Properties of waterborne polyurethane films: effects of blend formulation with hydroxyl telechelic natural rubber and modified rubber seed oils

A series of new waterborne polyurethanes (WPUs) was successfully prepared by the prepolymer process from the bio-renewable sources hydroxytelechelic natural rubber (HTNR with MW 3000 g mol^?1) and hydroxylated rubber seed oil (HRSO), with DMPA fixed at 5.6 wt%. The effects of ratio of HTNR and HRSO (ranging from 1.00/0 to 0.10/0.90) and of hydroxyl value (OHV) of HRSO (200 or 270 mgKOH/g) on final properties were studied. It was found that the particle size of WPU increased significantly with both HRSO/HTNR ratio and OHV of HRSO. Chemical structure of the WPU films was confirmed by FT-IR. The water uptake, mechanical, dynamic mechanical properties and thermal stability of WPU film improved with both HRSO content and OHV of HRSO, while swelling in THF decreased. All these WPU films had similar Tg. This article reports novel green biobased WPU with promising applications as adhesive for shoe industries.

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Modified rubber seed oil based polyurethane foams

In this work, rubber seed oil (RSO) was extracted with cyclohexane at room temperature for 24 h. The yield of RSO was about 40 %. The RSO was purified by using sodium hydroxide to eliminate some free fatty acids. Then the RSO was modified by simultaneous epoxidation and hydroxylation. Hydroxylated RSO (HRSO) had the hydroxylation extents 120 and 230 mgKOH/g with 2 h and 4 h reaction times, respectively. The chemical structures of the oils were studied by FT-IR and ¹H-NMR, and they were characterized also in other ways. Polyurethane foam samples based on the HRSOs were successfully prepared, and their physico-mechanical and thermal properties were also studied, with varied NCO index and water content in the formulations. The PUF230 had better thermal stability and compressive strength but lower density than the PUF120. Both the NCO index and the water content had large effects on density, cell size, and compressive strength of the polyurethane foams.     

Synthesis,characteristic, and properties of waterborne polyurethane based on natural rubber

A series of new waterborne polyurethanes (WPUs) was successfully prepared by prepolymer process from renewable source, hydroxytelechelic natural rubber (HTNR), with different amounts of DMPA (1.6–8.4 wt %), different molecular weights (1000–4000 g mol^?1), and different levels of epoxide (0%–20%) of HTNR. It was found that the urethane conversions of prepolymer were over 80% as calculated by FTIR technique. The resulting HTNR2000‐based WPUs exhibit a uniform particle size, which decreases from 420‐ to 83‐nm diameters with an increase in the amount of DMPA from 2.9 to 6.6 wt %. The particle size also decreases with an increase of soft segment or with an increase of epoxide content. They are well stable more over 6 months and without a significant difference in particle size compared with starting of them. Chemical structure of WPU films was confirmed by FTIR, ¹H‐NMR, and ¹³C‐NMR. Molecular weight and polydispersity were determined by SEC. In addition, thermal and water uptake properties were investigated. The experimental results reveal that the DMPA content, molecular weight of HTNR, and epoxide content play an important key role in water uptake and thermal properties. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Interfacial Interactions of Silica and Natural Rubber Enhanced by Hydroxyl Telechelic Natural Rubber as Interfacial Modifier

The incompatibility between hydrophilic silica and hydrophobic rubber is an important problem on using silica in nonpolar rubber. In this study, hydroxyl telechelic natural rubber (HTNR) that contains hydroxyl‐terminated groups was introduced into silica‐reinforced natural rubber (NR) in order to improve the bonding strength between rubber and silica. The properties of silica‐reinforced NR compounds and vulcanizates as a function of varying silica contents were evaluated at a fixed HTNR concentration at 8% wt/wt of silica content. The results show that the improvement of silica dispersion and decreasing of filler–filler interactions (Payne effect) were obtained in the NR compounds and vulcanizates with HTNR addition. The enhancements in tensile properties, crosslink density, abrasion resistance, heat build‐up, and thermal properties of the silica‐reinforced NR vulcanizates with added HTNR confirmed that HTNR performed good as interfacial modifier of silica. In the study, the optimum properties of silica‐reinforced NR vulcanizate were achieved at 30 phr silica with 2.4 phr HTNR. However, HTNR still showed poorer efficiency than the synergy between commercial silane coupling agent, bis [3‐(triethoxysilyl) propyl] tetrasulphide (TESPT) and diphenylguanidine (DPG) when used in silica‐reinforced NR vulcanizate. J. VINYL ADDIT. TECHNOL., 26:291–303, 2020. © 2019 Society of Plastics Engineers     

The chain extender content and NCO/OH ratio flexibly tune the properties of natural rubber‐based waterborne polyurethanes

The effects of chain extender content (ethylene diamine, EDA) and NCO/OH ratio on the properties of natural rubber‐based waterborne polyurethanes (WPUs) were investigated experimentally. The particle size of WPU increased significantly with the NCO/OH ratio, in the presence of the EDA chain extender, while it was unaffected by the EDA content. The water uptake of WPU film increased with the EDA content, while the swelling in various solvents decreased. In a thermal analysis, the second decomposition stage of a WPU film increased with the EDA content and with the NCO/OH ratio that also positively affected the dynamic mechanical and mechanical properties. These factors in WPU films had no the effect on the T_g. The stress–strain curves clearly showed the change in WPU films from soft elastomeric materials to ductile and hard plastics. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42505.     

Influence of filler type and loading on cure characteristics and vulcanisate properties of SBR compounds with a novel mixed vulcanisation system

In the present work, the influences of filler type and content on cure characteristics, mechanical and dynamic mechanical properties, and heat aging resistance of filled styrene butadiene rubber (SBR) compounds cured with a mixed vulcanisation system were assessed. A new mixed curing system was developed to obtain vulcanisates with excellent mechanical properties and heat aging resistance compared to those with a commercial EV cure system. The results show that filler has stronger effect on scorch time, cure time and cure rate index with the EV system than with the mixed curing system. The torque difference of filled SBR compounds depends on the filler content. With mixed vulcanisation, it is easier to control the conditions during moulding when the formulation is altered, particularly with a change in filler content. The mixed vulcanisation gave overall improved mechanical properties, heat build-up and heat aging resistance compared to the EV system, even though reinforcing fillers were used in the SBR compounds.     

Influence of accelerator/sulphur and co-agent/peroxide ratios in mixed vulcanisation systems on cure characteristics,mechanical properties and heat aging resistance of vulcanised SBR

The influence of accelerator/sulphur and co-agent/peroxide ratios on cure characteristic and vulcanisate properties in mixed vulcanisation of styrene butadiene rubber (SBR) was investigated in this work. Accelerator/sulphur ratio was investigated with three alternative sulphur curing systems, namely conventional, semi-efficient and efficient vulcanisation (EV) systems. Zinc dimethacrylate (ZDMA) was used as a co-agent to enhance the performance of peroxide and to provide ionic linkages. Ionic linkages contributed by ZDMA create bridges between two polymer chains. The ZDMA/peroxide ratio was varied from 2 to 10. The concentration of dicumyl peroxide was held fixed while the ZDMA content was varied. Cure characteristics, mechanical properties, dynamic mechanical properties and heat aging resistance were investigated in relation to the crosslink structure. Increasing the ZDMA/peroxide ratio significantly increased density of ionic linkages, especially in combination with the EV system. The combination of EV system with high ZDMA/peroxide ratio provided the highest ionic crosslink density and the lowest polysulphidic crosslink density: this enhanced the mechanical properties, the dynamic mechanical properties and the thermal stability of SBR vulcanisates.