Short-Term Test for the Induction of Lung Tumor in Mouse by Chloroprene

In a previous study by the authors,positive results from both a case-control study and a cohort study were reported.In the present study a short-term test for the induction of mouse lung tumor by chloroprene was conducted to confirm whether chloroprene monomer itself can induce tumors.Kunming albino mice weaned at 2 weeks were subjected to inhaling 0,2.9±0.3, 19.2±1.9,and 189.0±13.3 mg/m^3 chloroprene(GC purity,99.8%)4 h daily(except Sunday) for 7 months.All survivors were killed at the end of the 8th month or when moribund.No lung tumors were found before the 6th month.Thus,survivors at the 6th month were counted as effective animals.Most lung tumors observed were papilloadenomas(50/57),and a few were adenomas(7/57).The tumor incidence in the 2.9 mg/m^3 group was 8.1% in comparison to 1.3% in the control group,with the significance level at P<0.05.The higher the concentration,the higher the incidence.Examination of the multiplicity of tumor induction also demonstrated a dose-response relationship,and the number of tumors per mouse in the 189 mg/m^3 group was significant at P<0.01.1989 Academic Press,Inc.

Epidemiologic Study of Cancer Mortality among Chloroprene Workers

Both case-control and cohort studies were undertaken from July 1,1969 to June 30,1983 to ascertain whether exposure to chloroprene increases the risk of cancer.Fifty-five cases of cancer deaths were verified,16 of which had histories of exposure to chloroprene ranging from 3 to 23 years(median 11 years)with a latent period of 8-27 years,except for one case of 3 years(median 12.5 years).Fifty-four pairs were obtained by matching the cancer deaths to noncaneer deaths in accordance with strict requirements.The odds ratio for the paired data was 13,x^2=8.64,P <0.005.The average age at death from cancer of workers exposed to chloroprene was 12.7 years younger than that of unexposed workers,t'=2.98,P<0.001.The total cohort consisted of 1213 persons,among whom 149(11.6%)had histories of exposure for over 25 years,381(31.5%) for over 20 years,and 852(70.2%) for over 15 years.The SMR for the total cohort was 2.38(P <0.01),and all SMRs for the high-exposure occupations were of significance(P<0.05or P<0.01),in contrast to those of the low-exposure groups whose SMRs were low or zero.Thus, a dose-response relationship existed.Among the high-exposure occupations,maintenance me- chanics seem to have the highest risk of cancers,and SMRs for liver,lung,and lymphatic cancers were significant in this group.These results suggested that chloroprene exposure increases the risk of developing cancer.1989 Academic Press,Inc.

Low-temperature characteristicsof rubbers and performance testsof type 120 emergencyvalve diaphragms

Purpose–The type 120 emergency valve is an essential braking component of railway freight trains,butcorresponding diaphragms consisting of natural rubber(NR)and chloroprene rubber(CR)exhibit insufficientaging resistance and low-temperature resistance,respectively.In order to develop type 120 emergency valverubber diaphragms with long-life and high-performance,low-temperatureresistant CR and NR were processed.Design/methodology/approach–The physical properties of the low-temperature-resistant CR and NRwere tested by low-temperature stretching,dynamic mechanical analysis,differential scanning calorimetryand thermogravimetric analysis.Single-valve and single-vehicle tests of type 120 emergency valves werecarried out for emergency diaphragms consisting of NR and CR.Findings–The low-temperature-resistant CR and NR exhibited excellent physical properties.The elasticityand low-temperature resistance of NR were superior to those of CR,whereas the mechanical properties of thetwo rubbers were similar in the temperature range of 0℃–150℃.The NR and CR emergency diaphragms metthe requirements of the single-valve test.In the low-temperature single-vehicle test,only the low-temperaturesensitivity test of the NR emergency diaphragm met the requirements.Originality/value–The innovation of this study is that it provides valuable data and experience for futuredevelopment of type 120 valve rubber diaphragms.

Synthesis and characterization of NaA zeolite particle as intumescent fiame retardant in chloroprene rubber system

NaA zeolite with average particle size of 1 μm was successfully synthesized by microwave heating. Influences of pre-crystallization time, microwave power and microwave heating time on the synthesis of NaA zeolite were investigated. The as-synthesized sample was characterized by X-ray diffraction （XRD）, scanning electron microscopy （SEM） and particle size distribution （PSD）. Thermal and flame retardant properties as intumescent flame retardant （IFR） in chloroprene rubber （CR） system, such as thermogravimetry （TG）, limiting oxygen index （LOI）, burning rate （BR） and specific extinction area （SEA） were further investigated by adding NaA zeolite particles to CR. Experimental results show that the thermal stability and LO1 value increased while BR and SEA decreased by adding 5 phr NaA zeolite into the 40 phr IFR filled CR system.

Fatigue Life Estimation of an Elastomeric Pad by ε-N Curve and FEA

Failure analysis and fatigue life prediction are very important in the design procedure to assure the safety and reliability of rubber components. The fatigue life of a railway elastomeric pad is predicted by combining the test of material properties and finite element analysis (FEA). The specially developed chloroprene rubber material’s fatigue life equation is acquired based on uniaxial tensile test and fatigue life tests performed on the dumbbell specimens of the chloroprene rubber. The same chloroprene rubber was developed at Indian Rubber Manufacturer’s Research Association, Thane. The strain distribution contours and the maximum total principal strains of the elastomeric pad at different compressive loads are obtained using finite element analysis method. The software used for the FEA was ANSYS. The three parameter nonlinear hyperelastic Mooney-Rivlin Model and plane 182 elements were used for finite element analysis. The critical region cracks prone to arise are obtained and analysed. Then the maximum first principal elastic strain was used as the fatigue damage parameter, which is substituted in the chloroprene rubber’s fatigue life equation, to predict the fatigue life of an elastomeric pad in the number of cycles at different compressive loads. The results were compared with the technical requirements given by Indian Railway’s Research Designs and Standards Organization. These requirements were achieved up to certain extents. The results were also compared with the data available in the literature and a similarity was observed between the results acquired and literature data. In short, the proposed fatigue life prediction method can shorten the product design cycle, decrease the design and product cost remarkably and improve the quality of an elastomeric pad.

Development of Magnetic Compound Fluid Rubber Sensor for Practical Usage on &gamma;-Irradiation and Energy Harvesting for Broad-Band Electromagnetic Waves

We have performed sequential studies on new types of soft rubber for their application as artificial skin in robots and haptic sensors. Based on a proposed electrolytic polymerization method and novel adhesion technique for rubber and a metal that utilizes a metal complex hydrate, we have developed an MCF rubber sensor. This sensor uses a magnetic compound fluid (MCF), natural rubber (NR-latex) or chloroprene rubber latex (CR-latex), and requires the application of a magnetic field. The potential application of the developed sensor in various engineering scenarios and our daily lives is significant. In this regard, we investigated the effects of &gamma;-irradiation, infrared radiation, microwaves, and a thermal source on the MCF rubber sensor. We established that the MCF rubber is effective enough to be used for power generation of broadband electro-magnetic waves from &gamma;-rays to microwaves, including the range of the solar spectrum, which is the typical characteristic obtained in the present investigation. The remarkable attribute is that the MCF rubber sensor dose is not degraded by &gamma;-irradiation. We also demonstrated the effectiveness of the MCF rubber sensor in energy harvesting.