Polystyrene buffer foam based on shear hardening material modification and preparation method thereof

Abstract

The invention discloses a preparation method of polystyrene buffer foam based on shear hardening material modification. The preparation method comprises the following steps: (1) preparing an SHM modifier; (2) preparation of SHM-PS particles; (3) foaming agent injection and secondary granulation; and (4) foaming and forming to obtain the modified polystyrene buffer foam based on the shear hardening material. The invention also discloses the polystyrene buffer foam based on the modification of the shear hardening material, and the polystyrene buffer foam is prepared by any one of the preparation methods of the polystyrene buffer foam based on the modification of the shear hardening material. The material has the following beneficial effects: (1) the material has excellent buffering and energy-absorbing performance; (2) excellent impact damage resistance and fracture toughness;

Description

Technical Field

[0001] This invention relates to the field of polymer materials and functional cushioning materials, specifically to a polystyrene cushioning foam based on shear-hardening material modification and its preparation method. Background Technology

[0002] Expanded polystyrene (EPS) is a lightweight porous material.

[0003] The typical preparation process of polystyrene (EPS) cushioning foam involves mixing polystyrene particles with a foaming agent, heating and expanding the mixture, and then hot-pressing it through a mold to form a network-like foam with a large number of uniformly porous structures. Due to its dense internal microbubbles, EPS cushioning foam exhibits excellent cushioning performance and is widely used in electronic product packaging, automotive component protection, and building insulation. Compared to soft foam materials such as EVA (ethylene-vinyl acetate copolymer) and TPE (thermoplastic elastomer), EPS foam has higher stiffness and strength, providing effective support under static conditions and giving the overall packaging structure structural integrity and load-bearing capacity.

[0004] In terms of impact protection mechanism, polystyrene cushioning foam mainly relies on its three-dimensional porous closed-cell structure to absorb and dissipate externally input impact energy. When subjected to collision or impact, the air bubbles inside the polystyrene cushioning foam first buffer the transmission of shock waves by compressing their internal gas, thereby significantly reducing the impact force; at the same time, the cellular structure of polystyrene cushioning foam undergoes a certain degree of plastic deformation, converting mechanical energy into deformation energy, further weakening the impact force transmitted to the protected object.

[0005] Although polystyrene cushioning foam is widely used in the packaging field, it still has some shortcomings:

[0006] 1. Insufficient energy absorption performance: The energy absorption mechanism of traditional polystyrene cushioning foam mainly relies on the compression of the cell structure and the elastic deformation of the skeleton. However, under high strain rates or instantaneous impact loads, traditional polystyrene cushioning foam is prone to brittle fracture. At the macroscopic level, polystyrene cushioning foam is prone to brittle fracture due to poor interparticle connectivity, resulting in ineffective stress transfer between cells. This makes this type of foam material susceptible to localized structural crushing and fracture. Once localized damage occurs, its cushioning performance drops significantly, thus failing to effectively absorb and disperse external impact energy.

[0007] 2. Insufficient Toughness and Static Strength: Unlike traditional flexible polyurethane foam (PU) and ethylene-vinyl acetate copolymer foam (EVA), polystyrene cushioning foam in packaging applications not only needs to have cushioning and energy absorption capabilities but also a certain static load-bearing capacity to protect internal precision instruments (such as household appliances) from damage caused by static compression. Existing polystyrene cushioning foams generally suffer from poor toughness and weak interparticle bonding, making them prone to breakage and failure under static forces such as bending and compression, as well as impact, thus losing their original static load-bearing capacity. Summary of the Invention

[0008] Objective of the Invention: To address the technical problems of insufficient toughness, static strength, and energy absorption capacity in existing polystyrene cushioning foam materials, this invention discloses a polystyrene cushioning foam modified with shear hardening material (SHM) and its preparation method. The innovation of this invention lies in:

[0009] 1. Construct SHM modifiers with dynamic reversible boron-oxygen (B:O) chemical bonds, enabling them to trigger impact hardening and achieve dynamic modulus enhancement under external impact or high strain rate loading.

[0010] 2. Through a mature internal mixing and blending process, and with the assistance of silane coupling agents, uniform dispersion and interfacial fusion of shear hardening material (SHM) and polystyrene (PS) matrix are achieved;

[0011] 3. After foaming and molding, SHM-EPS composite material can produce a significant modulus jump under impact load. Its energy dissipation mechanism originates from the friction between molecular chains in SHM component and the reversible process of "breakage-reorganization" of dynamic B:O bond.

[0012] This invention significantly improves the load-bearing capacity and buffering energy absorption efficiency of foam materials under impact conditions through the synergistic effect of multi-scale energy dissipation mechanisms, providing an innovative solution for the research and development of high-performance polystyrene cushioning foam.

[0013] Technical solution: A method for preparing polystyrene cushioning foam based on shear-hardening material modification, comprising the following steps (parts by weight):

[0014] (1) Preparation of SHM modifier;

[0015] (2) Preparation of SHM-PS particles

[0016] Place 80-100 parts of polystyrene granules in a mixer and heat them at 160°C to soften for at least 10 minutes. Then, under softening and heating conditions, add 3-15 parts of the SHM modifier obtained in step (1) and continue mixing for at least 30 minutes. After completion, a PS-SHM blend is obtained.

[0017] The above PS-SHM blend was granulated to obtain PS-SHM blend particles;

[0018] (3) Foaming agent injection and secondary granulation

[0019] The foaming agent is injected into the blend through a high-pressure foaming machine, and the PS-SHM secondary blend particles are obtained by secondary extrusion granulation.

[0020] (4) Foaming molding

[0021] (41) Pre-foam the PS-SHM secondary blend particles obtained in step (3), and then proceed to step (42).

[0022] (42) The PS-SHM secondary blend particles after the pre-foaming treatment in step (41) are placed in a mold for mold foaming. After completion, polystyrene buffer foam based on shear hardening material modification is obtained.

[0023] Furthermore, the specific steps of step (1) are as follows:

[0024] (11) Preparation of shear-thickening gel intermediates

[0025] 1-10 parts of boric acid, 100 parts of polydimethylsiloxane with hydroxyl-terminated ends, and 0.1-1 parts of catalyst are mixed by hot melt and subjected to borate esterification reaction under shear force. After the reaction is completed, a polyborosiloxane with a certain degree of crosslinking is generated, which is the shear thickening gel intermediate.

[0026] (12) Preparation of SHM modifier:

[0027] Add 60-80 parts of the shear-thickening gel intermediate obtained in step (11) and 5-15 parts of boron-oxygen coordination enhancer to 5-30 parts of dimethyl silicone oil, and then use a high-temperature kneader to stir it at a constant temperature of 70℃-110℃ for at least 3 hours at a speed of 5-15 rpm to obtain a mixture.

[0028] After the above mixture is cooled to room temperature, an appropriate amount of silane coupling agent is added first, and then an appropriate amount of nano-fumed silica is slowly added in small amounts multiple times. The mixture is stirred at high speed at at least 2000 rpm until homogeneous, and a stable high-viscosity SHM modifier is formed.

[0029] Furthermore, the viscosity of the polydimethylsiloxane with hydroxyl-terminated ends described in step (11) is 50 to 100 cSt, preferably 50 cSt.

[0030] Furthermore, the catalyst described in step (11) is stannous octoate.

[0031] Furthermore, in step (11), the temperature of hot melting is controlled at 150-180°C, and the hot melting time is controlled at 1-5 hours, preferably 2 hours.

[0032] Furthermore, in step (12), the proportion of nano-fumed silica added is 5% to 20% of the total mass of the mixture, preferably 16%.

[0033] Furthermore, in step (12), the average particle size of the nano-fumed silica is 10 nm to 30 nm, preferably 20 nm.

[0034] Furthermore, the viscosity of the dimethyl silicone oil mentioned in step (12) is 180 cSt to 220 cSt.

[0035] Furthermore, the boron-oxygen coordination enhancer mentioned in step (12) is one of 1,4-phenyldiboronic acid and phenylboronic acid, preferably 1,4-phenyldiboronic acid.

[0036] Furthermore, the silane coupling agent in step (12) is γ-methacryloxypropyltrimethoxysilane or alkylphenoxypolyoxyethylene dimethyldiethoxysilane, preferably γ-methacryloxypropyltrimethoxysilane.

[0037] Furthermore, the proportion of the silane coupling agent added in step (12) is 1% to 3% of the total mass of the mixture, preferably 1.5%.

[0038] Furthermore, the density of the polystyrene particles mentioned in step (2) is 1.03–1.05 g / cm³. 3 .

[0039] Furthermore, in step (2), the particle size of the PS-SHM blend particles is 0.4 mm to 0.6 mm.

[0040] Further, the foaming agent mentioned in step (3) is pentane; its addition amount is 4% to 5% of the total mass of PS-SHM blend particles.

[0041] Furthermore, the particle size of the PS-SHM secondary blend particles in step (3) is 0.1 mm to 0.2 mm.

[0042] Furthermore, the process control conditions for pre-foaming in step (41) are as follows:

[0043] Steam pressure: 0.05MPa~0.1MPa, temperature controlled at 95℃~105℃; curing time: 20 hours~36 hours.

[0044] Furthermore, the process control conditions for mold foaming in step (42) are as follows:

[0045] Molding steam pressure: 0.1MPa~0.2MPa, molding time: 10min~25min, mold temperature: 105℃~110℃.

[0046] Polystyrene cushioning foam modified with shear-hardening materials is prepared by any one of the above-described methods for preparing polystyrene cushioning foam modified with shear-hardening materials.

[0047] The boron-oxygen coordination enhancer in step (12) plays a role in enhancing the dynamic coordination crosslinking network of B:O.

[0048] The dimethyl silicone oil in step (12) plays a role in regulating the intermolecular slippage of the system.

[0049] In step (12), the silane coupling agent can improve the compatibility between the SHM modifier and the polystyrene particles (GPPS).

[0050] The high-pressure foaming machine in step (3) injects the foaming agent (liquid pentane) into the PS-SHM blend particles uniformly through high-pressure mixing technology and achieves expansion in the pre-foaming stage. It is an indispensable key equipment in EPS production.

[0051] After step (4) is completed, the polystyrene cushioning foam (SHM-EPS) modified with shear hardening material obtained can be cut into specific sizes according to the usage requirements.

[0052] SHM modifiers exhibit a viscous gel state at room temperature, containing both B:O dynamic coordination bonds and triboroxane rings, which allows for a rapid increase in modulus under high-speed shear or impact. At low impact rates, they exhibit low modulus and viscous (or cold-flow) behavior. When the shear or impact rate exceeds a critical value, the internally contained B:O dynamic crosslinking bonds undergo a chain reaction, increasing the molecular crosslinking density and causing a sharp increase in modulus and hardness. Simultaneously, the "opening-reconnecting" effect of the B:O bonds effectively dissipates impact energy, achieving a buffering and energy absorption effect.

[0053] Beneficial effects: The polystyrene cushioning foam based on shear-hardening material modification and its preparation method disclosed in this invention have the following beneficial effects:

[0054] (1) Excellent buffering and energy absorption performance: The SHM modifier is dispersed in the EPS matrix through intensive mixing. Under impact conditions, it rapidly dissipates a large amount of energy through its own impact hardening effect and the synergistic deformation between multiphase materials, effectively absorbing impact kinetic energy. Furthermore, its instantaneously increased stiffness limits excessive deformation of the foam, thereby suppressing bottoming out. Simultaneously, the impact hardening effect of SHM allows stress waves to be more effectively transmitted to the surrounding areas of the foam material, reducing stress concentration. Under the same buffer material thickness and impact conditions, the peak impact force of the optimized SHM-EPS is reduced by 50%–70% compared to the unoptimized EPS.

[0055] (2) Excellent impact resistance and fracture toughness: After introducing SHM modifier into the EPS matrix, the resulting B:O dynamic cross-linking network can effectively improve the bonding strength between foam particles. At the same time, the impact hardening effect of SHM factor reduces stress concentration and inhibits the propagation of internal cracks in the foam material during impact. Attached Figure Description

[0056] Figure 1 Impact transmission force curves of polystyrene cushioning foam (SHE-EPS 5%) modified with shear hardening material prepared in Example 1 and polystyrene cushioning foam (EPS) as a control example.

[0057] Figure 2 Impact transmission force curves of polystyrene cushioning foam (SHE-EPS10%) modified with shear hardening material prepared in Example 2 and polystyrene cushioning foam (EPS) as a control example. Detailed Implementation

[0058] The specific embodiments of the present invention are described in detail below.

[0059] The "range" disclosed in this invention is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if a range of 10–50 is listed for a specific parameter, it is also expected that ranges of 10–40 and 20–50 are also included. Furthermore, if the minimum range values ​​are 1 and 2, and the maximum range values ​​are 3, 4, and 5, then the following ranges are all expected: 1–3, 1–4, 1–5, 2–3, 2–4, and 2–5. In this application, unless otherwise stated, the numerical range "a–b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0–5" means that all real numbers between "0–5" have been listed herein; "0–5" is merely a shortened representation of these numerical combinations.

[0060] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0061] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0062] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0063] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0064] Unless otherwise specified, the reaction will proceed under normal temperature and pressure conditions.

[0065] Unless otherwise specified, all parts or percentages are by weight or by weight percentage.

[0066] In this invention, all the substances used are known substances that can be purchased or synthesized by known methods.

[0067] In this invention, all the devices or equipment used are conventional devices or equipment known in the art and are readily available.

[0068] Performance evaluation

[0069] The present invention uses the following experimental methods to evaluate the cushioning performance of the optimized foam:

[0070] 1. Drop hammer impact test: Refer to "GB / T 8167-2008 Dynamic compression test method for cushioning materials for packaging" to determine the peak value of the transmitted force of polystyrene foam (SHM-EPS) material under different energy level impacts, compare the cushioning performance of the foam before and after SHM factor optimization, and calculate the reduction rate of peak transmitted force of the optimized SHM-EPS material relative to the unoptimized EPS material to evaluate the optimization effect of SHM factor.

[0071] 2. Pendulum impact test: The impact fracture strength of the long strip SHM-EPS material is measured using a pendulum device to evaluate the impact toughness of the material.

[0072] In one embodiment:

[0073] The preparation method of polystyrene cushioning foam based on shear-hardening material modification includes the following steps, by weight:

[0074] (1) Preparation of SHM modifier;

[0075] (2) Preparation of SHM-PS particles

[0076] Place 80 parts of polystyrene granules (GPPS) in a mixer and heat them at 160°C for 10 minutes. Then, add 3 parts of the SHM modifier obtained in step (1) under softening and heating conditions and continue mixing for 30 minutes. After completion, a PS-SHM blend is obtained.

[0077] The above-mentioned PS-SHM blend was granulated using an integrated mixing and granulation equipment to obtain PS-SHM blend particles;

[0078] (3) Foaming agent injection and secondary granulation

[0079] The foaming agent is injected into the blend through a high-pressure foaming machine, and the PS-SHM secondary blend particles are obtained by secondary extrusion granulation.

[0080] (4) Foaming molding

[0081] (41) Pre-foam the PS-SHM secondary blend particles obtained in step (3), and then proceed to step (42).

[0082] (42) The PS-SHM secondary blend particles after the pre-foaming treatment in step (41) are placed in a mold for mold foaming. After completion, polystyrene buffer foam based on shear hardening material modification is obtained.

[0083] Furthermore, the specific steps of step (1) are as follows:

[0084] (11) Preparation of shear-thickening gel (STG) intermediates

[0085] One part boric acid, 100 parts of hydroxyl-terminated polydimethylsiloxane (PDMS) and 0.1 parts catalyst were mixed by hot melt and subjected to borate esterification reaction under shear force. After the reaction was completed, polyborosiloxane (PBDMS) with a certain degree of crosslinking was generated, which is the shear thickening gel (STG) intermediate.

[0086] (12) Preparation of SHM modifier:

[0087] Add 60 parts of the shear-thickening gel intermediate obtained in step (11) and 5 parts of boron-oxygen coordination enhancer to 5 parts of dimethyl silicone oil, and then use a high-temperature kneader to stir it at 15 rpm for 9 hours under constant temperature of 70℃. After completion, a mixture is obtained.

[0088] After the above mixture is cooled to room temperature, an appropriate amount of silane coupling agent is added first, and then an appropriate amount of nano-fumed silica is slowly added in small amounts multiple times. The mixture is stirred at high speed of 2000 rpm until homogeneous, and a stable high-viscosity SHM modifier is formed.

[0089] Furthermore, the viscosity of the double-hydroxyl-terminated polydimethylsiloxane (PDMS) described in step (11) is 50 cSt.

[0090] Furthermore, the catalyst described in step (11) is stannous octoate (T9).

[0091] Furthermore, in step (11), the temperature of hot melting is controlled at 150°C and the hot melting time is controlled at 5 hours.

[0092] Furthermore, in step (12), the proportion of nano-fumed silica added is 5% of the total mass of the mixture.

[0093] Furthermore, in step (12), the average particle size of the nano-fumed silica is 10 nm.

[0094] Furthermore, the viscosity of the dimethyl silicone oil described in step (12) is 180 cSt.

[0095] Furthermore, the boron-oxygen coordination enhancer mentioned in step (12) is 1,4-phenylenediboric acid.

[0096] Furthermore, the silane coupling agent used in step (12) is γ-methacryloxypropyltrimethoxysilane (KH-570).

[0097] Furthermore, the silane coupling agent added in step (12) is 1% of the total mass of the mixture.

[0098] Furthermore, the density of the polystyrene particles (GPPS) mentioned in step (2) is 1.03 g / cm³. 3 .

[0099] Furthermore, in step (2), the particle size of the PS-SHM blend particles is 0.4 mm.

[0100] Furthermore, the foaming agent mentioned in step (3) is pentane, and its addition amount is 4% of the total mass of PS-SHM blend particles.

[0101] Furthermore, the particle size of the PS-SHM secondary blend particles in step (3) is 0.1 mm.

[0102] Furthermore, the process control conditions for pre-foaming in step (41) are as follows:

[0103] Steam pressure: 0.05MPa, temperature controlled at 95℃; curing time: 36 hours.

[0104] Furthermore, the process control conditions for mold foaming in step (42) are as follows:

[0105] Molding steam pressure: 0.1MPa, molding time: 10min, mold temperature: 110℃.

[0106] Polystyrene cushioning foam modified with shear-hardening materials is prepared by any one of the above-described methods for preparing polystyrene cushioning foam modified with shear-hardening materials.

[0107] In another embodiment:

[0108] The preparation method of polystyrene cushioning foam based on shear-hardening material modification includes the following steps, by weight:

[0109] (1) Preparation of SHM modifier;

[0110] (2) Preparation of SHM-PS particles

[0111] 100 parts of polystyrene granules (GPPS) were placed in a mixer and heated to soften at 160°C for 30 min. Then, 15 parts of the SHM modifier obtained in step (1) were added under softening and heating conditions. The mixing time was continued for 60 min. After completion, PS-SHM blend was obtained.

[0112] The above-mentioned PS-SHM blend was granulated using an integrated mixing and granulation equipment to obtain PS-SHM blend particles;

[0113] (3) Foaming agent injection and secondary granulation

[0114] The foaming agent is injected into the blend through a high-pressure foaming machine, and the PS-SHM secondary blend particles are obtained by secondary extrusion granulation.

[0115] (4) Foaming molding

[0116] (41) Pre-foam the PS-SHM secondary blend particles obtained in step (3), and then proceed to step (42).

[0117] (42) The PS-SHM secondary blend particles after the pre-foaming treatment in step (41) are placed in a mold for mold foaming. After completion, polystyrene buffer foam based on shear hardening material modification is obtained.

[0118] Furthermore, the specific steps of step (1) are as follows:

[0119] (11) Preparation of shear-thickening gel (STG) intermediates

[0120] Ten parts of boric acid, 100 parts of hydroxyl-terminated polydimethylsiloxane (PDMS) and one part of catalyst were mixed by hot melt and subjected to borate esterification reaction under shear force. After the reaction was completed, polyborosiloxane (PBDMS) with a certain degree of crosslinking was generated, which is the shear thickening gel (STG) intermediate.

[0121] (12) Preparation of SHM modifier:

[0122] Add 80 parts of the shear-thickening gel intermediate obtained in step (11) and 15 parts of boron-oxygen coordination enhancer to 30 parts of dimethyl silicone oil, and then use a high-temperature kneader to stir it at 5 rpm for 3 hours under constant temperature of 110°C. After completion, a mixture is obtained.

[0123] After the above mixture is cooled to room temperature, an appropriate amount of silane coupling agent is added first, and then an appropriate amount of nano-fumed silica is slowly added in small amounts multiple times. The mixture is stirred at high speed of 3000 rpm until homogeneous, and a stable high-viscosity SHM modifier is formed.

[0124] Furthermore, the viscosity of the double-hydroxyl-terminated polydimethylsiloxane (PDMS) described in step (11) is 100 cSt.

[0125] Furthermore, the catalyst described in step (11) is stannous octoate (T9).

[0126] Furthermore, in step (11), the temperature of hot melting is controlled at 180°C and the hot melting time is controlled at 1 hour.

[0127] Furthermore, in step (12), the proportion of nano-fumed silica added is 20% of the total mass of the mixture.

[0128] Furthermore, in step (12), the average particle size of the nano-fumed silica is 30 nm.

[0129] Furthermore, the viscosity of the dimethyl silicone oil described in step (12) is 220 cSt.

[0130] Furthermore, the boron-oxygen coordination enhancer mentioned in step (12) is phenylboronic acid.

[0131] Furthermore, the silane coupling agent used in step (12) is alkylphenoxypolyoxyethylene dimethyldiethoxysilane (D738).

[0132] Furthermore, the silane coupling agent added in step (12) is 3% of the total mass of the mixture.

[0133] Furthermore, the density of the polystyrene particles (GPPS) mentioned in step (2) is 1.05 g / cm³. 3 .

[0134] Furthermore, in step (2), the particle size of the PS-SHM blend particles is 0.6 mm.

[0135] Further, the foaming agent mentioned in step (3) is pentane, and its addition amount is 5% of the total mass of PS-SHM blend particles.

[0136] Furthermore, the particle size of the PS-SHM secondary blend particles in step (3) is 0.2 mm.

[0137] Furthermore, the process control conditions for pre-foaming in step (41) are as follows:

[0138] Steam pressure: 0.1 MPa, temperature controlled at 105℃; curing time: 20 hours.

[0139] Furthermore, the process control conditions for mold foaming in step (42) are as follows:

[0140] Molding steam pressure: 0.2MPa, molding time: 25min, mold temperature: 105℃.

[0141] Polystyrene cushioning foam modified with shear-hardening materials is prepared by any one of the above-described methods for preparing polystyrene cushioning foam modified with shear-hardening materials.

[0142] In yet another embodiment:

[0143] The preparation method of polystyrene cushioning foam based on shear-hardening material modification includes the following steps, by weight:

[0144] (1) Preparation of SHM modifier;

[0145] (2) Preparation of SHM-PS particles

[0146] 90 parts of polystyrene granules (GPPS) were placed in a mixer and heated to 160°C for 15 min. Then, 10 parts of the SHM modifier obtained in step (1) were added under the conditions of softening and heating mixing. The mixing time was continued for 45 min. After completion, PS-SHM blend was obtained.

[0147] The above-mentioned PS-SHM blend was granulated using an integrated mixing and granulation equipment to obtain PS-SHM blend particles;

[0148] (3) Foaming agent injection and secondary granulation

[0149] The foaming agent is injected into the blend through a high-pressure foaming machine, and the PS-SHM secondary blend particles are obtained by secondary extrusion granulation.

[0150] (4) Foaming molding

[0151] (41) Pre-foam the PS-SHM secondary blend particles obtained in step (3), and then proceed to step (42).

[0152] (42) The PS-SHM secondary blend particles after the pre-foaming treatment in step (41) are placed in a mold for mold foaming. After completion, polystyrene buffer foam based on shear hardening material modification is obtained.

[0153] Furthermore, the specific steps of step (1) are as follows:

[0154] (11) Preparation of shear-thickening gel (STG) intermediates

[0155] Five parts of boric acid, 100 parts of hydroxyl-terminated polydimethylsiloxane (PDMS), and 0.5 parts of catalyst were mixed by hot melt and subjected to borate esterification reaction under shear force. After the reaction was completed, polyborosiloxane (PBDMS) with a certain degree of crosslinking was generated, which is the shear thickening gel (STG) intermediate.

[0156] (12) Preparation of SHM modifier:

[0157] 70 parts of the shear-thickening gel intermediate obtained in step (11) and 10 parts of boron-oxygen coordination enhancer were added to 20 parts of dimethyl silicone oil. Then, the mixture was stirred at 10 rpm for 4 hours under constant temperature of 80°C using a high-temperature kneader. After completion, a mixture was obtained.

[0158] After the above mixture is cooled to room temperature, an appropriate amount of silane coupling agent is added first, and then an appropriate amount of nano-fumed silica is slowly added in small amounts multiple times. The mixture is stirred at high speed of 2500 rpm until homogeneous, and a stable high-viscosity SHM modifier is formed.

[0159] Furthermore, the viscosity of the double-hydroxyl-terminated polydimethylsiloxane (PDMS) described in step (11) is 80 cSt.

[0160] Furthermore, the catalyst described in step (11) is stannous octoate (T9).

[0161] Furthermore, in step (11), the temperature of hot melting is controlled at 160°C and the hot melting time is controlled at 2 hours.

[0162] Furthermore, in step (12), the proportion of nano-fumed silica added is 16% of the total mass of the mixture.

[0163] Furthermore, in step (12), the average particle size of the nano-fumed silica is 20 nm.

[0164] Furthermore, the viscosity of the dimethyl silicone oil described in step (12) is 200 cSt.

[0165] Furthermore, the boron-oxygen coordination enhancer mentioned in step (12) is 1,4-phenylenediboric acid.

[0166] Furthermore, the silane coupling agent used in step (12) is γ-methacryloxypropyltrimethoxysilane (KH-570).

[0167] Furthermore, in step (12), the addition ratio of the silane coupling agent is 1.5% of the total mass of the mixture.

[0168] Furthermore, the density of the polystyrene particles (GPPS) mentioned in step (2) is 1.04 g / cm³. 3 .

[0169] Furthermore, in step (2), the particle size of the PS-SHM blend particles is 0.5 mm.

[0170] Furthermore, the foaming agent mentioned in step (3) is pentane, and its addition amount is 4.5% of the total mass of PS-SHM blend particles.

[0171] Furthermore, the particle size of the PS-SHM secondary blend particles in step (3) is 0.15 mm.

[0172] Furthermore, the process control conditions for pre-foaming in step (41) are as follows:

[0173] Steam pressure: 0.08 MPa, temperature controlled at 100℃; curing time: 30 hours.

[0174] Furthermore, the process control conditions for mold foaming in step (42) are as follows:

[0175] Molding steam pressure: 0.15MPa, molding time: 20min, mold temperature: 108℃.

[0176] Polystyrene cushioning foam modified with shear-hardening materials is prepared by any one of the above-described methods for preparing polystyrene cushioning foam modified with shear-hardening materials.

[0177] Example 1: Preparation and performance evaluation of EPS foam with 5 wt% SHM modifier.

[0178] The preparation method of polystyrene cushioning foam based on shear-hardening material modification includes the following steps, by weight:

[0179] (1) Preparation of SHM modifier: SHM modifier is a functional reinforcing component with impact hardening effect;

[0180] (11) Preparation of shear-thickening gel (STG) intermediates:

[0181] 50g of boric acid, 1000g of hydroxyl-terminated polydimethylsiloxane (PDMS) with a viscosity of 50cSt, and 2g of stannous octoate catalyst were hot-melt mixed and subjected to a borate esterification reaction under shear force. After the reaction was completed, polyborosiloxane (PBDMS) with a certain degree of crosslinking was generated, which is the shear thickening gel (STG) intermediate.

[0182] The hot melt mixing temperature is 150℃; the hot melt mixing time is 2 hours to ensure that all components are fully mixed.

[0183] (12) Preparation of SHM modifier:

[0184] Weigh 80g of the shear-thickening gel intermediate obtained in step (11), 10g of phenylboronic acid, and 20g of dimethyl silicone oil. Use a high-temperature kneader to stir at 10rpm for 3 hours at a constant temperature of 80℃ to ensure thorough mixing of all components. After cooling to room temperature, gradually add 10g of nano-fumed silica (particle size 20nm) using a high-speed stirrer for 5 minutes at 2000rpm to obtain the SHM modifier.

[0185] (2) Preparation and granulation of SHM-PS particles

[0186] First, add 1000g of GPPS particles into a mixer. The mixing temperature is 160℃ and the mixing time is 10min. After the GPPS softens and clumps together, add 50g of SHM modifier. Maintain the original temperature and continue mixing for 30min before stopping to obtain PS-SHM blend.

[0187] Using an integrated mixing and granulation equipment, the mixed PS-SHM blend is granulated while hot to obtain white, opaque PS-SHM blend particles.

[0188] (3) Foaming agent injection and secondary granulation

[0189] 45g of pentane (blowing agent) was injected into SHM-PS particles using a high-pressure foaming machine, and after secondary granulation, SHM-PS secondary blend particles containing pentane (blowing agent) were obtained.

[0190] (4) Foaming molding

[0191] (41) Pre-foam the PS-SHM secondary blend particles obtained in step (3), and then proceed to step (42).

[0192] (42) The PS-SHM secondary blend particles after the pre-foaming treatment in step (41) are placed in a mold for mold foaming; after completion, a polystyrene buffer foam based on shear hardening material modification with a foaming ratio of 20 times is obtained.

[0193] Furthermore, the process control conditions for pre-foaming in step (41) are as follows:

[0194] Steam pressure: 0.08 MPa, temperature controlled at 100℃; curing time: 30 hours.

[0195] Furthermore, the process control conditions for mold foaming in step (42) are as follows:

[0196] Molding steam pressure: 0.15MPa, molding time: 20min, mold temperature: 108℃.

[0197] Comparative Example:

[0198] The preparation steps for polystyrene cushioning foam (EPS) are as follows:

[0199] (1) 45g of pentane (blowing agent) was injected into 1000g of polystyrene particles (GPPS) using a high-pressure foaming machine to obtain GPPS particles containing pentane (blowing agent).

[0200] (2) Foaming molding

[0201] (21) Pre-foam the GPPS particles obtained in step (1), and then proceed to step (22).

[0202] (22) Place the GPPS particles that have undergone the pre-foaming treatment in step (21) into a mold for mold foaming; after completion, polystyrene cushioning foam (EPS) is obtained.

[0203] Furthermore, the process control conditions for pre-foaming in step (21) are as follows:

[0204] Steam pressure: 0.08 MPa, temperature controlled at 100℃; curing time: 30 hours.

[0205] Furthermore, the process control conditions for mold foaming in step (22) are as follows:

[0206] Molding steam pressure: 0.15MPa, molding time: 20min, mold temperature: 108℃.

[0207] Sample performance evaluation

[0208] According to the performance testing requirements, the polystyrene cushioning foam modified with shear hardening material obtained in Example 1 and the polystyrene cushioning foam (EPS) obtained in the control example were cut into samples of different sizes, such as 100mm×100mm×60mm (drop hammer impact sample) and 150mm×15mm×8mm (pendulum impact sample).

[0209] Drop hammer impact test: The impact force curves of the polystyrene cushioning foam (EPS) samples obtained in Example 1 based on shear-hardening material modification and the control example obtained under an impact energy of 15 J are shown in the attached figure. Figure 1As shown, the peak impact force of the polystyrene (EPS) cushioning foam sample modified with shear-hardening material obtained in Example 1 was 2.1 kN, while the peak impact force of the EPS cushioning foam sample obtained in the control example was 2.6 kN. The peak impact force of the EPS cushioning foam sample modified with shear-hardening material obtained in Example 1 was reduced by 19.2% compared with that of the EPS cushioning foam sample obtained in the control example. Furthermore, comparing the damage to the samples, the damaged area and the degree of back indentation of the EPS cushioning foam sample modified with shear-hardening material obtained in Example 1 were significantly lower than those of the EPS cushioning foam sample obtained in the control example.

[0210] Pendulum impact test: A long strip of foam sample was broken under a pendulum impact energy of 50J, and the energy absorbed during the fracture process was measured. Based on the test results, the impact fracture toughness of the polystyrene cushioning foam (EPS) sample obtained in the comparative example was 6.72 kJ / m. 2 The impact fracture toughness of the polystyrene cushioning foam sample modified with shear-hardening material obtained in Example 1 was 11.65 kJ / m. 2 This represents an increase of 73.3%.

[0211] Example 2: Preparation and performance evaluation of EPS foam with 10 wt% SHM modifier

[0212] The preparation method of polystyrene cushioning foam based on shear-hardening material modification includes the following steps, by weight:

[0213] The operation steps are the same as those in Examples (1) to (4), except that the amount of SHM added is increased from 5 wt% to 10 wt%.

[0214] Sample performance evaluation

[0215] According to the performance testing requirements, the polystyrene cushioning foam modified with shear hardening material obtained in Example 2 and the polystyrene cushioning foam (EPS) obtained in the control example were cut into 100mm×100mm×60mm (drop hammer impact sample) and 150mm×15mm×8mm (pendulum impact sample).

[0216] Drop hammer impact test: The impact force curves of the polystyrene cushioning foam (EPS) samples obtained in Example 2 based on shear-hardening material modification and the control example obtained under an impact energy of 15J are shown in the attached figure. Figure 2As shown, the peak impact force of the polystyrene (EPS) buffer foam sample modified with shear-hardening material obtained in Example 2 was 1.8 kN, while the peak impact force of the EPS buffer foam sample obtained in the control example was 2.6 kN. The peak impact force of the EPS buffer foam sample modified with shear-hardening material obtained in Example 2 was reduced by 30.7% compared with the EPS buffer foam sample obtained in the control example.

[0217] Pendulum impact test: A long strip of foam sample was broken under a pendulum impact energy of 50J, and the energy absorbed during the fracture process was measured. According to the test results, the impact fracture toughness of the polystyrene cushioning foam (EPS) sample obtained in the control example was 6.72kJ / m. 2 The impact fracture toughness of the polystyrene cushioning foam sample modified with shear-hardening material obtained in Example 2 was 14.58 kJ / m. 2 This represents an increase of 116.9%.

[0218] The embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments, and various changes can be made within the scope of knowledge possessed by those skilled in the art without departing from the spirit of the present invention.

Claims

1. A method for preparing polystyrene cushioning foam based on shear-hardening material modification, characterized in that, By weight, the following steps are included: (1) Preparation of SHM modifier; (2) Preparation of SHM-PS particles Place 80-100 parts of polystyrene granules in a mixer and heat them at 160°C to soften for at least 10 minutes. Then, under softening and heating conditions, add 3-15 parts of the SHM modifier obtained in step (1) and continue mixing for at least 30 minutes. After completion, a PS-SHM blend is obtained. The above PS-SHM blend was granulated to obtain PS-SHM blend particles; (3) Foaming agent injection and secondary granulation The foaming agent is injected into the blend through a high-pressure foaming machine, and the PS-SHM secondary blend particles are obtained by secondary extrusion granulation. (4) Foaming molding (41) Pre-foam the PS-SHM secondary blend particles obtained in step (3), and then proceed to step (42). (42) The PS-SHM secondary blend particles after the pre-foaming treatment in step (41) are placed in a mold for mold foaming. After completion, polystyrene buffer foam based on shear hardening material modification is obtained.

2. The method for preparing polystyrene cushioning foam based on shear-hardening material modification as described in claim 1, characterized in that, The specific steps of step (1) are as follows: (11) Preparation of shear-thickening gel intermediates 1-10 parts of boric acid, 100 parts of polydimethylsiloxane with hydroxyl-terminated ends, and 0.1-1 parts of catalyst are mixed by hot melt and subjected to borate esterification reaction under shear force. After the reaction is completed, a polyborosiloxane with a certain degree of crosslinking is generated, which is the shear thickening gel intermediate. (12) Preparation of SHM modifier: Add 60-80 parts of the shear-thickening gel intermediate obtained in step (11) and 5-15 parts of boron-oxygen coordination enhancer to 5-30 parts of dimethyl silicone oil, and then use a high-temperature kneader to stir it at a constant temperature of 70℃-110℃ for at least 3 hours at a speed of 5-15 rpm to obtain a mixture. After the above mixture is cooled to room temperature, an appropriate amount of silane coupling agent is added first, and then an appropriate amount of nano-fumed silica is slowly added in small amounts multiple times. The mixture is stirred at high speed at at least 2000 rpm until homogeneous, and a stable high-viscosity SHM modifier is formed.

3. The method for preparing polystyrene cushioning foam based on shear-hardening material modification as described in claim 2, characterized in that, The viscosity of the hydroxyl-terminated polydimethylsiloxane described in step (11) is 50–100 cSt, preferably 50 cSt, and / or The catalyst mentioned in step (11) is stannous octoate, and / or In step (11), the temperature of hot melting is controlled at 150-180°C, and the hot melting time is controlled at 1-5 hours, preferably 2 hours.

4. The method for preparing polystyrene cushioning foam based on shear-hardening material modification as described in claim 2, characterized in that, In step (12), the addition ratio of nano-fumed silica is 5% to 20% of the total mass of the mixture, preferably 16%, and / or In step (12), the average particle size of the nano-fumed silica is 10 nm to 30 nm, preferably 20 nm, and / or The viscosity of the dimethyl silicone oil mentioned in step (12) is 180 cSt to 220 cSt.

5. The method for preparing polystyrene cushioning foam based on shear-hardening material modification as described in claim 2, characterized in that, The boron-oxygen coordination enhancer mentioned in step (12) is one of 1,4-phenylenediboric acid and phenylboronic acid, preferably 1,4-phenylenediboric acid, and / or The silane coupling agent mentioned in step (12) is γ-methacryloxypropyltrimethoxysilane or alkylphenoxypolyoxyethylene dimethyldiethoxysilane, preferably γ-methacryloxypropyltrimethoxysilane, and / or The addition ratio of the silane coupling agent in step (12) is 1% to 3% of the total mass of the mixture, preferably 1.5%.

6. The method for preparing polystyrene cushioning foam based on shear-hardening material modification as described in claim 1, wherein the density of the polystyrene particles in step (2) is 1.03–1.05 g / cm³. 3 , and / or In step (2), the particle size of the PS-SHM blend particles is 0.4 mm to 0.6 mm.

7. The method for preparing polystyrene cushioning foam based on shear-hardening material modification as described in claim 1, wherein the foaming agent in step (3) is pentane; its addition amount is 4% to 5% of the total mass of PS-SHM blend particles, and / or The particle size of the PS-SHM secondary blend particles mentioned in step (3) is 0.1 mm to 0.2 mm.

8. The preparation method of polystyrene cushioning foam based on shear-hardening material modification as described in claim 1, wherein the pre-foaming process control conditions in step (41) are as follows: Steam pressure: 0.05MPa~0.1MPa, temperature controlled at 95℃~105℃; curing time: 20 hours~36 hours.

9. The preparation method of polystyrene cushioning foam based on shear-hardening material modification as described in claim 1, wherein the process control conditions for mold foaming in step (42) are as follows: Molding steam pressure: 0.1MPa~0.2MPa, molding time: 10min~25min, mold temperature: 105℃~110℃.

10. A polystyrene cushioning foam modified with shear-hardening materials, characterized in that, It is prepared by the method for preparing polystyrene cushioning foam based on shear-hardening material modification as described in any one of claims 1-9.

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