Films properties

This chapter covers many of the most important properties measured by producers of blown film. These include mechanical, thermal, optical, physical, electrical, and rheological. The first five in this list apply primarily to the extruded film and the last one applies to the molten polymer inside the extruder and die. By obtaining the measurement values for these properties, manufacturers gain assurance that their resin or film will perform adequately, whether during manufacture (extrusion or conversion) or in final product form as used by the customer. 

Tests for resin and film property values can be performed in-house, by an outside testing facility, or by a supplier. There are advantages and disadvantages to each. The most important consideration is the accuracy of the data collected. After that, consideration must be given to costs associated with the amount of data needed (equipment, consumables, training, labor, etc.) and the frequency of measurement required. 

To suitably compare measurement values obtained at different times or locations, there must be assurance that the tests were performed under identical conditions. To accomplish this, a committee of experts in each particular subject area develops standardized test methods. The methods establish the exact conditions for all test parameters by all parties conducting tests to measure the property of interest. A major publisher of test methods covering polymer resins and plastic films is the American Society for Testing and Materials (ASTM), West Conshohocken, PA, USA. In this chapter, ASTM method reference numbers are included in parentheses at the beginning of each property description section. 

The following properties relevant to blown film processing comprise the main sections in this chapter  

Tensile strength Elongation Tear strength Impact resistance 

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As the safety and quality of industrial components, equipments and constructions is correlated with the inspection sensitivity and this is influenced in radiography by the film system class, a continuous supervision of the film systems on the market seems to be urgently necessary. To support the confidence of the film users in the film properties specified by the film manufacturers such a system for quality assurance for industrial x-ray films is proposed by some manufacturers and BAM. This system will be open to all manufacturers, distributers and users of x-ray films. It will deal with all film systems inclusive those which are not specified by a manufacturer as for instance mixed systems. The system for quality assurance will be based... 

The technological importance of thin films in snch areas as semicondnctor devices and sensors has led to a demand for mechanical property infonnation for these systems. Measuring the elastic modnlns for thin films is mnch harder than the corresponding measurement for bnlk samples, since the results obtained by traditional indentation methods are strongly perturbed by the properties of the substrate material. Additionally, the behaviour of the film under conditions of low load, which is necessary for the measnrement of thin-film properties, is strongly inflnenced by surface forces [75]. Since the force microscope is both sensitive to surface forces and has extremely high depth resolntion, it shows considerable promise as a teclnhqne for the mechanical characterization of thin films. 

Vinyl acetate (VA)/crotonates copolymer became available in the late 1950s. It was the first polymer used in fixatives to contain carboxyHc acid groups which, depending on neutralization percent, could produce variations in film properties eg, stiffness, humidity resistance, resiUency, tack, and removabihty by shampoo. It has largely been replaced in hair sprays by newer polymers. 

VA/crotonates/vinyl neodecanoate copolymer is the most used polymer in aerosol hair sprays (ca 1993). Like its precursor above, it has free carboxyhc acid groups which can be neutralized to give various film properties. Recommended neutralizing agents include aminomethyl propanol, ammonium hydroxide, and dimethyl stearamine. Recommended percent neutralization is 90%, but products can be found in the 80—110% range. 

Polyphenylquinoxalines (PPQ) are easier to make than the polyquinoxalines and offer superior solubiHty, processibiHty, and thermooxidative stabiHty (65). The PPQs exhibit excellent high temperature adhesive, composite, and film properties. However, to increase the use temperature of PPQs, acetylene... 

E. Pugh and T. O. Mohr, Thin Films Properties of Ferromagnetic Films, ASM, Metals Park, Ohio, 1963, Chapt. 7. 

Table 8. Film Properties of Two Types of HDPE with Different MWDs...

Table 6. Film Properties of Standard Ethylene—1-Hexene LLDPE and a Resin with Improved Mechanical Properties ...

The pelargonic acid by-product is already a useful item of commerce, making the overall process a commercial possibiUty. The 13-carbon polyamides appear to have many of the properties of nylon-11, nylon-12, or nylon-12,12 toughness, moisture resistance, dimensional stabiUty, increased resistance to hydrolysis, moderate melt point, and melt processibiUty. Thus, these nylons could be useful in similar markets, eg, automotive parts, coatings, fibers, or films. Properties for nylon-13,13 are = 56 (7 and = 183 (7 (179). 

The state-of-the-art i -Si H films (Table 3) are deposited at the rate of 1—3 A/s with the gas utilization rate on the order of 15%. Larger gas utilization rates, hence larger deposition rates, usually result in inferior properties than those indicated in Table 3. Increasing the deposition rate by merely increasing the power leads to dust formation. The use of higher excitation frequency can lead to deposition rates in excess of 15 A/s and still give relatively good film properties (7). 

Concurrent bombardment during film growth affects film properties such as the film—substrate adhesion, density, surface area, porosity, surface coverage, residual film stress, index of refraction, and electrical resistivity. In reactive ion plating, the use of concurrent bombardment allows the deposition of stoichiometric, high density films of compounds such as TiN, ZrN, and Zr02 at low substrate temperatures. 

Thin films formed by atomistic deposition techniques are unique materials that seldom have handbook properties. Properties of these thin films depend on several factors (4), including substrate surface condition, the deposition process used, details of the deposition process and system geometry, details of film growth on the substrate surface, and post-deposition processing and reactions. For some appHcations, such as wear resistance, the mechanical properties of the substrate is important to the functionaHty of the thin film. In order to have reproducible film properties, each of these factors must be controUed. 

Table 19. Film Properties of Vinylidene Chloride Copolymer Latex ...

Blends. Latex film properties are commonly modified through the blending of latexes, eg, a "soft" polymer is made slightly harder by blending with a "hard" latex. 

Cellulose esters of aromatic acids, aUphatic acids containing more than four carbon atoms and aUphatic diacids are difficult and expensive to prepare because of the poor reactivity of the corresponding anhydrides with cellulose Httle commercial interest has been shown in these esters. Of notable exception, however, is the recent interest in the mixed esters of cellulose succinates, prepared by the sodium acetate catalyzed reaction of cellulose with succinic anhydride. The additional expense incurred in manufacturing succinate esters is compensated by the improved film properties observed in waterborne coatings (5). 

PZN-PT, and YBa2Cug02 g. For the preparation of PZT thin films, the most frequently used precursors have been lead acetate and 2irconium and titanium alkoxides, especially the propoxides. Short-chain alcohols, such as methanol and propanol, have been used most often as solvents, although there have been several successful investigations of the preparation of PZT films from the methoxyethanol solvent system. The use of acetic acid as a solvent and chemical modifier has also been reported. Whereas PZT thin films with exceUent ferroelectric properties have been prepared by sol-gel deposition, there has been relatively Httle effort directed toward understanding solution chemistry effects on thin-film properties. 

Despite the considerable progress made in the few years in which anodic insertion/extraction films have been known, neither film compositions, film properties, nor electrochemical reactions are sufficientiy well characterized. There have been disagreements, as indicated for h-IrO and h-NiO in Table 2, as to whether is being extracted or OH inserted during coloration. The general problem is best illustrated by the important example of Pmssian blue. Early work (47—50) resulted in two different sets of equations for electrochromic reduction ... 

A water-reducible coating or resin is one that is diluted with water before use. Water-reducible alkyds give comparable drying performance to solvent-bome alkyds. However, they are not widely used because film properties tend to be poorer than those of solvent-bome alkyds, especially in air-dry systems (26). This is pardy because of alcoholysis of the alkyd by primary alcohols such as 1-butanol [71-36-3] C H qO, a common solvent in water-reducible alkyds (27,28) secondary alcohols such as 2-butanol [78-92-2] C qH O, minimize this problem (27). In any case, the slow loss of amine or ammonia leads to short-term high sensitivity to water. Even in the fully dry films, the presence of unreacted carboxyHc acid groups leads to films having comparatively poor water resistance limiting their usehilness. 

The film properties required for some appHcation can only be deterrnined by the performance of the appHed coating in practice. Because requirements and exposure conditions vary widely, devising laboratory tests to predict film performance is difficult and frequendy not possible. Data banks of actual field performance as functions of coating compositions, appHcation variables, and environmental factors can be very usehil. 

Dynamic mechanical thermal analysis has become a powerful tool for the assessment of cure and the study of the effect of extent of sure on film properties and performance (133,134). 

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