Brittle-ductile transition in PP/EPDM blends: effect of notch radius

The toughness of polypropylene (PP)/ethylene-propylene-diene monomer (EPDM) blends was studied over wide ranges of EPDM content and temperature. In order to study the effect of notch radius (R), the toughness of the samples with different notch radii was determined from Izod impact test. The results showed that both toughness and brittle-ductile transition (BDT) of the blends were a function of R, respectively. At test temperatures, the toughness tended to decrease with increasing 1/R for various PP/EPDM blends. Moreover, the brittle-ductile transition temperature (T-BT) increased with increasing 1/R, whereas the critical interparticle distance (IDc) reduced with increasing 1/R. Finally, it was found that the different curves of IDc versus test temperature (T) for different notches reduced down to a master curve if plotting IDc versus T-BT(m)-T, where T-BT(m) was the T-BT of PP itself for a given notch, indicating that T-BT(m)-T was a more universal parameter that determined the BDT of polymers. This conclusion was well in agreement with the theoretical prediction.

Brittle-tough transition in PP/EPDM blends: effects of interparticle distance and tensile deformation speed

The toughness of polypropylene (PP)/ethylene-propylene-diene monomer rubber (EPDM) blends containing various EPDM contents as a function of the tensile speed was studied. The toughness of the blends was determined from the tensile fracture energy of the side-edge notched samples. A sharp brittle-tough transition was observed in the fracture energy versus interparticle distance (ID) curves when the crosshead speed < 102.4 mm/min. It was observed that the brittle-ductile transition of PP/EPDM blend occurred either by reducing ID or by decreasing the tensile speed. The correlation between the critical interparticle distance and tensile deformation rate was compared with that between the critical interparticle distance and temperature for PP/EPDM blends. (C) 2000 Elsevier Science Ltd. All rights reserved.

Aging in EPDM used for outdoor insulation

The effect of accelerated weather aging an ethylene-propylene-diene monomer(EPDM) rubber used for outdoor insulation was studied by surface roughness measurement and X-ray photoelectron spectroscopy(xps). The surface roughness of EPDM rubber changed with aging time. The surface oxygen and aluminum content were found to increase and that of carbon, silicon and nitrogen to decrease with time. The detailed XPS analysis indicated that the concentration of carbon in C-C decreased and that of highly oxidized carbons in C-O, C=O and O=C-O increased with time, which was due to the oxidation of EPDM rubber polymer. The appearance of O=C-O on the surface of EPDM rubber was a signal that EPDM rubber became aged. The aging speed decreased with time. The aging mechanism is discussed also.

Characterization of propylene/ethylene copolymers sequentially polymerized with delta-TiCl3/Et2AlCl catalyst system

Morphological studies of a series of propylene/ethylene sequential polymers have been carried out by permanganic etching and transmission electron microscopy, as an aid to characterization, in conjunction with differential scanning calorimetry. The materials were synthesized using a titanium-based catalyst, with propylene and either ethylene or ethylene/propylene mixture introduced successively, with the aim of examining whether a proportion of block copolymer is obtained. These materials show a complicated phase structure which does not simply reflect polymerization time but varies greatly, especially in regard to the order of introduction of the monomers, and their morphology differs in a number of ways from that of typical commercial materials. Comparison of the materials, as synthesized and after extraction with heptane, suggests that there is a certain amount of material which can compatibilize polypropylene- and ethylene-rich phases, but it was not possible to decide whether it does in fact have block structure.

FACTOR-ANALYSIS APPLIED TO X-RAY-DIFFRACTION DIAGRAMS OF POLYMER BLENDS

The feasibility of applying the method of factor analysis to X-ray diffraction diagrams of binary blends of polypropylene and ethylene-propylene-diene terpolymer (PP/EPDM) was examined. The result of mathematical treatment was satisfactory. The number of scattering species and their concentrations in six kinds of PP/EPDM blends were determined. The separation of the spectral peaks of each species in the blends, contributing spectral intensities, was carried out.

Enhancement of the properties of EPDM/NBR elastomers using nanoclay for seal applications

In this research, we have investigated the effects of addition of different percentages of nanoclay to the ethylene propylene diene monomer (EPDM) and nitrile butadiene rubber (NBR) on the characteristics of these rubbers as seal material. Properties such as tensile strength, modulus at different extensions, elongation at break, compressive set, hardness, and permeability and abrasion resistance are tested to assess the effect of addition of the nanoclay. Results indicate that addition of nanoclay at certain compositions could slightly reduce the strength of the rubber. However more stable modulus at different strains are provided, the hardness of the rubber is preserved and slightly enhanced, the permeability is reduced in both rubbers especially considerable decrease in EPDM is observed which is desirable in diminishing the effect of explosive decompression. At the same time the compression test shows that the nanoclay improves the performance of the rubbers under compression which is essential in seal application. The X-ray diffraction tests clarify that the dispersion of the nanoclay in the NBR samples is of high quality. In the EPDM samples, the dispersion is in need of improvement. POLYM. COMPOS., 30:1657-1667, 2009. © 2008 Society of Plastics Engineers.

EPDM/CIIR Blends : Effect of EPDM Grade on Mechanical Properties

Blends of chlorobutyl rubber (CIIR) with two grades of ethylene-propylene diene monomer rubber (EPDM) were prepared and the effect of blend ratio on the cure characteristics, hot air ageing resistance, steam ageing resistance, and mechanical properties were evaluated. The blend of CIIR with EPDM grade 301 T showed additive behavior and the blend with the other grade of EPDM (NDR 4640) showed synergistic behavior.

Improved Mechanical Properties of NR/EPDM and NR/Butyl Blends by Precuring EPDM and Butyl

Ethylene-propylene-diene rubber (EPDM) and isobutylene-isoprene rubber (IIR) were compounded, precured to a low degree, and then were blended with natural rubber (NR). The compounding ingredients for NR were then added and the final curing was done. NR/ EPDM and NR/IIR blends, prepared using this method, were found to possess much improved mechanical properties as compared to their conventional counterparts. The optimum precuring crosslink density that has to be given to the EPDM and IIR phases has been determined.

Compatibility Studies on Sulphur Cured EPDM/CIIR Blends

The principal objective of this study was to explore the compatibility of a blend of two synthetic elastomers viz., ethylene-propylene-diene rubber (EPDM) and chlorobutyl rubber (CIIR). Various commercial grades of EPDM were blended with a specific grade of CIIR at different proportions. The mechanical properties such as tensile strength, tear strength, ageing resistance, etc. were studied. On the basis of the observed physical properties, two particular grades of EPDM were found to be compatible with CIIR. Differential scanning calorimetry and scanning electron microscopy confirmed the results. Chlorosulphonated polyethylene was added as a compatibilizing agent to overcome the phase separation of the other two incompatible grades of EPDM in blending with CIIR. The results revealed that the addition of compatibilizer greatly improves the compatibility and thereby the properties of the blends.

EPDM/CIIR Blends: Compatibility, Morphology and Physical Properties

A detailed study of the blends of ethylene-propylene-diene rubber (EPDM) and chlorobutyl rubber (CIIR) is proposed in this study. These blends may find application in the manufacture of curing diaphragms/curing envelopes for tire curing applications. EPDM possesses better physical properties such as high heat resistance, ozone resistance, cold and moisture resistance, high resistance to permanent defonnation, very good resistance to flex cracking and impact. Because of the low gas and moisture penneability, good weathering resistance and high thermal stability of CIIR, blends of EPDM with CIlR may be attractive, if sufficient mechanical strength can be developed. Although a lot of work has been done on elastomer blends, studies on the blends of EPDM and CIIR rubbers are meagre. Hence in this investigation it is proposed to make a systematic study on the characteristics of EPDM and CIIR rubber blends.The mechanical and physical properties of an elastomer blend depend mainly on the blend compatibility. So in the first part of the study, it is proposed to develop compatible blends of EPDM with CIIR. Various commercial grades of ethylenepropylene- diene rubber are proposed to be blended with a specific grade of chlorobutyl rubber at varying proportions. The extent of compatibility in these blends is proposed to be evaluated based on their mechanical properties such as tensile strength, tear strength and ageing resistance. In addition to the physical property measurements, blend compatibility is also proposed to be studied based on the glass transition behavlour of the blends in relation to the Tg's of the individual components using Differential Scanning Calorimetry (DSC) and Dynamic Mechanical Analysis (DMA). The phase morphology of the blends is also proposed to be investigated by Scanning Electron Microscopy (SEM) studies of the tensile fracture surfaces. In the case of incompatible blends, the effect of addition of chlorosulfonated polyethylene as a compatibiliser is also proposed to be investigated.In the second part of the study, the effect of sulphur curing and resin curing on the curing behaviour and the vulcanizate properties of EPDM/CIIR blends are planned to be evaluated. Since the properties of rubber vulcanizates are determined by their network structures, it is proposed to determine the network structure of the vulcanizates by chemical probes so as to correlate it with the mechanical properties.In the third part of the work, the effect of partial precuring of one of the components prior to blending as a possible means of improving the properties of the blend is proposed to be investigated. This procedure may also help to bring down the viscosity mismatch between the constituent e1astomers and provide covulcanization of the blend.The rheological characteristics and processability of the blends are proposed to be investigated in the last part of the study. To explore their possible applications, the air permeability of the blend samples at varying temperatures is proposed to be measured. The thermal diffusivity behaviour of EPDM/CIlR blends is also proposed to be investigated using novel laser technique. The thermal diffusivity of the blends along with the thermal degradation resistance may help to determine whether the blends are suitable for high temperature applications such as in the manufacturing of curing envelope.

Studies on Elastomer Blends with special reference to NBR/Butyl, NR/Butyl and NBR/EPDM Blends

The distribution of curing agents and fillers in the constituents of an elastomer blend is an important factor which determines the curing behaviour and vulcanizate properties of the blend. The distribution of curatives and fillers largely depends on the nature of elastomers. The curatives tend to migrate preferentially to the rubber of higher unsaturation and/or higher polarity, and reinforcing fillers tend to get distributed in the low viscosity phase, resulting in inferior mechanical properties of the blends. The thesis suggests several methods for improving mechanical properties of blends like NBR/butyl, NR/butyl, NBR/EPDM and NR/.

Compatibilisation of heterogeneous polymer blends by reactive processing

Functionalisation of polystyrene, PS, and ethylene-co-propylene-co-cyclopentadiene terpolymer, EPDM, with acrylic acid, AA, in a melt reactive processing procedure, in the presence of peroxide, trigonox 101, and coagents, Divinyl benzene, DVB (for PS), and trimethylolpropane triacrylate, TRIS (for EPDM), were successfully carried out. The level of grafting of the AA, as determined by infrared analysis, was significantly enhanced by the coagents. The grafting reaction of AA takes place simultaneously with homopolymerisation of the monomers, melt degradation and crosslinking reactions of the polymers. The extent of these competing reactions were inferred from measurements of melt flow index and insoluble gel content. Through a judicious use of both the peroxide and the coagent, particularly TRIS, unwanted side reactions were minimized. Five different processing methods were investigated for both functionalisation experiments; the direct addition of the pre-mixed polymer with peroxide and reactive modifiers was found to give optimum condition for grafting. The functionalised PS, F-PS, and EPDM, F-EPD, and maleinised polypropylene carrying a potential antioxidant, N-(4-anilinophenyl maleimide), F-PP were melt blended in binary mixtures of F-PS/F-EPD and F-PP/F-EPD in the presence (or absence) of organic diamines which act as an interlinking agent, e.g, Ethylene Diamine, EDA, and Hexamethylene Diamine, HEMDA. The presence of an interlinking agent, particularly HEMDA shows significant enhancement in the mechanical properties of the blend, suggesting that the copolymer formed has acted as compatibiliser to the otherwise incompatible polymer pairs. The functionalised and amidised blends, F and A-PSIEPDM (SPOI) and F and A-PPIEPDM (SPD2) were subsequently used as compatibiliser concentrates in the corresponding PSIEPDM and PPIEPDM blends containing various weight propotion of the homopolymers. The SPD1 caused general decreased in tensile strength, albeit increased in drop impact strength particularly in blend containing high PS content (80%). The SPD2 was particularly effective in enhancing impact strength in blends containing low weight ratio of PP (<70%). The SPD2 was also a good thermal antioxidant albeit less effective than commercial antioxidant. In all blends the evidence of compatibility was examined by scanning electron microscopy.

Tenacificação em Nanocompósitos de Poliamida 6 e Argila

Nanocompósitos de poliamida 6 (PA6) e montmorilonita modificada com sal de amônio quaternário têm sido estudados, visando melhorar as propriedades térmicas e mecânicas. De fato os efeitos da nano-escala e da interação carga-matriz resultam em maior módulo de elasticidade e resistência à tração, porém a deformação é reduzida. Assim, nesse trabalho, optou-se por adicionar elastômeros, terpolímero de etileno-propileno-dieno (EPDM) e terpolímero de etileno-propileno-dieno modificado com anidrido maleico (EPDM-MA), ao sistema PA 6/argila organofílica para recuperar os valores de deformação. Foi utilizada montmorilonita modificada com cloreto de dimetildioctadecil amônio. A intercalação por fusão foi realizada em câmara interna de mistura. Além das propriedades mecânicas, térmicas e reológicas, foram investigadas as modificações na cristalinidade da fase PA-6 em função da adição da argila modificada, EPDM e EPDM-MA, detectando-se as variações no grau de cristalinidade e nas temperaturas de fusão e cristalização. Os difratogramas de raios-x revelaram ocorrência de intercalação/esfoliação e também modificação da forma cristalina da PA 6, indicando a formação do cristal gama

Propriedades intrínsecas e de processamento de termoplásticos elastoméricos incorporando borracha de pneu reciclada

O trabalho apresentado tem por objetivo contribuir para a valorização da borracha proveniente de pneus em fim de vida, assente em princípios de sustentabilidade ambiental. A abordagem adotada para a concretização deste objetivo consiste na incorporação de borracha de pneus em formulações de base termoplástica e elastomérica (TPE), adequadas ao processo de moldação por injeção. São desenvolvidos estudos sobre a morfologia, propriedades mecânicas, térmicas e reológicas das ligas poliméricas à base de granulado de borracha de pneu (GTR). A falta de adesão entre o GTR e a matriz polimérica leva à degradação das propriedades mecânicas dos materiais obtidos. A estratégia explorada passa pela utilização de um elastómero para promover o encapsulamento do GTR e, desta forma, procurar obter ligas com propriedades mecânicas características de um TPE. São analisadas ligas ternárias (TPEGTR) compostas por polipropileno (PP) de elevada fluidez, GTR e elastómero virgem. O efeito da presença de diferentes elastómeros nas ligas é analisado neste trabalho: um elastómero de etilenopropileno- dieno (EPDM), e um novo elastómero de etileno-propileno (EPR) obtido por catálise metalocénica. O estudo da morfologia das ligas obtidas mostra haver interação entre os materiais, sendo possível inferir a viabilidade da estratégia adotada para promover a adesão do GTR. A incorporação de elastómero promove o aumento da resistência ao impacto e da extensão na rotura nas ligas, o que é atribuído, fundamentalmente, ao encapsulamento do GTR e ao aumento da tenacidade da matriz termoplástica. Com o objetivo de avaliar a influência da estrutura cristalina das ligas TPEGTR no seu comportamento mecânico, procede-se à análise do processo de cristalização sob condições isotérmicas e não isotérmicas. Neste estudo, é avaliado o efeito da presença dos materiais que constituem a fase elastomérica na cinética de cristalização. Para cada uma das ligas desenvolvidas, recorre-se ao modelo de Avrami para avaliar o efeito da temperatura no mecanismo de nucleação, na morfologia das estruturas cristalinas e na taxa de cristalização. Recorre-se à reometria capilar para estudar, sob condições estacionárias, o comportamento reológico das ligas TPEGTR. O modelo de Cross-WLF é utilizado para avaliar o comportamento reológico de todos os materiais, obtendo-se resultados similares àqueles obtidos experimentalmente. O comportamento reológico dos polímeros PP, EPR e EPDM é do tipo reofluidificante, tendo o EPR um comportamento reológico similar ao do PP e o EPDM um comportamento reo-fluidificante mais pronunciado. Em todas as ligas analisadas o comportamento reológico revela-se do tipo reo-fluidificante, sendo que a presença de GTR promove o aumento da viscosidade. Os parâmetros obtidos do modelo de Cross-WLF são utilizados para realizar a simulação da etapa de injeção recorrendo a um software comercial. Os resultados obtidos são validados experimentalmente pelo processo de moldação por injeção, evidenciando uma boa adequabilidade da aplicação deste modelo a estas ligas. O trabalho desenvolvido sobre ligas TPEGTR, constitui um contributo para a valorização da borracha proveniente de pneus em fim de vida, assente em princípios de sustentabilidade ambiental.

Effect of Blending Techniques on the Curing of Elastomer Blends

Compounding of styrene-butadiene copolymer/polybutadiene , natural rubber/ ethylene-propylene-diene terpolymer and natural rubber/butadiene-acrylonitrile copolymer blends was done in three different ways and their curing behaviour and the tensile properties of the es are compared.