Preparation and characterization of modified telechelic natural rubber-based pressure-sensitive adhesive

Telechelic natural rubber (TNR) was prepared by the use of potassium persulfate and propanal at 70 °C and various degradation times from 0 to 30 h. These samples were then grafted by maleic anhydride (MA) in toluene solution before modification with 3-amino-1,2,4-triazole (ATA) to produce modified TNRs (AMTNRs). Attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) was used to identify the chemical compositions. Carboxyl and hydroxyl groups of TNRs were clearly observed, due to chain scission, oxidation, and modified chain ends. The viscosities of TNRs were dropped greatly after 5 h and then decreased slowly as a function of degradation time. ATR-FTIR spectra of AMTNRs showed amide bonds between ATA and MA groups, and then the multiple hydrogen bonding arrays were formed. The glass transition temperatures (T_g) of AMTNRs were determined by differential scanning calorimetry. The T_g of AMTNR_0 moved to a higher temperature of –55 °C after modification by ATA, confirming the formation of multiple hydrogen bonding arrays. However, the T_g of AMTNR_5 to AMTNR_30 decreased slightly due to chain scission in the degradation process. The adhesive properties of AMTNR-based pressure-sensitive adhesive were evaluated by a Lloyd adhesion tester. The tack of AMTNRs depended on wettability whereas peel and shear strengths were responded by a combination between wettability and multiple hydrogen bonding arrays.