage caused by the temperature difference is minimized, and the molecular chains are also "frozen" in a relaxed state, thereby achieving the minimization and balanced distribution of internal stress.

[0041] S4, the material after demolding is subjected to heat treatment and cooling to obtain a high-performance hetero-naphthalene-biphenyl polyaryletherketone product.

[0042] In some preferred embodiments, the heat treatment temperature is 240-280℃, the time is 1-6h, and the cooling rate after heat treatment is ≤20℃ / h.

[0043] The material after demolding is usually in a non-equilibrium state, and the molecular chains may have internal stress, uneven orientation, or imperfect crystallization due to shearing and rapid solidification during the processing. Heat treatment provides sufficient movement ability for the molecular chains, allowing them to rearrange and form more perfect and stable crystal structures, thereby improving the crystallinity and uniformity of the crystal size. This process helps to eliminate internal stress, reduce defects, and promote the close packing of molecular chains, thereby significantly improving the mechanical strength, dimensional stability, heat resistance, and creep resistance of the material. Slow cooling allows the crystals to have sufficient time to grow and perfect, forming a more balanced distribution of crystal and amorphous regions, thereby obtaining more excellent long-term performance and fatigue resistance.

[0044] The features and performance of the present application are further described in detail below in conjunction with the embodiments.

[0045] Example 1

[0046] The present embodiment provides a method for injection molding of a hetero-naphthalene-biphenyl polyaryletherketone material, comprising the following steps:

[0047] S1, the hetero-naphthalene-biphenyl polyaryletherketone material is dried at 180°C for 4h, and after drying, it is added to the injection molding machine barrel for melt plasticization to obtain a melt, wherein the barrel temperature is controlled by increasing in sections along the feeding direction: 350°C in section I, 360°C in section II, and 365°C in section III, the back pressure of melt plasticization is controlled at 8 bar, and the screw rotation speed is 90 rpm.

[0048] S2, the melt is injected into the mold cavity by two-stage injection: the injection speed in the first-stage injection is 25 mm / s, and the injection pressure is 90 MPa; the injection speed in the second-stage injection is 35 mm / s, and the injection pressure is 110 MPa; the mold temperature is accurately controlled by a mold temperature machine, and the mold temperature is 180°C.

[0049] S3, the melt in the mold cavity is subjected to a pressure of 55 MPa for 6s, and then cooled and shaped in the mold for 40s, and then demolded.

[0050] S4, the material after demolding is subjected to heat treatment at 250°C for 4h and cooled to room temperature to obtain a high-performance hetero-naphthalene-biphenyl polyaryletherketone product, as shown in Figure 2 .

[0051] Example 2

[0052] The injection molding method of the hetero-naphthalene-biphenyl polyaryletherketone material provided in this example has the same steps as in Example 1, and the only difference is that the holding pressure is 50 MPa, and the holding time is 4s.

[0053] Example 3

[0054] The injection molding method of the hetero-naphthalene-biphenyl polyaryletherketone material provided in this example has the same steps as in Example 1, and the only difference is that the back pressure is 12 bar, and the screw rotation speed is 120 rpm.

[0055] Comparative Example 1

[0056] The injection molding method of the hetero-naphthalene-biphenyl polyaryletherketone material provided in this example comprises the following steps:

[0057] S1, the hetero-naphthalene-biphenyl polyaryletherketone material is dried at 180°C for 4h, and after drying, it is added to the injection molding machine barrel for melt plasticization to obtain a melt, wherein the barrel temperature is controlled by increasing in sections along the feeding direction: 350°C in section I, 360°C in section II, and 365°C in section III, the back pressure of melt plasticization is controlled at 8 bar, and the screw rotation speed is 90 rpm.

[0058] S2, the melt is injected into the mold cavity by two-stage injection: the injection speed in the first-stage injection is 25 mm / s, and the injection pressure is 90 MPa; the injection speed in the second-stage injection is 35 mm / s, and the injection pressure is 110 MPa; the mold temperature is accurately controlled by a mold temperature machine, and the mold temperature is 180°C.

[0059] S3, the melt in the mold cavity is applied with a pressure of 55 MPa for 6 s, and cooled and shaped at 180 °C for 40 s, and then demolded.

[0060] S4, the material after demolding is heat treated at 250 °C for 4 h and cooled to room temperature, to obtain a high-performance hetero-naphthalene-biphenyl polyaryletherketone product, as shown in Figure 3

[0061] Comparative Example 2

[0062] This comparative example provides an injection molding method of a hetero-naphthalene-biphenyl polyaryletherketone material, including the following steps: after simple drying, the barrel temperature is uniform (not segmented); single-stage uniform injection is used; after pressure holding, demolding is directly performed, without special heat treatment.

[0063] Comparative Example 3

[0064] This comparative example provides an injection molding method of a hetero-naphthalene-biphenyl polyaryletherketone material, which has the same steps as Example 1, and the only difference is that only a single barrel temperature of 360 °C is used for melting and plasticizing.

[0065] Comparative Example 4

[0066] This comparative example provides an injection molding method of a hetero-naphthalene-biphenyl polyaryletherketone material, which has the same steps as Example 1, and the only difference is that only single-stage uniform injection is used, with an injection speed of 35 mm / s and an injection pressure of 100 MPa.

[0067] Comparative Example 5

[0068] This comparative example provides an injection molding method of a hetero-naphthalene-biphenyl polyaryletherketone material, which has the same steps as Example 1, and the only difference is that a pressure holding pressure of 20 MPa and a pressure holding time of 2 s are used; the cooling and shaping time is 10 s.

[0069] Comparative Example 6

[0070] This comparative example provides an injection molding method of a hetero-naphthalene-biphenyl polyaryletherketone material, which has the same steps as Example 1, and the only difference is that the back pressure control for melting and plasticizing is 3 bar, and the screw speed is 180 rpm.

[0071] Test Example 1

[0072] The high-performance hetero-naphthalene-biphenyl polyaryletherketone products prepared in Example 1 and Comparative Examples 1-6 are subjected to performance testing.

[0073]

[0074] ​According to the experimental results, Example 1 has the best performance in all performance indicators, with a tensile strength of 106.24 MPa, a bending strength of 127.64 MPa, the smallest sample size deviation (-10 μm²), the best product appearance quality, no shrinkage on the surface, smooth without patterns, and high performance stability (tensile strength standard deviation of only 0.2). This shows that the comprehensive process parameters adopted in Example 1, including segmented temperature plasticization (350℃ / 360℃ / 365℃), two-stage injection (90MPa / 110MPa), moderate back pressure (8bar) and screw speed (90rpm), higher holding pressure and time (55MPa / 6s), and subsequent heat treatment (250℃ / 4h), can effectively improve the mechanical properties, dimensional accuracy and surface quality of the polyaryletherketone material.

[0075] In contrast, each of the comparative examples deviates from the optimized conditions of Example 1 in one or more parameters, and all have different degrees of performance decline. Comparative Example 1 uses a lower cylinder temperature (335℃ in Zone I, 345℃ in Zone II, and 354℃ in Zone III), which leads to a significant decrease in tensile and bending strength, an increase in size deviation, and the appearance of patterns on the surface, and an increase in standard deviation, indicating that the melt plasticization is not sufficient, the filling and compaction are insufficient, which affects the structural uniformity and mechanical properties of the material. Comparative Example 2 uses simple drying, uniform cylinder temperature, single-stage injection and no heat treatment, which is too simple, resulting in insufficient plasticization, flow and post-treatment of the material, and overall performance decline, especially an increase in surface patterns and a large size deviation. Comparative Example 3 only uses a single cylinder temperature (360℃) without segmented temperature, which affects the gradual plasticization and uniformity of the melt, resulting in slightly lower performance than Example 1 and more surface patterns. Comparative Example 4 only uses single-stage uniform injection without two-stage injection to optimize the melt filling process, resulting in insufficient flow control of the material during the mold filling stage, and a decrease in performance. Comparative Example 5 uses a lower holding pressure and a shorter holding time, and the cooling time is also shortened, resulting in product shrinkage, incomplete end, maximum size deviation, and significant decrease in mechanical properties, indicating that the holding and cooling stages are crucial for the density and shape stability of the product. Comparative Example 6 uses a lower back pressure and a higher screw speed, resulting in uneven melt plasticization, possible air entrainment or degradation, and a significant decrease in performance, with surface flow patterns and not smooth.

[0076] In summary, the method realizes the precise control of the whole forming process of the poly (phthalazinone ether ketone) by the multi-parameter synergistic control of drying, stepwise heating melting, multi-stage injection, pressure maintaining cooling and post-heat treatment. Among them, the stepwise heating strategy along the feeding direction ensures the gradual plasticization and uniform melting of the material, effectively avoiding thermal degradation; the multi-stage injection process optimizes the shearing and flow behavior in the melt filling process, reducing the internal stress and defect formation; and the specific heat treatment and controllable cooling after demolding directly regulate the crystallization kinetics of the material, making it form a more perfect and stable crystal structure, thereby comprehensively improving the mechanical properties, dimensional stability and heat resistance of the material. This series of process links is not isolated, but forms a synergistic system that is related and mutually enhanced, for example, the improvement of the melt quality in the early stage lays a foundation for the optimization of crystallization in the later stage, and the heat treatment further eliminates the internal stress and structural unevenness remaining in the early processing. This whole-process multi-parameter synergistic control method running through the raw material treatment, injection molding and post-treatment, systematically solves the key problems of degradation, uneven orientation and imperfect crystallization of the poly (phthalazinone ether ketone) in the processing, and represents an important progress in the field of precise forming technology of high-performance polymers.

[0077] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for injection molding a polyaryletherketone material containing naphthalene-biphenyl, characterized in that, The process includes the following steps: drying the naphthalene-biphenyl polyaryletherketone material; melting and plasticizing the dried material in a segmented heating barrel to obtain a melt; injecting the melt into a mold cavity using a multi-stage injection method; holding pressure and cooling the melt in the mold cavity to solidify it; and then heat-treating and cooling it after demolding to obtain a high-performance naphthalene-biphenyl polyaryletherketone product. The temperature of the barrel is controlled in stages: Zone I 340–350℃, Zone II 350–360℃ and Zone III 355–365℃; The back pressure during the melting and plasticizing process is controlled at 8-15 bar, and the screw speed is 70-120 rpm. The multi-stage injection includes two phases: the injection speed of the first-stage injection is 20-30 mm / s, and the injection pressure is 70-90 MPa; the injection speed of the second-stage injection is 30-50 mm / s, and the injection pressure is 80-120 MPa. The mold is precisely controlled by a mold temperature controller, and the mold temperature is 180-200℃. The pressure holding pressure is 40-70 MPa, and the pressure holding time is 4-10 seconds; The cooling and shaping time is 20-40 seconds.

2. The injection molding method for a heteronaphthyl biphenyl polyaryletherketone material according to claim 1, characterized in that, The naphthalene-biphenyl polyaryletherketone material is dried at 150-180℃ for 4-6 hours, and the water content of the dried naphthalene-biphenyl polyaryletherketone material is ≤0.02%.

3. The injection molding method for a naphthalene-biphenyl polyaryletherketone material according to claim 1, characterized in that, The heat treatment is performed at a temperature of 240-280℃ for 1-6 hours.

4. The injection molding method for a naphthalene-biphenyl polyaryletherketone material according to claim 1, characterized in that, The cooling rate after heat treatment is ≤20℃ / h.

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