Polymer formulation

Polymer sourulationCHAPTER 1INTRODUCTIONPigments ar additives in a polymer modelulation which provide countless possibilities to designers who want to several(predicate)iate their product. Legislation and rise environmental aw areness has read to the inert phasing aside of heavy metallic element in thoroughgoing fertilizer keys and subjoind usage of organic blushers. Despite their adept screw up stability, light fastness, tinctorial strength and unkept cost, certain organic rouges are wide cognize to cause signifi th beneath mugt warpage in polyethylene mouldings (even at blusher concentrations as low as 0.1% wt).1,2 This phenomenon is especially public in elephantine thin-walled mouldings much(prenominal) as lids, bottle c straddles and trays.3It is generally accepted that the warpage phenomenon is caused by the nucleating import these organic hues capture on polyethylene. They number as nucleating agents, increasing quartz glasslizinglisation rang e and altering the morpho put up downy of mouldings. Morphological replaces cause laster interior(a) stress which authorizes to deviance.2 Adding on to the job, different organic hues nucleate polyethylene to different degrees, making it impossible to aver mouldings with identical dimensions using identical bear upon conditions when a variety of pigments are used.4Numerous attempts withdraw already been do, with normally mode station success, to solve organic pigment bring on warpage. They range from adjusting swear out parameters, mould design swaps, pre-treatment of pigments, to internalization of additional additives. A review of writings in this research field of battle showed that although some studies have been conducted to investigate the incorporation of nucleating agents to override nucleating progenys of organic pigments on polypropylene, limited in geological validation of this signifier exists for polyethylene. The specific tool behind nucleating age nts overriding nucleation by organic pigments is in any case still unclear. in that respectfore, it is the aim of this research to study the influence of nucleating agents, based on potassium stearate and carboxylic deadly flavors, on the crystal and warpage behaviour of high density polyethylene containing fuzz phthalocyanine one thousand pigment. Differential S weedning Calorimetry (DSC) and ocular Microscopy (OM) leave be employed to follow the crystallizing behaviour of the material bodyulations and correlations amidst rate of crystallisation and shrinkage behaviour will also be make.CHAPTER 2LITERATURE REVIEW2.1. Nucleation and crystallization of Semi-Crystalline Polymers2.1.1. crystallisation MechanismsCrystallisation involves the makeation of an legitimate structure from a dis tell frame, such as conflate or dilute solution.5 The crystallization execute of polymers is thermodynamically driven. It is governed by change in Gibbs unload life force, G.6 G = H TS (2-1)Where H is change in enthalpy, T is compulsory temperature and S is change in south.When G is negative, crystallisation is thermodynamically well-to-do. This occurs when evil of enthalpy upon crystallization exceeds the loss of entropy multiplied by absolute temperature. It basis therefore be derived that as the absolute temperature of the system falls, the driving force of crystallisation will increase.7For a polymer to crystallise, it essential con process to the following requirements8Molecular structure must be tied(p) enough to allow coherent orderingCrystallisation temperature must be below run efflorescence but non close to starter transition temperatureNucleation must occur before crystallisationCrystallisation rate should be sufficiently highA 1 hundred percent crystallinity is non possible in polymers ascribable to factors such as kitchen range entanglements, viscous drag and branching. Thus they are termed semi-crystalline. All semi-crystallin e polymers let on a unique equilibrium unfreezeing temperature above which crystallites evanesce and below which a molten polymer starts to crystallise. The crystallisation of semi-crystalline polymers is a deuce-step process consisting crystal nucleation and crystal development.6 2.1.2. Primary NucleationPrimary nucleation can be defined as the governance of short-range ordered polymer aggregations in melt which act as a focal centre around which crystallization can occur.9 There are tercet mechanisms of primary nucleation, namely, homogenous nucleation, heterogeneous nucleation and orientation induced nucleation.102.1.2.1. homogeneous NucleationHomogeneous nucleation involves the spontaneous earthly concern of heart in a semi-crystalline polymer melt when it is cooled below its equilibrium melting temperature.7 This process is termed as compass pointic as nuclei are formed in cartridge holderly succession.11 Creation of nuclei occurs when statistical variation within a polymer melt results in the formation of ordered assemblies of chain segments larger than a critical size7 usually amidst 2-10nm.11 infra this critical size, the nuclei are un fixed and may be destroyed.11 Generally, super-cooling to mingled with 50-100C below equilibrium melting temperature is minimally required to achieve adjust homogeneous nucleation.12 The super-cooling is attributed to the energy parapet homogeneous nuclei are required to thrash to reach stability.7. When molecular segments pack next to each some other to form an embryo, there is a change in open energy, G, caused by two opposing mechanisms. The creation of tonic crystal surface increases free energy (S is negative) while the reduction in volume of the system decreases free energy ((U+pV) H is negative). The two opposing mechanisms lead to a size- restricted free energy curve which defines critical nucleus size.13 A small embryo has high surface to volume ratio and so G is corroboratory in other wo rds, crystal growth is non thermodynamically favourable.13,14 up to now as nuclei grow, the surface to volume ratio decreases up to a caput where volume change outweighs the creation of new surface and change in free energy decrease crystal growth begets increasingly probable. This point is defined as critical nuclei size and above this point, the energy barrier is overcome.13,14 Eventually when G becomes negative, nuclei are thermodynamically stable, paving the way for set ahead growth into lamellae or spherulites.14The minimum number of building block cubicles required to form a stable nuclei decrease when temperature decrease, due to a reduction in energy barrier. In other words, the rate of homogeneous nucleation increases when temperature of the polymer decreases.72.1.2.2. abstruse Nucleation In practice, ane usually observes heterogeneous nucleation and non homogeneous nucleation.15Heterogeneous nucleation involves the formation of nuclei on the surface of foreign bo dies present in the molten chassis of a semi-crystalline polymer. The foreign bodies can take the form of adventitious impurities such as dust discussion sectionicles or catalyst remnants, nucleating agents added on purpose or crystals of the same material already present in the molten phase (self-seeding).7,8 The presence of foreign bodies greatly reduces the energy barrier for the formation of stable nuclei. This reason for this is, polymer molecules which solidify against exist surfaces of foreign bodies create less new liquid/solid interface than the same volume of polymer molecules forming a homogeneous nucleus.6 In turn, critical size of nuclei is small in heterogeneous nucleation as compared to homogenous nucleation so that heterogeneous nucleation always occurs at move supercooling.16 unusual bodies with crystallographic spacings matching the semi-crystalline polymer are especially effective heterogeneous nucleating agents. Favorable nucleation sites take crystal grai n boundaries, cracks, discontinuities and cavities.72.1.2.3. Orientation-Induced NucleationOrientation-induced nucleation is caused by some degree of molecular coalescency in the molten phase of a semi-crystalline polymer. Molecular alignment reduces the entropy difference among the molten and crystalline state of the polymer. This kind of nucleation is authorized in various processes such as fibre melt-spinning, film-forming and shaft moulding. In these processes, polymer melt is sheared before and during crystallisation.8,172.1.3. Crystal Growth2.1.3.1. Primary CrystallisationPrimary crystallisation occurs when melt of a semi-crystalline polymer is cooled below its equilibrium melting temperature. It involves molecular segments depositing onto the growing face of crystallites or nuclei. The resultant crystal growth occurs along the a and b axes, relative to the polymers unit cell. These additions of molecular segments can occur through two mechanisms tight peck coterminous r e-entry or independent affirmation (illustrated in propose 2.3).6 Tight fold adjacent re-entry requires that chain stems be laid down continuously from a atomic number 53 polymer molecule in a series of hairpin bends until its length is exhausted. This atomic number 53 molecule is vista to be reeled in from surrounding molten material.7 This mechanism requires that molecular motions along the polymer molecules contour length to be several multiplication faster than the rate of crystal growth. On the other hand, the independent deposition mechanism tho requires localized motion of molecular segments. Molecular segments only need to re-organise sufficiently to align with molecular segments at the crystallite face.6tight fold adjacent re-entryindependent deposition62.1.3.2. collateral CrystallisationAfter a semi-crystalline polymer is cooled to board temperature, crystallisation is still thermodynamically favourable but restricted by the low mobility of molecular segments in it s amorphous regions. Over an extended period of time, which can span from hours to weeks, re-arrangement of molecular segments within amorphous regions can lead to further crystal growth. This process is defined as secondary crystallisation. Secondary crystallisation can take two forms either thickening of pre-existing crystallites by re-organisation of amorphous chain segments adjacent to crystallite surface or creation of new crystallites by re-organisation of amorphous chain segments in interstitial regions betwixt pre-existing crystallites. 62.1.4. Rate of CrystallisationThe crystallisation of semi-crystalline polymers is a two-step process and therefore overall crystallisation rate is governed by both nucleation rate and crystal growth rate. both(prenominal) factors are highly temperature dependent, as illustrated in invention 2.4. When temperature is just below equilibrium melting point, there exists a meta-stable region where rate of nucleation is low as nuclei that are fo rmed crack easily due to high thermal motions.8 As super-cooling increases, thermodynamic conditions become more favourable and rate of nucleation increases and reaches a maximal near the glass transition temperature. On the other hand, kinetic conditions are less favourable as super-cooling causes viscosity to increase. This results in a shift in maximum rate of crystal growth to higher temperatures where viscosity decrease is equilibrize by formation of nuclei.8,18Overall crystallisation rate at a given temperature is usually expressed as the inverse of time needed for half of the crystals to grow in the polymer (1/ t1/2).8When crystallisation occurs under isothermal conditions, its keep can be expressed by the Avrami compare8Xc(t) = 1 exp (-K.tn) (2-2)Where Xc(t) is the particle of material transformed at time t, n is the Avrami exponent and K is the Avrami rate constant.Equation (2-2) may also be written as19ln ( -ln 1-Xc(t) ) = n ln (t) + ln K (2-3)So that n and K may b e obtained by plotting ln ( -ln 1-Xc(t) ) against ln (t) n is the huckster while ln K is the y-intercept.19The prise of the Avrami exponent, n, is dependent on mechanism of nucleation and geometry of crystal growth. Theoretical values of n correspondent to different nucleation modes and crystal growth shape are tabulated in put back 2.1.19Crystal Growth ShapeNucleation ModeAvrami Exponent (n)RodHeterogeneous1Homogeneous2DiscHeterogeneous2Homogeneous3SphereHeterogeneous3Homogeneous4 prorogue 2.1 Relation between n and nucleation mode / crystal growth shape19When crystallisation occurs under constant-cooling-rate conditions, its progress can be expressed by the Ozawa equation8Xc(t) = 1 exp (-(t) / m) (2-4)Where (t) is the Ozawa rate constant, is the constant cooling rate (- T/t) and m is the Ozawa exponent.Equation (2-4) may also be written asln ( -ln 1-Xc(t) ) = m ln (t) + ln (t) (2-5)So that m and (t) may be obtained by plotting ln ( -ln 1-Xc(t) ) against ln (t) m is the slop e while ln (t) is the y-intercept.Qiu et al. feature the Avrami and Ozawa equations to make a connection between the Avrami and Ozawa exponents20log = log F(T) a log t (2-6)Where a = n/m and the kinetic function F(T) = ((t) / K)1/m. At a given degree of crystallinity, a plot of log against log t will abide a and log F(T) as the slope and y-intercept respectively.202.2. High Density Polyethylene (HDPE)2.2.1. chemic Structure, Crystallisation Rate and MorphologyHigh density polyethylene, HDPE, is a semi-crystalline polymer made up of repeat units (C2H4)n and has a general form as illustrated in Figure 2.5. It consists mainly of unbranched molecules with genuinely few defects to disrupt its linearity or hinder crystalline packing. As such, HDPE has a high rate of crystallisation, degree of crystallinity and density (0.94-0.97 g/cm3).7 Being a semi-crystalline polymer, HDPE exhibits a three-phase sound structure consisting of submicroscopic crystals surrounded by a non-crystalli ne phase comprising a partially ordered layer adjacent to the crystals and disordered material in the intervening spaces. This is illustrated in Figure 2.6.7The unit cell of HDPE, defined as the smallest arrangement of its chain segments that can repeat in three dimensions to form a crystalline matrix, is orthorhombic a cuboid with each of its axes having different lengths while the angles of adjoining faces are all 90. Each unit cell is made up of two ethylene repeat units a complete unit from one chain segment and split of four others from surrounding chain segments.7 wedge and Krim21 reported that the a, b and c axes of a polyethylene unit cell are of dimensions 7.417, 4.945 and 2.547 respectively. This is illustrated in Figure 2.7.orthogonal view,view along c-axis7HDPE unit cells pack together in a three dimensional set out to form small crystals known as crystallites. Most commonly, crystallites of HDPE take the form of lamellae crystallites with a and b dimensions that are much greater than their c dimensions. Lamellae thicknesses are usually between 50 to 200 while lateral dimensions can range from a few hundred angstroms to several millimetres. Figure 2.8 illustrates a HDPE lamella.7Various models have been proposed to explain the arrangement of molecular manacles in lamellae. They include adjacent re-entry with tight folds, switchboard, loose loops and a model with combined features (illustrated in Figure 2.9). As molecular length of HDPE is known to be many times greater than lamellae thickness, all models indicate some form of chain folding. However, they differ in their specific nature of folding.7d) composite model7In HDPE, the most common large scale-structures composed of crystalline and non-crystalline regions are known as spherulites. A spherulite consists of lamellae growing outward radially from a common nucleation site. As this growth advance into amorphous molten polymer, local inhomogeneities in concentrations of crystallisable segmen ts will be encountered. This causes the folded chain fibrils to inevitable twist and branch. As illustrated in Figure 2.10a, a spherulite will resemble a sheaf in its early stage of development. Fanning out of the growing lamellae will incidentally produce a spherical structure but true spherical residual is never achieved due to impingement of neighbouring spherulites. This growth of spherulites also involves the segregation of non-crystalline materials into regions between lamellar ribbons. Thus the overall structure of a spherulite consists of twisted and branched lamellae with polymer chains mostly perpendicular to their long axis and amorphous regions (illustrated in Figure 2.10b).222.3. innate Pigments2.3.1. Copper Phthalocyanine Pigments Copper Phthalocyanine GreenCopper phthalocyanines are a word form of organic pigments which dominate the sectors of soft and thousand coloration of polymers. This say-so can be attributed to desirable properties such as high tinctorial strength, adroit hues, excellent light and weather fastness excellent heat stability and good chemical resistance.23 In addition, in spite of its structural complexity, this class of pigments is inexpensive as they are manufactured in high yield from low cost starting materials.24The parent compound of hog phthalocyanine pigments is exceedingly easy to prepare a phthalic acid derivative is condensed with a origin of nitrogen such as urea and a cop salt such as cuprous chloride in the presence of a metal catalyst such as vanadium or molybdenum. This is usually make in organic solvents, at elevated temperatures (approximately 200C) and sometimes under increased pressure. The resultant crude copper phthalocyanine (yields of over 90%) is purified commercial-gradely by one of several processes salt attrition, solvent-free salt attrition, acid pasting and acid swelling.3,25Figure 2.11 illustrates the chemical structure of the copper phthalocyanine parent compound. It consists of a tetrabenzoporphyrazine nucleus containing a central copper atom. The planar molecule is in the form of a quadratic shape with length and thickness of 1.3nm and 0.34nm respectively.27 This parent copper phthalocyanine compound, which is characterised by unsubstituted benzene rings, is used as secular pigment. Copper phthalocyanine blue is polymorphous and exists in five crystal forms. Out of the five, the two of commercial importance are the alpha and beta forms while the other three are distorted forms.27 Different crystal forms bring about a variation in the blue feel. Alpha crystals exhibit a bright-red- musical note blue while beta crystals exhibit a super acid-shade blue.26C.I. pigment green 7, b) C.I. pigment green 36 (3y), C.I. pigment green 36 (6y)28Copper phthalocyanine green, the pigment of interest in this project, is produced from the copper phthalocyanine blue by replacing the hydrogens on the four benzene rings with halogens. Unlike its blue counterpart, where vari ation of shade is achieved by modification of crystal form, variation in the green shade is controlled by degree of chlorination or bromination. Copper phthalocyanine green only has one known crystal form.26 The two types of copper phthalocyanine green pigments are glossary index (C.I.) pigment green 7 and colour index (C.I.) pigment green 36. C.I. pigment green 7 is a blue-shade green made by introducing thirteen to fifteen chlorine atoms to replace hydrogens in the benzene ring of the copper phthalocyanine blue molecule (illustrated in Figure 2.12(a)). C.I. pigment green 36 is a scandalmongering-shade green made by gradual replacement of chlorine atoms in C.I. pigment green 7 with bromine atoms. The most brominated C.I. pigment green 36, known as 3y, has an extreme yellow shade (illustrated in Figure 2.12(c)) while the least brominated C.I. pigment green 36, 6y, has a much more bluish shade (illustrated in Figure 2.12(b)).28The outstanding tinctorial and fastness properties of b oth copper phthalocyanine green pigments allow their practise under the harshest conditions. They can be used efficaciously in masstone tints and shades down to the very palest depth. Both green pigments can be touch at temperatures in excess of 260C with little colour change. They have even better chemical and colour stability than copper phthalocyanine blues. On comparison, C.I. pigment green 7 is preferred over C.I. pigment green 36. The latter is weaker and more opaque and accounts for less than 5% of copper phthalocyanine putting green used in the polymer industry.32.3.2. Effect of Copper Phthalocyanine Green and Other Organic Pigments on Properties and Crystallisation Behaviour of Moulded PolyolefinsAlthough the combination of spectacular performance and low cost make copper phthalocyanine green ideal pigments, its use is not without challenges. It is widely known that copper phthalocyanine green and a few other pigments can cause unacceptable directs of shrinkage and war page in moulded parts of polyolefins.2,29 The problem persists even at pigment concentrations as low as 0.1% wt.2 shoplifting can be described as reduction in moulded part dimensions in reference to mould cavity dimensions.30 Warpage is a measure of out-of-plane distortion and commonly arises from the relaxation of unbalanced residual stress in a moulded part or unbalanced shrinkage in flow and transversal nidus.30The early work of Turturro et al.2 demonstrated that this shrinkage and warpage phenomenon is only limited to organic pigments. It was reported that no distortion occurred in HDPE mouldings containing inorganic pigments such as BBS red (cadmium selenide), 21 M yellow (blend of PbCrO4, PbSO4 and PbMoO4) and 500 L yellow (complex of Ni and Ti). Findings from later studies by Bugnon et al.31 and Suzuki Mizuguchi29 are in good agreement. Suzuki Mizuguchi29 reported similar observations when they incorporated inorganic pigments, TiO2, Fe2O3 and Cd Y into HDPE and PP. apply scanning electron microscopy, Bugnon et al.31 were able to show that when inorganic pigments such as CdS or CrTiO4 are incorporated into HDPE, there is no interaction between pigment surface and polymer. The polymer essentially builds a cavity around the pigment. On the other hand, an organic pigment of diketo-pyrrolo-pyrrole chemistry was rear to blend into the HDPE matrix. This led them to propose that inorganic pigments do not induce shrinkage and warpage as their chemical constitutions and polar hydrophilic surfaces have no interactions with polymers and do not influence their crystallisation behaviour.It is generally agreed that the shrinkage and warpage of polyolefins induced by copper phthalocyanine green and other organic pigments is associated with the nucleating effect these compounds have on the polymers.2,29,31 These compounds provide a foreign surface that reduces the free energy of formation of a new polymer nucleus.27 Vonk32 was one of the first few individuals who pointed out that organic pigments can act as nucleating agents for polyethylene. The nucleating effect of organic pigments on polyolefins has since been the cerebrate of intensive studies over the years. The key literature identified from this research area is that produced by Koh33 for Clariant (Singapore) Pte Ltd. Koh33 studied the influence of C.I. pigment green 7 and C.I. pigment green 36 on the crystallisation and properties of HDPE. It was reported that the high level of differential shrinkage in HDPE mouldings incorporated with copper phthalocyanine greens was come with by increased crystallisation rate, increased peak / onset crystallisation temperature and reduced spherulite size. These findings clearly indicate that copper phthalocyanine green can act as a nucleating agent for HDPE. It was also reported that increasing pigment concentration will cause an increase in crystallisation rate and level of differential shrinkage.Kohs33 findings are in line with those from simil ar studies carried out by Turturro et al.2, Suzuki Mizuguchi29 and Silberman et al.34 Turturro et al.2 observed a similar nucleating effect of copper phthalocyanine green on HDPE with the aid of depolarisation and dilatometry techniques. In addition, they found that the Avrami exponent value of HDPE decreases with increasing concentration of copper phthalocyanine green which indicates a shift in morphology, away from the spherulitic one characteristic of pure polyethylene. They proposed that the strong nucleating effect of copper phthalocyanine green causes only the development of fibrils in HDPE, which subsequently do not organise into spherulites. Interestingly, they also found that pigments do not affect the absolute level of crystallinity in HDPE implying that these compounds affect only the kinetics and not the thermodynamics of the crystallisation process.2 Suzuki Mizuguchi29 and Silberman et al.34 showed that, apart from HDPE, copper phthalocyanine green can also act as a n ucleating agent for PP. Moreover, Silberman et al.34 found that the addition of copper phthalocyanine green into PP would increase its lamellar size and decrease the activation energy (Uact) of its crystallisation process. The bill they put forward for these observations was based on the specific chemical structure of the pigment. The harmony of nitrogen in the copper phthalocyanine green molecule, with an absence of complex structures was eyeshot to promote the dynamic adsorption of PP molecules on the pigment surface and the subsequent crystallisation process. This will lead to the formation of a perfect crystal structure of large lamellar size. Together, the works from all three authors demonstrated that, at any rate copper phthalocyanine green, organic pigments of anthraquinone, perylene, quinacridone, copper phthalocyanine blue and condense azo chemistries can also act as nucleating agents for polyolefins.2,29,34At this point, with the aid of various papers, it is naturali sed that shrinkage and warpage of polyolefins induced by copper phthalocyanine green and other organic pigments are associated with these pigments serving as nucleating agents for the polymer. However the specific mechanism correlating nucleating effect and shrinkage or warpage has yet to be discussed. Both Turturro et al.2 and Suzuki Mizuguchi29 proposed the same explanation for this phenomenon. In a moulding process such as injection moulding, the quench rate is not the same at different parts of the polymer. Polymer melt in contact with mould walls crystallise and freeze very quickly, which results in crystals of low perfection with polymer chains oriented in the direction of flow. This layer of imperfect crystals in turn impedes heat exchange between polymer melt in the core regions and the mould walls. As a result, polymer melt in the core regions cool slowly and give rise to regular crystals. As the surface freezes very quickly, contraction in the core regions due to crystall isation will produce stress in the frozen outermost layer and cause distortion. In addition, relaxation of oriented regions after removal of polymer from the mould will also cause internal stress and lead to distortion. The presence of a strong nucleating agent such as copper phthalocyanine green will limit the time available for oriented chains to recover during cooling and also increase the thickness of the skin layer. Both factors will lead to more pronounced distortion.2,29Apart from altering the shrinkage and warpage behaviour of polyolefins, the nucleating effect of copper phthalocyanine green and other organic pigments is thought to also have a marked influence on the mechanical properties of polyolefins. An investigation of how certain organic pigments affect the mechanical properties of HDPE was undertaken by Lodeiro et al.1 They found that tested pigments, copper phthalocyanine blue and irgalite yellow do affect the fountainhead mechanical properties of HDPE. In partic ular, it was observed that the presence of small amounts of phthalocyanine blue in HDPE is sufficient to cause an increase in ductility, reduction in Youngs modulus (up to 10%), reduction in yield stress and increase in stroke strain. They attributed these consequences to smaller and more numerous spherulites induced by the pigment smaller spherulites in larger numbers, each surrounded by amorphous material, results in a polymer that will deform more readily and have lower yield stress and higher failure strain.2.4. Nucleating Agents2.4.1. Heterogeneous Nucleation of Polyethylene Nucleating Agents establish on Potassium Stearate and Carboxylic Acid SaltsNucleating agents have traditionally been added to semi-crystalline polymers to conjure processing and end product characteristics. The incorporation of these compounds results in shorter cycle time as they increase the crystallization rate of semi-crystalline polymers, ensuring faster solidification from the melt upon cooling. The ir addition also results in the formation of smaller spherulites in semi-crystalline polymers. This change in spherulite size improves mechanical properties (such as tensile strength, hardness and modulus) and ocular properties (such as haze and transparency).8,35Polyethylene, and in particular high density polyethylene, has an super fast rate of crystallization, which makes it very hard to nucleate.8,35 This is probably the reason wherefore little has been published on its nucleating agents. That being said, a handful of nucleating agents have been identified to date. Together, the works of Solti et al. and Ge et al. showed that benzoic acid, talc and Na2CO3 can effectively nucleate polyethylene.8 Besides the use of particulate or low molecular weight nucleating agents, polyethylene can also be nucleated by epitaxial crystallization on another polymer substrate. Loos et al. was able to demonstrate the melt crystallisation of LLDPE on oriented HDPE.8Potassium stearate is another nucleating agent tha