Investigation of Field Performance and Film Properties of Natural Rubber Latex Preserved with a Novel Chemical

The traditional long-term preservative system of latex has an impact on environmental air pollution by ammonia and leads to the production of carcinogenic nitrosamine substances by tetramethyl thiuram disulfide (TMTD). In this research, ammonia and a novel preservative with a polysulfidic link were compounded and tested as a novel traditional long-term latex preservative system, to overcome the drawbacks of traditional preservative systems. Control samples were prepared with ammonia as the standard preservative. In addition, ammonia and the novel chemical mixed samples were also prepared for investigating the combined effect. After the preservation treatment, the stable nature of field NR latex was evaluated via the Volatile Fatty Acid (VFA) test based on ASTM D 1076 standard. The Dry Rubber Content (DRC) test and Total Solid Content (TSC) test were carried out for VFA calculation purposes based on ISO126:2005 and ASTM D 1076 standards, respectively. The alkalinity test was carried out to maintain the required ammonia content in latex. In the first trial, traditional dispersion preparation of novel chemical dispersion failed due to the large particle size of the novel chemical. Therefore, two different novel chemical dispersions were prepared in the second trial, where dispersions 1 and 2 were prepared with wetting agents and without using a wetting agent, respectively. It was found that 0.020%v/v and 0.025% v/v concentrations of the novel chemical from dispersion 1 allowed the preservation of field NR latex for 8 days. A low concentration (0.015% v/v) of the novel chemical was able to keep latex with good stability for 5 days. The novel chemical dispersion without a wetting agent exhibited a marvelous preservative system to NR latex than with a wetting agent, because the wetting agent creates a barrier between particles of novel chemical and latex particles. The novel preservative acts as a good preservative while reducing the fumes of ammonia being emitted and eliminating the carcinogenic nitrosamine emission from TMTD

Microbial activity in natural rubber latex with currently existing preservative systems

Natural rubber latex is sterile within the tree and destabilizes within a few hours after tapping due to heavy microbial contamination. The main sources of contamination are the tree laces, tapping panel barks and cup which receives the latex. The work described is a systematic study on the behavior of microflora in Hevea latex with different preservative systems in order to investigate the reasons for latex quality deterioration even after the preservation with currently used preservative systems.   Observations were made on microbes present in natural rubber (NR) latex without adding any preservatives, latex preserved with LATZ (low ammonia, TMTD/ZnO and latex preserved with high ammonia (0.7%) (w/w). These samples were cultured in modified Klingers Iron Agar (KIA) at room temperature for 36 hours. The morphology of colonies was observed visually. Gram staining was done after preparation of heat fixed smear. Above colonies were further purified by streak plate technique and subjected to biochemical tests like acid fast, catalase and glucose fermentative activity.   According to Bergey’s manual of determinative bacteriology and results obtained from biochemical tests, the main types of bacterial species identified are Bacillus polymixa, Bacillus subtilis, Bacillus coagulans, Lactobacillus casei, Lactobacillus fermenti and Cocci species. The media used to culture the bacteria consist of Bromocresol purple which turns yellow with acid producing bacteria and turn pink with non-acid producing bacteria. Observing the colour around the colonies revealed that only some bacteria produce acids even with high concentration of ammonia (i.e. 0.7% (w/w)), but they do not produce acids when the latex is preserved with LATZ. These results showed that ammonia resistant bacteria can be controlled using secondary preservatives.   The results permit to understand the microbial activity in sterile and preserved natural rubber latex and can be used to select effective preservative system instead of currently used systems

Improvement of cure characteristics and physical properties of EPDM by incorporating skim rubber

Ethylene-propylene-diene rubber (EPDM) consisting of ethylene, propylene and an unsaturated diene is one of the synthetic rubbers for which the demand is rising fast. Owing to its non-polar and saturated backbone structure, EPDM exhibits good resistance to heat, oxidation and to polar solvents. They are good insulators for electricity as well.  Such properties have extended its application to rubber components used in automotive industry, building and construction industry and in wire and cable industries. It is reported that   modification of polyisoprene with a small amount of petroleum-processing products containing constituents similar to those of the albuminous fragments in NR will change the curing characteristics and physical properties of synthetic polyisoprene to the level of NR. Furthermore, skim rubber is used for increasing the rate of vulcanization of SBR due to the presence of higher amounts of non-rubber ingredients in them, which are capable of acting as a co-accelerator and an activator for vulcanization. This study clearly shows that ingredients such as decomposed products of proteins and natural fatty acids present in skim rubber function as co-activators for the vulcanization of EPDM. In this experiment the two accelerator systems namely tetramethylthiurandisulfide (TMTD)/2-mercaptobenzothiozole (MBT)  and TMTD/N-tert-butyl-2-benzothiazylsulfenamide (TBBS) were used to cure EPDM compounds   incorporated with varying amounts of skim rubber, ranging from 5 phr to 15 phr as an additive in the formulation.The improvement of cure charateristics in the presence of skim rubber as an additive was studied using Oscillating Die Rheometer, in the presence of both accelerator systems. The significant improvement of optimum cure time was observed when the skim rubber quantity was gradually increased in the formulation. However scorch time reduced while increasing the quantity of skim rubber. Therefore, it can be concluded that the non-rubber ingredients present in skim rubber can act as co-activators for the vulcanization of EPDM. These co-activators function by a mechanism similar to the mechanism of action of stearic acid in conventional vulcanization systems containing zinc oxide.Mechanical properties such as tensile strength, 100% and 300% modulus, hardness and rebound resilience were studied for the prepared compounds. It can be concluded that the optimum amount of skim rubber needed to be incorporated for the improvement of cure characteristics and mechanical properties of EPDM is around 5 phr. Results obtained further revealed that the optimized action of these co-activators present in skim rubber is achievable with the TMTD/TBBS accelerator system than with the TMTD/MBT accelerator system

Effects of a lifestyle intervention programme after 1 year of follow-up among South Asians at high risk of type 2 diabetes:a cluster randomised controlled trial

Abstract Introduction: South Asians are at high risk of type 2 diabetes (T2D). We assessed whether intensive family-based lifestyle intervention leads to significant weight loss, improved glycaemia and blood pressure in adults at elevated risk for T2D. Methods: This cluster randomised controlled trial (iHealth-T2D) was conducted at 120 locations across India, Pakistan, Sri Lanka and the UK. We included 3684 South Asian men and women, aged 40–70 years, without T2D but with raised haemoglobin A1c (HbA1c) and/or waist circumference. Participants were randomly allocated either to the family-based lifestyle intervention or control group by location clusters. Participants in the intervention received 9 visits and 13 telephone contacts by community health workers over 1-year period, and the control group received usual care. Reductions in weight (aim >7% reduction), waist circumference (aim ≥5 cm reduction), blood pressure and HbA1C at 12 months of follow-up were assessed. Our linear mixed-effects regression analysis was based on intention-to-treat principle and adjusted for age, sex and baseline values. Results: There were 1846 participants in the control and 1838 in the intervention group. Between baseline and 12 months, mean weight of participants in the intervention group reduced by 1.8 kg compared with 0.4 kg in the control group (adjusted mean difference −1.10 kg (95% CI −1.70 to −1.06), p<0.001). The adjusted mean difference for waist circumference was −1.9 cm (95% CI −2.5; to 1.3), p<0.001). No overall difference was observed for blood pressure or HbA1c. People who attended multiple intervention sessions had a dose-dependent effect on waist circumference, blood pressure and HbA1c, but not on weight. Conclusion: An intensive family-based lifestyle intervention adopting low-resource strategies led to effective reduction in weight and waist circumference at 12 months, which has potential long-term benefits for preventing T2D. A higher number of attended sessions increased the effect on waist circumference, blood pressure and HbA1c. Trial registration number: EudraCT: 2016-001350-18; ClinicalTrials.gov: NCT02949739