Characterization of biodegradable polymer blends of acetylated and hydroxypropylated sago starch and natural rubber.

Development of biodegradable polymers from absolute environmental friendly materials has attracted increasing research interest due to public awareness of waste disposal problems caused by low degradable conventional plastics. In this study, the potential of incorporating natural rubber latex (NRL) into chemically modified sago starch for the making biodegradable polymer blends was assessed. Native sago starch was acetylated and hydroxypropylated before gelatinization in preparing starch thermoplastic using glycerol. They were than casted with NRL into biopolymer films according to the ratios of 100.00/0.00, 99.75/1.25, 98.50/2.50, 95.00/5.00, 90.00/10.00 and 80.00/20.00 wt/wt, via solution spreading technique. Water absorption, thermal, mechanical, morphological and biodegradable properties of the product films were evaluated by differential scanning calorimetry (DSC), universal testing machine (UTM), scanning electron microscopy (SEM) and fourier transform infrared spectroscopy. Results showed that acetylation promoted the incorporating behavior of NRL in sago starch by demonstrating a good adhesion characteristic and giving a uniform, homogenous micro-structured surface under SEM observation. However, the thin biopolymer films did not exhibit any remarkable trend in their DSC thermal profile and UTM mechanical properties. The occurrence of NRL suppressed water adsorption capacity and delayed the biodegradability of the biopolymer films in the natural environment. Despite the depletion in water adsorption capacity, all of the product films degraded 50 % within 12 weeks. This study concluded that biopolymers with desirable properties could be formulated by choosing an appropriate casting ratio of the sago starch to NRL with suitable chemical substitution modes

NR/PP Thermoplastic Vulcanizates: Selection of Optimal Peroxide Type and Concentration in Relation to Mixing Conditions

Thermoplastic vulcanizates (TPVs) from natural rubber (NR) and polypropylene (PP) were studied, prepared by dynamic vulcanization during melt mixing, using various peroxides to crosslink the rubber phase. The objective was to find a proper balance between degree of crosslinking of the rubber and degradation of the PP-phase, and the tendency of the peroxide to form smelly by-products, in particular acetophenone. Four types of peroxides were investigated: 2,5-dimethyl-2,5-di(tert-butyl-peroxy) hexyne-3 (DTBPHY), 2,5-dimethyl-2,5-di(tert-butyl-peroxy) hexane (DTBPH), di(tert-butylperoxyisopropyl) benzene (DTBPIB), and dicumyl peroxide (DCP), at two mixing temperatures: 160 and 180°C for a 60/40 NR/PP TPV. The maximum and final mixing torques are clearly related to the intrinsic decomposition temperature of the particular peroxide used, where DCP and DTBPIB turn out to be effective at 160°C, whereas the other two require a higher temperature of 180°C. The best mechanical properties, tensile strength, elongation at break and compression set are obtained at lower mixing temperature with DCP and DTBPIB, presumably due to less degradation of the NR and PP. Unfortunately, these two peroxides form more smelly by-products than DTBPHY and DTBPH. Dependent on the requirements of the pertinent application, a balanced selection needs to be made between the various factors involved to obtain an optimal product performance of these NR/PP TPVs

Effect of Ground Tyre Rubber Devulcanisates on the Properties of a Passenger Car Tyre Tread Formulation

Extensive research on recycling processes, in particular for waste tyre material, is necessary due to increasing raw material costs, diminishing resources and growing awareness of environmental issues. One of the preferred methods is devulcanisation, in which only sulphur cross-links are broken, while the polymer chains remain intact. In this study, optimised processing conditions for the devulcanisation of whole passenger car tyres using diphenyldisulphide (DPDS) as a devulcanisation aid were applied. The devulcanised ground tyre rubber (D-GTR) obtained from the process was blended on top of the original tyre tread formulation at different concentrations. The cure characteristics and mechanical properties of the re-vulcanised blends are evaluated in comparison to the original compound. The results so far indicate that the addition of D-GTR influences the properties of the blend, but to a lesser extent than the commercially used powder or reclaim types do, for which loadings less than 5% can be applied. The main reason for the influence of D-GTR on the rubber properties is inhomogeneities in the D-GTR/virgin rubber blen