Low heat distortion temperature

It is thus seen that as a class the primarily aliphatic amines provide fast-curing hardeners for use at room temperatures. With certain exceptions they are skin sensitisers. The chemical resistance of the hardened resins varies according to the hardener used but in the case of the unmodified amines is quite good. The hardened resins have quite low heat distortion temperatures and except with diethylenetriamine seldom exceed 100°C. The number of variations in the properties obtainable may be increased by using blends of hardeners. 

Mechanical properties are typical of a rigid plastics material and numerical values (Table 30.2) are similar to those for poly(methyl methacrylate). Although thermosetting, it has a low heat distortion temperature ( 80°C) and is not particularly useful at elevated temperatures. 

It has a low heat distortion temperature (85°C) and, hence, articles made of it cannot be sterilised with steam, yellowing and cracking of the polymer on outdoor exposure is another main drawback. 

Poly(trimethylene terephthalate). Poly(trimethylene terephthal-ate) (PIT) is a crystalline polymer that is used for fibers, films, and engineering plastics. The polymer has an outstanding tensile elastic recovery, good chemical resistance, a relative low melting temperature, and a rapid crystallization rate. It combines some of the advantages of poly(ethylene terephthalate) (PET) and poly(butylene terephthalate) (PBT). Disadvantageous are the low heat distortion temperature, low melt viscosity, poor optical properties, and pronounced brittleness low temperatures. 

Although it is thermosetting it has a low heat distortion temperature and is not particularly useful at elevated temperatures. 

The material therefore readily absorbs moisture and must be effectively dried prior to moulding, otherwise a hazy or milky appearance may result. Polyacrylonitriles have a relatively low heat distortion temperature (around 75°C), hence they have limitations for products requiring a hot fill. The material is suitable for thermoforming operations but its relatively high moisture permeation is likely to restrict ultimate usage. The presence of acrylonitrile residues also placed the material under a cloud with the FDA, but use is now accepted provided acrylonitrile monomer does not exceed 0.1 ppm. Nitrile copolymers are usually copolymerised with methyl acrylate together with small quantities of butadiene/acrylonitrile rubbers. 

PVC, however, suffers from an inherent susceptibility to thermal degradation and hence must invariably be processed with heat stabilizers and careful control of processing temperature. The other important drawbacks of PVC are its brittleness in the absence of a plasticizer (low notched Izod impact strength) and its low heat distortion temperature (ca. 60°C) originating from its low glass transition temperature and essentially... 

It can be observed from Fig. 11.2 that the elongation at break of PLA is lower than PS indeed, proving that it is more brittle than PS. Thus, although biopolymers such as PLA have great commercial potential to substitute conventional petroleum based polymers, but some of the properties such as brittleness and low heat distortion temperature had restrict their use in a wide-range of applications. 

High research activity is dedicated to overcome typical weaknesses of PLA -low impact strength and low heat distortion temperature and to develop tailor-made PLA grades in order to serve special applications. These activities will conquer new niches for PLA and will help to increase PLA consumption at high velocity. 

PA 6,12 51 1.4 300 7 0.04 Low water absorption, detergent resistance and elongation at break Low heat distortion temperature, dissipation factog flammability, flexural modulus... 

These resins have many of the same features of polyethylene plus high transparency, tenacity, reliance, and increased resistance to oils, greases, and solvents. Commercial ionomers are nomigid, unplasticized plastics. Outstanding low-temperature flexibility, resilience, high elongation, and excellent impact strength typify the ionomer resins. Limitations of ionomers include low stiffness, susceptibility to creep, low heat distortion temperature, and poor ultraviolet resistance unless stabilizers are added. Most ionomers are very transparent. 

An additional advantage is that these coatings may be used on materials with low heat-distortion temperatures as well... 

Ingeo PLA is easily processable and suitable as amorphous biopackaging material as a result of its relatively high meso-lactide content. The downside is the poor resistance to elevated temperatures (low heat distortion temperature, HDT) during transportation, storage, and use of articles produced from this bioplastic. mc o-Lactide— which contains an L- and a D-isomer—is an unavoidable side product of lactide production and must be separated from L- and D-lactides of high stereochemical purity. 

An essential requirement for medical products is that the materials and components used must be sterilizable. Once the sterilization method has been established, the list of materials that are suitable for a medical product is already limited. For certain sterilization processes, plastics cannot be used because of their low heat distortion temperature, low hydrolysis resistance, or low resistance to color change and degradation of the molecular chains. 

Presently, PLA and other biopolyesters suffer from two important deficiencies that limit their use, of which the first is the low heat distortion temperature. The second is their relatively high permeabilities toward a number of substances, pmticularly water. Recently, copolymerization of cellulose acetate with PLA, both originating from renewable resources, resulted in a material with increased heat distortion temperature (200). In addition, nanocomposite technologies hold promise for improving both temperature distortion and permeation characteristics, as they have in conventional plastics. 

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