Use of thermal analysis in the optimization of polymeric diffusion barriers in controlled release delivery systems

Selinger, Elizabeth; Brine, C.J.

doi:10.1016/0040-6031(88)85248-1

Cited by 8 publications

(5 citation statements)

References 1 publication

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“…Figure 1 shows the DSC scan of an ethylcellulose ®lm with the Tg determined by the half-Cp method, where DCp is half the change of the complete transition. The values were 121Á3 and 123Á1 C, which are in agreement with those previously reported (Selinger & Brine 1988;Dressman et al 1995;Sakellariou & Rowe 1995). DSC of Surelease ®lms ( Figure 2) showed a discontinuity between 20 C and 60 C, that could be related to its softening point (35 C) determined previously by thermomechanical analysis (Iyer et al 1990).…”

Section: Determination Of Tgsupporting

confidence: 90%

“…It is the result of an increase in segmental motion in a material and is accompanied by an increase in heat capacity and possibly a relaxation endotherm (Coleman & Craig 1996). Furthermore, the Tg is affected by storage conditions (Aulton 1995), water content (Hancock & Zogra® 1994;Wang et al 1997) and the addition of plasticizers (Selinger & Brine 1988; Van der Voort Maarschalk et al 1998;Hogan 1995). Therefore, the Tg of polymers is a critical factor not only in the ®lm formation during coating (Okhamafe & York 1988Keshikawa & Nakagami 1994) but also in compaction (Van der Voort Maarschalk et al 1998) and drug release (Okhamafe & York 1989;Dressman et al 1995).…”

mentioning

confidence: 99%

“…Conventional DSC may not be sensitive enough to identify the Tg of less homogenous samples that may therefore require preconditioning. These dif®culties are exacerbated when plasticizers are added since they lead to a reduction and a broadening of the glass transition (Selinger & Brine 1988;Ford & Timmins 1989).…”

mentioning

confidence: 99%

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Use of Dynamic Differential Scanning Calorimetry in Identifying Glass Transition Temperatures of Ethylcellulose and Surelease Films

Velasco

Ford

Rajabi‐Siahboomi

1999

Pharmacy and Pharmacology Communications

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The thermal properties of ethylcellulose and Surelease films were evaluated by differential scanning calorimetry (DSC) and dynamic differential scanning calorimetry (DDSC). DDSC is a novel thermoanalytical technique that allows the identification of glass transitions when they are overlapped by other phenomena such as decomposition or dehydration. Films containing different amounts of plasticizer (triethyl citrate) were prepared from solutions of ethylcellulose in acetone. Additionally, films were prepared from Surelease dispersions at different coalescent temperatures. DSC was sensitive enough to identify the glass transitions in ethylcellulose films but not in Surelease films. DDSC, because it separates the heat flow into two components—loss and storage curves—allowed the identification of the glass transitions in the storage curve. The addition of different amounts of triethyl citrate to ethylcellulose films led to a reduction in the glass transition temperature (Tg). The Tg temperature in Surelease films decreased with an increase in the temperature of coalescence, probably because at higher temperatures the movement of the polymer strands was higher and enhanced the action of the plasticizers included in the Surelease film. For simple polymeric films containing ethylcellulose, Tg values were identified by DSC and DDSC was not required. However, for Surelease films, containing materials of different molecular weight, plasticizers and variable moisture content, DDSC was required.

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Section: Determination Of Tgsupporting

confidence: 90%

mentioning

confidence: 99%

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Use of Dynamic Differential Scanning Calorimetry in Identifying Glass Transition Temperatures of Ethylcellulose and Surelease Films

Velasco

Ford

Rajabi‐Siahboomi

1999

Pharmacy and Pharmacology Communications

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“…Apparently, more plasticizer was interposed between the polymer chains reducing the polymer-polymer interaction which was accompanied by the increase in intermolecular space (free volume). 3,7 In the opaque films the T g value reduced less significantly than in the transparent films, due to the presence of water (methodology preparation) that induced phase separation, i.e. less amount of PCL-T was interposed between the CA polymer chain.…”

Section: Thermal Analysismentioning

confidence: 99%

“…Over the last two decades, polymeric film coatings have been increasingly used to provide controlled and/or enteric release barriers for medications. [2][3][4] The mechanical and thermal properties and morphological aspects of a polymer film are important characteristics in a coating process. Frequently plasticizers are used to improve mechanical and thermal properties of a polymer and in general they could also change the permeation coefficient of a substance through a polymer film.…”

Section: Introductionmentioning

confidence: 99%

Poly(caprolactone triol) as plasticizer agent for cellulose acetate films: influence of the preparation procedure and plasticizer content on the physico‐chemical properties

Meier

Κanis

Lima

et al. 2004

Polymers for Advanced Techs

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The influence of the plasticizer content and film preparation procedure on the morphology, density, thermal and mechanical properties of cellulose acetate (CA) films plasticized with poly-(caprolactone triol) (PCL-T), were studied. Differential scanning calorimetry (DSC), thermal mechanical analysis (TMA), scanning electron microscopy (SEM), wide-angle X-ray diffraction (WAXD) and infrared spectroscopy (FT-IR) techniques were used. The films were prepared by dry-casting CA and CA/PCL-T in acetone or acetone/water solutions, which produced transparent and opaque films, respectively. In contrast to the transparent films, which were dense, the opaque films presented a porous morphology. However, the presence of PCL-T reduced the opaque film porosity, increasing, in consequence, its bulk density. The TMA results revealed that PCL-T reduced the glass transition temperature more significantly in the transparent than in opaque films. Only the transparent CA/PCL-T films presented a melting temperature, that reduced with higher concentrations of PCL-T, suggesting a higher ordering (crystallinity) when the films were prepared in the absence of water, as observed from WAXD curves. The mechanical properties also showed that the transparent films were more soft and tough than the opaque films. In summary, PCL-T was a good plasticizer agent for CA films due to the presence of hydrogen bonds between the components (FT-IR spectra). The presence of water in the dry casting process has a significant effect mainly on film morphology and mechanical properties.

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Thermal analysis of polymeric materials

Haines

1989

Thermochimica Acta

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Use of thermal analysis in the optimization of polymeric diffusion barriers in controlled release delivery systems

Cited by 8 publications

References 1 publication

Use of Dynamic Differential Scanning Calorimetry in Identifying Glass Transition Temperatures of Ethylcellulose and Surelease Films

Use of Dynamic Differential Scanning Calorimetry in Identifying Glass Transition Temperatures of Ethylcellulose and Surelease Films

Poly(caprolactone triol) as plasticizer agent for cellulose acetate films: influence of the preparation procedure and plasticizer content on the physico‐chemical properties

Thermal analysis of polymeric materials

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