CN107877957B - 一种柔性充气防热罩及其制备方法 - Google Patents

一种柔性充气防热罩及其制备方法 Download PDF

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CN107877957B
CN107877957B CN201610865932.1A CN201610865932A CN107877957B CN 107877957 B CN107877957 B CN 107877957B CN 201610865932 A CN201610865932 A CN 201610865932A CN 107877957 B CN107877957 B CN 107877957B
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柯红军
夏雨
王国勇
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Aerospace Research Institute of Materials and Processing Technology
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Abstract

本发明提出一种柔性充气防热罩及其制备方法,由若干层柔性抗烧蚀层、若干层柔性抗辐射层和柔性耐高温气密层组成,柔性抗烧蚀层和柔性抗辐射层由外而内按S‑F‑S‑F‑…‑S‑F结构交替分布,其中S为柔性抗烧蚀层,F为柔性抗辐射层,柔性耐高温气密层位于最内侧,各柔性抗烧蚀层、柔性抗辐射层和柔性耐高温气密层之间用硅橡胶胶黏剂粘结。本发明在硅橡胶体系中添加适量酚醛树脂和纳米陶瓷粉体,使硅橡胶涂覆织物保持柔性的同时,在高温下陶瓷化,显著提高抗烧蚀性能,有效减少烧蚀层层数及厚度,有良好的折叠性能。

Description

一种柔性充气防热罩及其制备方法
技术领域
本发明涉及一种柔性充气防热罩及其制备方法,属于耐烧蚀复合材料技术领域。
背景技术
随着航空航天技术的快速发展,大尺寸、高吨位的再入飞行器的发展受到国内外的广泛关注,火箭、导弹、飞船等飞行器工作温度较高,一般在2000K以上,气动加热或动力火焰产生的热流、高温已超出材料所能承受的范围,必须进行有效的热防护,航天器的高效热防护技术逐渐成为制约其发展的关键技术瓶颈之一。传统的再入航天器气动构型及热防护结构大多采用固定式刚性结构,受运载火箭发射能力及整流罩包络约束,极大地限制了航天器气动构型尺寸、质量及弹道系数,从而大大降低了航天器载荷运输能力。因此,航天器的高效热防护技术越来越倾向于轻质、适形、装配简单、无应力匹配的方向发展。柔性防热材料因为其结构匹配性好、安装灵活、结构收纳比小,在火箭、导弹等飞行器上的应用十分广泛。
再入飞行器一般都采用充气式再入减速模式,即利用充气形成的气动外形提供了升力或阻力的航天回收系统,材料一般选用柔性防热结构。由柔性防热结构制成充气式防热罩,卷缩在舱体外围,在进入大气前充气,形成倒锥外形,保护舱体并有效地进行气动减速。柔性防热结构除了具备耐高温、满足烧蚀性能外,还要具有可折叠、透气性低、抗拉伸等特点。充气式再入飞行器能够在再入过程中的气动载荷使用下维持气动外形;防热罩能够折叠在较小的容积内;充气罩展开后,能经受飞行环境的作用;再入大气时,能够起到防热作用。
目前国内外充气式柔性防热结构普遍采用耐高温涂层+柔性隔热材料+气囊材料,与辐条连接,具备收纳和展开能力,高温涂层主要用来承受火焰烧蚀,隔热层主要用来管理总的热载荷,使柔性热防护系统的背面温度等于或小于充气结构的最高使用温度。气密层用来连接热防护系统和充气结构,使进入的热气不能进入充气结构内部。由于该结构采用的柔性隔热材料厚度较大,一般厚度在30~50mm才可以发挥好的作用,所以导致重量较大、厚度较厚、不易折叠存放。
发明内容
本发明的目的在于克服现有技术不足,提供了一种轻质、易折叠存放、能有效降低总体厚度的柔性充气防热罩及其制备方法。
本发明的技术解决方案:一种柔性充气防热罩,由若干层柔性抗烧蚀层、若干层柔性抗辐射层和柔性耐高温气密层组成,柔性抗烧蚀层和柔性抗辐射层由外而内按S-F-S-F-…-S-F结构交替分布,其中S为柔性抗烧蚀层,F为柔性抗辐射层,柔性耐高温气密层位于最内侧,各柔性抗烧蚀层、柔性抗辐射层和柔性耐高温气密层之间用硅橡胶胶黏剂粘结;
所述的柔性抗烧蚀层为酚醛树脂及纳米陶瓷粉体改性硅橡胶涂覆纤维织物,酚醛树脂及纳米陶瓷粉体改性硅橡胶中纳米陶瓷粉体的含量为0.5%~3%,酚醛树脂的含量为5%~30%,且由外到内各层中酚醛树脂含量逐层减小。
所述的柔性抗烧蚀层不少于3层,最外层酚醛树脂含量(酚醛树脂含量是指酚醛树脂占硅橡胶体系质量的百分比,硅橡胶体系质量为硅橡胶和硫化剂总量)为25~30%,最内层酚醛树脂含量为5~10%,相邻两层之间含量梯度差不少于2%。柔性抗烧蚀层的总厚度越高,其耐烧蚀性能就越好,但重量也越大,总厚度太高,会影响收纳及折叠性能;单层厚度越厚,单层耐烧蚀性能也好,但厚度太大容易导致表面形成龟裂纹,柔性也会下降。
所述的柔性抗烧蚀层中纳米陶瓷粉体含量(纳米陶瓷粉体含量是指纳米陶瓷粉体占硅橡胶体系质量的百分比,硅橡胶体系质量为硅橡胶和硫化剂总量)为0.5%~3%,每层所含的纳米陶瓷粉体含量可以相同或不同,含量不同时,纳米陶瓷粉体含量由外到内减少,即外层的纳米陶瓷粉体含量要高于内层纳米陶瓷粉体含量。纳米陶瓷粉体含量越高,有利于高温下与裂解挥发分发生反应,提高炭层的内聚强度,提高残炭率及陶瓷化比例,但会影响柔性抗烧蚀层的柔性,进而影响折叠性。
更优选:所述的纳米陶瓷粉体含量由外到内逐层递减,相邻两层递减不少于0.25%。
本发明纳米陶瓷粉体含量梯度设计与逐渐减小的热流值相匹配,进一步提高残炭率及炭层的结构稳定性。在高温状态下,酚醛进行烧蚀反应,发生炭化,在高温冲刷裂解过程中,炭骨架会形成孔洞、裂纹等微缺陷,抗烧蚀层由外到内,随着温度及冲刷力度逐渐递减,外层温度越高,高温裂解产生的孔洞、裂纹就越多,纳米陶瓷粉体含量高一些,有利于高温下与裂解挥发分发生反应,提高残炭率及陶瓷化比例,有利于修复孔洞及裂纹,提高炭层的内聚强度。随着温度向内传导及散热,次外层温度及冲刷力度减弱,裂解反应的剧烈程度降低,降低纳米陶瓷粉体比例一方面适应反应的需要,同时,纳米陶瓷粉体比例降低对韧性及可折叠性产生积极的影响。
在高热流密度及高温下,硅橡胶首先发生炭化,硅橡胶中Si-O键会转变成连续抗氧化、绝缘的网络状SiO2灰烬覆盖在表面,酚醛树脂裂解发生炭化形成无定形炭,随着温度的进一步升高,裂解成挥发分气体,纳米陶瓷粉体主要作用是高温下与裂解挥发分发生反应,生成无定炭,一方面提高了高温残炭率,进一步进行陶瓷化,同时反应过程中的中间产物在高温状态下熔融,体积发生膨胀,可在一定程度愈合、修补热解产生的收缩缺陷,进一步提高残炭率及炭层的结构稳定性。
本发明柔性抗烧蚀层采用的纳米陶瓷粉体为纳米炭化硼、纳米二氧化钛、纳米碳化硅、纳米碳化硼或纳米氧化锆的一种或几种,粒径为30~100纳米。
本发明通过对柔性抗烧蚀层进行梯度设计,靠近热流面酚醛树脂含量高,靠近阻隔层酚醛树脂含量低,最外层酚醛树脂含量高,材料抗烧蚀性能好,高温、高热流冲刷下,酚醛树脂发生裂解炭化成无定形碳,吸收一部分热量,随着热流进一步向内传导,内部的柔性抗烧蚀层又进行一次烧蚀吸热,同时酚醛含量逐层递减,柔性抗烧蚀层的断裂伸长率越高,便于折叠。
本发明在综合考虑耐烧蚀性能、厚度及折叠性能,优选柔性抗烧蚀层总厚度不低于4mm,不高于15mm,每层厚度为0.2~1.5mm;在此范围内,相同层数下,总厚度越高,烧蚀性能越好;总厚度相同,层数不同,由于柔性抗烧蚀层和柔性抗辐射层的协同作用,层数越多,烧蚀性能越好。本领域技术人员可以根据烧蚀性能要求来具体设计柔性抗烧蚀层的层数和厚度。
本发明采用的酚醛树脂没有特殊的种类限制,其耐温等级根据飞行器温度及速度确定,可以选择钡酚醛、硼酚醛、钼酚醛等中的一种或几种。本发明在硅橡胶体系中添加适量酚醛树脂和纳米陶瓷粉体,使硅橡胶涂覆织物保持柔性的同时,显著提高抗烧蚀性能,有效减少烧蚀层层数及厚度。
本发明柔性抗烧蚀层采用的改性硅橡胶体系为热硫化型硅橡胶,由于改性硅橡胶体系中添加了不同比例的酚醛树脂,因此,在选择改性硅橡胶的硅橡胶种类时在满足耐温等级要求的同时,保证改性硅橡胶体系的硫化温度不低于酚醛树脂的固化温度。一般可使用甲基硅橡胶、甲基乙烯基硅橡胶等。
硅橡胶硫化剂一般为有机过氧化物或铂络合物加成型催化剂,本领域技术人员根据硅橡胶的种类来选择硫化剂的种类和用量,此为本领域公知技术,在此就不一一赘述。
所述的柔性抗辐射层为金属薄膜,采用抗辐射性能的金属薄膜,如铝薄膜材料、钛薄膜材料等的一种或几种。金属薄膜越厚,其抗辐射性能越好,但重量越大。本发明综合考虑金属薄膜抗辐射性能、重量及折叠性能影响,确定其最佳厚度为0.02~0.1mm。
柔性抗辐射层主要能降低两层间材料的热传导,把热量向加热面辐射,减缓热量向内层传导的速度,同时热量达到柔性抗辐射层的熔化温度,辐射层熔化带走大量的热量。本发明在相邻柔性抗烧蚀层之间都设置了柔性抗辐射层,在柔性抗辐射层与柔性抗烧蚀层协同作用下,能有效增加抗烧蚀能力,提高热防护效率。
本发明柔性耐高温气密层为硅橡胶涂覆纤维织物;主要作用为在充气罩气动减速过程中,充入一定压强的气体,起到良好的气密作用,保证整个充气罩气动外形的稳定性。为保证其具有良好的充气延展性及气密性,柔性耐高温气密层层数一般为1~3层即可满足要求,每层最佳厚度为0.2~1mm(单层厚度太大容易导致表面形成龟裂纹,柔性也会下降,影响气密性)。硅橡胶涂覆纤维织物具有耐热性能优良、热导率小、密度低、阻隔气密性好,且加工工艺简单,采用纤维涂覆机上涂覆硅橡胶胶层即可得到。
本发明采用的纤维织物为本领域常用的耐烧蚀纤维种类,根据发动机燃气温度确定纤维种类,可以为玻璃纤维织物、高硅氧织物、芳纶纤维织物等中一种或几种。
本发明在飞行器再入时,防热罩充入一定压强的气体,形成一定的气动外形,防热罩在高速度及高热燃气流冲刷时,外层为抗烧蚀层,主要起到烧蚀作用,通过在热流作用下,硅橡胶、酚醛树脂、纳米陶瓷粉体及织物发生分解、熔化、氧化、炭化等多种吸热的物理化学变化,带走大量的热,在高温状态下表面发生陶瓷化反应,形成坚硬的外壳,表面微烧蚀,从而阻止热流传递到材料内部,柔性抗辐射层主要作用是辐射防热,辐射防热是将热量辐射出去,阻止热量向内部进一步扩展,柔性耐高温气密层主要作用为充入一定压强的气体,形成一定的气动外形,阻隔热流向内部渗透,起到良好的气密作用,同时三部分可以根据热流密度及时间进行合理设计,发挥协同作用。
一种柔性充气防热罩的制备方法,通过以下步骤实现:
第一步,制备酚醛树脂及纳米陶瓷粉体改性硅橡胶树脂体系,
A1.1、将硅橡胶和硫化剂共混,在搅拌机中搅拌均匀,得到硅橡胶体系;
A1.2、将一定量的酚醛树脂和纳米陶瓷粉体分别加入到步骤A1.1得到的硅橡胶体系中,搅拌均匀,得到不同酚醛树脂及纳米陶瓷粉体含量的酚醛树脂改性硅橡胶树脂体系;
第二步,用步骤A1.1得到的硅橡胶体系和步骤A1.2得到不同酚醛树脂及纳米陶瓷粉体含量的酚醛树脂改性硅橡胶树脂体系分别双面涂敷纤维织物,硫化后得到硅橡胶涂敷纤维织物和不同酚醛树脂及纳米陶瓷粉体含量的改性硅橡胶涂敷纤维织物;
硫化工艺根据采用的热硫化型硅橡胶种类而定,由于酚醛树脂改性硅橡胶中添加了不同比例的酚醛树脂,因此,在选择酚醛树脂改性硅橡胶的硅橡胶种类时要保证硅橡胶的硫化温度不低于酚醛树脂的固化温度。
硅橡胶(含有不同酚醛树脂及纳米陶瓷粉体含量的硅橡胶涂敷工艺与硅橡胶涂敷工艺一致)涂敷纤维织物为本领域公知技术,采用纤维涂敷机,以纤维织物为载体在其两面涂敷橡胶,涂覆完进行硫化,其工艺控制为本领域公知技术,本领域技术人员根据选择的硅橡胶种类及硫化剂种类/添加量进行确定,在此就不一一赘述。
第三步,将第二步得到的不同酚醛树脂及纳米陶瓷粉体含量的改性硅橡胶涂敷纤维织物S与金属薄膜F进行交替铺设,得到S-F-S-F-…-S-F结构,从外而内,改性硅橡胶涂敷纤维织物的酚醛含量依次递减;
所述的改性硅橡胶涂敷纤维织物不少于3层,最外层酚醛树脂含量(是指酚醛树脂占硅橡胶体系质量的百分比,硅橡胶体系质量为硅橡胶和硫化剂总量)为25~30%,最内层酚醛树脂含量为5~10%,相邻两层之间含量梯度差不少于2%,所述的纳米陶瓷粉体的质量为硅橡胶体系质量的0.5%~3%;
第四步,在最内层的金属薄膜内铺设若干层硅橡胶涂敷纤维织物;
第五层,将所有的改性硅橡胶涂敷纤维织物、金属薄膜和硅橡胶涂敷纤维织物使用硅橡胶胶黏剂粘接硫化后,得到柔性充气防热罩。
本发明与现有技术相比的有益效果:
(1)本发明通过一定含量的酚醛树脂改性硅橡胶制备硅橡胶涂覆纤维织物,首先硅橡胶具有独特的化学稳定性,耐高低温性、耐侯性,燃烧热值低,火焰传播速度较慢,在高温热流状态下,Si-O键会转变成连续抗氧化、绝缘的网络状SiO2灰烬覆盖在表面,有效阻止烧蚀,同时在硅橡胶体系中添加适量酚醛树脂和纳米陶瓷粉体,使硅橡胶涂覆织物保持柔性的同时,在高温下陶瓷化,显著提高抗烧蚀性能,有效减少烧蚀层层数及厚度,有良好的折叠性能;
(2)本发明可以根据热流大小及时间,进行柔性烧蚀层的梯度设计,即靠近热流面酚醛树脂含量高,靠近阻隔层酚醛树脂含量低,酚醛树脂含量高,材料抗烧蚀性能好,高温、高热流冲刷下,酚醛树脂发生裂解炭化成无定形碳,吸收一部分热量,随着热流进一步向内传导,内部的柔性抗烧蚀层又进行一次烧蚀吸热,同时酚醛含量越小,涂覆织物的断裂伸长率越高,其柔性越好;
(3)本发明抗烧蚀层采用酚醛树脂及纳米陶瓷粉体含量双梯度设计,即酚醛树脂和纳米陶瓷粉体含量由外到内梯度设计,逐渐减少,在靠近燃气流外表面,随着温度的升高,硅橡胶发生炭化反应,形成灰烬,酚醛树脂的加入提高了高温残炭率,但是生成的炭为无定形炭,在燃气流冲刷下,不容易形成致密的炭层网络,纳米陶瓷粉体主要作用是高温下与裂解挥发分发生反应,反应过程中的中间产物在高温状态下熔融,体积发生膨胀,进一步进行陶瓷化,可在一定程度愈合、修补热解产生的收缩缺陷,纳米陶瓷粉体含量梯度设计与逐渐减小的热流值相匹配,进一步提高残炭率及炭层的结构稳定性,陶瓷化反应使疏松无定形炭层更加致密化,陶瓷保护层起到阻碍对流和热量传导的作用,在抑制材料热分解的同时,能有效阻碍外界热量向材料内部扩散;
(4)本发明外层采用柔性抗烧蚀层和柔性抗辐射层交替布置,充分发挥两者之间的协同作用,辐射层主要能降低材料间的热传导,把热量向加热面辐射,减缓热量向阻隔层传导的速度,同时热量达到辐射层的熔化温度,辐射层熔化带走大量的热量,柔性抗烧蚀层采用酚醛树脂改性硅橡胶体系,进一步提高了其抗烧蚀性能;
(5)本发明基于柔性功能层的梯度设计,可以使防热罩设计更加灵活,各功能层更好的发挥各自作用,实现协同吸热,同时能大大提高整体抗烧蚀性能、气密阻隔性能及可靠性。
附图说明
图1为本发明结构示意图。
具体实施方式
本发明如图1所示,由若干层柔性抗烧蚀层、若干层柔性抗辐射层和柔性耐高温气密层组成,若干层柔性抗烧蚀层、若干层柔性抗辐射层由外而内按S-F-S-F-…-S-F结构交替分布,其中S为柔性抗烧蚀层,F为柔性抗辐射层,柔性耐高温气密层位于最内侧,柔性抗烧蚀层、柔性抗辐射层和柔性耐高温气密层用硅橡胶胶黏剂粘结。
下面结合具体实例对本发明进行详细说明。
实施例1
柔性充气防热罩:
柔性抗烧蚀层4层,柔性抗烧蚀层中酚醛树脂含量分别为30%、20%、10%、5%,纳米陶瓷粉末含量分别为3%、2.5%、1.5%、0.5%,每层厚度为1.5mm;柔性抗辐射层采用0.05mm的铝箔;柔性耐高温气密层3层,每层厚度0.2mm。
具体制备工艺如下:
将100份HTV-1甲基乙烯基硅橡胶和5份过氧化苯甲酰(BPO)搅拌混合均匀。在混合物中分别加入0%、5%、10%、20%、30%的酚醛树脂和0、0.5%、1.5%、2.5%、3%的纳米陶瓷粉末为纳米碳化硼,粒径为60纳米,混合均匀备用。然后选用面密度为200g/m2的玻璃纤维平纹布,在硅橡胶涂覆机上双面涂覆,涂覆完在160~180℃硫化,得到硅橡胶涂覆织物。然后准备厚度为0.05mm的铝箔。在模具上将30%、20%、10%、5%的FQ-180酚醛树脂、3%、2.5%、1.5%、0.5%的纳米陶瓷粉末改性的硅橡胶涂覆织物与铝箔交替铺设后,再铺设3层硅橡胶涂覆织物,将所有层粘结,粘结剂采用GD414硅橡胶胶黏剂,粘接后进行室温硫化24h,脱模得到柔性充气防热罩。
本实施例制备得到的柔性充气防热罩按照GJB2620-96相关国标测试抗烧蚀性及气密性,烧蚀试验条件为:前70秒热流密度为167.47KW/m2,后60秒热流密度为376.81KW/m2,烧蚀后检查发现柔性耐高温气密层完好,未见烧蚀,同时气密性完好。
实施例2
柔性充气防热罩:
柔性抗烧蚀层3层,柔性抗烧蚀层中酚醛树脂含量分别为30%、15%、10%,纳米陶瓷粉末为纳米碳化硅,粒径为80纳米,含量分别为3%、2%、1%,厚度1.5mm;柔性抗辐射层采用0.05mm的铝箔;柔性耐高温气密层3层,每层厚度0.2mm。
制备工艺同实施例1。
本实施例制备得到的柔性充气防热罩按照GJB2620-96相关国标测试抗烧蚀性及气密性,烧蚀试验条件为:前70秒热流密度为167.47KW/m2,后60秒热流密度为376.81KW/m2,烧蚀后检查发现第一层柔性耐高温气密层表面略有烧蚀痕迹,其余两层柔性耐高温气密层未见烧蚀,同时气密性完好。
实施例3
柔性充气防热罩:
柔性抗烧蚀层5层,柔性抗烧蚀层中酚醛树脂含量分别为25%、20%、15%、10%、5%,纳米陶瓷粉末为纳米氧化锆,粒径为70纳米,含量分别为3%、2.5%、2%、1.5%、1%,厚度1mm;柔性抗辐射层采用0.05mm的铝箔;柔性耐高温气密层3层,每层厚度0.2mm。
制备工艺同实施例1。
本实施例制备得到的柔性充气防热罩按照GJB2620-96相关国标测试抗烧蚀性及气密性,烧蚀试验条件为:前70秒热流密度为167.47KW/m2,后60秒热流密度为376.81KW/m2,烧蚀后检查发现柔性耐高温气密层完好,未见烧蚀,同时气密性完好。
实施例4
柔性充气防热罩:
柔性抗烧蚀层4层,柔性抗烧蚀层中酚醛树脂含量分别为30%、20%、10%、5%,纳米陶瓷粉末含量分别为3%、2.5%、1.5%、0.5%,厚度1mm;柔性抗辐射层采用0.05mm的铝箔;柔性耐高温气密层3层,每层厚度0.2mm。
制备工艺同实施例1。
本实施例制备得到的柔性充气防热罩按照GJB2620-96相关国标测试抗烧蚀性及气密性,烧蚀试验条件为:前70秒热流密度为167.47KW/m2,后60秒热流密度为376.81KW/m2,烧蚀后检查发现第一层柔性耐高温气密层表面略有烧蚀痕迹,其余两层柔性耐高温气密层未见烧蚀,同时气密性完好。
实施例5
柔性充气防热罩:
柔性抗烧蚀层4层,柔性抗烧蚀层中酚醛树脂含量分别为30%、20%、10%、5%,各层中纳米陶瓷粉末含量均为2%,厚度1mm;柔性抗辐射层采用0.05mm的铝箔;柔性耐高温气密层3层,每层厚度0.2mm。
制备工艺同实施例1。
本实施例制备得到的柔性充气防热罩按照GJB2620-96相关国标测试抗烧蚀性及气密性,烧蚀试验条件为:前70秒热流密度为167.47KW/m2,后60秒热流密度为376.81KW/m2,烧蚀后检查发现第一层柔性耐高温气密层表面烧蚀痕迹明显,其余两层柔性耐高温气密层未见烧蚀,同时气密性完好。
本发明未详细说明部分为本领域技术人员公知技术。

Claims (10)

1.一种柔性充气防热罩,由若干层柔性抗烧蚀层、若干层柔性抗辐射层和柔性耐高温气密层组成,柔性抗烧蚀层和柔性抗辐射层由外而内按S-F-S-F-…-S-F结构交替分布,其中S为柔性抗烧蚀层,F为柔性抗辐射层,柔性耐高温气密层位于最内侧,各柔性抗烧蚀层、柔性抗辐射层和柔性耐高温气密层之间用硅橡胶胶黏剂粘结;
所述的柔性抗烧蚀层为酚醛树脂及纳米陶瓷粉体改性硅橡胶涂覆纤维织物,酚醛树脂及纳米陶瓷粉体改性硅橡胶中纳米陶瓷粉体的含量为0.5%~3%,酚醛树脂的含量为5%~30%,且由外到内各层中酚醛树脂含量逐层减小。
2.根据权利要求1所述的一种柔性充气防热罩,其特征在于:所述的纳米陶瓷粉体的含量在各柔性抗烧蚀层中相同或不同,含量不同时,纳米陶瓷粉体含量由外到内减少,即外层的纳米陶瓷粉体含量要高于内层纳米陶瓷粉体含量。
3.根据权利要求2所述的一种柔性充气防热罩,其特征在于:所述的:所述的纳米陶瓷粉体含量由外到内逐层递减,相邻两层递减不少于0.25%。
4.根据权利要求1所述的一种柔性充气防热罩,其特征在于:所述的柔性抗烧蚀层不少于3层,最外层酚醛树脂含量为25~30%,最内层酚醛树脂含量为5~10%,相邻两层之间含量梯度差不少于2%。
5.根据权利要求1所述的一种柔性充气防热罩,其特征在于:所述的柔性抗烧蚀层的总厚度为4mm~15mm,每层厚度为0.2~1.5mm。
6.根据权利要求1所述的一种柔性充气防热罩,其特征在于:所述的柔性抗烧蚀层采用的改性硅橡胶体系为热硫化型硅橡胶,改性硅橡胶体系的硫化温度不低于酚醛树脂的固化温度。
7.根据权利要求1所述的一种柔性充气防热罩,其特征在于:所述的柔性抗辐射层为铝薄膜或钛薄膜中一种或几种,厚度为0.02~0.1mm;所述的柔性耐高温气密层为1~3层,每层厚度为0.2~1mm。
8.一种柔性充气防热罩的制备方法,其特征在于,通过以下步骤实现:
第一步,制备酚醛树脂及纳米陶瓷粉体改性硅橡胶树脂体系,
A1.1、将硅橡胶和硫化剂共混,在搅拌机中搅拌均匀,得到硅橡胶体系;
A1.2、将一定量的酚醛树脂和纳米陶瓷粉体分别加入到步骤A1.1得到的硅橡胶体系中,搅拌均匀,得到不同酚醛树脂及纳米陶瓷粉体含量的酚醛树脂改性硅橡胶树脂体系;
第二步,用步骤A1.1得到的硅橡胶体系和步骤A1.2得到不同酚醛树脂及纳米陶瓷粉体含量的酚醛树脂改性硅橡胶树脂体系分别双面涂敷纤维织物,硫化后得到硅橡胶涂敷纤维织物和不同酚醛树脂及纳米陶瓷粉体含量的改性硅橡胶涂敷纤维织物;
第三步,将第二步得到的不同酚醛树脂及纳米陶瓷粉体含量的改性硅橡胶涂敷纤维织物S与金属薄膜F进行交替铺设,得到S-F-S-F-…-S-F结构,从外而内,改性硅橡胶涂敷纤维织物的酚醛含量依次递减;
所述改性硅橡胶涂敷纤维织物中纳米陶瓷粉体含量为0.5%~3%,酚醛树脂的含量为5%~30%;
第四步,在最内层的金属薄膜内铺设若干层硅橡胶涂敷纤维织物;
第五层,将所有的改性硅橡胶涂敷纤维织物、金属薄膜和硅橡胶涂敷纤维织物使用硅橡胶胶黏剂粘接硫化后,得到柔性充气防热罩。
9.根据权利要求8所述的一种柔性充气防热罩的制备方法,其特征在于:所述第三步中改性硅橡胶涂敷纤维织物不少于3层,最外层酚醛树脂含量为25~30%,最内层酚醛树脂含量为5~10%,相邻两层之间含量梯度差不少于2%。
10.根据权利要求8所述的一种柔性充气防热罩的制备方法,其特征在于:所述第三步中改性硅橡胶涂敷纤维织物中纳米陶瓷粉体含量由外到内逐层递减,相邻两层递减不少于0.25%。
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