Ethylene-propylene copolymers crosslink density

PVC, another widely used polymer for wire and cable insulation, crosslinks under irradiation in an inert atmosphere. When irradiated in air, scission predominates.To make cross-linking dominant, multifunctional monomers, such as trifunctional acrylates and methacrylates, must be added. Fluoropolymers, such as copol5miers of ethylene and tetrafluoroethylene (ETFE), or polyvinylidene fluoride (PVDF) and polyvinyl fluoride (PVF), are widely used in wire and cable insulations. They are relatively easy to process and have excellent chemical and thermal resistance, but tend to creep, crack, and possess low mechanical stress at temperatures near their melting points. Radiation has been found to improve their mechanical properties and crack resistance. Ethylene propylene rubber (EPR) has also been used for wire and cable insulation. When blended with thermoplastic polyefins, such as low density polyethylene (LDPE), its processibility improves significantly. The typical addition of LDPE is 10%. Ethylene propylene copolymers and terpolymers with high PE content can be cross-linked by irradiation. ... 

The curing of polyesters, ethylene-propylene copolymers, and for the grafting of styrene onto elastomeric polymer chains, benzoylperoxide is used. High density polyethylene (HDPE) is crosslinked in the presence of 2,5-dimethyl-2,5-di( -butylperoxy)hexyn-3. Crosslinking is achieved by electrons, y-rays or UV irradiation, and enhanced by the presence of methyl ether of benzoin. 

The modified fillers were used in two matrices with different polarity the ethylene-propylene copolymer EPM and hydrogenated acrylonitrile-butadiene rubber HNBR. Elastomers were crosslinked with dicumyl peroxide DCP. The influence of the variously modified fillers on the cross-linking density of the vulcanizates, rheometric and mechanical properties of filled systems were investigated. The ageing studies (thermal, atmospheric and under UV radiations) were conducted. 

Ethylene propylene copolymers (EPM) are made by Ziegler-Natta and metallocene polymerization and are the commercial mbbers with the lowest density. EPM cannot be vulcanized and thus is not reactive to peroxide curing. To introduce an unsaturated site suitable for crosslinking, a non-conjugated diene termonomer such as ethylidene norbomene, 1,4 hexaadiene or dicyclo-pentadiene, is employed to produce the mbber known as EPDM. Ethylene propylene diene mbber has small number of double bonds, external to the backbone, introduced in this way. In EPDM, the E stands for ethylene, the P for propylene, the D for diene and the M indicates that the mbber has saturated chain of the polymethylene type, properties of EPM and EPDM are ... 

The majority of these systems are crosslinked, so are thermosets. The term thermoplastic vulcanisates (TPV) is also used (a.8). Copolymers are made from ethylene, propylene and a small fraction of unsaturated diene, so allowing the crosslinking of the foam. Eor applications such as mouse mats, the foam density is... 

A review is presented of the nitrogen autoclave process for the manufacture of crosslinked polyolefin foams. Process and product developments over the last few years are summarised and future possibilities are described. Process developments include use of higher temperatures and pressures to produce foams having densities as low as 10 kg/cub.m. Product developments include foams based on HDPE/LDPE blends, propylene copolymers and metallocene-catalysed ethylene copolymers. The structure and properties of these foams are compared with those of foams produced by alternative processes. 5 refs. 

A base polymer, such as an ethylene-propylene (EP) copolymer, can be acquired in a range of compositions, molecular weights, various ethylene-to-propylene ratios, various molecular weight distributions, and a range of densities. Each of these variations results in a base polymer that has specific practical properties such as flexibility, elastic recovery, tensile strength and thermal limit to name a few. As a base polymer, ethylene-propylene polymers and most other non-crosslinked elastomers have no significant commercial application, since they are essentially a liquid with veiy high viscosity. 

The objects of our investigations were four kinds of elastomers, of different structure and polarity, viz. cis-1,4-polybutadiene (BR)> butadiene-acrylonitrile copolymer (NBR), isobutylene-isoprene copolymers (IIR) and ethylene-propylene-diene terpolymer (EPT). They were mixed with plastomers low density polyethylene (PE] ), polystyrene (PS), polytetrafluoroethylene (PTFE), polyvinyl chloride (PVC), polycaproamide (PCA) and polyacrylonitrile (PAN) (Table 1). The concentration of the plastomers in the mixtures was changed in the range from 0 to 50 pph of the elastomer. The polymers were blended at temperature T = 423 K by means of the micromill of the Plasti--Corder apparatus. After 24 hours, crosslinking substances, dicurayl peroxide (DCP) or sulphur and diphenylguanidine (S, DPG), were added at room temperature. The composition of the mixtures is given in Table 2. 

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