Antibacterial and anti-aging polypropylene material and preparation method thereof

Abstract

The invention relates to the technical field of polypropylene, and discloses an antibacterial and anti-aging polypropylene material and a preparation method thereof.The polypropylene material is prepared from, by weight, 100 parts of polypropylene, 1.5-4 parts of chitosan quaternary ammonium salt, 0.6-2 parts of sodium p-styrenesulfonate grafted polypropylene and 0.4-0.7 part of antioxidant; the sodium p-styrenesulfonate grafted polypropylene and the chitosan quaternary ammonium salt generate electrostatic interaction, and as a compatilizer, the compatibility between the chitosan quaternary ammonium salt and the polypropylene material is improved, the antibacterial property of the material is enhanced, and breeding of bacteria and molds can be reduced. Chitosan quaternary ammonium salt and polypropylene have good compatibility, the adverse effect of chitosan quaternary ammonium salt on the mechanical property of polypropylene is reduced, and chitosan quaternary ammonium salt contains a heat-resistant naphthalene ring structure, so that the heat aging resistance of the polypropylene material is improved, and the polypropylene material has good practical application in toilet seat covers and other life bathroom accessories.

Description

Technical Field

[0001] The present invention relates to the technical field of polypropylene, and specifically to an antibacterial and anti-aging polypropylene material and a preparation method thereof. Background Art

[0002] Polypropylene has good mechanical strength, wear resistance and chemical stability, and is widely used in the fields of sanitary ware such as toilet seat covers, hygiene products such as masks, and packaging products such as food wraps. Traditional sanitary ware such as toilets is in long-term contact with moisture, and the environment is humid, which is prone to breeding bacteria and molds, and will affect the physical and mental health of users. The current polypropylene materials have poor antibacterial and mildew-proof properties, and poor hydrophilic and skin-friendly properties, which are not conducive to their practical applications in the fields of sanitary ware and hygiene products.

[0003] Adding antibacterial agents such as chitosan, zinc oxide, and titanium dioxide to polypropylene can solve the problem of its poor antibacterial and other properties. Chitosan, quaternary ammonium salt chitosan, etc. are natural polysaccharide derivatives, which have good biocompatibility and excellent antibacterial properties, and are widely used in polymer materials such as polypropylene, polyurethane, and phenolic resin. Traditional quaternary ammonium salt chitosan is usually prepared by reacting the amino group of chitosan with 2,3-epoxypropyltrimethylammonium chloride, but it has problems such as poor heat resistance. The present invention aims to use quaternary ammonium salt chitosan containing naphthyl group to solve the problems of poor antibacterial and mildew-proof properties, mechanical strength, heat aging resistance and other properties of polypropylene materials. Summary of the Invention

[0004] (1) Technical problems to be solved:

[0005] Aiming at the deficiencies of the prior art, the present invention provides an antibacterial and anti-aging polypropylene material and a preparation method thereof, so that the polyethylene material has excellent antibacterial and mildew-proof properties while maintaining good heat resistance and anti-aging properties.

[0006] (2) Technical solution: An antibacterial and anti-aging polypropylene material and a preparation method thereof, calculated by weight, include 100 parts of polypropylene, 1.5 - 4 parts of chitosan quaternary ammonium salt, 0.6 - 2 parts of styrene sulfonate grafted polypropylene, and 0.4 - 0.7 parts of antioxidant.

[0007] The preparation method is: adding polypropylene, chitosan quaternary ammonium salt, styrene sulfonate grafted polypropylene, and antioxidant into a mixer for mixing, and then in a twin-screw extruder, the temperature of zones 1 - 6 is 160 - 195 °C, the screw speed is 200 - 300 r / min, extruding, and pelletizing to obtain the antibacterial and anti-aging polypropylene material.

[0008] Preferably, the preparation method of chitosan quaternary ammonium salt is as follows: add chitosan to a sodium hydroxide solution with a mass fraction of 30-40%, add isopropanol after stirring, heat to the reaction temperature, then add 2-(naphthalen-1-ylmethyl)oxiran-2-yl(dimethyl)ammonium salt, after stirring and reacting, add hydrochloric acid dropwise to the solution to control the pH to 6.5-7, filter, wash with ethanol, and dry to obtain chitosan quaternary ammonium salt.

[0009] Preferably, by weight, the dosage of the chitosan is 100 parts, and the dosage of 2-(naphthalen-1-ylmethyl)oxiran-2-yl(dimethyl)ammonium salt is 300-600 parts.

[0010] Preferably, the reaction temperature is 80-90 °C, and the reaction time is 12-18 h.

[0011] Preferably, the preparation method of 2-(naphthalen-1-ylmethyl)oxiran-2-yl(dimethyl)ammonium salt is as follows: add 100 parts by weight of N,N-dimethyl-1-(naphthalen-1-yl)methanamine and 59-78 parts by weight of epichlorohydrin to isopropanol, heat to 70-80 °C, react for 4-7 h, perform vacuum distillation, and recrystallize the product in an ethanol aqueous solution to obtain 2-(naphthalen-1-ylmethyl)oxiran-2-yl(dimethyl)ammonium salt. The reaction formula is:

[0012]

[0013] Preferably, the preparation method of sodium styrenesulfonate grafted polypropylene is as follows: add water, sodium p-styrenesulfonate, and benzophenone to ethanol, stir and prepare a grafting solution, control the mass concentration of sodium p-styrenesulfonate in the grafting solution to be 80-300 g / L, and the mass concentration of benzophenone to be 0.06-0.4 g / L, then add a polypropylene film, irradiate and graft under ultraviolet light in a nitrogen atmosphere for 15-30 min, take out the polypropylene film, wash with water and ethanol, and dry to obtain sodium styrenesulfonate grafted polypropylene.

[0014] (III) Technical effects: The present invention uses the epoxy group of 2-(naphthalen-1-ylmethyl)oxiran-2-yl(dimethyl)ammonium salt to react with the amino group of chitosan to obtain chitosan quaternary ammonium salt containing naphthyl groups, and then blends and granulates it with polypropylene and sodium styrenesulfonate grafted polypropylene to obtain an antibacterial and anti-aging polypropylene material.

[0015] The sodium styrene sulfonate grafted polypropylene of the present invention contains sulfonate groups, which have electrostatic interaction with chitosan quaternary ammonium salt, thereby modifying the polypropylene molecular chain on the surface of chitosan quaternary ammonium salt. The sodium styrene sulfonate grafted polypropylene is used as a compatibilizer, improving the compatibility between chitosan quaternary ammonium salt and polypropylene material. Chitosan quaternary ammonium salt is evenly dispersed in the polypropylene material matrix, having more antibacterial active sites, significantly improving the antibacterial performance of the material. It shows high bactericidal performance against Escherichia coli antibacterial rate and Staphylococcus aureus antibacterial rate, can reduce the growth of bacteria and molds, and expands the practical application of polypropylene materials in antibacterial household sanitary ware products.

[0016] The sodium styrene sulfonate grafted polypropylene improves the compatibility between chitosan quaternary ammonium salt and polypropylene, reduces the adverse effect of chitosan quaternary ammonium salt on the mechanical properties of polypropylene, enables the polypropylene material to still have a high tensile strength. And chitosan quaternary ammonium salt contains a heat-resistant naphthalene ring structure, adding it to the polypropylene material is beneficial to improving the heat resistance performance. After heat aging treatment, the polypropylene material can maintain a good tensile strength, showing excellent heat aging performance. And the added sodium styrene sulfonate grafted polypropylene contains sulfonate hydrophilic groups and hydrophilic chitosan quaternary ammonium salt, which can reduce the water contact angle of the polypropylene material, improve the surface hydrophilicity and skin-friendliness, and enhance the user's product experience. The obtained polypropylene material has good practical applications in household sanitary ware products such as toilet seat covers. Specific embodiments

[0017] The present invention will be further described below in conjunction with specific embodiments. The raw materials and reagents used in the following examples and comparative examples are all commercially available products. Polypropylene, model BH3820, Ningbo Keming Plastic Co., Ltd. Chitosan, with an effective ingredient content of 99%, Jiangsu Weizhirun Biotechnology Co., Ltd.

[0018] Example 1

[0019] (1) Add 20 g of N,N-dimethyl-1-(naphthalen-1-yl)methanamine and 11.8 g of epichlorohydrin to 30 mL of isopropanol, heat to 80 °C, react for 4 h, carry out reflux condensation during the reaction, perform vacuum distillation, and recrystallize the product in an ethanol aqueous solution with a volume fraction of 70% to obtain 2-(epoxypropyl)(naphthylmethyl)dimethyl quaternary ammonium salt.

[0020] (2) Add 10 g of chitosan to 25 mL of a sodium hydroxide solution with a mass fraction of 40%, stir and then add isopropanol, heat to 90 °C, then add 30 g of 2-(epoxypropyl)(naphthylmethyl)dimethyl quaternary ammonium salt, stir and react for 12 h, add hydrochloric acid with a mass fraction of 37% dropwise to the solution, control the pH of the solution to 7, filter and wash with ethanol, and dry to obtain chitosan quaternary ammonium salt.

[0021] (3) Add 150 mL of water, sodium p-styrenesulfonate, and benzophenone to 300 mL of ethanol, stir to prepare a grafting solution. Control the mass concentration of sodium p-styrenesulfonate in the grafting solution to be 80 g / L and the mass concentration of benzophenone to be 0.06 g / L. Then add the polypropylene film and irradiate it for grafting under a UV lamp with a power of 600 W in a nitrogen atmosphere for 15 min. Take out the polypropylene film, wash it with water and ethanol, and dry it to obtain sodium p-styrenesulfonate-grafted polypropylene.

[0022] (4) Add 1 kg of polypropylene, 15 g of quaternary ammonium salt of chitosan, 6 g of sodium p-styrenesulfonate-grafted polypropylene, and 6 g of antioxidant 1076 to a mixer and mix them. Then, in a twin-screw extruder, the temperatures of zones 1 - 6 are 160 °C, 170 °C, 185 °C, 195 °C, 195 °C, and 190 °C, the screw speed is 300 r / min, extrude, and pelletize to obtain an antibacterial and anti-aging polypropylene material.

[0023] Example 2

[0024] (1) Add 20 g of N,N-dimethyl-1-(naphthalen-1-yl)methanamine and 15.6 g of epichlorohydrin to 40 mL of isopropanol, heat to 70 °C, react for 7 h, perform vacuum distillation, and recrystallize the product in an ethanol aqueous solution with a volume fraction of 70% to obtain 2-(epoxypropyl)(naphthylmethyl)dimethyl quaternary ammonium salt.

[0025] (2) Add 10 g of chitosan to 35 mL of a 30% sodium hydroxide solution by mass fraction, stir and then add isopropanol, heat to 80 °C, then add 45 g of 2-(epoxypropyl)(naphthylmethyl)dimethyl quaternary ammonium salt, stir and react for 18 h, add 37% hydrochloric acid by mass fraction dropwise to the solution, control the pH of the solution to be 6.5, filter, wash with ethanol, and dry to obtain quaternary ammonium salt of chitosan.

[0026] (3) Add 150 mL of water, sodium p-styrenesulfonate, and benzophenone to 300 mL of ethanol, stir to prepare a grafting solution. Control the mass concentration of sodium p-styrenesulfonate in the grafting solution to be 200 g / L and the mass concentration of benzophenone to be 0.25 g / L. Then add the polypropylene film and irradiate it for grafting under a UV lamp with a power of 600 W in a nitrogen atmosphere for 30 min. Take out the polypropylene film, wash it with water and ethanol, and dry it to obtain sodium p-styrenesulfonate-grafted polypropylene.

[0027] (4) Add 1 kg of polypropylene, 25 g of quaternary ammonium salt of chitosan, 12 g of sodium p-styrenesulfonate-grafted polypropylene, and 4 g of antioxidant 1076 to a mixer and mix them. Then, in a twin-screw extruder, the temperatures of zones 1 - 6 are 160 °C, 170 °C, 185 °C, 195 °C, 195 °C, and 190 °C, the screw speed is 200 r / min, extrude, and pelletize to obtain an antibacterial and anti-aging polypropylene material.

[0028] Example 3

[0029] (1) Add 10 g of chitosan to 30 mL of a 40% sodium hydroxide solution by mass. After stirring, add isopropanol, heat to 85 °C, then add 60 g of 2-(naphthalenemethyl)dimethylglycidyl ammonium salt (prepared in the same way as in Example 1), stir and react for 18 h. Dropwise add 37% hydrochloric acid by mass to the solution, control the pH of the solution to 7, filter, wash with ethanol, and dry to obtain chitosan quaternary ammonium salt.

[0030] (2) Add 100 mL of water, sodium p-styrenesulfonate, and benzophenone to 300 mL of ethanol, stir to prepare a grafting solution, control the mass concentration of sodium p-styrenesulfonate in the grafting solution to 300 g / L and the mass concentration of benzophenone to 0.4 g / L. Then add a polypropylene film, and irradiate and graft for 30 min under an ultraviolet lamp with a power of 600 W in a nitrogen atmosphere. Take out the polypropylene film, wash with water and ethanol, and dry to obtain sodium p-styrenesulfonate-grafted polypropylene.

[0031] (3) Add 1 kg of polypropylene, 40 g of chitosan quaternary ammonium salt, 20 g of sodium p-styrenesulfonate-grafted polypropylene, and 7 g of antioxidant 1076 to a mixer and mix. Then, in a twin-screw extruder, the temperatures of zones 1 - 6 are 160 °C, 170 °C, 185 °C, 195 °C, 195 °C, and 190 °C, the screw speed is 200 r / min, extrude, and pelletize to obtain an antibacterial and anti-aging polypropylene material.

[0032] Comparative Example 1. The difference between this comparative example and Example 1 is that no chitosan quaternary ammonium salt and sodium p-styrenesulfonate-grafted polypropylene are added.

[0033] (1) Add 1 kg of polypropylene and 6 g of antioxidant 1076 to a mixer and mix. Then, in a twin-screw extruder, the temperatures of zones 1 - 6 are 160 °C, 170 °C, 185 °C, 195 °C, 195 °C, and 190 °C, the screw speed is 300 r / min, extrude, and pelletize to obtain a polypropylene material.

[0034] Comparative Example 2. The difference between this comparative example and Example 1 is that no chitosan quaternary ammonium salt is added.

[0035] (2) Add 1 kg of polypropylene, 6 g of sodium p-styrenesulfonate-grafted polypropylene, and 6 g of antioxidant 1076 to a mixer and mix. Then, in a twin-screw extruder, the temperatures of zones 1 - 6 are 160 °C, 170 °C, 185 °C, 195 °C, 195 °C, and 190 °C, the screw speed is 300 r / min, extrude, and pelletize to obtain a polypropylene material.

[0036] Comparative Example 3. The difference between this comparative example and Example 1 is that sodium styrene sulfonate grafted polypropylene is not added.

[0037] (1) Add 1 kg of polypropylene, 15 g of chitosan quaternary ammonium salt, and 6 g of antioxidant 1076 to a mixer for mixing. Then, in a twin-screw extruder, the temperatures of zones 1-6 are 160 °C, 170 °C, 185 °C, 195 °C, 195 °C, and 190 °C, the screw speed is 300 r / min, extrude and pelletize to obtain a polypropylene material.

[0038] Comparative Example 4. The difference between this comparative example and Example 1 is that chitosan is used instead of chitosan quaternary ammonium salt.

[0039] (1) Add 1 kg of polypropylene, 15 g of chitosan, 6 g of sodium styrene sulfonate grafted polypropylene, and 6 g of antioxidant 1076 to a mixer for mixing. Then, in a twin-screw extruder, the temperatures of zones 1-6 are 160 °C, 170 °C, 185 °C, 195 °C, 195 °C, and 190 °C, the screw speed is 300 r / min, extrude and pelletize to obtain a polypropylene material.

[0040] Comparative Example 5. The difference between this comparative example and Example 1 is that when preparing chitosan quaternary ammonium salt, 2,3-epoxypropyltrimethylammonium chloride is used instead of 2-(naphthalenemethyl)glycidyldimethylammonium salt.

[0041] (1) Add 10 g of chitosan to 25 mL of a 40% sodium hydroxide solution by mass fraction. After stirring, add isopropanol, heat to 90 °C, then add 30 g of 2,3-epoxypropyltrimethylammonium chloride, stir and react for 12 h. Dropwise add 37% hydrochloric acid by mass fraction to the solution, control the pH of the solution to 7, filter, wash with ethanol, and dry to obtain chitosan quaternary ammonium salt.

[0042] (2) Add 1 kg of polypropylene, 15 g of chitosan quaternary ammonium salt, 6 g of sodium styrene sulfonate grafted polypropylene, and 6 g of antioxidant 1076 to a mixer for mixing. Then, in a twin-screw extruder, the temperatures of zones 1-6 are 160 °C, 170 °C, 185 °C, 195 °C, 195 °C, and 190 °C, the screw speed is 300 r / min, extrude and pelletize to obtain a polypropylene material.

[0043] Respectively, the polypropylene materials prepared in Examples 1-3 and Comparative Examples 1-6 are injection molded by an injection molding machine at a temperature of 200 °C to make test specimens.

[0044] According to the film coating method of the QB / T 2591-2003 standard, test the antibacterial properties of the polypropylene materials, using the polypropylene material of Comparative Example 1 as a blank control sample. Examples 1-3 and Comparative Examples 2-5 are used as antibacterial plastic samples respectively.

[0045] Table 1

[0046]

[0047] As can be seen from the above table, chitosan quaternary ammonium salt and sodium styrene sulfonate-grafted polypropylene are added to the polypropylene materials in Examples 1-3. The polypropylene is grafted with sulfonate groups, which have electrostatic interaction with chitosan quaternary ammonium salt, thereby modifying the polypropylene molecular chain on the surface of chitosan quaternary ammonium salt. Making sodium styrene sulfonate-grafted polypropylene as a compatibilizer, the compatibility between chitosan quaternary ammonium salt and polypropylene material is improved. Chitosan quaternary ammonium salt is evenly dispersed in the polypropylene material matrix, with more antibacterial active sites, significantly improving the antibacterial performance of the material, showing high bactericidal performance against the antibacterial rate of Escherichia coli and Staphylococcus aureus.

[0048] In Comparative Example 2, chitosan quaternary ammonium salt was not added, and the antibacterial performance of the polypropylene material was very poor.

[0049] In Comparative Example 3, chitosan quaternary ammonium salt was added, and the antibacterial performance was significantly improved. However, the antibacterial rate of Escherichia coli and Staphylococcus aureus was lower than that in Example 1. Since sodium styrene sulfonate-grafted polypropylene was not added, the compatibility between chitosan quaternary ammonium salt and polypropylene was poor, and the dispersion in the material matrix was not good, with fewer antibacterial active sites than in Example 1, resulting in a slightly lower antibacterial rate.

[0050] In Comparative Example 4, chitosan was used instead of chitosan quaternary ammonium salt, which does not contain quaternary ammonium salt groups, resulting in an antibacterial rate lower than that in Example 1.

[0051] The chitosan quaternary ammonium salt prepared in Comparative Example 5 also significantly improved the antibacterial rate and antibacterial performance of the polypropylene material.

[0052] According to the standard of GB / T 1040.1-2006, the tensile strength of the test specimen was measured. The specimen was placed in a forced-air drying oven and heat-aged at 80 °C for 168 h, then placed at room temperature for 24 h, and then the tensile strength was measured.

[0053] The specimen was molded into a film shape, and the water contact angle was measured according to the standard of GB / T 30693-2014.

[0054] Table 2

[0055]

[0056]

[0057] The polypropylene materials of Examples 1-3 were added with sodium styrene sulfonate grafted polypropylene, which acted as a compatibilizer, improved the compatibility between chitosan quaternary ammonium salt and polypropylene, reduced the adverse effect of chitosan quaternary ammonium salt on the mechanical properties of polypropylene, and enabled the polypropylene materials to still have a very high tensile strength. Moreover, the chitosan quaternary ammonium salt contains a heat-resistant naphthalene ring structure, and adding it to the polypropylene material is beneficial to improving the heat resistance performance. After heat aging treatment, the polypropylene materials can maintain good tensile strength and exhibit excellent heat aging resistance. In addition, the added sodium styrene sulfonate grafted polypropylene contains a sulfonate hydrophilic group and the hydrophilic chitosan quaternary ammonium salt, which can reduce the water contact angle of the polypropylene material and improve the surface hydrophilicity and skin-friendly property.

[0058] Compared with Comparative Example 1, after heat aging treatment, the polypropylene materials of Comparative Examples 1-2 had a relatively large decrease in tensile strength. In Comparative Example 3, sodium styrene sulfonate grafted polypropylene was not added, and the compatibility between chitosan quaternary ammonium salt and the polypropylene material was poor, resulting in a low tensile strength of the material. In Comparative Example 4, chitosan was added, which does not contain a quaternary ammonium salt group and cannot undergo electrostatic interaction with sodium styrene sulfonate grafted polypropylene, thus unable to act as a compatibilizer, and the compatibility between chitosan and the polypropylene material was poor, resulting in a low tensile strength of the polypropylene material. The chitosan quaternary ammonium salt in Comparative Example 5 does not contain a heat-resistant naphthalene ring structure and does not improve the heat resistance of the polypropylene material. After heat aging treatment, the tensile strength retention rate of the material was low.

[0059] Although the present invention is disclosed as above, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention should be subject to the scope defined by the claims.

Claims

1. An antibacterial and anti-aging polypropylene material, characterized in that: In parts by weight, the antibacterial and anti-aging polypropylene material comprises 100 parts of polypropylene, 1.5-4 parts of chitosan quaternary ammonium salt, 0.6-2 parts of sodium styrene sulfonate grafted polypropylene, and 0.4-0.7 parts of antioxidant; The preparation method of the chitosan quaternary ammonium salt is as follows: adding chitosan to a sodium hydroxide solution, adding isopropanol after stirring, heating to a reaction temperature, then adding 2-epoxypropyl (naphthylmethyl) dimethyl quaternary ammonium salt, stirring for reaction, dripping hydrochloric acid into the solution, filtering, washing, and drying to obtain the chitosan quaternary ammonium salt.

2. The antibacterial and anti-aging polypropylene material according to claim 1, characterized in that: The mass fraction of the sodium hydroxide solution is 30-40%.

3. The antibacterial and anti-aging polypropylene material according to claim 1, characterized in that: In parts by weight, the amount of chitosan is 100 parts, and the amount of 2-epoxypropyl (naphthylmethyl) dimethyl quaternary ammonium salt is 300-600 parts.

4. The antibacterial and anti-aging polypropylene material according to claim 1, characterized in that: The reaction temperature is 80-90°C and the reaction time is 12-18h.

5. The antibacterial and anti-aging polypropylene material according to claim 1, characterized in that: The pH of the solution is controlled to be 6.5-7 by adding hydrochloric acid.

6. The antibacterial and anti-aging polypropylene material according to claim 1, characterized in that: The preparation method of the 2-epoxypropyl (naphthylmethyl) dimethyl quaternary ammonium salt is as follows: N,N-dimethyl-1-(naphthyl-1-yl)methylamine and epichlorohydrin are added to isopropanol, heated to 70-80° C., reacted for 4-7 hours, distilled under reduced pressure, and recrystallized to obtain 2-epoxypropyl (naphthylmethyl) dimethyl quaternary ammonium salt.

7. The antibacterial and anti-aging polypropylene material according to claim 6, characterized in that: In parts by weight, the amount of N,N-dimethyl-1-(naphthalene-1-yl)methylamine used is 100 parts, and the amount of epichlorohydrin used is 59-78 parts.

8. The antibacterial and anti-aging polypropylene material according to claim 1, characterized in that: The preparation method of the sodium styrene sulfonate grafted polypropylene is as follows: water, sodium p-styrene sulfonate and benzophenone are added to ethanol, stirred to prepare a grafting solution, then a polypropylene film is added, irradiated and grafted for 15-30 minutes under an ultraviolet lamp in a nitrogen atmosphere, the polypropylene film is taken out, washed and dried to obtain the sodium styrene sulfonate grafted polypropylene.

9. The antibacterial and anti-aging polypropylene material according to claim 8, characterized in that: The mass concentration of sodium p-styrene sulfonate in the grafting solution is 80-300 g / L, and the mass concentration of benzophenone is 0.06-0.4 g / L.

10. A method for preparing the antibacterial and anti-aging polypropylene material according to any one of claims 1 to 9, characterized in that: The preparation method comprises the following steps: adding polypropylene, chitosan quaternary ammonium salt, sodium styrene sulfonate grafted polypropylene and an antioxidant into a mixer for mixing; then extruding and granulating in a twin-screw extruder at a temperature of 160-195° C. in zones 1-6 and a screw speed of 200-300 r / min to obtain an antibacterial and anti-aging polypropylene material.

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