Low Sulfur-Sulfenamide Accelerator Combinations for Injection Molding of Cis-1,4-Poly(Isoprene)

1972 ◽  
Vol 45 (5) ◽  
pp. 1403-1411 ◽  
Author(s):  
J. F. O'Mahoney
Keyword(s):  
Carbon Black ◽  
Injection Molding ◽  
Sulfur Concentration ◽  
Cure Rate ◽  
Tetramethylthiuram Disulfide ◽  
Excellent Method ◽  
Injection Molded ◽  
Low Levels ◽  
Low Sulfur ◽  
Made In

Abstract Earlier work with cis-l,4-poly(isoprene) suggested that low levels of sulfur and high levels of sulfenamide accelerator with high levels of secondary accelerator was an excellent method for curing injection molded stocks. However, subsequent experience showed that despite the benefits of reduced sulfur concentrations on reversion, increased sulfur, increased sulfenamide, and reduced secondary accelerator concentrations were necessary for adequate cure and safety. From that experience we explored further and found that, if the sulfenamide concentration is held constant at a higher level and the secondary accelerator concentration is increased as sulfur concentration is decreased, nearly equivalent hardness and modulus can be maintained throughout most cure conditions with no loss in safety and cure rate and much improvement in reversion resistance. Studies were made in a carbon black filled stock with N-cyclohexyl-2-benzothiazole sulfenamide (CBS), N-oxodiethylene-2-benzothiazole sulfenamide (DBS), and N-morpholinyl-2-benzothiazolyl disulfide (MBD) as primary accelerators and tetramethylthiuram monosulfide (TMTM) and tetramethylthiuram disulfide (TMTD) as secondary accelerators.

scholarly journals Peculiarities of Injection Molding Conducting Composites

2018 ◽  
Vol 248 ◽  
pp. 01006
Author(s):  
Yovial Mahyoedin ◽  
Jaafar Sahari ◽  
Andanastuti Mukhtar ◽  
Norhamidi Mohammad ◽  
Iqbal
Keyword(s):  
Composite Material ◽  
Carbon Black ◽  
Injection Molding ◽  
Test Procedure ◽  
Molded Parts ◽  
Twin Screw ◽  
Probe Test ◽  
Injection Molded ◽  
Conducting Composites

The investigations in this study focused on the characteristic of feedstock in an effort to understand the mechanism of injection molded in composite material. A composite, which has 75% wt. filler, consist of graphite (G), carbon black (CB) and polypropylene copolymer (PP). Twin-screw co-rotating extruder used for mixing materials. The conductivity of the molded parts measured using a four-point probe test procedure. The results showed that the injection molding conducting composites, which aggregated into larger clusters, tended to disperse unevenly into the PP, resulting in fewer particle-particle contacts and, consequently, a lower-conductivity composite in some part of the molded.

The Aging of Vulcanized Rubber under Varying Elongation

1930 ◽  
Vol 3 (1) ◽  
pp. 131-143
Author(s):  
A. A. Somerville ◽  
J. M. Ball ◽  
W. H. Cope
Keyword(s):  
Carbon Black ◽  
Tetramethylthiuram Disulfide ◽  
Vulcanized Rubber ◽  
Synthetic Rubber ◽  
Aging Curve ◽  
Low Sulfur

Abstract 1—Deterioration in the oven is approximately 30 per cent greaterat 100 per cent elongation than at 0 per cent elongation. 2—Deterioration in the bomb is almost independent of elongation. 3—Deterioration in ozone is greatest at 5 and 10 per cent elongations. 4—Deterioration in sunlight with respect to stretch is analogous to deterioration in ozone. 5—Cracking of the test rings occurs in both ozone and sunlight when the rings are stretched, but not in the oven or bomb. This cracking is greatest at 5 and 10 per cent elongations. 6—A 40 per cent carbon-black stock shows marked deterioration and cracking in both ozone and sunlight at about 10 per cent elongation. 7—High sulfur causes greater deterioration in ozone and sunlight than low sulfur. 8—Undercures show greater deterioration than the optimum cure in ozone and sunlight. 9—Loading with a filler such as whiting does not change the shape of the ozone- and sunlight-aging curves, and does not materially affect the percentage deterioration. 10—Rubber bands show progres sively poorer aging in the bomb as the stretch increases from 0 to 700 per cent, while in ozone they give an aging curve having the characteristic dip at about 10 per cent elongation, showing the least deterioration at about 400 per cent elongation. 11—Tetramethylthiuram disulfide (3 per cent) as a vulcanizing agent causes rather low percentages of deterioration in ozone and sunlight, and gives fairly flat aging curves. 12—Mineral rubber (24 per cent) causes a smaller percentage deterioration than 4 per cent except at the critical elongation of about 10 per cent. 13—Paraffin (1 per cent) causes pretty bad deterioration in ozone but provides some protection in sunlight. 14—Added antioxidant does not change the shape of the ozone- or sunlight-aging curves but may lessen the amount of deterioration. 15—Two antioxidants may give comparable results in both oven and bomb, but quite different results in ozone and sunlight. 16—Synthetic rubber gives a characteristic ozone-aging curve.

Immunologic Studies of Antithrombin III Heparin Cofactor in the Newborn

1978 ◽  
Vol 39 (03) ◽  
pp. 624-630 ◽  
Author(s):  
W E Hathaway ◽  
L L Neumann ◽  
C A Borden ◽  
L J Jacobson
Keyword(s):  
Gestational Age ◽  
Antithrombin Iii ◽  
Newborn Infants ◽  
Term Infant ◽  
Sick Newborn ◽  
At Iii ◽  
Thrombotic Complications ◽  
Low Levels ◽  
Collection Methods ◽  
Made In

SummarySerial quantitative immunoelectrophoretic (IE) measurements of antithrombin III heparin cofactor (AT III) were made in groups of well and sick newborn infants classified by gestational age. Collection methods (venous vs. capillary) did not influence the results; serum IE measurements were comparable to AT III activity by a clotting method. AT III is gestational age-dependent, increasing from 28.7% of normal adult values at 28-32 weeks to 50.9% at 37-40 weeks, and shows a gradual increase to term infant levels (57.4%) by 3-4 weeks of age. Infants with the respiratory distress syndrome (RDS) show lower levels of AT III in the 33-36 week group, 22% vs. 44% and in the 37-40 week group, 33.6% vs. 50.9%, than prematures without RDS. Infants of 28-32 week gestational age had only slight differences, RDS = 24%, non-RDS = 28.7%. The lowest levels of AT III were seen in patients with RDS complicated by disseminated intravascular coagulation and those with necrotizing enterocolitis. Crossed IE on representative infants displayed a consistent pattern which was identical to adult controls except for appropriate decreases in the amplitude of the peaks. The thrombotic complications seen in the sick preterm infant may be related to the low levels of AT III.

scholarly journals Are We Able to Print Components as Strong as Injection Molded?—Comparing the Properties of 3D Printed and Injection Molded Components Made from ABS Thermoplastic

2021 ◽  
Vol 11 (15) ◽  
pp. 6946
Author(s):  
Bartłomiej Podsiadły ◽  
Andrzej Skalski ◽  
Wiktor Rozpiórski ◽  
Marcin Słoma
Keyword(s):  
Tensile Strength ◽  
Injection Molding ◽  
Mechanical Strength ◽  
Cross Section ◽  
Fused Deposition Modeling ◽  
High Strength ◽  
Large Cross Section ◽  
Fused Deposition ◽  
Injection Molded ◽  
The Cross

In this paper, we are focusing on comparing results obtained for polymer elements manufactured with injection molding and additive manufacturing techniques. The analysis was performed for fused deposition modeling (FDM) and single screw injection molding with regards to the standards used in thermoplastics processing technology. We argue that the cross-section structure of the sample obtained via FDM is the key factor in the fabrication of high-strength components and that the dimensions of the samples have a strong influence on the mechanical properties. Large cross-section samples, 4 × 10 mm2, with three perimeter layers and 50% infill, have lower mechanical strength than injection molded reference samples—less than 60% of the strength. However, if we reduce the cross-section dimensions down to 2 × 4 mm2, the samples will be more durable, reaching up to 110% of the tensile strength observed for the injection molded samples. In the case of large cross-section samples, strength increases with the number of contour layers, leading to an increase of up to 97% of the tensile strength value for 11 perimeter layer samples. The mechanical strength of the printed components can also be improved by using lower values of the thickness of the deposited layers.

scholarly journals A Practical Numerical Approach to Characterizing Non-Linear Shrinkage and Optimizing Dimensional Deviation of Injection-Molded Small Module Plastic Gears

Polymers ◽  
2021 ◽  
Vol 13 (13) ◽  
pp. 2092
Author(s):  
Xiansong He ◽  
Wangqing Wu
Keyword(s):  
Injection Molding ◽  
High Speed ◽  
Numerical Approach ◽  
Linear Shrinkage ◽  
Influential Factor ◽  
Dimensional Deviation ◽  
Non Linear ◽  
Injection Molded ◽  
Plastic Gears ◽  
Circle Diameter

This paper was aimed at finding out the solution to the problem of insufficient dimensional accuracy caused by non-linear shrinkage deformation during injection molding of small module plastic gears. A practical numerical approach was proposed to characterize the non-linear shrinkage and optimize the dimensional deviation of the small module plastic gears. Specifically, Moldflow analysis was applied to visually simulate the shrinkage process of small module plastic gears during injection molding. A 3D shrinkage gear model was obtained and exported to compare with the designed gear model. After analyzing the non-linear shrinkage characteristics, the dimensional deviation of the addendum circle diameter and root circle diameter was investigated by orthogonal experiments. In the end, a high-speed cooling concept for the mold plate and the gear cavity was proposed to optimize the dimensional deviation. It was confirmed that the cooling rate is the most influential factor on the non-linear shrinkage of the injection-molded small module plastic gears. The dimensional deviation of the addendum circle diameter and the root circle diameter can be reduced by 22.79% and 22.99% with the proposed high-speed cooling concept, respectively.

Mixing and Comparative Properties of NR Compounds Filled with Different Types of Reinforcing Fillers

2017 ◽  
Vol 266 ◽  
pp. 172-176
Author(s):  
Pattarawadee Maijan ◽  
Nitinart Saetung ◽  
Wisut Kaewsakul
Keyword(s):  
Carbon Black ◽  
Silica Surface ◽  
High Viscosity ◽  
Cure Rate ◽  
Modified Silica ◽  
Reinforcing Fillers ◽  
Silane Coupling ◽  
Different Types ◽  
Cure Time

Mixing behaviors of the compounds filled with different reinforcing fillers were studied in correlation with compound and vulcanizate properties. Four filler systems were used including: 1) silica plus small amount of silane coupling agent; 2) carbon black; 3) pre-modified silica; and 4) silica+silane-carbon black mixed one. The results have shown that silica provides longer optimum cure time and shorter cure rate than carbon black due to accelerator adsorption on silica surface. In addition, owing to highly polar nature on silica surface the silica-based compounds show rather high viscosity, attributed to stronger filler-filler interaction as can be confirmed by Payne effect and reinforcement index. However, the commercial surface treatment or pre-modified form of silica shows superior properties than in-situ modification of silica by silane during mixing, while it gives comparable properties to carbon black-based compound. Tensile properties of vulcanizates show a good correlation with the basic properties of their compounds.

scholarly journals Post-Processing Time Dependence of Shrinkage and Mechanical Properties of Injection-Molded Polypropylene

Materials ◽  
2020 ◽  
Vol 14 (1) ◽  
pp. 22
Author(s):  
Artur Kościuszko ◽  
Dawid Marciniak ◽  
Dariusz Sykutera
Keyword(s):  
Mechanical Properties ◽  
Impact Strength ◽  
Injection Molding ◽  
Accelerated Aging ◽  
Mold Temperature ◽  
Degree Of Crystallinity ◽  
Injection Mold ◽  
Secondary Crystallization ◽  
Scanning Calorimetry ◽  
Injection Molded

Dimensions of the injection-molded semi-crystalline materials (polymeric products) decrease with the time that elapses from their formation. The post-molding shrinkage is an effect of secondary crystallization; the increase in the degree of polymer crystallinity leads to an increase in stiffness and decrease in impact strength of the polymer material. The aim of this study was to assess the changes in the values of post-molding shrinkage of polypropylene produced by injection molding at two different temperatures of the mold (20 °C and 80 °C), and conditioned for 504 h at 23 °C. Subsequently, the samples were annealed for 24 h at 140 °C in order to conduct their accelerated aging. The results of shrinkage tests were related to the changes of mechanical properties that accompany the secondary crystallization. The degree of crystallinity of the conditioned samples was determined by means of density measurements and differential scanning calorimetry. It was found that the changes in the length of the moldings that took place after removal from the injection mold were accompanied by an increase of 20% in the modulus of elasticity, regardless of the conditions under which the samples were made. The differences in the shrinkage and mechanical properties of the samples resulting from mold temperature, as determined by tensile test, were removed by annealing. However, the samples made at two different injection mold temperature values still significantly differed in impact strength, the values of which were clearly higher for the annealed samples compared to the results determined for the samples immediately after the injection molding.

ЮНВТО Всемирная туристская Барометр, и статистическое приложение Обновленная информация, ИСентябрь 2021 года

2021 ◽  
Vol 19 (5) ◽  
pp. 1-40
Keyword(s):  
The United States ◽  
International Travel ◽  
International Tourism ◽  
Modest Improvement ◽  
International Tourist ◽  
The Pacific ◽  
Travel Restrictions ◽  
Low Levels ◽  
Roll Out ◽  
Made In

International tourism shows slight recovery in June and July 2021 driven by vaccinations and border reopening International tourist arrivals (overnight visitors) in the first seven months of 2021 were 40% below the levels of 2020, and still 80% down when compared to the same period of pre-pandemic year 2019. After a weak start of the year, international tourism saw a modest improvement during the months of June and July 2021. The small improvement in June and July was underpinned by the reopening of many destinations to international travel, mostly in Europe and the Americas. The relaxation of travel restrictions to vaccinated travellers, coupled with progress made in the roll-out of COVID-19 vaccines, contributed to ease travel restrictions, lift consumer confidence and gradually restore safe mobility in Europe and other parts of the world. Small islands in the Caribbean, Africa, and Asia and the Pacific, together with a few small European destinations recorded the best performance in June and July, with arrivals coming close to, or sometimes exceeding pre-pandemic levels. July (-67%) saw comparatively better performance than June (-77%), making it the best month so far since April 2020. Asia and the Pacific continued to suffer the weakest results in January-July 2021, with a 95% drop in international arrivals compared to the same period in 2019. The Middle East (-82%) recorded the second largest decline, followed by Europe and Africa (both -77%). The Americas (-68%) saw a comparatively smaller decrease. Although destinations continued to report very weak international tourism revenues in the first seven months of 2021, several countries recorded a modest improvement in the months of June and July, and some even surpassed the earnings of 2019. The same is true for outbound travel. Among the larger source markets, France (-35% over 2019) and the United States (-49%) saw a small rebound in expenditure in July. Despite the relative improvement over the low levels of 2020, international tourism remained well below 2019 levels. This is also reflected in the evaluation made by the UNWTO Panel of Experts in the September survey, showing mixed results for the period May-August 2021. Looking ahead, most experts continue to expect a rebound in 2022, driven by unleashed pent-up demand, mostly during the second and third quarter of that year. Nearly one-third of respondents expect a potential rebound in 2023. Almost half of all experts continue to see a return of international arrivals to 2019 levels in 2024 or later.

Mechanical Properties of Injection Molded Rubber Testing Samples

2015 ◽  
Vol 752-753 ◽  
pp. 308-311
Author(s):  
Adam Skrobak ◽  
Michal Stanek ◽  
David Manas ◽  
Martin Ovsik ◽  
Vojtech Senkerik ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Injection Molding ◽  
Standardized Testing ◽  
Rubber Compound ◽  
Testing Sample ◽  
Synthetic Rubber ◽  
Injection Molded

The aim of this article is to demonstrate and asses to what extent there is an impact on the mechanical properties of a standardized testing sample made of rubber compound based on synthetic rubber EPDM and produced by injection molding in comparison with a sample produced by classic preparation (cutting off a compression molded plate) according to the standard ISO 23529.

scholarly journals Effects of Injection Molding Screw Tips on Polymer Mixing

2018 ◽  
Vol 62 (3) ◽  
pp. 241-246 ◽  
Author(s):  
Dániel Török ◽  
József Gábor Kovács
Keyword(s):  
Injection Molding ◽  
Processing Parameters ◽  
Raw Material ◽  
Molding Machine ◽  
Surface Color ◽  
Melt Temperature ◽  
Injection Molding Machine ◽  
Aesthetic Appearance ◽  
Molded Parts ◽  
Injection Molded

In all fields of industry it is important to produce parts with good quality. Injection molded parts usually have to meet strict requirements technically and aesthetically. The aim of the measurements presented in our paper is to investigate the aesthetic appearance, such as surface color homogeneity, of injection molded parts. It depends on several factors, the raw material, the colorants, the injection molding machine and the processing parameters. In this project we investigated the effects of the injection molding machine on surface color homogeneity. We focused on injection molding screw tips and investigated five screw tips with different geometries. We produced flat specimens colored with a masterbatch and investigated color homogeneity. To evaluate the color homogeneity of the specimens, we used digital image analysis software developed by us. After that we measured the plastication rate and the melt temperature of the polymer melt because mixing depends on these factors. Our results showed that the screw tips (dynamic mixers) can improve surface color homogeneity but they cause an increase in melt temperature and a decrease in the plastication rate.

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