Asphaltene-Stabilized Polyisobutylene Pressure-Sensitive Adhesives for Ultraviolet Protection and Surface Bonding

Abstract

The usual way to protect indoor areas from solar UV radiation is to use UV-absorbing materials, which are applied as a thin film on the surface of the windowpane. Asphaltenes are useless wastes from crude oil refining that absorb UV radiation well, which gave the idea of their use in protective coatings. Pressure-sensitive adhesives based on polyisobutylene containing from 5 to 30 wt% of asphaltenes were obtained. Deterioration of the adhesive properties with the introduction of 5-20 wt% of asphaltenes was shown by adhesion tests, which can be associated with the plasticization of the polymer matrix. At the same time, the use of 30 wt% of asphaltenes leads to the polymer matrix reinforcement with the restoration of adhesive properties to the original level or even slightly higher. The rheological study of adhesives at 25 °C and 120 °C showed the structural network formation by asphaltenes at a content of 30 wt%, explaining the increase in adhesion performance. According to microscopy, asphaltenes are flat brown glass shards in a polymer matrix. They absorb electromagnetic radiation, predominantly in the UV range, while maintaining relative translucency in the visible range. This makes it possible to obtain thin films from the asphaltene-filled adhesive for bonding glass sheets to produce UV-blocked and tinted windowpanes.

Keywords: UV protection; asphaltenes; glass bonding; polyisobutylene; pressure-sensitive adhesives; rheology.

Figure 1

The dependences of viscosity on shear stress for PIB, asphaltenes, and their blends at 120 °C. The concentration of asphaltenes is shown in the legend.

Figure 2

The frequency dependences of storage and loss moduli of PIB and its mixtures with different content of asphaltenes at 120 °C. The insert shows the same dependences but as Cole–Cole diagrams.

Figure 3

The temperature dependences of storage and loss moduli of PIB and its mixtures with different content of asphaltenes. The inset shows enlarged sections of the same curves, and the arrows indicate the points of equality of the storage and loss moduli.

Figure 4

The dependences of viscosity on shear stress for PIB and its mixtures containing a different mass fraction of asphaltenes at 25 °C.

Figure 5

The dependences of storage and loss moduli on angular frequency for PIB and its mixtures containing a different mass fraction of asphaltenes at 25 °C. The insert shows the same dependences but as Cole–Cole diagrams.

Figure 6

The dependences of steady-state viscosity and complex viscosity on, respectively, shear rate and angular frequency for PIB and its mixtures containing a different mass fraction of asphaltenes at 25 °C (the mainline figure) and 120 °C (the insert).

Figure 7

The dependences of storage and loss moduli on shear stress for PIB and its mixtures with different content of asphaltenes at an angular frequency of 6.28 rad/s and 25 °C. The insert shows the same results but as a function of strain.

Figure 8

Load–displacement curves for probe-tack tests of PIB and its mixtures containing a different mass fraction of asphaltenes at 25 °C. The insert demonstrates the dependences of the debonding energy and the apparent strength of adhesive joints on the asphaltene content.

Figure 9

The dependence of peel strength on the asphaltene content in adhesives.

Figure 10

The dependence of the transmittance on the wavelength of electromagnetic radiation for PIB, asphaltenes, and their mixtures. The mass fraction of asphaltenes is indicated at the curves.

Figure 11

Microphotographs of PIB containing 5 (A), 10 (B), 20 (C), or 30 (D) wt% of asphaltenes.