FIELD OF THE INVENTION

The present invention relates to a natural based eco-friendly plasticizer for poly( vinyl chloride) (PVC). In more particular, the present invention relates to the use of medium-chain-length poly(3-hydroxyalkanoates) (mcl-PHA) as a natural based eco- friendly plasticizer for PVC.

BACKGROUND OF THE INVENTION PVC is an amorphous thermoplastic. Due to the presence of chlorine atoms, it has a significant polarity within the polymer molecule structure. Generally, additives such as plasticizers, thermal stabilizers, lubricants, pigments and fillers are added to the PVC resin during processing to improve the overall performance of the product. Plasticizers in particular are added to change the moldability of PVC and provide desired flexibility to the end products. By adding in different levels of plasticizers, PVC products could be formulated with physical properties ranging from rigid to flexible. PVC without any plasticizers are called rigid PVC while PVC that include plasticizers are called flexible PVC (PVC Fact Book, 2008).

Generally, the key performance properties of a PVC compounds are influenced by the chemical type of plasticizer as well as the plasticizer level (part per hundred of PVC). Various types of plasticizers give various plasticization effects due to the differences in the strengths of plasticizer-plasticizer and plasticizer-polymer interactions. At low plasticizer levels, the plasticizer-PVC interactions are the dominant interactions, while at high plasticizer concentrations, plasticizer-plasticizer interactions become more significant (Krauskopf and Godwin, 2005). In formulations at higher level of plasticizers, some leaching out of excess plasticizers to the polymer surface would be occurred. This is because plasticizing effect will ultimately reach constant once the critical point of plasticizer concentration is passed, where further addition of the plasticizer may lead to an inhomogeneous mixture of the PVC compound. Phthalic acid esters, generally known as phthalate plasticizers are the predominant type of PVC plasticizer produced in the world and accounted for almost 86% of world consumption of plasticizers in year 2008 (Bizzari, 2009). However several issues regarding the use of phthalates were raised recently, concerning about the effects of phthalates on the environment, human hormones and reproductive system as well as their exposures to children via breast milk, toys and baby care products. Based on a study in Norway, the bronchial obstruction in children was directly related to the amount of plasticizer-releasing materials present in the indoor environment (Plastermart, April 2008). According to Bornehag et. al. (2005), plasticizers that present in the dust are the main elements causing allergy, asthma and inducing puberty among the children since they spent most of the time in indoor. There was a study conducted in the same year showing that phthalates actually mimicked female hormones and could serve as the endocrine disruptors in human body, resulting in feminization of boys. Research also showed that phthalates were shown to be responsible of cancer proliferation in mice and rats. These phthalate-based plasticizers are found to be harmful to human beings when direct contact with skin and tissues. They have the risk of leaching out from PVC compounds during end-used applications, to the environment or human body. Therefore, alternative greener plasticizer materials which impart low toxicity, total or partial biodegradability and are economical and technical viable to substitute those conventional petrochemical based plasticizers are required.

Therefore, the present invention has developed a bacterial origin polymeric and oligomeric forms of mcl-PHA to replace conventional petrochemical based plasticizers as a natural based eco-friendly plasticizer for PVC.

SUMMARY

An object of the present invention is to provide a bacterial origin polymeric and oligomeric forms of mcl-PHA as natural based eco-friendly plasticizer for PVC. The mcl-PHA plasticized PVC products have the potential to be used in applications related to health safety concerns. For example, medical products used in direct contact with skin and tissue e.g. blood transfusion bags, intravenous fluid bags, drip lines; toys which may be chewed or sucked by young children; food wear and containers; films and packaging; flooring and wall-covering

Another object of the present invention is to provide a process to produce a bacterial origin polymeric and oligomeric forms of mcl-PHA as a natural based eco-friendly plasticizer for PVC.

The further object of the present invention is to provide the use of a bacterial origin polymeric and oligomeric forms of mcl-PHA as a natural based eco-friendly plasticizer for PVC.

These and other objects, features and advantages of the present invention will be readily apparent from the following description. BRIEF DESCRIPTION OF THE DRAWING/FIGURES

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention.

Figure 1 : Molecular structure of monomer units of (a) PHAsp _K o and (b) PHAOA; X: 1, 3, 5, 7 and 9.

Figure 2: SEM micrograph showing surface morphology of PVC. Voids and cavities were present in the PVC film (500 x magnification).

Figure 3: SEM micrographs showing surface morphology of (a) PSP2.5, (b) PSP ₅ , (c) PdegSP ₂ . ₅ , (d) PdeSP ₅ films (500 x magnification). Figure 4: SEM micrographs showing surface morphology of (a) POA2.5, (b) POA5, (c) PdeOA ₂ . ₅ and (d) PdeOA ₅ films (500 x magnification). Figure 5: FTIR absorption spectra of (a) PVC, PHA _SPf co and PSP; (b) PVC, degPHAsP _K o and PdeSP; (c) PVC, PHA _OA and POA; (d) PVC, degPHA _OA and PdeOA.

Figure 6: FTIR absorption spectra of (a) PVC, PHA _S PKO and PSP; (b) PVC, degPHAsPKo and PdeSP; (c) PVC, PHA _OA and POA; (d) PVC, degPHA _OA and PdeOA, in the region 1135 to 1350 cm ^'1 .

Figure 7: 1H-NMR spectra of (a) PVC, (b) PHA _0A , (c) POA ₂ . ₅ and (d) POA ₅ . Figure 8: Loss modulus vs. temperature curves of (a) PVC, PSP _{2 5} and PSP ₅ ; (b) PVC, PdeSP ₂ . ₅ and PdeSP ₅ ; (c) PVC, POA _{2 5} and POA ₅ ; (d) PVC, PdeOA _{2 5} and PdeOA ₅ .

Figure 9: Temperature variation of log storage modulus for (a) PVC, PSP2.5 and PSP ₅ ; (b) PVC, PdeSP ₂ .s and PdeSP ₅ ; (c) PVC, POA _{2 5} and POA ₅ ; (d) PVC, PdeOA _{2 5} and PdeOAj.

Figure 10: Temperature variation of film's stiffness for (a) PVC, PSP2.5 and PSP ₅ ; (b) PVC, PdeSP ₂ . ₅ and PdeSP ₅ ; (c) PVC, POA2.5 and POA ₅ ; (d) PVC, PdeOA _{2 5} and PdeOA ₅ .

DETAIL DESCRIPTION OF THE PRESENT INVENTION

In the following detailed description, reference is made to various specific embodiments in which the invention may be practiced. These embodiments are described with sufficient detail to enable those skilled in the art to practice the invention and it is to be understood that other embodiments may be employed and that structural and logical changes may be made without departing from the spirit or scope of the present invention.

Mcl-PHA are natural polyesters of hydroxyl fatty acids comprised of 6 to 14 carbon atoms length monomers, which are primarily synthesized by fluorescent pseudomonads under nutrient imbalance, as carbon and energy storage compounds. In the present invention, mcl-PHA were produced by bacterial namely Pseudomonas putida PGAl using oleic acid (OA) and saponified palm kernel oil (SPKO) as carbon source in shake flasks fermentations.

As natural polyesters, mcl-PHA owns the biodegradable, biocompatible and non-toxic properties and thus fulfill all the desirable traits of an alternative plasticizer material. Besides, instead of over-dependent on non-renewable petrochemical resources, mcl- PHA can be synthesized from natural renewable resources such as plant oil, fatty acids and agricultural wastes. As mcl-PHA is polar polyester possess polar ester groups and functional end groups e.g. hydroxyl and carboxyl group, it has the great potential to act as compatible plasticizer for PVC to improve the physical properties of the polymer. In addition, possible entanglement between the polymeric and oligomeric polyhydroxyalkanoates (PHA) with the PVC does not allow easy migration of the plasticizers out of the blend compounds. This is different from the conventional petrochemical -based plasticizers which are small molecules that intercalates into PVC and thus may have limited residence time in the PVC compound. In the event of accidental or natural migration from the blend compounds, the PHA plasticizers would not be hazardous to human ^health and the environment due to their non-toxic, biodegradable and biocompatible properties.

The potential of mcl-PHA to be a plasticizer for PVC is due to the presence of high number of polar as well as non-polar groups in PHA. The polar groups could have dipole-induced dipole interaction with the PVC, which would lead to good miscibility between the two polymers. The long chains of non-polar pendant groups in PHA can cause reduction in polar forces between the PVC chains, thus allowing the chains to glide past each other much easily. This would, in effect, lower the T _g and improve the physical properties of PVC. Both polymeric and oligomeric forms of mcl-PHA are viewed to be compatible with PVC as they may have sufficient affinity towards the PVC resin due to the specific interactions between the H ^a and chlorines of PVC with the carbonyl, carboxylic and hydroxyl groups of PHA. The mcl-PHA could be dispersed in the PVC polymer matrix, space apart the PVC polymer chains and reduced the PVC-PVC interactive forces. Therefore, mcl-PHA could be used as natural-based plasticizer for PVC. The thermal behavior and stability of PVC mixed with low concentrations of mcl-PHA is also a vital parameter to determine the plasticizing and thermal effect of PHA on PVC.

A series of solution-cast blends of PVC with low concentration of mcl-PHA (2.5 and 5 phr) were prepared to assess whether mcl-PHA and its oligoesters could be acted as compatible plasticizers for PVC. SEM, FTIR, Ή-NMR, DSC and DMA were conducted to study the microstructure, film morphology, miscibility and viscoelastic properties of the PVC-PHA blends. SEM micrographs of PVC/PHA films showed that plasticization of PVC involved the PHA penetrated in some of the porous structures of PVC and interfused with PVC polymer segments. Both FTIR and Ή- NMR spectroscopic analyses suggested the PVC-PHA miscibility was possibly due to the specific interactions between the ester C=0 group of PHA with the ^a H and local dipoles of chlorines of PVC. TGA study was used to investigate the thermal behavior and stability of the plasticized PVC films. Both measurements of DSC and DMA gave consistent results of a single and lower T _g for the blends, indicating that mcl-PHA was highly miscible with PVC. Results from DMA also showed that mcl-PHA and its oligoesters could impart elasticity to the PVC compounds and therefore decreasing the stiffness of the polymer.

The following example serves to illustrate the invention but it will be appreciated that the invention is not limited to this example:

EXAMPLE

Materials

Polyvinyl chloride) (PVC) (BDH laboratory reagent) with viscosity number 87 and molecular weight of approximately 100,000 g mol ^"1 was used throughout the experiments. Mcl-PHA synthesis.

Mcl-PHA were synthesized by Pseudomonas putida PGA1 from two different carbon substrates: oleic acid (OA) and saponified palm kernel oil (SPKO) at 0.5% (v/v and w/v, respectively) in shake flasks fermentation. The shake flasks fermentation was conducted in the orbital shaker incubator at 30 °C and 200 rpm throughout the experiments. PHA production was performed in a two-stage culture system, which consisted of cell-growth and PHA-accumulation phases. In the first phase, the bacteria were grown in 8.0 g L ^"1 nutrient broth, a nutritionally rich medium, to produce high concentration of cells. After 20 hours of incubation, the cells were harvested and transferred to the modified nitrogen-limited M9 medium which contained 12.8 g L ^"1 Na ₂ HP0 ₄ .7H ₂ 0, 3.0 g I/ ¹ KH ₂ P0 ₄ , 0.5 g L ^"1 NH ₄ C1, 0.5 g L ^"1 NaCl and trace elements consisted of 2.0 ml of 1.0 M MgS0 ₄ 7H ₂ 0 stock solution and 1 ml of 0.1 M CaCl ₂ stock solution. The bacteria were further cultivated in PHA production medium for 72 hours under aerobic condition. The cells were then harvested and PHA were extracted by chloroform. Pure PHA polymers were obtained by repeated precipitation of PHA/chloroform in chilled methanol.

Thermal degradation of mcl-PHA

The polymeric mcl-PHA were heat-treated at 170 °C for both OA-derived mcl-PHA (PHAOA) and SPKO-derived mcl-PHA (PHA _S PKO) The temperature was chosen as the degradation temperature since the heat-treated PHA (degPHAo _A and degPHAsp _K o) obtained were mainly composed of a mixture of oligomeric hydroxyacid fragments without terminal unsaturated fragments. Polymer samples were first pre-dried for 24 hours in vacuo. The samples were placed in 250 ml Erlenmeyer flask connected with a Liebig condenser. The reaction flask was placed in a silicon oil bath and heated from ambient temperature to 170± 2 °C. The level of the oil bath was kept at least 2 cm above the sample in the reaction flask to allow for temperature equilibration during heating. The sample was then kept under isothermal condition for 30 minutes. The reaction flask was removed from the oil bath after the heating was completed and allowed to cool down to room temperature. The heat-treated PHA in the flask was collected by dissolving it in a small amount of chloroform followed by complete solvent evaporation at room temperature in fume hood. Preparation of PVC/PHA polymer blends

A series of polymer blends comprised of PVC and different types of mcl-PHA (PHAOA, PHASPKO, degPHAoA and degPHAspKo) were prepared by using a common solvent, chloroform (CHC1 ₃ , M _w 119.38 g mol ^"1 , analytical grade, Merck). The PVC/chloroform solution was prepared by dissolving 5.0 g PVC in 100 mL chloroform while the PHA/chloroform solutions were prepared in two concentrations (0.125 g and 0.25 g mcl-PHA respectively in 20 mL chloroform). When the PVC solution was mixed with the PHA solution and the chloroform was evaporated, blends containing respectively 2.5 and 5 parts PHA per hundred parts PVC were obtained. The PVC/PHA blends were designated as following: POA _{2 5} and PdeOA _{2 5} (blends of 2.5 parts polymeric and oligomeric PHAOA with 97.5 parts PVC, respectively). PSP _{2 5} and PdeSP ₅ (blends of 2.5 parts polymeric and oligomeric PHASPKO with 97.5 parts PVC, respectively). POA ₅ and PdeOA (blends of 5 parts polymeric and oligomeric PHAOA with 95 parts PVC, respectively). PSP ₅ and PdeSP ₅ (blends of 5 parts polymeric and oligomeric PHASPKO with 95 parts PVC, respectively).

The PVC/chloroform solution was first mixed at 500 rpm, refluxed at 55 °C for 30 minutes. Then, the PHA solution was added to the PVC solution and the mixture was stirred at 500 rpm, 55 °C for one hour. The reaction flask was placed in a thermostated water bath and the level of the water was kept at least 2 cm above the level of the solution in the flask for homogeneous temperature distribution. Subsequently, the PVC/PHA solution was poured into a glass petri dish and stirred using a magnetic stirrer bar to slowly evaporate off the solvent in the fume hood at room temperature. When the mixture started to form a viscous solution, the magnetic stirrer bar was removed and drying via evaporation was continued until a homogenous film was obtained. The casted films were further dried under vacuum at 60 to 70 °C for two days followed by one week of drying in a hot air oven at 70 to 72 °C to remove the solvent traces.

Gas Chromatography (GC)

Monomer composition for the polymeric and oligomeric PHA was analyzed using a gas chromato graph model GC 2014 Shimadzu (Japan). 1.0 μΐ of methanolyzed PHA sample was injected by split injection with a split ratio of 10: 1 using a SGE 10.0 μΐ syringe. Nitrogen was used as the carrier gas at a flow rate of 3 ml min ^"1 . The column oven temperature was programmed from 120 °C for 2 min at the start, ramped up at a rate of 20°C min ^"1 to 230 °C and held at this temperature for 10 min. The temperatures of injector and detector were set at 225 °C and 230 °C, respectively. 3- hydroxyalkanoic acid methyl ester standards: 3-hydroxybutyric acid, 3- hydroxyhexanoic acid, 3-hydroxyoctanoic acid, 3-hydroxydecanoic acid, 3- hydroxydodecanoic acid, 3-hydroxytetradecanoic acid and 3-hydroxyhexadecanoic acid methyl esters (Larodan) were used to determine the respective retention times for monomer identification.

Gel Permeation Chromatography (GPC)

The number average molecular weight ( „), weight average molecular weight (M _w ) and polydispersity index (PDI) of the polymeric and oligomeric mcl-PHA used in the blending were determined by gel permeation chromatography (GPC). GPC analysis was performed using a Waters™ 600-GPC (USA) instrument equipped with a Waters Styragel HR (HR1, HR2, HR5E and HR5E) columns (7.8 mm internal diameter x 300 mm) (USA) connected in series and a Waters 2414 refractive index detector. Approximately 100 μΐ of a 2 mg/ml polymer sample was eluted by tetrahydrofuran at a flow rate of 1 ml min ^"1 at 40 °C. The instrument was calibrated using monodisperse polystyrene standards.

Differential Scanning Calorimetry (DSC)

DSC analysis for the mcl-PHA samples was carried out using Mettler Toledo DSC 822e. The experiments were programmed at a heating rate of 20 °C min ^"1 in the temperature range of -100 to 180 °C under a nitrogen gas flow. Cryospeed nitrogen was used to achieve the sub-ambient temperature. Approximately 5.0 mg of PHA sample was used and encapsulated in the aluminium pan. T _g of the sample was determined as the onset of a steep change in energy.

The T _g for PVC and the PVC/PHA blends were measured using Perkin Elmer Pyris DSC 6 thermal analyzer (USA) at a programmed heating rate of 20 °C min ^'1 . The experiments were carried out in the temperature range of 35 to 130 °C under dry nitrogen atmosphere at a flow rate of 20 ml min ^"1 . For PVC, approximately 5.0 mg in a compact powder form was loaded in the aluminium pan while for the PVC/PHA blends, 5.0 mg of the films were cut into small pieces and placed in the pans. The samples were scanned twice with the first scan heated from 35 to 120 °C to remove the thermal history of the sample, then cooled to 35 °C and scanned for the second time up to 130 °C. The T _g of the sample was determined as the onset of a steep change in enthalpy for the second scan.

Theoretical calculation of T _g using Gordon-Taylor equation

The theoretical value of 2" _g for the polymer blends can be calculated from the Gordon- Taylor equation whereby the ^-fitting parameter was determined by solving simultaneous equations using the Polymath® software as well as experimental T _g substitution approach. The Gordon-Taylor equation is shown in Eq (1).

(WpHA T _g + kWpvcTg )

Tg = ^ (W _PHA + k Wpvc) _{(1 )} where T _g is the glass transition temperature of the polymer blend; T _g PHA and T _g PVC is the glass transition temperature of the respective polymer; W is the weight fraction of the individual component; k is the model specific parameter.

Thermogravimetric analysis (TGA)

The thermogravimetric analysis of PVC/PHA blend films were measured with a TGA 6 (Perkin Elmer, USA). Each sample was heated at a heating rate of 30 K min ^'1 with the scanning temperature ranging from 50 to 900 °C under an atmospheric nitrogen flow at the flow rate of 20 ml min ^"1 to check for the presence of trapped solvent in the sample. The thermal profile of the polymer blends was then characterized using TGA by scanning the samples in the similar temperature range but at a slower heating rate of 10 K min ^"1 under similar flow rate of nitrogen gas. About 10.0 mg of sample was loaded in the ceramic pan and the thermal data were recorded on Perkin-Elmer Pyris 1 TGA software.

Scanning Electron Microscopy (SEM)

Unplasticized and plasticized PVC samples films were examined by SEM to study the surface morphology of the thin films. SEM microscopy was performed using a SEM Zeiss Auriga (Germany) at operating voltage of 1 kV, under magnification of 500 X.

Fourier Transform Infrared Spectroscopy (FTIR)

FTIPv analysis of PVC, PHA and PHA-plasticized PVC samples was conducted using a Perkin-Elmer FTIR-ATR Spectrometer (USA). The IR spectra of the thin films prepared were scanned at a wavelength of 4000 to 450 cm ^"1 , with a resolution of 4 cm ^{" 1} and recorded after 4 scans.

Proton Nuclear Magnetic Resonance Spectroscopy (1H-NMR)

1H-NMR analysis of PVC, PHA and PHA-plasticized PVC samples was carried out on a JEOL JNM-LA 400 FT-NMR spectrometer (Japan) operating at 400 MHz. About 20.0 mg of the sample was dissolved in 1 mL of deuterated chloroform. The integration value of a-methine proton (-CHC1-) of PVC was chosen as the reference and was assigned the value of 1.00.

Dynamic mechanical analysis (DMA)

In this study, mechanical properties of plasticized PVC e.g. storage modulus (E '), loss modulus (£"), loss angle tangent (tan δ) and stiffness were characterized by TA DMA Q800 dynamic mechanical analyzer using a tension film clamp. Before subjected to the mechanical testing, sample films were prepared using a hot press (Carver Instrument, Model C, S/N 40000-715). Specimens were heated pressed to a specific temperature at 4.5 psi applied load and held for 2 min, followed by cooling to ambient temperature. Strips of thin films with 30.0 mm fixed length were then mounted to the TA DMA Instrument and the measurements were made under the temperature scan mode ranging from -40 to 120 °C, under a heating rate of 5 °C min ^"1 and at a frequency of 1 Hz. Liquid nitrogen was used in the Cryospeed, the cooling accessory, to achieve sub-ambient temperature in this testing. Elastic modulus (E) of plasticized PVC was also determined by adapting the elastic modulus equation from the model equation in TA DMA Q800 Equation Guideline. The relationship of the stiffness, elastic modulus and sample's geometry for the sample analyzed on a film tension clamp was shown in Eq (2).

_{K =} ^L

O Eq (2) where K is stiffness (N m ^'1 ); E is elastic modulus (G N m ^'2 ); A is sample cross- sectional area (cm ) and L is sample length (cm). As the sample has a very small area as compared to its length, no end effects correction is needed, therefore the modulus equation is derived as shown in Eq (3).

L

^{E " K,} A Eq (3) where E is elastic modulus (G N m ^"2 ); A is sample cross-sectional area (cm ² ); L is sample length (cm); K _s is measured stiffness (N m ^"1 )

Results and Discussion

Monomer compositions of the polymeric and oligomeric PHASPKO and PHAOA Figure 1 (a) and (b) show the molecular structure of the monomer units for PHASPKO and PHAOA respectively, as analysed from the GC and Ή-NMR spectra. Table 1 Monomer composition of the polymeric and oligomeric PHASP O and PHAQA

'ID: Identity; Ce^: 3-hydroxyhexenoic acid; Cs: 3 -hydroxy octanoic acid;

Cjo: 3-hydroxydecanoic acid; Q ₂ : 3-hydroxydodecanoic acid;

Ci2 _: i". 3-hydroxydodecenoic acid; Cn^ 3-hydroxydodecadienoic acid;

C14: 3-hydroxytetradecanoic acid; Ci _4: i:3-hydroxytetradecenoic acid; and

Ci ₄ :2'. 3-hydroxytetradecadienoic acid Table 1 shows the relative monomer compositions of the polymeric and oligomeric PHASPKO and PHAOA which were used in the PVC blending. The oligomeric PHA contained higher amount of shorter side chain monomers (C ₆ and C ₈ ), compared to the polymeric PHA. For example, the amount of C ₆ and C ₈ monomers for degPHAsp _O was 52.1 wt %, which was higher than the amount present in polymeric PHASPKO (50.8 wt %). The amount of C ₆ and C ₈ monomers in polymeric PHAOA was 43.7 wt % and it increased to 47.4 wt % in degPHAo _A after the heat treatment of PHAOA at 170 °C.

Overall PHAOA contained higher unsaturated monomers compared to PHASPKO- The polymeric and oligomeric PHAOA contained 17.4 wt % (Ci _2; i, Ci _2:2 , Ci _4: i and Ci4 _:2 ) and 7.5 wt % (C _6: i, C _12: i and Ci _4: i) unsaturated monomer contents respectively. In the PHASPKO, the proportion of unsaturated monomers was much lower with only 1.6 wt % for polymeric PHASPKO and 1.2 wt % for oligomeric PHASPKO- Determination of T _g of PVC/PHA polymer blends by DSC analysis

Differential scanning calorimetry (DSC) is designed to determine the change of enthalpy for a material as heat is absorbed or released when it undergoes a physical transformation (Sin et. al , 1998). It analyzes the heating effect of polymer during the physical changes in terms of glass transition temperature (T _g ) by directly measuring the difference of the amount of heat supplied to the sample and the reference. T _g is indicative of the phase at which the polymer loses its rigid glass properties and begins to behave as a flexible polymer. The T _g values of PVC, PHA and PVC/PHA blends obtained from the DSC measurements are listed in Table 2 and Table 3.

Table 2 Number-average molecular weight (M„), weight-average molecular weight (M _w ), polydispersity index (PDI, defined by M M _n ) and glass transition temperature (Tg) of PVC, polymeric and oligomeric PHA

Polymer Commercial M _n M _w PDI T _g (°C) code/Preparation

PVC Viscosity no. 87 36700 96000 2.6 79

(BDH laboratory

reagent)

PHAOA Batch-fermentation 22800 50700 2.2 -44 degPHAoA Thermal degradation 18400 75700 4.1 -47

PHASPKO Batch-fermentation 32700 60000 1.8 -44 degPHAsPKo Thermal degradation 18200 42000 2.3 -48

Table 3 T _g of PVC/PHA blends determined from DSC analysis and Gordon-Taylor equation via data substitution and simultaneous equation (SE) solution

T _s exp: experimental T _g from DSC measurement; T _{g ca} ] _C : calculated T _g from Gordon- Taylor equation

From Table 2, T _g of PVC was 79°C. The corresponding values of polymeric and oligomeric PHAsp _K owere -44 and -48°C; polymeric and oligomeric PHAOA were -44 and -47 °C, respectively. All the PVC/PHA blends (Table 3) showed a T _g lower than that of PVC but higher than that for PHA, i.e. the T _g of the blends was intermediate to those of the component polymers (PVC and PHA), indicating good miscibility and compatibility within the system. The molecular basis of miscibility could be attributed to the polar and hydrogen bonding interactions between PHA and PVC.

Several factors are known to affect the T _g of a polymer blend. The most important factor is chain flexibility of the polymer. T _g will be lowered if flexibility is built into the polymer, for example, by a lubricant effect. A second factor in determining T _g value is the molecular polarity of the polymer. Increasing the polarity of a polymer increases its T _g . Some correlations fail to correctly predict T _g of plasticizer-polymer mixture because they neglect specific PVC-plasticizer interactions.

In the present invention, the T _g values for the polymer blends were reduced when the proportion of PHA increased. This means that the plasticization of PVC by higher amounts of PHA reduced the T _g of the polymer blends more effectively. It is believed that a higher PHA content imparted better plasticization to the PVC due to more PHA embedding themselves in between the PVC chains, thus spacing them further apart to increase the free volume and polymer chain mobility. This in turn lowered the T _g of the polymer blend significantly.

PVC plasticized with oligomeric PHA had lower T _g than PVC plasticized with polymeric PHA. It is suggested that plasticization of PVC by oligomeric PHA more greatly enhanced the segmental mobility of the blends compared to polymeric PHA. This in turn modified the T _g and material properties of the PVC/degPHA blends to a greater extent. This is because shorter plasticizer fragments could greatly increase the free volume in the polymer blend compared to longer, less mobile chains. Therefore, the presence of oligomeric PHA as plasticizer would contribute to better mobility and lower T _g for the PVC/degPHA blends.

Besides that, polymeric PHA has longer polymer chains than the oligomeric PHA. Thermal degradation of PHAOA and PHASPKO had led to higher number of shorter chains and higher number of terminal -OH and -COOH groups. This means that the polymeric PHA could have higher amount of functional carbonyl groups to interact with the a-hydrogen of PVC, and provide stronger chain entanglements with PVC. The higher amount of interacting PHA segments with the PVC would lead to a decrease of segmental flexibility of the polymer chains. Oligomeric PHA has lower molecular weight and more end groups. Although it has higher amounts of terminal COOH and OH groups which could contribute to the dipole-induced dipole interactions with neighboring PVC molecules, it has lesser entanglements with PVC.

The reduction of T _g of PVC by PHAOA was less compared to PHASPKO, indicating a lower extent of mobility of the molecular chain segments in the PVC plasticized with PHAOA- It was suggested that branching of the plasticizer tends to hinder the movement of the plasticizer within the polymer matrix (Marcilla et. al. , 2004). PHAOA consists of higher amount of bulky alkyl side chains (C12 and C ₁₄ ) compared to PHASP O and this may decrease the molecular flexibility in the PVC/PHAOA blend because the PHAQA chains could not slide past each other as easily as PHA _S PKO chains.

PHAOA also contains more unsaturated long side chains compared to PHASPKO- The high electron density in the double bonds of unsaturated pendant groups would be attracted to the electropositive carbon atom in C-Cl of PVC, leading to strong interactions with the PVC segments and this could decrease the segmental mobility within the PVC/PHA _0A blend. Thus, the T _s of the PVC/PHA _0A blend would be higher than the T _g of the PVC/PHA _SP KO blend.

Correlation of polymer-plasticizer interaction with T _g derived from Gordon- Taylor equation

Generally, the compositional dependence T _g of a compatible polymer blend lies between the T _g of the constituents and it can be expressed by Gordon-Taylor equation (Eq. (1)). According to An et. al. (1997), Gordon-Taylor equation is applicable for the determination of the T _g of blends when specific interactions within the mixture are not very strong.

DSC measurements yielded experimental T _g and the values were compared with the T _g determined from the Gordon-Taylor equation. The calculations of T _g of PVC/PHA blends using Gordon-Taylor equation via data substitution and simultaneous equation solution are shown in Table 3. It should be pointed out here that the constant k in the Gordon-Taylor equation is the model fitting parameter which includes all the possible interactions within the polymer mixture. These interactions were actually difficult to be determined precisely by conventional empirical and mechanistic approach.

Table 3 shows that the experimental T _s data for all the polymer blends is in excellent agreement with those obtained from the Gordon-Taylor equation. The absolute values of IS.T _g (lA gl) for all the blends are about 1°C and this shows that the difference between the experimental and calculated T _g values are insignificant. These results were in satisfactory agreement with the Gordon-Taylor fitting approach, where the differences between the respective T _g values should lie within experimental error < 2 °C (Penzel et. al., 1997).

The differences of the two estimates of ^-variable were also quite small with variations ranged from 0.04 to 0.1 1. This showed that there was insignificant difference between the T _g values obtained using the two calculation methods (simultaneous equations solution and substitution method) as the ^-specific parameters were not likely to deviate greatly. Study of PVC-PHA interactions by TGA

In the present invention, thermogravimetric analysis (TGA) was used to study the thermal behaviour of PVC and a series of PVC/PHA blends. The derivative thermogravimetry (DTG) which is defined as the first derivative of the weight change of sample as a function of temperature was used to analyze overlapping decompositions where different components of the polymer blends could be separated and their respective thermal stability determined. All the TGA data for the thermal decomposition of PVC and PVC/PHA blends were summarized in Tables 4.

Table 4 Thermogravimetric data of PVC blends and blend components

^ Tonset. Temperature at onset of decomposition; ² T _P : Temperature at fastest decomposition According to Table 4, apparent two distinct stages of degradation were exhibited in the decomposition of PVC. The first decomposition started from 216 °C to 367 °C with a peak decomposition temperature at 278 °C. This stage of degradation was ascribed to mainly the dehydrochlorination process, leaving behind the unsaturated hydrocarbon structures. The second decomposition started from 367 °C to 530 °C with a maximum rate at 449 °C, which presumably corresponded to the degradation of the resulting unsaturated hydrocarbons in the dehydrochlorinated PVC. There was a remaining 7.7 % of residual carbon black at the end of the TGA heating program since the heating was carried out under nitrogen atmosphere.

Similarly, the thermal decomposition of all the PVC/PHA blends occurred through two-stage degradation as PVC whereby at the first stage of degradation, decomposition of PHA and dehydrochlorination simultaneously occurred. The weight loss during the first stage of decomposition for the PVC/PHA blends was ascribed to the decomposition of PHA and evolution of chlorinated fragments comprising mainly HC1, as shown by the higher weight loss due to the added PHA in the PVC/PHA compared to the unplasticized PVC. There was no significant change in weight loss at the second stage of decomposition as this stage was mainly ascribed to the decomposition of fraction of PVC resin with no plasticizer, since any PHA would have completely degraded at temperature above 400 °C. There was a remaining carbon black residues at the end of the degradation since the heating was carried out under nitrogen atmosphere.

The temperature scale of the TGA instrument is calibrated by Curie-Points of certain metals and alloys and the accuracy is in the order of ± 4 °C. As shown in the table, there was no significant difference in the T _onset between the unplasticized PVC and those plasticized with PHA during the first stage of degradation, presumably the amounts of plasticizer at 2.5 and 5 phr were insufficient to produce any significant change to the onset of decomposition for PVC. However, the decomposition temperature range for the first stage of degradation showed a noticeable difference, whereby the plasticized samples were thermally degraded over a broader range, starting at a lower temperature. This effect could be due to the molecular interactions between the PVC and PHA plasticizer where the presence of PHA fractions might influence the degradation of the PVC. Thus, the plasticized samples would decompose earlier as compared to the unplasticized PVC.

Qualitative comparisons of plasticized PVC film morphology by SEM

SEM is used to examine the surface variations of plasticized PVC and could provide qualitative comparisons with the PVC morphology. In order to understand how the surface morphology of the PVC film changes with the introduction of plasticizers, the SEM micrographs of the pure PVC and PHA-plasticized PVC films were taken.

As shown in Figure 2, cavities were present in the individual PVC film whereby voids constitute the PVC matrix. The pores were distributed throughout the surface with the pore size in the range of 1 to 20 μηι. These observations were similar to the findings reported by Stephan et al . (2000).

As shown in the SEM micrographs of plasticized PVC (Figure 3 and Figure 4), after mixing the PVC with PHA, the cavities were not as clearly observed as in pure PVC. The PHA penetrated to some of the porous structures of PVC and interfused with the PVC polymer segments. The dispersion of the PHA into the PVC matrix presumably increased the distance between PVC chains, by placing themselves in between the PVC polymers and separating the PVC chains further apart, therefore promoted higher degree of freedom of polymer conformation. The effectiveness in the dispersion of plasticizers in PVC matrix could be attributed to the molecular weight of the PHA and polar interactions between PVC and PHA phases. Low molecular weight PHA would have greater diffusion into the PVC matrix compared to high molecular weight PHA, leading to greater flexibility and polymer chain movements.

FTIR analysis of PVC/PHA system

In the present invention, FTIR spectroscopy was used to investigate whether specific interaction between the PHA and PVC had taken place, which could be observed from the shift of certain peaks in the spectrum. Figure 5 shows the FTIR absorption spectra of PVC, PHA, PVC/PHA blends. All the blends showed the characteristic peaks of both PHA and PVC components, i.e. the C=0 stretching band at around 1737 to 1740 cm ^"1 and C-Cl stretching around 607 to 610 cm ^'1 , indicating that both polar functional groups of mcl-PHA and PVC were present in the polymer blends.

In miscible blends, a shift of the position of the carbonyl absorption in the FTIR spectra indicates specific interactions between the polymers. For example, for PHASPKO, the ester carbonyl stretching frequency was observed at 1726 cm ^"1 , as shown in Figure 5. The peak maximum position was shifted to higher frequency after the PVC was mixed with PHASPKO at different compositions, e.g. 1737 cm ^"1 for PSP ₅ and 1741 cm ^"1 for PSP2.5. On the other hand, the C=0 stretching frequency for PHAOA was observed at 1735 cm ^"1 . However shift of C=0 stretching band was observed in POA ₂ .5 (1739 cm ^'1 ) and POA ₅ (1740 cm ^'1 ) blends. On the other hand, the shifts of the C-Cl stretching frequency from 616 cm ^"1 (PVC) to lower frequency were also observed in the blends, with PSP at 607 to 608 cm ^"1 ; PdeSP at 609 to 610cm ^"1 ; POA at 608 cm ^'1 ; and PdeOA at 609 cm ^"1 . Therefore it is believed that specific polar interactions between the PHA and PVC had taken place. Figure 6 shows the FTIR absorption spectra in the C-O-C and CH-C1 stretching region of plasticized PVC. The CH-C1 deformation of PVC was assigned at 1328 cm ^'1 , whereas the C-O-C stretching vibration band for respective PHA was assigned at 1161 to 1 164 cm ^"1 . As shown in Figure 6, the C-O-C stretching vibration of PHA and CH-C1 deformation of PVC for all the polymer blends were shifted. For example in Figure 6(b), the C-O- C stretching frequency for low molecular weight PHASPKO (degPHAspKo) was observed at 1 162 cm ^"1 . After mixing the PVC with degPHAspKo, the peak maximum position was shifted to 1167 cm ^'1 for both PdeSP ₅ and PdeSP _{2 5} . Similarly, the CH-C1 stretching frequency for degPHAsp _K o was observed at 1328 cm ^'1 . After mixing the PVC with 2.5 and 5 phr of degPHAsp _K o, the peak maximum position was shifted to 1318 cm ^'1 for PdeSP ₅ and 1320 cm ^'1 for PdeSP _{2 5} blends. From the observations for the shift of C-O-C and CH-Cl stretching in all polymer blends, it is believed that the polar C=0 group in PHA and CI group in PVC could be responsible for the polymer miscibility, due to polar interactions in the system. These showed the existence of specific interactions such as dipole-dipole and polar interactions between the two polymers.

The relative ratio of absorbance band for reactive C-Cl stretching to the non-reactive CH bending (A ₆ 09/Ai ₄₂₆ ) in PVC was 1.94. However, the ratio of A ₆₀ 9/Ai ₄₂₆ was increased in all the PVC/PHA blends, for example, with POA _{2 5} having the ratio of 2.07, POAs 2.29, PSP ₂ .s 2.09 and PSP ₅ 2.42. The increase in the ratio of A ₆ O ₉ /AM ₂₆ indicated that the C-Cl group in the PVC has some interactions with the PHA where the intensity of the absorbance value for C-Cl stretching had increased. These could be attributed to the presence of specific interactions between the polar groups in PHA and PVC.

Table 5 showed the relative intensity ratio of the absorbance value at C=0 stretching present in mcl-PHA to the absorbance value of CH bending in PVC.

Table 5 Relative intensity ratio between absorbance value for C=0 stretching in PHA and CH bending in PVC

Ai ₇ 39/Ai ₄₂₆ : Absorbance intensity ratio of reactive C=0 group of PHA to non- reactive CH ₂ group of PVC

PVC plasticized with 5 phr PHA had higher relative ratio of Ai ₇ 3 ₉ /A ₁₄ 26 than with 2.5 phr PHA. As higher amount of PHA present in the polymer mixture, higher amount of polar groups in the polymer are available for possible interaction with PVC. PVC plasticized with SPKO-derived PHA had higher relative ratio of A ₁₇₃ 9/Ai ₄ 26 than with OA-derived PHA. SPKO-derived PHA had higher molecular weight (32700 g mol ^" ') and possessed a longer polymer chain compared to OA-derived PHA (22800 g mol ^"1 ). Thus SPKO-derived PHA was likely to have more interaction with PVC.

It should be noted that polar groups in a plasticizer are essential for good compatibility as it is the case of like dissolving like. When plasticizer molecules are introduced into the polymer mass, polymer chains are separated by the plasticizer molecules, which are able to line up their dipoles with the polymer dipoles. Polymer chains separated in this way are more easily moved relative to the one that are bonded very closely. Besides that it should be pointed out that branching of aliphatic chain and high molecular weight of a plasticizer reduces its ability to shield polymer dipoles, this subsequently reducing the mobility among the polymer chain (Marcilla and Beltran, 2004).

^-NMR analysis of PVC/PHA system

NMR spectroscopy is one of the techniques which could provide information on a molecular dimension scale (Havens & Koenig, 1983). Figure 7 showed the proton NMR spectra for PVC, PHA _0A and PVC PHA _0A blend, respectively.

In Figure 7(a), the peaks around 4.3 to 4.6 ppm were assigned to the a-methine proton (-CHC1-) which attached to the electropositive carbon atom, and peaks around 1.9 to 2.3 ppm was assigned to the β-methylene proton (-CH ₂ -) in PVC. The relative intensity ratio of ^a H (a-methine proton) to ^P H (β-methylene proton) was 1 :2, in agreement to the structure of the repeating unit. The peak at 1.5 ppm was due to the moisture in the D-chloroform. This could be due to the relatively low solubility of PVC in the chloroform and therefore small amount of water in the solvent could be detected in the spectrum. Figure 7(b) showed the Ή-NMR spectrum of PHAOA- The peak a at 0.8 ppm and peak b at 1.2 ppm were assigned to the methyl (-CH ₃ ) and methylene (-(CH ₂ ) _n -) group in the PHA side chain, respectively. Peak c at around 1.5 ppm was assigned to the methylene (-CH ₂ -) group attached to the carbon adjacent to the oxygen atom. These three peaks: a, b and c are the characteristic peaks of PHA, which could be used to validate the presence of polyester in the polymer blends. The peak d at around 2.5 ppm represented the methylene group at the a-position of the ester.

As could be seen from Figure 7(c) and (d), the spectra of POA _{2 5} and POA ₅ blend showed almost identical peaks as PVC, with three additional peaks being detected: 0.8 ppm, 1.2 ppm and 1.5 ppm which assignable to -CH ₃ , -(CH ₂ ) _n - and -CH ₂ - groups in PHA, respectively. This showed that both PVC and PHA were present in the blends. A small peak at around 2.5 ppm, as indicated by the arrows, was assignable to the a- hydrogen adjacent to the ester group, and this showed that polar ester group of PHA was present in the polymer blends. On the other hand, the relative intensity ratio of ^a H/ ^P H in POA _{2 5} and POA ₅ was reduced to 1.77 and 1.69 respectively, compared to PVC.

The Ή-NMR spectra for the other polymer blends showed similar spectrum as POA ₂ . ₅ and POA ₅ and the relative intensity ratio of ^a H to ^P H in the polymer blends were summarized in Table 6. Table 6 Relative intensity ratio between ^a H (a-methine proton) to ¾ (β-methylene proton) in polymer blends

From Table 6, the ratio of ^α Η/ ^β Η in polymer blends varied with the compositions and types of PHA present in the polymer blends. All the blends showed a reduced ratio of ^α Η/ ^β Η, compared to the PVC, indicating that the a-methine proton or/and β-methylene proton in the PVC could be interacted with the PHA, giving rise to the specific intermolecular interactions within the polymer mixture. These inter-polymer interactions could be probably attributed to the interactions of a-hydrogen as well as the local dipole-dipole interaction between chlorines of PVC with the PHA, in which the two polymers may intermingle with each other on a molecular level.

Hydrogen bonding-type interactions have been proposed as the key to achieving miscibility in many of the blends cited in this treatise. PVC which is a hydrogen-bond donor exhibits miscibility with many polymers containing H ⁺ acceptor units. The chlorine atoms of the PVC appear to render the polymer capable of interaction with polyesters, possibly by enabling hydrogen bonding to occur with the carbonyl groups of the polyester.

Dynamic mechanical analysis of PVC/PHA system

Loss Modulus (£")

A miscible system is formed when there are specific polymer-polymer interactions in a mixture of two polymers. These miscible blends are expected to show a single T _g value and a single modulus transition zone, which varies regularly with the blend composition (Nielsen & Landel, 1994). In this study, T _g was determined from the maximum peak of loss modulus (E ") curve.

For all PVC and PVC/PHA systems studied, the values of the T _g were obtained from the plots of loss modulus versus temperature and were evaluated from 40 to 140 °C for PVC; PHA _SPK o from -60 to 30 °C and PVC/PHA from 40 to 120°C. The loss modulus curve of PHASPKO showed a peak at -36.8 °C which corresponded to the T _g of PHA. PVC showed E" maximum at 91.9 °C, as shown in the loss modulus versus temperature curve (Figure 8). Table 7 summarized the T _g s of the plasticized PVC obtained from loss modulus peak versus temperature. Table 7 T _g of PVC/PHA measured from loss modulus peak maxima in DMA

The dynamic mechanical measurements showed a single T _g for all plasticized PVC, indicating that the mcl-PHA were highly miscible with PVC. Overall the T _g of all plasticized PVC were lower than the PVC, with T _g of PVC/PHA ₅ lower than PVC/PHA _{2 5} ; T _g of PVC/PHA _SP KO lower than PVC/PHA _0A and T _g of PVC/degPHA lower than PVC/PHA. The loss modulus curves of PVC, PVC PHA _{2 5} and PVC/PHA ₅ which consisted of low and high molecular weight of PHA as plasticizers were compared in Figure 10.

Figure 8 clearly shows that the T _g was shifted to lower temperature when PVC was mixed with PHA. A higher content of mcl-PHA in PVC/PHA led to a lower T _g value. This means that the plasticization of PVC was enhanced by higher amounts of mcl- PHA. This could be due to more PHA embedding themselves between the PVC chains, thus spacing the latter further apart to increase the polymer chain mobility.

Besides that, the loss modulus value of pure PVC as seen in Figure 10 has been reduced with the increase in the PHA content. The loss modulus (E") is related to the energy dissipated as heat upon deformation. Low loss modulus indicates low damping properties and hence elastic behavior. Therefore by increasing the PHA content, the blended material would have a more elastic behaviour. This agrees with Ahmad et al. (2007) which showed a positive correlation between low value of loss modulus and elastic polymeric behaviour. Storage modulus (Ε')

Storage modulus (E ') describes the ability of a polymer to absorb or store energy. This parameter provides an indication of rigidity of the polymer and its ability to resist deformation under an applied dynamic stress. High storage modulus indicates rigid material (Sin, 1998). The decrease in E' indicates a correlation between film stiffness and the temperature at which the films become rubbery. In this study, the storage moduli of the blends were compared with the pure PVC to investigate the effect of mcl-PHA on the rigidity of the polymer blends. The overall variation of storage modulus with temperature for PVC, PVC/PHA2. and PVC/PHA ₅ which consisted of low and high molecular weight PHA as plasticizers are compared in Figure 9 .

From Figure 9, the order of storage modulus for all PVC/PHA decreased in the following sequence: PVC > PVC/PHA _{2 5} > PVC/PHA _S . These observations indicated that the rigidity of the polymer blends is affected by the composition and amount fraction of the PHA plasticizer in the polymer mixture.

The modulus values of the all PVC/PHA decreases with increasing temperature. This behavior may be due to the softening effect of the PVC/PHA matrix at high temperatures which has higher polymer chain mobility (Lawrence et al., 2004) and the modulus eventually drops to zero when the polymer melts.

Elastic Modulus (£)

Elastic modulus (E) is the mathematical description of a polymer's tendency to be deformed elastically when a force is applied to it. It is a measure of the stiffness of a component. A stiff component, with a high elastic modulus, will show much smaller changes in dimensions. In general, engineering applications view stiffness as a function of both the elastic modulus and the geometry of a component. For rigid PVC, typical elastic modulus lies between 2.4 to 4.1 GPa. In this study, the calculated elastic modulus for the pure PVC was around 3.92 GPa. Subsequent elastic modulus values for the plasticized PVC were summarized in Table 8.

Table 8 Elastic modulus (£) values for PVC/PHA

As shown from Table 8, it could be seen that PVC plasticized with mcl-PHA showed a considerable lower elastic modulus than pure PVC. Overall, the effectiveness of reducing the elastic modulus of the polymer was found to be better in PVC/PHA ₅ as compared to PVC/PHA _{2 5} ; and better in PVC/PHA _S PKO as compared to PVC/PHA ₀ A; and better in PVC plasticized with low molecular weight PHA than high molecular weight PHA.

Stiffness

The extent of decrease in stiffness and changes in the softness of the plasticized PVC depend on both the level of plasticization and the nature of the plasticizer

(Hernandez et. al., 2000). As discussed earlier, introduction of the plasticizer into the polymer system greatly increased the mobility among the polymer chain, and this subsequently augmented the softening of the polymer. Figure 12 revealed the temperature variation of film's stiffness for all the plasticized PVC.

As shown in Figure 10 , the stiffness of PVC/PHA was decreased when the proportion of PHA was increased. According to Wypych (2004), when larger quantities of plasticizers were added into the PVC, more amorphous areas of the PVC were swollen. This would lead to increased ease of movement of the macromolecules, thus making the plasticized PVC to be more flexible. This could be seen from the decreased stiffness of the plasticized PVC when the amount of PHA was increased in the blend.

On the other hand, by comparing the film's stiffness of the PVC/PHA with PVC/degPHA blends at 40°C, it could be seen that addition of low molecular weight PHA could provide greater flexibility to the PVC compared to high molecular weight PHA, by introducing greater internal lubrication effect. The effectiveness in the lubrication effect could be attributed to the widespread specific interactions between the shorter chain fragments of low molecular weight PHA with PVC, promoted by the increased hydroxyl and carboxyl end groups.

Conclusions

Mcl-PHA could serve as a potential plasticizer for PVC due to the good miscibility between the two polymers evidenced by a single T _g based on DSC and DMA analyses. The T _g of the blends decreased with increasing the amount of the PHA. Blends composed of PVC and oligomeric PHA as plasticizer showed lower T _g than the blends composed of polymeric PHA. Oleic acid-derived mcl-PHA either in polymeric or oligomeric form imparted lower plasticizing effect to the PVC compared to SPKO- derived mcl-PHA by reducing the T _g of the polymer blends less effectively. The experimental T _g values from DSC analysis were compared with theoretical T _g values predicted from the Gordon-Taylor equation. It was found that the experimental T _g agreed well with the values calculated from the equation.

SEM micrographs of PVC/PHA films showed that plasticization of PVC involved the penetration of PHA polymers into some of the porous structures of PVC, and interfused with PVC polymer segments. These PHA polymers possibly embedded themselves between PVC chains and separated the PVC chains further apart, therefore promoted higher polymer chain movements. FTIR analysis confirmed the presence of both polar functional groups of PHA and PVC in the PHA-plasticized PVC. The amount of polar C=0 groups varied with the composition and type of PHA present in the plasticized PVC. It is postulated that the PVC-PHA miscibility was possibly due to the specific interactions between the C-O-C and C=0 groups of PHA with the CH- CI group of PVC. Results from 1H-NMR spectroscopic analysis also showed that the inter-polymer attractions between the two polymers were probably attributed to the a- hydrogen as well as the local dipole-dipole interaction between chlorines of PVC with the PHA.

DMA measurements showed a single T _g for all plasticized PVC and a lower loss modulus peak compared to the PVC, indicating the PHA were miscible with PVC. Decreased T _g , loss modulus peak value, stiffness, storage modulus, elastic modulus were observed in the polymer blends with higher amounts of PHA. When larger quantities of PHA plasticizers were added to the PVC, more amorphous areas of the PVC particles would be swollen and this would lead to increased ease of movement of the PVC macromolecules. On the other hand, low molecular weight PHA would increase the degree of chain movement and segmental flexibility to the PVC chains in a greater extent and would therefore impart plasticization effect to PVC more effectively, compared to high molecular weight PHA.

Some references, which may include patents, patent application and various publication are cited and discussed in the description of the present invention. The citation and/or discussion of such references is provided merely to clarify the description of the present invention and is not an admission that any such reference is "prior art" to the invention described herein. All references cited and discussed in this specification are incorporated herein by reference in their entireties and to the same extent as if each reference was individually incorporated by reference. List of References

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