In the field of rubber and plastics, there is often a problem of adhesion between two materials, and for some materials with poor adhesion, it is usually necessary to do some treatment (such as adding adhesive resin, etc.) to increase its adhesion. Commonly used adhesive resins have four categories: rosin resin, terpene resin, phenolic resin and petroleum resin, different adhesive resins in the adhesion and temperature resistance and other properties are different, this issue for everyone to introduce the four major adhesive resin characteristics, and how to distinguish these four major adhesive resins through analysis.
1. Rosin resin
use:
It can be used in paints, desiccants, synthetic resins, automotive inks, floor tiles, rubber compounds, fluxes, solder pastes, and various adhesives and protective coatings.
status quo:
Rosin resin is easy to be oxidized and isomerized, most of the current rosin is modified, modified rosin are: hydrogenated rosin, polymerized rosin, dissociated rosin, rosin glycerides, rosin pentaerythritol esters and the like.
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How to distinguish between different rosins
Rosin contains partial dihydro and tetrahydro rosinic acid, rosin and hydrogenated rosin in FTIR are mainly manifested as the absorption of carboxylic acid bonds (1695cm-1, 1280cm-1) (Figures 1-1). The difference between rosin and hydrogenated rosin is that rosin has a series of peaks at 5-6 ppm in H-NMR, while hydrogenated rosin does not (Figure 1-2).
Fig. 1-1 FTIR of rosin
Fig. 1-2 H-NMR diagram of rosin and hydrogenated rosin
In FTIR, Malay rosin will show the peak information of maleic acid glycosides (1780, 1843cm-1) (Figure 1-3), which can be easily identified.
Fig. 1-3 FTIR of rosin and Malay rosin
Rosin pentaerythritol ester and rosin glycerides cannot be distinguished on FTIR, and it is difficult to distinguish between H-NMR, but careful observation has found that the peak of rosin pentaerythritol ester at 4.0-4.5ppm is mainly single-peaked, while the peak of rosin glycerides here is bimodal (Figure 1-4), which is distinguished.
Fig. 1-4 Rosin pentaerythritol ester and rosin glyceride H-NMR diagram
Second, terpene resin
peculiarity:
Terpene resin is processed from natural turpentine. It has good properties such as transparent, non-toxic, neutral, electrical insulation, hydrophobic, non-crystallization, dilute acid and alkali resistance, heat resistance, light resistance, aging resistance and strong adhesion, and has good compatibility with various synthetic substances, and is easily soluble in aromatic hydrocarbons and vegetable oils.
How to distinguish terpene resins
Terpene resins are more easily distinguishable than other resins, and there are split peaks of isopropyl absorption (1387cm-1, 1368cm-1) and peaks of isopropyl vibrations (1163cm-1) in FTIR (Figure 2-1).
Fig. 2-1 FTIR of terpene resin
3. Phenolic resin
Phenolic resins are compatible with a wide variety of organic and inorganic fillers and are an important bonding resin.
classify:
There are many varieties of phenolic resins, and phenolic resins are distinguished from phenolic resins, cresol-formaldehyde resins, resorcinol formaldehyde resins, etc. from the different combinations of phenolic raw materials. The main means are to distinguish judgments through infrared spectroscopy, nuclear magnetic spectrum, and lysis fragments.
How to distinguish phenolic resins
Industrially phenolic resin is a mixture of resin and sixth methyltetraamine (ulotile), the phenolic resin has an absorption peak at 3300cm-1, 1235cm-1 in the infrared spectrum of the phenolic resin, the aromatic ring has an absorption peak at 1620-1610, 1605-1580, 1515-1480 and 1470-1450cm-1, the phenol type 1,2,6-structural resin has a strong absorption at 755cm-1, and the infrared absorption of the ulotto has a strong absorption at 1014cm-1. 671 cm-1 (Figure 3-1).
FIG 3-1 FTIR of phenolic resin 2123
The obvious difference between phenol-formaldehyde resin and cresol-formaldehyde resin is significantly enhanced from the absorption peak at 2980-2920, and the extra-plane angular vibration of hydrogen atoms on the benzene ring of 862 is also extremely characteristic, and the absorption band near 1000 belongs to the hydroxymethyl vibration (Figure 3-2).
Fig. 3-2 FTIR of phenol-formaldehyde resin and cresol-formaldehyde resin
In phenolic epoxy resins, the type can be judged by observing the vibration of the epoxy ring (970, 912, 757) (Fig. 3-3).
Fig. 3-3 FTIR of phenolic epoxy resin
4. Petroleum resin
Petroleum resin is a thermoplastic resin produced by pretreatment, polymerization, distillation and other processes of C5 and C9 fractions produced by petroleum cracking, which is a oligomer with a molecular weight between 300-3000.
C5 Petroleum Resin Features:
Compared with natural resin tackifiers (rosin and terpene resins), C5 petroleum resins have the characteristics of high peeling adhesion strength, good fast adhesion, stable adhesion performance, moderate melt viscosity, good heat resistance, good compatibility with polymer matrix, and low price, and gradually replace natural resin tackifiers.
Figure 4-1 C5 petroleum resin structure
C9 Petroleum Resin Features:
C9 petroleum resin (also known as aromatic petroleum resin) is resistant to acids and alkalis, chemicals and water. Poor bonding performance, large brittleness, poor aging resistance, should not be used alone. It has good compatibility with phenolic resin, gumarone resin, terpene resin, SBR, SIS, but due to its large polarity, it has poor compatibility with non-polar polymers, is flammable and non-toxic.
Fig. 4-2 C9 petroleum resin structure
How to distinguish between C5 petroleum resin and C9 petroleum resin
C5 petroleum resin differs from C9 in solubility, and C5 petroleum resin is insoluble in acetone.
On the infrared spectrum (FTIR), C5 petroleum resin is mainly C-H peak (698, 761, 1376, 1455cm-1), C9 petroleum resin has a significant benzene ring peak (1603, 1586, 746, 702cm-1) (Figure 4-3).
Fig. 4-3 FTIR of C5 petroleum resin and C9 petroleum resin
On the nuclear magnetic spectrum (H-NMR), C5 petroleum resin is mainly C-H peak at 0.8-2.2ppm (Figure 4-4), while C9 petroleum resin in addition to the 0.8-3.0ppm C-H peak, there is also a peak of about 7ppm benzene ring (Figure 4-5).
Fig. 4-4 C5 H-NMR of petroleum resin
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