Tear Strength Values Research Articles

Preparation and Characterization of Poly(Lactic Acid)/Ethylene Glycidyl Methacrylate Copolymer Blends

Both tensile and tear strength values of PLAxEGMCy blown-film specimens in machine and transverse directions improve significantly and reach the maximum values as their EGMC contents approach an optimum value of 6 wt%. The melt shear viscosity values of PLAxEGMCy resins measured at varying shear rates are significantly higher than those of the PLA resin and increase consistently with their EGMC contents. FT-IR analysis suggest that the carboxylic acid groups of PLA molecules react with the epoxy groups of EGMC molecules during the reactive-extrusion processes of PLAxEGMCy specimens. Further DMA and morphological analysis of PLAxEGMCy specimens reveal that EGMC molecules are phase-separated with PLA molecules at EGMC contents equal to or more than 2 wt%, since distinguished phase-separated EGMC droplets and tanδ transitions were found on fracture surfaces and tanδ curves of PLAxEGMCy specimens, respectively. Possible reasons accounting for the above interesting properties of the PLA/EGMC specimens are proposed in this study.

A STUDY IN VULCANIZATION OF NEOPRENE RUBBER (WRT) BY POLYMETHYLOL RESIN (RESOL) .

The vulcanization of neoprene (WRT) with different loading of polymethylol resin (Resol) was investigated to understand the role of resol as curing agent. The cure rate fasted when resol was added to the rubber compound, and the change in the mechanical properties were significant. An improvement in mechanical properties were seen with 7.5 phr loading of resol, while an adverse effect observed only with a high loading at 10 phr and in absence of magnesia and zinc oxide from rubber compound. Rubber compounds containing different loading of resol show slight decrease in tensile strength, elongation, and tear strength values after 5 days at 80 C , while high increase in hardness and modulus at the same conditions.

Physical assessment of composite biodegradable films manufactured using whey protein isolate, gelatin and sodium alginate

Composite films were manufactured using whey protein isolate (WPI), gelatin (G) and sodium alginate (SA) using a simplex centroid design. Tensile strength (TS), puncture strength (PT), percentage elongation at break point (E), tear strength (TT), water vapour permeability (WVP) and oxygen permeability (OP) of films were evaluated. The interactions between biopolymers showed quadratic effects ( P < 0.01) on TS, E, PT, TT and WVP values. Scanning electron microscopy (SEM) was performed to investigate the microstructures of composite films. The proportion of ingredients required to produce the optimum composite films was determined to be: WPI (g):G (g):SA (g) = 8.0:12.0:5.0. Overall, films (WPIGSA-9) produced using the combination of WPI (g):G (g):SA (g) = 10.0:16.0:14.0 demonstrated the best barrier to oxygen (8.00 cm 3 μm/m 2 d kPa); while films (WPIGSA-1) showed the best barrier to water vapour (48.04 g mm/kPa d m 2); films (WPIGSA-6) using the combination of WPI (g):G (g):SA (g) = 10.0:17.5:22.5 had the best mechanical properties of all of the experimental composite films tested.

Efeito da concentração de segmentos rígidos nas propriedades físico-mecânicas, químicas e na morfologia de elastômeros microcelulares de poliuretano

Neste trabalho, foram preparados três diferentes elastômeros microcelulares de poliuretano (EMPU) baseados em 4,4'- diisocianato de difenilmetano (MDI), com diferentes concentrações de fase rígida (Formulações 1, 2 e 3, com 32, 35 e 42% de fase rígida, respectivamente). As amostras foram preparadas através do método de duas etapas, pelo sistema de pré-polímero. As amostras dos EMPU foram caracterizadas através de ensaios físico-mecânicos, químicos e morfológicos. Os resultados dos ensaios mecânicos mostraram que o aumento no percentual da fase rígida levou a um aumento na resistência à tração e na resistência ao rasgo. O alongamento na ruptura não apresentou variação significativa com a modificação do percentual da fase rígida. O ensaio de resistência química demonstrou que os EMPU formulados apresentaram baixos índices de inchamento para solventes industriais comumente utilizados. Entretanto, em acetona, um elevado índice de inchamento foi observado. As análises morfológicas indicaram que o aumento no percentual da fase rígida promoveu a formação de células menores distribuídas de forma mais homogênea no EMPU.

Sugar–cellulose composites VII. A comparative assessment of corn syrup as a fiber substitute in paper

The ability of the mixture of α-linked glucose oligomers in corn syrup to function as intrafiber components of paper is statistically assessed at the 95% confidence level for two degrees of refining (257 and 402 mL CSF) of never-dried commercial softwood and hardwood/softwood pulps. Independent of the extent of refining, the replacement of the beaten fibers by corn syrup at about the 6% level does not result in a statistically significant deterioration (two-sided t-test, p = 0.05) of the ISO brightness or of the tensile, tear, burst or surface strength values of the resultant papers. The economic potential of such fiber replacement is discussed. As paper additives, the mixed α-oligomers (corn syrup), glucose and lactose perform indistinguishably.

In-situ elastomer composite based on fluorocarbon elastomer/liquid crystalline polymer blend

Blends of fluorocarbon elastomer (FKM) and liquid crystalline polymer (LCP) have been prepared by melt mixing technique. Processing studies indicated the decrease in the viscosity and the state of cure with the addition of 10 wt% LCP, and then increased at a higher rate with the addition of more LCP to the blend. The tensile strength values decreased at lower level of LCP. However, the modulus and tear strength values increased with higher increment of LCP content. From the X-ray diffraction measurements it has been observed that the crystalline structure of the FKM is greatly affected by the addition of LCP. The degradation temperatures from thermogravimetric analysis (TGA) suggested improved thermal stability of the fluorocarbon-LCP blends. From the dynamic mechanical analysis (DMA), it has been found that the glass transition temperature (T g) of the blends increased with increase in LCP content. For the compositions of 10 wt% and 20 wt% LCP blends, enhancement in storage modulus is found above the glass transition of FKM. Under dynamic conditions the increase of LCP content restricts the matrix flow and hence cracks developed at the interface of the LCP fibrils and matrix.

Vulcanization characteristics and mechanical properties of natural rubber–scrap rubber compositions filled with leather particles

AbstractScrap rubber recycling combined with waste leather particles in natural rubber compounds has been studied. The effect of leather and scrap rubber loading on vulcanization characteristics of natural rubber compounds has been evaluated. The presence of leather was found to reduce the scorch time and increase the maximum and minimum torque. While reversion was not observed in the absence of leather at 150 °C, it was more prominent when leather was incorporated. Mechanical properties such as tensile strength, elongation at break, tear strength, modulus and hardness were found to increase on increasing the scrap rubber loading in the absence of leather. Compounds containing leather exhibited higher tensile strength, modulus, hardness and tear strength values but the modulus and hardness values were found to decrease as the scrap rubber loading increased. All the vulcanizates exhibited only limited swelling in different media as the swelling of one phase of the composite was found to be restricted by the other phase. Copyright © 2004 Society of Chemical Industry

Mechanical properties of soft liner–poly(methyl methacrylate)‐based denture material

AbstractIn this study, the mechanical properties of two different permanent soft lining materials and their bonding to poly(methyl methacrylate) (PMMA) were compared. Both of the soft liners were heat‐cured commercial materials. The polymerization was carried out by conventional methods suggested by manufacturer, and the curing was done at the temperature of boiling water for 5, 15, 25, and 35 min. The sample groups were tested in the computer‐aided tensile‐testing machine at a rate of 2 mm/min. The slow rate helps the collection of more and more reliable data. At this time, the stress–strain curves were used to calculate ultimate tensile strength, elastic modulus, resilience, and toughness. The measurements were carried for PMMA, Molloplast B, Flexor, and a combination of PMMA/soft liner. After introducing the soft lining material on PMMA of the same thickness, the new material structure was more elastic than the original PMMA. Flexor showed adhesive failure at studied curing periods, but Molloplast B gave larger tear strength values and cohesive rather than adhesive failure at the 25‐min and 35‐min curing times. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 467–474, 2002

Morphology and mechanical and viscoelastic properties of natural rubber and styrene butadiene rubber latex blends

The morphology and mechanical and viscoelastic properties of a series of blends of natural rubber (NR) and styrene butadiene rubber (SBR) latex blends were studied in the uncrosslinked and crosslinked state. The morphology of the NR/SBR blends was analyzed using a scanning electron microscope. The morphology of the blends indicated a two phase structure in which SBR is dispersed as domains in the continuous NR matrix when its content is less than 50%. A cocontinuous morphology was obtained at a 50/50 NR/SBR ratio and phase inversion was seen beyond 50% SBR when NR formed the dispersed phase. The mechanical properties of the blends were studied with special reference to the effect of the blend ratio, surface active agents, vulcanizing system, and time for prevulcanization. As the NR content and time of prevulcanization increased, the mechanical properties such as the tensile strength, modulus, elongation at break, and hardness increased. This was due to the increased degree of crosslinking that leads to the strengthening of the 3-dimensional network. In most cases the tear strength values increased as the prevulcanization time increased. The mechanical data were compared with theoretical predictions. The effects of the blend ratio and prevulcanization on the dynamic mechanical properties of the blends were investigated at different temperatures and frequencies. All the blends showed two distinct glass-transition temperatures, indicating that the system is immiscible. It was also found that the glass-transition temperatures of vulcanized blends are higher than those of unvulcanized blends. The time–temperature superposition and Cole–Cole analysis were made to understand the phase behavior of the blends. The tensile and tear fracture surfaces were examined by a scanning electron microscope to gain an insight into the failure mechanism. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 2189–2211, 2000

Morphology and mechanical and viscoelastic properties of natural rubber and styrene butadiene rubber latex blends

The morphology and mechanical and viscoelastic properties of a series of blends of natural rubber (NR) and styrene butadiene rubber (SBR) latex blends were studied in the uncrosslinked and crosslinked state. The morphology of the NR/SBR blends was analyzed using a scanning electron microscope. The morphology of the blends indicated a two phase structure in which SBR is dispersed as domains in the continuous NR matrix when its content is less than 50%. A cocontinuous morphology was obtained at a 50/50 NR/SBR ratio and phase inversion was seen beyond 50% SBR when NR formed the dispersed phase. The mechanical properties of the blends were studied with special reference to the effect of the blend ratio, surface active agents, vulcanizing system, and time for prevulcanization. As the NR content and time of prevulcanization increased, the mechanical properties such as the tensile strength, modulus, elongation at break, and hardness increased. This was due to the increased degree of crosslinking that leads to the strengthening of the 3-dimensional network. In most cases the tear strength values increased as the prevulcanization time increased. The mechanical data were compared with theoretical predictions. The effects of the blend ratio and prevulcanization on the dynamic mechanical properties of the blends were investigated at different temperatures and frequencies. All the blends showed two distinct glass-transition temperatures, indicating that the system is immiscible. It was also found that the glass-transition temperatures of vulcanized blends are higher than those of unvulcanized blends. The time-temperature superposition and Cole-Cole analysis were made to understand the phase behavior of the blends. The tensile and tear fracture surfaces were examined by a scanning electron microscope to gain an insight into the failure mechanism.

Morphology, mechanical properties, and failure topography of semi-interpenetrating polymer networks based on natural rubber and polystyrene

Semi-interpenetrating networks (semi-IPNs) were prepared from natural rubber (NR) and polystyrene (PS) by the sequential method. In these semi-IPNs the NR phase was crosslinked while the PS phase was uncrosslinked. Different initiating systems such as dicumyl peroxide (DCP), benzoyl peroxide (BPO), and the azobisisobutyronitrile (AIBN) system were used for polymerizing the PS phase. The blend ratio was varied by controlling the swelling of NR in the styrene monomer. The mechanical properties of the semi-IPNs, namely, density, tensile strength, tear strength, elongation at break, tension set, tensile set, impact strength, and hardness, were determined. The morphology of different IPNs was studied using scanning electron microscopy. A compact morphology with a homogeneous phase distribution was observed in the semi-IPNs. The properties of the semi-IPN do not change much with the initiating system. However, in most cases, the DCP initiating system showed slightly superior performance. The tensile and tear-strength values of the IPNs were found to increase with increasing plastomer content. The crosslink density of the semi-IPNs also increased with increase in the polystyrene content. The experimental values were compared with theoretical models such as series, parallel, Halpin Tsai, Coran, Takayanaki, Kerner, and Kunori. The tensile and tear-fracture surfaces were examined using a scanning electron microscope. The fracture patterns were correlated with the strength and nature of the failure. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 2327–2344, 2000

A comparison of three methods for preparing reversible hydrocolloid duplicating material

This study compared the effects of repeated microwave oven and double-boiler liquefactions and prolonged autoduplicator storage on four physical properties of one reversible hydrocolloid duplicating material. No significant differences were observed between the linear dimensional change and detail reproduction of the three liquefaction techniques. Tear strength differences most clearly distinguished the techniques and effects of aging. Fifteen double-boiler remeltings produced tear strength values lower than those recorded for material stored in an autoduplicator for 2 weeks. Thirty microwave melting cycles still produced tear strength values equivalent to that of the autoduplicator material. After 30 melting cycles the compressive strengths of the microwave and double-boiler materials were inferior to that of the stored autoduplicator material.

Tear and processing behaviour of short sisal fibre reinforced styrene butadiene rubber composites

AbstractThe tear failure and processing characteristics of short sisal fibre reinforced styrene butadiene rubber (SBR) composites were investigated. Tear strength was examined with special reference to the effects of fibre length, fibre orientation, fibre concentration and bonding agent. It was observed that the tear strength depends on all the above factors. The tear failure mechanism was analysed from fractographs taken using a scanning electron microscope (SEM). During tear testing, the composites failed by a shearing process. Microscopic examination of cracks propagating in SBR composites revealed that the amorphous SBR matrix developed cracks, leaving ligaments of rubber attached to the broken fibres. The rubber particles were stretched as the crack opened and failure occurred at large critical extensions. It was observed that an increase in the concentration of fibres increased the tear strength in both longitudinal and transverse directions. The tear strength values were almost three to four times higher than those of the unfilled vulcanizates under similar conditions. In order to analyse the processing behaviour, the green strength, mill shrinkage and Mooney viscosity of the compounds were determined. Finally, the polymer–filler interaction was studied using the Lorenz–Park and Kraus equations.

Tearing behavior and recyclability of nitrile rubber/poly(ethylene-co-vinyl acetate) blends

The tear strength of nitrile rubber/poly(ethylene-co-vinyl acetate) (NBR/EVA) blends was measured as a function of blend composition in an Instron universal testing machine. An increase in tear strength was observed with increasing EVA content. The variation in this property was correlated with the microstructural morphology of the system. The tear failure mechanism of these blends as a function of blend composition was studied by examining the failure surfaces and the fracture patterns correlated with the strength and failure of these materials. Various models such as parallel model, series model and the Halpin-Tsai equation were used to fit the experimental tear strength values. In order to analyze the reprocessability of these blends, the blends were recycled up to three times and the mechanical properties were measured. It was found that the properties of the blends were little affected by recycling.

Application of Magnesium Hydroxide as a Flame Retardant and Smoke Suppressant in Elastomers

Abstract This study has provided information about the performance of magnesium hydroxide in two EVA copolymers while also comparing the performance of the copolymers. The low-ethylene EVA tolerates the higher filler loadings of magnesium hydroxide more readily than the high-ethylene EVA. On the other hand, the latter has certain advantages, exhibiting higher tensile and tear strength values. Increasing the loading of magnesium hydroxide has a beneficial influence on tear strength and water adsorption. It was also interesting to note the differences in limiting oxygen index between the two sets of filled compounds. Compared with EPDM, much lower filler loadings are needed to achieve similar values of oxygen index. Taking all properties into account, the range 100 to 150 phr of magnesium hydroxide would be recommended for further development work.

Comparison of tear test methods

Tear strength is an important property of a rubber vulcanisate, particularly when considering it for applications such as cables, hoses and tyres. In the present study four test methods, as specified for vulcanised rubbers in British Standards (BS 903 Part A3 and BS 6899), have been investigated on five different compositions based on a nitrile natural rubber, an ethylene acrylic rubber, a polyurehane and undisclosed chloroprene elastomer. The objective of the study was to examine the influence of thickness, grain effects and strain rate on the tear strength. It was also intended to establish if the different tear test methods would rank materials in the same order and whether a constant ratio exists between the tear strength values obtained using the different methods for different materials. Sample thicknesses in the range 0·5–3 mm and strain rates in the range 100–500 mm/min all produced small but significant variations in the tear strength, confirming that standardisation of these variables is very desirable. Grain effects were found to produce even larger variations in the test results, particularly for the trouser test pieces. It was found that the tests could be divided into two groups: • (a) trouser and cable tests; • (b) angle and crescent tests. The tests in each group ranked materials in the same order and the ratios between tests on different materials within each group was approximately the same.

Analysis of Tear Strength

An analysis has been made of the factors involved in the A.S.T.M. Trapezoid Tear-Strength Test. The tear strength of a fabric measured by this test is dependent mainly on the extensibility of the threads, the breaking strength of the threads, the effective specimen length, and the number of threads per inch of fabric. An analytical interpretation of the part played by each of these factors resulted in a general equation relating tear strength to the breaking strength and extensi bility of a given fabric. The evaluation of the derived equation gave a good correlation between the calculated and measured tear-strength values of the fabrics investigated.