影響膠粘劑粘接強度的化學(xué)因素
時(shí)間:2019-04-22 來(lái)源:http://whooo.net/ 發(fā)布人:昌盛機械
全自動(dòng)封膠機廠(chǎng)家提示大家,影響膠粘劑粘接強度的化學(xué)要素主要指分子的極性、分子量、分子外形(側基幾及大小)、分子量散布、分子的結晶性、分子對環(huán)境的穩定性(轉變溫度和降解)以及膠粘劑和被粘體中其它組份性質(zhì)PH值等。
The manufacturer of automatic sealing machine reminds us that the chemical factors affecting the bonding strength of adhesives mainly refer to the polarity, molecular weight, molecular shape (side group number and size), molecular weight dispersion, molecular crystallinity, molecular stability to the environment (transition temperature and degradation), and the properties of adhesives and other components in the adhesives, such as PH value.
1、極性。膠粘劑和被粘體分子的極性影響著(zhù)粘接強度,但并不意味著(zhù)這些分子極性的增加就一定會(huì )進(jìn)步粘接強度。從極性的角度動(dòng)身為了進(jìn)步粘接強度,與其改動(dòng)膠粘劑和被粘體全局部子的極性,還不如改動(dòng)界面區外表的極性。例如聚乙烯、聚丙烯、聚四氟乙烯經(jīng)等離子外表處置后,外表上產(chǎn)生了許多極性基團,如羥基、羰基或羧基等,從而顯著(zhù)地進(jìn)步了可粘接性。
1. Polarity. The polarity of adhesives and adhesives affects the bonding strength, but it does not mean that the increase of the polarity of these molecules will certainly improve the bonding strength. In order to improve the bonding strength, it is better to change the exterior polarity of the interface area than to change the polarity of the adhesive and the global part of the adhesives. For example, polyethylene, polypropylene and polytetrafluoroethylene (PTFE) have been treated by plasma. Many polar groups, such as hydroxyl, carbonyl or carboxyl groups, have been produced on the surface, which greatly improves the bondability.
2、分子量。聚合物的分子量(或聚合度)直接影響聚合物分子間的作用力,而分子間作用力的大小決議物質(zhì)的熔點(diǎn)和沸點(diǎn)的上下,決議聚合物的玻璃化轉變溫度Tg和熔點(diǎn)Tm。聚合物無(wú)論是作為膠粘劑還是作為被粘體,其分子量都影響著(zhù)粘接強度。
2. Molecular weight. Molecular weight (or degree of polymerization) of polymers directly affects the intermolecular forces of polymers, and the magnitude of intermolecular forces determines the melting point and boiling point of materials, and the glass transition temperature (Tg) and melting point (Tm) of polymers. Whether polymer is used as adhesives or as adhesives, its molecular weight affects the bonding strength.
3、側鏈。長(cháng)鏈分子上的側基是決議聚合物性質(zhì)的重要要素。從分子間作用力思索,聚合物支鏈的影響是,當支鏈小時(shí),增加支鏈長(cháng)度,降低分子間作用力。當支鏈到達一定長(cháng)度后,開(kāi)端結晶,增加支鏈長(cháng)度,進(jìn)步分子間作用力。這應當是降低或進(jìn)步粘接強度的緣由。
3. Side chain. The side groups on long chain molecules are important factors to determine the properties of polymers. Considering the intermolecular forces, the effect of polymer branched chains is to increase the length of branched chains and reduce the intermolecular forces when the branched chains are small. When the branched chain reaches a certain length, it begins to crystallize, increases the length of the branched chain, and improves the intermolecular force. This should be the reason for reducing or improving the bonding strength.
4、PH值。關(guān)于某些膠粘劑,其PH值與膠粘劑的適用期有較為親密的關(guān)系,影響到粘接強度和粘接壽命。普通強酸、強堿,特別是當酸堿對粘接資料有很大影響時(shí),對粘接常是有害的,特別是多孔的木材、紙張等纖維類(lèi)材更容易受影響。
4, pH value. As for some adhesives, their PH value has a close relationship with the application life of the adhesives, which affects the bonding strength and bonding life. Ordinary strong acid and alkali, especially when acid and alkali have a great impact on bonding data, are often harmful to bonding, especially porous wood, paper and other fibers are more vulnerable.
由于像熱固性的酚醛樹(shù)脂和脲醛樹(shù)脂的固化過(guò)程受PH值的影響很大,常常請求酸度較大。例如,固化時(shí)在酚醛樹(shù)脂中參加對甲苯磺酸或磷酸,在脲醛樹(shù)脂中參加氯化銨或鹽酸。因而,在不希望酸度大又要粘接的場(chǎng)所,選用中性的間苯酚甲醛樹(shù)脂是適合的。
Because the curing process of phenolic and urea-formaldehyde resins, such as thermosetting resins, is greatly affected by the PH value, the acidity is often requested. For example, p-toluene sulfonic acid or phosphoric acid is added to phenolic resin during curing, and ammonium chloride or hydrochloric acid is added to urea-formaldehyde resin. Therefore, it is suitable to use neutral m-phenol formaldehyde resin in places where acidity is not expected to be high and adhesion is required.
將木材外表預先用堿處置,普通可得到結實(shí)的接頭。但還必需留意膠層的PH值,它對膠層比對被膠接外表更有影響。
The wood appearance can be pre-treated with alkali, and generally a strong joint can be obtained. However, it is necessary to pay attention to the PH value of the adhesive layer, which has more influence on the surface of the adhesive layer than on the bonded surface.
5、填料。在膠粘劑中配合填料有如下作用:(1)增加膠粘劑的內聚強度;(2)調理黏度或工藝性(例如觸變性);(3)進(jìn)步耐熱性;(4)調整熱收縮系數或收縮性;(5)增大間隙的可填充性;(6)給予導電性;(7)降低價(jià)錢(qián);(8)改善其他性質(zhì)。
5. Filling. The fillers in the adhesives have the following functions: (1) increasing the cohesive strength of the adhesives; (2) adjusting the viscosity or technological properties (such as thixotropy); (3) improving the heat resistance; (4) adjusting the thermal shrinkage coefficient or shrinkage; (5) increasing the fillability of the gap; (6) giving conductivity; (7) reducing the price; (8) improving other properties.
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The wonderful content of this article is provided by automatic sealing machine. Hope to help you through the introduction of the edition, our official website is: http://linshi.jncsjx.com Thank you for reading and watching!
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