Crepe Rubber Research Articles

Social Sustainability of Raw Rubber Production: A Supply Chain Analysis under Sri Lankan Scenario

Raw rubber production is the sole foundation for the rubber product industry, rendering raw rubber to manufacture essential commodities to mankind, such as tires, condoms, surgical gloves, and so forth. Raw rubber production involves various stakeholders; however, literature focusing on the social impacts of the supply chains of raw rubber production has hereto been absent. Social life cycle assessment, a popular tool to assess the social impacts of a product or process and was deployed herein to assess the social profiles of three Sri Lankan raw rubber supply chains (crepe rubber, concentrated latex, and ribbed smoked sheets) in a cradle-to-gate manner. The Social Hotspots Database v4 on Sima Pro v9.3 was used for the analysis. Results indicated that Governance, Labour rights & decent work had been affected due to Corruption and Freedom of association & collective bargaining issues, mainly in Belarus and China. Proposed improvement options to address these touchpoints were found to be effective. If the importation of K-fertilizer shifted into countries with lower risks, such as Canada, Israel, and Lithuania, overall social risks associated with Corruption and Freedom of association & collective bargaining could be reduced by ca. 36% and 25%, respectively. As a result, social risks in the impact described above categories, i.e., Governance and Labor rights & decent work, were reduced by ca. 35–41% and ca. 17–20%, respectively. Managers may pay thorough attention to the hotspots identified herein in the first place and try to avoid them as much as possible. They may consider importation from the aforesaid low-risk countries while weighing the trade-offs with economic and environmental aspects.

Socio-economic Context of Rubber Growing in Non-traditional Rubber Cultivating Areas

Monaragala is one of the main non-traditional rubber cultivating areas in Sri Lanka, where majority of rubber is cultivated by smallholders. This is an attempt to identify the socio demographic characteristics, rubber cultivation characteristics, and rubber processing characteristic of smallholders in Monaragala district. The data used in this study were gathered through a field survey using a sample of 150 smallholders and the data were analyzed using descriptive statistics. The results of the survey showed that the knowledge of smallholders regarding rubber processing was around 70% and the processing standards was at a lower level. Majority of the smallholders are producing Ribbed Smoked Sheet (RSS) or sell raw field latex, which resembles that there is a potential to diversify the processing sector by introducing other processing techniques such as crepe rubber and technically specified rubber. Majority of the sample population which was around 63% were attracted towards high cost group processing centers than processing RSS at household level by using low-cost simple techniques such as using carpets for milling and chimney for smoke drying.

Social impact improving model based on a novel social life cycle assessment for raw rubber production: A case of a Sri Lankan rubber estate

Raw rubber production is the foundation of natural rubber product industry. Despite the various social issues (e.g., substandard working conditions) reported in raw rubber production, literature focusing on social impacts has been limited. Although social life cycle assessment (SLCA) has been a popular tool to assess the social impacts of a product or process, no any functional unit has so far been developed here due to the difficulty in linking the intangible social impacts to physical flows. Furthermore, the methodologies available in SLCA are insufficient for foreseeing the social benefits after addressing the social hotspots derived from a study. On this background, this study aimed at improving the social performances of raw rubber production using a novel SLCA method addressing the above said lacunas. The Stakeholder social impact (SSI) and Social impact categorical (SIC) indexes are salient components of this method as they quantify the social impact at stakeholders’ perspective and overall geopolitical perspective, referring to a functional unit, respectively. As a pilot study, this method was applied to a rubber estate in Sri Lanka where crepe rubber was produced. “Social benefits/security” and the “health and safety” of workers in the estate were identified as the most vulnerable factors affecting the rubber production. Further, the countermeasures proposed were found to be effective in improving these elements by 25% and 70%, respectively and overall social burden by ca. 12% as indicated by SIC index. Potential use of SSI index and SIC index at country level for benchmarking the overall social impacts and possible implications in adopting the methodology developed in other geographical areas and/or in other industries are discussed.

Kajian uji gelar aspal modifikasi berbasis karet padat jenis crepe rubber pada skala pilot

The COVID-19 pandemic that hit Indonesia had a significant impact on the industrial sector. One of them is the natural rubber industry which has experienced a decline due to export restrictions from natural rubber export destination countries. This has a direct impact on rubber farmers who suffer financial losses. The formation of a new natural rubber downstream industry for natural rubber modified asphalt is a solution to increase national rubber consumption without relying on exports. Therefore, the purpose of carrying out the asphalt title test based on natural rubber type crepe rubber is to evaluate technical feasibility and educate the public about using natural rubber for domestic needs. This service method consists of several stages: observing the absorption potential of natural rubber, analyzing technical feasibility, and evaluating the degree test of natural rubber modified asphalt. The degree test was carried out on the 10-meter road around the Faculty of Engineering, Riau University. The results of the degree test show that the modified asphalt raw material is based on crepe rubber, the asphalt sample marshall test that was held, and the core drill test meets the 2018 Highways standard. The degree test that has been carried out can educate the community and rubber farmers through APKARKUSI regarding natural rubber processing technology and compound making. Crepe rubber and the technology of making modified asphalt and applying modified asphalt for roads.

Effects of 1,2-Dihydro-2,2,4-Trimethyl-Quinoline (TMQ) Antioxidant on the Marshall Characteristics of Crepe Rubber Modified Asphalt

The use of natural rubber-like crepe rubber as an asphalt additive is very susceptible to aging. Aging on asphalt crepe rubber can occur during the mixing process or its use for the road. Studies on the prevention of aging on asphalt are still being developed to produce asphalt resistance to aging and have good performance in preventing deformation. Some studies that have been done are the addition of other additives such as antioxidants. This study aims to study the effect of adding crepe rubber and the antioxidant 1,2-dihydro-2,2,4-trimethyl-quinoline (TMQ) to the Marshall characteristics of rubber asphalt. Preparation of the rubber asphalt sample begins with making crepe rubber, which is by milling raw natural rubber in the form of a cup lump using a creeper. The crepe rubber product contains dry rubber content of more than 95%. Then the crepe rubber masticated using an open mill to soften and form it with 2 mm thickness. Then the crepe rubber is melted at 200 °C before being mixed with asphalt, heated to 165 °C. The crepe rubber content in the asphalt mixture is made 10%, and during the mixing process, the TMQ was added with contents of 0%, 1%, 2%, 3% w/w. The rubber asphalt samples were then tested for their penetration and marshall characteristics, using ASTM D5 and ASTM D6927 standards. The test results show that the addition of the TMQ can improve the penetration properties and stability of the rubber asphalt in holding the load. However, the addition of the TMQ of more than 2% causes a decrease in the rubber asphalt's stability properties. The best results were obtained by adding 2% TMQ with 68.7 dmm penetration and optimum asphalt content of 5.50%. Results of the marshall test for the sample are marshall stability 1403.96 kg, void filled aggregate (VFA) 75.90%, void in a mixture (VIM) 3.07%, void mineral aggregate (VMA) 15.34%, flow 3.370 mm, and marshall quotient (MQ) 420.8 kg/mm.

Pricing-to-Market and Exchange Rate Pass-Through in the Sri Lankan Crepe Rubber Export Markets

This article analyses the impact of the pricing-to-market (PTM) strategy on the Sri Lankan crepe rubber. The fluctuation in the value of the Sri Lankan rupees can alter the prices of exported goods in terms of foreign currencies. This affects the Sri Lankan products either to be more or less expensive to the foreign buyers and consequently, it effects on export demand. Hence, analyzing the effects of PTM is an important element in assessing the relationship of the exchange rates and export prices of tradable goods. Within and between models of panel regression was used to analyse the exchange-rate-pass -through (ERPT) of Sri Lankan crepe rubber in the world market. The within model was used to analyse the short-run pricing-to-market and the between model was used to analyse the long-run pricing-to market. Data of eight export market destinations spans from 2003 to 2014 were used in the analysis. Results indicated that the short-run pricing-to market is a strategically viable plan to expand the Sri Lankan crepe rubber market via exchange rate pass through.

The Effect of Addition of Antioxidant 1,2-dihydro-2,2,4-trimethyl-quinoline on Characteristics of Crepe Rubber Modified Asphalt in Short Term Aging and Long Term Aging Conditions

The use of natural rubber to resist bitumen is usually prone to degradation and aging. One method to overcome this problem is the addition of antioxidants. This study aims to determine the effect of the addition of antioxidants 1,2-dihydro-2,2,4-trimethyl-quinoline (TMQ) on natural rubber modified asphalt crepe rubber and its performance in short-term and long-term aging conditions. The modified rubber asphalt mixture’s manufacture begins by melting the crepe rubber at 200 °C before being mixed in asphalt at 165 °C. Addition of antioxidant TMQ during the stirring process of the mixture of asphalt and melted rubber. The crepe rubber content was 8, 10, and 12% w/w, while the TMQ content was 1, 2, and 3% w/w of the total sample weight. The modified asphalt samples’ characterization included penetration, softening point, weight loss after a rolling thin film oven test (RTFOT), penetration after RTFOT, and Marshall test. Review of the performance of asphalt under short-term aging conditions using a dynamic shear rheometer (DSR). Evaluation of asphalt performance under long-term aging conditions using Fourier-transform infrared spectroscopy (FTIR). The results showed that the fact that the best-modified asphalt product was the addition of 10% crepe rubber and 2% TMQ. The best-modified asphalt characteristics have penetration 68.70 dmm, softening point 55.45 °C, weight loss only 0.0579%, penetration after RTFOT 59.60, Marshall stability 1403.96 kg with optimum asphalt content of 5.50%, and rutting factor (G*/Sinδ) 6.91 kPa and 16.1 kPa before and after RTFOT. Overall, the modified crepe rubber asphalt can improve the performance of the asphalt in terms of durability. Simultaneously, the antioxidant TMQ works very well in increasing the resistance of bitumen to aging in the conditions of short-term aging and long-term aging.

Sustainability Assessment of Natural Rubber Primary Processing: A Review

Natural Rubber is an important commodity for the world due to its valuable properties such as good elasticity and renewable. Natural rubber is used to produce various important products such as tire, sport equipment, and medical devices. With increasing demand for these products, the demand of natural rubber is projected to jump in the future. To fulfil this demand, the increasing of natural rubber production is unavoidable. However, to use natural rubber in producing those final products, it needs to flow through primary processing such as crumb rubber manufacturing process, crepe rubber processing and latex centrifuge processing. These processes become source of income for countries such as Indonesia, Malaysia and Thailand as well as citizen of those countries. Despite of these positive impacts, the environmental impacts of natural rubber primary processing such as greenhouse gas emission, waste, high water and energy consumption are identified. Thus, to maintain sustainability, monitoring of sustainability impacts from natural rubber primary processing is necessary. Sustainability assessment is a procedure to evaluate sustainability impacts of products, process and policies. This paper aims to review sustainability assessment process applied in Natural Rubber Primary Processing.

Pengaturan Dosis Asap Cair Berbahan Baku Tempurung Kelapa Sebagai Bahan Penggumpal Lateks

In the processing of solid rubber, such as the manufacture of crumb rubber and rubber smoke sheet , o ne of the most important stages is the coagulation process using coagulant. The coagulation process is instrumental in determining for quality the rubber produced. Low quality of bokar is caused by farmers using coagulant which are not recommended. Because of that, it’s necessary to found the alternative coagulant that does not damage the quality and the price is relatively cheap. The purpose of this research is gets the best dosage of coconut shell liquid smoke for latex coagulation and to evaluate quality crepe rubber coagul um using coconut shell liquid smoke. The quality observed is dirt content, ash content, volatile matter, PRI, Mooney viscosity, and color index was implemented at PTPN VII , Way Berulu , Pesawaran District . The doses used were 0 , 1%, 1 , 5%, 2%, 2 , 5%, and 3%. The result showed that the most effective dose used in this research was 1% with quality approaching formic acid treatment. Keywords: coconut shell, formic acid, latex coagulant, liquid smoke

Reusing the generated sludge as Fe source in Fenton process for treating crepe rubber wastewater

Sludge recycling in Fenton oxidation was performed following the simplest procedure for studying the reaction phenomena and the role of Fe using methanol as the model compound and crepe rubber wastewater (CRWW) as the industrial application. CRWW is odorous and high in organics, nitrogen and phosphorus. Despite the capability of degrading hardly decomposable substances, large Fe3+ sludge production confines the useful application of Fenton oxidation. This sludge is hazardous due to residual organics adsorption from treated wastewater. Batch-mode experiments were performed at 25 °C and pH 2–3 for 24 h. After neutralization (adjusting pH > 9) and centrifugation, concentrated sludge was applied in the subsequent Fenton run as the Fe source. TOC reductions of 100% and 97% in conventional Fenton and 100% and 77% in sludge reuse systems were achieved for methanol and CRWW solutions, respectively, for initial COD:H2O2:Fe2+ mass ratio of 1:8:2 with effective reuse cycles. Fe in the sludge system behaved primarily as a heterogeneous catalyst, while dissolved Fe contributed to homogeneous catalytic reactions. Dissolved Fe2+ and total Fe were accumulated in sludge runs for enhancing the homogeneous process. Outcomes indicate that the simplest sludge reuse method experimented in this work can be effectively applied as an environmentally and economically promising method.

Financial and environmental sustainability in manufacturing of crepe rubber in terms of material flow analysis, material flow cost accounting and life cycle assessment

Abstract The natural rubber (NR) processing industry plays a critical role in the economies of many developing countries, particularly in Asia. Among the different types of NR, crepe rubber holds a significant position, as it is used to produce pharmaceutical and surgical rubber items, and also articles that are in contact with foods. At present, the crepe rubber manufacturing has been challenged by low productivity, rising cost of production, and environmental issues. Therefore, this study was aimed to assess the feasibility in the adoption of sustainable manufacturing practices in the crepe rubber production as a case study in Sri Lanka. This study consisted of three steps: 1) quantification of material and economic losses and global warming potential (GWP) via material flow analysis (MFA), material flow cost accounting (MFCA), and life cycle assessment (LCA) on a gate-to-gate basis, 2) developing proposals of improvement options with the help of Pareto and What-if analyses, field interviews, and the existing literature; and 3) validation of suggested improvement options through the re-execution of MFA, MFCA, and LCA. For 1 MT of rubber input, the underlying economic losses and GWP impact in the current manufacturing process were identified as LKR 19,585 and 279.3 kg CO2e with the values of 7% and 13% for Relative Standard Deviation, respectively. As improvement options, reduction options of water, chemicals, electricity, milling duration were proposed. It revealed that adoption of these reduction options could mainly reduce 32,064 kg of water and 30.1 kWh of electricity resulting in 5.3% of cost savings and a 4.3% of GWP impact reduction. Other implications associated with improvement options and their limitations are also discussed.

Sustainability of natural rubber processing can be improved: A case study with crepe rubber manufacturing in Sri Lanka

Rubber based products are essential commodities in the present day market. Natural rubber, being renewable with its unique qualities, plays a critical role in rubber product manufacture. Most natural rubber are produced in tropical Asian countries and their processing seems to be material- and energy-intensive hence challenged by cost-ineffectiveness and various environmental issues. Based on a case study of a Sri Lankan crepe rubber factory with a novel methodology, this study aimed at improving natural rubber processing sector to be more cost-efficient and eco-friendly. This methodology consisted of three phases: 1. quantification of factory’s resource use, economic loss, and greenhouse gas emissions using material flow analysis (MFA), material flow cost accounting (MFCA) and life cycle assessment (LCA), 2. developing proposals of viable improvement options, 3. benefit validation of the suggested improvement options for confident implementations. The results indicated that the economic losses and greenhouse gas emissions generated by processing 1 MT of dry rubber were LKR 18,151 and 254.2 kg CO2e, respectively. As improvement options, water, chemical, electricity reduction measures were proposed. Application of these options could reduce 45.59 MT of water and 542.8 kWh of electricity per 1 MT of dry rubber, resulting 26% and 79% drops in economic losses and greenhouse gas emissions, respectively. The findings and the research methodology reported here are significantly beneficial in introducing a sustainable manufacturing model not only to natural rubber processing industry but also to other similar manufacturing industries based in developing countries.

Mathematical modeling of drying kinetics and property investigation of natural crepe rubber sheets dried with infrared radiation and hot air

ABSTRACTIn this research study, infrared radiation was combined with hot-air drying to dry natural crepe rubber sheets (NCRS). The system was built and installed with real-time automatic measurement tools to collect data on drying kinetics. The drying temperature was set at 40, 50, or 60°C. Seven mathematical models were tested for fitting the drying kinetics at each temperature. The two statistical indicators used to select the best fit model were the coefficient of determination (R2) and the chi-square . The appropriate drying temperature was 50°C because NCRS tends to melt and tear beyond this temperature. The dried NCRS was analyzed for raw rubber properties in terms of Mooney viscosity, initial plasticity (Po), and plasticity retention index (PRI), and the dried NCRS was vulcanized with chemical crosslinking agents. Vulcanized NCRS samples were characterized for mechanical properties (tensile strength and elongation at break) and thermal properties (differential scanning calorimetry and dynamic mechanical analysis). The drying at 50°C gave good rubber properties with high PRI value, good mechanical properties, and thermal properties in the normal range. Especially, the mechanical properties were improved by the use of infrared radiation during drying, which is due to the shift of double and conjugated double bond crosslinks. Finally, the energy consumption was 92 kWh over the typical 6 days of drying.

Carbon Footprint of Rubber/Sugarcane Intercropping System in Sri Lanka: A Case Study

The global climate has been changing with the elevated CO2 in the atmosphere; hence identification of effective measures to mitigate or combat the adverse effects of climate change is at uttermost importance. The goal of Government of Sri Lanka (GoSL) for planting 40,000ha of rubber (Hevea brasiliensis Muell. Arg.) in the Uva province may partly address this issue sequestering the key greenhouse gas (GHG), CO2. Farmers in the area usually practice intercropping sugarcane (Saccharum officinarum) under immature rubber plants for extra income during the initial period of rubber cultivation. In the process of valuing rubber cultivation in mitigating the climate change effect, information on net greenhouse gas (GHG) emission from rubber/sugarcane intercropping system is required. Being scanty of such knowledge, this study was aimed to estimate the carbon footprint in the cultivation of rubber/sugarcane intercropping system in Sri Lanka.GHG emissions from the cultivation of rubber and sugarcane were calculated using the information available in the smallholdings having rubber/sugarcane intercropping in Monaragala district (IL2). GHG emission resulting from raw rubber processing, i.e. Ribbed Smoked Sheets (RSS) and Crepe Rubber (CR), was assessed using the data available in Kumarawatta Estate, Monaragala and Dartonfield Estate, Agalawatta, respectively. Also, GHG emission resulting from processing refined sugar was gathered from Palwatta Sugar Industries (Ltd), Monaragala. Carbon sequestration capacities of both crops were adopted from previous studies. Guidelines of Intergovernmental Panel on Climate Change (IPCC) were used in the estimation of carbon footprint. GHG emission in the process of cultivating rubber for its lifespan (30 years) was 65.15 CO2-eq ton/ha. When sugarcane was cultivated in rubber lands for four year period as a rubber/sugarcane intercropping system, GHG emission increased only by 9.72 CO2-eq ton/ha. Processing of RSS throughout the lifespan was responsible for additional 93.49 CO2-eq ton/ha emission whilst that for processing CR was limited to 50.14 CO2-eq ton/ha. Processing of refined sugar during four year intercropping period was accountable only for 0.62 CO2-eq ton/ha emission. In conclusion, carbon footprint (Net GHG emission) of cultivating rubber/sugarcane intercrop to produce CR and refined sugar was -1537.02 CO2-eq ton/ha/30yr whilst that for RSS and refined sugar was -1493.73 CO2-eq ton/ha/30yr. Increase in carbon footprint by intercropping sugarcane was only ca. 0.5% over mono cropping rubber. Potential application of this information in developing carbon trading projects is discussed.

Raw rubber and viscoelastic properties of organoclay filled latex crepe rubber

Organoclay (OC) filled natural rubber (NR) latex crepe was prepared in view of investigating the effect of organoclay on raw rubber properties and viscoelastic properties by incorporating aqueous dispersion of OC clay into NR latex followed by conventional acid coagulation procedure. Raw rubber properties of OC filled fractionated bleached (FB) and unfractionated unbleached (UFUB) crepe rubber were evaluated to characterized the composite samples in comparison to standard crepe rubber whilst process based characterization was carried out with Moony viscosity and Mooney relaxation data. Raw rubber properties have shown that OC acts as a pro-oxidant and as a result, Initial Plasticity (Po) and Plasticity Retention Index (PRI) which measures the thermo-oxidative degradation were negatively affected. Viscoelastic behaviour, as measured with low shear strain rate flow properties, is significantly affected by the addition of OC into the NR latex. Reduction of Mooney viscosity of OC filled crepe rubber has been explained with thermal oxidation as a result of metal impurities in the OC and plasticization caused by the organic modifier of the OC. Mooney stress relaxation has shown that lower clay loading provides a better processability and dispersion of OC within the crepe rubber.

Insight into prevention of enzymatic browning and increase of antioxidant potential of crepe rubber with ethephon stimulation

The effect of different ethephon concentrations 1%-5% (w/v) on colour of crepe rubber and plasticity retention index (PRI) was studied. The study was conducted with the RRISL 121 clone using S/2, d3 harvesting system. The results revealed that ethephon stimulation affects strongly the antioxidant and polyphenol oxidase (PPO) inhibitory potential. Further, thiol content and PRI values were increased while giving low Lovibond colour index upto 3% ethephon concentration and the properties were found to be inferior above 3% concentration. A probable reaction mechanism is proposed for colour improvement with optimum concentration of ethephon.

GHG Emission as a Measure of Environmental Impacts in Producing Selected Natural Rubber Products

Rubber production has been taking place in Sri Lanka for more than 100 years. This study presents emission of green house gases (GHG) associated with the production of concentrated latex and crepe rubber in Sri Lanka. According to the extent of rubber plantation by districts of Sri Lanka, Kegalle, Kalutara, Ratnapura and Colombo are the major rubber growing districts. Out of these districts Kegalle, Kalutara and Colombo were selected for the study. List of rubber manufacturing industries were used to select industries. Those industries were categorised based on number of workers such as small scale, medium scale and large scale. Industries were selected from all categories proportionate to the total no of industries in the list. Based on the list of rubber factories belonging to plantation companies and three factories belonging to private companies in Sri Lanka were used to collect all activity data were collected for a year. From April 2010 to March 2011 (financial year). The agricultural activities in rubber plantation and fuel consumption for staff transportation were not taken to account. Emission of greenhouse gases associated with the production of primary rubber products (crepe rubber and centrifuge latex) are quantified as functions of activities and emission factors. Diesel uses in fresh latex transportation, electricity use, diesel use for self power generation, production of diesel for latex transportation and self power generation and waste water generation from concentrated and crepe factories were considered for GHG emission calculation. Other than that, ammonia production for concentrated latex factories and firewood use in crepe rubber factories were also considered. Total emission for the year 2010 from the production of concentrated latex is 1,339,663 Ton of CO2 Eq. and from the production of crepe rubber is 8,431,884.1 ton of CO2 Eq. The emission factors of the production of concentrated latex and crepe rubber was estimated as 55.016 and 138.123 ton CO2 Eq per ton of product respectively. Emissions are largely associated with waste water discharges and energy use. This study discusses to reduce GHG emissions from above two product production processes. Keywords: GHG, Emission, Concentrated latex, Crepe rubber

Application of Multivariate Process Control (MPC) in the Natural Rubber Industry

Statistical process control (SPC) monitors specified quality characteristics of a product orservice to detect whether the process has changed in a way that would affect product qualityand to measure the current quality of products or services. This study introduces severalapplications on multivariate process control in the rubber industry employing the factory datain the Dartonfield estate of the Rubber Research Institute of Sri Lanka (RRI). Multivariateprocess control was applied to consider two or more variables simultaneously. In this studymultivariate techniques were done for the application of bleaching agents, sodium bisulphateand acids in the process of crepe rubber production.Multivariable scatter diagrams and control ellipse has been used to show the process whenthe multivariate data composed of two variables. Hotelling T2 control chart was used tomonitor application of chemicals simultaneously in a single chart. Principal components wereused to interpret dimensions of components and star charts were applied to diagnostic fordetermining the relative contributions of the each chemical component. The multivariateEWMA (MEWMA) control chart for monitoring the process mean vector was astraightforward extension of the univariate EWMA chart. The graphical presentation is veryimportant and it is a quick way to see the advantages of MPC.Multivariate Statistical analysis is concerned with data that consist of sets of measurementson a number of variables. So, multivariate quality control provides a way for monitoring andevaluation of chemical application process. Scatter plots and control ellipse is very importantto detect out of control points and relationships as a graphical method. Hotelling T2 is animportant chart that can be decomposed into an overall measure of distance of the groupmeans from the target T2 and measure of variability. Principal components can be useful formultivariate quality control, especially to observe variation of dimensions of chemicalapplications. Multivariate EWMA procedure use additional information from recent historyof the process and it is more sensitive in monitoring chemical application process.Therefore multivariate process control provides way for manufacturer to test their products inan environment that provide many advantages over univariate models.

Raw rubber properties of crepe rubber manufactured from preserved natural rubber latex using different combinations of preservatives

Objective of this study was to investigate the effect of different preservative systems used in the concentrated latex manufacturing industry on physical properties of the latex crepe made out of them. Unfractionated and unbleached (UFUB) crepe rubber manufactured from latices preserved with ammonia, tetramethylthiuram disulphide, zinc oxide and a 1:1 mixture of tetramethylthiuram disulphide (TMTD) and zinc oxide (LATZ) were subjected to examine their raw rubber properties. It was observed that UFUB crepe rubber manufactured out of either ammonia preserved, ZnO preserved or chemically untreated latices have better resistance to thermo-oxidative degradation compared to UFUB crepe rubber made out of both TMTD and LATZ preserved latex. Further, it was observed that neither ammonia nor ZnO has any effect on the thermal degradation of crepes made out of ammonia or ZnO preserved latex. It was clear from the results that the TMTD added as a component of the preservative system adversely affects the resistance to thermo-oxidative degradation as judged by PRI of crepe produced. Crepe rubber manufactured from TMTD preserved latex exhibits unusually lower PRI and a nitrogen content comparable with the normal UFUB crepe rubber. Skim crepe rubber which is considered a by-product of the latex centrifuging industry, usually records higher nitrogen percentages and lower PRI values. Therefore, evaluation of these two parameters could be used to differentiate skim crepe rubber from normal UFUB crepe rubber. It was also observed that TMTD has a strong negative impact on PRI of crepe rubber even at very low concentrations. It could be proposed that dimethylthiuram monosulphide (DMTMS) free radicals generated by thermal decomposition of TMTD are responsible for this PRI reduction.

Effect of iron in processing water on quality of crepe rubber

Latex crepe rubber is the purest form of natural rubber and contamination of crepe rubber with metal ions should be avoided to maintain the quality of the rubber, especially to prevent the oxidative aging during storage. The influence of iron in processing water on raw rubber properties of crepe rubber has been investigated. Our research has shown that most of the iron ions contaminated from the processing water were leached out during the production process. The remaining iron ions in the crepe rubber catalyse the thermo-oxidative degradation and thereby significantly affect the oxidative stability of the rubber. Combination effect of Fe3+ ions and aromatic thiol, which adds into natural rubber (NR) latex to bleach the yellow pigments in fractionated bleached (FB) crepe rubber, further reduced its resistance to thermal oxidation, measured by Plasticity Retention Index (PRI). Therefore, fractionated unbleached (FUB) crepe rubber has a better oxidative stability than fractionated bleached (FB) crepe rubber. Further investigations carried out to study the effect of oxidation state of iron showed that not only Fe3+ ions but also Fe2+ ions catalyses the oxidative degradation process of natural rubber (NR). Based on our experimental results, new specifications for total iron concentration in the processing water and maximum allowable iron concentration in latex crepe rubber have been proposed.