Polystyrene alloy foam and method of making same

Abstract

The present application provides a kind of polystyrene alloy foam material and its preparation method, including the following weight parts of each component: 40~65 parts of polystyrene, 20~45 parts of polyethylene, 3~10 parts of toughening agent, 1.5~3 parts of crystallization inhibitor, 4~6 parts of foaming agent and 0.5~1 part of coating agent;Wherein, crystallization inhibitor includes the modified cellobiose and hyperbranched polyester with molar ratio of (1~3):1, modified cellobiose contains active functional group, active functional group includes at least one of hydroxyl, carboxyl, amino and sulfonic acid group.Modified cellobiose active functional group can be bonded with hyperbranched polyester to form hydrogen bond, so that polyethylene molecular chain can be wrapped in the three-dimensional structure formed by modified cellobiose and hyperbranched polyester, and then limit the movement degree of freedom of polyethylene molecular chain, to reduce the crystallinity of polyethylene, it is beneficial to foaming agent can form more larger bubble, so that polystyrene alloy foam material can have high cushioning performance.

Description

Technical Field

[0001] This invention relates to the field of foam materials technology, and mainly to a polystyrene alloy foam material and its preparation method. Background Technology

[0002] Expandable polystyrene (EPS) is a mature foaming material. EPS has advantages such as dimensional stability, mature and stable molding process and low overall cost, and is widely used in home appliance packaging.

[0003] With the development of the home appliance industry, refrigerator products are upgrading towards larger sizes and heavier weights. Under the industry requirements of limiting the overall height of the packaging unit, the market has raised higher standards for the cushioning performance and structural adaptability of packaging cushioning foam. However, traditional EPS materials have inherent technical defects, such as poor welding rate and high brittleness, making them prone to breakage when dropped upon impact, and can no longer meet the cushioning and protection needs of new refrigerator models.

[0004] Currently, to address the performance shortcomings of EPS materials, PS / PE alloy foam materials have become a research and development direction. By introducing polyethylene (PE) components into polystyrene (PS), the properties of PE in absorbing vibration and impact and promoting particle plasticization and bonding, combined with the rigid support advantages of PS, can improve the brittleness problem of EPS. However, PE is a crystalline polymer, and the crystalline regions of PE will affect the foaming ratio of the PS / PE alloy foam system. At the same time, the crystallization rate of PE is relatively slow, which can easily lead to cell collapse and shrinkage during cooling, significantly reducing the cushioning performance of the foam material. Summary of the Invention

[0005] The purpose of this invention is to provide a polystyrene alloy foam material and its preparation method, so as to improve the cushioning performance of the polystyrene alloy foam material.

[0006] To address the aforementioned problems, this invention provides a polystyrene alloy foam material comprising the following components in parts by weight: 40 to 65 parts of polystyrene, 20 to 45 parts of polyethylene, 3 to 10 parts of toughening agent, 1.5 to 3 parts of crystallization inhibitor, 4 to 6 parts of foaming agent, and 0.5 to 1 part of coating agent; wherein the crystallization inhibitor comprises modified cellobiose and hyperbranched polyester in a molar ratio of (1 to 3):1, the modified cellobiose containing active functional groups, the active functional groups including at least one of hydroxyl, carboxyl, amino, and sulfonic acid groups.

[0007] In one embodiment, the modified cellobiose is activated by hydroxylation, carboxylation, amination or sulfonation of cellobiose.

[0008] In one embodiment, the cellobiose is a nanoscale rod-shaped particle with a length of 100 nm to 500 nm, a diameter of 5 nm to 20 nm, an aspect ratio of 10 to 50, and a specific surface area of ​​150 m². 2 / g~600m 2 / g.

[0009] In one embodiment, the hyperbranched polyester comprises at least one of terminal hydroxyl hyperbranched polyester and terminal carboxyl hyperbranched polyester; and / or

[0010] The hyperbranched polyester has a viscosity of 500 mPa·s to 20000 mPa·s and a density of 1.2 ± 0.1 g / cm³. 3 The number-average molecular weight is 1000 g / mol to 20000 g / mol, the molecular weight distribution is 1.2 to 2.5, and the degree of branching is 50% to 70%.

[0011] In one embodiment, the toughening agent includes at least one of EPDM rubber, polyolefin elastomer, styrene-butadiene-styrene block copolymer, styrene-ethylene-butene-styrene block copolymer, acrylate core-shell copolymer, low molecular weight random copolymer of styrene-acrylonitrile, styrene-isoprene-styrene, silicone rubber, and ABS rubber.

[0012] In one embodiment, the foaming agent includes at least one of petroleum ether, pentane, butane, and Freon.

[0013] In one embodiment, the coating agent includes at least one of zinc stearate, calcium stearate, and paraffin wax.

[0014] In one embodiment, the polystyrene has a tensile strength ≥40MPa and a cantilever beam unnotched impact strength ≥6KJ / m. 2 The melt flow index is 1 g / 10 min to 5 g / 10 min at 200℃ and 5 kg load, and the unnotched impact strength of the cantilever beam is ≥6 KJ / m. 2 The Vicat softening point of the polystyrene is ≥88℃.

[0015] In one embodiment, the polyethylene is low-density polyethylene with a density of 0.91 g / cm³. 3 ~0.94g / cm 3 It has a melting point of 105℃~115℃, a tensile strength of ≥15MPa, and an elongation at break of ≥500%.

[0016] A second aspect of the present invention provides a method for preparing a polystyrene alloy foam material, used to prepare the polystyrene alloy foam material as described in any of the above embodiments, wherein the preparation method is as follows: A crystallization inhibitor was obtained by melt extrusion, drying, and granulation of modified cellobiose and hyperbranched polyester in a molar ratio of (1~3):1. Polystyrene alloy foam material is prepared by melt extrusion of 40-65 parts by weight of polystyrene, 20-45 parts by weight of polyethylene, 3-10 parts by weight of toughening agent, 1.5-3 parts by weight of crystallization inhibitor, 4-6 parts by weight of foaming agent and 0.5-1 parts by weight of coating agent.

[0017] In one embodiment, during the melt extrusion process of the modified cellobiose and hyperbranched polyester, the temperature of the melt extrusion is 200°C to 220°C, and the rotation speed during the melt extrusion process is 60 r / min to 100 r / min.

[0018] In one embodiment, during the melt extrusion process of the polystyrene, the polyethylene, the toughening agent, the crystallization inhibitor, the foaming agent, and the coating agent, the melt extrusion temperature is 180°C to 215°C, and the rotation speed during the melt extrusion process is 300 r / min to 400 r / min.

[0019] As can be seen from the above technical solution, the advantages and positive effects of this invention are as follows: By adding cellobiose, high-density heterogeneous nucleation sites are provided for polyethylene. Cellobiose is a small molecule composed of two β-D-glucose molecules linked by β-1,4-glycosidic bonds. Its molecular surface has a large number of polar functional groups such as hydroxyl groups, which can be uniformly dispersed between polyethylene molecular chains, becoming high-density heterogeneous nucleation sites for polyethylene crystallization. This allows polyethylene to undergo a rapid heterogeneous nucleation process, thereby increasing the crystallization rate. Furthermore, due to the significantly increased crystallization rate, the cell walls can be solidified promptly during cooling, allowing the cells in the polystyrene alloy foam material to maintain their shape after molding, thus solving the problems of cell collapse and shrinkage. Further, the active functional groups of the modified cellobiose can not only form polar interactions with the polyethylene molecular chains but also form hydrogen bonds with the hyperbranched polyester, allowing the polyethylene molecular chains to be encapsulated in the three-dimensional structure formed by the modified cellobiose and the hyperbranched polyester. Furthermore, since the crystallization of polyethylene molecular chains is essentially a process in which random molecular chains align into regular crystalline regions through movement, and the three-dimensional network structure can restrict the degree of freedom of movement of polyethylene molecular chains, polyethylene molecular chains cannot freely aggregate and arrange themselves. Even if crystal nuclei can be rapidly formed on the surface of cellobiose, they cannot continue to grow into large crystalline regions. This results in polyethylene forming only a small number of tiny crystalline regions, significantly reducing the overall crystallinity. Consequently, a large number of amorphous regions are retained in the polystyrene / polyethylene system. These amorphous regions provide ample dissolution space for the foaming agent, which is conducive to the formation of more and larger bubbles, increasing the foaming ratio. This results in a loose and uniform porous structure, enabling the polystyrene alloy foam material of this application to possess high cushioning performance and excellent energy absorption and shock absorption performance to meet the needs of household appliance packaging materials. Attached Figure Description

[0020] Figure 1 This is a schematic flowchart of the preparation method of polystyrene alloy foam material in this invention. Detailed Implementation

[0021] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. However, those skilled in the art will understand that the embodiments described below are some embodiments of the present invention, but not all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0022] As used herein, “prepared from” is synonymous with “comprising”. The terms “comprising,” “including,” “having,” “containing,” or any other variations thereof, as used herein, are intended to cover non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such composition, step, method, article, or apparatus.

[0023] When a quantity, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pair of any upper or preferred value with any lower or preferred value, regardless of whether the range is disclosed individually. For example, when the range “1–5” is disclosed, the described range should be interpreted as including ranges “1–4”, “1–3”, “1–2”, “1–2 and 4–5”, “1–3 and 5”, etc. When numerical ranges are described herein, unless otherwise stated, the range is intended to include its endpoints and all integers and fractions within that range.

[0024] In these embodiments, unless otherwise specified, the portions and percentages are all by weight.

[0025] "Parts by mass" refers to the basic unit of measurement that expresses the mass ratio of multiple components. One part can represent any unit mass, such as 1g or 2.689g. If we say that component A has "a" parts by mass and component B has "b" parts by mass, it means the ratio of the mass of component A to the mass of component B is a:b. Alternatively, it can mean that the mass of component A is aK and the mass of component B is bK (where K is any number representing a multiplier). It is important to understand that, unlike parts by mass, the sum of the mass parts of all components is not limited to 100 parts.

[0026] The first aspect of the present invention provides a polystyrene alloy foam material comprising the following components in parts by weight: 40 to 65 parts of polystyrene (PS), 20 to 45 parts of polyethylene (PE), 3 to 10 parts of toughening agent, 1.5 to 3 parts of crystallization inhibitor, 4 to 6 parts of foaming agent, and 0.5 to 1 part of coating agent.

[0027] The crystallization inhibitor comprises a modified cellobiose and a hyperbranched polyester in a molar ratio of (1~3):1. The modified cellobiose contains an active functional group, which includes at least one of hydroxyl, carboxyl, amino, and sulfonic acid groups.

[0028] This application describes the preparation of polystyrene alloy foam materials by adding polyethylene components to polystyrene. Polystyrene is primarily distributed within the particles, with benzene rings providing structural support, thus enabling the polystyrene alloy foam material to possess sufficient structural strength. When applied to appliance packaging materials, this polystyrene alloy foam material can meet the load-bearing requirements during appliance transportation. Polyethylene can act as a stress-absorbing phase, dispersed on the outer layer of the beads to absorb vibration and impact. The combined use of polystyrene and polyethylene enhances the rigid support and flexible cushioning performance of the polystyrene alloy foam material.

[0029] The toughening agent forms a dual toughening system with polyethylene, which further compensates for the brittleness of polystyrene, improves the elongation at break and impact resistance of the material, and does not damage the rigid support properties of polystyrene.

[0030] Specifically, the toughening agent may include at least one of EPDM rubber, polyolefin elastomer, styrene-butadiene-styrene block copolymer, styrene-ethylene-butene-styrene block copolymer, acrylate core-shell copolymer, low molecular weight random copolymer of styrene-acrylonitrile, styrene-isoprene-styrene, silicone rubber, and ABS rubber.

[0031] During the material molding process, the foaming agent generates bubbles, forming a polystyrene alloy foam material with a porous foam structure through a foaming process. This porous foam structure enables compression deformation, achieving shock absorption and energy dissipation, thus providing the foam material with the structural basis for its cushioning properties.

[0032] Specifically, the foaming agent may include at least one of petroleum ether, pentane, butane, and Freon.

[0033] In material molding, coating agents can reduce the adhesion between the material and processing equipment, optimize the material's processability, and prevent production failures caused by adhesion to the wall. Additionally, they can improve the plastic bonding between foam particles, addressing the issue of poor EPS weldability.

[0034] Specifically, the coating agent includes at least one of zinc stearate, calcium stearate, and paraffin wax.

[0035] In this application, by adding a crystallization inhibitor, the crystallization inhibitor can accelerate the reduction of the crystallization rate during the polyethylene molding process and simultaneously accelerate the crystallization speed during the polyethylene molding process, thereby inhibiting high-density heterogeneous nucleation and grain growth, and avoiding the poor cell stability in the polystyrene alloy foam material system from affecting the buffering effect.

[0036] Understandably, polystyrene can be selected from 40 parts to 65 parts by weight. Specifically, the parts by weight of polystyrene include, but are not limited to, 40 parts, 42 parts, 44 parts, 50 parts, 55 parts, and 65 parts. Polyethylene can be selected from 20 parts to 45 parts by weight. Specifically, the parts by weight of polyethylene include, but are not limited to, 20 parts, 21 parts, 23 parts, 28 parts, 30 parts, 35 parts, 37 parts, 42 parts, and 45 parts. Toughening agent can be selected from 3 parts to 10 parts by weight. Specifically, the parts by weight of toughening agent include, but are not limited to, 3 parts, 5 parts, 7 parts, 9 parts, and 10 parts. Crystallization inhibitor can be selected from 1.5 parts to 3 parts; specifically, the parts by weight of crystallization inhibitor include, but are not limited to, 1.5 parts, 1.8 parts, 2 parts, 2.5 parts, and 3 parts. Foaming agent can be selected from 4 parts to 6 parts; specifically, the parts by weight of foaming agent include, but are not limited to, 4 parts, 4.5 parts, 5 parts, 5.5 parts, and 6 parts. The coating agent can be selected from 0.5 parts to 1 part; specifically, the weight parts of the coating agent include, but are not limited to, 0.5 parts, 0.7 parts, and 1 part.

[0037] Furthermore, the crystallization inhibitor comprises a modified cellobiose and a hyperbranched polyester in a molar ratio of (1~3):1. The molar ratio of the modified cellobiose and the hyperbranched polyester can be 1:1, 1.5:1, 2:1, 3:1, or any range of two of the aforementioned ratios. The modified cellobiose contains active functional groups, including at least one of hydroxyl, carboxyl, amino, and sulfonic acid groups.

[0038] Specifically, the modified cellobiose contains at least one active functional group selected from hydroxyl, carboxyl, amino, and sulfonic acid groups. The modified cellobiose can be obtained by modifying cellobiose, and the molecular formula of cellobiose is C2. 12 H 22 O 11 Cellobiose is composed of two β-D-glucopyran rings linearly linked by β-1,4-glycosidic bonds. As a small-molecule sugar with short chains and native hydroxyl groups, it possesses molecular-level dispersion potential and strong polarity, along with an extremely large specific surface area. Therefore, modified cellobiose can act as a heterogeneous nucleating agent for polyethylene molecular chains, significantly increasing the contact interface with the polyethylene polymer. This provides high-density nucleation sites for polyethylene crystallization, lowers the nucleation energy barrier, and accelerates the crystallization rate of polyethylene. This avoids cell collapse and shrinkage caused by slow crystallization during cooling, ensuring the integrity of the cell structure in the material.

[0039] Furthermore, the functional group modification of cellobiose retains the basic structure of disaccharide while introducing additional active functional groups. Modified cellobiose is a small molecule, and its strong polarity makes it prone to aggregation due to intermolecular hydrogen bonds. By compounding cellobiose with hyperbranched polyester, the highly branched three-dimensional structure of the polyester, with hydroxyl and carboxyl groups at the ends of its branches, allows the hydroxyl groups on the surface of the hyperbranched polyester to bond with the active functional groups of modified cellobiose, such as hydroxyl, carboxyl, amino, or sulfonic acid groups, through multi-site hydrogen bonds. This allows the modified cellobiose to graft onto the surface of the hyperbranched polyester molecule in the form of small aggregates, forming a three-dimensional network structure with cellobiose as the cross-linking point. In this way, the three-dimensional branched structure of the hyperbranched polyester forms steric hindrance, which can prevent the modified cellobiose from contacting each other, thus solving the problem of mutual aggregation between the modified cellobiose. This is conducive to the uniform dispersion of crystallization inhibitors at the molecular level in the polystyrene / polyethylene system, making the crystallization control effect consistent in all parts of the material, and avoiding local cell defects and performance fluctuations.

[0040] The molecular structure formed by the reaction between the modified cellobiose in the crystallization inhibitor and the hyperbranched polyester can be referred to in the following simplified structural formula:

[0041] It should be noted that the molecular structure of the modified cellobiose in the above simplified structural formula is as follows:

[0042] In the above simplified structural formula, the molecular structure of hyperbranched polyester is as follows:

[0043] The circular structure in the molecular structure of hyperbranched polyester is represented as follows:

[0044] The three-dimensional network structure formed after the reaction of modified cellobiose and hydroxyl-terminated hyperbranched polyester is as follows:

[0045] From the perspective of inhibiting the crystallinity of PE by crystallization inhibitors, since PE is a crystalline polymer and foaming agents can only dissolve in the amorphous region, the presence of the crystalline region affects the foaming ratio of the polystyrene / polyethylene system. At the same time, a slow crystallization rate will lead to cell collapse and shrinkage, affecting the cushioning performance of the buffer foam.

[0046] In this application, cellobiose is added to provide PE with a high density of heterogeneous nucleation sites. Cellobiose is a small molecule consisting of two β-D-glucose molecules linked by a β-1,4-glycosidic bond. Its molecular surface has numerous polar functional groups such as hydroxyl groups, which can be uniformly dispersed between PE molecular chains, becoming high-density heterogeneous nucleation sites for PE crystallization. This allows PE to undergo a rapid heterogeneous nucleation process, thereby increasing the crystallization rate. Furthermore, due to the significantly increased crystallization rate, the cell walls can be solidified promptly during cooling, allowing the cells in the polystyrene alloy foam to maintain their post-molding shape, thus solving the problems of cell collapse and shrinkage. Further, the active functional groups of the modified cellobiose not only form polar interactions with the PE molecular chains but also form hydrogen bonds with the hyperbranched polyester, enabling the PE molecular chains to be encapsulated in the three-dimensional structure formed by the modified cellobiose and the hyperbranched polyester. Furthermore, since the crystallization of PE molecular chains is essentially a process in which random molecular chains align into regular crystalline regions through movement, and the three-dimensional network structure can restrict the degree of freedom of movement of PE molecular chains, PE molecular chains cannot freely aggregate and arrange themselves. Even if crystal nuclei can be rapidly formed on the surface of cellobiose, they cannot continue to grow into large crystalline regions. This results in PE forming only a small number of tiny crystalline regions, significantly reducing the overall crystallinity. Consequently, a large number of amorphous regions are retained in the polystyrene / polyethylene system. These amorphous regions provide ample dissolution space for the foaming agent, which is conducive to the formation of more and larger bubbles, increasing the foaming ratio. This results in a loose and uniform porous structure, enabling the polystyrene alloy foam material of this application to possess high cushioning performance and excellent energy absorption and shock absorption performance to meet the needs of household appliance packaging materials.

[0047] In some embodiments, the polystyrene alloy foam material prepared in this application can be applied to household appliance packaging materials, specifically, it can be used as refrigerator packaging material.

[0048] In some embodiments, the modified cellobiose is activated by hydroxylation, carboxylation, amination or sulfonation of cellobiose.

[0049] In the molecular structure of cellobiose, there are only inherent hydroxyl groups at the C2, C3, and C6 positions of the glucose ring, and secondary hydroxyl groups are the main ones. The number of hydroxyl groups is small and their activity is low. The hydrogen bonds are formed only by the inherent hydroxyl groups and the hydroxyl or carboxyl groups of the hyperbranched polyester. This results in few sites and weak hydrogen bond binding force, which affects the formation of a dense three-dimensional network of multi-space hydrogen bonds. Moreover, it is easy to break during the high-temperature shearing process of polymer melting and extrusion, and cannot effectively encapsulate the PE molecular chain.

[0050] Modified cellobiose is obtained by activating it through hydroxylation, carboxylation, amination, or sulfonation. This significantly increases the number of active functional groups on the surface of the modified cellobiose, thereby enhancing the hydrogen bond interaction between the cellobiose and the hyperbranched polyester. Simultaneously, it improves the electrostatic and complexation interactions between the cellobiose and the polar sites of the PE molecular chains, providing ample interaction sites for subsequent construction of a three-dimensional network with the hyperbranched polyester and for controlling PE crystallization. Compared to unactivated cellobiose, it binds more tightly to the PE molecular chains and has a more uniform site distribution. The PE molecular chains can form crystal nuclei around the modified cellobiose in a shorter time, resulting in a faster crystallization rate. Moreover, during cooling, the cell walls can solidify more quickly, effectively preventing cell collapse and shrinkage due to delayed solidification, ensuring the integrity of the cell structure, and making the porous buffer structure of the foam material more stable.

[0051] Specifically, cellobiose can be hydroxylated under weakly alkaline conditions. The secondary hydroxyl group of cellobiose undergoes a ring-opening etherification reaction with ethylene oxide. Under weakly alkaline catalysis, the hydroxyl group loses hydrogen ions to form an oxygen anion, which attacks the carbocation of ethylene oxide, and after ring opening, a primary hydroxyl group is generated.

[0052] Carboxylation, amination, or sulfonation activation treatment of cellobiose can be achieved by introducing carboxyl groups (-COOH), amino groups (-NH2), or sulfonic acid groups (-SO3H) onto the cellobiose surface through esterification, amidation, or sulfonation reactions, based on the aforementioned hydroxylation modification. For example, succinic anhydride can be used as a carboxylating agent; the primary hydroxyl group introduced after cellobiose hydroxylation undergoes a ring-opening esterification reaction with succinic anhydride to graft a carboxyl group. Alternatively, 3-aminopropyltriethoxysilane (APTES) can be used as an amination agent; through a silane coupling reaction, an amino group can be grafted onto the hydroxyl site of cellobiose to obtain amination-modified cellobiose. Or, chlorosulfonic acid can be used as a sulfonation agent; at low temperature, it reacts with the hydroxyl groups of cellobiose to introduce sulfonic acid groups.

[0053] It should be noted that the modified cellobiose is activated by hydroxylation, carboxylation, amination or sulfonation of cellobiose, and is not limited to the above methods.

[0054] In some embodiments, cellobiose is in the form of nanoscale rod-shaped particles, with a length of 100 nm to 500 nm, a diameter of 5 nm to 20 nm, an aspect ratio of 10 to 50, and a specific surface area of ​​150 m². 2 / g~600m 2 / g.

[0055] Among them, cellobiose with a nanoscale rod-like structure has a content of 150m. 2 / g~600m 2With a high specific surface area of ​​ / g and moderate steric hindrance of rod-shaped granules, rod-shaped granules are more conducive to the dispersion of cellobiose in the PS / PE melt system compared to spherical and amorphous structures. This allows them to be more uniformly embedded between PE molecular chains. Combined with the steric hindrance of hyperbranched polyester, this further reduces the crystallinity of PE.

[0056] The cellobiose has a length of 100nm~500nm and a diameter of 5nm~20nm. This avoids the problem of cellobiose easily agglomerating due to its small size (length <100nm, diameter <5nm), leading to uneven distribution of nucleation sites and poor local crystallization control. Conversely, if the size is too large (length >500nm, diameter >20nm), it affects the uniform embedding of cellobiose in the interstices of PE molecular chains, resulting in the formation of large local particles. This affects the uniformity of the melt and causes excessive concentration of nucleation sites, leading to uneven solidification of cell walls and easy cracking of cells.

[0057] Furthermore, the aspect ratio of cellobiose is 10-50, and a moderate aspect ratio provides structural support for the three-dimensional network. Specifically, rod-shaped cellobiose, as the cross-linking core of the three-dimensional network, has sufficient spatial support when bonded to hyperbranched polyester, which is conducive to the formation of a continuous and dense three-dimensional network framework. This can further improve the encapsulation and movement restriction of PE molecular chains, and have a stronger inhibitory effect on the crystallinity of PE. If the aspect ratio is >50, the cellobiose is prone to bending and entanglement, affecting dispersibility and the construction of the three-dimensional network; if the aspect ratio is <10, the linear advantage of the rod-shaped structure is lost, and the nucleation sites and support will show a downward trend.

[0058] In some embodiments, the hyperbranched polyester includes at least one of terminal hydroxyl hyperbranched polyester and terminal carboxyl hyperbranched polyester. The hyperbranched polyester may be a terminal hydroxyl hyperbranched polyester alone, a terminal carboxyl hyperbranched polyester alone, or a combination of terminal hydroxyl hyperbranched polyester and terminal carboxyl hyperbranched polyester.

[0059] Among them, hydroxyl-terminated hyperbranched polyester refers to hydroxyl groups attached to the end of the branched chain, and carboxyl-terminated hyperbranched polyester refers to carboxyl groups attached to the end of the branched chain. Hyperbranched polyester uses at least one of hydroxyl-terminated hyperbranched polyester and carboxyl-terminated hyperbranched polyester. The hydroxyl groups and hydroxyl groups are not sterically blocked, and can quickly form hydrogen bonds with the active functional groups of modified cellobiose, which is conducive to the formation of an efficient and stable three-dimensional network structure. Moreover, under the steric hindrance effect of hyperbranched polyester, it can more effectively prevent the aggregation of modified cellobiose, so that the crystallization inhibitor can be uniformly dispersed in the PS / PE alloy system.

[0060] In some embodiments, the hyperbranched polyester has a viscosity of 500 mPa·s to 20000 mPa·s, a density of 1.2 ± 0.1 g / cm3, a number-average molecular weight of 1000 g / mol to 20000 g / mol, a molecular weight distribution of 1.2 to 2.5, and a branching degree of 50% to 70%.

[0061] The viscosity of hyperbranched polyester can be ≥500 mPa·s, enabling it to form a stable and supportive three-dimensional network structure with modified cellobiose through hydrogen bonding. This avoids the problems of loose and easily broken network structures caused by excessively low viscosity and short molecular chains, which would fail to effectively restrict the movement of PE molecular chains. The viscosity of hyperbranched polyester can be ≤20000 mPa·s, giving it excellent flowability in the PS / PE melt system. This facilitates rapid and uniform mixing of hyperbranched polyester with modified cellobiose and avoids problems such as feeding difficulties, wall sticking, and excessive shear force during twin-screw extrusion caused by excessively high melt viscosity.

[0062] The number-average molecular weight determines the chain length and the number of terminal functional groups in hyperbranched polyesters. A number-average molecular weight of 1000 g / mol to 20000 g / mol ensures that hyperbranched polyesters possess sufficient branched segments and terminal functional groups, enabling them to form multi-site hydrogen bonds with modified cellobiose. Simultaneously, steric hindrance effectively prevents the aggregation of modified cellobiose. Furthermore, a molecular weight ≤20000 g / mol in hyperbranched polyesters avoids the problem of excessively long melt chains leading to high melt viscosity and molecular chain entanglement.

[0063] The molecular weight distribution of hyperbranched polyesters can represent the uniformity of the molecular chain length of hyperbranched polyesters. In particular, by selecting hyperbranched polyesters with a molecular weight distribution of 1.2 to 2.5, the uniformity of molecular chain length is made stronger, and the uneven density of the three-dimensional network structure caused by excessive differences in molecular chain length is avoided.

[0064] Branching degree refers to the proportion of branched structures in the total structure of a hyperbranched polyester molecule. The branching degree of hyperbranched polyester can be greater than 50%, resulting in a highly branched three-dimensional structure. This provides sufficient steric hindrance for the three-dimensional structure formed with cellobiose, effectively preventing the aggregation of modified cellobiose. Furthermore, it avoids the situation where the spatial structure of the hyperbranched polyester is too close to that of a linear polyester due to excessively low branching, thus reducing the restriction effect of the three-dimensional structure formed with cellobiose on the degrees of freedom of the PE molecular chain. In addition, by selecting a branching degree of less than 70% for the hyperbranched polyester, excessive steric hindrance of the end functional groups due to excessive branching is avoided, while also ensuring sufficient contact and efficient bonding between the hydroxyl and carboxyl groups and the active functional groups of the modified cellobiose.

[0065] In some embodiments, the tensile strength of polystyrene is ≥40MPa, and the unnotched impact strength of the cantilever beam is ≥6KJ / m. 2 The melt flow index at 200℃ and 5Kg load is 1g / 10min~5g / 10min, and the unnotched impact strength of the cantilever beam is ≥6KJ / m. 2 The Vicat softening point of polystyrene is ≥88℃.

[0066] Because polystyrene serves as the rigid framework of foam materials, using polystyrene with a tensile strength ≥40MPa and an impact strength ≥6KJ / m² allows the prepared foam material to balance rigid support and basic toughness, reducing the brittle defects of pure PS. Specifically, using polystyrene with a tensile strength ≥40MPa ensures sufficient rigidity and mechanical strength for PS, providing stable structural support for the foam material. This meets the load-bearing and compression resistance requirements of large-size, heavy-duty refrigerator packaging, preventing plastic deformation of the packaging liner due to insufficient rigidity during transportation. The cantilever beam unnotched impact strength of polystyrene ≥6KJ / m² gives PS good impact toughness.

[0067] The melt flow index (MFI) of polystyrene (PS) is between 1 g / 10 min and 5 g / 10 min, referring to its fluidity and processability in the molten state. A MFI ≥ 1 g / 10 min ensures sufficient fluidity of PS in the molten state, allowing it to fully melt and mix uniformly with components such as PE, toughening agents, and composite crystallization inhibitors in a twin-screw extruder. This avoids uneven mixing due to excessively high melt viscosity, which can cause localized performance fluctuations in the foam material. Furthermore, a MFI ≤ 5 g / 10 min prevents excessively fluid PS melt, avoiding melt overflow and poor particle formation during extrusion granulation. It also ensures that the molten PS provides sufficient melt strength to effectively encapsulate air bubbles during foaming, preventing cell rupture and collapse due to insufficient melt strength and maintaining the integrity of the cell structure.

[0068] The Vicat softening point reflects the heat distortion temperature and thermal stability of polystyrene. A Vicat softening point ≥88℃ for PS is beneficial in preventing excessive softening and melt collapse during foaming due to high temperatures, maintaining the melt's structural morphology, and ensuring the molding accuracy and dimensional stability of the cells. Specifically, when the prepared polypropylene alloy foam material is used in refrigerator packaging, it will face different environmental temperatures during storage and transportation. A Vicat softening point ≥88℃ helps prevent thermal deformation of the foam material in high-temperature environments (such as summer transportation), ensuring the fit and protective effect of the packaging, and improving the material's environmental adaptability.

[0069] In some embodiments, the polyethylene is low-density polyethylene, and the density of low-density polyethylene is 0.91 g / cm³. 3 ~0.94g / cm 3It has a melting point of 105℃~115℃, a tensile strength of ≥15MPa, and an elongation at break of ≥500%.

[0070] The density is 0.91 g / cm³. 3 ~0.94g / cm 3 Low-density polyethylene (LDPE) has a high degree of molecular chain branching and weak intermolecular forces, resulting in excellent flexibility and elastic deformation capabilities. When LDPE is dispersed on the outer layer of PS beads, it can efficiently absorb vibration and impact energy during the transportation of household appliances through its own elastic deformation, which is beneficial to improving the high cushioning performance of foam materials.

[0071] The elongation at break of low-density polyethylene is ≥500%, which helps the prepared foam material to deform to a certain extent without breaking when subjected to strong impact. This helps to improve the impact resistance and drop resistance of the foam material, meeting the cushioning and protection requirements of heavy refrigerators.

[0072] In the preparation of polystyrene alloy foam, by selecting low-density polyethylene with a melting point of 105℃~115℃, and the processing temperature of the foam material during melt extrusion is 180℃~215℃, which is much higher than the melting point of LDPE, the LDPE can be completely melted during the extrusion process and further uniformly mixed with PS and various additives.

[0073] Since LDPE is a core component of the cell wall, its tensile strength directly determines the cell wall's resistance to rupture. By selecting LDPE with a tensile strength ≥15MPa, it is possible to prevent the cell wall from rupturing due to bubble expansion during foaming caused by insufficient strength, or from experiencing a decrease in cushioning performance due to cell wall rupture upon impact. Simultaneously, the rigidity of LDPE complements that of PS, giving the cell wall both flexible deformation energy absorption and rigid rupture resistance, which helps ensure the stability and integrity of the cell structure. Moreover, the high rigidity and high thermal stability of PS synergistically complement the high flexibility and high cushioning properties of LDPE, solving the problems of insufficient rigidity but insufficient toughness when using EPS alone, and insufficient rigidity but insufficient toughness when using PE alone.

[0074] Figure 1 This is a schematic flowchart of the preparation method of polystyrene alloy foam material in this invention.

[0075] like Figure 1 As shown, the second aspect of this application provides a method for preparing a polystyrene alloy foam material, used to prepare a polystyrene alloy foam material as described in any of the above embodiments. The preparation method is as follows: S100, modified cellobiose and hyperbranched polyester with a molar ratio of (1~3):1, are melt-extruded, dried and granulated to obtain a crystallization inhibitor.

[0076] Specifically, before melt extrusion, the modified cellobiose and hyperbranched polyester were dried in a vacuum drying oven for 10 hours. The melt extrusion process of the modified cellobiose and hyperbranched polyester was carried out by extrusion granulation using a twin-screw extruder. During the melt extrusion process, the temperature of the modified cellobiose and hyperbranched polyester was 200℃~220℃, and the rotation speed was 60r / min~100r / min. The resulting crystallization inhibitor was stored for later use.

[0077] In step S100, a crystallization inhibitor is prepared by compounding modified cellobiose and hyperbranched polyester. During this process, due to the functional groups such as hydroxyl or carboxyl groups in the hyperbranched polyester, the hydroxyl groups of cellobiose are bonded to the activated functional groups of the cross-linked polyester through multi-site hydrogen bonds, forming a three-dimensional network structure with cellobiose as the cross-linking point. This process effectively solves the problem of mutual agglomeration among the modified cellobiose groups. Furthermore, the three-dimensional branched structure of the hyperbranched polyester creates steric hindrance, which facilitates the uniform dispersion of the crystallization inhibitor in the polystyrene alloy foam material in subsequent steps.

[0078] S200: Weigh 40-65 parts by weight of polystyrene, 20-45 parts by weight of polyethylene, 3-10 parts by weight of toughening agent, 1.5-3 parts by weight of crystallization inhibitor, 4-6 parts by weight of foaming agent, and 0.5-1 parts by weight of coating agent, and melt-extrude to prepare polystyrene alloy foam material.

[0079] Specifically, polystyrene, polyethylene, toughening agent, crystallization inhibitor, foaming agent, and coating agent are melt-extruded using a twin-screw extruder. During the melt extrusion process of polystyrene, polyethylene, toughening agent, crystallization inhibitor, foaming agent, and coating agent, the melt extrusion temperature is 180℃~215℃, and the rotation speed during the melt extrusion process is 300r / min~400r / min.

[0080] The melt extrusion process utilizes a twin-screw extruder for granulation, with the foaming agent added via auxiliary equipment. The twin-screw extruder operates at a temperature of 180-200℃ and comprises seven temperature zones: zone 1 (180℃), zone 2 (185℃), zone 3 (200℃), zone 4 (200℃), zone 5 (2100℃), zone 6 (215℃), and zone 7 (215℃). These zone temperatures correspond to the reaction temperatures of different material processing zones.

[0081] In step S200, cellobiose, due to its numerous polar functional groups such as hydroxyl groups on its molecular surface, can be uniformly dispersed between PE molecular chains, becoming high-density heterogeneous nucleation sites for PE crystallization. This allows PE to undergo a rapid heterogeneous nucleation process, thereby increasing the crystallization rate. Furthermore, the active functional groups of the modified cellobiose form hydrogen bonds with the hyperbranched polyester, allowing the PE molecular chains to be encapsulated in the three-dimensional structure formed by the modified cellobiose and the hyperbranched polyester. This restricts the freedom of movement of the PE molecular chains, significantly reducing the crystallinity of the polystyrene alloy foam material. This provides ample dissolution space for the foaming agent, enabling it to form more and larger bubbles, increasing the foam expansion ratio. This results in a loose, uniform porous structure, giving the polystyrene alloy foam material of this application high cushioning performance and excellent energy absorption and shock absorption properties to meet the pressure requirements of household appliance packaging materials.

[0082] The inventors of this application have achieved the preparation of polystyrene alloy foam material by strictly designing the content of each component and the parameters in each step. The preparation method of polystyrene alloy foam material is described below through various embodiments.

[0083] Example 1 The preparation method of polystyrene alloy foam material in this embodiment includes the following steps: S110, modified cellobiose and terminal hydroxyl hyperbranched polyester in a molar ratio of 2:1 were melt extruded, dried and granulated to obtain a crystallization inhibitor. The active functional group of the modified cellobiose includes hydroxyl groups. The melt extrusion temperature was 200℃ and the rotation speed during the melt extrusion process was 60r / min. S210. Weigh out 50 parts by weight of polystyrene, 30 parts by weight of polyethylene, 7 parts by weight of toughening agent EPDM rubber, 3 parts by weight of crystallization inhibitor, 6 parts by weight of foaming agent pentane, and 1 part by weight of coating agent zinc stearate. Melt extrusion is performed using a twin-screw extruder with a processing temperature of 180~200℃. The extruder has seven temperature zones: zone 1 at 180℃, zone 2 at 185℃, zone 3 at 200℃, zone 4 at 200℃, zone 5 at 2100℃, zone 6 at 215℃, and zone 7 at 215℃. The rotation speed during melt extrusion is 300 r / min. Polystyrene alloy foam material is then prepared.

[0084] Example 2 The preparation method of polystyrene alloy foam material in this embodiment includes the following steps: S120, modified cellobiose and terminal hydroxyl hyperbranched polyester in a molar ratio of 3:1 were melt extruded, dried and granulated to obtain a crystallization inhibitor. The active functional group of the modified cellobiose includes hydroxyl groups. The melt extrusion temperature was 200℃ and the rotation speed during the melt extrusion process was 60r / min. S230: Weigh 60 parts by weight of polystyrene, 20 parts by weight of polyethylene, 7 parts by weight of toughening agent EPDM rubber, 3 parts by weight of crystallization inhibitor, 6 parts by weight of foaming agent pentane, and 1 part by weight of coating agent zinc stearate for melt extrusion. The processing temperature of the twin-screw extruder used in the melt extrusion process is 180~200℃. The extruder includes seven temperature zones: zone 1 at 180℃, zone 2 at 185℃, zone 3 at 200℃, zone 4 at 200℃, zone 5 at 2100℃, zone 6 at 215℃, and zone 7 at 215℃. The rotation speed during the melt extrusion process is 300 r / min. Polystyrene alloy foam material is prepared.

[0085] Example 3 The preparation method of polystyrene alloy foam material in this embodiment includes the following steps: S130, modified cellobiose and terminal hydroxyl hyperbranched polyester in a molar ratio of 3:1 were melt extruded, dried and granulated to obtain a crystallization inhibitor. The active functional group of the modified cellobiose includes hydroxyl groups. The melt extrusion temperature was 200℃ and the rotation speed during the melt extrusion process was 60r / min. S230: Weigh 50 parts by weight of polystyrene, 30 parts by weight of polyethylene, 7 parts by weight of toughening agent EPDM rubber, 2 parts by weight of crystallization inhibitor, 6 parts by weight of foaming agent pentane, and 1 part by weight of coating agent zinc stearate for melt extrusion. The processing temperature of the twin-screw extruder used in the melt extrusion process is 180~200℃. The extruder includes seven temperature zones: zone 1 at 180℃, zone 2 at 185℃, zone 3 at 200℃, zone 4 at 200℃, zone 5 at 2100℃, zone 6 at 215℃, and zone 7 at 215℃. The rotation speed during the melt extrusion process is 300 r / min. Polystyrene alloy foam material is prepared.

[0086] Example 4 The preparation method of polystyrene alloy foam material in this embodiment includes the following steps: S140, modified cellobiose and carboxyl-terminated hyperbranched polyester in a molar ratio of 2:1 were melt-extruded, dried and granulated to obtain a crystallization inhibitor. The active functional group of the modified cellobiose includes carboxyl groups. The melt extrusion temperature was 210℃ and the rotation speed during the melt extrusion process was 80 r / min. S240. Weigh 60 parts by weight of polystyrene, 20 parts by weight of polyethylene, 5 parts by weight of toughening agent styrene-butadiene-styrene block copolymer, 3 parts by weight of crystallization inhibitor, 6 parts by weight of foaming agent butane, and 1 part by weight of coating agent calcium stearate for melt extrusion. The processing temperature of the twin-screw extruder used in the melt extrusion process is 180~200℃. The extruder includes seven temperature zones: zone 1 at 180℃, zone 2 at 185℃, zone 3 at 200℃, zone 4 at 200℃, zone 5 at 2100℃, zone 6 at 215℃, and zone 7 at 215℃. The rotation speed during the melt extrusion process is 350 r / min. Polystyrene alloy foam material is prepared.

[0087] Example 5 The preparation method of polystyrene alloy foam material in this embodiment includes the following steps: S150, modified cellobiose and terminal hydroxyl hyperbranched polyester in a molar ratio of 1:1 were melt extruded, dried and granulated to obtain a crystallization inhibitor. The active functional groups of the modified cellobiose include amino groups. The melt extrusion temperature was 220℃ and the rotation speed during the melt extrusion process was 100r / min. S250: Weigh 40 parts by weight of polystyrene, 45 parts by weight of polyethylene, 3 parts by weight of toughening agent styrene-ethylene-butene-styrene block copolymer, 2 parts by weight of crystallization inhibitor, 5 parts by weight of foaming agent petroleum ether, and 0.5 parts by weight of coating agent paraffin wax. Melt extrusion is performed using a twin-screw extruder with a processing temperature of 180~200℃. The extruder has seven temperature zones: zone 1 at 180℃, zone 2 at 185℃, zone 3 at 200℃, zone 4 at 200℃, zone 5 at 2100℃, zone 6 at 215℃, and zone 7 at 215℃. The rotation speed during melt extrusion is 400 r / min. Polystyrene alloy foam material is prepared.

[0088] Example 6 The preparation method of polystyrene alloy foam material in this embodiment includes the following steps: S160, modified cellobiose and terminal hydroxyl hyperbranched polyester in a molar ratio of 3:1 were melt extruded, dried and granulated to obtain a crystallization inhibitor. The active functional group of the modified cellobiose includes sulfonic acid groups. The melt extrusion temperature was 200℃ and the rotation speed during the melt extrusion process was 60r / min. S260. Weigh out 65 parts by weight of polystyrene, 30 parts by weight of polyethylene, 10 parts by weight of toughening agent acrylate core-shell copolymer, 1.5 parts by weight of crystallization inhibitor, 4 parts by weight of foaming agent pentane, and 0.1 parts by weight of coating agent calcium stearate. Melt extrusion is performed using a twin-screw extruder with a processing temperature of 180~200℃. The extruder has seven temperature zones: 180℃ for the first zone, 185℃ for the second zone, 200℃ for the third zone, 200℃ for the fourth zone, 210℃ for the fifth zone, 215℃ for the sixth zone, and 215℃ for the seventh zone. The rotation speed during melt extrusion is 300 r / min. Polystyrene alloy foam material is then prepared.

[0089] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that no crystallization inhibitor was added.

[0090] Weigh out 50 parts by weight of polystyrene, 30 parts by weight of polyethylene, 7 parts by weight of toughening agent EPDM rubber, 6 parts by weight of foaming agent pentane, and 1 part by weight of coating agent zinc stearate for melt extrusion. The processing temperature of the twin-screw extruder used in the melt extrusion process is 180~200℃. The extruder includes seven temperature zones: 180℃ for the first zone, 185℃ for the second zone, 200℃ for the third zone, 200℃ for the fourth zone, 2100℃ for the fifth zone, 215℃ for the sixth zone, and 215℃ for the seventh zone. The rotation speed during the melt extrusion process is 300 r / min. Polystyrene alloy foam material is prepared.

[0091] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that the crystallization inhibitor was replaced with cellobiose.

[0092] Weigh out 50 parts by weight of polystyrene, 30 parts by weight of polyethylene, 7 parts by weight of toughening agent EPDM rubber, 3 parts by weight of cellobiose, 6 parts by weight of foaming agent pentane, and 1 part by weight of coating agent zinc stearate for melt extrusion. The processing temperature of the twin-screw extruder used in the melt extrusion process is 180~200℃. The extruder includes seven temperature zones: 180℃ for the first zone, 185℃ for the second zone, 200℃ for the third zone, 200℃ for the fourth zone, 2100℃ for the fifth zone, 215℃ for the sixth zone, and 215℃ for the seventh zone. The rotation speed during the melt extrusion process is 300 r / min. Polystyrene alloy foam material is prepared.

[0093] Comparative Example 3 The difference between Comparative Example 3 and Example 1 is that the crystallization inhibitor was replaced with a terminal hydroxyl hyperbranched polyester.

[0094] Weigh out 50 parts by weight of polystyrene, 30 parts by weight of polyethylene, 7 parts by weight of toughening agent EPDM rubber, 3 parts by weight of hydroxyl-terminated hyperbranched polyester, 6 parts by weight of foaming agent pentane, and 1 part by weight of coating agent zinc stearate for melt extrusion. The processing temperature of the twin-screw extruder used in the melt extrusion process is 180~200℃. The extruder includes seven temperature zones: zone 1 at 180℃, zone 2 at 185℃, zone 3 at 200℃, zone 4 at 200℃, zone 5 at 2100℃, zone 6 at 215℃, and zone 7 at 215℃. The rotation speed during the melt extrusion process is 300 r / min. Polystyrene alloy foam material is prepared.

[0095] Comparative Example 4 The difference between Comparative Example 4 and Example 1 is that the modified cellobiose in the crystallization inhibitor was replaced with cellobiose.

[0096] S110, a crystallization inhibitor is obtained by melt extrusion, drying and granulation of cellobiose and hyperbranched polyester in a molar ratio of 2:1, wherein the melt extrusion temperature is 200℃ and the rotation speed during the melt extrusion process is 60r / min. S210. 50 parts by weight of polystyrene, 30 parts by weight of polyethylene, 7 parts by weight of toughening agent, 3 parts by weight of crystallization inhibitor, 6 parts by weight of foaming agent, and 1 part by weight of coating agent were melt-extruded. The processing temperature of the twin-screw extruder used in the melt extrusion process was 180~200℃. The extruder included seven temperature zones: zone 1 (180℃), zone 2 (185℃), zone 3 (200℃), zone 4 (200℃), zone 5 (2100℃), zone 6 (215℃), and zone 7 (215℃). The rotation speed during the melt extrusion process was 300 r / min. Polystyrene alloy foam material was prepared. The polystyrene alloy foam materials obtained in Examples 1-6 and Comparative Examples 1-4 were molded with a steam foaming agent to obtain test samples, and the following performance tests were performed: (1) The density of the polystyrene alloy foam material obtained above was determined by the method of GB / T 6343.

[0097] (2) The 10% compression deformation test of the polystyrene alloy foam material obtained above was determined in accordance with the method of GB / T8813.

[0098] (3) The fracture bending strength of the polystyrene alloy foam material obtained above was determined in accordance with the method of GB / T1040.22022.

[0099] (4) The fracture bending strain test of the polystyrene alloy foam material obtained above shall be determined in accordance with the method of GB / T 8812.

[0100] (5) During the process of forming polystyrene alloy foam material with steam foaming agent, record the adjustment temperature of the foaming equipment to obtain the foaming window temperature of polystyrene alloy foam material.

[0101] (6) The dimensional stability of the polystyrene alloy foam material obtained above shall be determined by the method of GB / T8811.

[0102] Table 1 Performance parameters of polystyrene alloy foam materials

[0103] As can be seen from the above data, compared with Comparative Examples 1-4, the density of Examples 1-6 remained unchanged. By adding a crystallization inhibitor, the fracture flexural strain of the polystyrene alloy foam material in these examples was significantly improved. This demonstrates that the polystyrene alloy foam material prepared using a crystallization inhibitor can withstand a greater maximum flexural deformation before fracture, and the less likely the material is to fracture during buffer compression, the stronger its buffering capacity. It should be noted that although the 10% compression deformation in Example 2 was relatively large, the material performance needs to be considered comprehensively. Example 2 showed significant improvements in fracture flexural strain and foaming window temperature, indicating improved buffering performance and better processability.

[0104] Furthermore, Examples 1-6 exhibited lower 10% compressive deformation compared to Comparative Examples 1-4. The 10% compressive deformation index refers to the pressure required for a material to undergo 10% plastic compressive deformation, and its value is negatively correlated with cushioning performance. Therefore, the more easily the polystyrene alloy foam material in Examples 1-6 is compressed to absorb energy, the better its cushioning performance. By using a crystallization inhibitor, the material's cushioning performance is significantly superior to the comparative examples, providing a technical feasibility for thinning the bottom pad of the refrigerator's packaging material.

[0105] The foaming window temperature refers to the temperature range within which polypropylene composite materials can successfully complete foaming and molding, resulting in qualified foam materials with uniform cell structure, no collapse, no cracking, and no shrinkage cavities. The lower the foaming window temperature, the better it is suited to the low-temperature processing requirements of polypropylene. Among them, the foaming window temperatures of Examples 1 to 6 are lower than those of Comparative Examples 1 to 4. This shows that by adding a crystallization inhibitor, the crystallization rate can be accelerated, allowing the polypropylene melt to crystallize quickly and uniformly at lower temperatures, thereby achieving better processing performance.

[0106] On the other hand, in terms of dimensional stability, Examples 1 to 6 are basically the same as Comparative Examples 1 to 4. It can be seen that by adding crystallization inhibitors to prepare polystyrene alloy foam materials, its buffering performance can be improved without affecting its dimensional stability. After the material is formed, there are no obvious problems such as shrinkage cavities, collapse, or warping.

[0107] Data analysis from Examples 1-6 and Comparative Examples 1-4 shows that the addition of crystallization inhibitors improves the forming performance of the alloy material system, resulting in uniform and stable cell structure. Furthermore, the trend of change in fracture bending strength is not obvious. This means that the use of crystallization inhibitors improves the buffering performance of the material while having a small impact on fracture bending strength, enabling the buffer material to possess both buffering performance and non-fracture mechanical properties.

[0108] Furthermore, the performance data from Example 1 and Comparative Examples 1-4 show that: 1.1 In Comparative Example 1, without adding a crystallization inhibitor, the foaming window temperature of the polystyrene alloy foam material increased significantly, which is not conducive to molding and processing. Moreover, the 10% compressive deformation of the polystyrene alloy foam material increased, and the fracture bending strain value was much lower than that of Example 1, indicating that the polystyrene alloy foam material is not easily compressed to absorb energy, and the material is prone to breakage during buffer compression, resulting in a decrease in buffering performance.

[0109] 1.2 Comparative Example 2 used only cellobiose as the crystallization inhibitor, while Comparative Example 3 used only hyperbranched polyester. The 10% compressive deformation and fracture flexural strain of Comparative Examples 2 and 3 were the same as those of Comparative Example 1. This shows that the cushioning performance of the prepared polystyrene alloy foam material was not improved when using only cellobiose or hyperbranched polyester. Furthermore, the foaming window temperature of Comparative Examples 2 and 3 was higher than that of Example 1, and their crystallization rate was not improved, resulting in poor processability.

[0110] 1.3 In Comparative Example 4, where the crystallization inhibitor was unmodified cellobiose and hyperbranched polyester, the 10% compression deformation of the polystyrene alloy foam increased, and the fracture flexural strain value was much lower than that in Example 1. This indicates that the polystyrene alloy foam is not easily compressed to absorb energy, and the material is prone to breakage during buffer compression, resulting in poor buffering performance.

[0111] It is understood that those skilled in the art can make equivalent substitutions or changes to the technical solution and inventive concept of the present invention, and all such changes or substitutions should fall within the protection scope of the present invention.

Claims

1. A polystyrene alloy foam material, characterized in that, It includes the following components in parts by weight: 40 to 65 parts of polystyrene, 20 to 45 parts of polyethylene, 3 to 10 parts of toughening agent, 1.5 to 3 parts of crystallization inhibitor, 4 to 6 parts of foaming agent, and 0.5 to 1 part of coating agent. The crystallization inhibitor comprises a modified cellobiose and a hyperbranched polyester in a molar ratio of (1~3):

1. The modified cellobiose contains an active functional group, which includes at least one of hydroxyl, carboxyl, amino, and sulfonic acid groups.

2. The polystyrene alloy foam material according to claim 1, characterized in that, The modified cellobiose is activated by hydroxylation, carboxylation, amination or sulfonation of cellobiose.

3. The polystyrene alloy foam material according to claim 2, characterized in that, The cellobiose is in the form of nanoscale rod-shaped particles, with a length of 100 nm to 500 nm, a diameter of 5 nm to 20 nm, an aspect ratio of 10 to 50, and a specific surface area of ​​150 m². 2 / g~600m 2 / g.

4. The polystyrene alloy foam material according to claim 1, characterized in that, The hyperbranched polyester includes at least one of hydroxyl-terminated hyperbranched polyester and carboxyl-terminated hyperbranched polyester; and / or The hyperbranched polyester has a viscosity of 500 mPa·s to 20000 mPa·s and a density of 1.2 ± 0.1 g / cm³. 3 The number-average molecular weight is 1000 g / mol to 20000 g / mol, the molecular weight distribution is 1.2 to 2.5, and the degree of branching is 50% to 70%.

5. The polystyrene alloy foam material according to claim 1, characterized in that, The toughening agent includes at least one of EPDM rubber, polyolefin elastomer, styrene-butadiene-styrene block copolymer, styrene-ethylene-butene-styrene block copolymer, acrylate core-shell copolymer, low molecular weight random copolymer of styrene-acrylonitrile, styrene-isoprene-styrene, silicone rubber, and ABS rubber.

6. The polystyrene alloy foam material according to claim 1, characterized in that, The foaming agent includes at least one of petroleum ether, pentane, butane, and Freon; and / or The coating agent includes at least one of zinc stearate, calcium stearate, and paraffin wax.

7. The polystyrene alloy foam material according to claim 1, characterized in that, The polystyrene has a tensile strength ≥40MPa and a cantilever beam unnotched impact strength ≥6KJ / m. 2 The melt flow index is 1 g / 10 min to 5 g / 10 min at 200℃ and 5 kg load, and the unnotched impact strength of the cantilever beam is ≥6 KJ / m. 2 The polystyrene has a Vicat softening point ≥88℃; and / or The polyethylene is low-density polyethylene, and the density of the low-density polyethylene is 0.91 g / cm³. 3 ~0.94g / cm 3 It has a melting point of 105℃~115℃, a tensile strength of ≥15MPa, and an elongation at break of ≥500%.

8. A method for preparing a polystyrene alloy foam material, used to prepare the polystyrene alloy foam material as described in any one of claims 1 to 7, characterized in that, The preparation method is as follows: A crystallization inhibitor was obtained by melt extrusion, drying, and granulation of modified cellobiose and hyperbranched polyester in a molar ratio of (1~3):

1. Polystyrene alloy foam material is prepared by melt extrusion of 40-65 parts by weight of polystyrene, 20-45 parts by weight of polyethylene, 3-10 parts by weight of toughening agent, 1.5-3 parts by weight of crystallization inhibitor, 4-6 parts by weight of foaming agent and 0.5-1 parts by weight of coating agent.

9. The method for preparing polystyrene alloy foam material according to claim 8, characterized in that, During the melt extrusion process of the modified cellobiose and hyperbranched polyester, the temperature of the melt extrusion is 200℃~220℃, and the rotation speed during the melt extrusion process is 60r / min~100r / min.

10. The method for preparing polystyrene alloy foam material according to claim 8, characterized in that, During the melt extrusion process of the polystyrene, the polyethylene, the toughening agent, the crystallization inhibitor, the foaming agent, and the coating agent, the melt extrusion temperature is 180℃~215℃, and the rotation speed during the melt extrusion process is 300r / min~400r / min.

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