A polystyrene composition, its preparation and application

Abstract

The present invention relates to a polystyrene composition, its preparation and application. The components include polystyrene, styrene-butadiene copolymer, and polyethylene. The polystyrene composition material of the present invention has moderate toughness and is easy to break, and has moderate flexibility.

Description

Technical Field

[0001] The invention belongs to the field of plastic processing, and particularly relates to a polystyrene composition and a preparation and application thereof. Background Art

[0002] During testing, disposable sampling rods are usually used to conduct large-scale sampling of the pharynx, nasal cavity or anus. At the same time, in order to improve the sampling efficiency, the sampling rod of the disposable sampling rod is usually designed to be structurally broken, so that the sampling personnel can easily break the sampling head for storage. However, due to the easy-to-break design of the sampling rod structure, there are stress concentration points on the sampling rod. The sampling rod is very easy to break due to additional forces during the injection molding process, assembly process or transportation process. Even a slight improper force during sampling will cause the rod to break. This places high demands on the operating specifications of the sampler, seriously affecting the efficiency of large-scale testing. Summary of the invention

[0003] In view of the defects of the prior art, the technical problem to be solved by the present invention is to provide a polystyrene composition and its preparation and application.

[0004] A polystyrene composition of the present invention comprises, by weight:

[0005] Polystyrene 100 parts;

[0006] 10-20 parts of styrene-butadiene copolymer;

[0007] Polyethylene 90-120 parts;

[0008] The content of styrene SM structural components in the styrene-butadiene copolymer is greater than 39 wt.%, and the content of styrene SM structural components is tested by infrared quantitative analysis;

[0009] Infrared quantitative analysis method: First, the mixture of polystyrene and polybutadiene with different known proportions was subjected to infrared analysis to establish a standard curve for the determination of styrene / butadiene component content. Then, according to the Lambert-Beer formula, the characteristic peak height of styrene (1602cm -1 ) and the characteristic peak height of butadiene (910cm -1 ) ratio, and the proportion method was used to calculate the content of styrene SM structural component in styrene-butadiene copolymer.

[0010] The weight fraction of styrene-butadiene copolymer is 10 to 20 parts. If the fraction is too small, the notched impact strength is low and the toughness is poor; if the fraction is too large, the notched impact strength is high, the toughness is good, and it is not easy to break. Compared with the low SM structure, the styrene-butadiene copolymer with a high SM structure (the content of the SM structure component > 39 wt.%) has poor compatibility with polyethylene and will be selectively distributed in the polystyrene and polyethylene phases. The styrene-butadiene copolymer with a high SM structure is preferentially distributed in the polystyrene phase, which can effectively improve the toughness of the polystyrene phase. For the styrene-butadiene copolymer with a low SM content, it has a certain compatibility with polystyrene and also with polyethylene, resulting in the material not being easily broken.

[0011] The crystallinity of polyethylene > 55%, and the crystallinity is measured by DSC analysis method.

[0012] Specifically, the crystallinity measured by DSC analysis method is as follows: in a nitrogen atmosphere, under the condition of a heating rate of 10 °C / min, according to the relationship curve between the heat flow and the crystallization time in the exothermic curve, by calculating the ratio of the melting enthalpy of the polyethylene sample to the melting enthalpy of 100% crystalline polyethylene, the crystallinity of polyethylene is obtained.

[0013] The weight fraction of the polyethylene is 90 to 120 parts. If the fraction is too small, the phase separation of the material is not serious, the flexural deflection is too high, and it is not easy to break; if the fraction is too large, the phase separation is serious, the flexural deflection is too low, and it is too easy to break. Compared with low-crystallinity polyethylene, high-crystallinity polyethylene (crystallinity > 55%) has low compatibility with polystyrene. In the present invention, by selecting high-crystallinity polyethylene (crystallinity > 55%), its compatibility with the polystyrene phase is effectively reduced, the flexural deflection of the composite is reduced, and the easy-breaking performance is improved; for low-crystalline polyethylene, it has a certain compatibility with polystyrene, and its composite does not reach the effect of being easily broken.

[0014] Preferably, for the polystyrene, its unnotched Izod impact strength at 23 °C is 9 to 10 KJ / m 2 , and it is tested according to the standard of GB / T 1043.1-2008.

[0015] Preferably, for the polystyrene, according to GB / T 3682.1-2018, its melt index at 200 °C and 5 kg is 3.8 to 8.0 g / 10 min.

[0016] Preferably, the content of the SM structure component in the styrene-butadiene copolymer is 40 - 45 wt.%.

[0017] Preferably, the crystallinity of the polyethylene is 56 - 70%.

[0018] Preferably, by weight fraction, the components include:

[0019] 100 parts of polystyrene;

[0020] 13 - 17 parts of styrene - butadiene copolymer;

[0021] 100 - 110 parts of polyethylene.

[0022] A preparation method of the polystyrene composition of the present invention includes:

[0023] Weigh each component according to the weight ratio, mix them, and extrude and pelletize them by a twin - screw extruder to obtain the polystyrene composition.

[0024] An application of the polystyrene composition of the present invention in a disposable sampling rod.

[0025] The present invention utilizes the partially compatible characteristics among polystyrene, polyethylene, and styrene - butadiene copolymer, and improves the easy - breakage performance of the material by adding high - crystalline polyethylene and styrene - butadiene copolymer with high SM content. By selecting styrene - butadiene copolymer with high SM content, it preferentially distributes in the polystyrene phase, effectively improving the toughness of the polystyrene phase and increasing the impact strength of the material; if styrene - butadiene copolymer with low SM content is selected, it has a certain compatibility with polyethylene and is also compatible with polystyrene, acting as a compatibilizer, then the material cannot achieve the easy - breakage effect. By selecting high - crystallinity polyethylene, the compatibility with polystyrene is reduced, making the composite have the easy - breakage performance; if low - crystallinity polyethylene is selected, it has a certain compatibility with both polystyrene and styrene - butadiene copolymer, and the composite cannot achieve the easy - breakage effect.

[0026] Beneficial effects

[0027] The polystyrene composition of the present invention ensures 12 KJ / m 2 ≤ notched impact ≤ 32 KJ / m 2 Meanwhile, 10 mm ≤ flexural deflection ≤ 30 mm, making the material have moderate toughness and easy to break, with moderate deflection.

[0028] The sampling rod made of the material of the present invention can achieve the easy - breakage effect without the need for a breakage design. Even if there is a breakage structure design, due to the high notched impact strength and good toughness of the material, it is not easily broken by additional forces during the processes of production, transportation, and sampling, greatly reducing the operation threshold for sampling personnel, facilitating popularization and application. At the same time, it is suitable for large - scale and multi - quantity sampling and detection, and has good application prospects. Specific embodiments

[0029] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.

[0030] I. Raw material sources

[0031] A. Polystyrene

[0032] Polystyrene - 1, GPPS152, from Shanghai Secco. According to the standard of GB / T1043.1 - 2008, its notched Izod impact strength under the condition of 23°C is 10 KJ / m 2 ;

[0033] Polystyrene - 2, GPPS123, from Shanghai Secco. According to the standard of GB / T1043.1 - 2008, its notched Izod impact strength under the condition of 23°C is 9 KJ / m 2 ;

[0034] B. Styrene - butadiene copolymer

[0035] Styrene - butadiene copolymer - 1, SBS3545, from Formosa Plastics Corporation, Taiwan, China. According to infrared quantitative analysis method, the content of SM structure (styrene structure) component is 45 wt.%;

[0036] Styrene - butadiene copolymer - 2, SBS3542, from Formosa Plastics Corporation, Taiwan, China. According to infrared quantitative analysis method, the content of SM structure (styrene structure) component is 40 wt.%;

[0037] Styrene - butadiene copolymer - 3, SBS1487, from Formosa Plastics Corporation, Taiwan, China. According to infrared quantitative analysis method, the content of SM structure (styrene structure) component is 55 wt.%;

[0038] Styrene - butadiene copolymer - 4, SBS3537, from Formosa Plastics Corporation, Taiwan, China. According to infrared quantitative analysis method, the content of SM structure (styrene structure) component is 35 wt.%;

[0039] C. Polyethylene:

[0040] Polyethylene - 1, PE HTA001HD5, from ExxonMobil. According to DSC analysis method, its crystallinity is 67%;

[0041] Polyethylene - 2, PE 2426H, from LyondellBasell. According to DSC analysis method, its crystallinity is 56%;

[0042] Polyethylene - 3, PE HMA 016, ExxonMobil, according to DSC analysis, its crystallinity is 71%;

[0043] Polyethylene - 4, PE LL 6101, ExxonMobil, according to DSC analysis, its crystallinity is 44%.

[0044] II. Preparation Method

[0045] Weigh each component according to the weight ratio, then put them into a mixer with a rotation speed of 100 revolutions per minute for dry mixing for 3 - 5 minutes, and then melt - extrude and pelletize the mixed raw materials in a twin - screw extruder with a length - to - diameter ratio of 40:1, temperature range of 160°C, 190°C, 190°C, 200°C, 210°C, 210°C, 210°C, 220°C, 220°C, 220°C, 220°C, and a rotation speed of 450 revolutions per minute to obtain the polystyrene composition.

[0046] III. Test Standards and Methods

[0047] The polystyrene composition is injection - molded into standard test specimens at 200°C and then tested:

[0048] The notched impact is measured according to the standard of GB / T1843 - 2008, test conditions: Type A notch, normal temperature;

[0049] The flexural deflection is measured according to the standard of GB / T9341 - 2008, test conditions: 2mm / min, normal temperature;

[0050] Toughness evaluation: Notched impact < 12 KJ / m 2 , the toughness is too poor; 12 KJ / m 2 ≤ Notched impact ≤ 32 KJ / m 2 , the toughness is moderate; Notched impact > 32 KJ / m 2 , the toughness is too good;

[0051] Flexibility evaluation: Flexural deflection < 10mm, the flexibility is poor; 10mm ≤ Flexural deflection ≤ 30mm, the flexibility is moderate; 30mm < Flexural deflection < 35mm, the flexibility is too good; If it does not break during bending, uniformly take the value of 35mm.

[0052] Table 1 shows the formulation (parts by weight) and performance data of the examples

[0053]

[0054] Table 2 shows the formulation (parts by weight) and performance data of the comparative examples

[0055]

[0056]

[0057] From the above test results, it can be seen that for a special material for a disposable sampling rod with high impact resistance and easy breakage provided by the present invention, its bending deflection is between 10 mm and 30 mm, and the notched impact strength is between 12 KJ / m 2 ~32 KJ / m 2 . It has the characteristics of high notched impact and easy breakage. For a disposable sampling rod made of this material, after the sampling is completed, it can be broken by simply folding it once or bending it to a certain angle, effectively improving the sampling efficiency.

[0058] In Comparative Example 1, a styrene-butadiene copolymer with a low SM content was used. Compared with a styrene-butadiene copolymer with a high SM content, it can improve the compatibility between polystyrene and polyethylene, resulting in the composite being not easily broken.

[0059] In Comparative Example 2, polyethylene with a low crystallinity was used. Compared with polyethylene with a high crystallinity, polyethylene with a low crystallinity has better compatibility with polystyrene, resulting in the composite also being not easily broken.

[0060] In Comparative Example 3, the amount of styrene-butadiene copolymer used was too small, the notched impact strength of the composite was too low, and the toughness was insufficient. Especially for a long sampling rod, it was easy to break during use, with poor flexibility, affecting the actual use and reducing the sampling efficiency.

[0061] In Comparative Example 4, the amount of styrene-butadiene copolymer used was too large, the notched impact strength of the composite was high, and the toughness was good. However, it caused the composite to be too soft, and the sampling rod was also too soft and easy to break, which was not suitable for actual use.

[0062] In Comparative Example 5, the amount of polyethylene used was too small, the phase separation of the composite was not serious, and it could not be broken by bending and was not easily broken.

[0063] In Comparative Example 6, the amount of polyethylene used was too large, the phase separation of the composite was too serious, the bending deflection was too low, the flexibility of the composite was poor, and it was too easy to be broken, which was not suitable for actual use.

Claims

1. A polystyrene composition, characterized in that, by weight parts, the components include: 100 parts of polystyrene; 10 - 20 parts of styrene-butadiene copolymer; 90 - 120 parts of polyethylene; wherein the content of styrene SM structural component in the styrene-butadiene copolymer > 39 wt.%; the crystallinity of the polyethylene > 55%.

2. The composition according to claim 1, characterized in that, The notched Izod impact strength of the polystyrene under the condition of 23°C is 9-10 KJ / m 2 .

3. The composition according to claim 1, characterized in that, the content of styrene SM structural component in the styrene-butadiene copolymer is 40 - 45 wt.%.

4. The composition according to claim 1, characterized in that, the crystallinity of the polyethylene is 56 - 70%.

5. The composition according to claim 1, characterized in that, by weight parts, the components include: 100 parts of polystyrene; 13 - 17 parts of styrene-butadiene copolymer; 100 - 110 parts of polyethylene.

6. A preparation method of the polystyrene composition according to claim 1, comprising: weighing each component according to the weight ratio, mixing, and melt-extruding and pelletizing with a twin-screw extruder to obtain the polystyrene composition.

7. An application of the polystyrene composition according to claim 1 in a disposable sampling rod.

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