Vacuum Effect on Coating Bead

From: http://www.frontierindustrial.com/

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随着涂料存放时间的不断延长，消光粉都会在一定程度上出现分层与沉淀。因此，在设计配方的时候，需要考虑到如何避免消光粉的沉淀（主要是指无法再次分散的硬性沉淀）。市场上可以选择的防沉助剂种类很多，包括气相二氧化硅、蜡助剂等，都有很好的防沉效果。

一般哑光漆要达到半光效果需添加消光粉3～6％，哑光效果需添加消光粉6～8％，具体用量还要根据实验确定。消光粉在使用过程中不需要研磨，直接添加到涂料中，用高速搅拌机分散10～20分钟，分散速度约1200转/分钟，细度达到5µm即可。

确定了消光粉的选择和用量以后，即可加入其它着色色浆进行调色。

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(4)变稠；变厚；发胀(Fattening)色漆在贮存过程中，由于组分间发生化学反应而引起的稠度增高(不一定增加到不能使用的程度)、体积膨胀的现象。
(5)肝化(Levering；Feeding)涂料的稠度已增加到必须经过量稀释后才能使用或仍难以使用的程度。这是由于涂料的漆基胶化或色漆组分之间的化学反应而造成的。
(6)絮凝(Flocculation)在色漆或分散体中形成附聚体的现象。
(7)胶化(Gelling)涂料从液态变为不能使用的固态或半固态的现象。
(8)晶析(Partial crystallization)含有松香组分的醇溶性清漆或油基清漆，在储存过程中松香等局部结晶析出的现象。
(9)结皮(Skinning)涂料在容器中，由于氧化聚合作用，共液面上形成皮膜的现象。
(10)沉淀；沉底：沉降(Setting)涂料在贮存过程中户，其固体组分下沉至容器底部的现象。
(11)结块(Caking)色漆中颜料、体质颜料沉淀成用搅拌不易再分散的致密块状物。
(12)有粗粒(Seedy)涂料在贮存过程中展现出的粗颗粒(即少许结皮、凝胶、凝聚体或外来粗粒)
(13)返粗(Pig Skin)色漆在贮存过程中，出于颜料的絮凝而使研磨细度变差的现象。
(14)发花(Floating)含有多种不同颜料混合物的色漆，在贮存或干燥过程一种或几种颜料离析或浮出，并在色漆或漆膜表面集中呈现颜色不匀的条纹和斑点点等现象。
(15)浮色(Flooding)发花的极端状况。某些颜料浮升至表面，虽该膜表面颜色均匀—致，但明显地不同于刚施涂时的湿膜颜色‘。
(16)起气泡(Bubbling)涂料在施涂过程中形成的空气，或溶剂蒸汽等气体，或者两者兼有的泡。这种泡在漆膜干燥过程中可以消失，也可以永久存在。
二. 涂膜缺陷(Imperfection of film)
(1)针孔(pin-holes)一种在涂膜中巾有在着类似于用针刺成的细孔的病态。它是由于湿膜中混入的空气泡和产生的其他气泡破裂，且在漆膜干燥(固化)前不能流平而造成，也会由于底材处理或施涂不当(漆膜过厚等)而造成的。
(2)起皱(Wrinkling)漆膜呈现多少有规律的小波幅波纹形式的皱纹，它可深及部分或全部膜厚。皱纹的大小或密集率可随漆膜组成及成膜时条件(包括温度、湿膜厚度和大气污染情况)而变化。
(3)橘皮(orange skin)漆膜呈现橘皮状外观的表面病态。喷涂施工(尤其底材为平面)时，易出现此病态。
(4)发白(blushing)有光涂料在干燥过程中，漆膜有时候呈现乳白色的现象。这是由于空气中的水在湿漆膜表面凝露和(或)涂料中的—种或多种出态组分析出而引起的。
(5)流挂(Runs；sogs；curtains)涂料施涂于垂直面上时，由于其抗流挂性差或施工不当、漆膜过厚等原因而使湿漆膜向下移动，形成各种形状的下缘厚度不均匀。涂层流挂可由整个垂直面上料下坠而造成的似垂帘状漆膜外观，亦称幕状流挂(curtains)，可由局部窄缝或钉眼等处的过量涂料造成的窄条状下坠，亦称条状流挂(runs)，泪状挂(tear)是条状流挂的一种特殊形式。
(6)丝纹(Ropiness)在湿漆膜表面呈现的近似平行的线状条纹，且漆膜干燥之后，这种条纹仍然存在。是由某些施涂方法而带来的一种病态。如在浸涂或流涂时，丝纹是沿着流动的方向出现；在刷涂时，丝纹则沿最后刷涂漆膜的刷涂方向出现。
(7)刷痕(brush mark)刷涂后，在干燥漆膜上留下的一条条脊状条纹现象。这是由于涂料干燥过快、粘度过大、漆刷太粗硬、刷涂方法不当等原因使漆膜未能流平而引起的。
(8)收缩(Cissing)漆膜的若干部位呈现出程度不同、分布状态各异的厚薄不匀的外观。这是由于湿漆膜与底材(或干漆膜)间的界面张力太大、润湿性小，底材表面处理不好，含有油污湿气，喷涂时管线混入油水等而引起的。底材边缘部位漆膜变薄或无漆膜现象称为缩边；漆膜上出现若干小圆孔状的收缩称为缩孔；蠕动(Crawling)是一种明显的收缩形式。
(9)缩孔(Cratering)漆膜干燥后仍滞留的若干大小不等、分布各异的圆形小坑的现象。此病态俗称为麻坑(点)。
(10)厚边(Fat edge)涂料在涂漆面边缘堆积呈现脊状隆起，使干漆膜边缘过厚的现象。这是由于不正确的施涂而造成的。
(11)蠕流(Creeping)湿漆膜自然流展开超出原漆区的现象。
(12)漏涂区；漏涂点(Miss；holidays)在某些应涂漆部位而完全没有漆膜形成的一种病态。通常是由于涂漆操作未按规定而造成。
(13)接痕(Lapping defect)在同一天的涂漆过程中由于涂漆先后不同，而在底村上各漆区的边缘接界处呈现凸起的现象。
(14)咬底(Lifting)在于漆膜上施涂其同种或不同种涂料时，在涂层施涂或干燥期间使其下部的干漆膜发生软化、隆起或从底材上脱离的现象(通常的外观如起皱)。
(15)堆漆(Piling)干燥很快的漆，在刷涂操作过程中，由于变得非常粘稠，致使漆膜厚而不匀的现象。
(16)渗色(Bleeding)来自下层(底材或漆膜)的有色物质，进入并透过上层漆膜的扩散过程，因而使漆膜呈现不希望有的着色或变色。
(17)不盖底；露底(no-hiding；show-through)涂于底面(不论已涂漆与否)上的色漆，干燥后仍透露出底面的颜色的现象。
(18)残余粘性；残留粘性(Residual tack)干燥(固化)后的漆膜表面仍滞留粘性的一种病态。
(19)闪光(Flashing)局部漆膜(尤其在接碴处)光泽高于整体漆膜光泽的现象。通常由于漆膜厚薄不匀引起。
(20)渗出；发汗(Exudation；sweating)漆膜表面析出漆基的一种或多种组分的现象。渗出液似油状且发粘。
(21)干酪化(Cheesy)漆膜虽已充分干燥，但仍相当软且机械性能差的现象。通常是由于涂料配制不当而引起。
(22)表面粗糙；起粒(Bitty appearance)漆膜干燥后其整个或同部表面分布着不规则形状的凸起颗粒的现象。这是由于涂料贮存时发生结皮、絮凝以及施工时尘土、砂粒进入湿漆膜等原因引起的。
(23)积尘(Dirt retention)干漆膜表面滞留尘垢等异粒的现象。
(24)起霜花；起晶纹(Frosting)漆膜表面呈现许多多边形或蛛网形细皱纹的现象。
(25)污气网纹(gas checking)漆膜在干燥过程中，由于受到一氧化碳、二氧化碳、氧化硫等烟雾污气笼罩，其表面出现图样清晰的网状皱纹现象。
(26)爆孔(Popping)由于底材上的一些活性物颗粒爆发。致使其上面巳部分固化的漆膜出现一个个圆锥形坑穴的现象。
(27)泛金光(Brozing)色漆漆膜表面颜色转现出古铜色金属光泽的现象。
(28)漆膜变色(Discoloration of film )漆膜的颜色因气候环境影响而偏离其起初颜色的现象。它可包括褪色、变深、黄变、漂白、变白等。
(29)褪色(Fading)色漆漆膜的颜色因受气候环境的影响而逐渐变浅的现象。主要是由于色漆中颜料(尤其是某些有机颜料)在紫外线作用下发生褪色而引起的。
(30)漂白(Bleaching)色漆漆膜因经受酸碱等化学作用，致使其颜色逐渐变浅，最终全变白的现象。这主要是由于色漆中颜料发生化学作用而分解，失去原有色彩所造成的。
(31)黄变；泛黄(yellowing)该膜在老化过程中出现的颜色变黄倾向。
(32)变深(Darkening)色漆漆膜的颜色因受气候环境的影响晰逐渐变深、变暗(黑)的现象。主要由于该基颜色固受紫外线辐射而变黄、变深.以及含铅颜料与大气中存在的硫蒸气或硫化氢气体发生化学反应生成黑色硫化铅而造成的。
(33)破坏(Perishing)漆膜在老化过程中呈现的各种性能变坏的现象。例如漆膜强度、柔韧性、附着力等降低，或出现粉化、开裂和剥落等现象。
(34)起霜；起雾(Bloom)在原来有光泽的该膜表面上呈现乳白色似霜附着物的现象。在起霜的初始阶段，很容易用湿布将霜擦去。
(35)失光；倒光(Loss of gloss; Dulling; lost of gloss)漆膜的光泽因受气候环境的影响而降低的现象。
(36)变白(whitening)漆膜经受水、汽油等液体浸泡后，由于产发生蜂窝状的溶胀而使表面呈现乳白色的现象。轻微的变白会随液体挥发而消失；严重的变白，即使液体挥发后漆膜也不能恢复原状。
(37)溶胀；膨胀；泡胀(swelling)漆膜经受液体浸泡后，由于液体渗入整个漆膜使其发生增厚、变软的现象。
(38)软化；发软(Softening)漆膜经液体浸泡后，由于溶胀而硬度明显变低的现象。
(39)起泡(Blistering)涂层因局部失去附着力而离开基底(底材或下涂层)鼓起，漆膜呈现似圆形的凸起变形，泡内可含液体、蒸气、其他气体或结晶物。
(40)开裂(Cracking)漆膜出现不连续的外观变化。通常是由于漆膜老化而引起。重要的形式为：微裂、细裂、小裂、深裂、龟裂、鸦爪裂。
(41)微裂；发丝裂(Hair cracking)很细浅的表面裂纹且分布不规则的一种开裂形式。
(42)细裂；网状细裂(checking)细浅的表面裂纹且大体以有规则的图案分布于漆膜上的一种开裂形式。
(43)小裂(Crazing)类似于细裂，但其裂纹较为深宽。
(44)深裂(Deep cracks)裂纹至少穿透一道涂层的一种开裂形式。最终可导致漆膜完全破坏。
(45)龟裂；鳄裂(Crocodiling；alligatoring)宽裂纹且类似龟壳或鳄鱼皮样的一种开裂形式。
(46)鸦爪裂(Cow’s foot cracking)裂纹图案似乌鸦爪样的一种开裂形式。
(47)剥落；脱落；脱皮(Peeling)一道或多道涂层脱离其下涂层，或者涂层完全脱离底材的现象。
(48)片落(Flaking)漆膜以大小不同、分布不匀的碎片形状呈现的脱落现象。通常由开裂造成。
(49)侵蚀；磨蚀(Erosion)漆膜由于天然；老化和风砂造成的自然磨损，且有可能导致底材裸露的现象
(50)粉化(Chalking)漆膜表面由于其一种或多种漆基的降解以及颜料的分解出疏松附着细小的现象。
(51)脆化Embrittlement；embrittling))漆膜由于老化等原因，致使其柔韧性变坏的现象。
(52)回粘(After tack)干燥不发粘的漆膜表面随后又呈现发粘的现象。此病态一般是由于聚合不足的油、沥青或其氧化产物的脱液收缩作用(即液体从胶体中排出)引起；或底材处理不当，底材中的松香、油污、增塑剂等物从漆膜表面渗出而引起。在高温高湿环境中，更容易促使产生此病态。
(53)污染痕迹；污染；污斑；污点(Stain;staining)漆膜由于渗入外来物所导致的漆膜局部变色的现象。
(54)长霉；生霉；霉染(Mildew-growing; mold-growing; fungus growing)在湿热环境中.漆膜表面滋生各种霉菌的现象。
(55)生锈；锈蚀(Rusting)漆膜下面的钢铁表面，局部或整体产生红色或黄色的氧化铁层的现象。它常伴随有漆膜的起泡、开裂、片落等病态.
(56)生白锈(White-rusting)漆膜下面的有色金属表面局部或整体产生白色粉状氧化层的现象。它常伴随有漆膜的起泡、开裂、片落等病态。
(57)针孔状腐蚀；点蚀(Corrosion pin holes)该膜表面呈现(许多)非常小的圆形腐蚀斑点的现象.这是由金属底材的腐蚀产物引起的。
(58)丝状腐蚀(Filiform. corrosion)漆膜由于其下的金属表面发生细丝状腐蚀而呈现的疏松状隆起的现象。这种丝状腐蚀常由—‘或几个腐蚀生长点辐射而成。对于钢铁底材.这种病态也称丝状锈蚀，俗称“起红丝”。

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涂料生产和施工都会不同程度地产生气泡，气泡的产生防碍生产、施工的顺利进行，同时给成品涂膜带来缺陷。正确选用合适的消泡剂可以保证涂料生产和施工的正常进行。

消泡剂的任务：破坏气泡表面液膜，阻止泡的形成和促使泡的破灭。消泡剂用于大泡，微泡需脱气、消泡一起使用。

消泡剂特点：消泡剂不溶于介质，但能以微滴形式进入并分散于介质，消泡微滴最有效的直径相当于泡沫壁的厚度。

消泡剂组成：水性建筑涂料用消泡剂分非硅类和含硅类，常规消泡剂由以下组分组成：

活性物质：起破泡消泡作用，表面张力小。代表物有动植物油、疏水二氧化硅、高级醇等。

扩散剂：润湿乳化剂，保证消泡微滴扩散接触到气泡膜并铺展。有壬（辛）基酚聚氧乙烯醚、皂盐等。

载体：有助于活性物质和起泡体系结合，易于分散到起泡体系，把两者结合起来，其本身表面张力低，有助于抑泡，且可以降低成本。

消泡剂消泡所必须具备的两个条件：渗透因子：E= γ 1＋γ12-γ3 ＞0, 保证消泡剂渗透到泡沫壁；铺展因子S=γ1-γ12-γ3 ＞0，保证消泡剂微滴在泡沫介质中的扩散铺展，消泡剂消泡的全过程见右图。

消泡剂应用中需要注意的问题：消泡剂多为几种不同性质和作用的物质混合而成，在储运中分层，为保证消泡良好使用前要搅拌均匀，COGNIS新型分子级消泡剂Foam Star 30、Foam Star 34、Foam Star 36 无分层现象，使用方便。Foam Star 36在高乳液体系高、低黏度的拉毛涂料中有良好的消泡效果。

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泡沫经常伴随着人们的生活和生产，有时需要利用泡和泡沫，像浮选、灭火、除尘、洗涤、制造泡沫陶瓷和塑料等；但有的场合却需要消除泡和泡沫，如发酵、涂料、造纸、印染、排除体内器官胀气、锅炉用水、废水处理及棱镜(或玻璃)的制造等。平常喝啤酒时由于震动啤酒中的二氧化碳转变成气态致使啤酒出现大量泡沫，这是啤瓶中加一滴油就可以消泡，这其实就是利用了消泡剂的原理。

一般而言，纯水和纯表面活性剂不起泡，这是因为它们的表面和内部是均匀的，很难形成弹性薄膜，即使形成亦不稳定，会瞬间消失。但当溶液中有表面活性剂的存在，气泡形成后，由于分子间力的作用，其分子中的亲水基和疏水基被气泡壁吸附，形成规则排列，其亲水基朝向水相，疏水基朝向气泡内，从而在气泡界面上形成弹性膜，其稳定性很强，常态下不易破裂。泡沫的稳定性与表面粘性和弹性、电斥性、表面膜的移动、温度、蒸发等因素有关。

再者，气泡与液体的表面张力反变相关，其张力愈小，则愈易起泡。在生活和生产中，很多时候泡沫的出现，给人们带来诸多不便，故必须消泡。 凡能破坏泡沫稳定性的因素，均可用于消泡。消泡涵盖“抑泡”和“破泡”两重因素。有机硅消泡剂即具备这样的功能，它能降低水、溶液、悬浮液等的表面张力，防止形成泡沫，或使原有泡沫减少，通常具有选择性作用。

一般物理消泡法难于瞬间消泡，而化学和界面消泡，则十分快捷、便当、高效。 概而言之，消泡剂是指具有化学和界面化学消泡作用的药剂。作为消泡剂，有低碳醇、矿物油、有机极性化合物及硅树脂等。其形态有油型、溶液型、乳液型、泡沫型。作为消泡剂均具消泡力强、化性稳定、生理惰性、耐热、耐氧、抗蚀、溶气、透气、易扩散、易渗透、难溶于消泡体系且无理化影响、消泡剂用量少、高效等特点。

消泡剂品种繁多，用途广泛。消泡剂“抑泡”、“破泡”过程是：当体系加入消泡剂后，其分子杂乱无章地广布于液体表面，抑制形成弹性膜，即终止泡沫的产生。当体系大量产生泡沫后，加入消泡剂，其分子立即散布于泡沫表面，快速铺展，形成很薄的双膜层，进一步扩散、渗透，层状入侵，从而取代原泡膜薄壁。由于其表面张力低，便流向产生泡沫的高表面张力的液体，这样低表面张力的消泡剂分子在气液界面间不断扩散、渗透，使其膜壁迅速变薄，泡沫同时又受到周围表面张力大的膜层强力牵引，这样，致使泡沫周围应力失衡，从而导致其“破泡”。不溶于体系的消泡剂分子，再重新进入另一个泡沫膜的表面，如此重复，所有泡沫，全部覆灭。

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在工业生产的过程中会产生许多有害泡沫，需要添加消泡剂。消泡剂的种类很多，有机硅氧烷、聚醚、硅和醚接枝、含胺、亚胺和酰胺类的，具有消泡速度更快，抑泡时间更长，适用介质范围更广，甚至苛刻介质环境如高温、强酸和强碱的特点。广泛应用于清除胶乳、纺织上浆、食品发酵、生物医药、涂料、石油化工、造纸、工业清洗等行业生产过程中产生的有害泡沫。

1、天然油脂（即豆油、玉米油等）
优点：来源容易，价格低，使用简单；
缺点： 如贮存不好，易变质，使酸值增高。

2、 高碳醇
高碳醇是强疏水弱亲水的线型分子，在水体系里是有效的消泡剂。七十年代初前苏联学者在阴离子、阳离子、非离子型表面活性剂的水溶液中试验，提出醇的消泡作用，与其在起泡液中的溶解度及扩散程度有关。C7~C9的醇是最有效的消泡剂。
C12~C22的高碳醇借助适当的乳化剂配制成粒度为4~9μm，含量为20~50%的水乳液，即是水体系的消泡剂。
还有些成酯，如苯乙醇油酸酯、苯乙酸月桂醇酯等在青霉素发酵中具有消泡作用，后者还可作为前体。

3、聚醚类消泡剂
种类挺多，主要有以下几种：
a. GP型消泡剂
以甘油为起始剂，由环氧丙烷，或环氧乙烷与环氧丙烷的混合物进行加成聚合而制成的
GP型的消泡剂亲水性差，在发泡介质中的溶解度小，所以宜使用在稀薄的发酵液中。它的抑泡能力比消泡能力优越 ，适宜在基础培养基中加入，以抑制整个发酵过程的泡沫产生。
b. GPE型消泡剂即泡敌
在GP型消泡剂的聚丙二醇链节末端再加成环氧乙烷，成为链端是亲水基的聚氧乙烯氧丙烯甘油，也叫。按照环氧乙烷加成量为10%，20%，……50%分别称为GPE10，GPE20，……GPE50。
GPE型消泡剂亲水性较好，在发泡介质中易铺展，消泡能力强，但溶解度也较大，消泡活性维持时间短，因此用在粘稠发酵液中效果较好。
c. GPES型消泡剂：有一种新的聚醚类消泡剂，在GPE型消泡剂链端用疏水基硬脂酸酯封头，便形成两端是疏水链，当中间隔有亲水链的嵌段共聚物。这种结构的分子易于平卧状聚集在气液界面，因而表面活性强，消泡效率高。

4、硅类
最常用的是聚二甲基硅氧烷，也称二甲基硅油。它表面能低，表面张力也较低，在水及一般油中的溶解度低且活性高。它的主链为硅氧键，为非极性分子。与极性溶剂水不亲和，与一般油的亲和性也很小。它挥发性低并具有化学惰性，比较稳定且毒性小。纯粹的聚二甲基硅氧烷，不经分散处理难以作为消泡剂。可能是由于它与水有高的界面张力，铺展系数低，不易分散在发泡介质上。因此将硅油混入SiO2气溶胶，所构成的复合物，即将疏水处理后的SiO2气溶胶混入二甲基硅油中，经一定温度、一定时间处理，就可制得。
有机硅消泡剂系由硅脂、乳化剂、防水剂、稠化剂等配以适量水经机械乳化而成。其特点是表面张力小，表面活性高，消泡力强，用量少，成本低。它与水及多数有机物不相混溶，对大多数气泡介质均能消泡。它具有较好的热稳定性，可在5℃-150℃宽广的温度范围内使用；其化学稳定性较好，难与其他物质反应，只要配置适当，可在酸、碱、盐溶液中使用，无损产品质量；它还具有生理惰性LD250g/Kg鼠，通常用于食品和医药行业。它对所有气泡体系兼具有抑泡、破泡功能，隶属广谱型消泡剂范畴。它被广泛用于洗涤剂、造纸、纸浆、制糖、电镀、化肥、助剂、废水处理等生产过程中的消泡。在石油工业中，它被大量用于天然气的脱硫，加速油气分离；它还被用于乙二醇的干燥、芳香烃的萃取、沥青的加工、润滑油的脱蜡等装置中控制或抑制气泡。在纺织工业中，它用于染色、精练、上浆等过程中的消泡；在化学工业中它被用于合成树脂、胶乳、涂料、油墨等过程中的消泡；在食品工业中它被用于各种浓缩、发酵、蒸馏过程的消泡。可将硅脂涂在锅壁上、出口处或涂在金属网上，进行消泡。将硅脂配成溶液，可用于油相系统消泡。将硅脂加低粘度硅油配成水乳液，可用于多种水相系统消泡。在医学上，通常用于患者术前、X光和胃镜检查前清除脏器或胃内器官的胀气。
消泡剂大致可分两类：一类能消除已产生的气泡，如乙醇等；另一类则能抑制气泡的形成如乳化硅油等。我国许可使用的消泡剂有乳化硅油、高碳醇脂肪酸酯复合物、聚氧乙烯聚氧丙烯季戊四醇醚、聚氧乙烯聚氧丙醇胺醚、聚氧丙烯甘油醚和聚氧丙烯。

5、聚醚改性硅
结合了聚醚跟有机硅消泡剂二者的优点，具有无毒无害，对菌种无害，添加量极少，是一种高性价比的产品。

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胶黏剂的定义：通过界面的粘附和物质的内聚等作用，能使两种或两种以上的制件或材料连接在一起的天然的或合成的、有机的或无机的一类物质，统称为胶黏剂（adhesive）又叫粘合剂，习惯上称为胶。（通过黏合作用。能使被粘物结合在一起的物质）

粘结（粘合）：指两个表面靠化学力、物理力或者两者兼有的力使之结合在一起的状态。

胶黏剂首先必须在被粘物表面粘附，这是由于两相之间产生粘合力，该力来源于次价键力或主价键力。

内聚：即单一物质内部各粒子靠主价键力（包括离子键、共价键、配位键、金属键等）、次价键力（包括范德华力、氢键）结合在一起的状态。胶黏剂的内聚力与分子间力、相对分子质量、交联程度、结晶和分子缠绕等因素有关。

胶黏剂的要求：

1：不论出于何种状态，当涂布时都应呈液态

2：对被粘结物表面能够完全铺展，充分润湿

3：必须能够通过某种方式而使液体转变为固体或凝胶状态，形成坚韧而稳定的胶层

4：固化后应有一定的强度。能够可靠的连接，传递应力，抵抗破坏

5：可耐0℃以上的温度，并经受一定时间的考验

1.1胶黏剂的分类

1.1.1：按照外观分类

1：溶剂型

2：乳液型（水性）

3：膏状或糊状

4：固体型

5：膜状型

1.1.2：按照固化方式分

水基蒸发型、溶剂挥发型、热熔型、化学反应型、压敏型

1.2胶黏剂的基本组成

胶黏剂的组分包括基料、固化剂、溶剂、增塑剂、填料、偶联剂、交联剂、促进剂、增韧剂、增粘剂、增稠剂、稀释剂、防老剂、阻聚剂、阻燃剂、引发剂、光敏剂、消泡剂、防腐剂、稳定剂、络合剂、乳化剂。

1.2.1 基料的种类：

基料是胶黏剂的主要成分、主剂或主体聚合物，起粘合作用。按照化学的成分的不同 ，基料的来源有无机化合物和有机化合物。有机化合物是高分子合成类的高分子基料。

1.2.1.1常用的有机化合物

热固性合成树脂：酚醛树脂、环氧树脂、氨基树脂、聚氨酯树脂、不饱和聚酯和丙烯酸树脂。

特点：低相对分子量的高聚物或预聚物制成胶黏剂后，在使用过程中通过加热或加入固化剂，或两者均有的条件下，固化成为不溶或不熔的网状高分子，其特点是施胶时胶液易扩散渗透、固化后粘结强度高、韧性好、耐蠕变性、耐热性好。但是热固性树脂胶黏剂固化过程中易产生体积收缩和内应力，使粘结强度下降。可以加入填料等改性剂加以弥补。

热塑性合成树脂：橡胶类基料、天然高分子材料、水性胶乳类 基料

特点：高相对分子质量的高聚物或预聚物，但是相对分子质量不能太高，否则在施胶时，胶液不易扩散渗透，主要应用在对粘结强度不高的场合。

橡胶类基料胶黏剂：橡胶的特点：高弹性、粘结时成膜性能良好、胶膜富有柔韧性、具有优异的耐屈绕性、抗震性和蠕变性能，适用于动态下部件的粘结和不同热膨胀系数材料之间的粘结，常用的橡胶有：天然乳胶、氯丁橡胶、丁晴橡胶、丁苯橡胶、丁基橡胶、SBS等

1.2.1.2胶黏剂基料的选择原理

根据胶黏剂应用的对象、应用的场合及应用的性能的选择。同时分子基料的分子结构与粘结性能的关系甚为密切。

1：高分子材料的极性有关

含有极性基团的基材胶黏剂对极性材料的粘结性能较好，而对非极性材料较差；反之相同。

2：高分子材料的结晶性能

适当的结晶性能能够提高高分子材料本身的内聚强度和粘结力，有利于粘结。但是结晶性能太高，分子中的极性基团受束缚，不利移动，其溶解性能也差，粘结性能变差

3：高分子材料的分子量

分子量小，分子的活动能力和胶液对被粘材料的湿润能力强，但是太小时候，材料的内聚力太低，造成粘结强度偏低。一般选择分子量较为均匀的树脂。

1.2.2固化剂（硬化剂）

使基态原料通过化学反应，发生聚合、缩聚或交联反应转变为线性高聚物或者网状高聚物，是胶接接头具有力学强度和稳定性的物质。

固化剂的选择：

1：最好是液体的无毒、无色、无味的物质

2：固化剂与被固化物反应要平稳，放热量少，以减少胶层的内聚力

3：耐热性，选用分子中具有反应基团较多的固化剂

4：韧性，选用分子链较长的固化剂

1.2.3胶黏剂溶剂

指能够降低某些固体或者液体分子间力，而使被溶物质分散为分子或离子均一体系的液体，常用的溶剂为低粘度的液体物质。主要有脂肪烃、芳香烃、卤代烃、酯类、醇类、酮类、酸类、醚类、萜烯烃、酰胺类和水类。但是多数的有机溶剂有一定的毒性、易燃性、易爆性、对环境有污染、对安全又隐患、对人体有危害。

溶剂的作用：

1聚合反应的介质：是反应缓和、温度易于控制、

2 溶解基料：制备溶剂型胶黏剂

3：稀释剂：稀释胶黏剂使其达到一定的黏度，有利于湿润、便于涂布

4：调节胶黏剂的挥发速度

5：防止凝胶，用来增加贮存稳定性

6：粘结前的表面清洁处理剂

7：直接粘结，某些塑料

8：降低成本、提高效益

选择

1：极性 选择与基料极性相同或相近的溶剂（相似相容的原理）

2：溶解度参数（与极性有关） 溶剂的溶解度参数和高分子基体的溶解度参数相近

3：溶剂的挥发性：选择挥发度适当的溶剂或快慢混合的溶剂

溶剂挥发太快：胶液表面易成膜、膜下溶剂不易挥发；挥发是一个吸热的过程，太快胶膜表面的温度降低而凝结水汽，影响粘结质量

溶剂挥发太慢：表干时间慢，影响工效

溶剂的选择要考虑到价格、毒性和来源

1.2.4增塑剂

是一种降低高分子化合物玻璃化温度和熔融温度，改善胶层脆性、增进熔融流动性的物质。

作用：

1：屏散高分子化合物的活性基团，减弱分子间作用力，从而降低分子之间的相互作用

2：增加高分子化合物的热性、延伸性和耐寒性，降低其内聚强度、弹性模量及耐热性。

选择：

1：极性 极性大小影响增塑剂与主体材料的相容性，其原理同溶剂作用。

2：持久性：由于渗出、迁移、挥发二损失影响胶的物理机械性能。选择高沸点的或高分子量的增塑剂

3：分子量及状态：分子量越高，粘结强度越好

常用的增塑剂：

邻苯二甲酸酯、磷酸酯类、己二酸酯和癸二酸酯等

1.2.5填料

在胶黏剂中不与基体起化学反应，但是可以改变其性能，降低成本的固体材料

常用的填料分为有机填料和无机填料：

有机填料：改善树脂的脆性、吸湿性高、耐热性能低

无机填料：使胶的相对密度增加、脆性增加、但耐热性、介质性能、收缩率等都会有所改善。

填料的选择：

1：无活性与胶黏剂的其他组分不发生反应

2：分散性好与基料有良好的润湿性

3：不含水分、有害物质、油脂，无吸湿性

4：颗粒均匀。无毒

5：来源广泛、加工方便、价格低廉

6：填料的密度与基料的密度不能相差太大

7：用量适宜

常用的填料：二氧化硅、碳酸钙、碳酸镁、铝粉、酚醛树脂等

1.2.6偶联剂

能同时与极性物质和非极性物质产生一定结合力的和化合物，其特点是分子中同时具有极性和非极性部分的物质。常用的偶联剂有有机铬偶联剂、有机硅偶联剂和钛酸酯偶联剂。

在胶黏剂中常用的是硅烷偶联剂。

偶联剂的作用

1增加主体树脂

本身的分子间的作用力，提高胶黏剂的内聚强度

2增加树脂与被粘合物之间的结合，起了一定的架桥作用。

不同的偶联剂具有不同的反应基团，反应基团不同对粘结性能的影响也不同。

1.2.7其他助剂

引发剂：在一定的条件下能分解产生自由基的物质，一般含有不饱和键的化合物中加入引发剂，常用的引发剂有过氧化二苯甲酰、过氧化环己酮、过氧化异丙苯、偶氮二异丁氰等

促进剂（催化剂）：能够降低引发剂的分解温度或加速固化剂与树脂橡胶反应的物质。

防老剂：能延缓高分子化合物的老化的物质，对于高温、暴晒下使用的胶黏剂由于容易老化变质，在配胶时加入防老剂

增稠剂：粘度低的胶黏剂，增加使其粘度增加的物质

阻聚剂和稳定剂：阻止或延缓含有不饱和键的聚合物、单体在贮存过程中自行交联的物质(对苯二酚)

1.3胶黏剂的选用原则

1.3.1根据被粘材料的化学性质进行选择胶黏剂

A． 被粘材料的分子结构选择（基团的类型）

B． 被粘材料的极性选择

极性的大小有分子结构的正负电荷中心重合程度决定的。

强极性材料：金属、剥离、陶瓷、云母和含有极性基团（-OH、-NH2 、-COOH、-CN、-CO-NH2 、-SH）的聚合物选择极性胶黏剂

极性材料使用胶黏剂：酚醛-丁腈胶、酚醛-缩醛胶、环氧胶、丙烯酸聚酯、无机胶、聚氨酯胶、聚酰亚胺胶、不饱和聚酯胶、氯丁-酚醛胶、脲醛树脂胶、聚乙烯醇胶、聚醋酸乙烯乳胶、

非极性材料：聚乙烯、聚丙烯、聚苯乙烯、聚苯醚、硅树脂、硅橡胶、和含氟聚合物

非极性材料使用胶黏剂：聚异丁烯胶、EVA热熔胶、聚氨酯胶、丙烯酸聚酯胶、有机硅胶、硅橡胶

弱极性材料：有机玻璃、聚碳酸酯、氯化聚醚、聚氯乙烯、ABS、天然橡胶、丁苯橡胶

弱极性材料的使用的胶黏剂：聚氨酯胶、丙烯酸聚酯胶、氯丁胶

C、综合考虑被粘物的种类和性质选择胶黏剂

对被粘物了解的越透彻、选用的胶黏剂会越合适、粘结的效果会越好。

D、根据被粘材料的结晶性选择胶黏剂（被粘结物多属于结晶材料）

在粘结强度要求不高时，结晶聚合物可选用非极性或弱极性材料的胶黏剂

对粘结强度要求高的时候，被粘材料经适当的表面处理后，可选择极性胶黏剂

1.3.2、根据被粘材料的物理性能进行选择胶黏剂

A根据被粘材料的表面张力选择胶黏剂

胶黏剂的临界表面张力应小于被粘材料的临界表面张力（浸润性决定作用）

B 根据被粘材料的溶解度参数选择胶黏剂

二者的溶解度参数差不应大于0.5

C 根据被粘材料的脆性和刚性选择胶黏剂

质地硬脆的材料：选用强度高、硬度大切不易变形的热固性胶黏剂。环氧树脂、酚醛树脂、不饱和聚酯等胶黏剂

坚韧、强度高的刚性材料：选用强度高、冲击强度好切剥离强度也好的胶黏剂。热固性树脂和橡胶复合型胶黏剂（酚醛-丁腈胶、酚醛-缩醛胶、环氧-丁腈胶）

D 根据被粘材料的弹性和韧性选择胶黏剂

弹性形变大的材料：选用有相应的弹性和韧性的胶。如氯丁橡胶、聚氨酯胶、氯丁-酚醛胶

质地柔软的材料：选用韧性优良的胶黏剂（氯丁橡胶、聚氨酯、聚乙烯醇缩醛、聚醋酸乙烯等胶黏剂）

1.3.3根据胶黏剂的效能选择胶黏剂

胶黏剂的性能指标：状态、粘度、适用期、固化条件、使用温度、粘结工艺、粘结强度、使用温度、收缩率、膨胀系数、耐腐蚀性、耐水性、耐油性、耐介质（水、酸、碱、油、溶剂）、耐老化性能等

1.3.4根据接头的功能要求选择胶黏剂

接头的功能：机械强度（拉伸、剪切、剥离强度等）

耐热性能：200℃以下

耐油特性、耐水特性、光学特性

1.3.5根据许可的固化条件选择胶黏剂

固化过程的温度、压力、时间是影响粘结强度及其他性能的三个主要因素。

1.3.6其他因素

A:粘结的目的与用途

胶黏剂具有连接、密封、固定、定位、修补、填充、堵漏、嵌缝、防腐、灌注、罩光以及满足某种特殊要求等多种功效。

B：粘结件受力的情况

外力：拉伸、剪切、撕裂、剥离四种力，力的大小、方向、频率、时间。

C:粘结件的使用环境

温度、湿度、介质、真空度、辐射计户外老化

D:工艺的可能性

粘结工艺：室温固化、加热固化、加压固化、加热加压固化、固化时间的长短

E:考虑是否经济和来源难易

1.4胶黏剂的粘结工艺

粘结的一般工艺程序

确定被粘结物——选择胶黏剂——表面处理————配胶——涂胶——凉置——粘结——固化——检查——整修

1.4.1表面处理

改变被粘结物表面不利的粘结状态。

表面处理法法：机械处理、物理处理（火焰处理、放电处理、等离子放电） 化学处理（酸碱等化学处理剂）、辐射接枝处理

金属材料的表面处理：

1：除油（碱液、有机溶剂、电解、超声波）

2、除锈（化学侵蚀、电化学侵蚀）

表面处理的检验（水膜）

表面处理的有效时间

1.4.2配胶

单组份直接使用

双组分：按照比例进行配胶。A、B成分相对误差不超过2~5%

1.4.3涂胶

涂胶遍数（1 、2~3）、涂胶量（0.08~0.15mm）、涂胶方法（刷涂、喷涂、浸涂、注入、漏涂、滚涂、刮涂等）

1.4.4凉置

是溶剂蒸发、粘度增大、促进固化

溶剂胶（3~5min）

1.4.5粘结

粘结后以挤出微小胶圈为好，表示不缺胶。

1.4.6固化

初固化、基本固化、后固化

固化因素：固化温度（室温、低温、高温）、固化压力、固化时间

1.4.7检查

目测法、敲击法、溶剂法、

1.4.8：修整

二、胶黏剂开发设计原理

2.1胶黏剂基料的分子结构设计及其与性能的关系

胶黏剂的配方设计是根据其用途与功用，选择合适的材料配置成胶黏剂。或者是根据高分子材料分子的化学结构与材料物性之间的相互关系，合成具有所需功能的材料配置成胶黏剂

分子结构的设计主要是研究粘结特性与分子结构的关系

2.1.1高分子主链结构

高分子的主链元素一般为C-C键组成的饱和、不饱和的烷烯炔等直链、环状结构的高分子材料。有时还包含O、Si 、卤素、等杂原子组成的化合物。

主链结构决定聚合物的刚柔性。 C=C-C=C-C

1：单键组成的柔性大

2：含有芳杂环结构的刚性大、耐热性能好

3: 孤立双键的大分子。也具有柔性

4：共轭双键的化合物，不能够旋转，刚性大

柔顺性：

链长：分子链越长，柔韧性越好 C-C-C-C-C

重键：不易内旋，为刚性键

取代基团：基团的极性小、内旋容易、柔顺性好；距离远好

分子间作用力：小，柔顺性好

2.1.2高分子侧链结构 C-C-C-C-C

侧链的引入可以对高分子聚合物进行改性，

提高粘性：引入极性基团 –Cl 、-P 等

疏水性： 引入 F Si -O- 等

侧链的极性大小。对聚合物分子内和分子间的吸引力有决定性的作用。

基团的极性好、吸引力低、分子柔韧性好

极性大、聚合物分子内和分子间的吸引力高，聚合物的内聚强度变高，柔性降低

侧链基团的体积大小决定其位组作用的大小：体积大、位组大、具有刚性

但是侧链基团为直链状时，链长增加，位阻减小，柔韧性增加 C-C-C-C-C

侧链基团连接在同一个C原子上时，位阻大

2.1.3交联度

在线性长分子链之间产生化学交联时，聚合物的粘结性能和其他性能都发生改变。

交联度越低，柔韧性越好、越高，硬度越大，刚性和脆性越大。

交联类型：

1：在聚合物分子链上任意链段位置的交联。(聚合物的主链结构、交联剂的种类和数量、交联工艺条件等)

2：通过聚合物末端的官能团进行硫化（交联度取决于相对质量的大小）

3：通过侧链官能基团进行交联。（交联度取决于侧链基团的数目）

4：物理交联 （加热熔融形成聚集点）

2.1.4结晶性

规则排列的聚集状态。结晶性对玻璃化温度和软化点有很大的影响

粘结性能的影响取决于：结晶度、晶粒的大小及晶体的结构

聚合物晶态的形成主要是受气分子结构的影响：

1：化学结构越简单，越易结晶

2：分子链月规整，越易结晶

3：链上取代基的空间位阻越小，越易结晶

4：链段间的相互作用力越大，越有利于结晶

结晶性与胶黏剂的特性之间的关系

1：高结晶的聚合物：分子链排列紧密有序。孔隙率较低，结晶时分子间的相互作用力增大，分子链难以运动并导致聚合物硬化和脆化，粘结性能下降。但是结晶化提高了聚合物的软化温度，聚合物的的力学性能对温度变化的敏感性能减少。

2：聚合物球茎尺寸的大小：打球晶的存在时聚合物内部有可能产生较多的空隙和缺陷，并降低其力学性能

3：伸直链组成的纤维状的聚合物结晶，能使聚合物有较高的力学性能

4：加热某些结晶聚合物，可使结晶体中按一定规则 排列的分子发生混乱，是分子运动变的容易向熔融状态过度。此类聚合物可以作为热熔胶使用。

5：在某些情况下，结晶作用也可以用于提高粘结强度。（氯丁橡胶）

2.1.5分子键能

实验表明内聚力必须大于2.1×104J/mol，它与极性表面的粘附力才足够大，此类聚合物文物才可以作为胶黏剂的基料。

2.1.6相对分子质量及其分布

相对分子质量比较小的聚合物，粘度低、熔点低、粘附性能良好、但是内聚能低，导致粘结内聚强度不高。

相对分子质量较大的聚合物，难以溶解，熔点高、粘度大，粘附性能较差，但是内聚强度较大，可获得粘结内聚强度较高的胶黏剂。

聚合物的相对分子质量相同但是相对分子质量的分布不同，其粘结强度也不相同。低聚物含量较高时，接头破坏成内聚破坏，高聚物含量较高时，接头破坏成界面破坏

2.1.7分子的极性

高能表面：基料分子的极性越强、胶黏剂的粘结强度越高。

低能表面：基料分子的极性越弱、胶黏剂的粘结强度越高。

2.2高聚物的组成与力学性能

大多数胶黏剂的基料成分为非晶态聚合物（晶态聚合物的粘附性差）

2.2.1非晶态聚合物的力学性能

应力：单位面积承受的作用力，其基本形式有 拉伸应力、剪切应力和流体静压力

聚合物的力学性能决定于其分子运动

1：分子链中键角的改变会引起材料的弹性形变，其特点是速度快、形变可逆范围在1%的数量级

2：链段围绕主轴旋转，分子构像发生变化，引起可逆的高弹性形变（100%）

3：分子链之间相对位置发生变化所引起的是塑性形变，是不可逆的。

2.2.2胶黏剂的基本组成与力学性能的关系

除了粘结界面结合力外，粘结强度与胶层内聚强度（胶黏剂的强度）有关。

各影响因素对制备综合力学性能的胶黏剂的影响

1：聚合物相对分子质量 ：机械强度、低温韧性、粘度提高，浸润速度减慢

2：高分子的极性增加：内聚力、对极性表面吸附、耐热性、粘度增加，耐水性下降

3：交联密度提高：耐热性、耐介质性、模量、低温脆性增加；但蠕变、延伸率降低

4：增塑剂用量增加：冲击强度、蠕变增加；粘度、耐热性、内聚强度增降低

5：增韧剂用量增加：韧性、剥离强度增加，内聚强度、耐热性下降

6：填料用量增加：硬度、粘度、脆性增加；固化收缩率降低，成本下降

7：偶联剂的加入： 粘附性、耐湿热老化性能提高；有时耐热性降低

2.2.3非晶态聚合物的聚集状态与组成设计

线性或网状非晶相的聚合物都具有玻璃态、高弹态和粘流态三种不同的力学聚集状态。实际上他是材料力学性能受温度影响而发生的力学聚集状态。

玻璃化温度：Tg Tg决定聚合物分子链段的能垒，

2.2.4高聚物内聚强度与基料的选择

聚合物内聚强度的决定因素

1：基料的分子结构、分子间的作用力（微观、局部的强度0和分子键能 极性表面：键能大于20.9KJ/mol

2：材料的强度也与材料中的缺陷大小及分布有关。

提高胶黏剂的强度：

1：增强聚合抵抗裂缝扩展的能力（内聚力、机械强度、韧性增加）

2：减少材料中的缺陷

三、配方优化设计的方法

单因素优选法、多因素轮流优选法、正交实验法、

3.1单因素优选法

在胶黏剂的几个组分中，将（n-1）个因素固定，逐步改变一个因素的水平，根据目标函数评定该因素的最优水平，依次求取体系中个因素的最优水平，最后将各因素的最优水平组合成最好的配方。

最基本的方法。黄金分割法（0.168法）和分数法。

3.2多因素轮流优选法

其实质是每次去一个因素，按照0.168法优选，依次进行达到各因素优选。

3．3正交实验法

对各因素选取数目相同的几个平均值，按照均匀搭配的原则，同事按排一批实验，然后对实验结果进行统计分析，研究各因素间的交互作用，寻找最佳配方。

四、胶黏剂固化工艺的设计

4.1胶黏剂的固化方法

物理固化和化学固化

压力、温度、时间是固化过程的三个主要参数

4.2热熔胶的固化工艺设计

热熔胶的粘结时由熔融高分子浸润被粘表面后通过冷却发生固化，使用时必须控制熔融温度和涂胶后的凉置时间。

1：聚合物是结晶性的，冷却速度要控制

2：热熔胶本身的相对分子质量制约着温度的控制，热熔胶的强度和本体粘度是相互制约的

3：增粘剂和蜡的加入降低热熔胶的熔体粘度，改善使用工艺

4.3溶剂型胶黏剂的固化与溶剂选择

溶剂型胶黏剂的固化过程是高分子溶液浸润被粘物表年后，随着溶剂的挥发，溶液粘度不断增大直至达到一定的强度而固化。其中关键的是溶剂的选择和混合溶剂组分及配比。溶剂的要求包括溶解度、挥发性、与被粘材料的兼容型及毒性。

溶解度参数相近，分子结构相似，才能形成真正的聚合物溶液，对被粘表面有良好的浸润作用。

4.4热固性胶黏剂的固化工艺设计

热固性树脂是具有三项交联结构的聚合物，他具有耐热性好、耐水、耐介质优良、蠕变低等优点。

4.4.1热固性胶黏剂的固化方法

1：把现行高分子交联起来，如橡胶的硫化

2：由多官能团的单体或预聚体聚合成三相交联结构的树脂，如环氧树脂胶黏剂。

配方和固化周期对固化产物性能都有很大的影响

4.4.2凝胶化及凝胶化的影响因素

凝胶化：多官能提案单体或预聚体进行聚合反应时，随着分子量的增大，同时进行着分子链的支化和交联，当反应达到一定的程度时，体系中开始出现不熔、不溶的凝胶。

凝胶化的速度取决于官能团的反应活性以及多官能团单体的浓度和官能度。

4.4.3凝胶化后的反应

1：可溶性树脂增长反应

2：可溶性树脂分子间反应变成凝胶

3：可溶性树脂与凝胶之间的反应

4：凝胶内部进一步反应时交联密度提高

4.4.4固化温度和时间对胶黏剂性能的影响

基料和固化剂的交联反应都是在一定的温度下进行，在此温度范围内：温度越高、反应速率越快、反应进行的越完全，所需的固化时间越短。

克服化学能垒：固化温度要高，但是放热反应，固化温度不能太高以免局部过热、造成胶层内部的交联密度、化学成分的区域间的巨大差异、进而导致内应力的产生。

五、改变胶黏剂性能的设计原则

5.1粘结强度的改进设计

1：选择粘结力和内聚力都大的树脂(环氧树脂、聚氨酯)

2：加入增韧剂、降低脆性、增加胶层韧性，减小内应力

3：热固性树脂和热塑性树脂或橡胶并用，热固性树脂提供强力和耐热元素，而热塑性树脂提供粘性和韧性元素。综合结果会得到较高的粘结强度

4：引入极性基团或加入相容性能好、极性大的树脂，可提高橡胶型胶黏剂的粘结强度

5：适当的交联剂。

6：添加适量适当的填料、降低收缩率，晶须或纳米田纳西奥效果极佳

7：加入适当的偶联剂

8：加入稀释剂，降低粘度，增大湿润性

5.2耐热性的改进设计

1：采用耐高温性能好的树脂或橡胶（酚醛树脂、有机硅、氟橡胶、杂环聚合物）

2：提高环的密度，

3：增加交联剂

4：适当地提高结晶度

5：使用耐高温性能好的固化剂

6：加入耐热填料

7：减少高温氧化分解，加入抗氧剂

8：添加硅烷偶联剂

5.3耐寒性的改进设计

1：选用耐寒性的聚合物，如聚氨酯

2：加入增塑剂或增韧剂

3：降低交联度

4：降低结晶性

5：减少填料用量

5.4耐溶剂性的改进设计

1：采用耐溶剂好的树脂或橡胶

2：增加交联度

3：适当增大填料的用量

4：少用或者不用增塑剂

5.5耐酸碱性的改进设计

1：提高交联度

2：选用惰性填料

3：提高填料的用量

4：酯类增塑剂不耐酸

5.6耐水性改性设计

1：选用分子中含有-CN、-NH2、-OH、 -COO-等基团少的聚合物吸水性低，不易被水解。

2：增加胶黏剂基料的用量

3：使用耐水性固化剂

4：提高交联密度

5：所用填料为吸水性较小的品种

6：加入偶联剂，改善界面性质

5.7耐老化性的改进设计

1：选用耐水性、耐候性和耐老化性能好的基料

2：提高交联度

3：加入活性填料

4：某些胶黏剂中可适当的加入防老剂或抗氧化剂

5：加入适量的有机硅烷偶联剂

6：使用高温固化剂

5.8：阻燃性的改进设计

1：选用阻燃性的树脂和橡胶味基料

2：采用阻燃性的增塑剂

3：加入阻燃剂，如三氧化二锑、硼酸锌

4：使用阻燃性固化剂。

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The principal reasons for the wide spectrum of uses of silicones as components in the production of paint additives are:
•  low surface tension
•  excellent lubricating
•  slip properties

The surface tension of silicones is around 20 mN/m, which means that silicones quickly form a film at interfaces, when introduced into a liquid.

Differently structured silicones form films at the interface between substrate and coating and promote wetting of the substrate. Similarly specially selected silicones move to the air/liquid paint interface where they destabilise the air bubbles and cause them to burst. After application of a coating system this film is formed on the surface and produces a slip effect.

The possible application of silicones depends very much on their molecular structure and molecular mass. The basic building brick of all silicones is polydimethylsiloxane which has the molecular structure:

The following table presents a summary of these relationships displayed by polydimethylsiloxanes:

Polydimethylsiloxanes distinguish themselves only by the length of the polymer chain (i.e. magnitude of "x"). The average molecular mass (or the viscosity) is a measure of the length of the polymer chain (i.e. degree of polymerisation). The properties of these silicones with a simple structure depend therefore solely on the molecular mass.

2. Modified polydimethylsiloxanes
By chemical modifications of the molecular structure of polydimethylsiloxanes, modified silicones with new properties are obtained. A schematic chemical formulation of such modified silicones is shown in the following illustration:

The organic modification can represent any desired molecular grouping with the exception of the alkyl group ( -CH3).

The properties of these silicone products depend on three factors:
•  type of organic modification
•  relation of the x- and y-units
•  molecular mass

3. Silicone copolymers
Silicone co-polymers are compounds, which combine the properties of silicones with those of the corresponding co-polymer. This combination creates products with new interesting properties.

They minimise the risks incurred by accidental excessive dosage of ‘normal’ silicone oils like
•  cratering
•  poor adhesion
•  recoating problems
•  incompatibility in systems

Polyethers or polyesters are frequently used as the co-polymer component. The schematic chemical structure of silicone copolymers is:

Planned chemical synthesis can produce exactly the desired properties of silicone co-polymers. The m-unit is the hydrophilic organic component, the n-unit the hydrophobic organic component and the p-unit contributes the typical properties characteristic of the silicone co-polymer. The m-n-p-mass ratio therefore determines the overall properties of the silicone co-polymer.

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Written By: David Brassard

Edited By: Mr. David Crossan, Sr. Editor

Abhesion – lack of adhesion, easy release from substrates.

Abrasion – surface wear from friction.

Acetoxy cure system – a tin catalyzed moisture cure system that liberates an acetic acid/ vinegar odor by-product upon curing.

Adhesion – the bonding to a substrate by an adhesive or other agent.  May be chemical, mechanical, or a combination of both.

Adhesion promoter – a silane or zirconate compound which enables a self-priming bonding capability when utilized in adhesives.

Adhesive – elastomers, resins or PSA’s that are designed to display self-bonding properties to substrates without primers

Addition cure system – a reaction between a two PDMS polymers, where no by-products are generated.  Typically referred to as Platinum cure systems, where vinyl terminated PDMS and a methyl hydrogen copolymer PDMS crosslink with a platinum catalyst.

Si-H + CH2 = CHSi ————> SiCH2CH2Si

Can also be a peroxide initiated, free radical cure between two PDMS methyl groups or a methyl and a vinyl group, or two methyl groups resulting in crosslinking of a silicone.

Agglomerates - are large clusters of aggregates and primary particles.  In fumed silica’s, they are attracted by hydrogen bonding of the surface silanols.  They can be broken apart through shearing.

Aggregates – are clusters of primary particles.  In fumed silica’s, they are attracted by hydrogen bonding of the surface silanols.  They can be broken apart through shearing.

Alkoxysilane – a compound containing a central silicon atom and an Si-OR functionality, where R represents a aliphatic organic group.  Upon hydrolysis, generates a alcohol molecule.

Application time/life – the usability time of the product after catalyzation is measured here.  Often identified as how long until a product will not flow, enable tooling or application into the assembly.  Also known as work life, pot life.

Application rate – used to measure the flow of RTV sealants from a semco tube. Material is extruded from a semco tube at a stated pressure, usually 60 or 90 PSI through a standard orifice. Reported in grams per minute.

Antifoam – a liquid product that when added to a composition retards or inhibits the development of a foam in the composition.

Arc Resistance – denotes the resistance of a material to a to an arc produced by an electrical current between two electrodes.

ASTM – American Society of Testing Materials, they define standard test methods for industry.

Base – a silicone compound that is only partially compounded with fillers.  Often un-colorized and un-catalyzed, fabricators of finished rubber parts use bases in formulating their own special compounds.

BET surface area – is a method developed by Brunaer, Emmet and Taller in 1931, which is a means of displaying the surface area of powders by measuring the amount of gas absorption under varying pressure conditions.  The larger the BET gets, the smaller the primary particle and the larger the surface area of the powder.  The BET value relays the square meters of surface area per gram of powder.

Bladder cure - a surface only cure condition in a deep section cured product

Bleeding – the surface release of a plasticizer or incompatible liquid component from a cured elastomer.   Can also identify a oil separation from an uncured product.

Blow-out resistance – a green strength – resistance to be displaced while in an uncured state found in some sealants, useful in assembly applications, especially automotive engine assembly. 

Brittle point – denotes the lowest temperature than an elastomer can be subjected without breaking or shattering upon sudden impact or stress.

Bulk modulus – is the elastic/energy absorption capability property of an elastomer when compressed.  Silicone rubber will deform approximately only one half of what an organic rubber will when exposed to the same stresses. This is due to the siloxane bond spacing and the high free volume in a crosslinked matrix.

By-products – the evolved reaction materials of a condensation cure silicone with moisture. These typically generate the odor found when silicones cure.

Catalyst – is a reagent that when added to a compound, initiates a chemical reaction, but is not consumed by the reaction.

Caulk – is a compound that is used to fill crevices to enable a moisture or weather-proof seal.

Centipoise = a unit of measure for liquid materials.  One hundredth of a poise.  (centistokes x specific gravity)

Centistokes = like centipoises, it is also a method of defining the viscosity of liquids.  (centipoises / specific gravity)

Chain extension – a process where a high molecular weight linear polymer is fabricated from many lower molecular weight linear components.

Chain stopper – an M unit utilized in polymerization reactions, which limits chain growth by having only one hydrolyzable or reactive functional group on the molecule.

Chlorosilane – a compound containing at least one Si-Cl bond.  Silanes typically being tetrafunctional, have multiple chlorines and/or organic components.   These are the building blocks of silicones.

CIPG – cure in place gasket.  Applying a wet silicone to a part & allowed to dry.  Then the part is compressed onto the other substrate compressing the gasket.  Compression forces maintain the seal.  Adhesion to only the first substrate is required to hold the gasket in-place during assembly.

Coefficient of thermal expansion or CTE– the material’s fractional change in dimensions typically measured in length for a given unit change in temperature.

Cohesion – the strong attraction of a substance to itself enabling a high resistance to splitting or tearing.  Often accomplished through the chemical bonds from crosslinking and reinforcement.

Condensation cure system – a composition, which is capable of a reaction between silanol terminated polydimethylsiloxane and multifunctional crosslinker with a catalyst.  This reaction creates a water molecule.

Si-OH + AcOSi ———- > Si-O-Si + AcOH

Compatible – materials that can be mixed or blended without any chemical reaction or separation taking place.

Compound – this has very different meanings:

1. a substance containing two or more elements united in definite proportions by weight.

2. to mix or incorporate finely divided solids into a polymeric material.

Compression set – the reduction in thickness of a material caused by the loss of a spring-back capability after being in a compression condition for a period of time.   This spring-back capability id key as it creates the sealing forces of a rubber in a compression gasket application.

Copolymer – is a compound that contains two different chemical structures within the backbone as the repeating units.

Creep – is a cold flow like deformation of a cured elastomer under a load

Crepe Hardening – the thickening of an uncured silicone upon ageing caused by hydrogen bonding.  Can be offset by softening on a mill or shearing in a mixer.

Crosslinker – a silane or methyl hydrogen compound, which when utilized properly in compositions, will enable the formation of chemical bonds.

Crosslink density – the concentration of chemical bonds within a cured rubber or elastomer.  Measured by durometer and modulus.

Crosslinking – a series of reactions that occur as an uncured silicone material cures to form a cured material.

Cryogenic – having a very low temperature, in the range of –200^oF and lower.

Crystalline – is a solid with a very regular, lattice molecular architecture. 

Cure moderator – cure moderators are added to formulations to function as a timer to delay cure.   Very low molecular weight components will preferentially crosslink prior to the higher molecular weight components.  Slowly increasing in molecular weight until the viscosity meets the base polymer, then the product would rapidly cure.  Through formulation, they enable a very accurate 2 to 30 minute open time prior to a rapid cure.

Cure speed/time – The time required to convert the silicone elastomer to cured rubber. Example: 24 hours for 1/8” diameter bead at 77° F and 50% relative humidity or 15 minutes @ 150^oC.

Curing– a crosslinking reaction which enables silicone liquids, pastes or rubber compounds to harden to a three dimensional matrix.

Curing agent – a material which when added to a second material, brings about a chemical reaction, usually causing the hardening of the entire mass. 

Cureometer – a test device, which measures polymer properties as it cures/crosslinks.

Cure time – the time lapsed between the addition of a catalyst and the complete hardening of a material.

Cyclomethicone – a low molecular weight cyclic PDMS usually D-3, 4, or 5 and sometimes blends. This is a term utilized by the healthcare industry.

Cyclics – a term used to depict the volatile oligomeric components often found in silicone materials as a result of incomplete copolymerization.  These can be removed through post baking parts or de-volatization of polymers.  Cyclics are compounds that are in closed rings as opposed to linear, aliphatic chains.

D-4 – is industry shorthand to typically depict octamethylcyclotetrasiloxane, a volatile low molecular weight cyclic oligomer.   Vinyl D-4 has a vinyl functional group substituted on each silicon atom for a methyl, resulting in a methyl and vinyl group being pendant on each silicon atom.

Deep section cure – a silicone product that is formulated to enable cure to any depth or dimension.  Most typically found in a 2-part product where all components required for cure are incorporated.  Unlike a 1-part moisture cure, which requires atmospheric moisture permeation and cures slowly from the outside in.

Dehydrogenation – a chemical reaction where hydrogen is released from a compound.

Density – mass per unit volume, as compared to water.  Typically reported in grams/cubic centimeter.

Dielectric strength – the point when a material loses its insulation capability and enables an electrical current to pass through.  Typically measured in volts at a given thickness.

Dilatant – a rheological capability to display increasing hardness upon exposure to shear.

Dimethicone – another healthcare industry term for Trimethyl terminated PDMS fluid, It is also called simethicone. Found in many consumer products, skin and anti-flatulence preparations just to name a few.

Dimethylsiloxane – see PDMS

Dipodal – a silane having twice the level of the typical trimethoxy functionality.  This silane molecule will have two functional pendant hydrolysable trialkoxy groups.  One is found at each ends of the molecule. 

Dispersions- elastomeric or resinous product dissolved in a solvent carrier.  Dispersions are applied to substrates and allowed for the solvent to evaporate prior to use. A dispersion allows a very thin film to be applied.

Durometer – resistance to indentation. The measure of the crosslink density of a rubber sample via ASTM D-2240.

Endcapping – The functionalization of a polymer terminus.

Elastomeric – is a rubber-like substance displaying a stretching capability.  Some define as the ability to stretch to at least twice its length under light stress and snaps back to its original length upon the release of the stress.

Elongation – (elongation at break) the ability of the test piece to be stretched without breaking. Given in % of original dimension @ maximum elongation. Maximum elongation is determined by attaining the point of breakage. Typically measured via ASTM D-412.

Emulsion – is very small droplets of oil uniformly suspended in water, typically accomplished through the aid of chemical emulsifiers and high speed milling or high pressure homogenization.

EMI/RFI – electromagnetic interference or radio frequency interference are applications that require shielding of cables and apparatus.  Electrically conductive silicones are used for shielding.

Encapsulation – the complete surrounding of an electronic component or complex of components with a coating of an insulative material. The purpose is to protect the component from adverse environmental conditions.

Extrusion rate – a measurement of the flow capabilities of a material by dispensing through a narrow orifice under pressure and measuring the grams per minute.   Typically tested at 60 or 90 PSI and through a 1/8 orifice.

Fast cure – an order of magnitude faster than typical – Most R.T. cures are slow

Filler – a finely divided powder formulated into a composition to either enhance physical properties or reduce the overall cost of the composition.

FIP – form in place gasketing, RTV’s are applied wet, conforming perfectly to the gap upon mating excess sealants pushed-out.  The wet sealant then cures forming a gasket.  The gasket seals the two flanges by adhering to each exposed part.

Firm time - an old GE term, the time to obtain 40 Shore A min. in an 2-part tin catalyzed system

Flash point – the temperature that an materials vapors will ignite when it is exposed to an ignition source.

Flowable – a material that is in a liquid state at room temperature and will fill all of the voids in the container into which it is poured.

Fluid – typically defined as a material that will take the shape of any vessel containing it.  However, in silicone technology it also refers to a non-functional silicone PDMS polymer of low viscosity whose terminal groups will be trimethyl.  A fluid is the opposite of a resin, which is functional and can be crosslinked.   Repeating groups on the polymer backbone can be of a wide variety.

Fluorosilicone – a silicone PDMS material with varying levels of trifluoropropyl functionality along the backbone chain.  They can be either functional or non-functional.

Foam – a silicone rubber containing many gas pockets formed during cure, creating a cellular structure.  These voids can be caused from the release of hydrogen gas or a blowing agent, often thermally activated.

Freshening – the milling or working of an uncured silicone to break hydrogen bonds and enable better processability.

Fumed silica – a very fine silicon dioxide, typically formed through the pyrolysis/flame hydrolysis of silanes.

Functionalization – the complexing or chemical reaction of a pendant group with a reactive species, often silanes, which results in a change in activity or potential.

Gel – a soft, compliant, lightly crosslinked silicone elastomer.  Some display a semi solid-form.

Gel time – The period of time from initial mixing of flowable reactants in which the material becomes too viscous to flow or be tooled caused by crosslinking to a pre-cure elastomeric state.

Glass transition temperature, Tg – the temperature where a brittle solid will soften to a liquid, gel, or if an elastomer, start to display elastomeric behavior.

Grease – lubricating products made by thickening fluids with suitable fillers.

Green strength – a resistance to be displaced while in an uncured state found in some sealants, useful in assembly applications.

Gum – a very viscous polymer sometimes filled with silicas used as a base for rubber compounding.  Viscosity is often > 1,000,000 cps.

Hardness – Shore A – a scale of measurement used to define the relative hardness of materials.

HAV – hot air vulcanization, typically refers to either the curing technique or the actual ovens used to cure elastomers.  The ovens can be vertical or horizontal.

HCE – stands for high consistency elastomer, or heat cure elastomer.  An older term, which is less utilized today.

HCR – heat cured rubber or high consistency (silicone) rubber.  Crosslinkable with heat, HCR is typically molded with very high pressures.  Often highly filled, the very thixotropic silicone rubber appears to be a solid in an uncured state.  Also called a HCE, heat cured elastomer.

HDPE – stands for high density polyethylene.

Headspace – the unfilled portion of a container that is occupied by a gas.

Heat cured – 1 or 2 part product that typically crosslinks into a hard, cured product upon exposure to heat

Heavy-bodied – an uncured polymer exhibiting a very high green strength or blow-out resistance in a assembly test condition.

Heat cure – a reaction where external heat is applied to either accelerate or initiate a chemical crosslinking to result in a desired end product.

Heat sink – the ability to rapidly transmit heat from a generating component.

Hidden silanols – silanols that are hidden inside of the particle not deactivated in a treatment process.

HMDZ – is an industry shorthand term for hexamethyldisilazane, a very hygroscopic water scavenger and treatment agent.

Humidity – the amount of water vapor present in the air at a given time and place.

Hydrolysis – the reaction of a reactive species like a silane with water generating a by-product.

Hydrolyzable – a reactive species like a silane that will rapidly react with a water or a silanol functionality.

Hydrosilation – a chemical reaction in which a vinyl functional polymer will crosslink with a hydrofunctional polymer.

Hydrolytic stability – the degree of relative resistance to attack of a material by water or water vapor.

Hydrophillic / Hydrophillicity – is a high affinity or attraction to water.

Hydrophobic / Hydrophobicity – is a repulsion of a material to water.

Hygroscopic – is the capacity in which a material will absorb or retain water.

Inhibitor / Inhibition – a volatile reagent intentionally added to a batch, used to delay curing and control open time or work time.  Typically evaporated during heat curing.

Instant cure – a rapid room temperature or heat accelerated room temperature cure, usually within 1 minute.

Insulate – to prevent the passage of an electrical current by imposing a barrier substance in the path of the current.

Joint movement – is the movement of two rigid structures within an assembly.  It can be caused from differential thermal expansion rates, vibration, shock or other means.  Also defined as the ability of a sealant to conform to these movements through high flexibility and maintain a bond.

Killed polymerization – the cessation of a polymerization due to deactivation of the catalyst and/or introduction of a chain stopper.

Lamination – is fully enclosing an adhesive between two sheets, disallowing exposure of the surface, preventing off gas and surface cure. Condensation cured silicones require exposure to air for full cure and cannot be used in a lamination application.

LDPE – low density polyethylene, can allow moisture to permeate in the gas phase.

Ligand – is a pendant organic component of a molecule.

LMW – low molecular weight

LSR – liquid silicone rubber.  Actually it’s a misnomer, the products are mostly of a thick paste consistency.  It’s a pumpable, moldable and heat curable silicone composition.  Also called LIM, liquid injection molding (grade).

Masterbatch – various additives or pigments are pre-dispersed into PDMS liquids to allow ease of addition to batches in production.

Mechanical adhesion – the interlocking of a uncured elastomer with the surface irregularities, which upon curing results in a secure bond.

MeH – industry shorthand term for a methyl hydrogen copolymer.  The crosslinker utilized in addition cured platinum catalyzed reactions.  The hydrogen functionality can be pendent interchain, on the chain terminus, or both.

Methyl – a central carbon surrounded by three hydrogens, a typical non-functional pendant group on a PDMS molecule, typically written as CH₃.

Micron – 1 x 10^-6 meter

Modulus – see Youngs and Bulk Modulus – the amount of force or energy that can be absorbed by a rubber specimen.

Monomer – an elementary molecule capable of being polymerized into a polymer.

MQ resin – a silicone macromolecule if functionalized, it will have a multitude of crosslink sites.  When used properly in silicone elastomers, provides regions of high crosslink density.

Mudcracking – is the surface cracking of a sealant or coating during cure.  Caused from poor formulation, weak surface, or high joint movement during cure.

Nanometer – one millionth of a meter

Neutral cure – a condensation cure system that liberates no corrosive (to metals) by-products upon curing. Alkoxy/Alcohol cure systems are neutral cure.

Oil resistance the ability of an elastomer to survive and display minimal changes in a long-term oil immersion condition. 

One-part – is a ready-to-use silicone material that does not require mixing with a catalyst or other additive to form a durable rubber or adhesive.

Open time – typically defined as the time that a compound takes to double in viscosity after catalyzation.  Some define it as how long a product will flow, enable tooling or application into the assembly.

Outgassing – the release of gaseous components from a product often accompanying a curing product by-product release or evaporation of low molecular weight components.

Oxime cure system – a tin catalyzed moisture cure system, which liberates an alcohol methylethyl ketoxime byproduct upon curing. This byproduct smells like latex paint.

Parts – (per hundred) is a rubber industry term depicting formulation components utilization in a formula in a amount relative to the resin (base polymer) depicted as 100 parts

PDMS – polydimethyl siloxanes (see siloxane)

Peel strength– an adhesion test measuring both the adhesion to the substrate, and the cohesive forces found within a cured rubber.  It is measured in pounds per linear inch, PLI, and percent cohesive and adhesive failure.  The test is characterized in ASTM D-794.

Peelable – displaying no adhesion for easy removal

Peroxide – a thermally decomposing agent added to silicone products to result in a free radical addition cure.  These free radicals create reactive species from non-reactive groups.  These reactive groups then form crosslinks during the curing of the compound.  Both vinyl specific and general-purpose peroxides are used.  Following this crosslinking route, by-products are generated which must be removed, via post-baking.

Peroxide cure – an addition reaction in which free radicals create reactive sites and form crosslinks.

Phenyl – a pendant fully conjugated benzene ring functionality on a PDMS molecule, typically written as C₆H₅.

Plasticizers – is typically non-functional diluents enabling a lower viscosity, or a more desired plasticity.  In methyl silicones typically trimethyl terminated PDMS.

Platinum cure – an addition reaction between a hydride functional PDMS with a vinyl functional PDMS, which is catalyzed by a platinum salt, typically chloroplatinic acid.

Poisons/poisoning – an industry term that identifies a list of materials (non-toxic) that can complex and or deactivate a platinum catalyst.  ie. sulfur, amines, etc.

Polydispersity – a characteristic of polymer where it is composed of multiple polymer molecular weight/chain lengths.  It is contrary to a unimodal polymer.

Polymerization – a series of chemical reactions with oligomers, which result in long chains of repeated units being formed.

Porosity – the presence of void or air pockets in a cured composition.

Post baking / post cure – the exposure of a crosslinked material component after the initial heated cure to elevated temperatures in an effort to improve the mechanical properties or evaporate undesirable volatile components. 

Pot life – the amount of time available between the moment that a catalyst is stirred into a base material and the approximate moment that it becomes too thick to apply in the recommended manner.

Potting material – an electrically insulative, moisture resistant material, supplied in a liquid or putty-like form and used as a protective coating on sensitive areas of electrical and electronic equipment.

Pourable – is a self-leveling composition that can be easily dispensed from a package as a liquid.

Precipitated silica – is wet process silica formed through the reaction of sodium silicate and sulfuric acid.  Typically can contain up to 7% water.

Primer – a organo-functional silane in a multi-solvent solution.  Upon application to a substrate, a silanol rich surface remains, rendering the surface highly prone to adhesion reactions.

PSA- pressure sensitive adhesive, typically supplied in a dispersion.  Upon evaporation of the carrier, a permanently tacky, gel-like adhesive results that sticks to substrates through a light pressure application, like applying a label.  The common label and sticker backings are PSA’s.

Quenching – is the secondary addition of a crosslinker, often with an adhesion promoter targeted at providing an enhanced shelf-stability potential.

Reinforcement – is adding to the strength of an elastomer system.  This is typically accomplished by adding reinforcing fillers and resins.

Rheology – the study of the deformation and flow of materials, in terms of stress, strain and time.

Resin – a polymeric material often of a high molecular weight and flowable, utilized as a base raw material in elastomeric compositions.  It is often a crystalline material in a solvent carrier.

Reversion – a de-polymerization of a cured silicone rubber into its original polymeric components.

R.T. – room temperature cure

R.T.V. – room temperature vulcanization (curing without heat)

RTV-1 – a 1-part RTV system.  No mixing, ready to use.

RTV-2 – a 2-part RTV system.  The mixing of the two components is required prior to use.

Sag resistance – a test that measures the resistance to flow of a one-inch plug of uncured sealant after being placed on a vertical plane.

Scavenged /scavenger – the chemical reactions of silanes or MeH with silica silanols, water or other functionalities rendering them less reactive.

Scorch – a cure speed that exceeds the design of the targeted utilization.  Curing too fast at a given temperature to fully fill mold cavities.

Self-leveling – a high flow, syrup-like condition, unlike thixotropic

Shawningan black – a carbon black manufactured from a natural gas stream that is free from sulfur contamination.  Typically used in platinum catalyzed addition cure systems.

Shear – the introduction of energy into matter via applied displacement force and or restriction of flow.

Shelf-life – the period of time that a packaged product is useable.

Silane – A highly reactive molecule having a Silicon atom as the central unit.  Outside of their main utilization to produce monomers or silica, in silicones they are typically functionalized and used as crosslinkers and adhesion promoters.

Silbond ™ 40 – a 40% hydrolyzed tetraethoxy silane, typically used as a primer, hydrophobizing agent and adhesion promoter.

Silica – silicon dioxide in a finely divided powder form.  Can be generated from quartz, precipitated from sodium silicate or created via flame hydrolysis of certain silanes. 

Silicate – a salt of silicic acid

Silicone plasticizers – trimethyl terminated siloxane fluid having no functionality that cannot crosslink without the use of peroxides.

Silicone rubber – a crosslinked silicone polymer.  It maintains its elasticity and electrical properties over a wide range of temperatures and is widely found in sealants, gaskets, insulation, tapes, etc.

Silanol – a Si-OH functionality.  It can be found in a silica, glass and silicone polymers.

Siloxane fluids – polymers having a regular alternating silicon and oxygen central atoms, typically having pendant dimethyl functionality.  These polymers can be functionalized interchain and at chain terminus for a wide range of applications.

Silsequioxane – a ladder polymer, which can provide reinforcement in compositions.

Simethicone – trimethyl terminated siloxane fluid, also called dimethicone by non-silicone industry formulators.  Found in skin and anti-flatulence preparations.

Skin-over – the formation of an integral skin over the surface of a quantity of sealant.

Softening – reducing the viscosity of a compound by shearing which breaks hydrogen bonds.  Freshening is required of HCR on 2-roll mills prior to processing.

Solubility – the ability of a substance to dissolve in a solvent.

Solvent – a material that has the ability to dissolve of other materials.

Specific gravity – is the ratio of the weight of any volume of a material to the weight of an equal volume of water.

Specific heat - the quantity of heat required to raise the temperature of one gram of a substance to one degree centigrade at 15^oC.

Starved – a condition where a insufficient level of crosslinker or adhesion promoters exist in the uncured silicone composition.  This results in very high product viscosities and or very slow to incomplete curing capabilities.

Stoichiometry – is the chemical balance of reactants in a reaction.  Ideally one mole of A will fully react with one mole of B.

Substrate – a materials surface in which an adhesive or other agent is in contact with and acted upon.

Surface inhibition of cure – contamination of a platinum cured product by “poisons” found on a substrate, or oxygen inhibition of a peroxide cured system.

Surface tension – is an effect of the forces of attraction existing between molecules of a substance.  These forces are only exerted on the surface layers.

Surface wetting – is the full surface contact of a substrate by an adhesive or coating.

Tack-free time – the time it takes for a sealant to cure to a point where none of the applied material will stick to your finger, a spatula or a plastic weighted film.

Tear strength – the resistance to the propagation of a nick or cut in a test piece when tension is applied. Given in pounds per inch (ppi), Newton per millimeter (N/mm) or (kN/m) kilo Newton per meter.

Tg – see glass transition temperature

Tensile strength (tensile at break) – the amount of force required to break a test piece. Given in pounds per square inch (PSI), mega Pascals (MPa), or Newton per square millimeter (N/mm2).

Thermal conductivity – the speed with which a material is capable of transferring a given amount of heat through itself.

Two-part – is a dual component A & B silicone material product, which must be mixed together to enable curing to form a durable rubber.

Thixotrope – an additive that imparts thixotropy to a composition generally enabling hydrogen bonding to occur.

Thixotropic – is a non-slump or sag property, resulting in no flow without pressure.  Having high static shear strength and low dynamic shear strength, the material exhibits a highly predictable time-dependant loss of viscosity when exposed to shear. Viscosity decreases under steady shearing then slowly rebuilds.  This is caused by Hydrogen bonds breaking and reforming.

Treated – a chemical coating applied to fillers to hydrophobize and enable enhanced processing capabilities.

Ultraviolet (UV) cure – is the process of curing resins and adhesives with high intensity UV light.  Through the use of photoinitiators and certain functionalized polymers, this is made possible.

Uncured – a silicone material, which has not yet vulcanized or formed a durable rubber.

Unimodal – a polymer having a uniform molecular weight within a very narrow range.

Untreated silica – is silica filler that has no surface treatment and typically has a high surface silanol content.

Vinyl – is an unsaturated, two-carbon pendant functional group containing a double bond and capable of crossliking with an adjacent hydride functional PDMS.

Viscosity – a relative measurement, it’s the viscous property of a fluid as measured by shear stress divided by shear rate. Usually considered to be the relative thickness or thinness of a fluid as compared to the thickness (thinness) of water.  Any viscosity value can be changed, by modifying the test conditions of shear stress or shear rate.

VOC’s – volatile organic content, any evaporative component or by-product released from a material.  Measured in grams per liter.

Volatile – a liquid that changes rapidly into a vapor when exposed to air, heat, or both.

Volatiles – low molecular weight un-reacted silicone materials from polymerization.  Found in certain silicone polymers, these materials that can become airborne and create appearance and performance problems.

Volume expansion – a measurement of the increase in bulk or space occupied by a material in relation to an increase in temperature.

Volume swell – the amount of increase in volume of an elastomer after exposure to an aggressive condition.  Typically identified in liquid immersion testing.  Caused by the polymer dissipating stress via coil chains unwinding and expanding in size three dimensionally.

Youngs modulus – the amount of force per square inch to stretch a test piece to a given elongation. Typically measured @ 50, 100 or 200% elongation.  ASTM D-412 test method is typically utilized.

Yield stress – yield point or flow limit is identified as the pressure applied to a sample where plastic flow of a thixotropic material starts.

Vulcanization – the curing/crossliking of a rubber composition.

Weep – is a permeability of a seal or gasket to a sealed media resulting in a wicking behavior.

Weight loss – the loss of volatile materials removed from a substance after being subjected to heat, vacuum or both.

Wettability – the ability of a substrate to attract another substance based on the relative surface tensions between the two materials, or the surface finish.

Wet-out – is to fully impregnate the surface irregularities of a substrate with an adhesive.  This is accomplished either with an appropriate low viscosity or surface energy of an adhesive or with adequate application forces.

Work time/life – the usability time of the product after catalyzation is measured here.  Often identified as how long up until a product will flow, enable tooling or application into the assembly.  Also known as work life, pot life or gel time.

Yield point – a stress that needs to be applied to a material prior to any plastic deformation or flow to occur.  With thixotropic materials, the reduction of thick phase will only be resultant upon a force or stress being applied.  The yield point identifies the minimum level of stress or force that is required to apply to attain flow. 

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