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织物改性处理对涤纶织物/PVC复合材料吸水性能及 热性能的影响

2022-03-19普丹丹周涵普庆

丝绸 2022年3期
关键词:复合材料

普丹丹 周涵 普庆

摘要:为探究改性处理对涤纶织物/PVC复合材料吸水性能及热性能的影响,文章分别采用碱处理、碱溶液与上浆剂联合处理的方法对涤纶织物进行改性处理,利用接触成型技术制备涤纶织物/PVC复合材料。采用扫描电镜对涤纶织物/PVC复合材料的断面形貌进行观察,对复合材料的吸水质量分数和热稳定性进行测试分析。研究发现,织物改性处理降低了涤纶织物/PVC复合材料的吸水性能,随着浸泡时间的延长,未改性处理、碱处理、碱溶液与上浆剂联合处理涤纶织物/PVC复合材料的吸水质量分数依次降低;改性处理对涤纶织物/PVC复合材料的热稳定性无显著 影响。

关键词:  涤纶织物;改性处理;复合材料;吸水性能;热性能

中图分类号: TS101.923;TQ342.2

文献标志码: A

文章编号: 1001 7003(2022)03 0028 05

引用页码: 031104

DOI: 10.3969/j.issn.1001-7003.2022.03.004 (篇序)

涤纶织物/聚氯乙烯(PVC)柔性复合材料具有质量轻、强度高、可加工性能好等优点  [1-3] ,广泛应用于体育建筑、商场、交通服务设施等大跨度建筑中。但由于涤纶织物/PVC柔性复合材料在实际应用中存在易吸水和热稳定性差等缺点,导致材料易发霉,抗疲劳性能差,从而影响其使用寿命,并在一定程度上限制其应用。因此,研究涤纶织物/PVC柔性复合材料的吸水性能和热性能十分有必要。

在包括涤纶织物/PVC复合材料在内的层合复合材料的制备过程中,改善增强体与基体材料之间的界面结合是最关键的技术之一。目前最常用的方法是加入异氰酸酯类黏合剂以提高复合材料的界面黏结性能  [4-5] 。然而,异氰酸酯是极其有害的  [6] ,它不仅在生产过程中对工人的健康造成危害,还会在使用过程中释放出甲醛等有害物质。近年来,对涤纶织物进行表面改性,改善涤纶与基体材料之间的界面结合受到了众多科研工作者的廣泛关注  [7-9] 。为此,本文采用碱处理、碱溶液与上浆剂联合处理的方法对涤纶织物进行改性处理,利用接触成型技术制备涤纶织物/PVC复合材料,研究碱处理、碱溶液与上浆剂联合处理对涤纶织物/PVC复合材料吸水性能及热性能的影响。

1 实 验

1.1 材料及设备

平纹组织的涤纶织物,其经、纬丝线规格均为55.56 tex/96 f,经、纬向密度均为120根/10 cm(浙江金汇特材料有限公司),EPVC聚氯乙糊烯树脂,牌号为P450,聚合度为1 000±150(上海氯碱化工股份有限公司),氢氧化钠(分析纯,杭州高晶精细化工有限公司),表面活性剂1227(工业级,杭州科峰化工有限公司),抗静电剂SN(工业级,江苏省安海石油化工厂), 柠檬酸三丁酯(TBC,98 % )、环氧大豆油(ESO,化学纯)(阿拉丁试剂有限公司),SiO 2/TBC上浆剂(实验室自制)。

AL204分析天平(梅特勒托利多仪器(上海)有限公司),KQ-400KDE超声波清洗器(昆山市超声仪器有限公司),DHG-9146A鼓风干燥箱(上海精宏实验设备有限公司),CH1015超级恒温槽(上海衡平仪器仪表厂),JJ-6B数显恒速电动搅拌器(常州市金坛联友仪器有限公司),ULTRA55型场发射电子显微镜(FE-SEM,德国ZEISS公司),Labsys Evo型热重差热分析仪(法国塞塔拉姆公司)。

1.2 方 法

1.2.1 涤纶织物的表面改性

涤纶织物表面处理的方法如表1所示。

1.2.2 涤纶织物/PVC复合材料的制备

采用接触成型工艺制备涤纶织物/PVC复合材料。工艺流程如图1所示,具体步骤为:

1) 先将EPVC、TBC和ESO按照质量比100 ︰ 130 ︰ 7混合,以1 000 r/min的速度搅拌30 min,然后在真空干燥箱中进行脱泡,制备均匀的树脂糊混合物。

2) 分别将PF、PF-1、PF-2织物裁成20 cm×20 cm大小平放在聚四氟乙烯平板上,然后将制备的树脂糊混合物浇注在涤纶织物上面,通过手动辊缓慢地滚动以确保涤纶织物完全被浸润,并且挤出多余的树脂糊。

3) 将复合材料置于165 ℃的烘箱中烘燥6 min,冷却后反复进行手糊工艺,保证所有复合材料试样的厚度在0.85~0.88 mm。

1.3 测试与表征

1.3.1 复合材料断面形貌观察

利用ULTRA55型场发射电子显微镜(FE-SEM)对涤纶织物/PVC树脂复合材料的断面形貌进行观察,镀金25 s,测试电压10 kV。

1.3.2 吸水性能测试

按照GB/T 1034—2008《塑料吸水性的测定》(23 ℃水中吸水量的测定)方法。将复合材料试样放入(50.0±2.0) ℃烘箱内干燥至少24 h,然后在干燥器内冷却至室温,称量每个样品,精确至0.1 mg。 然后将试样放入盛有蒸馏水的容器中,水温控制在(23.0±1.0) ℃。分别浸泡(24±1) h、(48±1) h、(72±1) h后,每隔48 h取出一次试样,用清洁干布或滤纸迅速擦去试样表面所有的水,再次称量每个试样,精确至0.1 mg。 试样从水中取出后,在1 min内完成称量。

根据下式计算每个试样相对于初始质量的吸水质量分数,实验结果以相同条件下得到的三个结果的算术平均值 表示。

c i/ % = m i-m 0 m 0 ×100   (1)

式中: c i 为试样的吸水质量分数, % ; m i 为浸泡后是试样的质量,mg; m 0 为浸泡前干燥后试样的质量,mg。

1.3.3 TG分析

热失重(TG)分析是在程序升温的环境中,测试试样的质量对温度的依赖关系的一种技术,用于分析复合材料的热稳定性。采用Labsys Evo型热重差热分析仪测试涤纶织物/PVC复合材料的热稳定性。测试前,需要把样品切成均匀的小颗粒。设定测试温度为室温至750 ℃,升温速率为10 ℃/min,在氮气保护下进行测试。

2 结果与分析

2.1 复合材料断面形貌

本文采用FE-SEM对涤纶织物/PVC树脂复合材料断裂面的形貌进行观察,结果如图2所示。图2(a)为PF织物/PVC复合材料的断裂面,可以看出在复合材料断裂过程中,织物被完全拔出基体,在基体表面留下清晰的凹痕,织物与基体产生明显的脱黏现象,说明织物与基体之间的结合不好。图2(b)为PF-1织物/PVC复合材料的断裂面,可以看到断裂的织物残留在基体中,在复合材料的断裂面上织物与基体分离,这说明经过碱处理,织物表面粗糙度变大,增大了织物与基体的接触面积,在一定程度上提高了复合材料的界面黏结强度。图2(c)为PF-2织物/PVC复合材料的断裂面,可以看出在复合材料的断裂面,织物与基体的结合是令人满意的。这是由于上浆处理改善了涤纶织物与PVC基体的浸润性,增大了基体浸润纤维的表面积,同时也增加了涤纶织物表面与PVC基体之间的相互作用点,增强了涤纶织物与PVC基体之间的机械锁合。上浆剂膜层类似于一个“桥梁”,牢固地连接着基体和织物  [10] 。因此,复合材料的界面黏结得到改善。

2.2 吸水性能

复合材料的吸水性不仅与复合材料中基体、增强体材料的吸水性有关,还与复合材料的界面黏结情况密切相关。涤纶织物/PVC复合材料中,增强材料涤纶织物与基体材料PVC的吸水性能均很差,水分主要通过涤纶织物与PVC基体的界面孔隙的芯吸作用进入到复合材料内部。因此,复合材料的吸水率可以间接表征其界面黏结情况。

本文对相同规格的三种涤纶织物/PVC复合材料的吸水质量分数进行测试,结果如图3所示。

从图3可以看出,三种涤纶织物/PVC复合材料的吸水质量分数均随浸泡时间的延长而升高,表明复合材料具有一定的吸湿能力。从整体来看,在浸泡初期,复合材料吸水的速率较快,随着浸泡时间的延长,复合材料吸水的速率渐渐变慢。可以把复合材料的吸湿过程分为两个阶段: 第一阶段的吸湿主要发生在复合材料的表面,水分沿着材料表面的微孔渗入到复合材料内部;第二阶段的吸湿主要发生在复合材料的界面,水分通过复合材料界面处的毛细作用进入到复合材料的内部  [11] 。由于三种涤纶织物/PVC复合材料试样的表面结构基本一样,故在浸泡初期三种复合材料的吸湿规律大致相同。随着浸泡时间的延长,复合材料的吸湿通过复合材料界面处的毛细作用,三种复合材料的吸湿规律出现了明显的差异,这足以说明三种复合材料的界面结构差异较大。从图3还可以看出,PF织物/PVC复合材料、PF-1织物/PVC复合材料、PF-2织物/PVC复合材料的吸水质量分数依次降低,表明它们的界面结合依次紧密。这与上文复合材料断裂面形貌照片的结果吻合。

2.3 热稳定性

热失重法是测定聚合物热稳定性常用的方法之一,其除了可以用來分析材料的热稳定性和热分解过程之外,还可以用来测定材料中的组分及水分挥发物等。本文采用Labsys Evo型热重差热分析仪测试涤纶织物/PVC复合材料的热重曲线,结果如图4所示。

从图4可以看出,三种涤纶织物/PVC复合材料的TG曲线在25~200 ℃平稳中略有降低,主要是由于复合材料中水分的挥发。TG曲线在200 ℃左右迅速下降,表明复合材料从200 ℃左右开始分解。在200~350 ℃分解速率最快,至 350 ℃时 失重约为70 % 多,趋于平稳;当温度升至420 ℃左右时又逐渐分解,直至500 ℃曲线平稳。以上结果表明,织物改性处理对涤纶织物/PVC复合材料的热稳定性没有显著影响。

3 结 论

通过对涤纶织物进行表面改性,利用接触成型技术制备涤纶织物/PVC复合材料。先对涤纶织物/PVC复合材料的断面形貌进行观察,后对复合材料的吸水性能和热稳定性进行测试分析,得到如下结论:

1) 织物改性处理使涤纶织物/PVC复合材料的界面黏结得到改善。

2) 随着浸泡时间的延长,未改性处理涤纶织物/PVC复合材料、碱处理涤纶织物/PVC复合材料、碱溶液与上浆剂联合处理织物/PVC复合材料的吸水质量分数依次降低,表明织物改性处理降低了涤纶织物/PVC复合材料的吸水性能。

3) 三种涤纶织物/PVC复合材料的TG曲线的规律基本一致,表明织物改性处理对涤纶织物/PVC复合材料的热稳定性没有显著影响。

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Influences of fabric modification treatment on water absorption and thermal properties of polyester fabric/PVC composites

PU Dandan 1, ZHOU Han 1, PU Qing 2

(1.School of Textiles, Henan University of Engineering, Zhengzhou 450007, China; 2.Electrical Inspection Center, Henan Institute of Product Quality Supervision and Inspection, Zhengzhou 450004, China)

Abstract:

With the development of polyester industrial technology, the mechanical properties of polyester industrial yarn such as strength and modulus have been continuously improved. The application field of composites reinforced with polyester fiber (fabric) has also been expanding because of its advantages such as lightweight, flexibility and good weavability. Among them, polyester fiber (fabric) reinforced polyvinyl chloride (PVC) flexible composites have been widely used in long-span buildings such as sports buildings, shopping malls, transportation service facilities and so on due to the high strength and modulus, good dimensional stability, strong bearing capacity and excellent fatigue resistance. However, polyester, characterized by smooth surface, lack of polar groups and chemical inertia on the surface, is difficult to excellently bond with PVC matrix, resulting in poor interfacial bonding strength of PVC matrix composites. As a result, polyester fabric/PVC flexible composites have disadvantages such as high water absorption and poor thermal stability in practical application, resulting in proness to going mouldy and poor fatigue resistance of materials. This affects the service life and limits the application to a certain extent. Therefore, it is necessary to study the interface bonding properties of polyester fabric/PVC flexible composites under modified treatment and their relationship with water absorption and thermal properties.

In order to investigate the influence of fabric modification treatment on the water absorption and thermal properties of polyester fabric/PVC composites, the polyester fabric was modified by alkali treatment, alkali solution and sizing agent combined treatment, and the polyester fabric/PVC composites were prepared by contact molding technology. Scanning electron microscopy (SEM) was used to observe the section morphology of polyester fabric/PVC composites, and the water absorption fraction and thermal stability of the composites were tested and analyzed. Based on the above, this paper adopted the method of correspondence analysis to investigate the relationship between water absorption and interfacial bond of polyester fabric/PVC composites. It is found that with the increase in surface roughness of alkali treated polyester fabric, the contact area between fabric and matrix is increased, and the interfacial adhesion of composites is improved to a certain extent. Sizing treatment improves the wettability between polyester fabric and PVC matrix, increases the interaction point between polyester fabric surface and PVC matrix, and strengthenes the mechanical locking between polyester fabric and PVC matrix. Therefore, the interface bonding of the composites is improved. Fabric modification reduces the water absorption of polyester fabric/PVC composites, and with the extension of soaking time, the moisture absorption of composites is realized mainly through the capillary action at the interface of composites. There are obvious differences in the moisture absorption laws of unmodified polyester fabric/PVC composites, alkali treated polyester fabric/PVC composites, alkali solution and sizing agent jointly treated fabric/PVC composites, indicating a great difference in the interfacial structures of the three composites. The water absorption mass fraction of unmodified polyester fabric/PVC composites, alkali treated polyester fabric/PVC composites, alkali solution and sizing agent jointly treated fabric/PVC composites decrease successively, indicating their close interface bonding in sequence. Fabric modification has no significant effect on the thermal stability of polyester fabric/PVC composites.

The relationship between water absorption and interfacial bond of polyester fabric/PVC composites can bring inspiration for characterization of structural composites. The worse the water absorption property of structural composite, the better the interface bonding property. The results of this research can provide reference for the characterization of structural composites in the future.

Key words:

polyester fabric; modification treatment; composites; water absorption property; thermal property

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