A PC-PET plastic with high dimensional stability and preparation method thereof

Abstract

The present invention provides a PC-PET plastic with high dimensional stability and a preparation method thereof. PC-PET plastic includes the following components in parts by weight: 40-60 parts of PC resin; 40-60 parts of PET resin; 0.5-5 parts of polymer synergist; 0.2-2 parts of interfacial energy shielding agent; wherein the polymer synergist is a copolymer comprising PMMA block and PEO block, the PMMA block has polar compatibility with the PC phase, the PEO block forms a van der Waals effect or a hydrogen bond with the ester group in the PET phase, the mass ratio of PMMA block and PEO block is (3-4): 1, and the polymer synergist is a PMMA-b-PEO-b-PMMA triblock copolymer; the interfacial energy shielding agent contains a low-molecular-weight organic matter with a silicon-oxygen structure, and the interfacial energy of the low-molecular-weight organic matter is less than 22mN / m, and the weight-average molecular weight of the low-molecular-weight organic matter is 3000g / mol-10000g / mol. According to the present invention, the PC-PET blend material achieves high dimensional stability without relying on high fillers, without destroying the transparency, surface finish and toughness of the material.

Description

Technical Field

[0001] The present invention relates to the technical field of blending and modification of polymer materials, in particular to a PC-PET plastic with high dimensional stability and a preparation method thereof. Background Art

[0002] Blending polycarbonate (PC) with polyethylene terephthalate (PET) can balance the mechanical properties, processability, and partial heat resistance of both. However, due to the significant difference in polarity between PC and PET, the two are incompatible at the molten interface, which can easily lead to phase separation in the blended system. This can cause interfacial stress concentration, warping, dimensional instability, and other problems, making it difficult to meet the requirements of applications requiring high thermal stability and high appearance quality.

[0003] Existing modification methods primarily include the introduction of compatibilizers and the addition of fillers. However, compatibilizers often overreact with one of the phases or thermally degrade, resulting in unstable mechanical properties and a narrow processing window. The addition of fillers can easily lead to reduced transparency, surface finish, and impact resistance, making it difficult to meet the simultaneous requirements of optical quality and high dimensional stability for applications such as LiDAR elevating structures, elevating tail fins, and transparent sensor housings. Summary of the Invention

[0004] In order to solve the above problems, according to a first aspect of the present invention, a PC-PET plastic with high dimensional stability is provided, comprising the following components in parts by weight:

[0005] 40-60 parts of PC resin;

[0006] 40-60 parts of PET resin;

[0007] 0.5-5 parts of polymer synergist;

[0008] 0.2-2 parts of interfacial energy shielding agent;

[0009] The polymer synergist is a copolymer comprising a PMMA block and a PEO block, wherein the PMMA block has polar compatibility with the PC phase, the PEO block forms a van der Waals interaction or a hydrogen bond interaction with the ester group in the PET phase, the mass ratio of the PMMA block to the PEO block is (3-4):1, and the polymer synergist is a PMMA-b-PEO-b-PMMA triblock copolymer;

[0010] The interfacial energy shielding agent contains a low molecular weight organic matter with a silicon-oxygen structure, the interfacial energy of the low molecular weight organic matter is less than 22 mN / m, and the weight average molecular weight of the low molecular weight organic matter is 3000 g / mol-10000 g / mol.

[0011] Optionally, the total weight average molecular weight of the PMMA-b-PEO-b-PMMA triblock copolymer is 30000 g / mol-50000 g / mol;

[0012] The polymer distribution index of the PMMA-b-PEO-b-PMMA triblock copolymer is not greater than 1.2, wherein the glass transition temperature of the PMMA block is between 105° C. and 115° C., and the glass transition temperature of the PEO block is between -30° C. and -20° C.

[0013] Optionally, the preparation method of the PMMA-b-PEO-b-PMMA triblock copolymer comprises the following steps:

[0014] The polyethylene oxide glycol and the activated carbonate end-capping agent are subjected to an ester exchange reaction in the presence of a titanate catalyst at a temperature range of 90°C to 100°C to obtain a symmetrical dicarbonate end-capped PEO intermediate;

[0015] Adding the dicarbonate-terminated PEO intermediate, MMA monomer, free radical initiator and chain transfer agent into dimethyl sulfoxide to form a reaction system;

[0016] The reaction system is reacted at 90° C.-100° C. under an inert atmosphere for 5 h-7 h to generate a PMMA-b-PEO-b-PMMA triblock copolymer.

[0017] Optionally, the activated carbonate end-capping agent is p-nitrophenyl carbonate, fluorophenyl carbonate or NHS-carbonate;

[0018] The titanate catalyst is tetraisobutoxy titanate, titanium acetylacetonate or titanium isopropoxide;

[0019] The free radical initiator is azobisisobutyronitrile or methyl azobisisobutyrate;

[0020] The chain transfer agent is 2-(dimethylamino)propyl dithiocarboxate or S-1-diethylaminocarbonyl-2-methylpropyl dithiocarboxate.

[0021] Optionally, the molar ratio of the polyethylene oxide glycol, the activated carbonate end-capping agent and the titanate catalyst is 1:(2.2-2.5):(0.01-0.05);

[0022] The molar ratio of the dicarbonate-terminated PEO intermediate, the MMA monomer, the free radical initiator and the chain transfer agent is 1:(150-250):(0.2-0.5):1.

[0023] Optionally, the interfacial energy shielding agent is a compound system of polymethyl hydrogen siloxane and silane functionalized polyvinyl alcohol, the total addition amount of the compound system accounts for 0.2wt%-0.8wt% of the total amount of PC resin and PET resin, the mass ratio of the polymethyl hydrogen siloxane to the silane functionalized polyvinyl alcohol is (4-9):1, and the polymethyl hydrogen siloxane is used as the low molecular weight organic matter;

[0024] The hydrogen content of the Si—H groups in the polymethylhydrogensiloxane is 1 wt % to 3 wt %, and the grafting rate of the silane-functionalized polyvinyl alcohol is 15 mol % to 40 mol %.

[0025] Optionally, the silane-functionalized polyvinyl alcohol is polyvinyl alcohol grafted and modified with triethoxysilane, acryloxysilane or aminopropyltriethoxysilane.

[0026] Optionally, the compounding system further comprises a synergist, which is aminopropyltriethoxysilane or fluorine-modified alkylsilane. The added amount of the synergist accounts for 0.05wt%-0.1wt% of the total amount of PC resin and PET resin.

[0027] In particular, the present invention also provides a method for preparing the aforementioned PC-PET plastic with high dimensional stability, comprising the following steps:

[0028] Pre-dispersing the polymer synergist and the interfacial energy shielding agent at 70° C.-90° C. to obtain a premixed phase;

[0029] Melt-blending the PC resin, the PET resin and the premixed phase at 220° C. to 260° C. for 2 to 4 minutes to obtain a melt blend;

[0030] The molten blend is granulated to obtain PC-PET plastic particles with a particle size of 2 mm to 4 mm.

[0031] Optionally, the temperatures of the zones of the extruder from the feed zone to the die zone are 220°C-230°C, 230°C-240°C, 240°C-250°C and 250°C-260°C, respectively, and the screw speed is 80rpm-150rpm.

[0032] According to the present invention, a polymer synergist comprising PMMA and PEO blocks is introduced into a PC-PET blend to achieve polarity harmonization at the PC-PET interface. The PMMA blocks have a polarity structure that matches that of PC, enhancing its dispersion stability within the PC matrix. The PEO blocks, by forming van der Waals interactions or hydrogen bonds with ester groups in the PET phase, enhance their synergistic properties within the PET phase. The coexistence of the two in a specific mass ratio achieves molecular-level compatibility and flexible connectivity at the PC-PET interface, mitigating interfacial tension and the risk of microphase separation. The interfacial energy shielding agent, a low-molecular-weight organic compound containing a silicon-oxygen structure and an interfacial energy of less than 22 mN / m, preferentially distributes at the PC-PET interface, reducing interfacial free energy and suppressing interphase stress concentration and interfacial migration caused by the high polarity difference. This improves interfacial wettability and mechanical buffering during processing, thereby preventing interfacial delamination and stress warping during thermal cycling or complex molding processes. Therefore, the present invention achieves high dimensional stability and low cost of PC-PET blend materials, with a dimensional change rate of less than 0.4% and a molding shrinkage rate of less than 0.4% under thermal cycling conditions of -40°C to 90°C, through the synergistic effect of polymer synergists and interfacial energy shielding agents, without relying on high fillers and without destroying the transparency, surface finish and toughness of the material. The material is particularly suitable for application scenarios of structural parts with high requirements for dimensional accuracy and appearance quality, such as laser radar lifting components, transparent sensor housings and liftable tail wings.

[0033] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the following is a detailed description of the preferred embodiments of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 A schematic flow chart of a method for preparing a PMMA-b-PEO-b-PMMA triblock copolymer according to one embodiment of the present invention is shown;

[0035] Figure 2 A schematic flow chart of a method for preparing triethoxysilane-grafted modified polyvinyl alcohol according to one embodiment of the present invention is shown;

[0036] Figure 3 A schematic flow chart of a method for preparing polyvinyl alcohol grafted with acryloxysilane according to one embodiment of the present invention is shown;

[0037] Figure 4 A schematic flow chart of a method for preparing polyvinyl alcohol grafted and modified with aminopropyltriethoxysilane according to one embodiment of the present invention is shown;

[0038] Figure 5A schematic flow chart of a method for preparing a PC-PET plastic with high dimensional stability according to one embodiment of the present invention is shown;

[0039] Figure 6 shows a gel permeation chromatogram of the triblock copolymer prepared in Example 1 of the present invention;

[0040] Figure 7 shows a differential scanning calorimetry (DSC) spectrum of the triblock copolymer prepared in Example 1 of the present invention;

[0041] Figure 8 The triethoxysilane grafted modified polyvinyl alcohol prepared in Example 2 of the present invention is shown. 1 H-NMR spectrum. DETAILED DESCRIPTION

[0042] The technical solution of the present invention is further described below in conjunction with specific embodiments.

[0043] The embodiment of the present invention provides a PC-PET plastic with high dimensional stability, comprising the following components in parts by weight:

[0044] 40-60 parts of PC resin;

[0045] 40-60 parts of PET resin;

[0046] 0.5-5 parts of polymer synergist;

[0047] 0.2-2 parts of interfacial energy shielding agent;

[0048] The polymer synergist is a copolymer comprising a PMMA block and a PEO block, the PMMA block has polar compatibility with the PC phase, the PEO block forms a van der Waals interaction or a hydrogen bond interaction with the ester group in the PET phase, the mass ratio of the PMMA block to the PEO block is (3-4):1, and the polymer synergist is a PMMA-b-PEO-b-PMMA triblock copolymer; the interfacial energy shielding agent contains a low-molecular-weight organic matter with a silicon-oxygen structure, the interfacial energy of the low-molecular-weight organic matter is less than 22 mN / m, and the weight-average molecular weight of the low-molecular-weight organic matter is 3000 g / mol-10000 g / mol.

[0049] According to the solution of the embodiment of the present invention, by introducing a polymer synergist containing PMMA blocks and PEO blocks into the PC-PET blend system, polarity harmonization is achieved at the PC-PET interface. The PMMA blocks have a polar structure that matches that of PC, which helps to enhance its dispersion stability in the PC matrix. The PEO blocks enhance their synergistic ability in the PET phase by forming van der Waals interactions or hydrogen bonds with ester groups in the PET phase. The coexistence of the two in a specific mass ratio can achieve molecular compatibility and flexible connection at the PC-PET interface, alleviating interfacial tension and the risk of microphase separation. The interfacial energy shielding agent is a low-molecular-weight organic compound containing a silicon-oxygen structure with an interfacial energy of less than 22 mN / m. It can be preferentially distributed in the interface region between PC and PET, reducing interfacial free energy, inhibiting interphase stress concentration and interfacial migration caused by high polarity differences, improving interfacial wettability and mechanical buffering capacity during processing, and thus avoiding interfacial delamination and stress warping during thermal cycling or complex molding processes. Therefore, the present invention achieves high dimensional stability and low cost of PC-PET blend materials, with a dimensional change rate of less than 0.4% and a molding shrinkage rate of less than 0.4% under thermal cycling conditions of -40°C to 90°C, through the synergistic effect of polymer synergists and interfacial energy shielding agents, without relying on high fillers and without destroying the transparency, surface finish and toughness of the material. The material is particularly suitable for application scenarios of structural parts with high requirements for dimensional accuracy and appearance quality, such as laser radar lifting components, transparent sensor housings and liftable tail wings.

[0050] In one embodiment, the total weight-average molecular weight of the PMMA-b-PEO-b-PMMA triblock copolymer is 30,000 g / mol to 50,000 g / mol, for example, 30,000 g / mol, 40,000 g / mol, or 50,000 g / mol. Within this total weight-average molecular weight range, the polymer synergist's molecular chains can effectively extend and anchor at the interface between PC and PET, forming a stable polar transition channel without significantly increasing the system viscosity or causing phase separation risk.

[0051] The polymer distribution index (PDI) of the PMMA-b-PEO-b-PMMA triblock copolymer is no greater than 1.2, preferably between 1.05 and 1.15, for example, 1.05, 1.1, or 1.15. This PDI ensures a concentrated distribution of polymer synergist molecular chain lengths, thereby promoting uniform distribution and coordinated arrangement at the interface between PC and PET. This effectively reduces compatibility issues caused by differences in interfacial energy and polarity, enhances interfacial connectivity, and ultimately improves the thermal dimensional stability and molding precision of the entire blend.

[0052] The glass transition temperature of the PMMA block is between 105°C and 115°C, for example, 105°C, 110°C, or 115°C. The glass transition temperature of the PEO block is between -30°C and -20°C, for example, -30°C, -25°C, or -20°C. The PMMA-b-PEO-b-PMMA triblock copolymer achieves a "rigid and flexible" interfacial synergistic mechanism by precisely designing the glass transition temperatures of the two blocks. The PMMA block provides rigid anchoring and polarity matching, enhancing the interfacial stability and thermal dimensional retention of the PC phase, while the PEO block provides flexible bridging and hydrogen bond affinity, regulating the interfacial behavior of the PET phase and alleviating stress concentration. This temperature window design ensures that the polymer synergist has high dimensional stability under thermal cycling and complex processing environments between -40°C and 90°C.

[0053] In summary, through the coordinated design of the above-mentioned parameters, the polymer synergist achieves flexible bridging and polarity matching adjustment at the molecular scale between the PC and PET phases, effectively reducing interfacial tension, inhibiting phase separation and interfacial warping, and alleviating dimensional deformation caused by thermal stress accumulation. This further ensures the high dimensional stability of the blended material, with a dimensional change rate of less than 0.4% and a molding shrinkage rate of less than 0.4% under a thermal cycling environment of -40°C to 90°C.

[0054] Figure 1 FIG1 shows a schematic flow chart of a method for preparing a PMMA-b-PEO-b-PMMA triblock copolymer according to an embodiment of the present invention. Figure 1 As shown, the preparation method comprises:

[0055] Step S111, conducting an ester exchange reaction between polyethylene oxide and an activated carbonate end-capping agent in the presence of a titanate catalyst at a temperature range of 90° C. to 100° C. to obtain a dicarbonate end-capped PEO intermediate with a symmetrical structure;

[0056] Step S112, adding the dicarbonate-terminated PEO intermediate, MMA monomer, free radical initiator and chain transfer agent into dimethyl sulfoxide to form a reaction system;

[0057] Step S113 , reacting the reaction system at 90° C.-100° C. under an inert atmosphere for 5 h-7 h to generate a PMMA-b-PEO-b-PMMA triblock copolymer.

[0058] In step S111, the molar ratio of polyethylene oxide glycol, activated carbonate end-capping agent, and titanate catalyst is 1:(2.2-2.5):(0.01-0.05), for example, 1:2.2:0.03, 1:2.3:0.02, 1:2.5:0.04, or 1:2.4:0.05. This ratio strategy, through the synergistic effect of a reasonable excess of end-capping agent and a trace amount of high-efficiency catalyst, enables the transesterification reaction to have good conversion rate, structural controllability, and process stability, laying a reliable molecular foundation for the subsequent construction of PMMA-b-PEO-b-PMMA triblock copolymers with symmetrical structure, narrow distribution, and a well-defined glass transition temperature range.

[0059] The activated carbonate end-capping agents are p-nitrophenyl carbonate, fluorophenyl carbonate, or NHS-carbonate. The phenolic or amide leaving groups in these three carbonate structures exhibit strong electron attraction, effectively stabilizing the generated negative ions. This makes these carbonates highly electrophilic, thus facilitating rapid transesterification with the terminal hydroxyl groups of polyethylene oxide glycol. Furthermore, these carbonate end-capping agents have a simple structure, and the resulting intermediate (dicarbonate-capped PEO) exhibits good symmetry and controllable functional group density. This facilitates uniform growth of PMMA blocks from both ends during the subsequent controlled free radical polymerization, reducing fluctuations in molecular weight distribution and improving polymer structural uniformity. Furthermore, all three carbonate end-capping agents are hydrophobic small molecules of medium to low molecular weight and are well soluble in organic solvents (such as DMSO). They form a uniform reaction system with PEO, facilitating controllable reaction kinetics and subsequent product purification.

[0060] The titanate catalyst is tetraisobutoxy titanate, titanium acetylacetonate or titanium isopropoxide. The above titanate compounds are all Lewis acid-type metal complexes with excellent transesterification catalytic activity. They can accelerate the nucleophilic attack of hydroxyl groups on carbonates by synergistically activating the nucleophilic and electrophilic reaction process between hydroxyl groups and carbonate carbonyl groups, thereby increasing the transesterification rate and shortening the reaction time. In addition, these titanate catalysts have good solubility in polar solvents such as DMSO and can be fully mixed with PEO and activated carbonates to form a uniform system, avoiding side reactions or uneven end-capping of functional groups caused by local concentration extremes. At the same time, the above titanate catalysts can achieve a high end-capping rate at a lower dosage, ensuring a uniform distribution of initiation sites at both ends from the source, thereby improving the symmetry and polymerization controllability of the subsequent triblock copolymer structure and reducing the polymer molecular weight distribution index.

[0061] The reaction temperature of the transesterification reaction can be, for example, 90°C, 95°C, or 100°C, or any value between 90°C and 100°C. Within this temperature range, the reaction kinetics are highly efficient, which facilitates the full reaction of the activated carbonate with the terminal hydroxyl groups of the polyethylene oxide glycol. It also inhibits the degradation of the PEO segments and the occurrence of side reactions, thereby ensuring the structural integrity of the intermediate.

[0062] In step S112, the molar ratio of the dicarbonate-terminated PEO intermediate, MMA monomer, free radical initiator, and chain transfer agent is 1:(150-250):(0.2-0.5):1, for example, 1:150:0.2:1, 1:200:0.3:1, or 1:250:0.5:1. This ratio system is designed to precisely control the length of the PMMA chain segments, the polymerization rate, and the chain growth termination behavior, ensuring the symmetry of the PMMA-b-PEO-b-PMMA triblock copolymer structure and a narrow molecular weight distribution.

[0063] The free radical initiator is either azobisisobutyronitrile or methyl azobisisobutyrate. Both free radical initiators are well soluble in polar organic solvents such as DMSO, forming a uniform reaction system with the PEO carbonate intermediate and MMA monomer, which helps improve the consistency of the polymerization reaction and the purity of the product.

[0064] The chain transfer agent is 2-(dimethylamino)propyl dithiocarbamate or S-1-diethylaminocarbonyl-2-methylpropyl dithiocarbamate. These two types of chain transfer agents belong to the dithiocarbamate class and have Z-group structures (such as dimethylamino and diethylaminocarbonyl) that provide high controllability for MMA. They can form stable intermediates with MMA and maintain a reversible addition-fragmentation equilibrium. They are preferred agents for controlling molecular weight control and terminal structural uniformity in MMA polymerization.

[0065] In step S113, the inert atmosphere may be, for example, nitrogen or argon. The reaction temperature may be, for example, 90°C, 95°C, or 100°C, or any other temperature between 90°C and 100°C. The reaction time may be, for example, 5 hours, 6 hours, or 7 hours, or any other value between 5 hours and 7 hours.

[0066] The embodiment of the present invention first obtains a dicarbonate-terminated PEO intermediate by an ester exchange reaction. The intermediate has structural symmetry and dual active end groups, which effectively avoids the problems of uneven end groups or uncontrollable chain growth direction in traditional free radical polymerization. On this basis, controlled free radical polymerization is used for chain growth, which can achieve uniform growth of PMMA blocks from both ends of the PEO chain, thereby preparing a triblock copolymer PMMA-b-PEO-b-PMMA with a regular structure and symmetrical distribution. The method of the present invention can obtain a polymer product with a total weight-average molecular weight of 30,000 g / mol-50,000 g / mol, a molecular weight distribution index PDI of not more than 1.2, a PMMA block glass transition temperature between 105°C and 115°C, and a PEO block glass transition temperature between -30°C and -20°C.

[0067] In a more preferred embodiment, the interfacial energy shielding agent is a compound system of polymethylhydrogensiloxane and silane-functionalized polyvinyl alcohol. The main chain of the polymethylhydrogensiloxane molecule is composed of silicon-oxygen bonds, and its surface energy is lower than 22mN / m. Its molecular chain is rich in condensable Si-H groups, which can quickly migrate to the interface of PC and PET during the blending process, constructing a low-polarity barrier layer between the two phases, effectively reducing the interfacial tension, and inhibiting the phase separation phenomenon caused by the polarity mismatch between the PC phase and the PET phase, and further alleviating the interfacial residual stress and warpage deformation by forming a flexible lubricating layer. The silane-functionalized polyvinyl alcohol has polyvinyl alcohol as the main chain, is rich in polar hydroxyl structures, has good hydrophilicity and interfacial activity, and introduces a certain degree of hydrophobicity and spatial arrangement ability by grafting silane groups with an organosilicon structure, so that it has the dual functions of polarity transition and structural anchoring. In the PC-PET blend system, silane-functionalized polyvinyl alcohol, on the one hand, forms hydrogen bonds or van der Waals interactions with the ester groups of the PET segments through the main chain hydroxyl groups, thereby improving the polarity transition efficiency. On the other hand, its grafted silane structure and polymethylhydrogensiloxane can form segment associations or physical anchoring effects in the molten state, thereby achieving anchoring and flexibility adjustment of the interface layer, helping to build a stable interface wetting structure and alleviate the problems of interface stress concentration and dimensional deformation caused by polarity mismatch.

[0068] The total addition amount of this composite system accounts for the mass percentage of PC resin and PET resin total amount, for example, can be 0.2wt%, 0.5wt% or 0.8wt%.When mass percentage is lower than 0.2wt%, the distribution density of interfacial energy shielding agent in PC and PET interface region is insufficient, and it is difficult to realize effective continuous coverage, resulting in that the phase interface regulating effect is not obvious, and when mass percentage exceeds 0.8wt%, then it is possible to produce dilution effect to matrix phase, can significantly improve the viscosity of melt blending system, and induce the uneven distribution, phase separation or migration precipitation phenomenon of interface component, thereby affecting the processing fluidity, interfacial stability and product appearance quality of material.This polymethyl hydrogen siloxane is as aforementioned low molecular weight organic matter.The mass ratio of this polymethyl hydrogen siloxane and silane functionalized polyvinyl alcohol is (4-9): 1, for example, can be 4: 1, 5: 1, 7: 1 or 9: 1. The setting of this mass ratio comprehensively considers the dominant function of polymethylhydrogensiloxane in interfacial energy regulation and stress buffering, and the auxiliary role of silane-functionalized polyvinyl alcohol in polarity transition and anchoring, ensuring that the two form a stable synergistic system at the interface of PC and PET.

[0069] The hydrogen content of the Si-H groups in the polymethylhydrogensiloxane is 1wt%-3wt%, for example, 1wt%, 2wt%, or 3wt%. Examples of this polymethylhydrogensiloxane include Shin-Etsu KF-9901 (Hydrogen Dimethicone, 100% active matter) or a customized PMHS product such as SiSiB® HF2050. Controlling the hydrogen content of the Si-H groups in the polymethylhydrogensiloxane within this range not only provides moderate chemical reactivity, enabling effective condensation reactions with interfacial polar groups in the blend system, enhancing the anchoring ability of the wetting layer, but also avoids problems such as heterogeneous crosslinking, increased system viscosity, and decreased processing stability caused by excessive Si-H group content. This ensures the overall structural stability and process operability of the PC-PET blend system while maintaining interface control efficiency.

[0070] The grafting rate of the silane-functionalized polyvinyl alcohol is 15mol%-40mol%, for example, it can be 15mol%, 20mol%, 25mol%, 30mol%, 35mol% or 40mol%. The grafting rate of the silane-functionalized polyvinyl alcohol is 15mol%-40mol%, which means that among the vinyl alcohol units on every 100 polyvinyl alcohol molecular chains, 15-40 units are successfully grafted with silane functional groups. The grafting rate of the silane-functionalized polyvinyl alcohol is controlled within the above range. While maintaining the dispersion of its polar main chain structure, it is possible to introduce an appropriate amount of silane groups that can participate in interfacial reaction or association, thereby achieving synergistic regulation of the interface between PC and PET. Within this grafting rate range, the silane-functionalized polyvinyl alcohol can form hydrogen bonds with the PET chain segments through the main chain hydroxyl groups, and can also undergo chain association with polymethylhydrogensiloxane through the silane structure, thereby constructing a stable wetting interface layer, reducing interphase stress concentration, and improving dimensional stability and processing consistency.

[0071] In one embodiment, the silane-functionalized polyvinyl alcohol is triethoxysilane-grafted polyvinyl alcohol, acryloxysilane-grafted polyvinyl alcohol, or aminopropyltriethoxysilane-grafted polyvinyl alcohol. All three types of silane-functionalized polyvinyl alcohol contain polar groups (hydroxyl, acyloxy, amino, ether, etc.) and can serve as polar bridging components in PC-PET systems. In contrast, some non-polar alkyl silanes (such as methyltriethoxysilane) provide hydrophobicity but lack sufficient interfacial anchoring ability and polar synergistic effects.

[0072] Figure 2 FIG1 shows a schematic flow chart of a method for preparing triethoxysilane graft-modified polyvinyl alcohol according to an embodiment of the present invention. Figure 2 As shown, the preparation method comprises:

[0073] Step S121, adding polyvinyl alcohol (PVA) to a mixed solvent of water and ethanol in a mass ratio of 1:1, heating to 85°C-90°C and stirring for 1.5 hours-2 hours to completely dissolve the polyvinyl alcohol, thereby obtaining a 6 wt%-8 wt% polyvinyl alcohol solution;

[0074] Step S122, slowly adding triethoxysilane dropwise at 65°C-75°C, and then adding sodium acetate / acetic acid buffer to adjust the pH of the system to 5.5±0.3;

[0075] Step S123, stirring at 70°C-75°C for 3h-4h to hydrolyze triethoxysilane to generate Si-OH, which then undergoes alcoholysis and condensation reaction with hydroxyl groups in PVA to generate Si-OC covalent grafted structure;

[0076] Step S124, after cooling the reaction solution to room temperature, slowly pouring it into three times the volume of anhydrous ethanol to precipitate, filtering or centrifuging to separate the solid, and washing it with ethanol / water (95 / 5);

[0077] In step S125 , the precipitated solid is vacuum-dried at 50° C.-60° C. for 8 h-10 h, and then lightly crushed and passed through a 100-mesh sieve to obtain triethoxysilane-grafted polyvinyl alcohol powder.

[0078] In step S122 , the molar ratio of polyvinyl alcohol to triethoxysilane is 1:(0.05-0.2), for example, 1:0.05, 1:0.1, 1:0.15 or 0.2.

[0079] The grafting rate of the triethoxysilane-grafted polyvinyl alcohol prepared by the preparation method of the embodiment of the present invention can be controlled within the range of 15 mol%-40 mol%.

[0080] Figure 3 FIG1 shows a schematic flow chart of a method for preparing polyvinyl alcohol grafted with acryloxysilane according to an embodiment of the present invention. Figure 3 As shown, the preparation method comprises:

[0081] Step S131, adding PVA to deionized water, heating at 85°C-90°C and stirring for 1.5 hours-2 hours to completely dissolve the PVA, to obtain a 5wt%-7wt% PVA aqueous solution;

[0082] Step S132 , slowly adding γ-methacryloxypropyltrimethoxysilane dropwise to the PVA solution at 60° C.-70° C., followed by adding an ammonium persulfate / sodium bisulfite initiator mixture to form a uniform reaction system;

[0083] Step S133, maintaining stirring at 60°C-70°C for 2h-3h, the alkenyl group of γ-methacryloxypropyltrimethoxysilane undergoes graft copolymerization with the free radicals on the PVA chain under the induction of APS, while its -Si(OCH3)3 structure is retained;

[0084] Step S134, the reaction solution is cooled to room temperature, slowly poured into three times the volume of anhydrous ethanol for precipitation, filtered or centrifuged to separate the solid, and washed with ethanol / water (95 / 5);

[0085] Step S135 , vacuum drying the solid precipitated in ethanol at 50° C.-60° C. for 8 h-10 h, then lightly crushing and passing through a 100-mesh sieve to obtain acryloxysilane-grafted PVA powder.

[0086] In step S132 , the molar ratio of PVA to γ-methacryloxypropyltrimethoxysilane is 1:(0.1-0.25), for example, 1:0.1, 1:0.15, 1:0.2, or 0.25.

[0087] The grafting rate of the acryloxysilane-grafted polyvinyl alcohol prepared by the preparation method of the embodiment of the present invention can be controlled within the range of 15 mol%-40 mol%.

[0088] Figure 4 FIG1 shows a schematic flow chart of a method for preparing polyvinyl alcohol grafted with aminopropyltriethoxysilane according to an embodiment of the present invention. Figure 4 As shown, the preparation method comprises:

[0089] Step S141, adding PVA to deionized water, heating and stirring at 85°C-90°C for 1.5 hours-2 hours to completely dissolve the PVA, and obtaining a 5 wt%-7 wt% PVA aqueous solution;

[0090] Step S142, cooling the PVA solution to 55°C ± 2°C, and adjusting the pH of the system to 6.8 ± 0.2 using a weak acid or a weak base;

[0091] Step S143, slowly adding 3-aminopropyltriethoxysilane dropwise at 55° C.-65° C. while maintaining stirring;

[0092] Step S144, raising the temperature to 60°C-70°C and maintaining it for 1.5h-3h to partially hydrolyze 3-aminopropyltriethoxysilane to generate Si-OH, which then undergoes alcoholysis and condensation with PVA-OH to form Si-OC bonds to obtain a grafted product;

[0093] Step S145, the reaction solution is cooled to room temperature, slowly poured into three times the volume of anhydrous ethanol for precipitation, filtered or centrifuged to separate the solid, and washed with ethanol / water (95 / 5);

[0094] Step S146, vacuum drying the precipitated solid at 50° C.-60° C. for 8 h-10 h, taking it out, lightly crushing it and passing it through a 100-mesh sieve to obtain aminopropyltriethoxysilane grafted modified PVA powder.

[0095] In step S143 , the molar ratio of PVA to 3-aminopropyltriethoxysilane is 1:(0.08-0.2), for example, 1:0.08, 1:0.1, 1:0.15 or 0.2.

[0096] The grafting rate of the aminopropyltriethoxysilane grafted modified polyvinyl alcohol prepared by the preparation method of the embodiment of the present invention can be controlled within the range of 15 mol%-40 mol%.

[0097] In one embodiment, the compounding system further includes a synergist. The synergist is aminopropyltriethoxysilane or fluorine-modified alkyl silane. The synergist plays an auxiliary regulatory role in the compounding system and can synergistically enhance the overall performance in the following three aspects: 1) The synergist can form a low-surface-energy thin layer structure with good mobility with polymethylhydrogensiloxane, further reducing the free energy difference between the PC and PET phase interfaces, enhancing the continuity and flexible wetting ability of the interfacial layer, and helping to form a stable polar transition region; 2) On the basis of the good polar anchoring effect already provided by silane-functionalized polyvinyl alcohol, the synergist can provide additional functional sites or microphase association ability, strengthening its spatial anchoring and chain entanglement at the interface, thereby improving the interfacial adhesion stability of the compounding system during multiple thermal cycles or high-shear molding processes; 3) The introduction of the synergist gives the polymethylhydrogensiloxane and silane-functionalized polyvinyl alcohol composite interface layer a stronger stress buffering capacity, effectively reducing the stress accumulation and warpage caused by the difference in thermal shrinkage at the interface, thereby ensuring the dimensional stability of the overall blending system in a thermal cycling environment.

[0098] In certain embodiments, the amount of the synergist added to the total amount of PC resin and PET resin is 0.05wt%-0.1wt%, for example, 0.05wt%, 0.08wt% or 0.1wt%. Under this mass percentage, on the one hand, the synergist has strong surface activity and interfacial migration ability, can be enriched in the PC / PET interface region at very low concentrations, and forms a synergistic effect with the main system of polymethylhydrogensiloxane and silane-functionalized polyvinyl alcohol, effectively reducing interfacial tension and enhancing wettability. On the other hand, if the addition amount is too high, it is easy to cause local excessive cross-linking, interfacial gelation or small molecule precipitation, resulting in melt phase separation or mechanical property degradation. In addition, under thermal cycle load or complex molding conditions, this concentration range can provide sufficient interfacial stress buffering and polarity transition regulation ability, significantly improve dimensional retention and interfacial structure stability, and ensure that the dimensional change rate of the blended material is controlled below 0.4%.

[0099] Figure 5 FIG1 shows a schematic flow chart of a method for preparing a PC-PET plastic with high dimensional stability according to an embodiment of the present invention. Figure 5 As shown, the preparation method comprises:

[0100] Step S151, pre-dispersing the polymer synergist and the interfacial energy shielding agent at 70° C.-90° C. to obtain a premixed phase;

[0101] Step S152, melt-blending the PC resin, the PET resin and the premixed phase at 220° C.-260° C. for 2 min-4 min to obtain a melt blend;

[0102] Step S153: granulate the molten blend to obtain PC-PET plastic particles with a particle size of 2 mm to 4 mm.

[0103] In step S151, the temperature can be, for example, 70°C, 80°C, or 90°C, or any other value between 70°C and 90°C. This temperature range can effectively reduce the viscosity of the polymer synergist and interfacial energy shielding agent, improve their fluidity and mutual solubility in the solution system, avoid local aggregation or agglomeration, and lay the foundation for the continuous and uniform spreading of the subsequent interfacial layer. This pre-dispersion step helps form a composite phase boundary with a pre-oriented and wetting structure, improving their interfacial anchoring efficiency and directional regulation ability during melt blending.

[0104] In step S152, the melt blending temperature can be, for example, 220°C, 240°C, 250°C, or 260°C, or any other value between 220°C and 260°C. The melt blending time can be, for example, 2 minutes, 3 minutes, or 4 minutes, or any other value between 2 minutes and 4 minutes. The melt blending temperature range covers the synergistic processing window of PC and PET, fully achieving fluidity matching and viscosity synergy between the two phases while avoiding decomposition or discoloration problems induced by excessively high temperatures. This time range ensures the promotion of the directional distribution of the polymer synergist in the interface region between PC and PET and the formation of an interfacial harmonic structure, thereby enhancing interfacial wettability and compatibility. In one embodiment, in step S152, the temperatures of the extruder zones from the feed zone to the die zone are 220°C-230°C, 230°C-240°C, 240°C-250°C, and 250°C-260°C, respectively. The screw speed is 80 rpm-150 rpm, for example, 80 rpm, 90 rpm, 120 rpm or 150 rpm.

[0105] In step S153, the granulation process can adopt the cooling strand and pelletizing method, which can be selected according to the configuration of different granulation equipment. The particle size is controlled at 2mm-4mm to ensure the flow stability and metering accuracy of the particles in subsequent drying and processing.

[0106] The following is a detailed description of the specific examples and comparative examples.

[0107] Example 1:

[0108] An embodiment of the present invention provides a PC-PET plastic with high dimensional stability. The PC-PET plastic includes the following components in parts by weight: 40 parts of PC resin, 55 parts of PET resin, 4 parts of polymer synergist, and 1 part of interfacial energy shielding agent.

[0109] The polymer synergist is a PMMA-b-PEO-b-PMMA triblock copolymer. The preparation method of the PMMA-b-PEO-b-PMMA triblock copolymer comprises the following steps:

[0110] 11) Polyethylene oxide (PEG) with a molecular weight of approximately 10,000 g / mol was transesterified with fluorophenyl carbonate in the presence of titanium acetylacetonate catalyst at 90°C to obtain a symmetrical dicarbonate-terminated PEO intermediate. The molar ratio of PEG, fluorophenyl carbonate, and titanium acetylacetonate was 1:2.4:0.02.

[0111] 12) Adding a dicarbonate-terminated PEO intermediate, MMA monomer, azobisisobutyronitrile, and 2-(dimethylamino)propyl dithioformate in a molar ratio of 1:300:0.3:1 to dimethyl sulfoxide to form a reaction system;

[0112] 13) The reaction system was reacted at 90°C under an argon atmosphere for 5 h, and the MMA conversion was controlled to 60±5% to produce a PMMA-b-PEO-b-PMMA triblock copolymer.

[0113] The total weight-average molecular weight of the obtained triblock copolymer is 40,000 g / mol, the polymer distribution index is about 1.11, the mass ratio of PMMA block to PEO block is 3:1, the glass transition temperature of PMMA block is 110°C, and the glass transition temperature of PEO block is -25°C.

[0114] The interfacial energy shielding agent is polymethylhydrogensiloxane (PMSI), which has an interfacial energy of approximately 20 mN / m and a weight-average molecular weight of approximately 5000 g / mol. The commercially available Shin-Etsu KF-9901, with a hydrogen content of 2 wt% in Si-H groups, was used. The mass percentage of PMSI in the combined PC and PET resins was 0.5 wt%.

[0115] The present invention also provides a method for preparing a PC-PET plastic with high dimensional stability, wherein the PC-PET plastic is the aforementioned PC-PET plastic. The preparation method comprises the following steps:

[0116] 21) Pre-dispersing the polymer synergist and the interfacial energy shielding agent at 80° C. to obtain a premixed phase;

[0117] 22) Melt blending the PC resin, PET resin, and premixed phase at 240°C for 3 min to obtain a melt blend, wherein the temperatures of the extruder zones from the feed zone to the die zone are 220°C, 230°C, 240°C, and 250°C, respectively, and the screw speed is 100 rpm;

[0118] 23) The molten blend is granulated to obtain PC-PET plastic particles with a particle size of about 3 mm.

[0119] Figure 6 : shows the gel permeation chromatogram of the triblock copolymer prepared in Example 1 of the present invention. Figure 6 As shown, the top of the main peak appears at 13.8 mL, the corresponding weight average molecular weight Mw is about 40,000 g / mol, the number average molecular weight Mn is about 36,000 g / mol, the polymer distribution index PDI is 1.11, and there is no obvious low molecular weight residual peak, indicating that the product molecular weight distribution is concentrated and the polymerization reaction is well controlled.

[0120] Figure 7 The differential scanning calorimetry (DSC) spectrum of the triblock copolymer prepared in Example 1 of the present invention is shown. Figure 7As shown, the DSC curve exhibits two significant glass transition (Tg) events. The first heat flow baseline inflection point occurs at approximately -25°C, corresponding to the glass transition temperature of the PEO flexible segment, and the second heat flow baseline inflection point is located at approximately 110°C, corresponding to the glass transition temperature of the PMMA rigid segment. The two thermal transition regions appear as independent, well-defined baseline changes on the curve, indicating that the block copolymer possesses good phase separation and independent segment motion. No distinct crystallization peaks or melting endotherms were observed throughout the scanning range, indicating that the resulting polymer material is generally amorphous, consistent with the thermal performance expectations for the triblock random arrangement structure.

[0121] Example 2:

[0122] The difference between the embodiment of the present invention and embodiment 1 is that, in addition to the polymethylhydrogen siloxane in embodiment 1, the interfacial energy shielding agent also includes triethoxysilane grafted modified polyvinyl alcohol. The interfacial energy shielding agent of the embodiment of the present invention is a composite system of polymethylhydrogen siloxane and triethoxysilane grafted modified polyvinyl alcohol. The total addition amount of the composite system accounts for 0.5wt% of the total mass percentage of the total amount of PC resin and PET resin. The mass ratio of polymethylhydrogen siloxane to triethoxysilane grafted modified polyvinyl alcohol is 5:1. The grafting rate of the triethoxysilane grafted modified polyvinyl alcohol is about 25mol%.

[0123] In this embodiment, the preparation method of triethoxysilane grafted modified polyvinyl alcohol comprises the following steps:

[0124] 31) Add polyvinyl alcohol (PVA) to a 1:1 mixture of water and ethanol, heat to 90°C, and stir for 1.5 hours to completely dissolve the PVA, obtaining a 7 wt% PVA solution.

[0125] 32) Slowly add triethoxysilane dropwise at 70°C to control the molar ratio of triethoxysilane to the hydroxyl group in PVA to 0.15:1. Then, add sodium acetate / acetic acid buffer to adjust the pH of the system to 5.5.

[0126] 33) Stir at 70°C for 3 h to hydrolyze triethoxysilane to generate Si-OH, which then undergoes alcoholysis and condensation reaction with the hydroxyl groups in PVA to form a Si-OC covalent graft structure;

[0127] 34) After cooling the reaction solution to room temperature, slowly pour it into three times the volume of anhydrous ethanol to precipitate. Filter or centrifuge to separate the solid, and wash it with ethanol / water (95 / 5).

[0128] The precipitated solid was vacuum dried at 60°C for 10 h and then lightly pulverized through a 100-mesh sieve to obtain triethoxysilane-grafted polyvinyl alcohol powder.

[0129] Figure 8 The triethoxysilane grafted modified polyvinyl alcohol prepared in Example 2 of the present invention is shown. 1 H-NMR spectrum. Figure 8 It can be seen that the Si-CH3 characteristic peak appears at δ≈0.6ppm, with an integral of about 0.75, the -CH2-CH2-Si side chain characteristic peak appears at δ≈1.25ppm, the -CH-OH high-intensity peak of the main chain PVA appears at δ≈3.85ppm, with an integral of about 3, and the residual -OH peak is visible near δ≈5.0ppm. The integral ratio of the Si-CH3 peak to the PVA main chain peak is about 1:3, corresponding to a grafting rate of about 25 mol%.

[0130] Example 3:

[0131] The only difference between this embodiment and Example 2 is that, in addition to polymethylhydrogensiloxane and triethoxysilane-grafted polyvinyl alcohol, the composite system in this embodiment also includes a synergist. The synergist is aminopropyltriethoxysilane. The amount of the synergist added is 0.05 wt% of the total weight of the PC resin and PET resin.

[0132] Comparative Example 1:

[0133] The only difference between Comparative Example 1 and Example 1 is that Comparative Example 1 does not contain a polymer synergist.

[0134] Comparative Example 2:

[0135] The only difference between Comparative Example 2 and Example 1 is that Comparative Example 2 does not contain an interfacial energy shielding agent.

[0136] Comparative Example 3:

[0137] The only difference between Comparative Example 3 and Example 1 is that the polymer distribution index of the PMMA-b-PEO-b-PMMA triblock copolymer is about 1.4, and the polymer only exhibits a broad glass transition region, and two clear glass transition temperatures are not observed, indicating that its block segments fail to form a good phase separation structure and the thermal behavior of the soft segment and the rigid segment is severely coupled.

[0138] Comparative Example 4:

[0139] The only difference between Comparative Example 4 and Example 2 is that the grafting rate of the triethoxysilane-grafted polyvinyl alcohol is 60 mol %.

[0140] Table 1 below shows the comparison results of the PC-PET plastics prepared in various examples and comparative examples.

[0141]

[0142] In Table 1 above, heat deflection temperature was measured under a 1.8 MPa bending load using the ISO 75-2B method. Injection-molded bars (80 mm × 10 mm × 4 mm) were tested at a heating rate of 120°C / h, and the temperature at which the bar deflection reached 0.34 mm was recorded. The coefficient of linear expansion was determined using a thermomechanical analyzer (TMA) with a probe load of 0.02 N according to ASTM E831. Length-temperature data were collected over the temperature range of 25°C to 120°C and subjected to linear regression to calculate the average coefficient of linear expansion α (µm / m·K). Tensile strength was measured using ISO 527-2 Type 1A specimens at a rate of 5 mm / min. Flexural strength was measured using a simple three-point bend test (ISO 178) with a span of 64 mm and a rate of 2 mm / min on 80 mm × 10 mm × 4 mm bars. Notched Izod impact strength is measured in kJ / m. 2 80mm × 10mm × 4mm V-notched bars were tested using a Charpy impact tester (impact energy 5 J) according to ISO 179-1 / 1eA (23°C). The average value was calculated to one decimal place. Dimensional change was determined according to ISO 16750-4 using a thermal cycling C-profile of -40°C and 90°C, with a ramp rate of 5K / min and 30-minute hold times for 20 cycles. A complete point cloud of a 120mm × 80mm × 2mm injection-molded plaque was acquired using 3D structured light scanning (accuracy ±3µm). The maximum linear dimensional change (ΔL / L0 × 100%) was calculated by comparing the scanned area with the initial model. All results are based on the arithmetic average of five independent specimens. Molding shrinkage testing was conducted according to ISO 294-4. Specimens were prepared using a standard injection mold (ISO 527-2 Type 1A) under typical molding conditions. The difference between the molded part and the mold dimensions was measured using a high-precision caliper (resolution 0.01mm).

[0143] As shown in Table 1, the dimensional changes of Examples 1 to 3 were 0.32%, 0.25%, and 0.20%, respectively, while those of the four comparative examples were all greater than or equal to 0.38%. Comparative Example 1, which lacked a polymer synergist, achieved a high of 0.78%. This result demonstrates that by constructing a two-component interface control system consisting of a polymer synergist and an interfacial energy shielding agent, the dimensional stability of PC-PET blends can be significantly improved without relying on fillers. The dimensional change rate under thermal cycling is effectively controlled to within ±0.4%, demonstrating excellent dimensional stability. This strategy also synergistically enhances the material's heat deformation temperature, tensile and flexural strength, and impact toughness, meeting the dual requirements of dimensional accuracy and mechanical reliability for high-precision structural parts.

[0144] Furthermore, the molding shrinkage results show that Examples 1 to 3 achieved shrinkages of 0.39%, 0.36%, and 0.33%, respectively, significantly superior to Comparative Examples 1 to 4. This result demonstrates that molecular-scale interface regulation can effectively alleviate the stress mismatch at the PC-PET phase boundary during the melt molding cooling process, reducing deformation errors caused by uneven shrinkage. In particular, without the introduction of fillers, the examples of the present invention achieved the goal of controlling the molding shrinkage to less than 0.4%, ensuring the precision and repeatability of plastic molding and providing key evidence for achieving high dimensional stability.

[0145] Similar to the dimensional change rate, the linear thermal expansion coefficient dropped significantly from 7.5 µm / m·K (Comparative Example 1) to 5.6 µm / m·K (Example 3), indicating that the interface regulation system effectively weakened the macroscopic warping driving force caused by the thermal expansion difference between the PC phase and the PET phase.

[0146] In Comparative Example 1, removing the PMMA-b-PEO-b-PMMA resulted in the worst dimensional change rate, with both the heat deformation temperature and the linear expansion coefficient deteriorating simultaneously, confirming that polar bridging and flexible anchoring are the primary factors influencing dimensional stability. In Comparative Example 2, removing the interfacial energy shielding agent increased the dimensional change rate from 0.32% to 0.46%, demonstrating that the low interfacial energy shielding layer plays a key role in suppressing interfacial stress migration.

[0147] The grafting rate in Comparative Example 4 is higher than the range set by the embodiment of the present invention, resulting in a dimensional change rate of ±0.38%, which is significantly degraded compared to the excellent performance of Examples 2 and 3 (less than ±0.25%). This shows that if the grafting rate is too high, the polar functional groups on the PVA main chain are over-shielded, the flexibility of the molecular chain is reduced, and the strain buffering capacity of the material at the interface and the adaptability of the blend interface are reduced. At the same time, the steric hindrance effect brought about by high-density grafting inhibits effective interface intercalation and bonding, and the interface adhesion is also weakened. Therefore, the grafting rate needs to be controlled within the reasonable range set by the embodiment of the present invention in order to ensure good interface affinity and bonding strength while maintaining the flexibility of the molecular chain, and to achieve the optimal balance between dimensional stability and interface coordination ability.

[0148] In Example 3, the introduction of a trace amount of synergist further reduced the dimensional change rate to ±0.20%, demonstrating superior dimensional stability compared to Example 2 (±0.25%). This suggests that the introduction of a trace amount of synergist may have promoted secondary silane condensation reactions and the formation of a lightly cross-linked structure at the interface, helping to improve interfacial bonding strength and enhance the stress buffering capacity of the interface region, further suppressing microscopic strain accumulation and the risk of interfacial loosening during thermal cycling. This, in turn, achieved a higher level of dimensional stability control without compromising material toughness and processability.

[0149] Furthermore, Examples 1 to 3 exhibit significantly better heat deformation temperature, mechanical strength, and dimensional change than all comparative examples. In particular, Example 3 achieves a heat deformation temperature of 130°C, while its tensile strength, flexural strength, and notched impact strength are each approximately 6%-15% higher than those of the comparative examples. This demonstrates that the synergistic interfacial network formed by the polymer synergist, interfacial energy shielding agent, and trace synergist can maintain uniform wetting and a flexible transition between the PC and PET phases during melt blending and subsequent thermal cycling. This reduces interfacial stress concentration and micro-warping, thereby preventing premature destabilization of the matrix continuous phase under thermal-mechanical loads. Furthermore, it comprehensively enhances the material's heat resistance and toughness, enabling the plastic to achieve higher load-bearing strength and impact safety margins while maintaining high dimensional stability.

[0150] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A PC-PET plastic with high dimensional stability, characterized in that: It comprises the following components in parts by weight: 40-60 parts of PC resin; 40-60 parts of PET resin; 0.5-5 parts of polymer synergist; 0.2-2 parts of interfacial energy shielding agent; The polymer synergist is a copolymer comprising a PMMA block and a PEO block, wherein the PMMA block has polar compatibility with the PC phase, the PEO block forms a van der Waals interaction or a hydrogen bond interaction with the ester group in the PET phase, the mass ratio of the PMMA block to the PEO block is (3-4):1, and the polymer synergist is a PMMA-b-PEO-b-PMMA triblock copolymer; The interfacial energy shielding agent contains a low-molecular-weight organic matter with a silicon-oxygen structure, and the interfacial energy of the low-molecular-weight organic matter is less than 22 mN / m. The weight-average molecular weight of the low-molecular-weight organic matter is 3000 g / mol-10000 g / mol. The interfacial energy shielding agent is polymethyl hydrogen siloxane, or a composite system of polymethyl hydrogen siloxane and silane-functionalized polyvinyl alcohol. In the composite system, the grafting rate of the silane-functionalized polyvinyl alcohol is 15 mol%-40 mol%.

2. The PC-PET plastic according to claim 1, characterized in that The total weight average molecular weight of the PMMA-b-PEO-b-PMMA triblock copolymer is 30,000 g / mol-50,000 g / mol; The polymer distribution index of the PMMA-b-PEO-b-PMMA triblock copolymer is not greater than 1.2, wherein the glass transition temperature of the PMMA block is between 105°C and 115°C, and the glass transition temperature of the PEO block is between -30°C and -20°C.

3. The PC-PET plastic according to claim 2, characterized in that The preparation method of the PMMA-b-PEO-b-PMMA triblock copolymer comprises the following steps: The polyethylene oxide glycol and the activated carbonate end-capping agent are subjected to an ester exchange reaction in the presence of a titanate catalyst at a temperature range of 90°C to 100°C to obtain a symmetrical dicarbonate end-capped PEO intermediate; Adding the dicarbonate-terminated PEO intermediate, MMA monomer, free radical initiator and chain transfer agent into dimethyl sulfoxide to form a reaction system; The reaction system is reacted at 90° C.-100° C. under an inert atmosphere for 5 h-7 h to generate a PMMA-b-PEO-b-PMMA triblock copolymer.

4. The PC-PET plastic according to claim 3, characterized in that The activated carbonate end-capping agent is p-nitrophenyl carbonate, fluorophenyl carbonate or NHS-carbonate; The titanate catalyst is tetraisobutoxy titanate, titanium acetylacetonate or titanium isopropoxide; The free radical initiator is azobisisobutyronitrile or methyl azobisisobutyrate; The chain transfer agent is 2-(dimethylamino)propyl dithiocarboxate or S-1-diethylaminocarbonyl-2-methylpropyl dithiocarboxate.

5. The PC-PET plastic according to claim 4, characterized in that The molar ratio of the polyethylene oxide glycol, the activated carbonate end-capping agent and the titanate catalyst is 1:(2.2-2.5):(0.01-0.05); The molar ratio of the dicarbonate-terminated PEO intermediate, the MMA monomer, the free radical initiator and the chain transfer agent is 1:(150-250):(0.2-0.5):

1.

6. The PC-PET plastic according to any one of claims 1 to 5, characterized in that The total addition amount of the compound system accounts for 0.2wt%-0.8wt% of the total amount of PC resin and PET resin. In the compound system, the mass ratio of the polymethyl hydrogen siloxane to the silane functionalized polyvinyl alcohol is (4-9):1; The hydrogen content of the Si—H groups in the polymethylhydrogensiloxane is 1 wt % to 3 wt %.

7. The PC-PET plastic according to claim 6, characterized in that The silane functionalized polyvinyl alcohol is polyvinyl alcohol grafted and modified with triethoxysilane, acryloxysilane or aminopropyltriethoxysilane.

8. The PC-PET plastic according to claim 7, characterized in that The compounding system further includes a synergist, which is aminopropyltriethoxysilane or fluorine-modified alkylsilane. The added amount of the synergist accounts for 0.05wt%-0.1wt% of the total amount of the PC resin and the PET resin.

9. A method for preparing a PC-PET plastic with high dimensional stability as claimed in any one of claims 1 to 8, characterized in that: The steps include: Pre-dispersing the polymer synergist and the interfacial energy shielding agent at 70°C-90°C to obtain a premixed phase; The PC resin, the PET resin and the premixed phase are melt-blended at 220° C. to 260° C. for 2 min to 4 min to obtain a melt blend; The molten blend is granulated to obtain PC-PET plastic particles with a particle size of 2 mm to 4 mm.

10. The preparation method according to claim 9, characterized in that The temperatures of the zones of the extruder from the feed zone to the die zone are 220°C-230°C, 230°C-240°C, 240°C-250°C and 250°C-260°C, respectively, and the screw speed is 80rpm-150rpm.

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